Master Thesis/Internship

Topic Guide 2013-2014

Information.............................................................................................................................................................................................5

I.

CMOS Scaling (sub-22 nm) .................................................................................................... 6 Electrical evaluation and reliability assessment of local interconnects......................................................................... 6 Time-Dependent Dielectric Breakdown (TDDB) reliability of advanced CMOS gate dielectrics ........................ 6 Conductive Atomic Force Microscopy (C-AFM) for memory devices characterization ........................................ 7 Investigation and optimization of the electrical switching properties of scaled Ta2O5-based resistive RAM memory cells .................................................................................................................................................................... 7 Reliability measurement and modeling of advanced BEOL interconnect .................................................................... 9 Evaluation of MgO as tunnel barrier in material stacks for MRAM applications ....................................................... 9 Thermo-compression bonding of fine-pitch micro-bumps for 3D integration of ICs............................................ 10 Study of chipping mechanisms in the dicing of thin silicon wafers .............................................................................. 10 Evaluation of photoresist outgassing for Extreme Ultraviolet Lithography .............................................................. 11 Deposition, characterization and application of dielectric films .................................................................................. 11 Development, characterization and application of pore sealing treatments ............................................................ 12 Hot carrier reliability on advanced logic/DRAM devices............................................................................................... 13 Investigation of advanced self-rectifying resistive switching memory cells (SRC-RRAM) .....................................14 Self-assembled monolayers as enabling technology for microelectronics ................................................................. 14 Advanced barrier CMP slurry development ..................................................................................................................... 15 Development of a ramped voltage BTI procedure for fast gate dielectric testing.................................................. 16 Compact modeling of advanced transistors...................................................................................................................... 17 Modeling of temperature effects in advanced devices.................................................................................................... 17 Characterization and modeling of oxide border traps in Ge/III-V MOSFETs .......................................................... 18 Interface stability and reliability of high-mobility channel MOSFETs .......................................................................... 18 Carbon nanotube contacts: electrical characterization of CNT – damascene contacts ......................................19 Carbon nanotube growth and its catalyst nanoparticle deposition for future contact applications ..................20 Bottom-up fill of deep holes with nanowires for future contact schemes ............................................................... 21 Energy spectrum of a cylindrical superlattice nanowire ................................................................................................ 21 Modeling of tunable band gap bilayer structures and devices ...................................................................................... 22 Design of an reliability characterization package for future generation high-performance CMOS ransistors.................................................................................................................................................................................... 22 Design and simulation of on-chip circuits for parallel characterization of ultra-scaled transistors and SRAM cells for BTI reliability ................................................................................................................................................ 23 Graphene: device fabrication for optoelectronics........................................................................................................... 24

Master Thesis/Internship Topics 2013-2014

1

Graphene: device fabrication and characterization ......................................................................................................... 25 Plasma etching and characterization of novel materials for advanced patterning ................................................... 26 Low damage plasma processing: new materials for pore stuffing of 2.0 porous SiOCH materials ....................26 Depth loading study in STI .................................................................................................................................................... 27 Advanced materials characterization using ion beam scattering ................................................................................. 28 Development of an accelerator based metrology application...................................................................................... 29 Analysis of surface preparation for HV and UHV-SSRM ............................................................................................... 30 Active dopant characterization with micro-probes on advanced ultra-shallow high-mobility CMOS semiconductor structures...................................................................................................................................................... 30 Development of a professional data analysis package for the micro-four point probe (M4PP) ..........................31 Fundamentals of nanoscopic materials removal............................................................................................................... 32 Strain characterization in advanced transistor structures using Raman .................................................................... 33 Non-destructive assessment of electrical properties of nanoscale probe tips....................................................... 33 Nickel damascene process for MEMS................................................................................................................................. 34 Defectivity monitoring of directed self-assembly ............................................................................................................ 35 Modeling of leakage in very high permittivity dielectrics for DRAM applications................................................... 36

II.

Heterogeneous Integration .................................................................................................37 Calibration of stress sensors for 3D-IC applications...................................................................................................... 37

III. Electronics for Healthcare and Life Sciences....................................................................38 Studying the function of neural circuits.............................................................................................................................. 38 Measurement of nanomaterial exposure in air ................................................................................................................ 39 Sensors for weight management and energy expenditure ............................................................................................ 39 How to detect dehydration with body area networks?................................................................................................. 40 Ionic fluidic study of metallic nanopores............................................................................................................................ 41 Exploration of efficient electroporation protocols for intracellular recording of action potentials using configurations of microelectrodes on chip........................................................................................................................ 41 Characterization of optical waveguides for optogenetic stimulation of in vitro and in vivo neurons...................42 High-density carbon nanotube electrodes for recording and stimulating electrogenic cells ...............................42 Controlling light-matter interactions with plasmonic nanoantennas.......................................................................... 43 Engineering micro-structures for an optimized lens-free image .................................................................................. 44 Measuring electrical properties of cancer cells ................................................................................................................ 45 Gram staining using spectroscopy ....................................................................................................................................... 45 Gold nanostars for imaging and photothermal treatment of cancer .......................................................................... 46

Master Thesis/Internship Topics 2013-2014

2

Antibody stabilizers for lateral flow assays........................................................................................................................ 46 Multiplex ligation polymerase amplification on chip ....................................................................................................... 47 TNFα detection in cell-culture medium of activated cells ............................................................................................ 47 Detection of single protein molecules in microwells on a digital lab-on-a-chip for point-of-care diagnostics .................................................................................................................................................................................. 48 Quantitative protein kinetics analysis using a refractometric LSPR sensor with an improved figure of merit ............................................................................................................................................................................................ 48 High quality-factor resonators in silicon nitride waveguides ........................................................................................ 49 Noise characterization and modeling of electrodes for in vivo and in vitro neural recording............................50 Characterization of the light-sensitivity of CMOS-ICs for life science applications ............................................... 50 Multimodal integration of EEG and functional Near Infrared Spectroscopy for ambulatory brain imaging .....51

IV. Imaging Systems ....................................................................................................................53 Dynamic current steering in active pixel sensors............................................................................................................ 53

V.

Large Area Flexible Electronics ..........................................................................................54 Degradation mechanisms in organic solar cells................................................................................................................ 54 Organic photodetectors......................................................................................................................................................... 54 Contact resistance optimization in organic thin film transistors ................................................................................. 55 Bias stress stability study of a-IGZO TFTs........................................................................................................................ 56

VI. Wireless Communication ....................................................................................................57 Radio-frequency communication with metal-oxide electronics on plastic ............................................................... 57 Algorithm and architecture co-optimizations for cost and power constrained signal processing system .......58 Digital assistance and digital frontend for deep submicron analog circuits............................................................... 58 Functional error mitigation schemes for latency-constrained wireless systems ..................................................... 59

VII. Energy......................................................................................................................................60 Hydrogen generation through water photoelectrolysis using semiconductor photoanodes...............................60 Electrical characterisation of amorphous Si layers for solar cell applications .......................................................... 60 Dielectric ablation by laser processing for photovoltaic applications ........................................................................ 61 Development of assembly technology for next-generation c-Si PV modules .......................................................... 61

Master Thesis/Internship Topics 2013-2014

3

Optimization of the bonding and detachment process of epitaxial silicon foils for application in thin-film crystalline silicon solar cells................................................................................................................................................... 62 Development and validation of an optical model for PV modules .............................................................................. 63 Degradation mechanisms in organic solar cells................................................................................................................ 63 Large area coating of organic photovoltaic modules ...................................................................................................... 64 2D and 3D modeling of high efficiency back junction solar cells................................................................................. 65 Photonic nanostructures for light management in novel thin silicon solar cells and modules.............................65

VIII. Sensor Systems for Industrial Applications .....................................................................67 Opto-acoustic micro-resonator for sensing applications .............................................................................................. 67 MEMS-based compass: optimization of magnetometers enabled by MEMS resonators ........................................68 Cost-effective photonic sensor for point-of-care medical diagnostics ...................................................................... 69

IX. Microelectronics Design .......................................................................................................70 Visualisatie van DfX analyse feedback in een elektronisch ontwerp .......................................................................... 70 Design van een 3.3V digitale standaardcelbibliotheek in UMC 180 nm technologie voor ruimtetoepassingen.................................................................................................................................................................. 70 Ontwerp van radiatie-tolerante flipflopsvoor imec’s DARE bibliotheken ................................................................ 72 Design prediction tool development for solder joint reliability for printed board assemblies, including the flexibility of components/boards................................................................................................................................... 73

X.

NERF........................................................................................................................................74 Design and construction of automated environments to study spatial memory function in rodents ...............74 Closed-loop real-time read out and control of memory processing in behaving rats........................................... 74 Scale-space based segmentation and identification of cells in microscopic images................................................. 75 Optogenetic dissection of dopamine function for learning from reward and punishment...................................76 Using superparamagnetic nanoparticles as force actuators in cells and tissues....................................................... 76 Design, prototyping and testing of miniaturized brain implants .................................................................................. 77 Inferring population network dynamics from cellular imaging data in behaving animals .......................................78

Master Thesis/Internship Topics 2013-2014

4

Information Students from universities and engineering schools can apply for a master thesis and/or internship project at imec. Imec offers topics in engineering and (industrial) sciences in different fields of research. The internship and thesis projects currently available are collected in this topic guide and are classified according to the imec research domains. You can find more detailed information on each research domain under the heading ‘Research’ on www.imec.be. Should you require more information, you can send an e-mail to [email protected]. How to apply? Send an application e-mail with your motivation letter and detailed resume to the responsible scientist(s) mentioned at the bottom of the topic description of your preference. The scientist(s) will screen your application and let you know whether or not you are selected for a project at imec. It is not recommended to apply for more than three topics. For more information, go to the Internship and Master Thesis page under the heading Academy on our website.

Master Thesis/Internship Topics 2013-2014

5

I.

CMOS Scaling (sub-22 nm) Electrical evaluation and reliability assessment of local interconnects In future CMOS technologies the individual transistors will be connected through local interconnects in order to increase the device density and to reduce the metal one complexity. These local interconnects however have to fulfill the same strict reliability specification as the other chip components and a thorough understanding of the potential degradation mechanisms is needed. The main task of this thesis/internship is the electrical characterization of these local interconnects. This includes the evaluation of various newly designed test structures, the comparison of different local interconnect processes and the investigation of potential reliability issues. Type of project: Thesis or internship project (preferred duration is 6 months) Degree: Master in Industrial Sciences or Master in Science or Master in Engineering Responsible scientist: For further information or for application, please contact Thomas Kauerauf ([email protected]).

Time-Dependent Dielectric Breakdown (TDDB) reliability of advanced CMOS gate dielectrics CMOS scaling is not only concerned with the reduction of the channel length and channel width, but also the scaling of other transistor parameters such as the gate dielectric thickness. Recently high-k gate dielectric were introduced and the long-term reliability of these ultra-thin layers is of major concern. The time-dependent dielectric breakdown (TDDB) is one of the critical mechanisms, where the generation of individual defects in the dielectric leads to an increase in gate leakage current and eventually to device failure. Although there has been a lot of learning on TDDB in the recent years, there are still many open questions waiting to be answered. The main task of this thesis/internship is to study the effect of electrical stress at the gate on key transistor parameters. Since the degradation does not occur abrupt but gradually, testing and analyzing the shift of these parameters over time is required. A second aspect will be to evaluate whether these parameter shifts are actually critical to the device performance and if additional effects such as self-heating can be expected. Type of project: Thesis or internship project (preferred duration is 6 months) Degree: Master in Industrial Sciences or Master in Science or Master in Engineering Responsible scientist: For further information or for application, please contact Thomas Kauerauf ([email protected]).

Master Thesis/Internship Topics 2013-2014

6

Conductive Atomic characterization

Force

Microscopy

(C-AFM)

for

memory

devices

Conductive bridging resistive memory CBRAM, based on resistance switching mechanisms, is emerging as a potential replacement for Flash and/or DRAM applications, due to its high scalability potential, for future 20 nm technology nodes and beyond (fig. A). Conductive atomic force microscopy C-AFM (fig. B) is a scanning probe microscopy technique, relying on a normal atomic force microscope equipped with a current sensor capable to measure ultra low currents. C-AFM represents an invaluable tool in two ways. First it allows examining very small features with nm-scale spatial resolution (nanoscopic electrical probing), and secondly the tip can be used as a nano sized electrode. This internship/thesis fits into the characterization framework for OXRRAM/CBRAM using C-AFM. You will be trained in the use of the tool and you will intensively use it focusing on device characterization methodologies. During the period of the internship the student will focus particularly on material characterization and environmental conditions .The data analysis and interpretation will cover an important part of the work; you will apply statistical principles in data collection and will be asked to rule out your results. You will work in an international R&D team; a good command of English language is required. The detailed content of the work will be defined in detail at the moment of starting this project.

Type of project: Thesis or internship project of 6 months Degree: Master in Science or Master in Engineering majoring in physics, electrical engineering, material science, chemistry Responsible scientist: For further information or for application, please contact Umberto Celano ([email protected]).

Investigation and optimization of the electrical switching properties of scaled Ta2O5-based resistive RAM memory cells The Resistance RAM (RRAM) is a new class of memories emerging as serious candidate for future memory replacement. Resistance RAM cells typically consist of an insulator material sandwiched between two metal electrodes, and exhibiting resistive-switching properties, that is to say the application of an electrical current/voltage to the cell induces reversible changes of the cell resistance, which allows thus programming different memory states. For metal/oxide/metal RRAM devices, the switching to the low resistance state (LRS) is understood as the formation of oxygen-vacancy chain through the oxide while the return to the high resistance state (HRS) is due to partial recovery of these defects, the two operations being electrically induced.

Master Thesis/Internship Topics 2013-2014

7

Ta2O5 materials have recently drawn a lot of attention due to excellent set of RRAM memory properties demonstrated recently on scaled cells (see Fig.1). Not only controlled memory operation, low programming power, and good data retention were demonstrated, but also in particular longer write-programming endurance results were obtained on such material (Fig.1c) than on other switching oxides.

(a)

(b)

(c)

Fig1: examples of scaled Ta2O5-based RRAM cell (a), switching I-V traces (b), and excellent write endurance properties (c), as extracted from “M.-J. Lee et al., Nature Materials, vol.10, 2011, p165”

However, little is known yet with respect to the switching mechanisms and improvement potentials in Ta2O5based RRAM. We recently undertook the integration development of scaled Ta2O5 RRAM memory cells stacked on memory-select transistors. The purpose of the internship will be to study the effect of processing and cell-stack material combinations (including electrodes) on the electrical-switching properties. To this aim, the following methods will be used: • Standard I-V measurements • Constant voltage stress tests • Above methods at different temperatures • Pulse programming using sub-10ns wide electrical pulses • Possible C-V measurements • Possible modeling activity The study will be carried out within a project team consisting of experts in different fields (processing, integration, physical characterization, modeling ...), so that the understanding and modeling of the electrical results can be facilitated. The study will also be realized in close collaboration with industrial partners. The gained understanding of the switching will allow defining an optimum stack configuration satisfying the industrial specification for memory operation. Type of project: Internship project of minimum 5 months Degree: Master in Science or Master in Engineering majoring in material science, physics, electronics Responsible scientist: For further information or for application, please contact Ludovic Goux ([email protected]).

Master Thesis/Internship Topics 2013-2014

8

Reliability measurement and modeling of advanced BEOL interconnect Deep submicron interconnect scaling leads to severe issues with reliability of the wires in the BEOL (Back-end-ofline) process stage. Both electromigration and TDDB (Time-dependent dielectric breakdown) play a major role. deliver mode: 7 we want to measure the characteristics of deeply scaled interconnect schemes to evaluate the degradation mechanisms and to characterize them under different conditions. Moreover, based on these measurements we want to build a SPICE-level model which allows to model the effects in a parametric way for use in circuit level simulations of data-path or memory structures. Profile: strong interest in measurement setups and hardware, basics of electrical SPICE-level modeling, basics of reliability degradation. Type of project: Thesis of minimum 6 months (full-time, at Leuven) Degree: Master in Engineering majoring in micro- or nano-electronics Responsible scientist(s): For further information or for application, please contact Kristof Croes ([email protected]) and Francky Catthoor ([email protected]).

Evaluation of MgO as tunnel barrier in material stacks for MRAM applications Magnetic random access memory (MRAM) is a non-volatile memory having the information stored in the magnetization direction. In order to realize next generation of high density non-volatile memory a lower switching current density and high thermal stability are needed. A promising solution to achieve these requirements in MRAM relies on MgO based magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy. Crystalline MgO with (001) texture is needed to achieve perpendicular magnetic anisotropy in CoFeB/MgO/CoFeB based MTJs. Parameters that are believed to have an important impact on performance are: texture, interface, B-content of CoFeB, seed and capping layers or post-deposition anneals conditions. In this project basic understanding of the stacks is being built up. MgO will be deposited via MgO RF sputtering or Mg post-oxidation. A comparison with MgO ALD (atomic layer deposition) properties could be performed. The project will comprise beside stack deposition, extensive physical analysis such as XRD, AFM, TEM, SIMS, XPS and magnetic properties such as evaluation of magnetoresistance ratio and magnetization saturation. 1. 2. 3. 4.

S. Ikeda, K. Miura, H.Yamamoto, K. Mizunuma, H.D. Gan, M. Endo, S. Kanai, J. Hayakawa, F. Matsukura, and H. Ohno, Nature Materials, 2010, 9, 721. K. Yakushiji, K. Noma, T. Saruya, H. Kubota, A. Fukushima, T. Nagahama, S. Yuasa and K. Ando, Applied Physics Express, 2010, 3, 053003. D.C. Worledge, G. Hu, D.W. Abraham, J.Z.Sun, P.L. Trouillard, J. Nowak, S. Brown, M.C. Gaidis, E.J. O'Sullivan and R.P. Robertazzi, Applied Physics. Letters, 2011, 98, 022501. Y.S. Choi, K. Tsunekawa, Y. Nagamine, and D. Djayaprawira, Journal of Applied Physics, 2007, 101, 013907.

Type of project: Thesis and/or internship project of 3 up to 6 months Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in material science, physics, electronics, chemistry Responsible scientist: For further information or for application, please contact Mihaela Popovici ([email protected]).

Master Thesis/Internship Topics 2013-2014

9

Thermo-compression bonding of fine-pitch micro-bumps for 3D integration of ICs Three-dimensional integration of ICs is a major driving technology for future size shrinkage and performance improvement of electronic products. One of the key elements in 3D integration is to build reliable fine pitch interconnects between the vertically stacked ICs. At imec, we are working on thermo-compression bonding technology to make interconnection joints between the micro-bumps on the ICs. In this master thesis, you will work on both the theoretical and experimental aspects of thermo-compression bonding to deepen the understanding of this process and to further develop it towards finer pitch requirements. You will focus on the investigation of actual physical conditions and resulting micro-scale changes applied on the bonding interfaces between micro-bumps under different process conditions, and their influence on the final bonding quality. In the implementation of this work, you will be involved in model building, planning of experiments, processing, characterization, and finally the analysis of results. You will have access to cutting-edge tools with the guidance from experienced researchers and engineers. Type of project: Thesis project of 6 months Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in physics, applied mechanics, material science or relevant fields Responsible scientist: For further information or for application, please contact Teng Wang ([email protected]).

Study of chipping mechanisms in the dicing of thin silicon wafers Chipping of silicon wafers during their dicing is an important factor which limits the throughput and yield of the dicing process. Chipping also plays a significant role in determining the reliability of ICs. The recent development of 3D integrated ICs and ultra-thin packages have strongly driven the need of thinning silicon wafers to a thickness range of below 100 µm, which has made the In this thesis work, your focus will be on the understanding of chipping mechanisms on both front sides and back sides of thin silicon wafers. The target is to identify different chipping mechanisms under different dicing conditions and on wafers with different passivation layers through carefully designed experiments and microscopic inspection using both optical and scanning electron microscopes. You will be involved in design and execution of experiments, characterization, and analysis of experimental results. You will have access to cutting-edge processing and metrology tools, assisted by experienced researchers and engineers. Type of project: Thesis project of 6 months Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in physics, material science, mechanical engineering or relevant fields Responsible scientists: For further information or for application, please contact Teng Wang ([email protected]) and Kenneth Rebibis ([email protected]).

Master Thesis/Internship Topics 2013-2014

10

Evaluation of photoresist outgassing for Extreme Ultraviolet Lithography Extreme Ultraviolet (EUV) light is currently of increased interest in semiconductor processing. EUV Lithography (EUVL) is the leading candidate for 15nm half-pitch device manufacturing and beyond. One of the concerns of this process technology is related to outgassing of materials in the vacuum environment – e.g. from photoresists –, which, enhanced by the EUV irradiation, can result in a reflectivity decrease of the optical elements and in other decrease of exposure tool performance. In this field the student would work at imec on an experimental outgassing set-up (Fig. 1) to evaluate the EUV related outgassing and contamination and is involved in outgassing analysis of various photoresist materials. This will contribute significantly to the understanding how materials and process conditions can impact contamination in the EUV scanners, and lead to procedures to qualify resist materials before they are used on the EUV scanners.

Fig.: Experimental EUV outgassing set-up at imec for investigation of outgassing of lithography materials.

Type of project: Preferably internship project of minimum 6 months Degree: Master in Science or Master in Engineering majoring in physics, material science, chemistry Responsible scientist: For further information or for application, please contact Ivan Pollentier ([email protected]).

Deposition, characterization and application of dielectric films New dielectric films are being developed for many applications in integrated circuits. Dielectric films are, in general, used to form an electrical insulator between active devices-transistors and/or electrically conducting metal lines. Their main characteristics are: • good uniformity over the wafer • high resistivity • controlled stress • hardness and Young’s modulus

Master Thesis/Internship Topics 2013-2014

11

The deposition process also has the following needs: • reproducibility and compatibility with other process steps in the manufacturing of the integrated circuit • the adhesion of the film to films below and above has to be assured • a good reliability of the IC, which is strongly dependent on the quality of the dielectric films The characterization of thin dielectric films consists of several phases. At imec, we start with the determination of thickness, refractive index, density, chemical composition through Fourier Transform Infrared spectrometry, stress, Young’s modulus, hardness, porosity, hydrophilicity and dielectric constant of the films. If this characterization looks promising, a second series of tests which simulate other (former and later) process steps, are performed; this also includes tests to determine the adhesion to other films, mainly by 4 point bending analysis. Also, a more detailed chemical analysis, e.g. through XPS and TOFSIMS, will be performed. If all tests are positive, finally, the material is used in an integration process, resulting in a real test chip and the final electrical characterizations (including reliability characterizations) are made. The student will be very strongly involved in the detailed characterization of the basic film properties. Hereby (s)he will use state of the art analysis equipment, such as ellipsometers, a Fourier Transform Infrared spectrometer, a high precision mass measurement system, and others. Furthermore (s)he will also be involved in the next phase of the characterization cycle, as setting up the processes for the simulation of integration aspects and the electrical characterization on test chips. Academic and industrial results will be reported in meetings where both imec staff and industrial affiliates participate. Type of project: Internship project of 6 months Degree: Master in Science or Master in Engineering majoring in material science, chemistry Responsible scientist: For further information or for application, please contact Patrick Verdonck ([email protected]).

Development, characterization and application of pore sealing treatments New low-k dielectric films are being developed for many applications in integrated circuits. The new low-k films are quite porous and have large pores. During the integration of these low-k films into an integrated circuit, it is necessary to seal these pores in order to obtain structures with a high reliability. The pore sealing process has to obey demanding requirements, such as: • the final thickness of the pore sealing films should be as low as possible, of the order of a few nm • the dielectric constant of the pore sealing film should be as low as possible, below 4 • during the deposition of the pore sealing film, the pores in the bulk of the low-k film have to remain open • the pore sealing treatment should damage the low-k film as little as possible At imec, we have already started to explore different routes for these pore sealing treatments. The deposition of both dielectric and metal films is being studied. Also the combination of different treatments (plasma, application of self assembled monolayers etc.) are being investigated. Pore sealing of different materials is being tested, as well on films with a dielectric constant of less than 2.0 and very large pores, with a pore diameter up to 4 nm, as on films with a dielectric constant of 2.4 with a pore diameter of less than 1 nm. Different characterization techniques are applied. Ellipsometric porosimetry is very important to detect the sealing of the treatments. Also determination of the final dielectric constant by C-V measurements is essential. Besides these, the most interesting film stacks are also being characterized by other techniques such as: Fourier Transform Infrared spectrometry, XPS and TOFSIMS. If these tests yield positive results, the new treatment is used in an integration process, resulting in a real test chip and the final electrical characterizations (including reliability characterizations) are made.

Master Thesis/Internship Topics 2013-2014

12

The student will be very strongly involved in the detailed characterization of the film-stack properties. Hereby (s)he will use state of the art analysis equipment, such as ellipsometers, a Fourier Transform Infrared spectrometer, a high precision mass measurement system, C-V meters and others. Academic and industrial results will be reported in meetings where both imec staff and industrial affiliates participate. Type of project: Internship project of 6 months Degree: Master in Science or Master in Engineering majoring in material science, chemistry Responsible scientist: For further information or for application, please contact Patrick Verdonck ([email protected]).

Hot carrier reliability on advanced logic/DRAM devices The continuous device scaling down allows the integration of a large number of transistors on a chip and increases the speed. However since the 65 nm node, the VDD is saturating at a level around 1V due to the non-scaling subthreshold slopes of the MOSFET’s. And this increases electric fields with scaling, makes hot carrier reliability an very important issue. In this study, hot carrier degradation in very thin EOT regime will be investigated by exploring defects in the gate oxide/ junction. Also, the impact of the process conditions including different high-k stacks and/or device structure will be studied. For the applicant, a good knowledge of semiconductor physics is required. During the project, the student will have the opportunity to participate and interact with the researchers of the Logic/DRAM program. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in material science, physics, electronics Responsible scientist: For further information or for application, please contact Moon Ju Cho ([email protected]).

Master Thesis/Internship Topics 2013-2014

13

Investigation of advanced self-rectifying resistive switching memory cells (SRCRRAM) Resistive Random-Access-Memory (RRAM), based on resistance switching mechanisms, is emerging as a potential nonvolatile memory candidate for below-20nm technology nodes, due to its better scalability, beyond the limits currently predicted for NAND Flash. 10nm-small RRAM cells are shown to have low voltage operation, very fast switching time, in the order of ns and below, small energy consumption per switching and good reliability. To take on the benefits of these excellent attributes to circuit level and enable high density memory array implementation, additional self-rectifying functionality is required for the resistive switching stack and needs to be achieved within a two-terminal, 10nm scalable structure. The main task of this internship/thesis is to screen new resistive switching memory concepts with the aim of assessing their potential for self-rectifying memory cells and/or investigate RRAM cells that show self-rectifying characteristics, with the aim of understanding the switching behavior, relate it to intrinsic performance and identify paths for further improvement/optimization. You will be involved in electrical characterization, focusing on performance and/or reliability aspects. You will be using state-of-the-art instrumentation and you will apply statistical principles in data collection using in-house developed characterization methodologies, so as to ensure a short response time in characterization. You will process data and assist in their interpretation. Feedback for process improvement is a key point. You must have a good background in semiconductor physics and knowledge of CMOS technology. You must be fluent in at least one programming/data analysis environment such as Matlab or similar and familiar with LabView and basic instrumentation for electrical testing. You will work in an international R&D team; a good command of English language is required. The detailed content of the work will be defined at the moment of starting this project, in line with latest research priorities. Type of project: Internship or thesis project of 6 months Degree: Master in Science or Master in Engineering majoring in electronics, electrical engineering, physics Responsible scientist: For further information or for application, please contact Bogdan Govoreanu ([email protected]).

Self-assembled monolayers as enabling technology for microelectronics As the total transistors and interconnect sizes come down to few tens of nanometers a shift in paradigm for the manufacturing and integration of microelectronics components becomes apparent. Organic molecules - owing to their size, mechanical flexibility and chemical tunability - fit well in this slot and, thus, are expected to play a key role in IC downscaling. In this respect, self-assembled monolayers (SAMs) seem the best candidates. SAMs are a prototypical form of nanotechnology: the SAM precursor molecules carry the “instructions” required to generate an ordered, nanostructured material without external intervention. SAMs demonstrate that molecular-scale design, synthesis, and organization can generate macroscopic materials properties and functions. Although the details of the thermodynamics, kinetics, and mechanisms of assembly will differ significantly, these monomolecular films establish a model for developing general strategies to fabricate nanostructured materials from individual nanometer-scale components. Because SAMs can assemble onto surfaces of any geometry or size, they provide a general and highly flexible method to tailor the interfaces between nanometer-scale structures and their environment with molecular (i.e., subnanometer scale) precision. SAMs can control the wettability and electrostatic nature of the interfaces of individual nanostructures and thus their ability to organize into large assemblies adding chemical functionality, thermodynamic stability (e.g., improving the adhesion at the dielectric/metal interface).

Master Thesis/Internship Topics 2013-2014

14

In particular, metallization of SAMs, i.e. the formation of metallic or barrier overlayers or clusters on top of monomolecular organic films, is of great importance for many areas of fundamental and applied research. Albeit this problem was actively addressed in the last years, reliable methods to the deposition of metal on top of the SAM are continuing to be a topic of intense research. This task is challenging since most of the studies show an undesirable metal penetration through the SAM. It is generally believed that this is caused by structural defects in the monolayer. Cu is the interconnect material of choice in the metallization step for advanced semiconductor device manufacturing. The current approaches to Cu metallization include chemical vapor deposition (CVD), physical vapor deposition (PVD), selective electroless deposition (ELD) and electroplating. The purpose of this work is to characterize and benchmark the thin SAM organic films deposited both in liquid phase and vapor phase on full 300mm wafer scale as a function of the ELD films quality. The effects of the SAMs chemistry (functional groups, vapor vs. liquid phase deposition, deposition solvents etc...) and ELD experimental conditions on the deposition mechanism and efficiency of the electroless Cu bath (e.g. in terms of Cu thickness and roughness control, adhesion at the interfaces dielectric/SAMs/Cu..., which will be characterized by the student) will be investigated. Type of project: Thesis and/or internship project of minimum 6 months Degree: Master in Science or Master in Engineering majoring in chemistry, material science Responsible scientist: For further information or for application, please contact Silvia Armini ([email protected]).

Advanced barrier CMP slurry development In order to build even smaller devices, very narrow structures have to be filled with copper to achieve advanced interconnects. The aspect ratio of these lines makes them hard to fill without defects and voids. One of the approaches that helps the deposition of copper into narrow structures is to vary the underlying barrier-seed layer. The choice of this layer improves copper electroplating and can make ELD Cu deposition possible. In the subsequent processing steps, the copper as well as the underlying barrier-seed layer needs to be removed in the field area, leaving conducting material only within the interconnect structures. This is achieved through a Cu Chemical Mechanical Polishing (CMP) step followed by a barrier CMP step (which removes the barrier-seed layer). When polishing these barrier layers using CMP, there are several process issues that can occur. First of all, the barrier metal needs to be removed quickly and evenly, which can be hard due to native oxides on the surface. Second, it is necessary to keep corrosion issues under control during the CMP process. The goal of this project is to optimize barrier-seed layer removal rates on blanket wafers while limiting (galvanic) corrosion using model slurries which are optimized for barrier CMP. In order to achieve a good removal rate, different oxidizers and complexing agents are added to model slurries while surfactants/inhibitors are added to protect the surface against corrosion and improve planarity. Static etch rates for these slurries need to be determined to estimate extent of static corrosion. Other CMP parameters (e.g. pressures, flow rates) can be adjusted to further improve the process. Basic electrochemical measurements can be done as well to determine the effect on the corrosion currents in the Cu-barrier CMP system for different slurry additives. For the best performing slurries, it needs to be ascertained that the defectivity and planarity of the polished surface is good. Performance with respect to other device materials needs to be checked. Time permitting, these slurries may be tested on patterned wafers as well as on other advanced barrier materials. Applied techniques include CMP on our experimental polisher, sheet resistance measurements, defectivity analysis, electrochemical tests, etc. A basic knowledge of chemistry is necessary, some experience in electrochemistry is a plus.

Master Thesis/Internship Topics 2013-2014

15

Type of project: Internship or thesis project of minimum 3 months Degree: Master in Industrial Sciences or Master in Science majoring in chemistry, chemical technology, materials science, physics Responsible scientist: For further information or for application, please contact Lieve Teugels ([email protected]).

Development of a ramped voltage BTI procedure for fast gate dielectric testing As the vertical scaling of the conventional poly-Si/SiO2/Si field effect transistors (MOSFET) reached the nanometric scale, the high electric field dropping in the oxide resulted in an intolerable gate leakage current. At that point, industry opted for replacing the conventional SiO2/poly-Si structure by high-k/metal gate stacks that tolerate physically thicker oxide while keeping or even increasing the oxide capacitance. Once the leakage current issue was circumvented, the so-called bias temperature instability (BTI) is becoming one of the most critical factors, complicating the qualification of the future technology nodes [ 1, 2, 3]. Furthermore, the number of stochastically behaving gate oxide defects in each device decreases to a numerable level due to the lateral downscaling, while their relative impact on the device characteristics increases. For all these reasons, BTI lifetime cannot be described any longer by a unique number, and BTI lifetime distribution has to be taken into consideration. As a consequence, even in the ideal case of the average BTI lifetime meeting the ITRS [ 4] specifications, a fraction of nanoscaled devices will fail at low overdrives. The main task of this thesis/internship is to develop a fast methodology to assess NBTI lifetime distributions. A ramped voltage BTI procedure is proposed as fast alternative to the time consuming current methodology. This includes the adaptation of the test software, the demonstration of the finished routine, the benchmark with the classical BTI routine and eventually the electrical testing of advanced gate stacks. [1] E. Cartier, A. Kerber, T. Ando, M. M. Frank, K. Choi, S. Krishnan, B. Linder, K. Zhao, F. Monsieur, J. Stathis and V. Narayanan “Fundamental aspects of HfO2-based high-k metal gate stack reliability and implications on tinv-scaling,” in Proc.: IEDM 2011, pp. 441-444. [2] M. Cho, M. Aoulaiche, R. Degraeve, B. Kaczer, J. Franco, T. Kauerauf, Ph. J. Roussel, L. Å. Ragnarsson, J. Tseng, T.Y. Hoffmann and G. Groeseneken, “Positive and negative bias temperature instability on sub-nanometer EOT high-k MOSFETs,” in Proc.: IRPS 2010, pp. 1095-1098. [3] J. Franco, B. Kaczer, G. Eneman, J. Mitard, A. Stesmans, V. Afanas'ev, T. Kauerauf, Ph.J. Roussel, M. Toledano-Luque, M. Cho, R. Degraeve, T. Grasser, L.-Ǻ. Ragnarsson, L. Witters, J. Tseng, S. Takeoka, W.-E. Wang, T.Y. Hoffmann, G. Groeseneken, “6Å EOT Si0.45Ge0.55 pMOSFET with optimized reliability (VDD=1V): Meeting the NBTI lifetime target at ultra-thin EOT,” in Proc.: IEDM 2010, pp.70-73. [4] International Technology Roadmap for Semiconductors available at http://public.itrs.net.

Type of project: Internship or thesis project of 6 months preferably Degree: Master in Industrial Sciences or Master in Science or Master in Engineering Responsible scientist: For further information or for application, please contact Maria Toledano Luque ([email protected]).

Master Thesis/Internship Topics 2013-2014

16

Compact modeling of advanced transistors As CMOS technology is entering the 10nm and sub-10nm technology era, important innovations are introduced in the device design and even in the device concepts. New constraints are also appearing such a layout dependent effects. To enable circuit design based on these new transistors and behaviors, the compact models used for circuit simulations must evolve accordingly. Working on compact modeling allows to have a very broad view on the field of semiconductors, from fabrication constraints towards device physics, and taking into account system level requirements. The goal of this project is to model modern devices (FinFETs) fabricated at imec. This work will imply reviewing the standard methodology used in transistor compact modeling, setup the required experiments to extract key transistor model parameters, perform the measurements, and use the results to build compact models based on Silicon data. Industry standard software for compact model extraction will be available, as well as access to all technical information required to perform compact model extraction. The student will be part of the compact modeling team and interact with device developers and circuit designers. Type of project: Internship or thesis project of 6 months Degree: Master in Engineering majoring in (micro)electronics Responsible scientists: For further information or for application, please contact Morin Dehan ([email protected]) and Marie Garcia Bardon ([email protected]).

Modeling of temperature effects in advanced devices As technology feature sizes are reduced, temperature becomes an important parameter in devices and in circuit design. Temperature impacts strongly the speed, the power and the reliability of circuits. Massive amounts of heat are generated by the higher and higher density of power with lower access to cooling. The low access to heat dissipation can even generate "self-heating" effects, for example in FinFETs. In parallel, the use of advanced materials stacks change the sensitivity of devices to temperature and can even reverse well-known trends used to design circuits. These effects have to be understood and captured in device compact models to be transferred at circuit design level, where their impact will be evaluated and solutions could be found. The goal of this project is to understand and model how temperature affects device functionality in bulk and SOI FinFETs, as well as to understand the impact of scaling on temperature variations. The study will be based on measurements of imec devices. The modeling and understanding will be mainly based on use of industry standard compact models such as BSIM to produce model cards for circuit simulation. The student will be part of the compact modeling team but also interact with the device characterization engineers and circuit designers. Type of project: Internship or thesis project of 6 months Degree: Master in Engineering majoring in (micro)electronics Responsible scientists: For further information or for application, please contact Morin Dehan ([email protected]) and Marie Garcia Bardon ([email protected]).

Master Thesis/Internship Topics 2013-2014

17

Characterization and modeling of oxide border traps in Ge/III-V MOSFETs Recent developments on CMOS-driven III-V and Ge MOS (Metal-oxide-semiconductor) technologies provide new opportunities in advancing the performance envelope of logic devices as well as lowering the operating power. The quest of high speed/low power post-Si CMOS with heterogeneous integration calls for in-depth studies on various aspects including device modeling and characterization, performance benchmarking, reliability/passivation/contact studies and ultimately, scaling beyond 10nm node. Recently, the impact of oxide traps (border traps) on device performance has been demonstrated [1] on III-V and Ge MOSFETs. The proposed research activities for the internship include (but not limited to): 1. Electrical characterization of III-V/Ge planar MOS- and FIN- FETs for gate stack performance, and oxide and interface evaluation (Admittance analysis, AC-transconductance, charge pumping... ), paired to device benchmarking. 2. Modeling and simulation: relating the border traps and electrical results measured on devices with different channel materials, gate stacks and layer structures. [1] D. Lin, et al, p. 645 IEDM 2012

Type of project: Internship or thesis project Degree: Master in Science or Master in Engineering majoring in electrical engineering, physics, materials science Responsible scientists: For further information or for application, please contact Koen Martens ([email protected]) and Dennis Lin ([email protected]).

Interface stability and reliability of high-mobility channel MOSFETs After the end of conventional CMOS scaling era, unabated enhancement of the device performance has been guaranteed by materials and architecture innovation. Three main technological breakthroughs have been introduced in recent CMOS nodes: strain engineering (90nm node), high-k/metal gate technology (45nm) and trigate (finFET) architectures (22nm). A new innovation will be soon needed for continued equivalent scaling in future nodes. One of the most promising options currently under consideration is the introduction of high-mobility channel materials, namely Ge-based channels for pMOS and III-V compounds for nMOS. However, significant technological challenges remains to be solved. In particular, interface passivation of non-Si channel materials is a critical issue which severely impacts the device performance and reliability. Moreover, further challenges derive from the need of integrating such novel materials in the novel finFET architecture and in combination with previously introduced innovations (strain-engineering, high-k/metal gate stacks). The main task of this thesis/internship is the electrical characterization of high-mobility channel device prototypes. This includes the use of several measurement approaches (I-V, C-V, pulsed I-V, Charge Pumping, Measure-StressMeasure techniques) with both manual and semi-automatic computer-controlled measurement setups. Type of project: Internship or thesis project of 6 months preferably Degree: Master in Industrial Sciences or Master in Science or Master in Engineering Responsible scientist: For further information or for application, please contact Jacopo Franco ([email protected]).

Master Thesis/Internship Topics 2013-2014

18

Carbon nanotube contacts: electrical characterization of CNT – damascene contacts Carbon Nanotubes (CNT) have remarkable electrical, thermal and mechanical properties that make them interesting candidates as a metal in future contact applications where conventional metals cannot meet the required specs that come with the extreme scaling in nanotechnology. At imec, CNT interconnects are being created and electrically evaluated inside 150nm diameter contact holes. All steps for the CNT integration, the steps for patterning the Cu damascene top contact, and the mask set used are compatible with 130nm device technologies on 200mm wafers.[1,2] Our new platform is designed for automatic electrical testing using Kelvin vias, parallel vias or other probing pads. This project is focusing on improving the CNT quality to reduce the contact resistance [1-3]. In parallel, splits in the integration module on the top contact are included to obtain more insight in the CNT-to-metal contact. The electrical performance studies have the objective to obtain a detailed understanding of the CNT interconnect and find ways to improve the CNT interconnect performance. The purpose of the project is: (1) Obtaining a better understanding of the behavior of the CNT interconnect under stressed conditions (high frequency, breakdown, aging, reliability...), supported by theoretical modeling. (2) Developing a theoretical model that can be validated experimentally to distinguish the resistance from the CNT and bottom and/or top contact. The CNT growth and integration work is realized in a cross-functional team bridging the two groups of Prof. Dr. S. De Gendt and Dr. Zs. Tökei (team InterConnect Integration). [1] van der Veen et al., IEEE IITC conf. proc. (2012) 14.2 [2] van der Veen et al., “Electrical Characterization of CNT contacts with Cu damascene Top Contact” Microelectron Eng. (2013) http://dx.doi.org/10.1016/j.mee.2012.09.004 [3] Chiodarelli et al. Nanotechnology 22 (2011) 085302.

Cross-section of the electrical structure showing four 150nm contact holes filled with CNT and metallized with Cu single damascene top contact

Type of project: Internship or thesis project of minimum 4 months Degree: Master in Science or Master in Engineering majoring in physics, electronics, material science, nanotechnology Responsible scientists: For further information or for application, please contact Yohan Barbarin ([email protected]) and Marleen van der Veen ([email protected]).

Master Thesis/Internship Topics 2013-2014

19

Carbon nanotube growth and its catalyst nanoparticle deposition for future contact applications Due to their remarkable electrical, thermal and mechanical properties, carbon nanotubes (CNT) have been considered for various applications in different fields of research. One particular application, situated in the world of integrated circuits, is a CNT based interconnect and CNT contacts. Various reports exist in literature where the growth of CNT with a high quality is demonstrated. However, most of these results are obtained under process conditions that are not fully CMOS compatible and hence cannot be used in nanoelectronic applications in CMOS. The aim of this project is to investigate and develop a CMOS compatible growth process that results in high quality CNTs. The CNTs need to be grown in very small via features (sub 22 nm) or structures with a high aspect ratio (diameter with respect to depth of the hole), as is projected for future generations of interconnects and other contact applications (Figure 2). The most important boundary conditions for this CNT growth are: 1) Catalyst placement on the bottom of the deep hole. 2) Achieve CNT growth directly on conductive substrates.

Figure 1: Schematic view of CNTs in small via features ( 6eV) do break the Si-CH3 bonds as well, causing chemical and structural re-organization of the material, with appearance of high-polarity bonds and densification. Both together, plasma radicals and VUV act synergetically, leading to even higher damage. An option to overcome these issues is the so-called pore stuffing approach, where, once formed, interconnected pores of the p-SIOCH are temporary filled with another material. Right now, conventional polymers have shown good filling and decent protection properties, however on one hand their VUV absorption spectrum is weak, while on the other hand they are easily thermally decomposed which poses some issues for subsequent process steps, namely TaN/Ta barrier deposition. There is therefore a need to study other type of filler materials, showing a higher optical

Master Thesis/Internship Topics 2013-2014

26

absorption in the VUV range and better thermal stability, but still being removable later in the process flow (typically after metal CMP). The details of the proposed internship are therefore as follows: 1. The research will follow an intense in-house training allowing him to get familiar with the cleanroom tools and working environment (safety), then with the different experimental techniques required by the project. 2. Starting from the in-house 2.0 p-SiOCH dielectric film (called ALKB+), and the physico-chemical properties of the envisioned filler material, the researcher will optimize the filling conditions so as to obtain the best possible filling, i.e. > 85% of the free volume. At this stage, numerous thin film characterization methods will be intensively used. 3. Once the best filling conditions will be found, the researcher will characterize the plasma-damage characteristics of the resulting hybrid film, looking especially at the impact of VUV, and comparing it to more conventional fillers. Bulk k-value will be evaluated, as well as chemical & structural modifications caused by plasma exposure. Simultaneously, the thermal stability of the hybrid film will be checked up to 350°C, and removal (burn-out) approaches will be investigated. Techniques for such a study are broad and represent a significant part of the stay: deep understanding of 300mm etch tool usage, work with coupons and optical filters, thin film characterization (ellipsometry for thickness-n&k, FTIR or ATR-FTIR for bulk composition, WCA for film hydrophobicity, XRR for density, k-value extraction by C-V measurements on metal dots, porosity by ellipsometric porosimetry). More specific material characterization (XPS, TOF-SIMS) may be requested to the Material Characterization & Analysis (MCA) group. Type of project: Internship or thesis with internship project of 6 up to 12 months Degree: Master in Science or Master in Engineering majoring in materials sciences, physics, chemistry, electronics Responsible scientists: For further information or for application, please contact Mikhail Baklanov ([email protected]) and J.-F. de Marneffe ([email protected]).

Depth loading study in STI It has been shown that the fluorocarbon-based-passivation STI has some benefits in the profile control for the current small generation nodes , see PESM 2012 (Fluorocarbon-Based Passivation in STI Plasma Etching). Though it can provide a single sidewall slope, required CD, and CDU there is one parameter that would still be interesting to optimize --- it is an ISO /Dense depth loading.

Master Thesis/Internship Topics 2013-2014

27

The objective of the work is to perform various plasma experiments on a SA3 patterned lot in order to reduce the difference in depth of ISO and Dense structures. The experiments are planned to be performed in Kiyo-E chamber. The effect of pressure-power and gas composition is to be studied. Also, the activity can include cooperation with the modeling group, if the new model of STI is ready. Type of project: Internship project of minimum 3 months Degree: Master in Engineering majoring in chemistry, electronics, physics (materials, plasma) Responsible scientists: For further information or for application, please contact Alexey Milenin ([email protected]) and Kaidong Xu ([email protected]).

Advanced materials characterization using ion beam scattering This work will be executed at imec, the leading European micro-electronics research center. Imec does research on a wide variety of front edge micro-electronic devices and applications (transistors, memories, solar cells...). To verify the correct fabrication of these extremely challenging new devices (sub-22 nm technology) also high-end characterization tools are essential. In this framework, accelerator based tools are recognized as versatile solutions for thin film (sub-nm scale) characterization. This topic is an opportunity to learn about fundamental materials characterization techniques in a state-of-the-art nanoelectronics research center. You will be exposed to challenges in current and future CMOS technology. Novel materials processing techniques and characterization approaches have boosted the nanoelectronics industry dramatically. We have witnessed the introduction of high-k materials (e.g. HfO2) replacing the SiO2 insulator in advanced transistors, and metals (e.g. TiN) replacing poly-Si as a gate material. Yet, the introduction of novel materials is expected to be even more essential in the future. Research is ongoing to replace Si by alternative materials that exhibit a higher mobility. Finally, new materials are also needed for the realization and optimization of new devices such as Magnetic memory cells (MRAM), resistive memory (RRAM) cells, conductive bridge resistive memory (CBRAM), photovoltaic(PV) cells, nano-batteries, micro-electromechanical systems (MEMS), light emitting diodes (LEDs) etc. The development of new materials at imec builds also upon the experience and expertise of the materials and component analysis (MCA) department. One of our major tools is an ion accelerator (maximum 2 Mega Volt) with two dedicated end stations; one for Rutherford Backscattering spectrometry (RBS), and another for Elastic Recoil Detection (ERD) experiments. In RBS, essential information from the sample is gained from the residual energy of the scattered projectiles. In ERD, the information comes from the energy of the recoiled target atoms. To attain the best possible detection resolution, the acceleration voltage and the projectile species need to be properly chosen in relation with the nominal sample structure and the known detection schemes. The focus of your work will be to investigate novel materials, e.g. Lithium-containing materials for battery applications, using Elastic Recoil Detection experiments. Till now, at imec, we have been employing mostly a 6 MeV Cl beam for the ERD analysis of thin films. It may be expected that projectile beams other than Cl (e.g. Cu, Br, I) and primary energy other than 6 MeV are more effective in the analysis of certain thin films. Through practical experiments and supported with simulations (software available), you will investigate the capabilities of various ion species and acceleration voltages towards the analysis of new materials. Type of project: Thesis and/or internship project of minimum 6 months Degree: Master in Science or Master in Engineering majoring in materials science, physics, chemistry, electronics Responsible scientist: For further information or for application, please contact Johan Meersschaut ([email protected]).

Master Thesis/Internship Topics 2013-2014

28

Development of an accelerator based metrology application This work will be executed at imec, the leading European micro-electronics research center. Imec does research on a wide variety of front edge micro-electronic devices and applications (transistors, memories, solar cells,...). To verify the correct fabrication of these extremely challenging new devices (sub-22 nm technology) also high end characterization tools are essential. In this framework accelerator based tools are recognized as versatile solutions for thin film (sub-nm scale) characterization. This subject involves the development and implementation of an object-oriented control application within a Visual C++ based programming environment. In particular, the software will have to communicate with various instruments through Ethernet (TCP/IP) and RS232/RS485 (via Serial-Ethernet gateways) and with the user through an extremely user-friendly graphical interface (GUI) as well as support for a flexible scripting language capability. The goal is to achieve this functionality by developing a high quality object-oriented program, paying attention to optimal class structures, efficient usage of polymorphism, re-usability aspects, etc. This project aims at the development of a new software package for the control of an accelerator-based measurement system in a graphical, object oriented, Microsoft Visual C++ programming environment (dialog boxes, menu’s, toolbars, property sheets, etc.). This package will most likely be developed based on the Qt4 (http://qt.digia.com/ ) class library in order to allow the final application to run on any operating system (Windows, Linux, Apple,...). The main tasks will be as follows: • Analyze the present operational system, and design a completely new high-level class diagram for the envisaged multi-threading metrology application. • To implement the necessary communication protocols (with stepper motors, data acquisition, counters) into the Visual C++ environment, with an initial user-interface for testing purposes. • To design and implement a user-friendly graphical user interface (GUI) and scripting capability to interact with the hardware. The software will be designed such that new devices can be connected and disconnected dynamically during the operation, and should appear as virtual instruments on the screen. The signals from various virtual instruments are accessible to both virtual super-instruments as well as scripts that can be run in a command-like environment. The various instruments should be accessed in parallel, i.e. multiple threads may be needed. Ideally, the software allows access to the control application from various locations (locally and remotely) and by various users (multi-user). This subject is a challenge for those who wish to specialize themselves in all aspects and capabilities of objectoriented programming within a Visual C++ based environment. Type of project: Thesis project of 1 year with a 4 weeks internship Degree: Master in Industrial Sciences majoring in electronics/ICT Responsible scientists: For further information or for application, please contact Johan Meersschaut ([email protected]) and Trudo Clarysse ([email protected]).

Master Thesis/Internship Topics 2013-2014

29

Analysis of surface preparation for HV and UHV-SSRM The SSRM technique is an AFM-based technique used to obtain 2D carrier maps of electronic devices (MOS, bipolar transistors, FinFets, TFETs,…) with (sub)-nm resolution. Samples therefore need to be cross-sectioned (polishing or cleaving). The latter may lead to artifacts such as Fermi-level pinning, surface states, native oxide,…

High Vacuum-SSRM, and recently Ultra High Vacuum-SSRM, versions have been introduced with improved performances relative to the ambient version, due to water layer removal, as well as reduced/suppressed native oxide growth, contamination and anodic oxidation during the measurements. In order to fully benefit from the vacuum, a more detailed understanding of the impact of the measurement environment is required as well as the role of eventual passivation procedures and cleaning/heating treatments after cross section preparation. Task of the student(s) will be to study these effects and to correlate the electrical (HV-SSRM and UHV-SSRM) performance with existing models for the high pressure SSRM-contact. The latter will involve studies on spatial resolution, ohmic contact formation (through studies of I-V curves), tip and sample erosion, and life time (regrowth, oxidation,..) of the sectioned surface. Type of project: Internship project of 6 months Degree: Master in Engineering majoring in chemistry, physics Responsible scientist: For further information or for application, please contact Pierre Eyben ([email protected]).

Active dopant characterization with micro-probes on advanced ultra-shallow highmobility CMOS semiconductor structures As CMOS devices get smaller with each technology node, the processes needed to fabricate and characterize these also become more and more complex. Moreover, the fast introduction of new high mobility materials (Ge, SiGe, III-V) additionally complicates the electrical analysis of these new structures. Ultimately one is interested in the characterization of the electrically active portion of the implanted dopant species, either in extremely shallow blanket layers (sub-20 nm) or small structures (50x50 um pads down to 20-100 nm wide trenches) or layers with carriers of different mobility signature (interface versus bulk behavior)

Master Thesis/Internship Topics 2013-2014

30

On blanket layers the active dopant portion can in principle be determined by combining Secondary Ion Mass Spectrometry (SIMS) profiles (for depth information) with surface sheet resistance or conventional Hall measurements. The latter give additionally information about the sheet carrier (= active dose) and exact mobility of the surface layer. Conventional Hall, however, suffers from contact penetration issues and needs quite large areas (cm). Recently a new virtually zero-penetration micro-probe (10 um pitch) based tool (CIPT), from Capres, has been installed at imec, which allows micro-Hall measurements close to the edge of a blanket sample (5 um distance) in the presence of a 600 mT magnetic field. The accuracy of these measurements on many of the new materials, however, still needs to be further investigated. Among others, values for the Hall scattering factor need to be determined. Subsequently, one needs to be able to extract the active dopant information on ever smaller structures (50x50 um) and thinner 250 nm deep trenches (20 nm wide), taking into account two-dimensional and side-wall effects. For some of these challenging structures new extraction algorithms will need to be developed based on the understanding obtained through Synopsis/Sentaurus device simulations. For trenches also specialized reference (calibration) characterization structures will be developed and fabricated. Besides the study of ever shrinking structures, another issue is being able to discriminate between carriers with different mobility’s in the same layer, for instance in the neighborhood of an interface or in the bulk of the layer. For such a characterization a variable magnetic field will be considered giving rise to a field dependent mobility spectrum. Measurement procedures and physical understanding for such types of measurements will have to be developed. The major steps in this work will be: (i) Familiarizing oneself with the CIPT (and micro-four point probe M4PP) tools and related software and underlying theoretical publications, (ii) Extending the capabilities of micro-Hall measurements on blanket films in different new materials, (iii) Explore the capabilities of micro-Hall on different types of small structures and develop a theoretical framework for the obtained results, (iv) Investigate the behavior of micro-Hall measurements in the presence of a variable magnetic field. Type of project: Internship or thesis project of minimum 6 months Degree: Master in Science or Master in Engineering majoring in physics, electrical/electronic engineering, material science Responsible scientist: For further information or for application, please contact Trudo Clarysse ([email protected]).

Development of a professional data analysis package for the micro-four point probe (M4PP) The micro-four point probe (M4PP) is an electrical technique that allows for the very accurate measurement of the (sheet) resistance of a very thin (sub-100 nm) highly conductive semiconductor layer on top of a substrate of opposite impurity type (n- or p-type) (by pushing a current through the outer two probes and measuring the resulting voltage difference between the inner two probes). In 2009 such a M4PP tool has been installed at Imec. The tool came with commercial software (from Denmark) for the sheet resistance raw data collection, but not for the data manipulation of the many different data files or consequent data interpretation. When applying this technique to a bevelled surface (slanted), one can generate a sheet resistance versus depth profile, from which the underlying carrier depth profile can be extracted. The latter is of crucial importance for the development of future state-of-the art transistors. In 2010-2011 an initial version of a brand new M4PP data treatment software package named “Tivoli” has been implemented. During the next (second) academic year Tivoli was enhanced among others with improved smoothing capabilities, a graphics overlay module and printing capability.

Master Thesis/Internship Topics 2013-2014

31

The goal of the third working year of this project is, to continue the development of the Tivoli package for both surface sheet resistance+mobility and carrier depth profiling analysis. The programming environment is Microsoft Visual C++, with the Qt4 class libraries (http://qt.digia.com/) and Qwt graphics libraries (http://qwt.sourceforge.net/ ). Issues involved in this work will be: (i) For surface analysis, making different types of result plots/maps (resistance/voltage versus position, two-dimensional 200- and 300 mm resistance contour maps, etc.) and implementing support for a new micro-probe CIPTech tool allowing to extract mobility data from the measurements, (ii) For carrier depth profiling, implementing probe pitch correction algorithms and adding support for two point (so called spreading resistance) measurements, which have a smaller sampling volume, (iii) Adding further support for making overlays with profiles from other dopant and carrier characterization techniques, (iv) Eventually semi-automatically generation of analysis results reports (in MS Word or PDF format). It is not the aim of this work to develop new data treatment “algorithms’. This subject is, however, a challenge for those who wish to specialize themselves in all aspects and capabilities of object-oriented Windows programming within the Visual C++ environment with a signal-slot architecture (Qt) environment, focusing on a truly userfriendly graphical user interface (GUI). Type of project: Thesis project of minimum 6 months with 1 month internship Degree: Master in Industrial Sciences majoring in electrical/electronic engineering, ICT Responsible scientist: For further information or for application, please contact Trudo Clarysse ([email protected]).

Fundamentals of nanoscopic materials removal The high potential of three-dimensional (3D) electrical atomic force microscopy (AFM) has recently been demonstrated; for example by probing the electrical properties of carbon nanotube based interconnects. Our method uses scanning spreading resistance microscopy (SSRM) and applies a slice-and-view approach where material is removed on the nanometer scale by successive tip scanning. In-house made boron-doped diamond tips are used for both continuous material removal by successive scanning and for the actual electrical measurements. By stacking and interpolating between the individual 2D SSRM resistance maps, one can obtain an electrical tomogram. The further development of this 3D electrical AFM method crucially depends on understanding the fundamentals of nanoscale material removal using doped diamond tips. This topic investigates the basics of nanoscopic material removal using in-house developed full diamond tips. It is the aim to develop procedures allow for adjustable scan removal rates of about 1-10 nm/scan on hard materials like silicon, germanium and silicon oxide. Three different tip configurations are evaluated in this work: pyramidal tips, knife-shaped tips (45° rotated on cantilever) and in-plane tips (triangular shape with tapered end). The latter configuration strongly facilitates locating the region of interest as the tip region is clearly visible in the optical microscope of the AFM. Operating such diamond probes in slicing motion only, can be exploited for nanomachining purposes as well. The student will optimize the tip performance for making reference marks and removing passivation layers. The final outcome of this work are probe concepts and scanning approaches enabling the nanoscopic controlled removal of semiconductor materials. The student will work in a state-of-the-art materials characterization lab. He/she will be trained in working with AFM and in particular with SSRM. For probe tip inspection, scanning electron microscopy (SEM) is used. The student will be part of the materials and component analysis (MCA) department. Type of project: Internship project of 6 months Degree: Master in Science or Master in Engineering majoring in physics, electrical engineering, material science Responsible scientist: For further information or for application, please contact Thomas Hantschel ([email protected]).

Master Thesis/Internship Topics 2013-2014

32

Strain characterization in advanced transistor structures using Raman Strain engineering is used as a concept in most advanced nanoelectronics transistor structures to enhance the mobility of electrons (or holes) in the channel region and thereby increasing the channel conductivity. This is achieved by various approaches (e.g. strain-inducing capping layers, using a silicon-rich solid solution such as SiGe). PMOS and NMOS respond differently to the applied strain. PMOS benefits from applied compressive strain whereas NMOS performance is supported by tensile strain. The use of such stress-engineering implies also the possibility to measure locally the stress inside the channel region. In this topic, the use and optimization of the Raman method is investigated for measuring the local stress in state-of-the-art FinFET transistor structures. Raman is an optical technique and relies on inelastic scattering of photons which means that the energy of photons in monochromatic light changes upon interaction in a sample. The student will learn to work with a micro-Raman system using different laser wave lengths. The experimental focus is on using the nanometer-scale dimension of the device to locally increase the Raman signal originating from the channel region. The student will be trained in working with a Raman system and characterize advanced device structures. He/she will be part of the materials and component analysis (MCA) department. Type of project: Internship project of 6 months Degree: Master in Science or Master in Engineering majoring in physics, electrical engineering, material science Responsible scientist: For further information or for application, please contact Thomas Hantschel ([email protected]).

Non-destructive assessment of electrical properties of nanoscale probe tips Doped diamond tips have been developed for carrier profiling of state-of-the-art semiconductor devices with a spatial resolution of 1nm. They are mainly used for scanning spreading resistance microscopy (SSRM) which uses a high pressure in the GPa range to establish a good electrical contact to the silicon. Despite the high resolution of such tips, their overall fabrication yield is still limited to about 30-50%. A tip evaluation procedure does exist to determine the yield for a particular probe wafer but the actual testing affects the tip properties and can hence not be used for tip qualification (predicting the tip performance without tip wear). Therefore, in this topic a nondestructive approach is developed and optimized based on local I-V measurements at low forces. Moreover, it is the aim of this internship to better understand the mechanism behind the formation of the nanoscale electrical contact and to link the observed high tip resolution in SSRM to the physical properties of the apex of the diamond tip. For this, the obtained I-V tip characteristics are compared to the actual tip performance in SSRM (resolution, conductivity) and to the physical shape/geometry of the diamond tip apex. The final outcome is a non-destructive tip qualification procedure and gaining better insight into the diamond tip to substrate interaction. For this, the student is going to working a modern materials characterizations lab and will be trained to operate an atomic force microscopy (AFM) system, to perform SSRM measurements and to collect I-V measurements for tip evaluation. After the training period, the student will independently perform the electrical and physical tip assessment. He/she will be part of the materials and component analysis (MCA) department. Type of project: Internship project of 6 months Degree: Master in Science or Master in Engineering majoring in physics, electrical engineering, material science Responsible scientist: For further information or for application, please contact Thomas Hantschel ([email protected]).

Master Thesis/Internship Topics 2013-2014

33

Nickel damascene process for MEMS In a previous project, we have started to investigate the properties of electrodeposited nickel (Ni), which is a very interesting candidate for making structures that could be used in a MEMS (Micro ElectroMechanical System). Advantages of Ni are that it has a low electrical resistivity and it is mechanically more robust than most other metals. Therefore, it can be an important metal for building MEMS structures. For building transistors, copper is extensively used in the so-called “Damascene process”, in which various layers are stacked during processing by sequences of patterning-metallization-planarization, in order to build more complex structures (see figure). For this student project, we are going to develop a process in which Ni is deposited inside a patterned structure (e.g. photoresist, oxide) and the student will be executing many of these processing steps.

Figure - Cross section of a 3-layer Damascene stack, which consists of metal (brown), dielectric (yellow) and stopping layer required for planarization (green), on a silicon substrate.

In the first phase of the project, the student will get familiar with the processing steps, focusing on electrodeposition of Ni and chemo-mechanical polishing (CMP). Initially, the student will work on thin films and investigate the deposition and removal properties of Ni. In the next phase, a patterned structure will be used for which the results obtained during the first phase will be applied. Analysis, interpretation and presentation of the results will be important activities in which the student participates. Execution of experiments on silicon wafers in the IMEC cleanroom. Analysis of samples (e.g. optical microscopy, Atomic Force Microscopy (AFM), Focused Ion Beam (FIB), cross-sectioning, Scanning Electron Microscopy (SEM), resistivity), characterization of deposition and removal uniformity. Project can be done by student as a Master thesis, or as ‘industrial internship’. Background by education: Chemistry, Physics, Engineering. Type of project: Internship project of 6 months Degree: Master student in chemistry, physics, engineering Responsible scientists: For further information or for application, please contact Harold Philipsen ([email protected]) and Lieve Teugels ([email protected]).

Master Thesis/Internship Topics 2013-2014

34

Defectivity monitoring of directed self-assembly In this project the patterning reliability (or defectivity) of our chemo-epitaxy directed self-assembly process will be monitored over time. The initial goal is to demonstrate long term stability of the process and to implement improvements as these are developed in parallel projects. The ultimate goal of the study is to demonstrate the ability of the process to reproducibly deliver low defectivity on full 300mm wafers.

X-PS cross-linking

Lithography

OH-Brush grafting

O2 plasma etch

Chemical Pattern

Rinse

BCP annealing

In our directed self-assembly process (see cartoon above) we use a number of process steps (including optical lithographic patterning, dry etch and spin coating of dedicated polymer materials) to obtain a so-called ‘chemical pattern’. At this stage there is no wafer topography, but only well controlled domains of different chemical surface energies. When a block copolymer of appropriate composition is coated on such a surface, spontaneous frequency multiplication is obtained (see microscope images below). The left image shows the low frequency pre-pattern. The 1st image on the right is the desired result. In some cases, however a defective self-assembly result is obtained (2nd image on the right). In this project the number of such defects on a full 300mm wafer will be quantified.

4

or

Initially the work will mainly focus on metrology, including defect inspection and SEM (scanning electron microscope) defect review in the advanced 300mm imec wafer fab. Depending on skills and interest, wafer processing may be included in a later phase of the project. Type of project: Thesis with internship project of 12 up to 18 months Degree: Master in Science or Master in Engineering majoring in material science, physics, chemistry, chemical engineering Responsible scientist: For further information or for application, please contact Roel Gronheid ([email protected]).

Master Thesis/Internship Topics 2013-2014

35

Modeling of leakage in very high permittivity dielectrics for DRAM applications Future dynamic random access memories (DRAM) require metal-insulator-metal capacitors (MIMcaps) with equivalent oxide thicknesses (EOT) ≤ 0.4 nm, necessitating the introduction of dielectrics with very high dielectric constant (k~100). Furthermore, low leakage current densities (≤ 1e-7 A/cm2) are required for sufficient retention of charge. Regrettably, high-throughput industrial deposition techniques can result in dielectric films with defects that can facilitate electronic conduction. Reducing the leakage thus requires thorough understanding of the role of the defects. The general aim of the thesis is to interpret the measured leakage and capacitance characteristics (IV and CV at varying temperature). This will be achieved by modeling trap-assisted leakage mechanisms in MIM structures with non-uniform electric field due to charge trapped inside the dielectric. Requirements therefore include understanding of the physics of various conduction mechanisms, self-consistent solving of the Poisson equation, and optionally electrical IV and CV measurements. Type of project: Thesis project Degree: Master in Science or Master in Engineering majoring in physics, electronics, nanoscience/technology, material science Responsible scientist: For further information or for application, please contact Ben Kaczer ([email protected]).

Master Thesis/Internship Topics 2013-2014

36

II.

Heterogeneous Integration Calibration of stress sensors for 3D-IC applications The 3D-IC technology enables the high density integration of integrated circuits resulting in the smaller footprint of the chip and at the same time improving the signal integrity and to some extend the power consumption. It also enables integration of different CMOS technologies in one functional 3D module. However the 3D-IC integration introduces an extra complexity into the micro-system thus affecting its reliability and thermo-mechanical stability. To quantify these effects the set of temperature and stress sensors has been developed. The response of these devices has also been measured at different temperatures and at different levels and kinds of the mechanical stresses. The objective of this master thesis is to get more systematic experimental and theoretical information on the sensitivities of the sensors which are available on the different 3D test vehicles. In particular the work will be focused on the calibration of stress sensors at vertical (out-of-plane) stresses and at the calibration of stress sensors at different temperatures. The work will include: • literature study • developing the experimental techniques and the methodology to enable the calibration of different sensors • performing the experiments • analyzing the results and drawing the conclusions Type of project: Thesis project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in material science, physics, electronics Responsible scientist: For further information or for application, please contact Vladimir Cherman ([email protected]).

Master Thesis/Internship Topics 2013-2014

37

III.

Electronics for Healthcare and Life Sciences Studying the function of neural circuits Investigating the computations performed by the brain requires simultaneous recordings from many individual neurons. Moreover, it is essential to dissect and perturb genetically defined functional components of neural circuits to test the effects of these perturbations. Neuroscience is currently constrained by a limited ability to make specific perturbations in neural circuits. Yet, neural circuits are perturbed in various ways during development. As the brain develops, not only the numbers of neurons increase drastically but also the composition of the neural circuits change. Constant spatial and functional reorganization of the developing brain also affects the connectivity between the components of neural circuits. Yet, the brains of both developing and adult animals function properly and generate behaviours essential for life. Zebrafish is a rising model organism for studying the function and development of neural circuits. First, zebrafish brain development and organizational principles are highly similar to the mammalian brain. Zebrafish larvae are optically transparent and posses a small and easily accessible brain for electrophysiology, imaging and optogenetic manipulations. The molecular toolbox associated with zebrafish is well developed, easily accessible and expanding rapidly. The main aim of the proposed research is to understand the fundamental principles underlying the function and development of neural circuits. Towards this overarching goal the successful student candidate will investigate how sensory information is processed along the brain pathways; how this information is stored and recalled in the process of learning and memory; how neural circuits are established in development and which cells give rise to the necessary components of this system; how the neural circuits change throughout development of the embryo and how this relates to the behaviour of the organism. To accomplish these goals, the successful candidate will be trained in functional imaging, electrophysiology, computer based analytical methods and genetics. Using these techniques we will study the activity of thousands of neurons in response to odor stimulation and perturb the genetically defined components of these neural circuits to understand their function in olfactory information processing. Moreover we will develop and use anatomical and physiological methods to trace the functional connectivity of olfactory circuits in both adult and larval zebrafish brain. Ultimately, the experiments that are designed by using these new tools will help us to understand the fundamental principles of sensory information processing in the brains of vertebrates, including humans. Type of project: Internship or thesis project Degree: Master student majoring in engineering, physics, bio-engineering, mathematics Responsible scientist: For further information or for application, please contact Emre Yaksi ([email protected]).

Master Thesis/Internship Topics 2013-2014

38

Measurement of nanomaterial exposure in air Nanomaterials contain objects smaller than 100 nm in at least one dimension, for example, particles, filaments, or sheets. They represent an increasingly important product of nanotechnologies having a wide range of applications from medicine to energy storage. On the other hand, nanomaterials have different chemical and toxicological properties compared to bulk materials and can introduce different environmental and occupational hazards. Important properties determining their biological effect are their aspect ratio and surface area. The literature on measurement strategies for assessing exposure to manufactured nanomaterials is currently very limited, especially regarding airborne exposures. The information base for exposure assessment in workplaces is currently built on a limited database which has to be improved in volume, comparability and reproducibility.

This student topic will combine a literature search regarding the toxicological properties of nanomaterials and laboratory work (scanning electron microscopy SEM, X-ray photoelectron spectroscopy, XPS) eventually determining airborne exposure. We are looking for a candidate with enthusiastic attitude and basic knowledge of physical chemistry. The objectives of this project are to • get familiar with the nanomaterials produced and used in imec; • conduct a literature search about the current literature about measurement strategies; • develop an experimental setup providing controlled release of nanomaterials in the air; • perform physical and chemical characterization of nanomaterials. Type of project: Internship or thesis project of 6 months Degree: Master in Industrial Sciences or Master in Science, majoring in material science, physics, chemistry Responsible scientist: For further information or for application, please contact Dimiter Prodanov ([email protected]).

Sensors for weight management and energy expenditure The development of novel sensors and the deployment of personal body area networks with these sensors are driven by microsystem integration technologies. These wireless networks provide assisted living, sports or increased wellbeing functions for the user, without visible interference with their active lives. Prevention rather than detection and cure will be the future paradigm. In imec's imHealthy program, these body area networks (BAN) with several different types of sensors are currently under development: ECG signals, skin conductance, motion and many more signals can be monitored, recorded and wirelessly transmitted to a personal mobile device during longer periods of time. With the growing availability and acceptance of these sensor networks for improving our life quality, it is becomes attractive to use their information in a multitude of applications.

Master Thesis/Internship Topics 2013-2014

39

Overweight is a growing concern in our society and monitoring it together with tracking our energy (or calorie) burning with BAN based sensors can help us to give timely warning signals, since people are tending to neglect there body signals. In this thesis work, the aim is to study and compare several strategies for monitoring people’s weight and energy expenditure from the signals produced by the sensors in the BAN: e.g. measuring a persons’ activity with a accelerometer on the body together with monitoring the heartrate can give a solid figure for the amount of calories that were dissipated. At the start of this thesis, a study of weight and energy expenditure monitoring methods that are compatible with imec's available BAN sensors systems will be made. After getting acquainted with the BAN hard- and software, an experimental monitoring tool will be developed for the BAN sensors by analyzing the readout signals (from 3D accelerometer, skin conductance sensor for sweat estimation, heart rate sensor) and combining them in a user app that allows informing a person about his/her energy balance. Type of project: Thesis project Degree: Master in (Bio)Engineering, majoring in nanotechnology, (bio)electronics Responsible scientists: For further information or for application, please contact Walter De Raedt ([email protected]) and Chris Van Hoof ([email protected]).

How to detect dehydration with body area networks? Microsystem technologies are currently stimulating the development and deployment of personal body area networks. These wireless networks provide lifestyle, assisted living, sports or entertainment functions for the user, without visible interference with their active lives. Prevention rather than detection and cure will be the future paradigm. In imec’s imHealthy program, such body area networks (BAN) with several different types of sensors are currently under development: ECG signals, skin conductance, ions in sweat, motion and many more signals can be monitored, recorded and wirelessly transmitted to a hub during longer periods of time. The aim of this thesis work is to study how these sensor networks can be used for detecting dehydratation of persons, this is particularly of interest for sports and elderly people. Dehydration can have various causes: not only serious illnesses (diarrhea, vomiting, excessive consumption of alcoholic beverages…) but also prolonged physical activity with sweating , stress, prolonged exposure to dry air can cause a dehydration that is not readily recognized. Enhancing BAN networks with dehydration detection and timely warning thus is a very worthwhile and challenging feature. This thesis work will start with a study of dehydration detection methods that are compatible with imec’s BAN sensors systems that are under development. Next a monitoring tool for dehydrtation will be developed for these sensors by analyzing sensor readout signals and combining them in a user app that allows warning the user about his dehydration status. Type of project: Internship or thesis project Degree: Master in (Bio)Engineering, majoring in nanotechnology, (bio)electronics Responsible scientists: For further information or for application, please contact Walter De Raedt ([email protected]) and Chris Van Hoof ([email protected]).

Master Thesis/Internship Topics 2013-2014

40

Ionic fluidic study of metallic nanopores Downscaling is a trend not only seen in the field of electronics, but even in the field of fluidics. This has given rise to the field of microfluidics, which allowed the manipulation of very small quantities of reagents, and recently to the field of nanofluidics, where completely new phenomena come into play. Solid-state nanopores, nanometersized holes in a thin synthetic membrane, are a versatile fluidic device for the detection and manipulation of charged biomolecules. An external electric field drives a biomolecule through the nanopore, producing a characteristic transient change in the trans-pore ionic current. This approach can be used for sensitive singlemolecule biosensing platforms, and much current research is directed toward nanopore sequencing of DNA. An understanding of the conductance of a nanopore is the basis for any nanopore experiment. To date, however, models for conductance through metallic nanopores are under developed. In most previous studies of dielectric pores, it was usually assumed that (a) the potential drop occurs predominantly across the pore and (b) the pore has a cylindrical shape. However, in many cases, particularly when the pore is highly charged, the surface conductance significantly contributes to the corresponding potential drop. At the meantime, the specific chemical interactions on metal surfaces are critical but not integrated into the modeling of the conductance. This thesis will focus on a fundamental study of the nanopore fluidics and build the conductance model for metallic nanopores. For this purpose, the size of nanopore, different metal surfaces will be systematically studied. Further surface modification experiments with different electrolyte buffer will be also applied to connect the metallic nanopore with dielectric ones. Modeling of nanopore conductance will be derived to interpret the nanofluidics inside. Type of project: Thesis project Degree: Master in Science or Master in Engineering, majoring in physics, electronics, physical chemistry Responsible scientists: For further information or for application, please contact Yi Li ([email protected]) and Chang Chen ([email protected]).

Exploration of efficient electroporation protocols for intracellular recording of action potentials using configurations of microelectrodes on chip Multi-electrode arrays are an elegant and fast technique to sense electrical activity of in vitro electrogenic cells such as neurons and cardiac cells. Despite the ability to record from many cells at the same time, the signal quality and the resolution of this technique are still not optimal. Recently, imec developed a technique that makes it possible to record intracellular action potentials using on-chip electroporation (Braeken et al., Lab Chip, 2012). Such intracellular signals are 500 times larger in amplitude and preserve the original shape of the action potential, improving the quality of the recording drastically. The project aims to further investigate the principle of electroporation using on-chip electrical stimulation. The student will make use of a novel experimental platform designed for testing different electrode configurations, topologies and materials, such as three-dimensional electrodes, carbon nanotubes, etc. Effects of electroporation protocols will be evaluated using fluorescent imaging techniques and recording of the spontaneous electrical activity of cardiac and neuronal cells using the multi-electrode array platform of imec. Type of project: Internship or thesis project Degree: Master in Science or Master in Engineering, majoring in (bio)electronics, (bio)physics, biomedics, nanotechnology Responsible scientists: For further information or for application, please contact Andim Stassen ([email protected]) and Dries Braeken ([email protected]).

Master Thesis/Internship Topics 2013-2014

41

Characterization of optical waveguides for optogenetic stimulation of in vitro and in vivo neurons Since the first reports in literature only a few years ago, optogenetics is one of the fastest growing and most promising fields in neuroscience. Optogenetic stimulation is based on optical activation or inhibition of neurons that have been genetically modified to express light-sensitive opsins in their membranes. Today, optical stimulation in vivo is mainly performed using bulky optical fibers with limited selectivity. Imec is investigating optical stimulation of cells using a novel type of devices that make use of waveguide technology to guide visible light into in vitro and in vivo probes. By positioning multiple light entry and exit sites we want to ensure selective stimulation of single cells is feasible. The student will be involved in characterizing on-chip waveguides to investigate optical losses in the substrate, the efficiency of coupling of light into and from the substrate, and the efficiency of optogenetic stimulation of single cells in vitro and in vivo. Parameters of efficient stimulation and the effect on single cells will be studied using optical imaging and electrical recording techniques. Type of project: Thesis and/or internship project Degree: Master in Science or Master in Engineering majoring in electronics, physics, biomedics, optics Responsible scientists: For further information or for application, please contact Luis Hoffman ([email protected]) and Dries Braeken ([email protected]).

High-density carbon electrogenic cells

nanotube

electrodes

for

recording

and

stimulating

Electrogenic cell types, such as heart or brain cells, rely on electrical signals to communicate with one another. In order to gain insights in the fundamental processes of brain cell communication, unravel the cause of brain disorders, or validate the effect of certain drugs on heart cells, it is important to record these signals in a minimally invasive and long-term manner. Our imec research group developed a state-of-the-art chip which is smaller than the size of a fingernail, but yet contains tens of thousands of subcellular-sized electrodes, each individually addressable and able to record and stimulate cells on top. Obviously, the quality of the signal depends highly on the properties of the electrode material. Prerequisites are a good biocompatibility and a high recording and stimulation efficacy. Recently, carbon nanomaterials – such as carbon nanotubes – have attracted considerable interest due to their exceptional electronic, thermal and structural properties. Different and independent studies show that the interface created between carbon nanomaterials and the cellular membrane can yield a high-quality electrical coupling. Using a technique called ‘capillary forming’, complex three-dimensional structures such as overhanging wells, inward or outward bending ‘flower petals’ and intricate microhelices can be fabricated, which can dramatically increase the intimate coupling between the cell and the electrode. The student will be involved fabricating and characterizing different flavors of carbon structures using electrochemical, electrophysiological and optical techniques.

Master Thesis/Internship Topics 2013-2014

42

Type of project: Thesis and/or internship project Degree: Master in Science or Master in Engineering majoring in biomedics, biology, nanotechnology, bioelectronics Responsible scientists: For further information or for application, please contact Jordi Cools ([email protected]) and Dries Braeken ([email protected]).

Controlling light-matter interactions with plasmonic nanoantennas Plasmonic nanoantennas are metallic nanoparticles that can be considered as classical oscillators at the nanoscale. They act as antennas, converting electromagnetic waves at optical frequencies into localized fields. As such, they provide an effective way to study light-matter interactions at the nanoscale by coupling photons in and out of nanoscale volumes and manipulate them. Applications of surface plasmon resonances are widespread, nurtured by nanotechnology, and already approaching a level of maturity that gives them a prominent position to contribute to some of today’s most important challenges: energy harvesting, cancer treatment, disease diagnostics, DNA sequencing, and optical computing. In our group we explore plasmonic antennas for their potential use in innovative biomedical technologies. For instance, directional antennas are designed to route specific light colors emitted by luminescent molecules. High quality factor antennas with very high near-field enhancements in combination with a gain medium can even act as plasmonic nanolasers, paving the way towards highly integrated on-chip biological experiments. In this master thesis, the interaction of plane light waves, as well as local quantum emitters, with new plasmonic antenna designs will be studied. The student will gain hands-on experience with sample preparation in the imec cleanroom, scanning electron microscopy (SEM), and optical experiments (in close collaboration with the KU Leuven Department of Physics. The experimental results will be verified and complemented by full-field 3D electromagnetic simulations. Type of project: Thesis project of 1 year Degree: Master in Science or Master in Engineering majoring in physics, electric engineering, nanotechnology Responsible scientists: For further information or for application, please contact Niels Verellen ([email protected]) and Dries Vercruysse ([email protected]).

Master Thesis/Internship Topics 2013-2014

43

Engineering micro-structures for an optimized lens-free image Lens-free imaging has the potential to generate high-resolution microscope images without the need of expensive and bulky optical components. In lens-free imaging the small objects are illuminated with coherent light and the interference pattern of the diffracted light is captured by an image sensor. As these patterns can be mathematically described, the inverse formula can be used to reconstruct the original object from the recorded interference pattern (see figure 1). As such, traditional microscopy is replaced by computational algorithms that allow us to generate microscopic images using a portable, inexpensive device.

Figure 1: recorded interference pattern of a marker (left) as well as the reconstructed image (right)

To further explore the full potential of this technique, the aim of this thesis is to engineer micro-structures whose features are directly visible in the recorded interference pattern, eliminating the need to do full image reconstruction for image region selection. Hereto the student will devise micro-structures whose interference pattern has a minimal footprint and a maximal signal-to-noise ratio. Novel concepts will be proposed and their interference patterns simulated. Finally several micro-structures will be fabricated and tested in real-life working conditions. This project is ideal for master students who want to explore the intricate relationship between concept simulation, device fabrication and experimental validation. Type of project: Internship or thesis with internship project Degree: Master in Engineering or Master in Physics Responsible scientist: For further information or for application, please contact Frederik Colle ([email protected]).

Master Thesis/Internship Topics 2013-2014

44

Measuring electrical properties of cancer cells It has been known that around 90% of cancer death cases are not due to primary cancer, but metastasis, i.e. tumor cells migrate from the primary tumor and reside at other part of the body. Circulating tumor cells (CTCs) are cells shed from primary tumors and circulate in the peripheral blood. CTCs have been known to be one of the most important pathways for cancer metastasis. The identification & isolation of CTCs are an extremely challenging task because of the low abundance (down to 1 CTCs per mL) and high similarity to blood cells. State-of-the-art techniques are suffering from low specificity & efficiency, the loss of cell viability and high subjectivity. This project work aims to characterize the physical properties of cancer cells (various cell lines as model system) in order to distinguish and thus isolate them from blood cells. This non-invasive method may provide cell information without jeopardizing the cell viability, which allows follow-up genetic study on these cells. Two approaches will be combined in this work: electrical cancer characterization by dielectrophoresis and optical characterization by fluorescent staining. For both approaches, early studies have already implied clear difference between cancer cells and blood cells. In the course of this work, an imec proprietary device will be used to capture cells in a microfluidic chip which allows both electrical & optical characterizations for fixed cancer cell and leukocytes. Type of project: Thesis project of 1 year Degree: Master in Science or Master in Engineering majoring in physics, electric engineering, nanotechnology Responsible scientists: For further information or for application, please contact Chengjun Huang ([email protected]) and Chengxun Liu ([email protected]).

Gram staining using spectroscopy Gram staining is a widely used method to differentiate bacteria on the chemical and physical properties of their cell walls into Gram-positive or Gram-negative. Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. A standard procedure typically takes three steps: staining with a water-soluble dye called crystal violet, decolorization, and counterstaining. The gram stain is one of the most frequently used stains in a clinical microbiology laboratory, but as this procedure is time-consuming, a simple spectroscopic method to replace this method would largely be beneficial. Raman scattering is an optical spectroscopy method and allows to differentiate chemical biomolecules based on their vibrational or rotational modes. It has been shown to be allow for differentiation of cells and may allow as well to spectroscopically differentiate bacteria. You will combine state-of-the-art confocal Raman spectroscopy with advanced signal processing using principal component analysis to image and differentiate both gram-positive and –negative bacteria. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in bio-engineering, nanotechnology, (bio)chemistry, biomedics Responsible scientist: For further information or for application, please contact Evelien Mathieu ([email protected]).

Master Thesis/Internship Topics 2013-2014

45

Gold nanostars for imaging and photothermal treatment of cancer Cancer is still one of the most leading death causes in the world and the demand for more precise and sensitive imaging and therapy techniques remains high. In the latest decennium, nanoparticles have been opted as a contrast agent to improve the detection limit for optical tumor imaging or even to treat cancer. During this thesis, gold nanoparticles will be examined as they can be both used for cell therapy upon irradiation and for imaging based on surface enhanced Raman scattering (SERS). More specifically, gold nanostars will be coated with a SERS label and subsequently coupled with biological ligands to target specific receptor molecules on the tumor cells. Using multiple SERS labels, each with a specific spectrum, multiplexing is possible allowing to visualize different cell types or molecules. Besides imaging, the treatment will occur by photothermal therapy since the particles will absorb light at a specific wavelength and convert it into heat. This heat is deadly for tumor cells since they are more temperature sensitive compared to normal cells. The thesis student will be strongly involved in the different aspects of this topic, including the chemical synthesis of nanoparticles, Raman spectrometry, in vitro studies and microscopy techniques. Type of project: Thesis project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in (bio)chemistry, bio-engineering, nanotechnology or related Responsible scientist: For further information or for application, please contact Antoine D’Hollander ([email protected]).

Antibody stabilizers for lateral flow assays Lateral flow immunoassays are especially designed for single use at a point of care/need. The best-known lateral flow system today is the pregnancy test. In all lateral flow systems, antibodies are immobilized on a solid support or on a transducer for selective detection of their analyte. However, when an antibody comes into contact with a solid support, the folding conformation can change to a partially unfolded or totally unfolded state. Unfolded antibodies show a reduced or even a total loss of their activity. Therefore, immobilized antibodies must be stored in an environment beneficial to stabilize their conformation. Furthermore, guaranteed stability of immobilized antibodies on a solid support is an important key to achieve reliability and stable interfaces for lateral flow immunoassay commercialization. This thesis aims to characterize different commercial stabilizers and methods to preserve the 3D conformation of the antibody for application in lateral flow systems. Hereto different characterization methods will be used. This research should lead to robust and reliable biointerfaces for lateral flow detection schemes. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in bio-engineering, (bio)chemistry, biomedicine or related Responsible scientist: For further information or for application, please contact Karolien Jans ([email protected]).

Master Thesis/Internship Topics 2013-2014

46

Multiplex ligation polymerase amplification on chip Since its introduction, the polymerase chain reaction (PCR) has become an indispensable tool in clinical diagnostics. In recent years, significant advancements emerged in the area of miniaturization of PCR using microfabricated structures with clear benefits. Not only the speed and the efficiency of the amplification can be improved, also the assay costs are largely reduced by downscaling due the lower consumption of expensive reagents. A further benefit in developing complete lab-on-a-chip systems is the possibility to integrate both sample preparation and amplification in a single disposable cartridge. At imec, we recently designed and developed a silicon based miniaturized PCR system. This on-chip PCR chamber showed to be very promising, but its use for multiplexing has not been demonstrated. Therefore, the scope of this research topic is to transfer and optimize this 3-step multiplex PCR based reaction, more particularly a multiplex ligation polymerase amplification (MLPA) reaction, for on chip analysis. To make this project a success, a broad interest in molecular biology, chemistry and basic engineering is required. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences of Master in Science or Master in Engineering majoring in bio-engineering, (bio)chemistry, biomedicine or related Responsible scientist: For further information or for application, please contact Tim Stakenborg ([email protected]).

TNFα detection in cell-culture medium of activated cells Cytokines (e.g. IL6, IL10, TNFα and many others) are an important class of secreted proteins that play a key role in the immune response. They are secreted by many cell types like macrophages, monocytes, T-cells, B-cells, etc. This secretion is often in very small amounts with a peak of only a few hours after activation of the cells. In literature, the detection of cytokines is mainly done by RT-PCR or ELISA, which are both sensitive techniques, but they do not allow real-time detection. Therefore, a need remains for real-time detection methods that allow rapid, quantitative, close-to-the-cell (to reduce dispersion effects) cytokine analysis. A type of biosensor that can meet these requirements are silicon waveguide ring resonators. Silicon waveguide ring resonators are based on the total internal reflection properties of silicon. Silicon waveguide ring resonators contain a bus waveguide, for the input of the light, a silicon ring shape close to the bus waveguide and an output waveguide to the detector. When the ring is close enough to the bus waveguide, the light can couple into the ring and positive interference of discrete wavelengths can occur. These wavelengths are dependent on the total length of the ring, but also the refractive index near the ring surface. This property results in a detectable wavelength shift when for example proteins bind to the ring, which makes it ideal for real-time, labelfree sensing. As a proof-of-principle we will make use of the U-937 cell line which is known to secrete elevated levels of TNF-α when stimulated with for example phorbol myristate acetate (PMA). The cells will be trapped in cellular bioreactors near the sensor surface for real-time detection of the secreted TNF-α. These results will be compared to results obtained with the BIAcore tool and Enzyme-Linked Immunosorbent Assay (ELISA). This topic is a collaboration between imec and the MeBIOS group of Jeroen Lammertyn at KULeuven. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in bio-engineering, (bio)chemistry, biomedicine or related Responsible scientist: For further information or for application, please contact Jef Ryken ([email protected]). Master Thesis/Internship Topics 2013-2014

47

Detection of single protein molecules in microwells on a digital lab-on-a-chip for point-of-care diagnostics Detecting low protein concentrations in blood samples has the potential to improve early-stage detection of many diseases. Most immunoassays detect protein concentrations in the range 10-12 M. However, most proteins relevant for early detection in cancer and early stages of infection (f.e. HIV) require detection of protein biomarkers in a much lower concentration range of 10-16 to 10-12 M. The most common assay format for detecting these proteins in serum is ELISA. This thesis will focus on the detection of single protein biomarkers by developing an integrated lab-on-a-chip that allows ELISA to be executed in femtoliter-sized reaction chambers (i.e. digital ELISA). In a first step, sandwich antibody complexes will be formed on microscopic spheres. After this, the immunocomplexes will be labeled with an enzyme-reporter as in standard ELISA tests. When the ratio of proteins to microscopic spheres is very low, as is the case for low protein biomarker concentrations in serum, beads will either carry a single protein in an immunocomplex or none. Next, the captured immunocomplexes will be confined to very small reaction chambers. As such, the fluorophores that are generated by each single immunocomplex are very concentrated, ensuring a high local concentration of fluorescent product that can be detected with standard fluorescence microscopy. This approach relies on the accurate fabrication of femtoliter-sized reaction chambers to confine these fluorophores. In a first phase, a fabrication process will be developed that enables the creation of arrays of hydrophilic microwells surrounded by a hydrophobic material. Therefore, a thin layer of hydrophobic Teflon will be coated on a glass substrate. Subsequently, microwells will be etched through the Teflon layer and the glass substrate, thereby generating large arrays of micron-sized glass wells in a Teflon matrix. In a next phase, this array of microwells will be used for a digital ELISA assay for detecting the protein tumor necrosis factor-α (TNF-α) on a lab-on-a-chip. Microscopic spheres used for capturing TNF-α in serum are loaded inside the microwell arrays by transporting droplets containing these beads over the array by using a digital lab-ona-chip. Wells containing a single TNF-α molecule will be quantified by counting the fluorescent microwells. This topic is a collaboration between the MeBIOS group of Jeroen Lammertyn at KULeuven and imec. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in nanotechnology, (bio)physics, bio-engineering or related Responsible scientist: For further information or for application, please contact Frederik Colle ([email protected]).

Quantitative protein kinetics analysis using a refractometric LSPR sensor with an improved figure of merit Proteins are vital parts of living organisms, and it’s important to explore their structures and functions. The interactions between proteins, from transient, low-affinity to stable, high-affinity, define much of cellular behavior, and analysis of their interaction networks will help to assign functions to uncharacterized proteins. Furthermore, during the development of therapeutics, such as antibodies, molecules are frequently selected based on their binding kinetics and selectivity for a target ligand, as this single parameter is often predictive of activity in in-vitro and in-vivo assays. The standard analysis method, surface plasmon resonance (SPR), suffers from the fact that its decay length is much larger than the protein size and thus might not provide an optimum sensing ability. However, its nanoscale counterpart, localized surface plasmon resonance (LSPR) is very promising to solve this problem. LSPR is a resonantly excited coherent electron oscillation at a metal nanoparticle surface, and its wavelength position is highly sensitive to local refractive index changes within the electromagnetic near-field of the nanoparticles. This effect forms the basis of LSPR biosensors. The electromagnetic field decay length has the same length scale as proteins, making biomolecules an ideal analysis target. In addition, it provides the possibility of miniaturization and multiplexing, as well as the compatibility with microfluidics for point-of-care personalized diagnostics. Master Thesis/Internship Topics 2013-2014

48

At imec, we have recently developed a LSPR sensing platform with the spectral linewidth as narrow as ~10nm, offering a supreme figure of merit to potentially reduce the limit of detection. The thesis student will compare its sensing ability to that of the conventional SPR platform, and take advantage of the sensing system to investigate the protein-protein interactions and their binding/unbinding kinetics in real time. Type of project: Thesis and/or internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in bio-engineering, (bio)chemistry, biomedical or related Responsible scientist: For further information or for application, please contact Jiaqi Li ([email protected]).

High quality-factor resonators in silicon nitride waveguides Dielectric waveguides consisting of a high-index core surrounded by lower-index cladding layers allow low-loss guiding of light. For photonic integrated circuits, the focus still lies on silicon photonic waveguide structures for 1300 and 1550 nm wavelengths. However for several applications in biology and chemistry, waveguides for short wavelength operation are desirable. Silicon nitride is a promising material for optical waveguides due to its low non-linearity and its transparency in the visible and infrared spectrum. Last year, a low-loss silicon nitride waveguide platform was developed. By an extensive materials study in the 200 mm line of imec, the propagation losses were reduced below 0.5 dB/cm at a wavelength of 532 nm while maintaining a low autofluorescence. In the picture, the coupling from a fiber to a 250 nm wide waveguide on chip is shown. For integrated biosensing applications, the development of compact, high-quality factor resonators at visible wavelengths is of paramount importance. In this thesis project, the student will start from the developed silicon nitride waveguide technology and design novel high quality-factor waveguide resonators. Initially, two types of resonators will be considered: linear 1D photonic crystal resonators and ring resonators. The main focus will be on the linear photonic crystal resonators, for which both the Bragg gratings and the resonant cavity will have to be designed and optimized on the working frequency of 532 nm. This will be done by performing FDTD or FEFD simulations, followed by experimental confirmation of the simulated properties on the fabricated samples by means of waveguide transmission spectroscopy. The student will gain hands-on experience with optical experiments. Sample preparation will be handled by the student in the imec III-V cleanroom in cooperation with the daily advisor. The student will obtain experience in optical and electron beam lithography and master various deposition and etching techniques. Further sample characterization will be done by optical microscopy, scanning electron microscopy and waveguide transmission spectroscopy. The candidate should have a strong interest in photonics and nanofabrication. Type of project: Thesis project of 1 year Degree: Master in Science or Master in Engineering majoring in material science, physics, nanotechnology Responsible scientist: For further information or for application, please contact Pieter Neutens ([email protected]).

Master Thesis/Internship Topics 2013-2014

49

Noise characterization and modeling of electrodes for in vivo and in vitro neural recording Imec develops state-of-the-art CMOS-active Si neural probes and multi-electrode arrays (MEAs) for large-scale neural recording. One of the most important sub-components of such devices is the electrode that transduces the neural signals into measurable voltages. In addition to the wanted signal, electrodes (and integrated circuits) also pick-up unwanted noise originating from different sources: thermal, biological, electrode-electrolyte interface, electronic, and crosstalk. Understanding the contribution of these noise sources to the overall recorded neural data is crucial for developing better and smaller electrodes and more efficient algorithms to recover the encoded neural information. In this research project, the student will perform an in-depth study of the non-biological noise recorded with electrodes of different sizes from passive and CMOS-active Si probes and multi-electrode arrays. The student will develop the required setups for accurate measurements of small noise amplitudes. Hands-on experience in building PCBs using discrete components (low-noise amplifiers, R C components, etc.) and good understanding of their properties is a pre-requisite. Moreover, knowledge in handling spectrum/network/impedance analyzers & Matlab is advantageous. The overall goal will be to identify the causal links between electrode noise and intrinsic/extrinsic electrode properties including electrode-electrolyte impedance, area, material roughness, material composition, etc. Type of project: Thesis project of min. 6 months full-time Degree: Master in Electrical Engineering, Master in Material Engineering/Sciences majroing in device physics, electrical engineering, physics, physical chemistry, electrochemistry, material science Responsible scientist: For further information or for application, please contact Andim Stassen ([email protected]) and Carolina Mora Lopez ([email protected]).

Characterization of the light-sensitivity of CMOS-ICs for life science applications For many life sciences applications, monolithic integration of analog CMOS ICs with MEMS, photonics, and microfluidics is essential to enable multimodal, high-performance diagnostic, therapeutic, and scientific instruments. Analog CMOS ICs are required amongst others to amplify and filter small bio-signals, multiplex large sensor arrays, and actuate and manipulate cells or other micro-objects. In most cases, such chips need to be operated under ambient light conditions or may even be exposed to laser light for fluorescence microscopy. On the other hand, Si CMOS is innately sensitive to light (from near IR to near UV) causing leakage currents in the transistors that alter the overall circuit performance. It is hence crucial to properly shield the circuits. In this research project, the student will do an in-depth investigation of the light-sensitivity of implantable CMOS neural probes and multi-electrode arrays for in vitro applications. These two technology platforms have recently been developed at imec. The student will do extensive IC characterization (on wafer and single die level) under various light conditions and, if necessary, develop appropriate experimental setups to study the observed effects in more detail. The student will also explore and identify new solutions for light shielding or sensitivity suppression: deposition of thin metal layers (imec processing), chip/setup packaging, layout techniques, circuit design techniques, etc. Furthermore, electrical modeling of the light effects may serve as an additional tool to further understand the observed phenomena.

Master Thesis/Internship Topics 2013-2014

50

Type of project: Thesis project of min. 6 months full-time Degree: Master in Electrical Engineering, Master in Sciences majoring in electronics, device physics, material science Responsible scientist: For further information or for application, please contact Carolina Mora Lopez ([email protected]) and Luis Hoffmann ([email protected]).

Multimodal integration of EEG and functional Near Infrared Spectroscopy for ambulatory brain imaging Research on low power, portable EEG recording devices have recently gained huge momentum. These devices are already being used for continuous monitoring of brain activity for both therapeutic and neuroscientific research. Active-electrode based, comfortable, gel-free EEG headsets have made it possible to use these in home environment with minimal professional supervision. Near Infrared Spectroscopy (NIRS), a brain imaging technique of growing interest, however, lags far behind while ambulatory monitoring is concerned. It has been recently shown that EEG combined with functional-NIRS (fNIRS) has far greater prospect in decoding brain activity. EEG measures post synaptic potentials associated with neural activation while fNIRS measures local haemodynamic changes associated to the same. These two modalities complement each other in their ability to resolve information about the spatial and temporal characteristics of neural activity. Analog circuits live at the heart of these medical systems, extracting relevant biomedical signals in presence of various unwanted artifacts . As one of the key building blocks of such medical systems, constrains on these analog circuits are strict: Low power dissipation, high signal quality, reliability, and miniature size. Combining EEG and fNIRS in a portable headset requires both electrical and optical monitoring, preferably on the same IC. These battery operated systems have to low power and the two modalities should have minimal interference. The sensor nodes should be optimally placed and proper algorithms need to be developed to extract maximal information on neural activity. The focus of this MS topic will be to first start with literature search of the existing fNIRS system and how they are combined with EEG measuremnt. She/he will next validate the efficacy of EEG+fNIRS with existing EEG headset and off-the-shelf components. The candidate will recognize the key challenges in combining these two modalities and will also be involved in developing algorithms to extract maximal information from this mutimodal system.

Existing custom EEG+fNIRS system used in lab environment.

Future multimodal EEG+fNIRS ambulatory monitoring.

Master Thesis/Internship Topics 2013-2014

system

for

51

Type of project: Thesis project with internship of 6 months Degree: Master in Engineering majoring in electronics Responsible scientist: For further information or for application, please contact Srinjoy Mitra ([email protected]).

Master Thesis/Internship Topics 2013-2014

52

IV.

Imaging Systems Dynamic current steering in active pixel sensors Most CMOS image sensors use ’active pixels’ to reduce the readout noise. Being ‘active’ in this case means they contain a transistor in source-follower operation that acts as a buffer between the sensitive pixel photo-sensitive node and the output line that is shared between all pixels in the same column of the imager array. With ever-increasing imager pixel count, both parasitic resistance and capacitance of these output lines increase, while at the same time higher frame rates require increased sample rates. The settling time of the pixel sourcefollower including all interconnect parasitics becomes the bottleneck for large imagers at high-speed operation. While the standard solution to this problem involves an increase of the operating current, there are alternative options suggested in literature as well as new ideas, that could improve on this speed-power trade-off. In this thesis, the target is to investigate to what extent the speed/power-ratio of this imager readout could be improved; this involves • literature study • quantitative comparison by spectre simulations on the available options for a representative imager • (if possible) a more generic modeling of this trade-off to deduce guidelines for an optimal solution, depending • on the imager parameters Type of project: Thesis project Degree: Master in Engineering majoring in electronics Responsible scientists: For further information or for application, please contact Steven Terryn ([email protected]) and Jonathan Borremans ([email protected]).

Master Thesis/Internship Topics 2013-2014

53

V.

Large Area Flexible Electronics Degradation mechanisms in organic solar cells Organic photovoltaic devices are one of the most promising applications of organic semiconductors. As organic semiconductors can be manufactured by low temperature processes, such as printing from solution based inks, these materials are compatible with flexible plastic substrates resulting in a lightweight, inexpensive and very practical product. Over the last years impressive progress has been achieved in organic photovoltaic device efficiency and promising roll-to-roll compatible deposition techniques have been also reported. This rapid technological development brings applications close-by, and consequently also the importance of device reliability. Cost evaluations suggest that a lifetime of 5-10 years is necessary with current power conversion efficiencies to achieve low prices. Nevertheless, currently only 1 year of outdoor lifetime was reported on polymer solar cells, other studies in accelerated conditions estimated the device lifetime to 2-3 years. Currently, organic solar cells are comprised of a multilayer stack of a transparent anode, an organic or oxide interlayers, a photoactive bulk heterojunction composed at least two organic compounds capped with an evaporated cathode. Reaction with oxygen and humidity as well as light induces degradation both in the volume and at the interfaces of these layers leading to multiple concurrent degradation mechanisms. Therefore discriminating between the parallel mechanisms is one of the biggest challenges in reliability research. The focus of this master thesis/internship lies in the investigation of the degradation of exciton separation, charge transport and charge extraction in organic solar cells. Implementation of new device architectures, complementary electrical measurements and eventually material characterization techniques will assist the distinction between the simultaneously occurring degradation mechanisms. Most of the work will be done in the state-of-the-art organic device processing lab of imec. The student will receive a broad training on full device processing and characterization tools. After a short training period it is expected that the student can work independently and focusing on his/her investigation. This thesis/internship will mostly consist of practical work. Type of project: Internship or thesis project of minimum 6 months Degree: Master in Science or Master in Engineering majoring in physics, material science, nanosciences, electrical engineering Responsible scientist: For further information or for application, please contact Eszter Voroshazi ([email protected]).

Organic photodetectors Organic semiconductors are used in many fields of photonics. Displays fabricated using organic light emitting diodes (OLED) can be found in modern smartphones and tablets, whereas organic solar cells (OPV - organic photovoltaics) are emerging with demonstrated efficiencies above 10%. Organic photodetectors (OPD) are another very interesting domain, with ultrathin active layers (order of tens of nanometers) providing performance comparable to bulk inorganic devices. Thanks to a multitude of possible compounds, parameters such as response spectrum, cut-off wavelength etc. can be easily tuned. Because of very high absorption coefficient and low refractive index, issues such as reflection or crosstalk can be minimized. Another exciting feature is the low processing temperature and thus feasibility of using a flexible foil as substrate, leading to rollable or curved photodetector arrays. The focus of this internship will be optimization of the fabrication process of advanced organic photodetectors and investigation of their performance with respect to given specifications. Active layers will be deposited by spincoating (solution processed polymers) or thermal evaporation (evaporated small molecules).

Master Thesis/Internship Topics 2013-2014

54

The student will be involved in the entire fabrication cycle, performed in the state-of-the-art facilities including imec's dedicated organic line. Initially, the student will receive training on the relevant processing and characterization tools. After a short introduction to the facilities, an independent investigation is expected with the focus on short-term research goals. Type of project: Internship or thesis project of 4 up to 6 months Degree: Master in Science or Master in Engineering majoring in nanotechnology, material sciences or electrical engineering. Responsible scientists: For further information or for application, please contact Pawel Malinowski ([email protected]) and Soeren Steudel ([email protected]).

Contact resistance optimization in organic thin film transistors Flexible electronics have drawn many attentions for its applications in large area electronics, such as flexible display. To realize the complex circuits on foil, high performance thin film transistors (TFTs) with low process temperature are required. Metal oxide n-type transistors have been demonstrated in industry with average mobility around 15 cm2/V∙s for back-plane applications in flexible display and OLED TV. However, there is no ptype TFTs demonstrated with the process temperature lower than 150 ˚C in metal oxide TFTs. Instead, organic TFTs have also been widely studied for its advantages, such as low process temperature and nice p-type TFTs performance. Record high p-type mobility up to 30 cm2/ V∙s has been demonstrated in large area electronic by solution proceed single crystal organic TFTs. Thus OTFTs has its potentials in high performance p-type logic circuits and also CMOS application in cooperation with n-type metal oxide transistors. To realize high performance TFTs in large area electronics, contact resistance of the TFTs is a very important factor that limits the performance of the OTFT circuits. With the improvement in contact resistance in OTFTs, many performance issues would be improved e.g. speed of circuits, noise margin in CMOS logic gates and selfheating induced instability. In the project, you will be part of the transistor team and you will process and characterize the organic thin-film transistors independently with some initial training. You will start with device fabrication by working with vacuum deposition system and photolithography for different process steps. Different device structures would be investigated for the contact resistance analysis. You will electrically characterize the TFTs and interpret the data to define follow-up experiments. The morphologies of the devices maybe characterized by different technologies such as optical microscopy, atomic force microscopy (AFM) and x-ray diffraction (XRD). This project is very practical and process oriented. Fundamental knowledge of TFT device physics is necessary. A good sense of experimental design and discipline to execute the plan are required. Persons with hands-on experience in labs or cleanrooms are preferred. Independent working style and good communication abilities in English are highly appreciated. Type of project: Internship project Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in electrical engineering, material science, chemical engineering Responsible scientist: For further information or for application, please contact Tung-Huei Ke ([email protected]).

Master Thesis/Internship Topics 2013-2014

55

Bias stress stability study of a-IGZO TFTs In recent years, amorphous oxide semiconductors (AOSs) are of great interest for thin-film transistor (TFT) channel layer applications. They have been studied due to their superior characteristics, such as high uniformity, high electron mobility between 10-50 cm2/V‧s, and their fabrication at low temperatures on plastic substrates. These advantages of a-IGZO thin-film transistors are promising for next-generation large & flexible backplanes for displays. Among AOSs, amorphous indium gallium zinc oxide (a-IGZO) is leading the display industry because of its high performance. Issue of bias instability of these TFTs under light & at higher temperature still not completely understood. The semiconductor possesses a high optical band gap and is transparent but the TFTs still exhibit a photo response to visible light when illuminated. Some studies have reported that illumination can enhance the negative gate bias stress effect. However, a study involving the full spectrum of colors and overall gate bias conditions under various temperatures has not yet been conducted on our devices. The objective of the research on this topic is to provide detailed assessments of our a-IGZO TFT’s bias stress instabilities under illumination and at higher temperatures. Positive and negative gate bias stress instabilities with and without light (red, blue & green spectra) exposure together with temperature range between 25oC to 120oC need to be studied extensively. The time dependence behavior of stress and recovery under various stress conditions needs to be established. From the results a conclusion need to be drawn for both positive and negative gate bias stress in relation to device structure, interface & material defects of the TFTs. This activity also includes the measurements of the manufactured devices with various process splits. If time allows, the student will also investigate the devices on the flexible substrates. Type of project: Internship or thesis project of 6 months Degree: Master in Science or Master in Engineering majoring in material physics, electronics, nanotechnology Responsible scientist: For further information or for application, please contact Manoj Nag ([email protected]).

Master Thesis/Internship Topics 2013-2014

56

VI.

Wireless Communication Radio-frequency communication with metal-oxide electronics on plastic In recent years, fast progress was made in the technology of thin-film semiconductor devices based on organic semiconductors (such as pentacene and derivatives) and oxides, such as Indium-Gallium-Zinc-Oxide (GIZO). In particular this latter semiconductor offers over amorphous silicon the advantages of a much higher carrier mobility, of the order of 10 cm2/Vs, and room temperature processing, making it fully compatible with plastic substrates. This new technology opens the way to circuits and systems fabricated directly on flexible plastic foil. RFID transponders and tags are one type of application that will greatly benefit from this opportunity. RFID is an important technology in logistics, to transmit an identification code between a transponder and a reader. The crucial components of a passive RFID tag are the antenna and the rectifier. The antenna must be isotropic and have the largest gain possible, while the rectifier must operate at HF (13.56MHz) or more preferable at UHF (868MHz). In the rectifier, the diodes must follow the high-frequency input signal and provide enough power for the tag circuitry. Large Area Electronics technologies allow strong cost reductions compared to Si chips and simultaneously offer true mechanically flexibility, required for tag integration onto items. The diodes can have mainly two topologies: the Schottky and transistor connected diodes. Transistor-diodes are based on a shorted gate-drain transistor configuration. In this configuration, the gate-drain electrode and the source act as the injector and the blocking electrode, respectively. The main advantage of such topology is the integration with other circuitry, as the same process technology for standard transistors can be used for its fabrication. Their main drawback, on the other hand, is the relatively long minimal channel length that can be achieved with standard photolithographic processes. Schottky diodes offer the possibility of extremely small charge transient time and are normally chosen as rectifying element. However, as GIZO is an amorphous material with a high defect density, it is difficult to achieve high Schottky barriers and low leakage currents. The main task of the student is to investigate the effects of GIZO deposition on the transistor-diode characteristics, in order to achieve high on/off drain currents and high electron mobility, targeting mainly the transistor onset voltage control. This activity includes the fabrication of devices within imec clean room and our laboratories using mainly two deposition techniques: RF sputtering and thermal evaporation. The second step will be to integrate these single devices in a rectifier with integrated capacitances and characterize its frequency response. Initially, the devices will be fabricated on a hard substrate such as silicon, but the final device should be completely realized on a flexible plastic carrier. If time allows, the student will also tackle the Schottky barrier formation on GIZO and its characterization. In order to develop insightful ideas about the diode performance, all experimental work will be followed by analytical and SPICE models. Type of project: Internship or thesis project of 6 months Degree: Master in Science or Master in Engineering majoring in material physics, electronics, nanotechnology Responsible scientist: For further information or for application, please contact Adrian Chasin ([email protected]).

Master Thesis/Internship Topics 2013-2014

57

Algorithm and architecture co-optimizations for cost and power constrained signal processing system Many fundamental innovations in ICT are driven by advanced signal processing systems and their efficient implementations. As an example, wireless baseband signal processing is one of the key enablers for affordable Gbps wireless communications. As one of the key challenges in such innovation, cost and power of signal processing implementations need to be minimized whereas application level requirements are not scarified. To achieve this goal, co-optimizations of the following two will be essential: • Signal processing algorithms that extract useful information from raw data via various mathematical transformations and searching operations. • Signal processing architectures that execute the above mathematical transformations and searching operations. In the proposed thesis, the student will work on concrete cases such as: • MIMO detectors optimized for LTE and LTE-Advanced radio systems • Channelization for software defined radio receivers For each of the topics, the work will consist first of an extensive literature study of the involved algorithms. Next, algorithms will be selected with the help of the experienced imec researchers in the field. Finally, an efficient implementation should be derived. To achieve this, possible algorithm or architecture optimizations will be needed. The student will learn the respective application domain (e.g., MIMO detectors for LTE) as well as embedded software design and computer architectures. As a result, this topic provides a good training for industry-relevant skills as well as innovative algorithms and architectures. Type of project: Internship project of 6 up to 12 months Degree: Master in Electrical Engineering majoring in signal processing, telecommunication, embedded systems Responsible scientist: For further information or for application, please contact Min Li ([email protected]).

Digital assistance and digital frontend for deep submicron analog circuits CMOS is scaling down to deep-submicron technologies (28nm, 22nm, 14nm) pushed by benefits obtained in digital design (speed is increasing and area per function is decreasing). From analog design point of view the benefits of scaling are less clear (parasitics are lower, time resolution is increased but voltage resolution is decreased), but it has to follow digital design. On the other side, modeling of MOS transistor in deep submicron technologies is less accurate. Spread with respect to nominal corner is larger in deep- submicron technologies. There is a clear trend to correct (or assist) functions implemented in analog domain in the digital domain. The master student may work on the following aspects: • Calibration, compensation and healing algorithms and digital implementations for practical deep submicron analog circuits • Power and performance optimized controlling algorithms and digital implementations for practical deep submicron analog circuits This topic will offer an exciting challenge on the boundaries of analog circuits, signal processing and digital circuits. Type of project: Internship project of 6 up to 12 months Degree: Master in Electrical Engineering majoring in signal processing, telecommunication, circuit design Responsible scientists: For further information or for application, please contact Min Li ([email protected]) and Vojkan Vidojkovic ([email protected]). Master Thesis/Internship Topics 2013-2014

58

Functional error mitigation schemes for latency-constrained wireless systems Many streaming applications, exhibit not only throughput requirements but also the combination with hard latency constraints. This is the case for wireless baseband applications, especially when they are oriented to high throughput communications. Typical examples of this are connectivity standards like WLAN 11n/ac or 11ad as well as cellular standards like Long-Term Evolution or LTE Cat5/6/7. Functional reliability guarantees should hence be provided, which are not just quality-of-service trade-off based but that are hard requirements on the system implementation. Today's reliability mitigation approaches cannot meet these requirements except with a very large hardware (area) cost, as in triple redundancy methods. Alternatively, EPFL and imec have been working on a costeffective approach [1] that is based on smart checkpointing and a heavily optimized run-time manager that takes care of hard throughput guarantees with minimal overhead. In this project we want to extend the existing approach to deal also with the highly-challenging above mentioned combination of throughput and latency requirements. In particular, we will map functional reliability mitigation technique(s) on a representative HW platform at imec, which runs realistic wireless driver(s). This primarily requires an initial understanding of the HW platform, SW driver, and the mitigation technique. Then, we will develop a customized optimal mapping of the mitigation technique [1] on the target platform. This may cause an extension of the originally developed mitigation technique in order to meet the prospective challenges in the target platform constraints and requirements. The student will optimize the mapping of the mitigation technique on the target platform. The student will: 1. Prestudy together with EPFL PhD on the current functional reliability mitigation approach [1]. 2. Study the detailed requirements of realistic wireless applications at omec. 3. Optimize the existing mitigation technique and develop and extension to it based on the platform requirements, in a cooperation between EPFL and imec researchers. 4. Apply the extended technique on the imec benchmark to demonstrate the feasibility and the cost advantages compared to the standard hardware ECC (Error correction) solutions. Requirements 1. Good knowledge of C programming. 2. Basics of wireless baseband applications. 3. Interest in mapping applications to architecture platforms. [1] M. M. Sabry, D. Atienza, and F. Catthoor “A Hybrid HW-SW Approach for Intermittent Error Mitigation in Streaming-Based Embedded Systems” In proceedings of DATE 2012. Type of project: Internship project of 6 up to 9 months from mid August or begin September’13 onwards. Degree: Master degree Responsible scientists: For further information or for application, please contact Francky Catthoor ([email protected]).

Master Thesis/Internship Topics 2013-2014

59

VII.

Energy Hydrogen generation through water photoelectrolysis using semiconductor photoanodes Hydrogen receives tremendous attention as a renewable energy source in the future. Water photoelectrolysis is a direct approach to generate hydrogen using solar energy. Due to adjustable bandgap and proper band edge potential, III-Nitride semiconductor is considered as a promising material in photoelectrolysis. In this project, some important challenges in III-Nitride system will be focused. To enhance the photocarrier separation and migration, metal particles/films are introduced at sample surface to manipulate surface potential and band bending. The corresponding changes in photocatalytic property will also be investigated. Moreover, sample corrosion during photoelectrolysis is commonly observed. A thin metal oxide layer by atomic layer deposition will be employed to separate the electrode from direct contact to solution during photoelectrolysis. Third, chemical reactive sites play an essential role in carrier transfer to solution. Nanostructuring treatment will be applied to the sample surface for a larger surface area. In this project, the student will be responsible for device fabrication and (photo)electrochemical characterization. The device fabrication part includes different metal deposition, annealing and electrode preparation. The experiments include mainly cyclic voltammetry, chronometry and impedance spectroscopy. Type of project: Thesis or internship project of 6 months, preferably starting between May-June 2013. Degree: Master in Science or Master in Engineering majoring in (electro)chemistry, material science, physics, electronics Responsible scientists: For further information or for application, please contact Peter Tseng ([email protected]) and Ruben Lieten ([email protected]).

Electrical characterisation of amorphous Si layers for solar cell applications Amorphous silicon layers offer several advantages for the production of cost-effective, high efficiency Si solar cells. These advantages stem from the presence of an ultra-thin intrinsic amorphous silicon passivation layer between the doped (amorphous silicon) emitter region and the crystalline silicon base material. The presence of this heterojunction, where the interface defect density can be very low, and with favourable band alignment to repel minority carriers, enables achieving very high open circuit voltage values, and resulting high efficiency cells. To maximize the solar cell efficiency, minimizing the resistive losses in the electrical contact to a doped amorphous silicon layer is also critical. Previous works have shown the significance of the amorphous layer processing conditions on the layers resistivity, and its link to the contact resistance. The presence of an heterojunction requires careful passivation, and an analysis of this passivation layer/doped layer stack is one of the aims of this proposed research. It is foreseen that capacitance-voltage and conductance measurements of a-Si layers, with varying layer thickness, processing conditions, substrate doping etc, will form the basis for this research. Analysis of the measured data can yield information on defect densities in the layers, the energy of these defects in the silicon bandgap. The impact of processing on these parameters will be examined. It is envisaged that this work will focus on electrical characterisation of amorphous silicon layers, and interpretation of the data generated from this analysis. We are looking for a student who has experience in electrical characterisation, preferably capacitance-voltage/ conductance-voltage measurements.

Master Thesis/Internship Topics 2013-2014

60

Type of project: Internship project (of 8 months preferably) Degree: Master in Physics or Master in Engineering majoring in physics, electronic engineering Responsible scientist: For further information or for application, please contact Barry O’Sullivan ([email protected]).

Dielectric ablation by laser processing for photovoltaic applications Laser processing has long been used in photovoltaic solar cell manufacture, but recently it is receiving considerably research interest as a method of rapidly and accurately ablating dielectric layers. This enables a pattern to be defined on a solar cell, in an industrially viable process. In this application, a laser process is used to ablate thin SiO2 layers, used as passivation layers in interdigitated back contact solar cells. In the envisaged process flow, it is foreseen that two ablation steps will be required: firstly to define the n+ and p+ doped regions, and secondly to open the points at which the metal layer contacts these doped layers. This work will involve optimising the laser parameters for such applications, and in designs that correlate with either lithography or screen printing masks. As the ablation process itself involves melting of the underlying silicon, which then expands, and ruptures the SiO2 layer above, there is a risk of surface damage of the remaining silicon. However, by performing chemical treatments on this layer, this damage can be minimized. The aim of this project is to develop suitable laser and subsequent chemical treatment combinations to accurately define the required pattern, and avoid degradation of the underlying layers. Type of project: Internship project of minimum 8 months Degree: Master in Physics or Master in Engineering majoring in physics, chemistry, electronic engineering Responsible scientist: For further information or for application, please contact Barry O’Sullivan ([email protected]).

Development of assembly technology for next-generation c-Si PV modules Photovoltaics have always been mainly (over 80%) based on c-Si solar cells, and this will continue to be the case for the foreseeable future. The module technology used for connecting and protecting these cells likewise has been established already quite some time ago and has proven its worth with operational lifetimes exceeding 20 years in harsh outdoor conditions. However, cost (and other) considerations are continuously pushing technology development towards higher performance, longer lifetimes and cheaper materials and processing. But while this pressure has in the past mostly been focused on cell development, also module technology is now being pushed towards such improvements. With this in mind, imec is developing module concepts (i-module and i2-module), that provide an alternative for the currently standard technology for making modules. The standard technology is based on stringing of cells for electrical interconnection and subsequent EVA lamination for encapsulation of these strings between a (transparent) front- and backsheet, whereas the i-module targets bonding of the cells to the superstrate using a silicone adhesive, early on in the process, and then further build up the module. In all of the proposed module concepts, silicone bonding plays a crucial role, and many aspects of it are still under investigation. In this topic, the idea is to focus on this silicone bonding technology. In first instance we want to develop and characterize it further, while at the same time implementing and evaluating it in the different module concepts.

Master Thesis/Internship Topics 2013-2014

61

Later on, we would like to investigate the possibilities and limitations of the technology to expand the module concepts further and test a few ideas we have in mind (intermediate concepts, additional components, alternative module materials). Of course, even though the focus is on the silicone bonding technology, also its impact on previous and subsequent processing has to be taken into account, and therefore close interaction with students and other people working in those fields is needed. Type of project: Thesis or internship project of minimum 9 months Degree: Master in Industrial Sciences or Master in Engineering majoring in material science, physics, electronics Responsible scientist: For further information or for application, please contact Jonathan Govaerts ([email protected]).

Optimization of the bonding and detachment process of epitaxial silicon foils for application in thin-film crystalline silicon solar cells To limit the use of ultra-pure silicon in the fabrication of thin-film crystalline silicon solar cells, a procedure to create foils is established at imec. This concept consists of the formation of an epitaxial layer on top of a weak porous silicon layer. After this epitaxial layer underwent the front-side solar cell processing, the cells are separated from each other by laser grooving. At the same time, the laser groove is used to be able to detach a specific part of the epitaxial foil from its parent substrate. Afterwards, it is bonded to a quartz plate by a permanent silicone bond. Many different separation processes (like heat treatment, ultrasonic waves, mechanical force, …) can be used to detach the epitaxial foils from the parent substrate. The object of this research topic is to help us screening the possible separation processes to obtain tiles of silicon on a quartz plate. In a second step optimize the most promising candidate in order to improve the yield of this specific process sequence. This will be done by starting from a currently used process sequence that is used to glue a single foil of silicon onto a quartz plate. However, many additional problems (like formation of micro-cracks on the edges, stress and bowing of the foils during and after gluing, …), occur when tiles of 40µm-thick foils need to be glued to a single quartz plate in an accurate manner. Your task will be to investigate the impact of various parameters on the detachment and bonding yield of those silicon films, identify which ones are essential for our process, and gain control on them. This work will be experimental and will take place in a lab and cleanroom environment. For this application you should therefore have a hands-on attitude. You should be able to work accurate and consistent. Since you will depend also on other persons for processing, you should be a real team player. A background in engineering is preferred.

Bonded epitaxial foil of 40µm-thick onto a quartz substrate

Type of project: Thesis or internship project of minimum 9 months, starting September 2013 Degree: Master in Science or Master in Engineering majoring in material science, physics, chemistry Responsible scientist: For further information or for application, please contact Kris Van Nieuwenhuysen ([email protected]). Master Thesis/Internship Topics 2013-2014

62

Development and validation of an optical model for PV modules It is well known that photovoltaic (PV) modules have a lower performance in the field than measured directly after production under “Standard Test Conditions”. The resulting energy yield losses can be mainly attributed to: • reduced illumination resulting in lower current • increased cell temperature during operation resulting in lower voltage (not compensated by slightly higher current) nNon-uniform illumination conditions (shading, clouds,...) leading to current mismatch in serially connected cells • performance degradation over time In order to predict either the energy production of PV modules or to identify energy yield loss within the module, it is necessary to develop a suitable model to calculate the optical absorption, cell temperature and electrical output as a function of ambient temperature, wind direction and total irradiance. With this in mind, imec develops a model for module that incorporates optical, thermal and electrical properties and behavior and is suitable for simulating non-steady-state and non-uniform illumination conditions. Thermal and electrical properties of PV modules were investigated and have been correctly integrated into the opto-electro-thermal model. However, more insight into optical properties of PV module is needed to improve the accuracy of the energy yield simulations. In the first place, the goals of this topic is to characterize the optical properties of PV modules and to develop an optical model suitable to simulate non-steady-state and non-uniform illumination conditions. The optical model has to fit into the opto-electro-thermal model, therefore close interaction with students and other people working in those fields is needed. Later on, we would like to validate the opto-(electro-thermal) PV module model. Type of project: Thesis or internship project of minimum 9 months Degree: Master in Industrial Sciences or Master in Engineering majoring in material science, physics (optics) Responsible scientists: For further information or for application, please contact Hans Goverde ([email protected]) and Ounsi El Daif ([email protected]).

Degradation mechanisms in organic solar cells Organic photovoltaic devices are one of the most promising applications of organic semiconductors. As organic semiconductors can be manufactured by low temperature processes, such as printing from solution based inks, these materials are compatible with flexible plastic substrates resulting in a lightweight, inexpensive and very practical product. Over the last years impressive progress has been achieved in organic photovoltaic device efficiency and promising roll-to-roll compatible deposition techniques have been also reported. This rapid technological development brings applications close-by, and consequently also the importance of device reliability. Cost evaluations suggest that a lifetime of 5-10 years is necessary with current power conversion efficiencies to achieve low prices. Nevertheless, currently only 1 year of outdoor lifetime was reported on polymer solar cells, other studies in accelerated conditions estimated the device lifetime to 2-3 years. Currently, organic solar cells are comprised of a multilayer stack of a transparent anode, an organic or oxide interlayers, a photoactive bulk heterojunction composed at least two organic compounds capped with an evaporated cathode. Reaction with oxygen and humidity as well as light induces degradation both in the volume and at the interfaces of these layers leading to multiple concurrent degradation mechanisms. Therefore discriminating between the parallel mechanisms is one of the biggest challenges in reliability research. The focus of this master thesis/internship lies in the investigation of the degradation of exciton separation, charge transport and charge extraction in organic solar cells. Implementation of new device architectures, complementary electrical measurements and eventually material characterization techniques will assist the distinction between the simultaneously occurring degradation mechanisms. Master Thesis/Internship Topics 2013-2014

63

Most of the work will be done in the state-of-the-art organic device processing lab of imec. The student will receive a broad training on full device processing and characterization tools. After a short training period it is expected that the student can work independently and focusing on his/her investigation. This thesis/internship will mostly consist of practical work. Type of project: Internship or thesis project of minimum 6 months Degree: Master in Science or Master in Engineering majoring in physics, material science, nanosciences, electrical engineering Responsible scientist: For further information or for application, please contact Eszter Voroshazi ([email protected]).

Large area coating of organic photovoltaic modules Organic photovoltaics (OPV) are evolving within the field of renewable energy production from lab-scale devices to industrial-scale modules. OPVs differ from traditional silicon based solar cells in their carbon-based light absorbing material. These organic materials are processable in two manners: vacuum evaporation and solution based deposition. Roll-to-roll compatible processing techniques like spray coating and slot-die coating can be used within the solution processed domain to achieve high-throughput production. This, in combination with the low process temperature required, creates opportunities for processing on many types of substrates, including foils or textile. To enable the transition from lab- to industrial- scale production, patternable coating techniques need to be investigated. Recent OPV developments have focused on efficiency enhancement on single cell levels, with active areas below 1 cm². However, due to the inherently low mobility’s of organic materials, the upscaling poses serious problems. One of the more promising approaches for upscaling connects several smaller cells together in a monolithic series connection. In order to create the interconnection of these subcells, several patterning steps are normally required. Recently established in-house patterning techniques have enabled the reduction in material wastage and the number of patterning steps required, but modifies the coating characteristics. In this project, the researcher will investigate scalable coating techniques for large area OPV production and the effects of patterning methods on the coatings. Initially, conventional sheet-based processing methodologies will be used, followed by the transferal of the process to roll-to-roll applicable tools. Once coating and patterning have been developed, complete OPV modules will be fabricated, and their performance will be benchmarked against more conventional fabrication techniques. Type of project: Internship or thesis project of minimum 6 months Degree: Master in Industrial Engineering or Master in Science or Master in Engineering majoring in material science, nanotechnology, electrical engineering, chemical engineering, physics, chemistry Responsible scientist: For further information or for application, please contact Jeffrey Tait ([email protected]).

Master Thesis/Internship Topics 2013-2014

64

2D and 3D modeling of high efficiency back junction solar cells This project is part of a further collaboration between MCA and the PV department, for the development of 2D and 3D modeling of high efficiency back junction solar cells (IBC, Interdigitized Back Contact). IBC solar cells stand as the workhorse of imec’s PV technology vehicle, aiming in high efficiency values (above 22%) and simplification of the fabrication process in order to reduce the associated costs. The overall operation of the IBC cells is governed by the combination of a large number of fabrication features and parameters (i.e. doping, passivation, antireflection coating, contact placement, etc.). In order to maximize the electrical output of the cell, it is necessary to optimize both its optical and electrical properties so as to achieve high optical absorption and efficient trapping of the photogenerated electron-hole pairs. In this respect, the ability to model the overall cell operation is of paramount importance, as it offers in – depth understanding of the effect of each parameter / feature, and most importantly, a cost effective test vehicle for the optimization of the cell performance. In this direction, imec has already developed both 2D and 3D modeling platforms for the cell simulation, which are based both on Process and Device simulation tools. At this point, we are in the final stage of the development and evaluation of these platforms, and we are focusing on the optimization of the Device modeling (optical and electrical). In particular, we are using several tools from Synopsys (SProcess, SDevice, SDE, Sentaurus Workbench etc.) The main work of this project will be the optimization of the device simulations, first by calibrating cells with simpler geometries and then, the most updated cell types. One additional goal is the link of Process simulation results with the observed device behavior of solar cells that have been fabricated by means of ion implantation. Both topics are in close conjunction with current research activities on modeling, within MCA. The student will work on close collaboration with researchers both from MCA and PV. Depending on the overall progress of the work, he might have to focus more either to optical or the electrical aspect of the modeling. Type of project: Internship project of 6 months Degree: Master in Science or Master in Engineering majoring in physics, electrical engineering, material science Responsible scientists: For further information or for application, please contact Pierre Eyben ([email protected]) and Antonios Florakis ([email protected]).

Photonic nanostructures for light management in novel thin silicon solar cells and modules Context Silicon based solar photovoltaic cells represent more than 90% of the photovoltaic panels presently sold in the world; silicon is one of the most abundant materials on earth. In such cells, more than 1/3 of the cost is due to the silicon itself. Indeed, its purification and crystallisation have an important energetic and economical cost. This is why the photovoltaic research community is presently looking for ways to have solar cell structures based on thinner and thinner silicon layers. There are nevertheless limitations, existing for thick cells and becoming crucial for thin cells: the thinner the material, the lower its light absorption, in particular at long wavelengths (near infrared), due to the low absorption of Silicon. Thus, in order to keep the light absorption high, it is necessary to find light scattering and trapping techniques inside the absorbing silicon layer. Imecframe Imec is developing novel approaches to decrease the cost of silicon solar cells, including going to thinner silicon layers (40 to one micron). For such thin cells, the regular light scattering approach used for today’s thick cells (> 150 µm) by texturisation of the silicon surface) will not be sufficiently effective anymore. We propose therefore to develop light scattering and light trapping techniques to compensate for these losses.

Master Thesis/Internship Topics 2013-2014

65

This means concretely: Understanding the optical losses of such structures thanks to home-made optical simulations. (Simulation tool: CAMFR based on Python, possibly Lumerical) as well as various optical characterisation techniques. Exploring schemes to enhance the light trapping in order to enhance absorption, while keeping good electrical properties. For this 2nd point the imec Photovoltaics group is exploring several approaches: • Nanopatterned diffractive structures: we are developing nanopatterning techniques based on novel lithography techniques: nanoimprint lithography, hole-mask colloidal lithography (pseudo-random) and plasma or solution-based etching techniques, allowing to strongly modify the optical properties of a solar cell stack. • Dielectric Bragg reflector that increase the reflection to almost 100 % in the near-IR. • Metallic or dielectric nanoparticles to scatter light into the layers. Internship description In this frame, it is proposed to interns (between 3rd and 5th year of Master or equivalent) to participate to the numerical modelling of solar cells with and without light-management features, as well as to some aspects of the experimental part, in particular nanoimprint lithography and solar cell characterisation. Type of work: experimental and simulations Type of project: Thesis or internship project Degree: Master in Science or Master in Engineering majoring in physics, electrical engineering, material science, chemistry Responsible scientist: For further information or for application please contact Ounsi El Daif ([email protected]).

Master Thesis/Internship Topics 2013-2014

66

VIII.

Sensor Systems for Industrial Applications Opto-acoustic micro-resonator for sensing applications In the past decades, Micro-ElectroMechanical resonators made their way in a vast amount of applications. They are used nowadays as clocks and timing devices, inertial sensors, gas sensors, energy harvesters, ... The vast majority of these resonators rely on electrostatic, piezoelectric, thermal or piezoresistive transduction mechanisms for their function. Indeed, these mechanisms are relatively easily implemented in typical microelectronic platforms. The development of photonic platforms, like the ones available at imec, allow considering to use optical interactions, e.g. radiation pressure, as transduction mechanisms. Optical forces are well known for example in bio- or life science contexts where optical tweezers have been demonstrated for a long time. In this project we will investigate the possibilities offered by optical (hyper)sensing and actuation to define opto-acoustic resonators for applications in gas sensing. To be more specific, the candidate will have to design and characterize novel types of opto-acoustic resonators with enhanced robustness, in one of the photonic platforms from imec.

Optical and acoustic ring resonators to be combined for sensing applications

For this purpose, the student will 1. design and model the device analytically and numerically in FEM packages (COMSOL or ANSYS) for which previous experience is wished for but definitely not required 2. lay-out the structures to make these processable 3. fully characterize the device (electrically, optically, acoustically) 4. use the processed devices as sensor or propose an enhanced design improving on the simulated sensing performance of the first one Through this work, the student will learn about state-of-the-art optical sensing of acoustic waves while enhancing his/her engineering skills and learning simulation tools and characterization facilities. Type of project: Thesis project Degree: Master in Science or Master in Engineering majoring in physics, electronics Responsible scientists: For further information or for application, please contact Bruno Figeys ([email protected]) and Xavier Rottenberg (Xavier.Rottenberg.imec.be).

Master Thesis/Internship Topics 2013-2014

67

MEMS-based compass: optimization of magnetometers enabled by MEMS resonators MEMS-based inertial measurement units (IMUs) have gained the status of mainstream commodities for consumer electronics in the past years and find use in guidance, navigation, attitude control, smart metering, etc.. From the simple 1-axis accelerometer, IMUs have evolved to 3 degrees-of-freedom (DOFs) acceleration sensing and eventually to 6DOFs modules, including angular rate sensors. In particular, the synergy of multi-DOF inertial sensors turned out to be key in improving the navigation capabilities of inertial modules. This trend of adding more functionality to existing units goes on. On-chip magnetometer, barometer, thermometer, electronic nose and clocks, are seen as further improvements of current IMUs, but moreover to enable novel smart multi-sensor units. The goal of this master thesis is to characterize and compare the performance of different MEMS resonators fabricated at imec in the Poly-SiGe MEMS platform that were designed to be used in magnetometers for compass applications. You will further build a magnetometer system around at least one of these resonators selected for his promising capabilities. Different standard and novel types of resonant MEMS devices have been designed and fabricated for compass applications. One of these, the Xylophone Bar Magnetometer (XBM), is shown in the figure below. It consists of a free-free beam supported at the nodal points of its fundamental transverse mode of vibration. For its function, it is excited via its nodal supports with a sinusoidal current at its natural vibration frequency. In the presence of an external B, this current results in a sinusoidal Lorentz force (F) that puts the XBM in vibration. The vibrations amplitude, in direct relation with the magnetic field intensity, is capacitively measured through a set of electrodes placed under the beam.

Microphotograph of a Xylophone Bar Magnetometer (XBM) fabricated in Poly-SiGe MEMS technology at imec

For this thesis, you will have to: - understand the working principle of each type of MEMS magnetometer and derive simple models for each of these, i.e. analytical, numerical (COMSOL) and equivalent circuit, - perform experimental characterization of produced devices, first with a Laser Doppler Vibrometer (LDV) to observe vibration modes and identify the working frequencies, then with a 2-port network analyzer to assess the electrical response of the resonators, - update the model with the experimental data, - compare the performance of each type of magnetometer, - breadboard a dedicated circuit around a selected resonator to allow an integrated magnetic field measurement. Type of project: Thesis project Degree: Master in Science or Master in Engineering majoring in physics, electronics Responsible scientists: For further information or for application, please contact Veronique Rochus ([email protected]) and Xavier Rottenberg (Xavier.Rottenberg.imec.be). Master Thesis/Internship Topics 2013-2014

68

Cost-effective photonic sensor for point-of-care medical diagnostics In the past decade, physicians’ insight in the biomolecular causes of several diseases has grown tremendously. Although this knowledge provides a very rich basis for fast and accurate medical diagnoses, it is currently only applied at limited scale due to a lack of efficient methods to measure biologically relevant molecules in a urine or blood sample from a patient. Where nowadays an analysis can take weeks, and can only be done in big clinical laboratories, one ideally would want a system that can perform molecular diagnostics in real-time at the point-ofcare, e.g. at the patient’s bed-side. Integrated photonic sensors lately receive a lot of attention for this type of applications. Indeed, in analogy to electronic integrated circuits, photonic integrated circuits combine and miniaturize optical functions, such as (laser) sources, detectors and filters, on a chip. Such photonic integrated circuits, mass manufactured at high quality using optical lithography and etching, are already commonly applied in optical fiber communication networks that form the basis of the internet. Imec has developed a state-of-the-art technology in its CMOS-fab that enables the fabrication of integrated photonic chips on a large scale in a cost-effective way. Using this technology, sensors for biomedical applications have already been developed. They consist of on-chip waveguide interferometers or resonators. When biochemical receptor molecules placed on the waveguide walls selectively capture target molecules, a phase shift is induced in the light propagating through the waveguide. This phase shift then results in a measurable output change of the interferometer or resonator. Using this technique, sensor chips with hundreds of different sensors have been demonstrated. However, although the sensor chips can be fabricated cost-effectively, the interface instrumentation, that interrogates the chip, is still prohibitively expensive (in the order of 100 000 euro) for application at the bed-side of the patient. Therefore, there is a strong drive towards developing low cost interrogation instrumentation. Recent progress in imec’s technology enables just that, and now you have the opportunity to contribute to the development of a new prototype instrument! The goal is straightforward, but challenging at the same time: develop a photonic chip and instrument that allows biomolecular measurements, but at a fraction of the instrument cost. Your challenges: 1. design a cost-effective interrogation scheme 2. design your own photonic chip 3. build a prototype instrument 4. characterize your photonic chip 5. perform a proof-of-concept measurement of your chip with the instrument you built Your gains: 1. work in a multidisciplinary team 2. acquire hands-on experience with optical components 3. learn about on-chip photonics, such as waveguiding and interference 4. learn lithographic mask design for a CMOS-fab

Type of project: Thesis project Degree: Master in Engineering majoring in electronics, photonics, applied physics or related Responsible scientist: For further information or for application, please contact Tom Claes ([email protected]).

Master Thesis/Internship Topics 2013-2014

69

IX.

Microelectronics Design Visualisatie van DfX analyse feedback in een elektronisch ontwerp Onder Design-for-X worden alle ontwerpaspecten van een elektronisch product verstaan die buiten het zuiver elektrische ontwerp vallen. Hieronder vallen zaken zoals de maakbaarheid van het product (DfManufacturing), de bedrijfszekerheid (DfReliability), de testbaarheid (DfTest), enz. Het eindwerk kadert binnen de onderzoeksactiviteiten van het EDM programma van imec (www.edmp.be) dat zich richt op het uitwerken van ontwerp- en kwalificatierichtlijnen voor Printed Board Assemblies (PBA) voor de Vlaamse elektronica-industrie en elektronica-implementatoren. Binnen dit programma is er een PBA simulatie tool ontwikkeld (Visual studio 2010 – visual basic & excel integratie) die analyses doet op elektronische ontwerpen. De resultaten van deze tool worden nu in Excel voorgesteld aan de gebruikers. Het eindwerk richt zich op het grafisch visualiseren van de gerichte analyse feedback naar de gebruiker: • Studie van de gebruikte CAD formaten en selectie van een formaat. Dit formaat wordt nadien gebruikt om data van een elektronisch ontwerp in te lezen en te visualiseren. • Importeren van de CAD Data: extraheren van gegevens en opslaan in de gebruikte datastructuur van de PBA simulatie tool. • Grafische visualisatie van deze CAD data. • Visualisatie van diverse feedback gegevens − testanalyses: defect rates, meest falende componenten − betrouwbaarheidsgegevens − thermische analyses − mechanische vibratie analyses • Optioneel: 3D voorstelling van de CAD gegevens. • Ontwerp van een applicatie en/of custom control in MS Visual Basic 2010. Project: Thesis project Degree: Master in Industrial Sciences majoring in electronics-ICT Responsible scientist: For further information or for application, please contact Wesley Van Meensel ([email protected]).

Design van een 3.3V digitale standaardcelbibliotheek in UMC 180 nm technologie voor ruimtetoepassingen Imec ontwikkelt in samenwerking met het Europese Ruimteagentschap ESA celbibliotheken die toelaten stralingstolerante chips te ontwerpen in commerciële technologieën. Deze aanpak biedt als voordeel dat er niet gekozen moet worden voor dure stralingsharde processen met beperkte functionele flexibiliteit in het analoog domein. Momenteel ondersteunt imec een 180 nm bibliotheek in UMC technologie. We noemen die stralingstolerante bibliotheken DARE, een acroniem voor Design Against Radiation Effects. De bibliotheken worden gratis ter beschikking gesteld van de Europese ruimtevaartindustrie. Op dit moment wordt er actief gebruik gemaakt van DARE om ASICs (Application Specific Integrated Circuits) voor kritische ruimtetoepassingen te ontwikkelen. Het uitdoven van oudere chipproductieprocessen leidt tot een grotere vraag naar cel bibliotheken die enkel met 3.3V voeding werken. Dit eindwerk heeft als doel een functioneel volledige stralingsharde standaard cel bibliotheek te maken om de nood vanuit de ruimtevaartindustrie te beantwoorden. Via dit ontwerpeindwerk worden de studenten vertrouwd met het concept van stralingsharde elektronica, vanuit zowel digitaal als analoog standpunt. Eerst krijgen ze inzicht in de werking en de transistorimplementatie van de Master Thesis/Internship Topics 2013-2014

70

essentiële basisblokken van digitaal chipontwerp (latch, flipflop, adder, exor...). De extreme condities (temperatuur, straling...) in de ruimte vragen een grondige verificatie van elke basiscel. Hiervoor doen we beroep op gespecialiseerde CAD software, waarmee de studenten stap voor stap vertrouwd worden gemaakt. De figuur toont de verschillende ontwerpaspecten van een typisch basisblok. Elk basisblok wordt op transistorniveau uitvoerig gesimuleerd om de performantie onder veranderende produktie- en omgevingsfactoren te analyseren en bij te sturen. Het gefinaliseerde ontwerp wordt daarna volledig uitgetekend in een ‘layout’ en met extractie- en karakterisatiesoftware worden de nodige formaten gegenereerd om de cel voor te stellen in verschillende stappen van het digitale ontwerpproces (synthese, timing analyise, layout...) . Dit eindwerk vereist toegang tot Cadence ontwerptools en de Calibre verificatie tools. Dit kan gebeuren door regelmatig naar imec (Leuven) te komen of door remote in te loggen op het imec-netwerk. Een constante communicatie met de begeleider op imec is vereist. Software tools (state-of-the-art): • Cadence: Virtuoso, Composer, Analog Design Environment, Ocean, Spectre simulator • Metor Graphics: Calibre (DRC, LVS, LPE) • Linux/Unix Tijdsindeling: 10% technologie, 50% ontwerp/simulatie, 30% layout., 10% scripting

Project: Thesis project Degree: Master in Industrial Sciences majoring in (micro)electronics Responsible scientist: For further information or for application, please contact Geert Thys ([email protected]).

Master Thesis/Internship Topics 2013-2014

71

Ontwerp van radiatie-tolerante flipflopsvoor imec’s DARE bibliotheken Via dit ontwerpeindwerk worden studenten vertrouwd met CMOS ontwerp op transistor niveau. Concreet woden radiatie-tolerante flipflops ontworpen. Imec ontwikkelt in samenwerking met de Europese ruimtevaartorganisatie (ESA) standaardcelbibliotheken die gebruikt worden in radiatie-tolerante chips. In de ruimte zijn chips onderhevig aan verschillende soorten hoogenergetische straling die hun oorsprong vinden in de kosmische straling. Het betreft deeltjes (alfa, ionen, neutronen etc.); niet elektromagnetische straling. Momenteel ondersteunt imec celbibliotheken in 180 nm CMOS technologie van UMC (Taiwan). We noemen die bibliotheken DARE, een acroniem voor Design Against Radiation Effects. De bibliotheken staan ter beschikking van de Europese ruimtevaartindustrie en worden vandaag actief aangewend in ASIC ontwikkeling. Wanneer een energetisch deeltje door een CMOS chip ‘vliegt’, wordt in het silicium een hoeveelheid lading achter gelaten. Deze stoorlading kan in de elektronische schakeling leiden tot een niet-destructieve functionele fout. De chip dient dan zodanig ontworpen te worden, dat hij ongevoelig wordt voor de stoorlading. De stoorlading kan resulteren in verschillende elektrische fenomenen. Flipflops zijn bijvoorbeeld onderhevig aan SEU (Single Event Upset). De inslag veroorzaakt een niet gewilde toestandsverandering van de flipflop. Klassieke CMOS flipflops zijn zeer gevoelig. Deeltjes met een beperkte energie kunnen reeds een SEU veroorzaken. De HIT flipflop (Heavy Ion Tolerant), die we nu gebruiken in onze radiatietolerante bibliotheken, heeft een architectuur die robuuster is wat SEU betreft. Uiteraard is het transistorschema van de flipflop complexer. De cel wordt dus groter en verbruikt meer. Een alternatief is de DICE (Dual Interlocked Storage Cell) architectuur. DICE heeft een aantal bijkomende voordelen t.o.v. de HIT cel. De opzet van de thesis bestaat erin analoge simulaties op te zetten om de SEU-robuustheid van flipflops te bepalen in verschillende technologieën (UMC 180nm, XFAB 180nm, UMC 65nm). Vervolgens kunnen verschillende SEU-tolerante flipfloptopologieën met elkaar worden vergeleken, waarbij ook andere parameters (vermogen, oppervlakte, snelheid) in rekening dienen gebracht. De meest performante SEU flipflop kandidaten kunnen daarna uitgetekend worden (layout) en gekarakeriseerd, zodat de nieuwe cellen kunnen worden opgenomen in de bibliotheek. Ontwerp van een testchip is mogelijk afhankelijk van het tijdsbestek. Dit eindwerk vereist toegang tot Cadence en Mentor Graphics ontwerp-tools. Regelmatige aanwezigheid op imec voor ontwerpondersteuning en het gebruik van de specifieke software tools is aangeraden. Remote inlogen op het imec netwerk biedt de aanvullende mogelijkheid om van thuis uit te werken. Software tools (state-of-the-art) en omgeving: • Cadence: Virtuoso (Schematic Composer + Layout), Analog Design Environment, Spectre simulator • Mentor Graphics: Calibre (DRC, LVS, LPE) • Linux/Unix Tijdsindeling: 10% technologie, 60% ontwerp/simulatie, 30% layout.

Master Thesis/Internship Topics 2013-2014

72

Project: Thesis project Degree: Master in Industrial Sciences majoring in (micro)electronics Responsible scientist: For further information or for application, please contact Geert Thys ([email protected]).

Design prediction tool development for solder joint reliability for printed board assemblies, including the flexibility of components/boards The working heart of any electronic system is the (green-coloured) printed circuit board with many electronic components assembled to it. The material which makes the electrical, but also the mechanical and thermal connection between the component and the board is tin (Sn) based solder. This material is suitable thanks to its low melting temperature allowing to make the connection at acceptable temperatures for board and components. Solder is also a very ductile material, meaning having a low yield stress, allowing to compensate for a thermal expansion mismatch between the component and the board. Where this ductility minimises the stress in board and component in a positive way, it becomes vulnerable for mechanical fatigue fracture occurring under repeated deformations. A proper design and good knowledge of life time for each component helps to avoid these solder joint failures. In the recent years, poor solder joint life time has resulted in major field returns for laptop computers, gaming consoles and even failing electronics in cars. In this work, available Finite Element Models for a wide range of components will be used to estimate the life time of the solder connections. The student will perform parametric studies with as final goal to define a spreadsheet based design tool. This tool should be able to predict life time for a component as function of several parameters such as chip size, component size, solder joint height, board stiffness, temperature cycling conditions etc. This study also allows investigating the mechanical impact zone of every component, in particular valid for large components which could damage neighbouring smaller components. Verification of the tool is done through available internal testing and from well-reported data in literature. Project: Internship or thesis project of minimum 6 months Degree: Master in Industrial Sciences or Master in Science or Master in Engineering majoring in mechanics, material science, physics. Knowledge in FEM and elasticity theory are a benefit, but not required to perform the thesis study. Responsible scientist: For further information or for application, please contact Bart Vandevelde ([email protected]).

Master Thesis/Internship Topics 2013-2014

73

X.

NERF Introduction Imec, VIB (Flanders’ leading life science institute), and the Leuven University have set up a joint basic research initiative to unravel the neuronal circuitry of the human brain: Neuroelectronics Research Flanders (NERF). Supported by the Flemish Government, NERF looks into fundamental neuroscientific questions through collaborative, interdisciplinary research combining nanoelectronics with neurobiology. It intends to push the boundaries of science, by zooming in on the working of neurons at an unprecedented level of detail. In the long run, NERF will generate new insights in the functional mapping of the brain, as well as research methodologies and technologies for medical applications, i.e. diagnostics and treatment of disorders of the central and peripheral nervous system. The NERF labs are located at the imec premises. Read more: http://www.nerf.be/.

Design and construction of automated environments to study spatial memory function in rodents The Kloosterman laboratory at the NeuroElectronics Research Flanders (NERF) in Imec studies how neural circuits and systems in the brain process and store information. For this, we monitor the activity of tens to hundreds of neurons simultaneously as rodents (rats or mice) perform a variety of spatial memory tasks. In one example, rats learn to associate a specific odour cue with a goal location where a small reward can be retrieved. The behavioural testing environment in this case features odour delivery devices and automated doors that are embedded in a multi-arm maze. The aim of this project is to design and build modular and re-usable devices to support complex behavioural experiments for the study of spatial memory function. The project involves embedded system design, 3D computer-aided design (CAD), rapid prototyping and printed circuit board (PCB) design. We are looking for a candidate with a strong background in robotics, electrical engineering or mechanical engineering and an interest in neuroscience. The ideal candidate is able to work independently and does not shy away from challenges. Type of project: Thesis or internship project of 6 up to 12 months Degree: Master in Science or Master in Engineering majoring in robotics, mechanical engineering, electrical engineering, biomedical engineering or similar field. Responsible scientist: For further information or for application, please contact Fabian Kloosterman ([email protected]).

Closed-loop real-time read out and control of memory processing in behaving rats Understanding how new memories are formed and used to guide actions by our brain is a major challenge in neuroscience. Spatial memory processing in rodents can be used as a model to investigate memory processing dynamics. In this project we use large-scale in vivo electrophysiological recordings combined with behaviour assays to study memory processing. In particular, we aim to decode memory-related replay of experience-dependent neural activity patterns at a millisecond timescale. By combining decoding the activity in a real-time fashion with online electrical or optical feedback stimulation of the brain, we can selectively interfere with ongoing memory processing. The rationale of this closed-loop system is to provide experimental evidence for the role of replayed activity patterns in memory consolidation and retrieval.

Master Thesis/Internship Topics 2013-2014

74

Our ideal candidate will have a strong background in computer science or electrical/biomedical engineering and a vivid interest in neuroscience. The candidate will be involved in the implementation of signal processing tools and real-time encoding/decoding algorithms for data streams coming from an array of electrodes implanted in a rat brain. Other activities include fabrication of brain implants for small animals and electrophysiological recordings. Experience with Python (NumPy/SciPy), C/C++ or scientific computing in general is an advantage. Type of project: Thesis or internship project of 6 up to 12 months Degree: Master in Science or Master in Engineering majoring in computer science, electrical engineering, biomedical engineering or similar field. Responsible scientists: For further information or for application, please contact Fabian Kloosterman ([email protected]) and Davide Ciliberti ([email protected]).

Scale-space based segmentation and identification of cells in microscopic images In order to better measure cell’s response to different chemical or mechanical stimuli robust quantification of the cell spatiotemporal organization is required. Accurate identification of individual cellular phenotypes can be obtained by combining automated microscopic acquisition with extensive morphological feature extraction and data mining strategies. The topic will include research into innovative high-performance algorithms for segmentation of large 2D and 3D microscopic images. The work will be directed towards implementation of automated protocols requiring minimal user interaction and allowing parallel processing of the acquired data. Two concrete applications will be addressed: (i) measurement of glial cell activity in functional in vivo confocal or twophoton microscopic images and (ii) classification of white blood cells from live microscopic images. Specifically the student will explore utility of scale space approaches based on successive spatial smoothing and convolution (for example SIFT or SURF) for cell type identification. We are looking for a candidate with strong background in signal processing or skills in programming. Experience in Java or C# will be preferred.

Master Thesis/Internship Topics 2013-2014

75

Type of project: Thesis or internship project of 3 up to 6 months Degree: Master in Science or Master in Engineering majoring in computer science Responsible scientist: For further information or for application, please contact Dimiter Prodanov ([email protected]).

Optogenetic dissection of dopamine function for learning from reward and punishment One form of learning, commonly observed in humans and animals, relies on the reinforcing effect of rewarding or aversive experience. As a result of such learning, sensory cues, behavioral responses or specific actions become associated with positive or negative values, which is critical for seeking resources and avoiding danger. Previous research in animals and humans has well established that neurons which use dopamine as their neurotransmitter are key players in reward processing. These dopamine neurons mainly reside in the midbrain ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). They are activated by unexpected rewards and sensory cues predicting future rewards. When predicted rewards are omitted they are suppressed. Thus, dopamine neurons seem to encode the discrepancy between predicted and actual reward, also called reward prediction errors. Based on formal theories of reinforcement learning, it has been proposed that dopamine acts as a teaching signal to mediate learning from reward. While the function of prediction errors has been intensively studied, the function of cue-evoked dopamine responses has received much less attention. The goal of this project is to evaluate the behavioral relevance of cueevoked dopamine activity in awake, behaving mice, using optogenetic activation and inhibition techniques. Mice will be trained on an olfactory conditioning task, in which different odorants are associated with reward. For selective manipulation of dopamine neurons in vivo, optical fibers will be implanted into the brain. The master student is expected to perform and analyze behavioral/optogenetic experiments and, depending on interest, may also acquire mouse surgery skills. If you are interested in the project and have any questions, please do not hesitate to contact the responsible scientist, Dr. Sebastian Haesler. Type of project: Thesis project with internship of up to 6 months Degree: Master in Science majoring in biology, neuroscience, psychology Responsible scientist: For further information or for application, please contact Sebastian Haesler ([email protected]).

Using superparamagnetic nanoparticles as force actuators in cells and tissues Nanoparticles offer exciting opportunities for the development of new technologies at the interfaces between chemistry, physics and biology. Magnetic nanoparticles are a special class of nanoparticles which can be manipulated using magnetic fields. Magnetic nanoparticles have provided much promise for a number of applications ranging from targeted cell delivery, magnetic resonance imaging contrast enhancement, and targeted cancer therapy in the form of local hyperthermia. The goal of this project is to evaluate the use of superparamagentic nanoparticles as force actuators in cells and tissue. The techniques involved are standard molecular biology (cloning and preparation of plasmid DNA), cell culture (human cell lines and transfection) and conventional (confocal) and advanced microscopy such as transmission electron microscopy (in collaboration). If you are interested in the project and have any questions, please do not hesitate to contact the responsible scientist, Dr. Sebastian Haesler. Type of project: Thesis project with internship of up to 6 months

Master Thesis/Internship Topics 2013-2014

76

Degree: Master in Science majoring in (bio)physics, biomedical engineering, biology Responsible scientist: For further information or for application, please contact Sebastian Haesler ([email protected]).

Design, prototyping and testing of miniaturized brain implants The Kloosterman laboratory at the Neuro-Electronics Research Flanders (NERF) studies how neural circuits and systems in the brain process and store information. For this, we monitor the activity of tens to hundreds of neurons simultaneously as rodents (rats or mice) behave freely. Previously, we have used custom designed brain implants that carry an array of wire electrodes. In collaboration with the Bioelectronic Systems group at Imec, new silicon-based neural probes have been developed that will allow us to record from a larger number of neurons in a wide network of brain regions. These probes will be used in combination with optical stimulation techniques in order to perturb activity of certain types of cells to better understand their role in memory processing. The aim of this project is to design and build prototypes of novel brain implants for rats that combine multiple wire electrodes (tetrodes) and silicon neural probes for recording of neural activity and optical fibers for stimulation. The project will be conducted as a joint effort of two research groups at NERF and Imec and involves 3D computer-aided design (CAD) and rapid prototyping. Experience in printed circuit board (PCB) or embedded system design is an asset. Prototypes will be characterized mechanically and eventually tested in experiments in vivo. We are looking for a candidate with strong background and skills in biomedical, mechanical or electrical engineering and with interest in neuroscience.

Master Thesis/Internship Topics 2013-2014

77

Type of project: Thesis or internship project of 6 months Degree: Master in Science or Master in Mechanic Engineering, Electric Engineering, Biomedical Engineering Responsible scientists: For further information or for application, please contact Fabian Kloosterman ([email protected]) and Dimiter Prodanov ([email protected]).

Inferring population network dynamics from cellular imaging data in behaving animals One of the major challenges in systems neuroscience is the development of robust algorithms for understanding the complex dynamics of neural activity during behavior. Our lab uses the mouse and various imaging and genetic tools to study visual processing by large cortical networks in awake behaving animals. In the course of our imaging experiments, we generate terabytes of high-speed cellular-level calcium imaging data that capture the activity of large neuronal populations in visual cortex in the context of a virtual-reality based spatial navigation assay. To unleash the true potential of these experimental assays, we need to develop robust probabilistic models to infer neural spiking activity from calcium fluorescence signals, as well models of the underlying network dynamics. To help us achieve this aim, we seek highly motivated Master’s students with strong quantitative skills, expertise the analysis of biological signals or imaging data, and a genuine interest in making a significant contribution to neuroscience. Our team at NERF offers a highly interdisciplinary research environment and state-of-the-art labs and computing infrastructure. This is an ideal position for prospective students from the physical sciences seeking to make the jump to brain research. Fluency in MATLAB, Python or/and other data-driven programming languages is required. Type of project: Thesis or internship project of 6 months Degree: Master in Science or Master in (Electrical) Engineering majoring in physics, applied mathematics, computer science, signal and imaging processing Responsible scientist: For further information or for application, please contact Vincent Bonin ([email protected]).

Master Thesis/Internship Topics 2013-2014

78

WWW.IMEC.BE ASPIRE INVENT ACHIEVE

Master Thesis/Internship Topics 2013-2014

79