„New perspective for bonded silicon wafers Inspection“ IR Inspection for multiple applications
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012
Paradigma of Mems Production
Business Unit Lighting & Imaging Europe
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Wafer Level Inspection is essential for process and equipment qualification Black hole for cost models
cost/die @ different yield level 12 Cost/die 10 Substrate & Material
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structuring & Processing Packaging
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Assembly
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Cost/ die
2 0 1
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Assumptions: 75 % of Yield loss can be found here
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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91 Yield in %
cost/ die = 1 Euro pack & bond = 50%
Business Unit Lighting & Imaging Europe
Paradigm of MEMS Business
Paradigm of MEMS Production
- Short time-to-Market - Various materials and bonding methods - Different die sizes and functionality - Different handling precautions - Low Volume production
Quick and easy inspection
New perspective for bonded silicon wafers Inspection ; Matthias Endig ; Semicon Europe 9 October, 2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Methods of Inspection on Wafer Level
Wafer Inspection Methods (non Destructive)
• Infrared imaging (conventional) low resolution • Scanning Acoustic Microscopy (SAM) in-water Inspection • X-Ray health & safety concerns • „Magic mirror“ not suitable for deeper structures
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Telecentric Optics vs. Endocentric Optics
IR Inspection Methods compared
Conventional IR Inspection
IR
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
IR Inspection with Telecentric (Zoom) - Lenses
IR
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Business Unit Lighting & Imaging Europe
Telecentric Optics vs. Endocentric Optics
Comparison between Telecentric Lenses and Conventional Lenses Telecentric lenses feature parallel light beams which means that the distance the photons have to travel is the same at the edge of the image and the centre of the image.
MML series telecentric lens
Angle of view
CCTV lens, lens for a single-lens reflex
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Conventional ( endocentric) lenses have a perspective distortion which means all light has to pass trough one single point ( focal Point)
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Business Unit Lighting & Imaging Europe
Telecentricity CCTV lens Image
Subject
With ordinary lenses, part of the surface of a subject may be hidden by asperities.
Telecentric lens Image
Subject
With telecentric lenses, the surface of a subject is not hidden by asperities.
Telecentric Lenses are Perfect for Measurements and recognition of shape and geometry .
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012
Business Unit Lighting & Imaging Europe
Telecentric Optics vs. Endocentric Optics
Inspection in various “Depths”
Telecentric lenses usually have a very small Focal plane “Depht of Field” which allows to run inspections In the “Focal plane” only blanking out higher and deeper structures.
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Examples
1. Void Inspection 2. Void Inspection on Highly Doped Wafers
3. Alignment Mark for multiple Wafer 4. Glass frit Sealing
5. Underfill 6. Dicing Cut
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Application Examples
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Business Unit Lighting & Imaging Europe
Application Voids
4 main causes for Voids
Bond Quality to be inspected. There are several causes for the most common failure, voids
1.
Particles
2.
outgassing
3.
Materials properties
4.
inappropriate handling
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Voids
Significance of Voids for 3DIC & TSV’s 3D Integrated Circuits with Through-Silicon Vias (TSVs) have significantly more severe requirements for voids than other applications of wafer bonding. Circuits.
Oxide Interface Oxide Interface VOID
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Voids
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VOID Detection
IR Backside Illumination
Topside Illumination
IR Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Business Unit Lighting & Imaging Europe
Application Voids
Backside Illumination of Voids
Light is blocked by metal or dust and particles which appear dark
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Alignment
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Topside Illumination
High Doped Material
Light is reflected by interface layer around particles and appears appear bright Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
TONWERT KURVE SPREIZEN
Business Unit Lighting & Imaging Europe
Application Allignment
Alignment Accuracy Measurement Top Wafer Top & Bottom Wafer Top Surface Alignemt mark Top Wafer Top & Bottom Wafer Bottom Alignemnt Mark
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Alignment
Basic Principle For High Accuracy high magnification is needed By Image processing several Images can be combined into one By this process the Allignment mark Offset can be calculated
Z axis variation of 25μm Image merge
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012
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Business Unit Lighting & Imaging Europe
Application Alignment
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IR- Transmission Measurement Measurement Accuracy Optical Magn. 8x Image/Pixels Relation: 0,8 micrometer XY Repeatability: ± 0.2 micrometer System Accuracy： ± 2um Measurement Time 30 Sec.
IR Backlight
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Application Glass Frit bonding
Business Unit Lighting & Imaging Europe
Glass Frit Bonded Wafers
IR
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Application Glass Frit bonding
Business Unit Lighting & Imaging Europe
Glass- frit sealing defects
Bonding Frames
Seal Integrity Defect
Glass Frit Bonds
Seal Void Defect
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Dice mark inspection
DICING
Blade
Pattern Si
Si
Dicing MEMS is much more difficult because of sensitivity of dies for: •
Contamination,
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Water & Cleaning
•
Outbreaks due to aspect ratios.
•
ESD issues
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Dicing Chips
Edge Dice Marks visible from
View from Wafer SIDE
Chipping is clearly visible from Top with NIR
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
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Business Unit Lighting & Imaging Europe
Application Underfill
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Underfill Inspection
Si Device Silver paste potting
wire
Void Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Al Frame
Business Unit Lighting & Imaging Europe
Underfill Voids
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Application Application Underfill
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Business Unit Lighting & Imaging Europe
Underfill Void
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Application Application Underfill
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Zoom In
Business Unit Lighting & Imaging Europe
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Workflow – Zoom in 8inch Si-Au-Si
Si Au
Au
Si
Au
© SCHOTT AG
Business Unit Lighting & Imaging Europe
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Wafer level IR Inspection - Conclusion 1. Value Driver Process Control; Structure Control, Integrity check
2. Easy Operation no water, lead or special handling
3. Automated Complete automated Wafer Scanning
4. High Resolution by using telecentric Zoom
5. Versatile lenses with various illuminations © SCHOTT AG
IR MEMS Inspector Halle 2, Nr. 2040
Business Unit Lighting & Imaging Europe
We are looking forward to supporting you even better.
Thank you!
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Business Unit Lighting & Imaging Europe
Back Up slides
Back Up slides
New perspective for bonded silicon wafers Inspection ; Matthias Endig ; Semicon Europe 9 October, 2012 © SCHOTT AG
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Back Up Slide
Business Unit Lighting & Imaging Europe
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Highly Doped Wafer Comparison SAM vs. IR-Inspector
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Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Business Unit Lighting & Imaging Europe
„IR-MEMS Inspector“ vs other inspection methods
© SCHOTT AG
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Business Unit Lighting & Imaging Europe
Back Up slide
Bonding Layer By Direct Bonding - offset
Top
Bonded Wafer Inspection with NIR, Matthias Endig, 09/10/2012 © SCHOTT AG
Bottom
Business Unit Lighting & Imaging Europe
1 - SUMMARY
MEMpax®
The Product: • MEMpax® is a thin borosilicate glass made in the SCHOTT down-draw process • Available in all industry standard wafer formats, e.g. 4”, 6”, 8” and 12” • Thicknesses from 0.1 – 0.7 mm • Target markets are the MEMS and Biotech industry
The Advantages: • • • • • •
Significant cost advantage compared to polished glass wafers The CTE of MEMpax ® is matching the CTE of silicon Enabling anodic bonding with silicon wafers Very thin wafers without grinding and polishing Fire-polished surface with roughness < 1nm Wafer formats up to 12” in thicknesses < 300µm
© SCHOTT AG
Business Unit Lighting & Imaging Europe
1 - SUMMARY
Example: Comparison of production flows for a t=0.3mm wafer Traditional
MEMpax®
Float glass (>0.7mm)
Down-draw glass (0.3mm)
Cut to size
Cut to size
Grinding
Polishing
Washing
Wafer (0.3mm)
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Wafer (0.3mm)
Business Unit Lighting & Imaging Europe
Installed Base
© SCHOTT AG
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Business Unit Lighting & Imaging Europe
Control Software Outline 1
Business Unit Lighting & Imaging Europe
Control Software Outline 2
Mag / FOV Low/Hight-Power
Lighting Control
Stage Position
Business Unit Lighting & Imaging Europe
Control Software Outline 3
ZOOM
Focus XY Stage Control
Business Unit Lighting & Imaging Europe
Control Software Outline 4
Step Movement
Designation MAG. Movement
Business Unit Lighting & Imaging Europe
Control Software Outline 5
Measurment
