European Organization for Nuclear Research CERN Training, April 10-12, 2000 “Radiation effects on electronic components and systems for LHC”

RADIATION EFFECTS ON ELECTRONIC COMPONENTS AND CIRCUITS

First course: Radiation Effects on Electronic Components

Martin Dentan CERN - EP - ATE / CEA Saclay DAPNIA

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 1

OUTLINE

1. RADIATION EFFECTS ON MATERIALS 2. UNITS 3. CONSEQUENCES OF RADIATIONS ON ELECTRONICS N TOTAL IONIZING DOSE EFFECTS N DISPLACEMENT DAMAGE EFFECTS N SINGLE EVENT EFFECTS 4. SUMMARY CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 2

1. RADIATION EFFECTS ON MATERIALS ELECTRONIC DEVICES’ MATERIALS: N oxides; N semi-conductors (Si,Ge, GaAs, GaInAsP, …); N metallic compounds (Al, Au, AlCu, AlSi, SnPb, TaSi2, Pt, W, …) from interconnections, etc. ; N organic compounds (based on C, H, O, N, …).

“Radiation sensitive” materials: N oxides; N semi-conductors; N heavy elements from interconnections (W, Ta, Au, Pb, Pt, …). CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 3

RADIATION INDUCED ENERGY DEPOSITION 1. Electron-hole pair creation (ionization): Ionization in Si or in SiO2; N

Direct mechanism: - Incident photons => absorption. - Incident charged particles => ionization along the track.

N

Indirect mechanism: - incident “heavy” energetic particle (n, p, ions, …) => elastic collisions or nuclear reaction => ionization along the track of secondary particles.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 4

2. Chemical bonds rupture: At Si-SiO2 interface; N

Direct mechanism: absorption of photon or charged particle => bond rupture.

N

Indirect mechanism: e+ created in SiO2 slowly leaves the oxide. Bond rupture when crossing the SiO2-Si interface.

3. Atomic displacement: In Si: N

Dislocations along tracks of “heavy” incident or secondary particles (n, p, ions);

N

Clusters of dislocations at the end of the tracks.

In SiO2: N

Amorphisation (but SiO2 already amorphous).

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 5

A. ENERGY DEPOSITION IN OXIDES 1. Cumulated Ionization: Also called TID: Total Ionizing Dose

a/ Mechanism: N

electron-hole pair creation;

N

partial recombination (strong if no electric field);

N

electrons: high mobility => leave the oxide;

N

holes: very low mobility => mostly trapped.

b/ Result: N

net positive charge trapped in the oxide;

N

long term trapping at room temperature.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 6

Energy deposition in oxides – continued.

Cumulated ionisation in a MOS oxide - Example: N-MOS

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 7

Energy deposition in the oxides – continued.

2. Instantaneous ionization: Also called SEE: Single Event Effect

a/ Mechanism: x single highly ionizing particle (incident or secondary ion); x high e+e- pair density along its track; x

bias across the oxide => transient current across the oxide;

x

this mechanism can be helped by the electric field induced in SiO2 by charges created in Si by the single ionizing particle.

b/ Result: x oxide breakdown. 3. Atomic Displacement: x amorphization x

no effects on the oxides (already amorphous).

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 8

B. ENERGY DEPOSITION AT THE Si – SiO2 INTERFACE 1. Chemical bond Rupture: a/ CMOS process: x Si-SiO2 interface : dandling bonds are passived by hydrogen; b/ Mechanism of bond rupture: x energetic hQ => bond ruptures => interface states in Si. x e+ leaving SiO2 => bond ruptures => interface states in Si. x interface states are amphoterous. c/ Results: x interface charges: e+ if Vg0 (NMOS); x carrier’s surface mobility decreases; x no recovery of interface state density at 300K (except in the case of a very high interface state density); x interface states build-up even after irradiation (interface states are induced by e+ leaving SiO2 after irradiation). CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 9

C. ENERGY DEPOSITION IN SILICON 1. Electron-hole pair creation: a/ Mechanisms: - Direct ionization: x photon absorption; x ionization along incident ion or proton track; - Indirect ionization: ionizing secondary particle resulting from collision of p, n, etc. on nucleus from semiconductor and surrounding materials: x elastic collision => recoil ionized atoms => ionization along the track; x D or decay product (Al, Mg, …) from nuclear reaction on Si => ionization along the track; x fission product from nuclear reaction on heavy elements (W, Ta, Au, Pb, Pt,…) => ionization along the track; x J photon from nucleus excitation / desexcitation => ionization by J absorption; CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 10

Energy deposition in silicon - continued

b/ Electrical effects of e+e- creation: - Instantaneous creation of high e+e- pair density along a track : x indirect ionization by secondary particle (recoil atom, D, nuclear decay product, fission fragment, …) => plasma along the track of a single secondary particle => current or charge injection in sensitive nodes => Single Event Effect (SEE): electrical pulse, digital upset, junction burnout, oxide gate rupture, … - Continuous creation of scattered e+e- pair density x main mechanism: direct ionisation by incident particle (photon, electron, proton, ion, …) x LHC: low dose rate => no significant currents; x Electron-hole pairs recombine => no permanent effect.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 11

Energy deposition in silicon - continued

2. Atomic Displacements: Result from particles producing NIEL (Non Ionizing Energy Loss).

a/ Mechanisms: x collisions (elastic diffusion, electromagnetic interaction) in cascade on atoms from semiconductor lattice, produced by: - incident “heavy” particles (p, n, ions); - secondary particles issued from elastic diffusion, nuclear reaction, fission. x defects (vacancies, interstitial, Frenkel pair, dislocation, etc.) are produced along the tracks of secondary particles and in clusters at the end of these tracks.

b/ Effects: x x x x

minority carrier’s lifetime decreases => recombination currents; carrier’s mobility decreases; effective majority carrier’s concentration decreases => resistivity increases; creation of acceptor levels => type inversion (N -> P); Type inversion is significant in high resistivity material (silicon detectors) under high neutron fluence. It is not significant in usual silicon devices (transistors, diodes,…).

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 12

Energy deposition in silicon - continued EXAMPLE OF NEUTRON DAMAGE BY ELASTIC DIFFUSION: recoil atom tracks terminating in clusters

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 13

Energy deposition in silicon – Atomic displacements - continued

Decrease of minority carrier’s lifetime: x (1/9) = (1/9o) + K9. x 9 /9o () depends on the injection (saturation mechanisms) 9 / 9o

1

.75 Strong Injection .50

9o = 2 ns Weak Injection

9o = 500 ns

.25

1010

10

11

12

10

10

13

14

10

) (n / cm ) 2

) is the neutron fluence; W is the minority carrier’s lifetime. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 14

Energy deposition in silicon – Atomic displacements - continued

Decrease of effective majority carrier’s concentration: x “Carrier Removal” effect : n = no exp(-2/k) x Example in N-type silicon:

) is the neutron fluence; n is the majority carrier’s concentration. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 15

Energy deposition in silicon – Atomic displacements - continued

Decrease of carrier’s mobility: x (1/2) = (1/2o) + K2. Examples: K2 = 3 . 10

-19

V.s

2 o = 1500

cm .V .s before irradiation

2

cm .V .s after  = 2,2 . 10 n/cm eq. 1 MeV.

= 1360

2 2

-1 -1

-1 -1

14

-2

) is the neutron fluence; P is the carrier’s mobility.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 16

2.

UNITS

A. IONIZATION UNITS: Cumulated ionisation: x Total Ionising Dose (TID): unit = gray (Gy); 1 Gy = 100 rad = 1 J/kg; x Dose rate: unit = Gy/s x Warning: a dose must always be referred to the absorbing material. The relevant material for electronic components is SiO2. Notation, example: 100 rad(SiO2). Instantaneous ionization by a single particle: x Linear Energy Transfer (LET) unit: eV.mg-1.cm-2. (more often used by physicists: dE/dX) x Warning: LET depends on the target material, on the ionizing particle, and on its energy.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 17

Units – continued.

B. DISPLACEMENT DAMAGE UNITS: x RDU (Radiation Damage Unit ) = displacement damage 2 produced by 1 neutron / cm with an energy of 1 MeV. 2

x 1 MeV equivalent neutron /cm = normalized fluence unit used to compare a real beam to a beam of pure 1 Mev neutrons producing the same displacement damage in silicon (in RDU units). WARNING concerning the unit “1 Mev eq. n/cm2”: x It is suitable to compare beams in terms of production of displacement damage only. x It is not suitable for other materials than silicon (unless specified). x It is not suitable to compare beams in terms of production of Single Event Effects (SEE).

Example : x 1 MeV neutrons => no significant nuclear reactions in Si; x 5 MeV neutrons => significant nuclear reactions in Si, producing energetic ionizing particles (Al, Mg) responsible for Single Event Effects. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 18

2 – Units – Continued.

Single ionizing particle produced by nuclear reaction in silicon V n , D (b a rn ) 1E 0 5 E -1 1 E -1 5 E -2 1 E -2 5 E -3 1 E -3 5 E -4

n + S i -> p + A l

T h r e s h o ld : 3 .8 5 M e V

1 E -4 4

5

10

15

20 22 E n e u tro n (M e V )

V n , D (b a rn ) 5 E -1 1 E -1 5 E -2 1 E -2 5 E -3 n + S i ->

T h r e s h o ld : 2 .6 5 M e V

D + Mg

1 E -3 5

6

7

8

9

10 E n e u tro n (M e V )

1 MeV neutrons => no nuclear reaction in Si => no SEE; 5 MeV neutrons => nuclear reaction in Si => possible SEEs. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 19

Units – continued.

Spectrum of energy deposited in ionization and in displacement damage in silicon by 1 neutron.cm-2. -1

2

rad(Si).n .cm 10

-9

keV/cm3 -10

10

10 -11

10

1 -12

10

-13

0.1

10

-2 10

-1 10

10

0

Ionization

10

1

En (MeV)

-2 10

0 10

1 10

En (MeV)

Displacement damage

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 20

Units – continued. -2

Displacement damage (RDU) made by 1 neutron cm in silicon, as a function of its energy

x 1 RDU = displacement damage produced by 1 n/cm2 having an energy of 1 MeV. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 21

3. CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES

A. TOTAL IONIZING DOSE (TID) EFFECTS 1. MOS TRANSISTORS: Example : NMOS Vg > Vt

Negative fixed charge (ion) Negative mobile charge (electron) Id

Polysilicon gate E E E E E E source N+

P-type Silicon

Oxide gate

drain N+ Vg Id

Vt

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 22

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Effect of oxide trapped charge in NMOS:

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 23

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Oxide trapped charge and interface trapped charge effects in NMOS:

Oxide trapped charge and interface trapped charge effects in PMOS:

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 24

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Contribution of oxide trapped charge and interface trapped charge on threshold voltage shift

NMOS and PMOS threshold voltage shift

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 25

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Influence of the bias on the threshold voltage shift

=> devices must be properly biased during ionizing radiation tests CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 26

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

N Vt depends on the temperature. Example :

Vt also depends on the thermal history of the devices. => Burn-in degrades the radiation hardness.

Vt depends on the dose rate. Example :

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 27

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

DOSE RATE EFFECT, EXAMPLE: NMOS HIGH DOSE RATE M

LOW DOSE RATE

2nd order effect: recombination. Each electron is surrounded O by numerous holes => large recombination S => reduced density of trapped holes in SiO2.

M

M

M

1st order effect: time. Short time irradiation => only a O part of the trapped holes leave SiO2. S

M O

S

O

S

O

2nd order effect: recombination. Each electron is surrounded by few holes => small recombination => high density of trapped holes in SiO2.

1st order effect: time. Long time irradiation => most of the trapped holes leave SiO2.

S

Result: Vit and Vot are relatively small and approximately balanced => relatively small Vt.

M O

Result: large Vit, small Vot => large Vt.

S

Low dose rate can reduce by a factor 5 or more the failure dose of CMOS or BiCMOS circuit

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 28

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

'Vt depends on the gate oxide thickness.

100

Trapped holes leave very thin oxides by tunnel effect 1E3

1E2

10 Oxide thickness (nm)

With tunn el effect

1E1

1E0

1E-1

1E-2

1E-3 1

eff ec t nn el ith ou t tu W

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 29

WARNING: standard deep submicron CMOS technologies are not radiation-hard technologies. A special design is required to get radiation hardness properties.

Ö Very deep submicron CMOS technologies have small 'Vt.

-'Vfb/ Mrad(Si)

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Influence of the fabrication date on the threshold voltage shift of commercial MOS - Example

=> Don’t forget radiation hardness spreading within batch or from batch to batch when selecting COTS. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 30

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Leakage current induced in NMOS by total dose

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 31

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Leakage current induced between NMOS by total dose

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 32

3A - TOTAL DOSE EFFECTS – MOS Transistors – Continued

Other consequences of total dose in MOS transistors:

a/ Decrease of transconductance: Saturation transconductance : Gm = (2 2 Cox Id W/L)

1/2

N interface states density increases N surface mobility decreases Ö Gm decreases. b/ Decrease of drain current - gate voltage slope in weak inversion: Weak inversion slope : Sfi = (kT/q)Log(1+Cox/Csc) N N N

interface states density increases Depletion field decreases Csc increases

Ö Sfi decreases. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 33

3A - TOTAL DOSE EFFECTS –Continued

2. BIPOLAR TRANSISTORS: Example : NPN transistor Emitter – base junction is forward biased. Before irradiation: N Ib1 = holes current injected from the base into the emitter. N -4 = Ic / Ib1

Ib2

-

Ic

-

Emitter

Emitter N+ Base p

Drift nCollector N+

Collector

Undepleted silicon

Depleted silicon

Undepleted silicon

SiO2

After irradiation: N Ib1 = holes current injected from the base into the emitter. N Creation of interface states => recombination current : Ib2 = current of recombination of a fraction of the electrons injected by the emitter into the base. N - = Ic / (Ib1 + Ib2) < -4 Base

+ + Ib1

Ic : Collector current Ib1 : regular base current Ib2 : recombination current

In PMOS, e+ trapped in SiO2 migrate near Si and induce additional interface states. This makes the interface state density and thus the recombination current Ib2 larger in PMOS than in NMOS. This phenomenon is aggravated at low dose rate. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 34

3A - TOTAL DOSE EFFECTS – Bipolar Transistors – Continued

Before irradiation: N -(Ic) is almost flat

Remark : - degradation depends on the dose-rate.

In weak injection (low Ic): N no saturation on the interface states; N no saturation of the recombination current; N - degradation increases rapidly when Ic decreases.

In strong injection (high Ic): N saturation on the interface states; N saturation of the surface recombination current; N - degradation decreases slowly when Ic increases.

After irradiation:



CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 35

3A - TOTAL DOSE EFFECTS –Continued

3. P-JFET TRANSISTORS: Before irradiation : N channel conduction controlled by Vgs; N small source and drain (Rss’ and Rdd’) resistances.

After irradiation: N positive charges are trapped in the oxides between source and gate and between gate and drain; depletion in the silicon located under these oxides; source and drain resistances increase; effective pinch-off voltage decreases (due to Vss’ = Rss’xId); these mechanisms do not affect N-JFETs. Vp depends on the dose rate.

N N N N N

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 36

3A - TOTAL DOSE EFFECTS –Continued

3. P-SILICON RESISTORS: Before irradiation : N the resistor value depends on the geometry and on the resistivity of the semiconductor strip.

After irradiation :

+

SiO2

+ + + + + + + + + + + + + + + + + + + + +

P

+

P+

N positive charges are trapped in the oxide covering the semiconductor strip; these charges induce a depletion in the semiconductor; the thickness of the non-depleted semiconductor decreases; the resistance increases. R depends on the dose rate. N N N N

P+ P

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 37

3A - TOTAL DOSE EFFECTS –Continued

3. MOS CAPACITORS: Before irradiation : N highly doped silicon under the oxide => low voltage coeficient. N capacitance depends on oxide thickness. After irradiation: N positive charges trapped in the oxide. N high doping level => trapped charges do not induce space-charge effect. Ö The capacitance remains unchanged.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 38

3 - CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES - Continued

B. DISPLACEMENT DAMAGE (NIEL) EFFECTS NIEL: Non Ionizing Energy Loss.

1. MOS TRANSISTORS N Vg > Vt induces a carrier inversion layer in MOS channel; N in this inversion layer, carriers are located in a stable energy level; N they are not subject to recombination processes; N recombination centers induced by atomic displacements do not modify the channel carrier concentration; N the surface mobility is not modified by atomic displacements; N the channel transconductance is not modified by atomic displacements. Ö MOS transistors are not affected by displacement damages. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 39

3B - DISPLACEMENT DAMAGE EFFECTS – Continued

2. BIPOLAR TRANSISTORS: Example : NPN transistor Emitter – base junction is forward biased. Before irradiation: N Ib1 = holes current injected from the base into the emitter. N -4 = Ic / Ib1

Ib1

Collector

Collector N+

Drift n-

Base p

Emittor N+

Emittor

Ic

- -

Undepleted silicon

Depleted silicon

Undepleted silicon

SiO2

After irradiation: N Ib1 = holes current injected from the base into the emitter. N creation of recombination centers in the base. N Ib2 = recombination current of a fraction of the electrons injected by the emitter into the base. N - = Ic / (Ib1 + Ib2) < -4 Base

+ + Ib2

Ic : Collector current Ib1 : regular base current Ib2 : recombination current

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 40

3B – DISPLACEMENT DAMAGE EFFECTS – Bipolar – Continued

Before irradiation: N -(Ic) is almost flat

After irradiation: In strong injection (high Ic): N saturation of the recombination centers; N saturation of the volume recombination current; N - degradation decreases slowly when Ic increases. In weak injection (low Ic): N no saturation of the recombination centers; N no saturation of the recombination current; N - degradation increases rapidly when Ic decreases.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 41

3B – DISPLACEMENT DAMAGE EFFECTS – Bipolar – Continued

Radiation-hardness criterion : (related to displacement damage effects) Physical criterion : no significant degradation if 9 > 9b 9 = minority carrier lifetime; 9b = minority carrier transit time through the base.

N The transit time 9b is directly linked to the transition frequency Ft; N The minority carrier’s lifetime is directly linked to the neutron fluence; Ö Bipolar transistors radiation hardness to displacement damage effects can be assessed by Ft measurement.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 42

3B –DISPLACEMENT DAMAGE EFFECTS – Bipolar – Continued

Good parameter to estimate the gain degradation: N 'E = E – Eo N 'E/E

depends on Eo depends on Eo

=> bad parameter. => bad parameter.

N (1/-) = (1/- - 1/-o)

free from -o

=> good parameter

Ib2 = Ic '(1/E) => '(1/E) represents the origin of the gain degradation.

Other displacement damage effects on bipolar transistors : N “carrier removal” N silicon resistivity increases N Serial resistance increases Ö Vce saturation increases; Ö Diodes breakdown voltage increases. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 43

3B –DISPLACEMENT DAMAGE EFFECTS – Continued

3. JFET TRANSISTORS: N N Ö Ö Ö

“carrier removal” effective carrier’s concentration decreases in JFET channel; pinch-off voltage decreases; Idss decreases; transconductance decreases.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 44

3B –DISPLACEMENT DAMAGE EFFECTS – Continued

4. RESISTORS made with high resistivity silicon: N “carrier removal” N effective carrier’s concentration decreases in high resistivity strips; Ö the resistance increases.

5. CAPACITANCES: N

highly doped silicon under the oxide;

N Ö

“carrier removal” is not effective; the capacity remains unchanged.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 45

3B –DISPLACEMENT DAMAGE EFFECTS – Continued

OPTOCOUPLER

GaAs LED

Si bipolar phototransistor photon: h3 > Eg (Si)

Displacement damage effects: - Bipolar current gain - decreases - light attenuation in the medium between LED and bipolar ? - LED light emission decreases (non radiative recombination)

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 46

LED after neutron irradiation

LED before neutron irradiation Space charge region

P

Space charge region

N

P

non-radiative recombination

Recombination center

N

I

I

h3 radiative recombination

P

h3

radiative P recombination

N h3

N h3

non-radiative recombination After neutron irradiation, defects in the bandgap induce non-radiative recombinations. A fraction of the current is lost, leading to a reduced photon flux. 

 pre-rad



 pre-rad ' post-rad

I

I

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 47

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – Continued

C. SINGLE EVENT EFFECTS 1. BASIC MECHANISMS a/ “Instantaneous” charge injection in a node, enhanced by funelling: N single highly ionizing particle (secondary ion in HEP experiments); N high e+e- pair density along its track; N the track cross a space charge region (reverse-biased junction); N the junction field lines propagates along a portion of the track; N charge along this portion of the track is quickly swept onto the junction by drift; Ö fast collection of a very high quantity of charges on a unique node (or on several nodes in the case of very advanced technologies). b/ “Instantaneous” short circuit along a conductive plasma string: N single highly ionizing particle (secondary ion in HEP experiments); N high e+e- pair density along its track; Ö high conductivity string along the track; Ö instantaneous short circuits through reverse biased junction, oxide, etc. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 48

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – Continued

2. NON-DESTRUCTIVE EFFECTS (non permanent errors): “Instantaneous” charge injection in a sensitive node, enhanced by funelling.

Funelling in MOS : Transient pulse in a node => upset in SRAM (latches) and error in logic circuits.

Funelling in capacitor : Charge deposition in a cell => upset in DRAM and error in analog memory.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 49

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – Continued

A few words about memories Memory ROM PROM REPROM, OTPROM EEPROM, FLASH, DRAM SRAM Ferroelectric RAM

Bit storage Layout program Fuse / antifuse electrical charge electrical charge latch logic state Electrical dipole

Rewrite “on line” N N N Y Y Y

Memories are sensitive to SEE (Single Event Effects): N Bit storage = electrical charge => SEE sensitive via charge deposition. N Bit storage = latch logic state => SEE sensitive via current pulse.

Memories are sensitive to TID (Total Ionizing Dose): N total ionizing dose = cumulated electrical charge deposition. N if bit storage = electrical charge, cumulated charge deposition can modify the charge of the memory cell up to an undetermined logic state. N refreshment is not a solution, because refreshment circuitry suffers from total dose. N other total dose effect on memories: transistor parameter shift, leakage currents. N Architectural solutions: redundancy + voting or EDAC (Error Detection And Correction); static registers instead of dynamic registers; hardened architectures. N Technological solutions: SOI substrate + rad-hard process, or ferroelectric RAM. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 50

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – NON DESTRUCTIVE EFFECTS – Continued

MAIN CONDITIONS TO PRODUCE A SINGLE EVENT UPSET (SEU): A “large enough” quantity of charges must be deposited in a “short enough” time in a “sensitive” node of the circuit. N The quantity of charges must be larger than the minimum required to produce an upset => the LET (Linear Energy Transfer) of the particle that deposits energy must be higher than a threshold LET. N The charge must be deposited in a sensitive node The cross section of the sensitive node is: S = U / () cos T (cm2) (U = Upset number;  = fluence; 6 = incident angle)

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 51

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – Continued

3. DESTRUCTIVE EFFECTS (permanent errors) Instantaneous “short circuit” along a plasma string. a/ Single Event Gate Rupture (SEGR) in MOS devices: N single highly ionizing particle (secondary ion in HEP experiments); N high e+e- pair density along its track across the gate oxide N Ö Ö Ö

bias across the oxide; high instantaneous current; oxide breakdown. gate-to-channel short circuit: permanent effect.

ion track

gate (-)

p+

n+ p

source (gnd)

n+ p

p+

holes electrons n epi layer n+ substrat drain (+)

In power MOSFETs, this mechanism is enhanced by the electrical field induced in SiO2 by the charges deposited by the ionizing particle in Si under SiO2. This occurs when the devices are “OFF” (high source-drain voltage drop)

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 52

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – DESTRUCTIVE EFFECTS – Continued

b/ Single Event Burnout (SEB) in power MOS and power BJTs: N device “OFF” Ö high voltage drops across the reverse biased junction; (BJT base-collector junction, or DMOS drain – channel junction) Ö high electrical field; N a single highly ionizing particle crosses the junction (a secondary ion, in HEP experiments) Ö high e+e- pair density along its track; Ö Multiplication by avalanche (owing to the high electrical field); Ö high instantaneous current, amplified by the gain of the bipolar; Ö junction breakdown; Ö short circuit: permanent effect. Power NMOS are more sensitive to SEB than power PMOS, because the impact ionization rate is larger for electrons than for holes.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 53

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – Continued

4. SINGLE EVENT LATCH-UP (SEL) N “Instantaneous” charge injection in a sensitive node; N Destructive effect if no protection applied.

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 54

3 – CONSEQUENCES OF RADIATIONS ON ELECTRONIC DEVICES – SINGLE EVENT EFFECTS – Continued

4. SOI SOLUTION AGAINST TRANSIENT EFFECTS: (SOI: Silicon On Insulator)

CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 55

4.

SUMMARY

Energy deposition : N N

direct mechanism: by incident particles. Indirect mechanism : by secondary particles from elastic collision, nuclear reaction, etc.

Effects on material : N N N

ionization dose; chemical bonds ruptures ionized track displacement damage

Effects on elementary device : Permanent effect: N Leakage current N Parameter degradation

Destructive effect: Non destructive effect: N Single Event Gate Rupture N Single Event Upset N Single Event Burnout N Single Event Latch- up (*)

Effects on circuit: Permanent effect: N Power consumption n N Features degradation N Lose of functionality N Stuck bit in memory

Destructive effect: Non destructive effect: N Single Event Gate Rupture N Memories : bit errors, memory erasing N Single Event Burnout N Logic circuits : bit errors N Single Event Latch-up (*) N Analog memory : error

(*) destructive effect except if current limitation. CERN Training / April 11, 2000 / Radiation Effects on Electronic Components and circuits, part 1 of 2 / Martin DENTAN / p. 56