radiation effects on devices : total ionizing dose...

1

UNIVERSITE MONTPELLIER II

byJ. Gasiot

«Electronique et Rayonnement»Université de Montpellier II, FRANCE

CERN TrainingRadiation effects on electronic components and systems for LHC

Radiation effects on devices :Total Ionizing Dose, displacement effect, single event effect

Acknowledgments : Laurent Dusseau, G. Hubert, E. Lorfèvre. Many of the viewgraphs come from original works developed in our team.

2

OUTLINE

• Introduction

• Radiation field & dosimetry

• Total ionizing dose

• Displacement

• Single event effect

• Conclusion

3

Introduction

Radiation effects on electronic devices are observed :

Nuclear applicationscivil

high Dosegamma, electron, neutron

MilitaryDose and photocurrents in SCX-ray flash

Acceleratorshigh dose, displacement and single eventhadrons

Spacedose, displacement (LEO) and single eventheavy ions, electrons protons

Commercial LSI at ground levelsingle event neutron and material contamination

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Introduction

Radiation failure classification in devices :

Cumulative effects :Long term cumulative effect

Dose (TID, Total Ionizing Dose) and Dose rateIonization and trapping in insulators, bulk and interface

Displacement damage

Single Event Process (SEP)Short time response resulting from the energy transfer of a particleto the device.

5

Introduction

24 %43 %

33 %

UnidentifiedAnomalies

OtherAnomalies

Radiation Induced Anomalies

Space anomalies

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1E+0 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 1E+8

Tracker

Calorimeters

Muon Chambers

Cavern

Total Dose (rad/10 years)

Space

Comparison with space environment

Total Dose in Space and CMS

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1.E+05 1.E+07 1.E+09 1.E+11 1.E+13 1.E+15

Tracker

Calorimeters

Muon Chambers

Cavern

Charged Hadrons Flux (particles/cm2/10 years)

Protons in space

Protons in tracker

Pions in tracker

HCAL ECAL


Charged Hadron Flux in space and CMS

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1E+07

1E+08

1E+09

1E+10

1E+11

1E+12

1E+13

1E+14

1E+15

1E+00 1E+01 1E+02 1E+03 1E+04

Energy (MeV)

E.d

ΦΦ/d

E (

1/cm

2/10

yea

rs)

Pions in CMS tracker

Protons in space

Protons in CMS tracker


Charged Hadron Diff. Energy Spectrum

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OUTLINE

• Introduction


• Displacement

• Conclusion

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•Activity•Luminosity

Source Field Material

•Flux•Fluence•Stoppingpower

•Dose•Effect

Radiation field & dosimetry

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•ActivityUnit: Ci, Bq (s-1)1 Ci=3.7 1010 Bq (disintegrations . s-1)

•Luminosity fkS

NNL 21=

N1,N2 number of particlesS: Interaction surfacef: Collision frequencyR: Activity :cross section

LRi i∑= .σ

iσ

SourceSource

Radiation source

•Typical activity :Co60 radiotherapy k CiGeological sample 0.1 Bp/g

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Radiation field

• Φ Flux cm-2 s-1

• Ψ Fluence cm-2

Field

Typical values :- neutron at ground level : 0,1 cm-2 s-1 - protons in space, belts (E > 10 MeV) : 105 cm-2 s-1 - Electrons in space belts (E > 1 MeV) : 106 cm-2 s-1

- heavy ions in space (Geo, 10 years) : 106 cm-2

Radiation field

For a charged particle beam, the average energy loss ischaracterized by (ICRU) :- Stopping power, S ( MeV/µµm): average energy loss per unit pathlength of a charged particle traversing a material - resulting from coulomb interactions with

- Electrons (Collision) Scol- Atomic nuclei (nuclear) Snuc

- Mass stopping power (1/ρρ) SThe energy may not be transferred in the surrounding path area.Nuclear reactions are not considered.

Field : particle energy loss

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Dosimetry

• Macroscopic : Dose

Gy (J.kg-1)

• Microscopic : LET,

NIEL

• Macroscopic :

- radiation protection Sv

- in Si e-h production

3.7 1015

e-h /Gy

• Microscopic : MeV g-1

LET : charge deposition around

the track

NIEL :energy transferred to recoil

atoms

Physical measurement Effect

Material

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Dosimetry

Dosimetry is concerned by the determination of the energy deposited in thearea of interest. As direct a measurement is most of the time impossible, a dosimeter is used.There are two levels- The physical characterization- The effect on a property of the considered. device :Measuring a dose at the first level on expect to obtain the second.Macroscopic physical data :The average energy deposited in a material per unit of mass at the point ofinterest is called Dose, Absorbed Dose, or Total Dose : - Gy (J.kg-1) (1 Gy = 100 rad )Macroscopic effect :In personal dosimetry the effect unit is the Sv (Sievert)1 Gy gamma is 1Sv1 Gy neutron or proton correspond to several Sv

Material : energy deposition

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Dosimetry

Material : energy deposition

Typical doses : Ground level, population : 0,5 rad/yearLethal dose : 4 Sv (4 Gy gamma whole body)Space mission 10 y : GEO 10 krad Constellation 100 kradNuclear reactors : D >> 1 MGy

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PARTICLE EFFICIENCY FOR TOTAL DOSE IN Si

Iron 104 max TID is closeProton 106

Electron 107

Photon 108

Neutron 109 long discussions

Even if this kind of data must be used with care, its aninteresting first response ( order of magnitude).

- Fluences (cm-2) that produces 1 Gy (TOTAL IONISATIONDOSE) in Silicon ( Particle energy : E = 14 MeV)

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Carrier densitycm-31010

Insulator

1022

Conductor

1015 1019

Semiconductor

Transient Phenomenon :Photo-currents

Permanent or semi-permanent Phenomenon :Displacements

Trapped charges + annealing

∆V = 3,6 d2 DC/Gy ~ 1015 cm-3

for d =100 nm and D=10 Krad ∆V=3,6 V

D, dosed, oxide thickness

Radiation Effects

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Dosimetry

LETdx

d=

Φ

ρ1

Material- Linear Energy transfer LET ( MeV.cm2. g-1) : Energy deposition related to Ionization along the particle path

- Non Ionizing Energy Loss NIEL ( MeV.cm2. g-1) : Energy deposition related to recoil atoms along the particle pathUsual parameter for displacement damage

Others convenient units are used : - MeV.µµm -1

- C.µµm -1

Usual parameter for Single Events

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MEV/(mg/cm2))

MEV/µmpC/µm

*0,2321

*0,0446

*96,5665

Linear Energy Transfer Units in Silicon

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10-2 10-1 100 101 102 1030,01

0,1

1

10

Proton Alpha Silicium

Energy (MeV)

LE

T

MeV

/(m

g/cm

2)LET in Silicon

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0,01 0,1 1 10 1E20,0

0,5

1,0

1,5

2,0

proton alpha

Energy (MeV)

LE

T

MeV

/(m

g/cm

2)

0,25 and 0,35 µm Technology Sensibility

SEU Sensibility

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10-2 10-1 100 101 102 1030,01

0,1

1

10

1E2

1E3

1E4

1E5

1E6 proton alpha Silicium

Ran

ge

(µm

)

Energy (MeV)

Range in Silicon

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LET and Range in Silicon

0,01 0,1 1 10 1E2 1E3 1E4

0,1

1

10

H He Li Be B C N O F Ne Na Mg Al Si P

LE

T (

MeV

.cm

2 /mg

)

Range (µm)

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Total dose Effects

Charge Trapping

Charge trapping after irradiation Threshold voltage degradationas a function of the total Dose

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

- ------ ---

Metal

Si

SiO2

Charge trapped at the interface

Charge trapped inthe oxide volume

NMOS

0

1

2

3

4

5

6

0 100 200 300 400 500Dose (Gy)

∆∆vt

h (V

)

+VGS

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Radiation Effects

Heavy Ions and Protons• Single Event Effects (Semiconductor / Oxide)

•Total dose effect (Oxide)

• Displacement damage (Semiconductor )

CMOS technologies Single Event Latch upSingle Event Upset

Power devices Single Event BurnoutSingle Event Gate RuptureSingle Event Latchup

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ION

Reverse biased junction

� Diffusion, radial and slow

Generation of electron-hole pair Collection � Drift, Field funneling

Heavy ion - Semiconductor interaction

Radiation Effects

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OUTLINE

• Introduction



• Displacement


• Conclusion

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TOTAL IONISATION DOSE EFFECT (TID)

Total Ionizing Dose (TID) induces :charge trapping in the oxide

new states at the Si-SiO2 interface.

- TID may change the device electrical characteristics for a dose as low as 10 Gy

- Long term behavior, interface state density and bulkcharge, depend on the device history.– Important parameters are :

- Dose- Dose rate- Applied voltage- Temperature- Time.

- These parameters must be taken into account in the device selection.

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TOTAL IONISATION DOSE IN : Si and SiO2

- In Si ( r = 2,3 g cm-3, pair creation energy = 3,8 eV)

In Si N = 3,7 1015 (electron-hole pairs) cm-3 Gy-1

- In SiO2 ( r = 2 g cm-3, pair creation energy = 17 eV)

In SiO2 N = 7,6 1014 (electron-hole pairs) cm-3 Gy-1

- To obtain this result, it is supposed that the energy is mostly transferred to electrons.

- The density of electron-hole pairs for one Gy is very low, unless high dose and dose rate :

- No effect on metal

- No effect on Si or others SC (for low dose rate < 105 Gy-1 s-1 )

- Possible effect on insulator - Trapping (starting at 10 Gy)

Very high dose rate may affect the semiconductor : starting with low carrierconcentrations (military applications)

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TOTAL IONISATION DOSE IN SiO2 ( BULK)

Typical Silicon oxide capacity behavior under irradiation :

- 1 - In SiO2 during irradiation e-h pairs are created

- 2 - As electron and hole mobility are quite different (µµe >> µµh)

- Most electrons may get out

- Most holes can be trapped

- 3 - The charge positive induced by D in the capacitor (S, a) is given by :

∆∆Q = f a S N e D

f is a collection efficiency (0 < f < 1).

f = 0 hard oxide

f= 1 dosimeter

∆∆Q can be considered as the equivalent charge near the surface.

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- With a proper electric field holes may be trapped near to the Si-SiO2 interface,

it’s the worst case :

∆∆Q = a S N e D

The capacity is C = εε S/a (εεr = 3,9)

The voltage drop is : ∆∆V(Volt) = 3,5 a2(µµm) D(Gy)

High dose, bad quality (f = 1) thick oxides (a2) develop important voltage.

- At the device level :

MOS Gates - not a problem for LSI

All devices - Thick Oxide next to the SC may induce, leakage, .....

TOTAL IONISATION DOSE IN SiO2 ( BULK)

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Typical Silicon-silicon oxide interface behavior under irradiation :

In device fabrication, interface states density are kept as low as possible.

Electron injection occurs in the interface states, charges are exchanged with Si.

Interface state charge can be positive or negative depending on the fermi levelposition in regard to the state energy location.

- n channel - acceptor - (negative)

- p channel - donor - (positive)

Interface states charge changes with polarization (time constant).

Total ionizing dose at the Si-SiO2 interface

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- 1 - At Si-SiO2 interface during irradiation chemical bonding are changed,hole trapping at interface, some hydrogen migration have been observed....

- New interface states are formed.

- Interface state density vs. energy is changed.

- Interface charge is more important.

As a result : static and dynamic electrical response of the Si-SiO2 is altered.

- 2 - Si-SiO2 interface state density evolution with time after irradiation :

- Interface state density changes with time.

- Construction after irradiation.

- Effect of annealing, hole trapping at interface.

Total ionizing dose at the Si-SiO2 interface

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TOTAL IONIZATION DOSE AT THE Si-SiO2 INTERFACE

Si O

Si

2

Q Bulk

Q Interf.

Dynamic charge exchange

nm

n'(Q), p'(Q)

n, p

Interface state charge and bulk trapped charge will play an important role :changing the free carrier density n and p next to the interface

possible inversion layermodifying the carrier mobility and life time

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TOTAL IONIZATION DOSE EFFECTS IN DEVICES

MOSTotal ionization dose effects in MOS devicesresult from both, bulk charge and Silicon-silicon oxide interface charge :- Induced mobility degradation- Threshold voltage changes- Induced leakage

Device characteristic changes :- Vth (threshold voltage). Interface and bulkcontribution.- Q Trapped oxide charge (density)- Q Interface trap charge (density and Edistribution)- µµ Mobility in the channel.- ID Channel output drive (n or p)

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BIPOLARTotal ionization dose effects in Bipolar devices result from siliconoxide (protection, isolation, non active) layers proximity with Siactive device area :

- Induced mobility degradation - Induced leakage

Device characteristic changes :- Gain b.- LeakageIC - Integrated circuits

Frequency operation Access and delay time Power supply current

TOTAL IONIZATION DOSE EFFECTS IN DEVICES

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OUTLINE

• Introduction



• Displacement


• Conclusion

39

- Displacement damage is related to lattice defect density induced by (secondary) particle collision with atoms, in thetarget, that are ejected from their initial position.

- Lattice defect density will increase with irradiation, inducing adegradation of the material characteristics.

- For the semiconductor, introducing new defects means :- diminution on the carrier life time (minority),- carrier charge density change,- reduced mobility

The electrical characteristics degradation of the semiconductorwill affect the device performances.

Displacement

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The NIEL, Sd , is a target oriented parameter : average energy lossinducing displacement in the target.NIEL simple expression for a mono atomic target :

Sd = (N/A) ΣΣ σσi(E) Ti(E) MeV g-1 cm2

N is the Avogadro number, A is the atomic number of the target.σσ(E) is the interaction cross section. T(E), the average part of theenergy of the recoil atom that will induce displacement. The variouspossible interactions (i) are taken into account.

Particle interaction is a stochastic process, the NIEL is just anapproximation that get sense when the number of events is quitelarge in the considered area.high energy particles :

- 1 GeV muon will induce a shower that will affect billions ofparticles.

Displacement

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Role of (relatively) low energy particles in displacementdamage.Collision with atoms :

- Elastic- Inelastic

- Protons and heavy ions are important at low momentum.- Electrons induce displacement at high energy.- Photons do not have any effect if their energy is lower than 10MeV - wavelength above 10-13 m.

- Neutron behave almost like protons at high energy (100 MeVand up).Displacement damage is important at low energy. Inelasticcollisions are of particular interest.

Displacement

42

The energy threshold for atom displacement is in therange of 6 to 25 eV.

- One 100 MeV electron, Si recoil 0,77 MeV, 0,1MeV in displacement

2 500 Frenkel pairs (90 % recombine in aminute).

Displacement

43

OUTLINE

• Introduction



• Displacement


• Conclusion

44

Effects in CMOS technologies

SRAM structure struck by an ion

Device level Circuit level(memory cell)

Single Event Upset

ION

ION

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Drain current Evolution of the node voltage

For impacts in or close to the drain

0,0E+0

2,0E-3

4,0E-3

6,0E-3

8,0E-3

1,0E-2

1,2E-2

1,4E-2

1E-13 1E-12 1E-11 1E-10 1E-09Temps (s)

Ids

(A)

x=0,6umx=1,5umx=1,9umx=2,4 um

Qcollected

0

1

2

3

4

5

1E-12 1E-11 1E-10 1E-09Temps (s)

Ten

sion

s (V

olts

) Vgrille

Vdrain

(1)

(0)

If Qcollected > Qcritical SEU

Single Event Upset


46

Drain current Evolution of the node voltage

For impacts in or close to the drain

0,0E+0

2,0E-3

4,0E-3

6,0E-3

8,0E-3

1,0E-2

1,2E-2

1,4E-2

1E-13 1E-12 1E-11 1E-10 1E-09Temps (s)

Ids

(A)

x=0,6umx=1,5umx=1,9umx=2,4 um

Qcollected

0

1

2

3

4

5

1E-12 1E-11 1E-10 1E-09Temps (s)

Ten

sion

s (V

olts

) Vgrille

Vdrain

(1)

(0)

If Qcollected > Qcritical SEU

Single Event Upset


47

LET (MeV.cm2/mg)

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

Cro

ss S

ecti

on

(cm

2)

0 20 40 60 80

Cross Section of a 0.6 µm CMOS technology

Saturation

Threshold

Single Event Upset


48

Single Event Latchup

Example oflatchup characteristic

Schematic representationof the parasitic NPNPstructure

0,1

1

10

100

2 3 4 5 6

Vsupply (V)

Isup

ply

(mA

)

Holding pointTriggering point

Vdd

P+P+P+

P substrate

Vout Vss

Vin

NPN

N+ N+N+

Nwell PNP

ION Destructive Failure


49

� Adding contacts,body ties

� Geometric dimensions

P+N+

N well

P substratecontacts

N+N+P+P+

P+ P+N+N+

N well

P substrateGuard rings

P+ P+ N+N+

� Guard rings

SEL Hardening


50

� Epitaxy

� Doping

N+N+

N well

P+substrate

P epitaxial zone

P+P+

Isolation trench

N+N+

N well

P substrate

P wellBuried oxide

P+ P+

� SOI

SEL Hardening


51

Effects in Power Devices : MOSFET, VIP

Single Event Burnout

Source N+Prise P+ Body P

CanalGrille polysilicium

Oxyde de grille

Métal

Substrat N+

Contact de Drain

épi N

ION

émetteurn+ p

n epi c ll ct ur

asprise p +

ION

Power MOSFET (VDMOS) = 15000 cells in parallel

Triggering of the parasitic bipolar transistor Burnout

52

Effects in Power Devices :


trace de l'ion

p

n

n+

n+ 5 ns after the ion’s passage

Potential and current lines Generation rate

53

MOSFET, VIP


trace de l'ion

p

n

n+

n+

Potential and current lines Generation rate

25 ns after the ion’s passage

54

SEB Hardening

0

5

o i d µm

µm

0 5 0 215 30 35 40 45

P P P+P+N+ N+

standardB450H

Sensitive at 380 V Sensitive at 460 V

Sensitive at 310 V

Br 142 M

eV


0

5µm

P+ PN+

PP+

N+

55

1E+14

1E+15

1E+16

1E+17

1E+18

1E+19

12 14 16 18 20 22 24Distance (microns)

Log

Con

cent

ratio

n (c

m-3

)

Doping Profile at theepi-substrate junction

n+

p plug+ p plug+p emitter

source metallization

gate

n+ substrate

epi n

b s

c l e t r

�

�

�

LET Sensitivity� Standard 1� Stepped profile 1/6� Gradual profile 1/30


SEB Hardening

56

Single Event Gate Rupture

n+

p plug+ p plug+p

source metallization

gate

n+ substrate

epi n

ION

gate oxide

VG < 0 V

Drain contact

VDS > 0 V

Electronsto draincontact

Holes tosourcecontact

Gate electrode

E

ION track


57

SEGR Hardening

PP+

N+

0

5

oxi de µm

µm

0 5 10 2015 30 35 40 45

P P P+P+N+ N+

standard

� Oxide thickness optimization� Reduced area of gate oxide� Extended plug

��

�


58

Single Event Latchup

n+

p plug+ p plug+p

Emitter metallization

Gate

p+ substrate

epi n

Collector +VCE

ION

Parasitic thyristor Example of Latched cell

Hardening solutions comparable to SEB

Effects in Power Devices : IGBT

59

ConclusionDevelopment of an Electronic systems Evaluation of the constraint

Radiation field Working conditions (time, temperature, ..)

Testing conditionsSystem evaluationRadiation hardening level :Device

technologydesign

Circuitdesign

SystemredundancySoft correctionShielding

radiation effects on devices : total ionizing dose...

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