principles of semiconductor devices-lecture39
TRANSCRIPT
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www.nanohub.org
NCN
ECE606:SolidStateDevicesLecture39:ReliabilityofMOSFET
1AlamECE-606S09
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Outline
AlamECE-606S09 2
1. Introducon2. NegaBveiasTemp.Instability3. GateDielectricreakdown4. RadiaBonInducedDamage5. Conclusion
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Warranty,productrecallandotherfactsoflife
AlamECE-606S09 3
Inthiscourse,you
arelearningto
analyze/design
MOSFETsthatgo
inanIC
becausetheICs
operateinincredibly
harshcondiBons,turningonandoff
trillionsofBme
duringitslifeBme.
thereforetheproperBesofthe
MOSFETkeepchanging.
Eventually,S/Dcanbeshorted,thegateoxidecanbreak,etc.
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SiOandSiHonds
AlamECE-606S09 4
Broken Si-H bonds
Negative Bias Temperature Instability (NBTI)
Hot carrier degradation (HCI)
Broken Si-O bonds
Gate dielectric Breakdown (TDDB)
Electrostatic Discharge (ESD)
Radiation induced Gate Rupture (RBD)
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NegaBveiasTemperatureInstabilityDefined
AlamECE-606S09 5
VD(volts)
ID(mA)
beforestress
aZerstress
012340
4
3
2
1
StressTime(sec)
%
degradaon
101103105107109
5
10
15
Spec.
Warranty
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NTIdefined
AlamECE-606S09 6
n~0.25Ea~0.5eVAdependsonEox
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DiffusionDistance
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t1
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NITwithHdiffusion
AlamECE-606S09 8
NH
x
Combiningthesetwo,weget
SiSiSi H
HH
H
HH
H
Sisubstrate
Poly
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SiOonds
AlamECE-606S09 9
Broken Si-H bonds
Negative Bias Temperature Instability (NBTI)
Hot carrier degradation (HCI)
Broken Si-O bondsGate dielectric Breakdown (TDDB)
Electrostatic Discharge (ESD)
Radiation induced Gate Rupture (RBD)
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Outline
AlamECE-606S09 10
1. IntroducBon2. NegaBveiasTemp.Instability3. GateDielectricBreakdown4. RadiaBonInducedDamage5. Conclusion
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Time-dependentulkTrap
AlamECE-606S09 11
C/Cox
VG
IdealVT
ActualVT
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Dielectricreakdown
AlamECE-606S09 12
ln(Bme)GateCurrent reakdown
ln(-ln(1-F))
VG1>VG2>VG3 VDD64
20-2-4-6-8
-10
-20246810log(TBD)
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AnodeHoleInjecBonforDielectricreakdown
AlamECE-606S09 13
Anode
Cathode
e
h
NBD-DensityofpercolaBondefectsatbreakdown
Je-Electroncurrentdensity
a-ImpactIonizaBonRate(probabilitythataholewillbecreated
byanincomingelectron)
Tp-TransmissionRate(probabilitythattheholewilltravel
throughtheoxidelayer)
k-TrapGeneraBonEfficiency
(probabilitythattheholewillcreateapercolaBondefect)
OXIDE
JeaTpk
NBD
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AnodeHoleInjecBonTheoryofTDD
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Jh=JeTpJe=Aexp(-B/E) =1-2Tp~const
ln(TBD)~1/R~1/E
Je~f(E)~Mexp(DV)ln(TBD)~1/R~V
AB
V~low
B
A
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PercolaBonModelforDielectricreakdown
AlamECE-606S0915
M
P1=NC1[p
1][(1-p)(N-1)]
P1=() exp(-)
with=(t/)and=M
F1()=1-Po()
Prob.ofexactly1BD
Prob.ofafilledcolumn:p=qM
Prob.offilledcell:q=(ata/NM)
ln[-ln(1-F1)]~lnt
ln(-ln(1-F))
100/million
VG1>VG2>VG3 VDD
64
20-2-4
-6-8-10
-20246810log(TBD)
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Outline
AlamECE-606S0916
1. IntroducBon2. NegaBveiasTemp.Instability3. GateDielectricreakdown4. RadiaonInducedDamage5. Conclusion
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RadiaBonInducedDamage
AlamECE-606S0917
Geant4highenergyparBclephysicsbasedtoolkit
UsedfortheionizaBonandenergyrelaxaBon(~10eVkeVs)
177MeVClion50Mrad(Si)8MeVelec
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RadiaBonInducedChargeuildup
AlamECE-606S0918
C/Cox
VG
IdealVT
ActualVT
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Summary
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1) ReliabilityisaseriousconcernforscalingofMOSFETs.2) TherearemanydifferenttypesofdegradaBon
mechanismsthatneedscarefulmodelingtopredictthe
lifeBmeofaMOSFETs.
3) Atpresent,NTIinPMOStransistorsisthemostdifficultreliabilityproblem,followedbyHCI,TDD,andRadiaBon
effects.