hotcarriereffectshot carrier effects - cbnubandi.cbnu.ac.kr/~ysk/hotcarrier.pdf · 2011. 9. 22. ·...
TRANSCRIPT
![Page 1: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/1.jpg)
Hot Carrier EffectsHot Carrier Effects
충북대학교 전자정보대학 김영석
2 11 92011.9
1
![Page 2: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/2.jpg)
Moor’s LawIC complexity roughly doubles every 2 years” Gordon Moore, 1965
Higher Density
But, Hot Carrier Effects
2전자정보대학 김영석
![Page 3: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/3.jpg)
ScalingDennard (IBM) in 1974
Constant Electric Field Scaling
3전자정보대학 김영석
![Page 4: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/4.jpg)
ScalingThreshold Voltage VTH
V
CQ
VVVox
depFFBoxsiFBTH
+
−++=Δ+Δ+=
)2(2
2
εφε
φφφ
VqNCQ
tCWqNQ
qNVW
SBFsubsidep
ox
oxoxdepsubdep
sub
SBFsidep
+=
−
==−+
=
/)2)((2
,,)2(2
φε
εφε
kV
tkkVqkN
VV
tC
TH
oxox
SBFsubsisiFBTH
oxoxox
=+
+Δ+≈/
)/2)((2:scalingafter
/
'
εφε
φ
ε
Drain Current
D l
kIkVkV
kLkWkCI D
THGSoxnD =−≈ 2' )//(//)(
21 μ
WLCCVC GSGS 2Delay
kkIkVkC
WLCCI
D
GSGS
oxGSD
GSGS
ττ
τ
==
≈=
/)/)(/(
3,
'
Power Consumption
' )/)(/( PkVkIP DD ==
4
2)/)(/(k
kVkIP DD
전자정보대학 김영석
![Page 5: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/5.jpg)
MOSFET ReviewCross-section
Depletion
0 < VGS < VTH
S bth h ld tSubthreshold current
Inversion
VGS >= VTHVGS > VTH
5전자정보대학 김영석
![Page 6: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/6.jpg)
MOSFET: ID @ InversionLinear Region
ID ~ VDS
Voltage controlled resistor (VGS)
Pi h ffPinch-off
VDS=VDSAT
Saturation RegionSaturation Region
VDS => Leff slowly
Vchannel=VDSAT=const
Pinch-off section absorbs (VDS-VDSAT), high-field region, electron velocity saturationvelocity saturation
HCI
Large lateral electric field
Population of high-energy electrons
6전자정보대학 김영석
![Page 7: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/7.jpg)
Scaling => 채널길이 감소Lateral E-field (drain) 증가 (>100kV/cm)=> Hot-Carrier 발생 (E>1.5eV)
Impact Ionization(I/I) or Avalanche Breakdown
Isub 증가 => 기판전압증가, Snapback 발생
I 증가 > O id T / VT 증가Ig 증가 => Oxide Trap/ VT 증가
Hot Carrier Effects(HCI)
7전자정보대학 김영석
![Page 8: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/8.jpg)
Substrate Currents Mechanism
Electron Energy > 1.5eV
=> Impact Ionization
> El t H l i ti=> Electron-Hole pair generation
전자는 드레인 or 게이트로 이동
정공은 기판으로 이동 (Isub)정공은 기판으로 이동 (Isub)
Isub can be used to predict the device lifetime
8전자정보대학 김영석
![Page 9: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/9.jpg)
Substrate Currents Difference between Electrons and Holes: pn μμ ⋅≈ 3
Electron-Hole pair generation by Electrons: Energy>1.8eV
Electron-Hole pair generation by Holes: Energy>2.4eV
p
9전자정보대학 김영석
![Page 10: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/10.jpg)
Substrate Currents(Isub) 문제점Breakdown 발생: 정공 기판으로 이동 => 기판 전압 상승 => 소스-기판 순방향바이어스 => 소스에서 전자들이 기판으로 방출 (기생 npn BJT동작) => More I/I => Snapback Breakdown
CMOS Latch-Up 유발CMOS Latch Up 유발
Back Bias Generator 전압을 올림
드레인-기판 공핍영역에서 정공에 의한 Secondary Impact-Ionization 발생
A monitor to correate device degradation with lifetime
Device Degradation/Isub are driven by a common source: Emax
10전자정보대학 김영석
![Page 11: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/11.jpg)
Hot-Carrier Injection into Gate Oxide 게이트 산화막으로 주입된 대부분의 전자들은 게이트 전극으로 이동 ( 약 fA - pA).
이중 1/1E6 정도의 전자들은 게이트 산화막에 trap됨
Negative Charge => VT 증가 => 전류감소
11전자정보대학 김영석
![Page 12: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/12.jpg)
Nature of Gate Oxide DamageHCI increases with shrinking
L , xj , tox , Nsub => E(lateral), E(vertical) (sinificant)
HCI
2 D O id h t i I t f t ti2 Damages: Oxide charge trapping, Interface trap generation
Very localized
gm , VTH , IDgm , VTH , ID
Charge-Pumping technique
Provide amount of Oxide charge trapping/Interface trap generation even for the case of Localized degradation
2 Voltage Regions
VDS ~ 2VGS: Max substrate current Interface trap generationVDS ~ 2VGS: Max substrate current, Interface trap generation (no Oxide charge trapping)
VDS ~ VGS: Hot electron injection into oxide, Oxide charge trapping (Less Interface trap generation)
12전자정보대학 김영석
![Page 13: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/13.jpg)
HCI into Gate Oxide Hot Carrier
Carriers that have a much higher kinetic energy than the average carrier population
E-Ec=kTe >> kTE-Ec=kTe >> kT
2 Modes of Electron Injection
Substrate Hot-Electron (SHE)
Channel Hot-Electron (CHE)
13전자정보대학 김영석
![Page 14: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/14.jpg)
HCI into Gate Oxide : SHESubstrate Hot-Electron due to Substrate leakage Current
Electrons generated in the depletion region
Drift toward Si-SiO2 interface
G i h ki tiGain enough kinetic energy
Overcome the energy barrier (3.1eV)
Injected into the gate oxideInjected into the gate oxide
Some trapped in the Oxide
Uniform Oxide Charge Accumulation => VTH
Primarily in Long-Channel MOSFET
14전자정보대학 김영석
![Page 15: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/15.jpg)
HCI into Gate Oxide : CHEChannel Hot Electrons are caused by Electrons flowing in the channel
Short Channel => SHE (Larger fraction of SHE are swept into S/D instead of the surfaceinstead of the surface
Pronounced at Large VDS
Hot Electrons in the Drain end of channel due to High Electric Field
Also Electron-Hole Pairs by Impact Ionization
Localized near the Drain Junction
15전자정보대학 김영석
![Page 16: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/16.jpg)
HCI into Gate Oxide : Injected Electron Current Density
Injected Electron Current Density
∫=y
inje dyyxPyxnxj ),(),()(
N(x,y) : Local electron contration
Pinj(x,y) : Spatial distribution of the injection probabilityPinj(x,y) : Spatial distribution of the injection probability
16전자정보대학 김영석
![Page 17: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/17.jpg)
Lucky Electron Model: scattering probabilitiesScattering Events
A to B: Channel Electrons gain kinetic energy from the lateral channel electric field
B: The Momentum of the hot electron must be redirected towardB: The Momentum of the hot electron must be redirected toward the interface by a Quasi-Elastic Collision
• No energy-robbing collision
• Retain the kinetic energy
B to C: Travel without suffering further collisions
17전자정보대학 김영석
![Page 18: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/18.jpg)
Lucky Electron Model: scattering probabilitiesScattering Probabilities
P1: the probability of the electron to gain a kinetic energy sufficient to overcome the effective potential barrier at the interface
bΦinterface
path freemean scattering: where//1 −== Φ−− λλλ xb Ed eeP
P2: the probability of an electron with initial kinetic energy of being redirected toward the interface
Φ
]1[21
2 ΦΦP b−=
By integrating the product
P1 and P2 over all energies
Φ
λλxb
b
EΦ
b
xΦ e
ΦEP /
41 −=
18전자정보대학 김영석
![Page 19: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/19.jpg)
Lucky Electron Model: scattering probabilitiesScattering Probabilities – continued
Ped: the probability of travelling to the interface without further collisions
Poc: oxide scattering factor (electrons scattered in the image-
λ/yed eP −=
Poc: oxide scattering factor (electrons scattered in the image-potential-well above the oxide interface must be excluded)
oxyoc eP λ/0−=
Pinj(Eox) : the overall probability that a hot-electron can enter the gate oxide by overcoming the potential barrier (empirical)
ηγα
+++
=− ]1[
1
]1[ 5.1/oxoxtEox
oxinj
eEEP
β++ ]1[]1[
eff
eL
19전자정보대학 김영석
![Page 20: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/20.jpg)
Lucky Electron Model: Injection Current ModelInjection Current
Region A: Electrons are attracted toward the gate
Region B/C:
El t ll d f th idElectrons are repelled from the oxide
But, More electrons are injected due to Larger lateral E-field and so more hot electrons
exp)(21
2
⎥⎦
⎤⎢⎣
⎡ Φ−⎥
⎦
⎤⎢⎣
⎡Φ
= boxinj
moxDSei E
EPEtIiλ
λλ
pathfreemeandirection re theis where2
−−−
⎥⎦
⎢⎣
⎥⎦
⎢⎣ Φ
r
mj
br Eλ
λλ
ηγα
+=1
51/E
oxinj E
EP γβ
++ − ]1[]1[ 5.1/oxoxtE
eff
ox eL
E
20전자정보대학 김영석
![Page 21: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/21.jpg)
Lucky Electron Model: SummaryLucky Electron Model
eVeIIII
i
chsubchGi
6.1~energy thresholdionization:/~/ /
Φ
ΦΦ−
V2.3~energybarrier injection :Φ
21전자정보대학 김영석
![Page 22: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/22.jpg)
Lucky Electron Model: Measurement resultsSimulation results (right figure)
Solid: without oxide scattering factor Poc
Dashed: with oxide scattering factor Poc
M t (l ft fi )Measurements (left figure)
22전자정보대학 김영석
![Page 23: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/23.jpg)
CHE/DAHCChannel hot electron(CHE) injection
Drain avalanche hot carrier(DAHC) injection => Impact Ionization
23전자정보대학 김영석
![Page 24: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/24.jpg)
Impact Ionization by Hot-ElectronsElectrons are accelerated by the E-field
Get sufficient energy to break the covalent bond
Impact-Ionization=Avalanche Breakdown
I b li bl d i t it f th t f h tIsub: a reliable and convenient monitor of the amount of hot-carrier degradation
24전자정보대학 김영석
![Page 25: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/25.jpg)
Impact Ionization by Hot-Electrons
Isub ~ IDS * Pi
Pi = the probability of an electron travelling a sufficient distance to gain the kinetic energy or more without suffering a collision
E/Φ λiΦ
eVeP
i
Eqi
mi
6.1~energy ionizationimpact : where
/
Φ= Φ− λ
Substrate current
mi EqDSsub eICI λ/
1Φ−= DSsub 1
25전자정보대학 김영석
![Page 26: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/26.jpg)
Fowler-Nordheim (FN) TunnelingPrimarily by Eox
Localized at the source (maximum Eox at the Source)
⎟⎟⎞
⎜⎜⎛ −
= CEJ βexp2
Nonsignificant (But Significant for very thin oxide)
⎟⎟⎠
⎜⎜⎝
=ox
oxT ECEJ exp
Nonsignificant (But Significant for very thin oxide)
26전자정보대학 김영석
![Page 27: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/27.jpg)
Oxide Traps and Charge TrappingSi-SiO2 system : 4 Charges
Fixed Oxide Charge
Structural defect
R l t d t th l id ti (T li diti SiRelated to thermal oxidation process (T, cooling conditions, Si Orientation)
Mobile Oxide chargeg
Ionic impurities Na+ K+
Oxide trapped charge / Interface trapped charge : Important role i th d i d d ti d t HCIin the device degradation due to HCI
27전자정보대학 김영석
![Page 28: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/28.jpg)
Fixed oxide chargeSi-SiO2 atomic model
Si dangling bond
Oxygen dangling bond
B th d li b d l t /h l TRAPBoth dangling bond : electron/hole TRAP
SiN : nitrogen dangling bond
28전자정보대학 김영석
![Page 29: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/29.jpg)
Interface Trap GenerationInterface states=surface states=fast states Nit
Structural, oxidation-induced defects
Metal impurities, Radiation
L li d t th i t fLocalized at the interface
Charged and discharged depending on the surface potential
Depend on bias conditionsDepend on bias conditions
In case of acceptor-like interface states
Neutral when empty
Negatively charged when filled
Atomic mechanisms for creation of interface states by hot electron and holes [sah]and holes [sah]
Breaking the strained Si-Si or Si-O bonds creating oxide traps
Breaking the hydrogen bonds, release H atom, leaving behind dangling Si- or O-bond
Hydrogen is trapped by proton trap => reduction of the interface trapsinterface traps
29전자정보대학 김영석
![Page 30: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/30.jpg)
Bias Dependence of Degradation MechanismsOxide Degradation
Oxide Charge Trapping
Interface Charge Trapping
Ch f D i h t i ti d t id dChange of Device characteristics due to oxide damage
gm decrease
VTH increaseVTH increase
VTH decrease versus VGS shows Two local Maxima => One at VGS=VDS, another at VGS=VDS/2
VTH decrease vs time shows Two different slopes for VGS=VDS and VGS=VDS/2
30전자정보대학 김영석
![Page 31: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/31.jpg)
Bias Dependence of Degradation MechanismsVGS=VDS/2
Maximum substrate current
Injection of Impact Ionization Electrons/Holes
I t f T G tiInterface Trap Generation
A depends on Isub and IDS
7.05.0 −=⋅=Δ nwheretAV nTH
A depends on Isub and IDS
VGS=VDS
Maximum Ig
Oxide Charge Trapping
2.0 =⋅=Δ nwheretBV nTH
Hole injection
Ig(electron) >> Ig(hole)eVeV holeelec 5.4~,2.3~ ΦΦQ
Ig(electron) Ig(hole)
But, (Interface trap generation by holes) ~ 1000*(Interface trap generation by electrons)
31전자정보대학 김영석
![Page 32: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/32.jpg)
Degradation under Dynamic Stress ConditionsIn a circuit, MOSFET devices usually operate under dynamic operating conditions
Degradation under dynamic stress > Degradation under static stress for large VDSstress for large VDS
Sublinear dependence
Why? Increased interface trap generation by hot holes
Model: two-step hole/electron injection process
Oxide trap generation by holes (>4.6eV)
Ch d iti l b h lCharged positively by holes
Some positive trapped charge located close to the interface tunnels back to Si
Some positive trapped charge not close to the interface just stay there
C t s i j t d l t sCaptures injected electrons
Create negative charged interface states
Hole trap increasesHole trap increases
32전자정보대학 김영석
![Page 33: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/33.jpg)
Degradation under Dynamic Stress ConditionsUnder static stress conditions
VDS,VGS constant
Trapped holes stay there (not return to the substrate)
E fi ld d ll dE-field gradually decreases
Rate of degradation drops
Under Dynamic stress conditionsUnder Dynamic stress conditions
VGS changes
Trapped holes tunnel back to the si
E-field not change
Enhanced carrier injection => degradation increases
33전자정보대학 김영석
![Page 34: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/34.jpg)
Degradation under Dynamic Stress ConditionsDynamic degradation is larger when hole injection occurs
For larger VDS(>7V), smaller VGS(~2V)
Hole injection is dominant by oxide E-field
D i d d ti i dDynamic degradation is pronounced
For lower VDS(E<6MV/cm)
Electron injection is dominant by oxide E-fieldElectron injection is dominant by oxide E field
Dynamic degradation negligible
34전자정보대학 김영석
![Page 35: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/35.jpg)
Degradation under Dynamic Stress ConditionsVGS, VDS < 5V (Hole injection not dominant)
Static = Dynamic degradation
Dominant degradation mechanism is interface trap generation by hot holes
No significant dynamic degradation for current ICs because VGS, VDS<5V, so hole injection is not dominant
35전자정보대학 김영석
![Page 36: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/36.jpg)
Threshold Voltage Shift
0@FGpp VVQCVV + 0@
FGTHiTH
DSoxpp
FG
oxpp
ppCGFG
QVV
VVCC
QCC
VV
−=
==+
++
=
)22(2 0 FFSBTHdep
FFBTHi
oxppTHiTH
VVCQ
VV
CCVV
φφγφ −++=−+=
+
)(0 FFSBTHox
FFBTHi Cφφγφ
36전자정보대학 김영석
![Page 37: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/37.jpg)
CharacterizationVFG 영향
A region: Electrons(Ich) 증가 => I/I 증가
B region: Emax 감소 => I/I 감소
VD 영향VD 영향
VD 증가 => Emax 증가 => I/I 증가
Leff 영향Leff 영향
Leff 감소 Emax 증가 => I/I 증가
37전자정보대학 김영석
![Page 38: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/38.jpg)
CharacterizationISUB vs VD
VTH vs time
Lifetime vs ISUB
38전자정보대학 김영석
![Page 39: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/39.jpg)
Device DegradationHCI
=> VTH 감소, 전류 IDS 감소, gm 감소
=> Circuit Speed 감소
> Ci it F il=> Circuit Failure
39전자정보대학 김영석
![Page 40: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/40.jpg)
Device LifetimeIn General, Device Lifetime is defined by
%3
10
=Δ
=Δ
D
T
II
mVV
%3=Δ m
D
ggI
mg
40전자정보대학 김영석
![Page 41: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/41.jpg)
Techniques to Reduce HCIReduce Maximum Electric Field (Emax)
Reduce VDD
Gate Oxide Engineering for higher reliability (e.g., oxynitrides)
St t t t th t th f EStructure to separate the current path from Emax
41전자정보대학 김영석
![Page 42: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/42.jpg)
LDD(Lightly Doped Drain)Hot Carrier Effect 방지를 위한 소자 구조
LDD(Lightly Doped Drain)
42전자정보대학 김영석
![Page 43: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/43.jpg)
SummarySubstrate Current by Impact Ionization
G t C t b L k El t
(1) /1
mi EqDSUB eICI λϕ−=
Gate Current by Lucky Electrons
(2) /2
mb EqDG eICI λϕ−=
(1)+(2)
(3))( / ibSUBG II ϕϕ∝ (3) )( ib
D
SUB
D
G
IIϕϕ∝
oxide barrier toenergy :2.3IonizationImpact create energy to :3.1
eVeV
b
i
==
ϕϕ
43전자정보대학 김영석
![Page 44: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/44.jpg)
SummaryDevice Lifetime by Interface Traps (IG, ISUB)
eIWC Eq
D
mit /5
(4)(1)
(4) =τ λϕ
II
IW SUB iit / (5) )(
(4)(1)
∝
+
−τ ϕϕ
WII
II
SUB
D
DD
9.2
9.1
∝∴τSUB
TI t ftt73 V
44
TrapsInterfacecreateenergy to :7.3 eVit =ϕ
전자정보대학 김영석
![Page 45: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/45.jpg)
SummaryLifetime: Ex
AI
mWAIAI
SUB
SUBD
/103
60,10,10
129.2
64 ===
−
−− μ
years
mAWID
SUB
31sec101
/103
9
129.1
=×≈∴
×≈
τ
μ
Note that Li-Ion battery: 2 years, 400회
45전자정보대학 김영석
![Page 46: HotCarrierEffectsHot Carrier Effects - CBNUbandi.cbnu.ac.kr/~ysk/HotCarrier.pdf · 2011. 9. 22. · HotCarrierEffectsHot Carrier Effects 충북대학교전자정보대학김영석](https://reader036.vdocuments.mx/reader036/viewer/2022071405/60f9e8634de3c94f6073f19a/html5/thumbnails/46.jpg)
ReferencesHot Carrier Design Considerations for MOS Devices and Circuits, C. T. Wang, Van Nostrand Reinhold, 1992
Hot-Carrier Reliability of MOS VLSI Circuits, Y. Leblebici and S. M. Kang, Kluwer Academic Publishers, 1993Kang, Kluwer Academic Publishers, 1993
46전자정보대학 김영석