Influence of ultra-thin gate oxide on the Influence of ultra-thin gate oxide on the electric performance and low frequency electric performance and low frequency
noise of sub -0.1µm NMOSFETsnoise of sub -0.1µm NMOSFETs
M. FadlallahM. Fadlallah1,31,3, G. Ghibaudo, G. Ghibaudo11, J. Jomaah, J. Jomaah1 1 andand G. Guégan G. Guégan22
1)IMEP/LPCS, ENSERG, BP 257, 38016 Grenoble, France1)IMEP/LPCS, ENSERG, BP 257, 38016 Grenoble, France2) CEA/LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9, 2) CEA/LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9,
FranceFrance3) LAM UFR Sciences, Moulin de la Housse, BP 1039, 51687 3) LAM UFR Sciences, Moulin de la Housse, BP 1039, 51687
Reims cedex 2Reims cedex 2
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
OUTLINEOUTLINE IntroductionIntroduction Static performanceStatic performance
Short Channel effectShort Channel effect Extraction method parameterExtraction method parameter
Low frequency noiseLow frequency noise 1/f low frequency noise1/f low frequency noise Ohmic mode Ohmic mode Saturation modeSaturation mode
Influence of the gate currentInfluence of the gate current ConclusionConclusion
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
INTRODUCTIONINTRODUCTION
OBJECTIVEOBJECTIVE : Ultimate CMOS devices (channel lenght<50nm : Ultimate CMOS devices (channel lenght<50nm & oxide thickness below 1nm)& oxide thickness below 1nm)
Many problems related to the channel length shortening and Many problems related to the channel length shortening and ultra-thin gate oxideultra-thin gate oxide
1/f noise reinforced with channel length reduction and ultra-1/f noise reinforced with channel length reduction and ultra-thin oxidethin oxide
High gate currentHigh gate current
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
STATIC PERFORMANCESTATIC PERFORMANCE
-0.5 0 0.5 1 1.5 2
1.10-4
gm (A
/V)
1.10-11
2.10-4
3.10-4
4.10-4
5.10-4
6.10-4
NMOS VD=0.05V W=10µm
Id (A
)
Vg (V)
L(µm) = tox=1.2nm
0.055
0.065
0.1
0.15
0.175
0.35
0.5
1
Typical Id & gm vs Vg transfer characteristics
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
STATIC PERFORMANCESTATIC PERFORMANCE Extraction of the main static MOSFET parameter using Y function Extraction of the main static MOSFET parameter using Y function
NMOS(1.2nm)NMOS(1.2nm) ttoxox=1.2nm=1.2nm
W(µm)W(µm) 1010
L(µm)L(µm) 55nm-1µm55nm-1µm
(V(V-1-1)) 0.330.33
L(µm)L(µm) 0.0240.024
µµ00(cm(cm22/Vs)/Vs) 182182
RRSDSD(()) 159159
mdg gIVY )(
The Y function is independent of :The Y function is independent of :Mobility attenuation factor Mobility attenuation factor Series resistance of drain and sourceSeries resistance of drain and source
Extraction of Vt and Gm using the Extraction of Vt and Gm using the linear part of Ylinear part of Y
0
2.10 -3
4.10 -3
6.10 -3
8.10 -3
1.10 -2
1,2.10-2
1,4.10-2
1,6.10-2
0 0.2 0.4 0.6 0.8 1 1.2 1.4
L(µm)= 0.0750.10.1750.250.51
VD=0.05V W=10µm
Vg (V)
Y f
unct
ion
- (
AV
)1/2
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
STATIC PERFORMANCESTATIC PERFORMANCE
Charge sharing effect : we can Charge sharing effect : we can not neglect the part of charge not neglect the part of charge controlled by the drain and controlled by the drain and source junction with respect source junction with respect to the gateto the gate
Reduction of the threshold Reduction of the threshold
voltage at small gate lengthvoltage at small gate length 0.35
0.45
0.55
0.65
0.75
0.85
0.95
0 2.10-5 4.10-5 6.10-5 8.10-5 1.10-4 1,2.10-4
L (µm)Vt
(V)
NMOS
VD=0.05V
tox=1.2nm
W=10µm
Variation of the threshold voltage
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
STATIC PERFORMANCESTATIC PERFORMANCE Drain Induced Barrier Lowering (DIBL)Drain Induced Barrier Lowering (DIBL)
For a MOSFET with short channel => Important penetration of electric field from the drain towards source
The barrier potential at source reduces due to the influence of drain bias
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
STATIC PERFORMANCESTATIC PERFORMANCE
DIBL EFFECTDIBL EFFECT
Variations of DIBL coeficient
DIBL=dLog(Id)/dVd 0.01
0.1
1
1.10-6 1.10-5 1.10-4 1.10-3
L (µm)
NMOS
tox=1.2nm
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LOWLOW FREQUENCY NOISE FREQUENCY NOISE 1/f noise : 1/f noise : TwoTwo principle models principle models
Carrier number fluctuations (Mc Whorter) Hole trapping Flat band voltage spectral density Correlated mobility fluctuations
fWLC
NkTqS
g
ICµS
I
g
I
S
ox
tVFB
m
doxeffVFB
d
m
d
Id
2
2
2
2
2
21
: tunnelling constant (0.1nm)
Nt : slow oxide trap density (/eV/cm3): Vs/CSVFB : flat band voltage spectral density
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LOW FREQUENCY NOISELOW FREQUENCY NOISE
1/f noise : 1/f noise : TwoTwo principle models principle models
Mobility fluctuations (HOOGE)Empiric (h=10-3-10-7) depend of the quality of devices N : total carrier number
fNI
fSh
d
Id 2
)(
d
deffh
d
Id
IfL
V
I
fS22
)(
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LOW FREQUENCY NOISELOW FREQUENCY NOISE 1/f noise due to carrier number fluctuations1/f noise due to carrier number fluctuations Oxide trap density Nt=Oxide trap density Nt=1.101.101717-5.10-5.1017 17 /eVcm/eVcm33
Id (A)
SId
/Id2
10 -6
10 -8
10 -10
10 -12
10 -3
10 -4
10 -5
10 -6
10 -7
10 -8
NMOS tox =1.2nm W=10µm
L(µm)= 0.5, 0.175, 0.1, 0.075
Variations of the normalized drain current noise SId/Id2 (symbols) and corresponding (gm/Id2) (solid line) with drain current Id
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LOW FREQUENCY NOISELOW FREQUENCY NOISE Variation of SVariation of Svgvg
1/21/2(V/Hz(V/Hz1/21/2) with gate voltage drive (V) with gate voltage drive (Vgg-V-Vtt) for extraction of ) for extraction of
coulomb scattering coefficient coulomb scattering coefficient
0 0.2 0.4 0.60
1 106
2 106
3 106
4 106
(Vg -Vt ) (V)
Svg
1/2
NMOS tox=1.2nm
L = 0.5µm, W=10µm
Vd = 50mV
YC
X
OX .. 0
X
Y
20oxVfbVg VtVg.C.1SS
fCLW
NkTqS
2ox
t2
Vfb
NMOS(1.2nm)NMOS(1.2nm) ttoxox=1.2nm=1.2nm
W(µm)W(µm) 1010
L(µm)L(µm) 55nm-1µm55nm-1µm
NNtt(ev(ev-1-1cmcm-3-3)) 1.101.101717-5.10-5.101717
(V.S/C)(V.S/C) 1.101.1044
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
LOW FREQUENCY NOISELOW FREQUENCY NOISE 1/f noise : Saturation mode1/f noise : Saturation mode
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.81.10-11
1.10-10
1.10-9
1.10-8
NMOS tox =1.2nm W=10µm
Vd (V)
L(µm)= 0.5
Vg = 1.1 v
Vg = 0.95 v
(gm/Id)2
SId/Id2
SId
/Id2 (
/Hz)
1.10-10
1.10-9
1.10-8
1.10-7
0 0.5 1 1.5 2
SId
/Id2
(/H
z)
NMOS tox =1.2nm W=10µm
Vd (V)
L(µm)= 0.175
Vg = 1 v
Vg = 0.838 v
(gm/Id)2
SId/Id2
The Good correlation between SId/Id2 (symbols) & (gm/Id)2 confirms that the sources of 1/f noise of these devices are the carrier number fluctuations due to electron trapping in the oxide
Nt values extracted in saturation confirm those obtained in the linear regime
LAM
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M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
INFLUENCE OF THE GATE CURRENTINFLUENCE OF THE GATE CURRENT
the impact of the gate current the impact of the gate current relatively high proved to be relatively high proved to be critical for advanced devicescritical for advanced devices
the ultra-thin gate oxide is not the ultra-thin gate oxide is not harmful for the functionality of harmful for the functionality of devices in static terms and 1/f devices in static terms and 1/f noisenoise -0.5 0 0.5 1 1.5 2 2.5
1.10-14
1.10-13
1.10-12
1.10-11
1.10-10
1.10-9
1.10-8
1.10-7
1.10-6
1.10-5
1.10-4
1.10-3
Id (
A)
NMOS
VD=0.05V W=10µm
Vg (V)
0.5
0.25
0.175
0.15
0.1
0.065
0.055
L(µm) =
tox=1.2nm
0.5
0.055
gate curent (A)
1.10-2
1.10-1
1.100
-0.5 0 0.5 1 1.5 2 2.51.10-14
1.10-13
1.10-12
1.10-11
1.10-10
1.10-9
1.10-8
1.10-7
1.10-6
1.10-5
1.10-4
1.10-3
Id (
A)
NMOS
VD=0.05V W=10µm
Vg (V)
0.5
0.25
0.175
0.15
0.1
0.065
0.055
L(µm) =
tox=1.2nm
0.5
0.055
gate curent (A)
Id (
A)
NMOS
VD=0.05V W=10µm
Vg (V)
0.5
0.25
0.175
0.15
0.1
0.065
0.055
L(µm) =
tox=1.2nm
0.5
0.055
gate curent (A)
1.10-2
1.10-1
1.100
LAM
ULIS’03
M.FADLALLAH et al. Influence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETsInfluence of ultra-thin gate oxide on the electric performance and low frequency noise of sub -0.1µm NMOSFETs
CONCLUSIONSCONCLUSIONS Output transfer characteristicsOutput transfer characteristics
1/f noise in linear and saturation modes1/f noise in linear and saturation modes
the source of 1/f noise is always due to the carrier number with the source of 1/f noise is always due to the carrier number with correlated mobility fluctuationscorrelated mobility fluctuations
The slow oxide trap density deduced in linear and saturation The slow oxide trap density deduced in linear and saturation modes is a good indication of the quality of ultra-thin dielectricmodes is a good indication of the quality of ultra-thin dielectric
the ultra-thin gate oxide is not harmful for the functionality of the ultra-thin gate oxide is not harmful for the functionality of devices in static terms and noisedevices in static terms and noise
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