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

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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

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

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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

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

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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

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

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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

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

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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

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

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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

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

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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

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

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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

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

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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

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

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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

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

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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

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