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Latent Noise in Schottky Barrier MOSFET UPoN 20081
Latent Noise in Schottky Barrier MOSFETLatent Noise in Schottky Barrier MOSFET
Sheng-Pin Yeh, Sheng-Pin Yeh, Chun-Hsing ShihChun-Hsing Shih*, Jeng Gong, and Chenhsin Lien*, Jeng Gong, and Chenhsin Lien
Institute of Electronics Engineering, National Tsing Hua University, Taiwan Institute of Electronics Engineering, National Tsing Hua University, Taiwan
*Department of Electrical Engineering, Yuan Ze University, Taiwan*Department of Electrical Engineering, Yuan Ze University, Taiwan
*Email: chshih@saturn.yzu.edu.tw*Email: chshih@saturn.yzu.edu.tw
UPoN 2008UPoN 2008
Latent Noise in Schottky Barrier MOSFET UPoN 20082
Latent Noise in Schottky Barrier MOSFETLatent Noise in Schottky Barrier MOSFET
Necessity of Metallic Source/DrainNecessity of Metallic Source/Drain
I-V Curves of SBMOSI-V Curves of SBMOS
Noise in SBMOS and MOSFET Noise in SBMOS and MOSFET
Latent Noise Mechanisms in SBMOSLatent Noise Mechanisms in SBMOS
SummarySummary
Latent Noise in Schottky Barrier MOSFET UPoN 20083
Necessity of Metallic Source/DrainNecessity of Metallic Source/Drain
Source: ITRS
Gate Length
SDE Depth
SDE Resistance
Xj
Rsd
Gate
S/D
Unacceptable SDE resistance will limit the use of impurity doped S/D
Latent Noise in Schottky Barrier MOSFET UPoN 20084
Recent Research of SBMOSRecent Research of SBMOS
Eliminating the limits on the dopant source/drain junctions makes metallic S/D SBMOS as one of the most attracting candidates for use in future CMOS devices.
Latent Noise in Schottky Barrier MOSFET UPoN 20085
Latent Noise in Schottky Barrier MOSFETLatent Noise in Schottky Barrier MOSFET
Necessity of Metallic Source/DrainNecessity of Metallic Source/Drain
I-V Curves of SBMOSI-V Curves of SBMOS
Noise in SBMOS and MOSFETNoise in SBMOS and MOSFET
Latent Noise Mechanisms in SBMOSLatent Noise Mechanisms in SBMOS
SummarySummary
Latent Noise in Schottky Barrier MOSFET UPoN 20086
SBMOS vs. MOSFET (Drain Current)SBMOS vs. MOSFET (Drain Current)
Gate
n+ Source
n+ Drain
Silicon Substrate
Gate Oxide
Conventional
MOSFET
Gate
Schottky Source
Schottky Drain
Silicon Substrate
Gate Oxide
SBMOS
Lg = 90 nm, Tox = 2.5 nm, SBH = 0.4 eV
SBMOS suffers from potential constraints on the drain currents because of its
unique Schottky barrier source/drain junctions.
Latent Noise in Schottky Barrier MOSFET UPoN 20087
SBMOS vs. MOSFET (Energy Band Diagrams)SBMOS vs. MOSFET (Energy Band Diagrams)
Gate
n+ Source
n+ Drain
Silicon Substrate
Gate Oxide
Gate
Schottky Source
Schottky Drain
Silicon Substrate
Gate Oxide
Vg= 0V
Vg= 1V
Vd= 1V
e-
SBMOS MOSFET
φBn
Vg= 0V
Vg= 1V
Vd= 1V
e-
In SBMOS, carriers can thermonicly emit over or laterally tunnel through Schottky barrier to contribute drain current. Unique Impact Ionization is observed in SBMOS.
SB Tunneling
Thermal Emission
Latent Noise in Schottky Barrier MOSFET UPoN 20088
Ambipolar Conduction Ambipolar Conduction
-1.0 -0.5 0.0 0.5 1.0 1.5 2.010-12
10-10
10-8
10-6
10-4
10-2
Dra
in C
urr
ent (
A/
m)
Gate Bias (V)
Lg = 90 nm, Tox = 2.5 nm
Vd = 1.0 V
φ Bn = 0.5 eV
φ Bn = 0 eV
φ Bp = 0.6 eV
φ Bp = 1.1 eV
SBMOS presents the ambipolar conduction as a function of gate voltage. At a negative bias, holes can also pass through the drain Schottky barrier, forming a hole channel, yielding an undesirable drain current. And, SBH must be minimized.
Latent Noise in Schottky Barrier MOSFET UPoN 20089
Dopant Segregated Schottky Barrier MOSFET (DS-SBMOS)Dopant Segregated Schottky Barrier MOSFET (DS-SBMOS)
SBMOS
Off-State (Vg = -0.5 V) On-State (Vg = 1.0 V)
Source
Drain
electron
hole
(Vd = 1.0V)
DS-SBMOS
```
DS-SBMOS
Schottky Source
Schottky Drain
Dopant Segregated Layer
Inserting a heavily doped segregation layer effectively modifies the Schottky barriers to increase the driving current and suppress the ambipolar behavior.
Latent Noise in Schottky Barrier MOSFET UPoN 200810
Interface States Generated during Metal SilicidationInterface States Generated during Metal Silicidation
φ Bn
Interface States EC
EF
EV
EFi Schottky Source Si
Vg
Electron
Si
Silicide
Interface
Metal
Metal Diffusion
Si
Si Diffusion
Metal
Si
Dopant Segregation
Metal
Dopant
Si
Drain
Formation of the metallic source/drain using silicidation brings about interface states and noise sources. Importantly, trap and detrap depend on Vg and SBH.
Hole
Latent Noise in Schottky Barrier MOSFET UPoN 200811
Latent Noise in Schottky Barrier MOSFETLatent Noise in Schottky Barrier MOSFET
Necessity of Metallic Source/DrainNecessity of Metallic Source/Drain
I-V Curves of SBMOSI-V Curves of SBMOS
Noise in SBMOS and MOSFETNoise in SBMOS and MOSFET
Latent Noise Mechanisms in SBMOSLatent Noise Mechanisms in SBMOS
SummarySummary
Latent Noise in Schottky Barrier MOSFET UPoN 200812
NoiseNoise in Conventional MOSFETs in Conventional MOSFETs
For MOSFETs For MOSFETs
Drain current fluctuates due to variations ofDrain current fluctuates due to variations of
Number of inversion charge density ∆Qi <traps in gate oxide>
(and number of inversion carriers in channel ∆N=WL∆ Qi)
Effective channel mobility ∆μeff <phonon scattering>
dsieffd VQL
WI
effeff
di
i
dd
IQ
Q
II
Oxide Traps
Source
Drain
e-
e- e
-
e-
e- e
-
e-
e-
e-
e- e
-
Scattering
Gate
Latent Noise in Schottky Barrier MOSFET UPoN 200813
Unique Noise in Schottky Barrier MOSFETUnique Noise in Schottky Barrier MOSFET
T. Asano, Jpn. J. Appl. Phys.,
2002, p. 2306.
NMOS, p-Si
Observations:
1. More Noisy in SBMOS than MOSFET
2. Unique noise observed in different metals silicidation SBMOS
(SBH: PtSi = 0.85 eV, NiSi = 0.65 eV for electron)
Latent Noise in Schottky Barrier MOSFET UPoN 200814
Unique Noise in Schottky Barrier MOSFET (Cont.)Unique Noise in Schottky Barrier MOSFET (Cont.)
M. V. Haartman, ICNF 2005, p. 307.
PMOS
Observations:
1. More Noisy in SBMOS (PMOS), SBH: NiSi = 0.45 eV for hole
2. Strong dependence of noise on gate bias
Latent Noise in Schottky Barrier MOSFET UPoN 200815
Latent Noise in Schottky Barrier MOSFETLatent Noise in Schottky Barrier MOSFET
Necessity of Metallic Source/DrainNecessity of Metallic Source/Drain
I-V Curves of SBMOSI-V Curves of SBMOS
Noise in SBMOS and MOSFET Noise in SBMOS and MOSFET
Latent Noise Mechanisms in SBMOSLatent Noise Mechanisms in SBMOS
SummarySummary
Latent Noise in Schottky Barrier MOSFET UPoN 200816
Noise Mechanisms in SBMOS: at Silicon SurfaceNoise Mechanisms in SBMOS: at Silicon Surface
Oxide Traps
Schottky Barrier
Source
Schottky Barrier
Drain
e- e-
e-
e- e-
e- e- e- e- e-
e-
Dopant Segregated Layer (If applied)
Scattering
Gate
φBn
Vg= 0V
Vg= 1V
Vd= 1V
e-
Mechanisms:
1. Number Fluctuation 1. Number Fluctuation <<traps in gate oxidetraps in gate oxide>>
2. Mobility Fluctuation 2. Mobility Fluctuation <<phonon scatteringphonon scattering>>3. But with unique impact ionization in Source3. But with unique impact ionization in Source
Latent Noise in Schottky Barrier MOSFET UPoN 200817
Noise Mechanisms in SBMOS: at SourceNoise Mechanisms in SBMOS: at Source
Schottky Barrier
Source
Gate
Mechanisms:
1. Trap levels in Schottky barrier contact
(SBH and Gate bias dependent)
2. Trap levels in substrate metallic Source contact
(SBH and substrate bias dependent)
3. Different in DS-SBMOS and SBMOS
φBn
InterfaceStates EC
EF
EV
EFiSchottkySource Si
Vg
SourceSource
Latent Noise in Schottky Barrier MOSFET UPoN 200818
Noise Mechanisms in SBMOS: at DrainNoise Mechanisms in SBMOS: at Drain
Mechanisms:
1. Trap levels in channel and substrate metallic (Schottky barrier) contact (SBH and bias dependent)
2. Noise generations in Drain is different to those in Source due to ambipolar conduction.
Source
e-
Source
e-
Drainh+
Drainh+
Schottky Barrier
Source
Schottky Barrier
Drain
Dopant Segregated Layer (If applied)
Gate
Surface channel
Latent Noise in Schottky Barrier MOSFET UPoN 200819
Noise Problems in SBMOSNoise Problems in SBMOS
Oxide Traps
Schottky Barrier
Source
Schottky Barrier
Drain
e- e-
e- e- e-
e- e- e- e- e-
e-
Drain
e-
Source Impact Ionization
e-
Source
e-
Source
e-
Drainh+
Drainh+
Dopant Segregated Layer (If applied)
III
III
IV
IV
I
I
V II
II V
SourceSource
(If no DS layer) (If no DS layer)
Schottky barrier MOSFET
Conventional MOSFET
Drain
Latent Noise in Schottky Barrier MOSFET UPoN 200820
SummarySummary
Eliminating the limits on the dopant junctions makes SBMOS as one of Eliminating the limits on the dopant junctions makes SBMOS as one of
the most attracting candidates for future CMOS devices, while the most attracting candidates for future CMOS devices, while SBMOS SBMOS
suffers from potential suffers from potential problemsproblems onon its unique Schottky barrier junctions its unique Schottky barrier junctions..
Schottky barrier MOSFETs present particular ambipolar conduction as Schottky barrier MOSFETs present particular ambipolar conduction as
a function of gate voltage.a function of gate voltage.
Formation of the metallic source/drain using metals silicidation brings Formation of the metallic source/drain using metals silicidation brings
about interface states and noise sources.about interface states and noise sources.
Unique noises in SBMOS were observed. Proposed noise mechanisms in Unique noises in SBMOS were observed. Proposed noise mechanisms in
SBMOS are presented. SBMOS are presented.
Proper noise behavior and mechanisms in SBMOS require further Proper noise behavior and mechanisms in SBMOS require further
thorough investigations.thorough investigations.
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