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Ultimate Device Scaling: Intrinsic Performance Comparisons of Carbon-
based, InGaAs, and Si Field-effect Transistors for 5 nm Gate Length
Mathieu Luisier1, Mark Lundstrom2, Dimitri Antoniadis3, and Jeffrey Bokor4
1ETH Zurich, 2Purdue University, 3MIT, and 4University of California at Berkeley
• Motivation
• Simulation Approach Models and Validation
• General Scaling Considerations Band-to-band Tunneling
Electrostatics and Contacts
Source-to-drain Tunneling
• Performance Comparisons
• Conclusion and Outlook
Outline
Motivation: Future of Moore’s Law
65nm (2005)
45nm (2007)
32nm (2009)
22nm (2011)
5nm (2020)
??Source: Intel Corporation
1. 3-D Si FinFETs for ever?
2. What will be the dominant limiting factors when Lg<10nm?
Gate Length Reduction in planar Si MOSFETs:=> increase of short-channel effects (SCE)=> poor electrostatic control (single-gate)
Gate Length Reduction in planar Si MOSFETs:=> increase of short-channel effects (SCE)=> poor electrostatic control (single-gate)=> SOLUTION: 3-D FinFET since 2011
Leakage Sources in Ultrascaled Devices
IBT/S-to-D
BTBT1
BTBT2
HIBL
Band Diagram of Lg=5nm Nano-transistor
How can we minimize leakage?
Best device structure at Lg=5nm:The least sensitive to leakage
P. Hashemi et al., EDL 30, 401 (2009)
L. Tapasztó et al., Nat. Nano. 3, 397 (2008)
Y.Q. Wu et al., EDL 30, 700 (2009)
Nanowire Graphene III-V UTB CNT
NEEDED: Fast, cheap, and reliable platform to investigate the performance of next-generation ultrascaled nano-transistors beyond 3-D FinFETs
Supratik Guha, IBM Research
More Features
Simulation Capabilities
Efficient Parallel Computing
• 3D Quantum Transport Solver• Different Flavors of Atomistic
Tight-Binding Models• Multi-Physics Modeling: From
Ballistic to Dissipative (e-ph) Electron/Hole
Transport
• Industrial-Strength Nano-electronic Device Simulator
• Multi-Geometry Capabilities • Investigate Performance of
Ultra-Scaled Nano-Devices before Fabrication
• Schrödinger-Poisson Solver with NEGF and WF
• Finite Element Poisson• Accelerate Simulation Time
through Massive and Multi-Level Parallelization
8Donnerstag, 20. April 2023
State-of-the-art Nano-TCAD Tool
Physical Models
Si Bandstructure
TB: sp3d5s*
OMENBias
Momentum
Energy
Space
Model Verifications
Expt: J. del Alamo @ MIT Expt: A. Franklin @ IBM YH Expt: S. Rommel @ RIT S. Datta @ PSU
III-V HEMT CNT FET BTBT Diode
Zener Current
NDR Current
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Id-Vgs at Vds=0.5 V in Carbon Devices
AGNR width: 2.1 nm / CNT diameter: 1.49 nm / Band Gap Eg=0.56 eV
Observations:•same EOT gives very different electrostatic gate-channel coupling•as long as Eg>Vds, BTBT remains weak, but still intra-band tunneling
SiO2
EOT=0.64nm
HfO2
EOT=0.64nm
BTBT
HIBL/IBT
Intra-Band Tunneling: Electrostatics
Spectral current through GAA CNT FETs with d=1.49 nm, Eg=0.563 eV, different dielectrics, and EOT=0.64 nm
Fringing Fields:
•stronger when spacer with large εR
•effective channel length is longer•same effect as gate underlap doping
Intra-Band Tunneling: Material (1)
Fix electrostatic potential (Gaussian-like barrier)Investigate how semiconductor properties influence IBT
CNT d=1nmEg=0.817eV
Si NW d=3nmEg=1.404eV
Id=4.4nA
Id=91nA• Smaller band gap (and m*) gives higher intra-band tunneling current
• Need to understand why
OBSERVATIONS:•Current flows through the potential barrier, almost no thermionic component
Intra-Band Tunneling: Material (2)
What is needed: Under-the-Barrier (UB) modelSame principle as Top-of-the-Barrier (ToB), but with
Complex Bandstructure instead of Real Bandstructure
Transmission through potential barrier: T(E)=exp(-2*Κ(E)*L)
ToB
UB
Eg=1.408eVEg=1.404eVEg=1.378eVEg=0.817eV
Ohmic vs Schottky Contacts
Ohmic
Schottky
Id-Vgs transfer characteristics for Si NW and CNT FETs with
Ohmic and Schottky Contacts
Id-Vgs at Vds=0.5 V in CNT, NW, and UTB
VDD=0.5 V
Features:
•CNT with d=0.6nm and Si/InGaAs NW with d=3nm have same band gap: Eg=1.4eV
•CNT with d=1nm has band gap: Eg=0.82eV
•EOT=0.64nm made of 3.3nm HfO2
•No AGNR since worse than CNT
•Intrinsic characteristics
• d=1nm GAA-CNT (high IBT) and DG-UTB (bad electrostatics) scale poorly• 3-D devices with same “large” band gap (Eg=1.4 eV) scale better (low IBT)• if CNT with d<1 nm and Eg>1 eV possible, then at least as good as NW • CHALLENGE: trade-off between high injection velocity (low m*) and low
SS (high m*) needed, new constraint at short gate lengths
Conclusion and Outlook
• Simulation Platform for Lg=5nm Ultra-scaled Devices
Full-band and atomistic
Same approximations for All
• Understand Limiting Factors Electrostatics and IBT
Trade-off between vinj and SS
• Outlook Include non-ideal effects
Try other crystal orientations
Investigate nano-contact physics