COMON: SOI Multigate Devices Modeling - MOS-AK

52 Pages·2013·3.56 MB·German

by  Paul Böhm

COMON:
SOI Multigate Devices Modeling

Alexander Kloes, Michael Graef, Franziska Hain, Thomas Holtij, Mike Schwarz
Technische Hochschule Mittelhessen, Germany
NanoP - Competence Center Nanotechnology and Photonics
Research Group Nanoelectronics / Device Modeling
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 1
Outline
1. Introduction
1.1 Current Flow in MuG-FETs
1.2 Challenges to Compact Modeling
1.3 Conformal Mapping
2. Conventional MuG-FETs
2.1 Undoped / Doped Junction-based DG-FET
2.2 Junctionless DG-FET
2.3 Trigate-FET
3. Tunneling Devices
3.1 Schottky Barrier DG-FET
3.2 Tunnel FET
4. Conclusions
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 2
Outline
1. Introduction
1.1 Current Flow in MuG-FETs
1.2 Challenges to Compact Modeling
1.3 Conformal Mapping
2. Conventional MuG-FETs
2.1 Undoped / Doped Junction-based DG-FET
2.2 Junctionless DG-FET
2.3 Trigate-FET
3. Tunneling Devices
3.1 Schottky Barrier DG-FET
3.2 Tunnel FET
4. Conclusions
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 3
1.1 Current Flow in MuG-FETs
Current flow in Trigate FETs: in fact a 3D problem!
Most leaky path in lightly doped device:
 below VT: channel center (most DIBL)
 above VT: channel surface
 Device first switches on in corners (max. gate control)
Gate

n
ai Gate Gate
r
e D
t n n
a i i
a a
G
e Dr Dr
d
e xi e e
ec O d d
cr xi xi
urou O O
oS
S
SOI
below VT above VT
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 4
1.1 Current Flow in MuG-FETs
TCAD: Transfer Characteristics and Transconductance
Hch=50nm
Tch=20nm
 Below VT:
center current dominates
 Above VT:
surface current dominates

[1] A. Kloes, M. Weidemann, M. Schwarz: Analytical Current Equation for Short-Channel SOI Multigate FETs Including 3D
Effects, in Solid-State Electronics, Vol. 54, No. 11, 2010.
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 5
1.1 Current Flow in MuG-FETs
Lightly-doped short-channel Trigate FET
Position of most leaky path along channel (above VT)
Gate

n
ai
r
D
e
t
a
G
e
d
ce rce Oxi
ru
uo
oS
S
SOI
channel length
shortening
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 6
1.2 Challenges to Compact Modeling
Challenges to compact modeling:
 2D or 3D potential problem
 Compact models require analytical (closed form) solution
 Minimum fitting parameters for scalability and predictive ability
This work:
 DC modeling only
Simplifications:
 (Mostly) neglect quantum confinement (Tch > 10nm)
 No fringing fields in BOX
 Neglect back gate
 Drift-diffusion transport
But…
 Inherently include 2D/3D effects without the need of any fitting parameters!
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 7
1.3 Conformal Mapping
Approach to solve 2D potential problem:
Q + q
∆Φ(x, y) = − dep inv Poisson‘s equation
ε

Si
 Map area of interest in complex plane Z upon
simplified geometry in complex plane W
(Schwarz-Christoffel transformation)
 Solve potential problem in plane W
(e.g. by Poisson‘s integral)
 Re-map solution to plane Z
 Prefer 2D Laplacian instead of
Poisson equation
(to avoid mapping of space charge)

[2] Kloes, A., Kostka, A.: A new analytical method of solving 2D Poisson´s equation in MOS devices applied to threshold voltage
and subthreshold modeling, Solid-State Electron., Vol. 39, No. 12, pp. 1761–1775, 1996
[3] E. Weber, Electromagnetic fields, Vol. I., Mapping of fields. John Wiley, New York, 1950
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 8
Outline
1. Introduction
1.1 Current Flow in MuG-FETs
1.2 Challenges to Compact Modeling
1.3 Conformal Mapping
2. Conventional MuG-FETs
2.1 Undoped / Doped Junction-based DG-FET
2.2 Junctionless DG-FET
2.3 Trigate-FET
3. Tunneling Devices
3.1 Schottky Barrier DG-FET
3.2 Tunnel FET
4. Conclusions
12. April 2013 Spring MOS-AK/GSA Workshop 2013 - Alexander Kloes 9
2.1 Undoped / Doped Junction-based DG-FET
Double-Gate FET:

 Undoped / doped channel
 Analytical 2D potential solution for Poisson equation
 Neglect mobile charge (subthreshold)
 Closed form solution by conformal mapping technique
 Extend solution to strong inversion
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