MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Quantum Effects Lead to Phenomena such as:
Ultra Thin Oxides – Observe:
High Leakage Currents Through the Oxide - Tunneling
Depletion in Poly-Si metal gate – capacitance effect
Thickness of Inversion Layer – alters tox
GIDL (Gate-Induced Drain Leakage) – High Doping - Leads to
tunneling
DIBL (Drain-Induced Barrier Lowering) – Short Channel - Leads to
tunneling
Take advantage of Quantum Effects
Decrease effective mass
Change E -vs- k energy band diagram by…
Induce strain using lattice mismatch between S/Cs
Quantum Confinement – Gain in Device Efficiency
Band gap engineering – Use other S/Cs to decrease Eg
Knowlton
1
MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Ultrathin SiO2 – begin to observe quantum effects
+V
gate
VSource
M
VDrain
W
+
poly-crystalline
Si
O
Source Contact
Insulator
S
n++ Poly Si
Gate Contact
or Electrode
Drain Contact
Insulator
SiO2 - Gate oxide
n+source - - - - - - - - - - - - - - n+drain
channel
p-Si Wafer
Crystalline Si
L
Cox 
Knowlton
 o r A
tox

tox
 o kox A
tox
2
1
MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Ee-
Ef
n++-Si
p- Si
p- Si
n++-Si
p- Si
n++-Si
SiO2
SiO2
Flat band
Knowlton
MSE 310/ECE 340
Electrical Properties
of Materials
SiO2
What condition
is this?
3
Part 5: Quantum Effects in MOS Devices
EeTreat as
IF a p-n
junction
p- Si
n++-Si
n++-Si
p- Si
p- Si
n++-Si
e- flow
only one
way
SiO2
Flat band
Knowlton
SiO2
What condition
is this?
4
2
MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Poly-depletion
eVRev
p- Si
n++-Si
Knowlton
MSE 310/ECE 340
Electrical Properties
of Materials
Poly
depletion
Biased into Strong Inversion
5
Part 5: Quantum Effects in MOS Devices
Depeletion in poly-Si
C  Cox


x
1
C 
 D , poly 
C
 Si 
 ox , physical
1
Colinge & Colinge, S/C Devices
Other:
Relativistic Carriers (hot emissionoxide damage)
Knowlton
6
3
MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Quantization: (cont.)
2D gas in channel
Inversion layer thickness is similar
to the gate oxide thickness
tox ,eff  tox , physical 
Changes oxide thickness
 ox
x
 Si
Davies, The Physics of Low Dimensional
Semiconductors, (Cambridge, 1998) p. 343
See also:
KnowltonHareland, IEEE Transactions on Electron Devices, 1996
Anderson & Anderson. Fundamentals of
Semiconductor Devices, (McGraw Hill, 2005) p.
504-506
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MSE 310/ECE 340
Part 5: Quantum Effects in MOS Devices
Quantization (Cont.) – Consider Quantization in MOS Channel
Electrical Properties
of Materials
EC,S-C
Ee-
Oxide
Semiconductor
Where are:
Ψ and lΨl2
located???
Knowlton
From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
8
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MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
8
Quantization: (cont.) - Recall “Particle in a Box” or “Infinite Potential Well” or “Quantum Well”?
Chapter 3 of Kasap
V=
8
V=
8
V(x)
Electron
V=0
Energy of electron
Ψ and lΨl2 is
always zero at
the boundary!
0
0
a
0
E4
n=4
E3
n=3
E2
n=2
E1
n=1
x
4
3
2
x=0
x=a
Energy levels in the well
1
0
x
(x)  sin(nx/a)
a0
a
Probability density  |(x)|2
Electron in a one-dimensional infinite PE well. The energy of the
electron is quantized. Possible wavefunctions and the probability
distributions for the electron are shown.
Knowlton
From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
MSE 310/ECE 340
Electrical Properties
of Materials
9
Part 5: Quantum Effects in MOS Devices
Quantization: (cont.)
2D gas in channel
Inversion layer thickness is similar
n ~1
to the gate oxide thickness
Changes oxide thickness
tox ,eff  tox , physical 
Knowlton
 ox
x
 Si
Energy States of e-:
Bound versus Unbound (continuum)
Davies, The Physics of Low Dimensional Semiconductors, (Cambridge, 1998) p. 343
10
5
MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Tunneling:
Drain Induced Barrier Lowering (DIBL)
Fowler-Nordheim (FN) [cold
emission – oxides]
Direct (oxides)
Band-to-Band
Barrier lowering
Vgate= 0n
Vg
Drain
Contact
Poly Si
Gate Contact
VD=VDD
Vd
Drain
Contact
SiO2 - Gate oxide
n+source
n+drain
channel
p-Si Wafer
This results because…
…this occurs.
Knowlton
Streetman & Banerjee , Solid State Electronic Circuits (Prentice Hall,2000)
MSE 310/ECE 340
Electrical Properties
of Materials
Muller & Kamins (Wiley-Interscience,2003) Fig. 9.17 p. 452
Part 5: Quantum Effects in MOS Devices
Gate Induced Drain Leakage (GIDL)
Tunneling:
Vgate=0
Vg
Poly Si
Gate Contact
Colinge & Colinge, S/C Devices
Fowler-Nordheim (FN) [cold
emission – oxides]
Direct (oxides)
Band-to-Band
Barrier lowering
Drain
Contact
11
VD=VDD
Vd
Drain
Contact
SiO2 - Gate oxide
n+source
n+drain
channel
P-Si Wafer
Knowlton
GIDL
Sze, Modern S/C Device Physics (Wiley-Interscience,1998)
Ch. 3 by SlJ. Hillenius
12
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MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Quantization: (cont.)
2D gas in channel
SOI Gate-all-around (GAA) MOSFET:
Knowlton
MSE 310/ECE 340
Electrical Properties
of Materials
Colinge & Colinge, S/C Devices
13
Part 5: Quantum Effects in MOS Devices
Bandgap Engineering of Channel
Consider: Bandgap, mobility, effective mass, lattice matching, quantum confinement of carriers
Lattice Constants:
aSi = 5.4309 Å
aGe = 5.6577 Å
Knowlton
Cullity, Elements of X-ray Diffraction, 2nd Ed (1978) Appendix 5
From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
14
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MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Bandgap Engineering of Channel
Consider: Bandgap, mobility, effective mass, lattice matching, quantum Lattice Constants:
confinement of carriers
aSi = 5.4309 Å
aGe = 5.6577 Å
Cullity, Elements of X-ray Diffraction, 2nd Ed (1978) Appendix 5
Knowlton
Science M. Ieong, B. Doris, J. Kedzierski, K. Rim, M. Yang, Silicon Device Scaling to Sub-10nm Regime (2004)
MSE 310/ECE 340
Electrical Properties
of Materials
15
Part 5: Quantum Effects in MOS Devices
Bandgap Engineering of Channel
Consider: Bandgap, mobility, effective mass, lattice matching, quantum
Lattice Constants:
confinement of carriers
aSi = 5.4309 Å
aGe = 5.6577 Å
Cullity, Elements of X-ray Diffraction, 2nd Ed (1978) Appendix 5
Knowlton IBM RJ Antoniadis et al., Continuous MOFET Performance Inc with Scaling - Strain & Channel Matl (2006)
16
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MSE 310/ECE 340
Bandgap Engineering for Light Emitting Devices
Electrical Properties
of Materials
Type 1
Type 2
Type 3
Herbert Kroemer, Nobel Lecture: Quasielectric fields and band offsets: teaching electrons new tricks*, REVIEWS OF MODERN PHYSICS, VOLUME 73,
JULY 2001, *The 2000 Nobel Prize in Physics was shared by Zhores I. Alferov, Jack S. Kilby, and Herbert Kroemer. This lecture is the text of Professor
Knowlton Kroemer’s address on the occasion of the award.
MSE 310/ECE 340
Electrical Properties
of Materials
Knowlton
Anderson & Anderson, Fundamentals of Semiconductor Devices, (McGraw Hill, 2005) Ch. 6.3 p. 317-331
Bandgap Engineering: Three types
Note that the band offsets are not the same!
17
Heterojunctions – Type 2 & 3
18
9
MSE 310/ECE 340
Electrical Properties
of Materials
Knowlton
MSE 310/ECE 340
Electrical Properties
of Materials
Knowlton
Tunnel FET (TFET)
IRPS Datta HTFET for Energy Efficient Computing 2013
19
Tunnel FET (TFET)
Mayberry-Intel Pushing Past Frontiers of Technology final [3 2013]
20
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MSE 310/ECE 340
Electrical Properties
of Materials
Part 5: Quantum Effects in MOS Devices
Quantization: (cont.)
2D gas in channel
SOI Gate-all-around (GAA) MOSFET:
Gate-All-Around (GAA) MOSFET is an SOI transistor in which the gate
oxide and the gate electrode are wrapped around the channel region.
Fabricated using an SOI CMOS process to which two process steps are
added
a photolithographic step
a wet etch step during which a cavity is formed under previously patterned
silicon islands.
The remarkable features of this MOSFET are that there are two channels
(at the top and the bottom of the silicon film,
The entire channel area is surrounded by good-quality gate oxide and the
gate electrode.
Knowlton
Colinge & Colinge, S/C Devices
21
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