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Nanoscale III-V CMOS
J. A. del Alamo
Microsystems Technology Laboratories
Massachusetts Institute of Technology
IEEE Electron Devices Society Webinar
July 13, 2016
Acknowledgements:
• Students and collaborators: D. Antoniadis, J. Lin, W. Lu, A. Vardi, X. Zhao
• Sponsors: Applied Materials, DTRA, KIST, Lam Research, Northrop Grumman,
NSF, Samsung
• Labs at MIT: MTL, EBL
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Moore’s Law at 50: the end in sight?
2
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Moore’s Law
Moore’s Law = exponential increase in transistor density
3
Intel microprocessors
2016:
Intel 22-core Xeon
Broadwell-E5
7.2B transistors
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Moore’s Law
4
?
How far can Si support Moore’s Law?
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Transistor scaling Voltage scaling Performance suffers
5
Transistor current density:
Goals:
• Reduced footprint with moderate short-channel effects
• High performance at low voltage
Intel microprocessors Intel microprocessors
Supply voltage:
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Moore’s Law: it’s all about MOSFET scaling
1. New device structures with improved scalability:
2. New materials with improved transport characteristics:
n-channel: Si Strained Si SiGe InGaAs
p-channel: Si Strained Si SiGe Ge InGaSb
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7
III-V electronics in your pocket!
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1. Self-aligned Planar InGaAs MOSFETs
9
Lin, IEDM 2012, 2013, 2014
W
Mo
Lee, EDL 2014; Huang, IEDM 2014
selective MOCVD
Sun, IEDM 2013, 2014 Chang, IEDM 2013
reacted NiInAs
dry-etched recess
implanted Si + selective epi
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Self-aligned Planar InGaAs MOSFETs @ MIT
10
Lin, IEDM 2012, 2013, 2014
Recess-gate process:
• CMOS-compatible
• Refractory ohmic contacts
• Extensive use of RIE
W
Mo
0.0 0.1 0.2 0.3 0.4 0.50.0
0.2
0.4
0.6
0.8
1.0 Lg=20 nm
Ron
=224 m0.4 V
I d (
mA
/m
)
Vds
(V)
Vgs
-Vt= 0.5 V
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• Ohmic contact first, gate last
• Precise control of vertical (~1 nm), lateral (~5 nm) dimensions
• MOS interface exposed late in process
Fabrication process
11
W/Mo n+ InGaAs/InP
InGaAs/InAs
InAlAs
SiO2
InP
d-Si
Resist
Mo
Pad
HfO2
Mo/W ohmic contact
+ SiO2 hardmask SF6, CF4 anisotropic RIE CF4:O2 isotropic RIE
Cl2:N2 anisotropic RIE Digital etch
Waldron, IEDM 2007
Finished device
Lin, EDL 2014
O2 plasma H2SO4
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• Channel: In0.7Ga0.3As/InAs/In0.7Ga0.3As
• Gate oxide: HfO2 (2.5 nm, EOT~ 0.5 nm)
Highest performance InGaAs MOSFET
12
Lg=70 nm:
• Record gm,max = 3.45 mS/mm at Vds= 0.5 V
• Ron = 190 Ω.mm Lin, EDL 2016
3.45 mS/m
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Excess OFF-state current
13
OFF-state current enhanced with Vds
Band-to-Band Tunneling (BTBT) or Gate-Induced Drain
Leakage (GIDL) Lin, IEDM 2013
-0.6 -0.4 -0.2 0.010
-11
10-9
10-7
10-5
Lg=500 nm
Vds
=0.3~0.7 V
step=50 mV
I d(A
/
m)
Vgs
(V)
Transistor fails to turn off:
Vds ↑
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-0.4 -0.2 0.0 0.210
-11
10-9
10-7
10-5
W/ BTBT+BJT
W/O BTBT
Vds
=0.3~0.7 V
step=50 mV
I d (A
/
m)
Vgs
(V)
Excess OFF-state current
14
Lg↓ OFF-state current ↑
bipolar gain effect due to floating body
Lin, EDL 2014
-0.6 -0.4 -0.2 0.010
-11
10-9
10-7
10-5
Lg=500 nm
Vds
=0.3~0.7 V
step=50 mV
I d(A
/
m)
Vgs
(V)-0.6 -0.4 -0.2 0.0
10-8
10-7
10-6
10-5
10-4
500 nm
280 nm
120 nm
T=200 K
Vds
=0.7 V
I d (A
/
m)
Vgs
-Vt (V)
Lg=80 nm
Vds ↑
Simulations w/ BTBT+BJT
w/o BTBT+BJT
Lg=500 nm
Lin, TED 2015
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2. InGaAs FinFETs
15
Intel Si Trigate MOSFETs
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Bottom-up InGaAs FinFETs
16
Si
Waldron, VLSI Tech 2014
Aspect-Ratio Trapping
Fiorenza, ECST 2010
Epi-grown
fin inside
trench
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Top-down InGaAs FinFETs
17 Kim, IEDM 2013
60 nm
dry-etched fins
Radosavljevic, IEDM 2010
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0 20 40 600.0
0.5
1.0
1.5
2.0
1.8
1
0.8
0.57
InGaAs FinFETs
5.3
4.3
Si FinFETs
gm[m
S/
m]
Wf [nm]
0.630.6
0.23
0.66 1
0.18
InGaAs FinFETs: gm
18
Thathachary,
VLSI 2015
gm normalized by width of
gate periphery
• Narrowest InGaAs FinFET fin: Wf=15 nm
• Best channel aspect ratio of InGaAs FinFET: 1.8
• gm much lower than planar InGaAs MOSFETs
Oxland, EDL 2016
Radosavljevic,
IEDM 2011
Kim, IEDM 2013
Natarajan,
IEDM 2014
channel
aspect
ratio
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InGaAs FinFETs @ MIT
19
Vardi,
DRC 2014,
EDL 2015,
IEDM 2015
Key enabling technologies: BCl3/SiCl4/Ar RIE + digital etch
• Sub-10 nm fin width
• Aspect ratio > 20
• Vertical sidewalls
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InGaAs FinFETs @ MIT
20
Vardi, VLSI Tech 2016 • CMOS compatible process
• Mo contact-first process
• Fin etch mask left in place double-gate MOSFET
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At VDS=0.5 V:
• gm=1.4 mS/µm
• Ron=170 Ω.µm
• Ssat=170 mV/dec
InGaAs FinFETs @ MIT
21 Vardi, VLSI Tech 2016
Lg=30 nm, Wf=22 nm, Hc=40 nm
(AR=1.8):
0.0 0.2 0.4 0.6 0.8 1.00
200
400
600
800
1000
1200 VGS
= 0.75V
0.5
0.25
0
-0.25
I d [
A
m]
VDS
[V]
-0.5
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.80
200
400
600
800
1000
Wf=22 nm
Lg=30 nm
VDS
=500mV
VGS
[V]
I d [
A
m]
0
400
800
1200
1600
gm [
S
m]
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.61E-8
1E-7
1E-6
1E-5
1E-4
1E-3
DIBL=220 mV/V
VGS
[V]
I d [A
m]
Wf=22 nm
Lg=30 nm
VDS
=500 mV
50 mV
S=140 mV/dec
170
Hc
Current normalized by 2xHc
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22
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.61E-10
1E-9
1E-8
1E-7
1E-6
1E-5W
f=7 nm
Lg=20 nm
VDS
=500 mV
VGS
[V]I d
[A
m]
50 mVS=120 mV/dec
DIBL~150
0.0 0.2 0.4 0.6 0.8 1.00
10
20
30
40 VGS
= 0.75 V
0.5
0.25
0-0.25
I d [
A
m]
VDS
[V]
Most aggressively scaled FinFET
Lg=20 nm, Wf=7 nm, Hc=40 nm (AR=5.7):
Vardi, VLSI Tech 2016
At VDS=0.5 V:
• gm=170 µS/µm
• Ron=4 kΩ.µm
• Ssat=130 mV/dec
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InGaAs FinFETs: gm benchmarking
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gm normalized by width of gate periphery:
• First InGaAs FinFETs with Wf<10 nm
• Severe gm degradation for thin Wf sidewall roughness?
Hc
Wf
Vardi, VLSI Tech 2016
Hc
Double gate Trigate
0 20 40 600.0
0.5
1.0
1.5
2.0
1.8
1
0.8
0.57
5.7
3.3
2.3
1.8
InGaAs FinFETs
5.3
4.3
Si FinFETs
gm[m
S/
m]
Wf [nm]
0.630.6
0.23
0.66 1
0.18
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Latest results
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Record results for InGaAs FinFETs with Wf < 25 nm
• Scaled gate oxide: HfO2 with EOT=0.6 nm
• Attention to line-edge roughness
0 20 40 600.0
0.5
1.0
1.5
2.0
1.8
1
0.8
0.57
5.7
3.3
2.3
1.8
InGaAs FinFETs
5.3
4.3
Si FinFETs
gm[m
S/
m]
Wf [nm]
0.630.6
0.23
0.66 1
0.18Latest!
Vardi, submitted 2016
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InGaAs FinFETs: gm benchmarking
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gm normalized by fin width (FOM for density):
• Doubled gm/Wf over earlier InGaAs FinFETs
• Still far below Si FinFETs poor sidewall charge control
Vardi, submitted 2016
Hc
Wf Wf
Hc
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Impact of fin width on VT
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• Strong VT sensitivity for Wf < 10 nm; much worse than Si
• Due to quantum effects
InGaAs doped-channel FinFETs: 50 nm thick, ND~1018 cm-3
Vardi, IEDM 2015
T=90K
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3. Nanowire InGaAs MOSFETs
27
Waldron, EDL 2014
Tomioka, Nature 2012 Persson, EDL 2012
• Nanowire MOSFET: ultimate scalable transistor
• Vertical NW: uncouples footprint scaling from Lg and Lc scaling
Tanaka, APEX 2010
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InGaAs Vertical Nanowires on Si by direct growth
28 Björk, JCG 2012
Selective-Area Epitaxy
Au seed
Vapor-Solid-Liquid
(VLS) Technique
InAs NWs on Si by SAE
Riel, MRS Bull 2014
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InGaAs VNW MOSFETs by top-down approach @ MIT
• Sub-20 nm NW diameter
• Aspect ratio > 10
• Smooth sidewalls
Zhao, EDL 2014
Key enabling technologies:
• RIE = BCl3/SiCl4/Ar chemistry
• Digital Etch (DE) =
O2 plasma oxidation
H2SO4 oxide removal
15 nm
240 nm
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Process flow Tomioka, Nature 2012 Persson, DRC 2012 Zhao, IEDM 2013
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-0.4 -0.2 0.0 0.2 0.4
0
100
200
300
400
500
600
700
Vgs(V)
Vds=0.5 V
gm
,pk(
S/
m)
NW-MOSFET I-V characteristics: D=40 nm
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Single nanowire MOSFET:
• Lch= 80 nm
• 3 nm Al2O3 (EOT = 1.5 nm)
• gm,pk=620 μS/μm @ VDS=0.5 V
• Ssat=110 mV/dec @ VDS=0.5 V
• Approaches best bottom-up devices
[Berg, IEDM 2015]
0.0 0.1 0.2 0.3 0.4 0.50
50
100
150
200
250
300
350Bottom electrode as the source (BES)
Vgs=-0.2 V to 0.7 V in 0.1 V step
Vds (V)
I d (A
/m
)
Zhao, 2016
(submitted)
-0.4 -0.2 0.0 0.2 0.4
10-9
10-8
10-7
10-6
10-5
10-4
Vds=0.5 V
Vgs(V)
I d (
A/
m) Vds=0.05 V
S=98 mV/dec, Vds
=0.05 V
S=110 mV/dec, Vds
=0.5 V
DIBL = 177 mV/V
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Self-aligned Bottom-up InAs NW-MOSFETs
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VNW MOSFET array:
• VLS growth
• D=28 nm
• Lch= 190 nm
• gm,pk=850 μS/μm @ VDS=0.5 V
• Ssat=154 mV/dec @ VDS=0.5 V
Berg, IEDM 2015
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4. InGaSb p–type MOSFETs
33
Nainani, IEDM 2010
Planar InGaSb MOSFET demonstrations:
Takei, Nano Lett. 2012
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InGaSb p–type FinFETs @ MIT
34 Lu, IEDM 2015
Key enabling technology:
• BCl3/N2 RIE
• [digital etch under development]
15 nm fins, AR>13
20 nm fins, 20 nm spacing
• Smallest Wf = 15 nm
• Aspect ratio >10
• Fin angle > 85° • Dense fin patterns
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Si-compatible contacts to p+-InAs
35
Lu, IEDM 2015
Ni/Ti/Pt/Al on p+-InAs (circular TLMs):
Record ρc: 3.5x10-8 Ω.cm2 at 400oC
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InGaSb p-type FinFETs
36 Lu, IEDM 2015
• Fin etch mask left in place double-gate MOSFET
• Channel: 10 nm In0.27Ga0.73Sb (compressively strained)
• Gate oxide: 4 nm Al2O3 (EOT=1.8 nm)
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InGaSb FinFET I-V characteristics
37
• Lg = 100 nm, Wf = 30 nm (AR=0.33)
• Normalized by conducting gate periphery
Lu, IEDM 2015
0.01 0.1 1 10 10010
100
Yuan, 2013 [7]
Nainani, 2010 [8]
Chu, 2014 [11]
Xu, 2011 [12]
Nagaiah, 2011 [13]In
0.36Ga
0.64Sb
GaSb
gm (
S/
m)
Lg (m)
This work
(FinFET)
In0.27
Ga0.73
Sb
GaSb In0.35
Ga0.65
Sb
In0.2
Ga0.8
SbPlanar MOSFETs
• First InGaSb FinFET
• Peak gm approaches best InGaSb planar MOSFETs
• Poor turn off
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5. Co-integration of SiGe p-MOSFETs and InGaAs MOSFETs on SOI
38
InGaAs
n-MOSFET
Czornomaz, VLSI Tech 2016
SiGe
p-MOSFET
6T-SRAM
SiGe InGaAs
Si
SiO2
Confined Epitaxial Lateral Overgrowth
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Conclusions
1. Great recent progress on planar, fin and nanowire
InGaAs MOSFETs
2. Device performance still lacking for multigate designs
3. P-type InGaSb MOSFETs in their infancy
4. Many, MANY issues to work out:
sub-10 nm fin/nanowire fabrication, self-aligned contacts, device
asymmetry, introduction of mechanical stress, VT control, sidewall
roughness, device variability, BTBT and parasitic HBT gain, trapping, self-
heating, reliability, NW survivability, co-integration on n- and p-channel
devices on Si, …
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A lot of work ahead but… exciting future for III-V electronics