Nanoscale Science and EngineeringNSF, Arlington, VA
Dec. 6, 2010Eli Yablonovitch, Berkeley EECS Dept.
Electronics / network electricity use
Buildings Electricity: ~2,700 TWh
CommercialResidential
Electronics
Networked~150 TWh ?
Net. Eqt.~ 20 TWh
• U.S. only• Annual figurescirca 2006
• All approximate
One central baseload power plant (about 7 TWh/year)
~290 TWh
Bruce Nordman, LBL
Tel.
• Because power consumption Vdd2
and Vdd (operation voltage) scaling has slowed after 0.13μm node.
High Performance ITRS Roadmap
0.7 V0.8 V0.9 V1.0 V1.1 V1.2 V1.3 V1.8 V2.5 VVdd
16 nm
22 nm
32 nm
45 nm
65 nm
90 nm
0.13 µm
0.18 µm
0.25 µm
Technology Node
Power Usage Rising Faster Than Past Trend
∝
Units:
~40kT/bit of information
0.16 atto-Joules/bit of information
0.16 nano-Watts/Gbit/second
This is about 106 times less energy than we are using today!
What will be the energy cost, per bit processed?
1. Logic energy cost ~40kT per bit processed
2. Storage energy cost ~40kT per bit processed
3. Communications currently >100,000kT per bit processed
.
There are many type of memory possible:1. Flash2. SRAM3. Dram4. Magnetic Spin5. Nano-Electro-Chemical Cells6. Nano-Electro-Mechanical NEMS7. Memristor8. Chalcogenide glass (phase change)9. Carbon Nanotubes
••
Similarly there are many ways to do logic.
But there are not many ways to communicate:
1. Microwaves (electrical)2. Optical
Moore
You?
!
Transistor
fkTR
V
fRkTV
noise
noise
∆=
∆=
4
42
2
What is the energy cost for electrical communication?
Signal Noise PowerEnergy per bit≥ = 4kT per bit
All information processing costs ~ 40kT per bit. (for good Signal-to-Noise Ratio)
Great!
So what’s the problem?
{
mVolt1V
CqqkT4VCq
qkT4V
C1kT4V
RC1RkT4V
fRkT4V
Volts10mVolts100noise
2noise
2noise
2noise
2noise
≈
×=
×=
×=
=
∆=
µ
//321
The natural voltage range for wired communication is rather low:
The thermally activated device wants at least one electron at ~1Volt.
The wire wants1000 electrons at 1mVolt each.
(to fulfill the signal-to-noise requirement >1eV of energy)
Voltage Matching Crisis at the nano-scale!
If you ignore it the penalty will be (1Volt/1mVolt)2 = 106
The natural voltage range for a thermally activated switch like transistors is >>kT/q, eg. ~ 40kT/q
or about ~1Volt
"In addition, power is needed primarily todrive the various lines and capacitances associated with thesystem. As long as a function is confined to a small area ona wafer, the amount of capacitance which must be driven isdistinctly limited. In fact, shrinking dimensions on an integratedstructure makes it possible to operate the structure athigher speed for the same power per unit area."
p. 114
10µm
1µm
100nm
10nm
Moore's Law
1960 1980 2000
Crit
ical
D
imen
sion
2020 2040 2060Year
Tech
nolo
gy G
ap
Gates only
Gates including wires
107
105
102
1
0.1
104
106
10
108
103
Ene
rgy
per B
it fu
nctio
n (k
T)
The other , for energy per bit function
Shoorideh and Yablonovitch, UCLA 2006
Transistor Measurements by Robert Chau, Intel
nano-transformerνh
~1eV
A low-voltage technology, or an impedance matching device,needs to be invented/discovered at the Nano-scale:
transistor amplifier with steeper sub-threshold slope
photo-diode
+ ++
-
+VG
MEM's switch
Cryo-ElectronicskT/q~q/C
Cu
Cu
solid electrolyte
Electro-Chemical Switch
giant magneto-resistancespintronics
+
•TFET's•Negative Capacitance Gates
--V2O5 metal-insulator transition
Theme 1 ‐ Nanoelectronics: Solid‐State Milli‐Volt Switching
An amplifying transistor as a voltage matching device:Small voltage inLarge voltage out
in
outAmplification of weak signals has an energy cost!Amplification of weak signals has a speed penalty!
Gate Voltage
Cur
rent
Vg
ln{I}
steeper sub-threshold
slope
The Zener Diode:
EFc
EFv
band
to b
and
tunn
elin
g
Bias Voltage
Diff
usio
n cu
rren
t
Cur
rent
EF
band
to b
and
tunn
elin
g
Bias Voltage
Diff
usio
n cu
rren
t
Sharp Step
Cur
rent
The Esaki Diode:
The Backward Diode as a Switch:
EFc
EFv
band
to b
and
tunn
elin
g
Bias Voltage
Diff
usio
n cu
rren
t
Cur
rent
Sharp Step
The Backward Diode:These have been routinely made in Ge homo-junctions,since the 1960's.
• Modulate the Tunneling Barrier
• Density of States Switch
2 Ways to Obtain Steepness
The sub‐threshold slope for tunneling dependson the steepness of
the band‐edges:
All The CasesN
IP
Z
I
ZP
N
YI P
N
Z
NI
P
Z
IP
N
ZLZ,i
ZIP
X
N
NP
Z
IP
N
Z
N
IP
Z
X
24
I
ZP
N
IP
N
ZLZ,i
IP
N
Z
)(***2 32
*232 ETEVmeJ ZiOLDD
r
hπ=−
)(** ,,32,22 ETEEemJ fZiZAreaDDr
hπ=−
)(*42
2
32
*333 Ε=−
r
hT
VmeJ OLDD
π
I
VG
2OLVI ∝
I
VG
ConstantI ∝
I
VG
NI
P
Z
NI
P
Z
NP
Z
)(**2*210 ETE
heI ZiDD
r=−
)(*)(***4*2,,00 fifZiZDD EEETEE
heI −=− δ
r
)(**2 2Point,11 Ε=−
rTV
heJ OLDD
I
VG
ConstantI ∝
I
VG
I
VG
YI P
N
Z
ZIP
X
N
N
IP
Z
X
)(***222
2/321 ETVEmeJ OLZiDD
r
hπ=−
)(1**2,,22
2/1,11 ET
VEEmeJ
OLfZiZEdgeDD
r
hπ=−
)(*3
2 2/322
2/5Edge,22 ETVmeJ OLDD
r
hπ=−
I
VG
2/3OLVI ∝
I
VG
OLVI ∝
VG
OLVI 1∝
EC
OFF
material 2(AlGaSb)
oxide
gate metal
quantum well 1 (I
nAs)
EF
EV
EF
EC
ON
EF
EF
EV
oxide
gate metal
quantum well 1 (I
nAs)
material 2(AlGaSb)
EC
SHARPLYOFF
material 2(AlGaSb)
oxide
gate metal
quantum well 1 (InA
s)
EF
EV
EF
CDEP
CQW
COX
z
Theme 1:Key Scientific Questions (Kickoff Meeting 2010)
• New examples of Type III Energy band offsets need to be discovered.
• Fundamental band edge abruptness is very poorly understood.
• We need to concentrate on 2d/2d pn junctions
• Do we want to go all the way to monolayer/monolayer pn junctions?
• Will that guarantee reproducible thresholds?
nano-transformerνh
~1eV
A low-voltage technology, or an impedance matching device,needs to be invented/discovered at the Nano-scale:
transistor amplifier with steeper sub-threshold slope
photo-diode
+ ++
-
+VG
MEM's switch
Cryo-ElectronicskT/q~q/C
Cu
Cu
solid electrolyte
Electro-Chemical Switch
giant magneto-resistancespintronics
+
•TFET's•Negative Capacitance Gates
--V2O5 metal-insulator transition
Theme 2 ‐ NanoMechanics: Solid‐State Milli‐Volt Switching
Why Mechanical Switches?
• Relays have zero off‐state leakage zero static energy
Source
DrainGate
Air gap
tgap tdimple
32
3-Terminal Relay
• Relays switch on/off abruptly allows for aggressive VDD scaling (ultra‐low dynamic energy)
Measured I-V
Gate Voltage
Dra
in C
urre
nt
S≈0.1mV/dec
VPIVPO
Relay On‐State Resistance
• ~1K Ohm resistance is acceptable for performance.Formation of metal‐metal bonds in the on state is not necessary!
• Physical contact can be avoided altogether, to eliminate surface adhesion, with a deformable dielectric:
33
tunneling current
• Electrodes can be coated to improve reliability:
dielectric
Tunneling Nanoswitch
Advantages:• ease of fabrication and packaging
• better device reliability
Device Operating Principle:• Electrostatic actuation of electrode • Conduction via tunneling
• nanoconductors embedded in a deformable matrix
7.7
mV
/ D
ecad
e
Pull-In/Pull-Out
Bulovic / Lang (MIT)
Tunneling Micro-Electro-Mechanical Systems:
Double Win:
1. By never making direct contact, we don't pay the energy price of theinterfacial energy.
2. By never making direct contact, the reliability issues are greatly eased.
This comes at the price of higher resistance, but we know the wires in chips have a
characteristic impedance ~1000 Ohms.
This is achievable by tunneling without direct contact!
nano-transformerνh
~1eV
A low-voltage technology, or an impedance matching device,needs to be invented/discovered at the Nano-scale:
transistor amplifier with steeper sub-threshold slope
photo-diode
+ ++
-
+VG
MEM's switch
Cryo-ElectronicskT/q~q/C
Cu
Cu
solid electrolyte
Electro-Chemical Switch
giant magneto-resistancespintronics
+
•TFET's•Negative Capacitance Gates
--V2O5 metal-insulator transition
Theme 4 – NanoPhotonics for Ultra‐Low Energy Communication
Ultra-sensitive Floating Gate photodetector:
Eliminate wire capacitance between photodetector and amplifierTransistor with a floating Ge-islandPhotonic crystal cavity with 1000×efficiency improvement.
SiO2
Silicon
Drain
Source
n-Si n-Si
Ge islandn-Si channel
Reflectors integrated with SOI waveguides to create a transverse cavity
incident light
Source Drain
SiO2
Silicon
n-Sih+h+
e- e-
Photons modulate depletion widthGe
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
Volta
ge (µ
V)
0 100 200 300 400 500
Time (ps)
40psec
39
nano-transformerνh
~1eV
A low-voltage technology, or an impedance matching device,needs to be invented/discovered at the Nano-scale:
transistor amplifier with steeper sub-threshold slope
photo-diode
+ ++
-
+VG
MEM's switch
Cryo-ElectronicskT/q~q/C
Cu
Cu
solid electrolyte
Electro-Chemical Switch
giant magneto-resistancespintronics
+
•TFET's•Negative Capacitance Gates
--V2O5 metal-insulator transition
Theme 3 – NanoMagnetics: Surmounting the Landauer Limit
41
Fundamental Limits of Computing
Charles BennettRolf Landauer
Von Neumann-Landauer limit (1961):Energy lost in a logic operation in which 1 bit is lost is E ≥ kT ln 2
John von Neumann
Bennett (1973):Logical Reversibility of Computation