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HORIZON 2020 EUROPEAN UNION FUNDING FOR RESEARCH & INNOVATION
Jin-Woo Han and Meyya MeyyappanNASA Ames Research CenterMoffett Field, Californa, USA
Nanotechnology in Nanoelectronics Development
Table of Contents
• History of Electronics Building Block
• Transition from Vacuum to Solid-State Era
• Nanoscale Vacuum Channel Transistor
• Device Characteristics
• Summary
6/30/2015 3
Electronic Revolution from Transistors
6/30/2015 4
Evolution of Electronics
Abacus
Mechanical Switch
Vacuum Tube
TransistorIntegrated
Circuit
Roman Analog
(1500)
Pascal calculator
(1670)
Babbage engine
(1830)
Vacuum Triode (1906) Junction
Transistor (1948)
Pentium (1995)
Eniac (1946)
17,000 TubesTradic (1954)
800 TransistorsIBM (1983)
6/30/2015 5
Vacuum Tube
Late 19th Century
- Expensive
- Bulky
- Fragile
- Energy hungry
Relay 1st Transistor 1st IC
1947 (William
Shockely)
- Ge material
- Instable
1849
- Babbage Engine
- 8000relays/5tons
- Short lifetime
1959 (Robert
Noyce)
- Si material
- SiO2 dielectric
- Al gate
Now
- Si substrate
- SiO2 dielectric
- Poly-Si gate
Gate
S D
Nano-Electro-Mechanical
Switch
For low-standby power (~2007)
By MEMS technology
For high mobility channel (~2004)
By ALD technology
For low gate delay
By MG technology
(~1990’)?
Back to the Past for Better Future
6/30/2015 6
Operation Mechanism of Triode Devices
Cathode Anode
Grid
Vacuum
Source Drain
Gate
Silicon
Vacuum Tube
Transistor
Gate/Grid Voltage
Dra
in/A
no
de C
urr
en
t
ON
OFF
• Switch
• Amplifier
6/30/2015 7
Benefit of Vacuum Channel – Speed
Silicon crystal lattice
Lattice Scattering
Velocity Saturation
= 5 X 107cm/s
Ballistic Transport
c = 3 X 1010cm/s
Vacuum
6/30/2015 8
Benefit of Vacuum – Temperature Immunity
Crystal lattice scattering in semiconductor
Vacuum Channel is immune to high temperature.
Military applications
6/30/2015 9
Benefit of Vacuum – Radiation Immunity
Radiation ionization in semiconductor
Vacuum Channel is immune to radiation.
Nuclear & space applications
Weakness of Vacuum Device - Bulky
Replacing a bad tubes ENIAC, Integration?
Bulky Tube
Broken Tube
Weakness of Vacuum Device – Energy
Hot cathode
Energy
Quantum
Well
Electron
Workfunction
Evolution Scenario of Triode Devices
+ High gain
+ High performance
+ Premier audio
- Bulky, Fragile
- Expensive
- Short Lifetime
- Power consumption
Vacuum Tube
+ Cheap
+ Integrated Circuit
+ Reliable
+ Low energy
+ Long lifetime
+ Variety applications
- Low performance
- Low breakdown
MOSFET
+ CMOS process
+ Cheap !!+ Long lifetime
+ High power
+ High performance
+ Variety applications
+ Premier audio
Nano Vacuum Tube
Cathode Anode
Back gate
Vacuum ambient
<5nm
<50nm
What If Nanoscale Vacuum Device ?
Machining (millimeter scale)
Discrete component
Operation voltage > 100V
Thermionic emission (heater)
Short lifetime
Glass package (fragile)
High vacuum requirement
Conventional vacuum tube
Wafer process (nanometer scale)
Integrated vacuum circuit
Operation voltage <10V
Field emission (cold cathode)
Long lifetime due to heating free
Semiconductor package
Relaxed vacuum requirement
Nanoscale vacuum tube
Fowler-Nordheim Tunneling
E
C
E
C
Tunnelingdistance
VG < Vturn-on VG > Vturn-on
Vacuum Vacuum
Off-state On-state
Electron tunneling through a potential barrier, rather than escaping over it
Thermal excitation Photo excitation Tunneling
Surface barrier Surface barrier bending
due to applied field
Fowler-Nordheim Equation
m mass of electron
work function of the cathode
y function of F and
t(y), v(y) approximated as constants
J emission current density
e electron charge
h Planck’s constant
F electric field at cathode
)(
3
)2(8exp
)(8
2/32/1
2
23
yvheF
m
yth
FeJ
Field Emission Current Density
dssFDsTNeJ ),,(),(
N(T,S): electron density
D(F,s,): tunneling probability
s: kinetic energy
T: temperature
F: applied field
: work function
F-N Tunneling Equation
6/30/2015 16
Simplified F-N Tunneling Equation
Where:
V
baVI exp
2
a emitting area
emitter work function
field enhancement factor
Vba
V
I 1)ln(ln
2or
2/1
264.10
exp1.1
1056.1
aa
/1044.62/37b
Field Enhancement Factor
Anode
Cathode
= F / V
d
r
hr
h1
24ln
2
h
dr
F: electric field at emitter tip
V: voltage between anode and cathode rSpacer
6/30/2015 17
Target SpecificationsTarget dimension < 50 nm
Vacuum range Pressure (mbar) Mean free path
Ambient pressure 1013 68nm
Low vacuum 300-1 0.1-100um
Medium vacuum 1-10-3 0.1-100mm
High vacuum 10-3-10-7 10cm-1km
Ultra high vacuum 10-7-10-12 1km-105km
Extremely high vacuum <10-12 >105km
Target operation voltage < 5V
6/30/2015 18
Summary
• Lesson learned from solid-state device history
• Pivot of historical change in device technology
• Nanoscale vacuum less than mean-free-path air
• Operation voltage less than ionization potential
• Gate-all-around structure
• Vacuum electronics may be back to the future