2013-02-24
CMOS Compatible Nanoscale Vacuum Tube
02/19/2013
Jin-Woo
Jin
Woo Han, Ph. D
NASA Ames Research Center
Electronic Revolution from Transistors
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
1
2013-02-24
Evolution of Electronics
Vacuum Triode (1906) Junction
Transistor (1948)
Abacus
Pentium (1995)
Mechanical Switch
Vacuum Tube
Transistor
Integrated
Circuit
Pascal calculator
(1670)
Roman Analog
(1500)
Eniac (1946)
17,000 Tubes
Babbage engine
(1830)
Tradic (1954)
800 Transistors
IBM (1983)
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Vacuum Tube
Grid
Cathode
Anode
Vacuum
Transistor
Gate
Source
Drain
Silicon
Drain/Anode
e Current
Operation Mechanism of Triode Devices
ON
OFF
Gate/Grid Voltage
g
• Switch
• Amplifier
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
2
2013-02-24
Back to the Past for Better Future
For low-standby power (~2007)
By MEMS technology
For high mobility channel (~2004)
By ALD technology
Nano-Electro-Mechanical
Switch
?
For low gate delay
By MG technology
(~1990’)
Gate
S
Relay
1849
- Babbage Engine
- 8000relays/5tons
- Short lifetime
Vacuum Tube
19th
Late
Century
- Expensive
- Bulky
- Fragile
- Energy hungry
1st Transistor
1947 (William
Shockely)
- Ge material
- Instable
1st IC
D
Now
1959 (Robert
- Si substrate
Noyce)
- SiO2 dielectric
- Si material
- Poly-Si gate
- SiO2 dielectric
- Al gate
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Edison Effects (1883)
Hot filament
(Cathode)
Current
Thomas Edison (1847-1931)
Thermionic Emission
Æ Heat-induced flow of electron from a surface of metal to a vacuum
Metal Workfunction
Æ Minimum energy required for the electron overcomes the biding potential
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
3
2013-02-24
Vacuum Diode, Fleming Oscillation Valve
(1903)
John Ambrose Fleming (1849-1945)
Fleming Oscillation Valve
Æ First application of the Edison Effect used as a rectifier and detector
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Vacuum Triode, Audion (1906)
Grid
Cathode
Anode
Lee de Forest (1873-1961)
Vacuum Triode
Æ First device to provide power gain and radio transmitter.
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
4
2013-02-24
Transistor (1914)
John Bardeen, William Shockley, Walter Brattain
AT&T Bell Lab
Nobel Prize in 1956
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Integrated Circuit (1958)
J k Kilby
Jack
Kilb (1923-2005)
(1923 2005)
Texas Instrument
Nobel Prize in 2000
SF Bay Area Nanotechnology Council
February 19, 2013
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5
2013-02-24
Evolution Scenario of Triode Devices
Vacuum Tube
MOSFET
Nano Vacuum Tube
+ Cheap
+ High gain
+ High performance
+P
Premier
i audio
di
+ CMOS process
+ Integrated Circuit
+ Cheap !!
+ Reliable
+L
Long lifetime
lif ti
+ Low energy
- Bulky, Fragile
+ High power
+ Long lifetime
- Expensive
+ Variety applications
- Short Lifetime
- Power consumption
- Low performance
- Low breakdown
+ High performance
+ Variety applications
+ Premier audio
Vacuum ambient
<50nm
Cathode
<5nm
Anode
Back gate
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Benefit of Vacuum Channel – Speed
Vacuum
Ballistic Transport
c = 3 X 1010cm/s
Silicon crystal lattice
Lattice Scattering
Velocity Saturation
= 5 X 107cm/s
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
6
2013-02-24
Benefit of Vacuum – Temperature Immunity
Crystal lattice scattering in semiconductor
Vacuum Channel is immune to high temperature.
Æ Military applications
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Benefit of Vacuum – Radiation Immunity
R di ti
Radiation
iionization
i ti
iin semiconductor
i
d t
Vacuum Channel is immune to radiation.
Æ Nuclear & space applications
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
7
2013-02-24
Weakness of Vacuum Device - Bulky
Bulky Tube
Replacing a bad tubes ENIAC, Integration?
Broken Tube
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Weakness of Vacuum Device – Energy
Electron
Quantum
Well
Energy
Workfunction
Hot cathode
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
8
2013-02-24
What If Nanoscale Vacuum Device ?
Conventional vacuum tube
Nanoscale vacuum tube
Machining (mm scale)
Wafer process (nm scale)
Æ Discrete component
Æ Integrated vacuum circuit
Æ Operation voltage > 100V
Æ Operation voltage <10V
Æ Thermionic emission (heater)
Æ Field emission (cold cathode)
Æ Short lifetime
Æ Long lifetime due to heating free
Æ Glass package (fragile)
Æ Semiconductor package
Æ High vacuum requirement
Æ Relaxed vacuum requirement
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Fowler-Nordheim Tunneling
Surface barrier
Surface barrier bending
due to applied field
φ
Thermal excitation
Photo excitation
Tunneling
Electron tunneling through a potential barrier, rather than escaping over it
Off-state
E
Tunneling
distance
E
Vacuum
VG < Vturn-on
On-state
Vacuum
C
VG > Vturn-on
C
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
9
2013-02-24
F-N Tunneling Equation
Field Emission Current Density
J = e ∫−+∞∞ N (T , s ) D( F , s, φ )ds
N(T,S):
D(F,s,φ):
s:
electron density
tunneling probability
kinetic energy
T:
F:
φ:
temperature
applied field
work function
Fowler-Nordheim Equation
J=
J
e
h
F
⎡ 8π ( 2m )1 / 2φ 3 / 2
⎤
v ( y )⎥
exp ⎢ −
3heF
8πhφt ( y )
⎣
⎦
e 3F 2
2
emission current density
electron charge
Planck’s constant
electric field at cathode
m
φ
y
t(y), v(y)
mass of electron
work function of the cathode
function of F and φ
approximated as constants
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Simplified F-N Tunneling Equation
⎛ b⎞
I
1
I = aV 2 exp⎜ − ⎟ or ln⎛⎜ 2 ⎞⎟ = ln( a ) − b⎛⎜ ⎞⎟
⎝V ⎠
⎝V ⎠
⎝ V⎠
−6
2
⎛
⎞
Where: a = 1.56 × 10 αβ exp⎜ 10.4 ⎟
⎜ φ 1/ 2 ⎟
1.1φ
⎝
⎠
α
φ
β
b = 6.44 × 107 φ 3 / 2 / β
e tt g area
emitting
a ea
emitter work function
field enhancement factor
Field Enhancement Factor
β =F/V
Anode
F: electric field at emitter tip
V voltage
V:
lt
b
between
t
anode
d and
d cathode
th d
h
2
1
r
β=
∗
d
⎛ h⎞
ln⎜ 4 ⎟ − 2
r
⎝ ⎠
r
d
Spacer
r
h
Cathode
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
10
2013-02-24
Low Voltage Operation – Small workfunction
1. Small workfunction of cathode
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Low Voltage Operation – Large field enhancement
1. Large field enhancement factor
(sharp emitter tip & Short cathode to anode distance)
E
C
G
Vacuum channel transistor
G
D
S
MOSFET
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
11
2013-02-24
Relaxed Vacuum Requirement
Mean free path of electrons in air
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
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Image of the Vacuum Transistor
150 nm
-6
10
20
15
-8
10
10
-10
10
5
0
Collector current (A)
Collector c
current (μA)
25
-12
-4 -2
0
2
4
6
10
8 10 12
Gate voltage (V)
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
12
2013-02-24
Applications of Nano Vacuum Tube
High Performance
Æ Premier Audio
Æ Hifi into Smartphone
High Temperature Stability
Æ Automobile Industry
High Radiation Immunity
Æ Aerospace
A
IIndustry
d
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
Subsequent Necessary Process
Vacuum Package Process
Matured in MEMS Package
Potent Option : Wafer bonding
TSV wafer Æ bonding Æ Dicing
Wire bonding Æ Packaging
• MEMS Gyroscope
• MEMS Accelerometer
• MEMS Microphone
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
13
2013-02-24
Thank you
SF Bay Area Nanotechnology Council
February 19, 2013
Texas Instrument
14