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

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Electronic Revolution from Transistors

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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)

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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

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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

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Benefit of Vacuum Channel – Speed

Silicon crystal lattice

Lattice Scattering

Velocity Saturation

= 5 X 107cm/s

Ballistic Transport

c = 3 X 1010cm/s

Vacuum

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Benefit of Vacuum – Temperature Immunity

Crystal lattice scattering in semiconductor

Vacuum Channel is immune to high temperature.

Military applications

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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

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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

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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