Single Crystal Diamond NEMS Switch

Meiyong LiaoOptical and Electronic Materials Unit

National Institute for Materials Science, Japan

普段の生活のエネルギー消費を減らす必要！

ナノマシンスイチ：省エネルギー技術（ゼロ）として期待 。

待機電力消費---半導体スイッチ

機器が非使用状態、若しくは何らかの入力（命令指示）待ちの時に定常的に消費している電力

平成２０年度

1-5 W

5-10W

MEMS switch: Merits

Poor

Poor

Poor（<25dB）

Large （＞１ｄＢ）

Fast （１0ns）

>1 uW

Large

Semiconductor switch

Excellent

Excellent

Good（>30dB)

Small（<0.2dB)

Slow （10µs）

~0

zero

MEMS switch

High and low temperatures

Linearity

Isolation

Insertion loss

Speed

Power loss

Leakage

Property

Advantages over semiconductor devices

But, poor reliability due to (i) Surface stiction(ii) Mechanical abrasion

Semiconductor devices consume power in OFF state!

VGVD

A

カンチレバー

ドレイン ゲート

ソース

OFF state

VD

A

VG

ドレイン ゲート

ソース

ON stateMEMS switch

Diamond MEMS: route toward high reliability and high performance

2 3 4 5 6 7 8

2500

5000

7500

10000

12500

15000

17500

20000

2L

dEfρ

∝

GaN

ZnO

Ni

Si3N

4

Si

Au

SiC

Diamond

AlN

W

Fe

Accoust

ic v

elo

city

(m/s)

Lattice constant (A)

The highest Young’s modulus

The lowest friction coefficient

Hydrophobic surface

Highest thermal conductivity

Tunable electrical conductivityThe best material

Merits

Current MEMS: intrinsic limitations !!

Challenges and Strategies in Diamond MEMS

What process….? What device concept……?

DifficultiesBatch fabrication of single crystal diamond MEMS structures.Lack of device concepts compatible with the fabrication

process.

AimsEstablish unique process for diamond MEMS structures. Develop high-performance diamond MEMS/NEMS devices.Create novel device concepts.

StrategiesNo direct deposition of diamond on sacrificial layers. Diamond-on-Diamond lateral device concept.

Diamond growthMPCVD

Parameters:Gas: H2 (500 sccm)， CH4 (0.4 sccm)RF Power: 400 WPressure: 80 TorrSub. Tem: 900-950oC[B]:1000 ppm 1020cm-3

Substrate: Ib (100)---100 ppm nitrogenThickness: 0.1-0.5µm

Batch production of micro-scale M/NEMS structures

air gap

M. Y. Liao, et al, J. Micromech. Mircoeng. 20，085002 (2010)

W=400nm

W=200nm

W=200nm

M. Y. Liao, et al,Advanced Materials 22, 5393 (2010)

Quality of the MEMS/NEMS structure

1000 1100 1200 1300 1400 1500 16000.2

0.3

0.4

0.5

0.6

0.7

Inte

nsi

ty (

a.u.)

Wavenumber (cm-1)

260 280 300 320 340 360 380

π∗

Counts

(a.

u.)

Energy loss (eV)

Protection Pt layer

Boron doped diamond

diamond

graphite

diamond

Nanoindentation of MEMS structures

Young’s modulus: 800±200 GPa (Calibrated by Si cantilever)

xdiasixm kkk −−

+=111

AFM

M. Y. Liao, et al, J. Micromech. Mircoeng. 20，085002 (2010)

Nanoelectromechanical switch: 2-terminal

0 2 4 6 8 10 12 14 16 18 2010-14

10-13

10-12

10-11

10-10

10-9

Cur

rent

(A)

Voltage (V)0 10 20 30 40 50 60 70 80

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Curr

ent

(A)

Voltage (V)0 5 10 15 20

10-14

10-13

10-12

10-11

10-10

10-9

10-8

Cur

rent

(A)

Voltage (V)

A A A

Nanoelectromechanical switch: 3-terminal

-80 -60 -40 -20 010-16

10-14

10-12

10-10

10-8

1st 2nd 3rd

Dra

in c

urre

nt (A

)

Gate voltage (V)-80 -60 -40 -20 0 20 40 60 80

10-13

10-12

10-11

10-10

10-9

10-8

Dain voltage =10 V

Dra

in c

urre

nt (A

)

Gate Voltage (V)

2µm

5µmON-stateOFF-state

VG

A

D

VD

G

S

0 50 100 150 20010-14

10-13

10-12

10-11

10-10

Cur

rent

(A)

Time (s)

3-T NEMS switch: Reliability

S

G

D

OFF-state

~VG

A

105 switching cycles

0 500 1000 1500 2000 2500 3000

10-14

10-13

10-12

10-11

Gate votage off

Curr

ent

(A)

Time (s)

100Hz AC VG

0 10 20 30 40 5010-16

10-14

10-12

10-10

10-8

10-6

10-4

10-2

150 oC

200oC

250oC

Curr

ent

(A)

Voltage (V)

High temperature operation

Modeling and simulation of NEMS switch

Gate DrainSource

0V)(ε =∇⋅∇−

Tes DE)(nnD)(E

21F ⋅+⋅−=

Potential in the air around the beam

Fes: Electrostatic force density of the beamE: electric field, D: displacement vector

Pull-in voltage: defined as the beam contact to the gate.L: length, W: width, t: thickness

B=E0t3g3

)Wgc(1cLε

B4cV3

22

40

1inpull

+=−

Modeling and simulation of NEMS switch

Comparison between experiment and simulation:

0 10 20 30 40 500

20

40

60

80

Pul

l in

voltag

e (

V)

Drain voltage (V)

0 10 20 30 40 50 60 70 80 900

200

400

600

800

1000

Str

ess

(M

Pa)

Gate voltage (V)

High Young’s ModulusGood reproducibility Consistence between experiment and simulationYoung’s modulus=1100GPa

Joint stress much lowerthan fracture strength

Drain voltage affecting pull-in voltage

Applications of diamond M/NEMS Switch: H4

携帯電話や無線LANなどの無線通信

耐環境デバイス：高温論理回路

メモリ

（待機ゼロ）電源制御装置

ナノ・マクロマシンスイッチ

High

power Hightemperature

High

frequencyHighreliability

Summary

For the first time

Single-crystal diamond NEMS switch was fabricated.

Batch production of SCD MEMS/NEMS structures were developed.

The diamond NEMS switches exhibit high performance.(1) High controllability .(2) High reproducibility.(3) Good reliability.

Modeling and simulation were made and were consistent with experiments