Structure and Properties of Si IncorporatedTetrahedral Amorphous Carbon Films Prepared

by Hybrid Filtered Vacuum Arc Process

Churl Seung Lee a), b) , Kwang –Ryeol Lee a) , Kwang Yong Eun, Ki Hyun Yoon b)

a) Thin Film Research Center, Korea Institute of Science and Technologyb) Department of Ceramic Engineering, Yonsei University

a-C:H ta-C Diamond

0

10

20

30

40

50

60

70

80

90

100

Introduction ta-C (Tetrahedral Amorphous Carbon)

– Advantages • High ratio of sp3 hybridized carbon bonds• Extreme hardness, smooth surface, thermal stability,

chemical inertness….

Har

dnes

s (G

Pa)

Introduction

ta-C (Tetrahedral Amorphous Carbon)– Disadvantage

• High residual compressive stress → poor adhesion• Many attempts have been reported

– Substrate biasing , post-annealing, boron incorporation

Si incorporation to ta-C film

Background

Si addition to a-C:H– Improved tribological properties in humid environment

– Improved the adhesion

– Enhanced the thermal stability

W.-J. Wu et al., Thin Solid Films, 307 (1997) 1K. Oguri et al., Surf. Coat. Tech., 47 (1991) 710

Motivation

Si addition to ta-C– To control the structure and the mechanical properties of ta-C

– Non-hydrogenated carbon source and solid type Si source• Prevention of the confusion in the analysis of C-H-Si bonding

configuration.

Synthesis of ta-C:Si

Bias: GroundControl parameter

Ar gas flow 10 ~ 20 SCCM

Pressure B.P.= low 10-6 torr W.P.= mid 10-4 torr

Si was incorporated in the ta-C film by simultaneous magnetron sputtering of Si during the FVA deposition.

Si Incorporation

Si in the film

C

Si in substrate

Composition

9 10 11 12 13 14 15 16 17 18

0

20

40

60

80

100

O

Si

C

Co

nce

ntr

atio

n (

at.

%)

Ar Flow (sccm)

Mechanical Properties

0 10 20 30 40 50

0

1

2

3

4

5

6

7

Res

idua

l Com

pres

sive

Str

ess

(GP

a)

Si Concentration (at.%)0 10 20 30 40 50

15

20

25

30

35

40

45

50

55

60

65

70

Hardness

Plane Strain Modulus

Si Concentration (at.%)

Har

dnes

s (G

Pa)

50

100

150

200

250

300

350

400

Plane S

train Modulus (G

Pa)

Comparison

0 10 20 30 40 500

20

40

60

80

100

Stress

Hardness

No

rma

lize

d P

rop

ert

ies

(%)

Si Concentration (at.%)

I II III

Raman Spectra & G-peak

800 1000 1200 1400 1600 1800 2000

50

37

22

8.5

4

2.5

1

0

Inte

nsity

(a.

u.)

Raman Shift (cm-1)

-5 0 5 10 15 20 40 45 50 551505

1510

1515

1520

1525

1530

1535

1540

1545

1550

1555

1560

1565

1570

1575

G-p

ea

k P

osi

tion

(cm

-1)

Si Concetration (at.%)

The Effect of Stress on G-peak Position

J.K.Shin et al., Appl. Phys. Lett., 78 (2001) 631

Stressed

Stress-relieved

Raman Spectra & G-peak

800 1000 1200 1400 1600 1800 2000

50

37

22

8.5

4

2.5

1

0

Inte

nsity

(a.

u.)

Raman Shift (cm-1)

I

II

III

0 5 10 15 20 40 45 50

1505

1510

1515

1520

1525

1530

1535

1540

1545

1550

1555

1560

1565

1570

1575

G-p

ea

k P

osi

tion

(cm

-1)

Si Concetration (at.%)

Region INo significant changes in atomic bond structure.The stress effect on G-peak position

Atomic Bond Structure

0 10 20 30 40 500

20

40

60

80

100

Stress

Hardness

Nor

mal

ized

Pro

pert

ies

(%)

Si Concentration (at.%)

I II III

Raman Spectra & G-peak

0 5 10 15 20 40 45 50

1505

1510

1515

1520

1525

1530

1535

1540

1545

1550

1555

1560

1565

1570

1575

G-p

ea

k P

osi

tion

(cm

-1)

Si Concetration (at.%)

Region IIThe initial stage of SiC phase appearanceNanocrystalline SiC related peak at 1450 cm-1

800 1000 1200 1400 1600 1800 2000

50

37

22

8.5

4

2.5

1

0

Inte

nsity

(a.

u.)

Raman Shift (cm-1)

Region IIISiC phase was dominantSi-Si bonding increased

I

II

III

The Changes of the Structure

XPSSi 2p

Si-Si C-Si

4000 3500 3000 2500 2000 1500 1000 500

Si-Cstretching

0

37

22

8.5

4

Inte

nsi

ty (

a.u

.)

Wavenumber (cm-1)

0 10 20 30 40 500

20

40

60

80

100

Stress

Hardness

Nor

mal

ized

Pro

pert

ies

(%)

Si Concentration (at.%)

I II III FTIR

Region IIISiC phase was dominantSi-Si bonding increased

94 96 98 100 102 104 106 108

50 at.%

22 at.%

Inte

nsity

(a.

u.)

Binding Energy (eV)

ta-C:Si films prepared by hybrid FVA– Si concentration can be controlled by Ar gas flow

The significant stress reduction by Si addition– Hardness was reduced by 23 % ,while stress was reduced by 48

% in low Si concentration. – Weaker Si-C bond sites relieved the stress without breaking the

three dimensional interlink.– When the Si concentration was higher than 22 at.%, the SiC

phase strongly influenced on the structure and mechanical properties.

Conclusions