Structure and Properties of Si Incorporated
Tetrahedral 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 Technology
b) Department of Ceramic Engineering, Yonsei University
Introduction
 ta-C (Tetrahedral Amorphous Carbon)
– Advantages
• High ratio of sp3 hybridized carbon bonds
• Extreme hardness, smooth surface, thermal stability,
chemical inertness….
Hardness (GPa)
100
90
80
70
60
50
40
30
20
10
0
a-C:H
ta-C
Diamond
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
K. Oguri et al., Surf. Coat. Tech., 47 (1991) 710
W.-J. Wu et al., Thin Solid Films, 307 (1997) 1
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: Ground
Control 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 substrate
C
Si in the film
Composition
100
Concentration (at.%)
C
80
60
40
Si
20
O
0
9
10
11
12
13
14
15
Ar Flow (sccm)
16
17
18
Mechanical Properties
70
7
400
350
6
60
55
Hardness (GPa)
5
4
3
2
1
300
50
Plane Strain Modulus
45
40
250
200
35
150
30
25
Hardness
100
20
0
0
10
20
30
40
Si Concentration (at.%)
50
15
50
0
10
20
30
40
Si Concentration (at.%)
50
Plane Strain Modulus (GPa)
Residual Compressive Stress (GPa)
65
Comparison
I II
III
Normalized Properties (%)
100
80
Hardness
60
40
Stress
20
0
0
10
20
30
40
Si Concentration (at.%)
50
Raman Spectra & G-peak
1575
1570
1565
50
Intensity (a.u.)
22
8.5
4
2.5
-1
G-peak Position (cm )
1560
37
1555
1550
1545
1540
1535
1530
1525
1520
1515
1
1510
0
1505
-5
800
1000
1200
1400
1600
-1
Raman Shift (cm )
1800
2000
0
5
10
15
20
40
45
Si Concetration (at.%)
50
55
The Effect of Stress on G-peak Position
Stressed
Stress-relieved
J.K.Shin et al., Appl. Phys. Lett., 78 (2001) 631
Raman Spectra & G-peak
1575
1570
50
22
8.5
II
4
2.5
1
I
0
800
1000
1200
1400
1600
-1
Raman Shift (cm )
1800
1560
-1
III
G-peak Position (cm )
Intensity (a.u.)
37
1565
1555
1550
1545
1540
1535
1530
1525
1520
1515
1510
2000
1505
0
5
10
15
20
40
Si Concetration (at.%)
 Region I
No significant changes in atomic bond structure.
The stress effect on G-peak position
45
50
Atomic Bond Structure
I II
III
Normalized Properties (%)
100
80
Hardness
60
40
Stress
20
0
0
10
20
30
40
Si Concentration (at.%)
50
Raman Spectra & G-peak
1575
1570
1565
50
22
1560
-1
III
8.5
II
4
2.5
1
I
0
800
1000
1200
1400
1600
1800
G-peak Position (cm )
Intensity (a.u.)
37
1555
1550
1545
1540
1535
1530
1525
1520
1515
1510
2000
-1
Raman Shift (cm )
 Region II
The initial stage of SiC phase appearance
Nanocrystalline SiC related peak at 1450 cm-1
1505
0
5
10
15
20
40
45
Si Concetration (at.%)
 Region III
SiC phase was dominant
Si-Si bonding increased
50
The Changes of the Structure
I II
III
FTIR
0
Intensity (a.u.)
4
8.5
80
Si-C
stretching
22
37
Hardness
60
40
4000
3500
3000
Stress
20
10
20
2000
1500
1000
500
106
108
Wavenumber (cm )
0
0
2500
-1
30
40
50
Si Concentration (at.%)
 Region III
XPS
Si 2p
Si-Si
Intensity (a.u.)
Normalized Properties (%)
100
C-Si
50 at.%
SiC phase was dominant
Si-Si bonding increased
22 at.%
94
96
98
100
102
104
Binding Energy (eV)
Conclusions
 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.