다이아몬드상 카본필름의 잔류응력과 기계적 물성
DESCRIPTION
다이아몬드상 카본필름의 잔류응력과 기계적 물성. 한국기계연구원 2001. 8. 7 한국과학기술연구원 이 광 렬. Outline. 다이아몬드상 카본필름의 소개 다이아몬드상 카본필름의 일반적 특성 장단점 및 응용 박막의 잔류응력 잔류응력의 종류 잔류응력의 측정 다이아몬드상 카본필름의 잔류응력 잔류응력의 발생거동 및 영향 제삼원소 첨가에 의한 잔류응력의 제어 잔류응력을 이용한 박막의 탄성계수평가. Carbon Atomic Bond Structure. What is DLC ?. - PowerPoint PPT PresentationTRANSCRIPT
다이아몬드상 카본필름의 잔류응력과 기계적 물성
한국기계연구원2001. 8. 7
한국과학기술연구원이 광 렬
Outline
• 다이아몬드상 카본필름의 소개– 다이아몬드상 카본필름의 일반적 특성– 장단점 및 응용
• 박막의 잔류응력– 잔류응력의 종류– 잔류응력의 측정
• 다이아몬드상 카본필름의 잔류응력– 잔류응력의 발생거동 및 영향– 제삼원소 첨가에 의한 잔류응력의 제어
• 잔류응력을 이용한 박막의 탄성계수평가
Carbon Atomic Bond Structure
What is DLC ?
• Amorphous Solid Carbon Film• Mixture of sp1, sp2 and sp3 Hybridized Bonds• High Content of Hydrogen (20-60%)
• Synonyms– Diamond-like Carbon– (Hydrogenated) amorphous carbon (a-C:H)– i-Carbon– Tetrahedral Amorphous Carbon
a-C:H ta-C
Properties of Solid Carbon
Property Diamond DLC Graphite
Density (g/cm3) 3.51 1.8 – 3.6 2.26
Atomic Number Density (Mole/cm3)
0.3 0.2 – 0.3 0.2
Hardness (Kgf/mm2) 7000 - 10000 2000 - 8000 <500
Friction Coeff. 0.05 0.03 – 0.2
Refractive Index 2.42 1.8 – 2.6 2.15 – 1.8
Transparency UV-VIS-IR VIS-IR Opaque
Resistivity (cm) >1016 1010 - 1013 0.2 – 0.4
Historical Survey
• 1972– Aisenberg and Chabot : Arc Ion Beam
• 1979– Holland and Ohja : PACVD
• 1984– Mori and Namba : Ion Plating
• 1986– Savvides : Sputtering
• 1992– Collins et al : Laser Ablation– Filtered Vacuum Arc
Deposition Methods
Energy
Ion Source
Cold Substrate
Impa
ct E
nerg
y (e
V)
1
10
100
1000
Amorphous Carbon
(sp2)
DenseCarbon
CarbonSource
HydrocarbonSource
DenseHydro-Carbon
PolymerLike
Carbon
PlasmaPolymers
Energy Dependence of DLC
Ion Energy Distribution
PACVDPACVD
Examples of Deposition Methods
Examples of Deposition Methods
합성방법의 특징합성 방법 특징
PECVD (DC, HF, RF,ECR, pulsed DC)
High Productivity, Very Smooth FilmLow Hardness & Thermal StabilityNon Uniform in Complicated Shape
Sputtering : ion beam Process Compatibility for HDD Low Adhesion, Poor Film Quality
Ion Beam Deposition
Medium Hardness, Medium ProductivityUniform Coating for Complicated Shape
High Residual Stress, Poor AdhesionComplicated Deposition System
Laser Ablation High Adhesion & HardnessLow Productivity
FVA(Filtered Vacuum Arc)
High Hardness & Thermal Stability High Residual Stress, Poor Adhesion
Properties of Solid Carbon
Property Diamond DLC Graphite
Density (g/cm3) 3.51 1.8 – 3.6 2.26
Atomic Number Density (Mole/cm3)
0.3 0.2 – 0.3 0.2
Hardness (Kgf/mm2) 7000 - 10000 2000 - 8000 <500
Friction Coeff. 0.05 0.03 – 0.2
Refractive Index 2.42 1.8 – 2.6 2.15 – 1.8
Transparency UV-VIS-IR VIS-IR Opaque
Resistivity (cm) >1016 1010 - 1013 0.2 – 0.4
Major Points of DLC Films
• Low Deposition Temperature (R.T. – 200oC)– No limitation of Substrate Materials
• Smooth Surface– Roughness : few nm
• Wide Range of Physical Properties– Tunability of the Properties
• Uniform Large Area Deposition– High Productivity and Low Cost
AFM Image of DLC coated Si
IR Transmittance of DLC Coated Ge Windows
Courtesy of J&L Tech. Ltd
Minor Points of DLC Films
• Thermal Instability– Degradation at High Temperature (400 – 600oC)
• High Residual Compressive Stress– Max. 10 GPa
• Poor Adhesion– Stable Chemical Bonds
– Especially on Ferrous Materials
Structure and Mechanical Properties
• Hardness– 3-D interlink of the
atomic bond network
• Residual Stress– Distortion of bond angle
and length
• Both are dependent on the degree of 3-D interlinks.2-D Analogy of the Structure
Self Delamination Failure during Tribotest
DLC 필름의 특성과 응용구 분 특 성 응 용
High hardness
Low friction andhigh wear resist.
Chemical Inertness
Optical Transmittance
2,000 - 8,000Hv(cf. Diamond 10,000Hv)
마찰계수 0.05 - 0.2(cf. Stainless Steel : 0.6 - 0.7)
산 또는 알카리와 반응치 않는다
특히 적외선 영역의 높은 광투과도
비철금속 가공용 공구 ,정밀금형의 표면경화코팅
치구 , GEAR, SURGICALBLADE, HARD DISK 등의 고체 윤활 코팅
부식 방지막 , 인체삽입물의BIO-COMPATIBLE COATING
IR WINDOW, SCANNERWINDOW 의 표면보호 코팅
경질박막의 내마모 윤활특성
DLC
WC
TiN
CrN
TiCN
마모도 마찰계수 .
2.0 1.6 1.2 0.8 0.4 0.2 0.4 0.6 0.8 1.0( 상대비교치 )
DLC 필름의 특성과 응용구 분 특 성 응 용
High hardness
Low friction andhigh wear resist.
Chemical Inertness
Optical Transmittance
2,000 - 8,000Hv(cf. Diamond 10,000Hv)
마찰계수 0.05 - 0.2(cf. Stainless Steel : 0.6 - 0.7)
산 또는 알카리와 반응치 않는다
특히 적외선 영역의 높은 광투과도
비철금속 가공용 공구 ,정밀금형의 표면경화코팅
치구 , GEAR, SURGICALBLADE, HARD DISK 등의 고체 윤활 코팅
부식 방지막 , 인체삽입물의BIO-COMPATIBLE COATING
IR WINDOW, SCANNERWINDOW 의 표면보호 코팅
Applications of DLC Film
Video Cassette Recorder
DLC 코팅 VTR 헤드드럼
Courtesy of Daewoo Electronics Co.
DLC Coated Digital VCR Tape
HDD 용 Hard Disk
DLC coated Head Slider
DLC Coated Razor Blade
Schematic of Diesel Engine
Results of Wear Test under Dry Lubrication Conditions
0 5000 10000 15000
0.2
0.3
0.4
0.5
DLC coated Ring
Hard Cr Ring
No-lubricant conditionLoad 50N
Fric
tion
Coe
ffic
ient
Number of Cycle.
Hard Cr Coated Ring DLC coated Ring
Before Test Before Test
After Test After test
Result of Dynamo Test (900h)
Before Test Before Test
After Test After Test
100m6.5m
5.3m
Hard Cr Coated Piston Ring
DLC/Cr Coated Piston Ring
Sliding Tools for Electron Gun
• Grids (2) manipulate the electron beam.
• Sliding Tools is used to make spacing between the grids (Tolerance is about 4m)
• Smooth grid surface and parallel positioning are important.
DLC Coated Sliding Tools
• Low friction
• Long life time
• Electrical insulation
• No corrosion on the shelves
Courtesy of J&L Tech. Co., Ltd.
IC Packaging
• 반도체 packaging 용 EMC mold cavity 의 이형성 증진 및 수명연장을 위한 코팅
DLC Coating on Packaging Tools
Courtesy of J&L Tech. Co., Ltd.
인공 고관절 및 무릎관절
고관절
무릎관절
DLC Coating for Wear Resistance
Biological Application of DLC
인공 심장 , 수정체
인공심장 판막 인공수정체
DLC Coated Stents
Load
Ruby BallTest disk
Saline
Load :
High &Low
Surroundings :
Wet Condition
Dry Condition
Schematic of Wear Tester
Dry Wet
DLC on Ti
DLC on Ti-Alloy
Condition :
High Load
3000 cycle
Dry Wet
Wear Volume
0.026 mm3
0.021mm3
0.002mm3
0.002 mm3
Wear Volume
Dry Wet Dry Wet
Fracture Cycle
92250 cyc
6750 cyc
10250 cyc
3172 cyc
Condition :
High Load
DLC on Ti
DLC on Ti-Alloy
Life Time of DLC Coatings
IR Windows for Missile and Night Vision System
IR Transmittance of DLC Coated Ge Windows
Sand Blast Type Erosion Rig
J. E. Field, Carvendish Lab. Cambridge University
Solid Particle Impact Erosion
Damage Pattern of Multilayer Coated Ge windows
200 sec
600 sec
Ge
510nm a-Si
1900nm DLC
690nm a-Si
1000nm DLC
Multilayer Structure
DLC Coated CD-R Pressing Die
Courtesy of J&L Tech. Co., Ltd.
CD Surface Formed by Using Uncoated Mold
RMS roughness = 1.31nm
CD surface formed by using DLC coated mold
RMS roughness = 0.95nm
Residual Stress of Thin Films
• Thin films typically support very high stresses due to the constraint of the substrate to which they are attached– Normally at near failure stress!– Determines mechanical behaviors of the coating and devices
(elastic distortion, plastic deformation, fracture, adhesion)
Substrate Interaction Stresses Intrinsic Stresses
Relative Dimensional Change after Growth
Thermal Stress
Epitaxial Stress
Interfacial Stress
Structure Evolution During Growth
Relative Dimensional Changes
Condition : Adhesion between film and substrate Any process that changes the in-plane dimension of the film relative to that of the substrate
Thermal Stress
Condition : Difference in thermal expansion coeff. Difference in temperature
Epitaxial Strains
Condition : Coherency with different lattice parameters
Interfacial Stresses
Condition : Inherent but significant in very thin film or multilayer
Intrinsic Stress (Growth Stress)
Residual Stress of Thin Films
Measurement of Residual Stress
• Assumption– 1-D Treatment of Elastic
Equilibrium
– Sufficient Adhesion
– df << ds
– ds << R
sff
ssf
ss
ff
f
ssf
ddd
dY
R
dE
dE
d
dY
R
for 6
1
16
1
2
2
sff
ssf
ss
ff
f
ssf
ddd
dY
R
dE
dE
d
dY
R
for 6
1
16
1
2
2
Curvature (R)
dsdf
ss
ff
f
bf
sfbf
dY
dY
R
dY
3
2
ss
ff
f
bf
sfbf
dY
dY
R
dY
3
2
Stress of Multilayer
Ko
K1
K2
11 foKK
212 fKK f1
f1
f2
2
21
14 f
s
f
s
ff d
d
Y
Y 2
21
14 f
s
f
s
ff d
d
Y
Y
Measurement of Curvature
dx
dK
sin
dx
dK
sin
X-ray Strain Measurement : sin2Method
d
sin2
dE
dE
d ff )2
1(sin1 2
Angle between normal vector and scattering vector
d
dEf
2sin/
1
d
dEf
2sin/
1
Typical Behavior of Residual Stress of DLC Films
0 50 100 150 200 250
0.5
1.0
1.5
2.0
2.5
3.0
)V/mTorr(/ 1/2PVb
)V/mTorr(/ 1/2PV b
Res
idua
l Com
pres
sive
Str
ess
(GP
a)
ta-C by FVA a-C:H by rf-PACVD
High Residual Stress
Instability of Coating and Device
The Effect of Stress on Raman G-peak Position
J.K.Shin et al., Appl. Phys. Lett., 78 (2001) 631
Stressed
Stress-relieved
4.1cm-1/GPa
T : Elastic energy
U : Bending strain energy
Δγ : Surface energy
=(- fs+ fv+ sv)
fsT
svfvU
22
2)1(3
B
B
B
ut
tE
22
2)1(3
B
B
B
ut
tE
BB UT
0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36-10
-5
0
5
10
15
20
25
30
(J
/m2 )
Thickness(m)
Fundamental Adhesion
Energy Dependence of DLC
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)
Reduction of Hardness and Residual Stress
0 10 20 30 40 500
20
40
60
80
100
Stress
Hardness
N
orm
aliz
ed P
rope
rtie
s (%
)
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)
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)
I
II
III
The Changes of the Structure
XPSSi 2p
Si-SiC-Si
4000 3500 3000 2500 2000 1500 1000 500
Si-Cstretching
0
37
22
8.5
4
Inte
nsity
(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 reduce
d by 48 % in low Si concentration. – Weaker Si-C bond sites relieved the stress without brea
king 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
압축 잔류 응력을 이용한 박막의 탄성계수 평가
• Mechanical properties of thin films are not the same as those of materials having the sample composition in bulk form– High quench rate in deposition process
– High defect densities and textures
– Non-equilibrium compositions
– Confinement of dislocations, craction, etc. in small dimensions
Nano-Indentation
• Initial unloading is pure elastic.
• Sneddon’s elastic contact theory
E1 2
Nano-indentation Results
0 50 100 150 200 250 300 350
100
200
300
400
500
600
700 500nm ta-C on Si 500nm ta-C on Al
CSM
Ela
stic
Mod
ulus
(GPa
)
Displacement (nm)0 50 100 150 200 250 300 350
100
200
300
400
500
600
700 200nm ta-C on Si 200nm ta-C on Al
CSM
Elas
tic M
odul
us (G
Pa)
Displacement (nm)
Sonic Vibration and Laser-Acoustic Technique
Sonic Vibration Laser-Acoustic
Bulge Test
4
3
221 r
hMtc
r
htcP o
)1/( EM For Isotropic Film
Key Idea of the Present Method
1
E
For Isotropic Thin Films
DLC film Deposition
Cleavage along [011] Direction
Si Etching (by KOH Solution) Wet Cleaning
Strain Measurement
Preparation of Freehang
Strain From DLC Bridge by Micro Fabrication
DLC film Deposition ( on SiO2 )
DLC PatterningSiO2 Isotropic Wet Etching
Wet Cleaning
Strain Estimation
Microstructure of DLC Bridges
C6H6, 10mTorr, -400V, 0.5m
150m
Strain of the Buckled Thin Films (I)
xco
E
)1(
t
D
xAxW
x
Wt
x
WD
c
o
c
x
WWx
x
WWx
2
2
2
2
4
4
4
2cos1)(
0
0 ,2
at
0 ,2
at
Z
X
2A0
Stain of the Buckled Thin Films (II)
2
2
2
2
2 2
11
2
1
ox
x
x
A
dxx
W
x
W
cooA
E
2
1
0
131
1
13
1
,4
From
2
22
2
2
2
t
A
t
E
t
D
oo
c
c
c
ooA
E
2
1
Elastic Modulus for Various Ion Energies
0 100 200 300 400 500 600 700 800
0
50
100
150
200
250
Pla
ne
Str
ain
Mod
ulus
(G
Pa
)
Negative Bias Voltage (V)
Nanoindentation t>1.0 ㎛
100 200 300 400 500 600
0
50
100
150
200
Bridge Method
Freehang Method
E/(1
-)
(GPa
)
Negative Bias Voltage (V)
Advantages of This Method
– Simple Method
– Completely Exclude the Substrate Effect
– Can Be Used for Very Thin Films
The possibility of elastic modulus measurement in very thin film
Elastic Modulus of Very Thin Films
0 200 400 600 800 1000 1200
25
50
75
100
on Si on W / Si on SiO
2/ Si
Bia
xial
Ela
stic
Mod
ulus
(GPa
)
Thickness (nm)
a-C:H, C6H6 -400V
J.-W. Chung et al, Diam.Rel. Mater. in press (2001)
ta-C (Ground)
Residual Compressive Stress & G-peak Position of Raman
0 50 100 150 200 2501520
1525
1530
1535
1540
1545
1550
1555
G-p
eak
Pos
ition
(cm
-1)
Vb / P1/2 (V/mTorr1/2)
0 50 100 150 200 250
0.5
1.0
1.5
2.0
2.5
3.0
Res
idua
l Com
pres
sive
Stre
ss (G
Pa)
Vb / P1/2 (V/mTorr1/2)
Biaxial Elastic Modulus
0 100 200 300 400 500 6000
50
100
150
200
Bia
xial
Ela
stic
Mod
ulus
(GP
a)
Thickness (nm)
0 50 100 150 200 250
0.5
1.0
1.5
2.0
2.5
3.0
Res
idua
l Com
pres
sive
Str
ess
(GP
a)
Vb / P1/2 (V/mTorr1/2)
20
233
166
100
G-peak Position of Raman
0 300 600 900 12001520
1530
1540
1550
1560
G-p
eak
Pos
ition
(cm
-1)
Thickness (nm)
0 50 100 150 200 250
0.5
1.0
1.5
2.0
2.5
3.0
Res
idua
l Com
pres
sive
Str
ess
(GP
a)
Vb / P1/2 (V/mTorr1/2)
20
233
166
100
0 300 600 900 12001520
1530
1540
1550
1560
G-p
eak
Pos
ition
(cm
-1)
Thickness (nm)
233
166
100
20
Schematic Film Structure
Si Substrate
Si Substrate
Si Substrate
0 100 200 300 400 500 6000
50
100
150
200
Bia
xial
Ela
stic
Mod
ulus
(GP
a)
Thickness (nm)
Conclusions
Using the free overhang method, we could accurately measure the biaxial elastic modulus of very thin DLC film.
(down to 50nm).
The structural evolution in the initial stage of the film growth depended on the deposition conditions.
- At the optimum ion energy, the film exhibited a fixed elastic modulus and G-peak position regardless to the film thickness.
- On the other hand, the structural evolution during the initial stage of the film deposition was significant in the films of high content of polymeric or graphitic component.
Acknowledgement
• Financial Support– 과기부 한러협력기술개발사업 (91-94) – 과기부 선도기술개발사업 (94-01)– 과기부 중소기업지원사업 (97)– 산자부 산업기반기술개발사업 (99-01)– KIST 기관고유사업 (92-00)– 산업체 : 대우전자 , 대우중공업 , 제이엔엘테크
• Researchers– Postdoc : 오제욱 , 최준엽 , 신진국– 위촉연구원 : 김성화 , 김종국 , 김명근– 학생연구원 : 조성진 , 이철승 , 박세준 , 정진원