material simulation of carbon thin film
DESCRIPTION
Material Simulation of Carbon Thin Film. Kwang-Ryeol Lee Korea Institute of Science and Technology. Seminar @ Sandia National Lab. (2005. 4. 29). People. http://diamond.kist.re.kr/DLC. Present Simulation Topics. - PowerPoint PPT PresentationTRANSCRIPT
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Material Simulation of Carbon Thin Film
Kwang-Ryeol Lee
Korea Institute of Science and Technology
Seminar @ Sandia National Lab. (2005. 4. 29)
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People
http://diamond.kist.re.kr/DLC
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Present Simulation Topics
• Novel diluted magnetic semiconductors : SiC, Diamond, GaN, GaAs, TiN, various Nanowires
• Interfacial intermixing of metallic multilayers : Asymmetry of interfacial intermixing in Al-Co, Co-Cu, Au-Pt
• Field emission simulation of doped CNTs : N and B doped CNT
• Atomic scale analysis of amorphous carbon thin film : Stress control
• Prototype TCAD for nano CMOS devices (just launched)
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SiC:TM(Si1-xTMxC) Si-substituted TM
-4 -2 0 2 4-4
-2
0
2
4
DOWN
UP
-SiC:CrSi
64 atom cell
DO
S (
Sta
tes/
eV)
E - EFermi
(eV)
Cr(3d)
-4 -2 0 2 4-4
-2
0
2
464 atom cell
-SiC:MnSi
DOWN
UP
DO
S (
stat
es/e
V)
E - EFermi
(eV)
Mn(3d)
x = 0.03 (3%)
VASP with PAW potential
Search for DMS materials
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Deposition in Co-Al System
Co on AlAl on Co
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Asymmetric Intermixing
Au on Pt (001)
Pt on Au (001) Co on Cu (100)
Cu on Co (100)
Co on Al
Al on Co
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Field Emission from CNT : Calculation
Plane wave
Localized basis
(5,5) Caped CNT, 250atoms
• Ab initio tight binding calc. To obtain self-consistent potential and initial wave function
• Relaxation of the wave functionBasis set is changed to plane wave to emit the electrons
• Time evolutionEvaluation of transition rate by time dependent Schrödinger equation
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Coupled states between localized and extended states contribute to the field emssion.
B stateA state C state D state
π*+localized stateLocalized stateπ bond:Extended state
Emission from N doped CNT
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Enhanced Field Emssion by Nitrogen Doping
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0 1 2 3 4
Pure CNT
Emitted current(μA)
Total current: 8.8A
En
erg
y st
ate
s (e
V,
E-E
F)
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0 1 2 3 4
Nitrogen doped CNT
Emitted current(μA)E
ne
rgy
sta
tes
(eV
, E
-EF)
Total current: 13.2A
AB
C
D
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Nitrogen Effect
EF
- N-doped CNT
- Undoped CNTLocalized state
The nitrogen has lower on-site energy than that of carbon atom.T. Yoshioka et al, J. Phys. Soc. Jpn., Vol. 72, No.10, 2656-2664 (2003).
The lower energy of the localized state makes it possible for more electrons to be filled in the localized states.
Doped Nitrogen Position
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
Ban
d sh
ift (
eV)
8
10
12
14
16
18
20
22
Em
ission current (A
)
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Present Simulation Topics
• Novel diluted magnetic semiconductors : SiC, Diamond, GaN, GaAs, TiN, Various Nanowires
• Interfacial intermixing of metallic multilayers : Asymmetry of interfacial intermixing in Al-Co, Co-Cu, Au-Pt
• Field emission simulation of doped CNTs : N and B doped CNT
• Atomic scale analysis of amorphous carbon thin film : Stress control
• Prototype TCAD for nano CMOS devices (just launched)
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Bond Structure of Carbon Allotropes
1S2 2S22P2
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Diamond-like Carbon
• Amorphous Solid Carbon Film• Mixture of sp1, sp2 and sp3 Hybridized Bonds• High Content of Hydrogen (20-60%)
• Synonyms– (Hydrogenated) amorphous carbon (a-C:H)– i-Carbon– Tetrahedral Amorphous Carbon
Heart valve Hard disk
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a-C:H ta-C
2-D Analogy of Structure
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High Residual Compressive Stress
Film Deposition
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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
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2 4 6 8 10 1210
20
30
40
50
60
70
80
90
100
Fallon Weiler Xu Chhowalla
sp3 f
ract
ion
Stress (GPa)
Ha
rdn
ess
Hardness and Residual Stress
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2 4 6 8 10 1210
20
30
40
50
60
70
80
90
100
Fallon Weiler Xu Chhowalla
sp3 f
ract
ion
Stress (GPa)
Ha
rdn
ess
Hardness and Residual Stress
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0 10 20 30 40 500
20
40
60
80
100
Stress
Hardness
No
rmal
ized
Pro
per
ties
(%
)
Si Concentration (at.%)
Stress Reduction by Si Incorporation
C.-S. Lee et al, Diam. Rel. Mater., 11 (2002) 198-203
S.-H. Lee et al, to be Submitted (2005)
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Molecular Dynamics Simulation
• Brenner force field for C-C bonds• Tersoff force field for C-Si and Si-Si bon
ds• Diamond substrate : 6a0 x 4.75a0 x 6a0
– 1,368 atoms with 72 atoms per layer• Deposition
– Total 2,000 atoms– Incident Kinetic Energy : 75 eV for both
C and Si– Si concentration : 0.5 % ~ 20 %
Fixed Layer
FullyRelaxedLayer
Deposited atomscreated on this plane
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Snapshots after Deposition
0.0 %
0.5 %
1.0 %
2.0 %
3.0 %
5.0 %
10.0 %
20.0 %
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0 5 10 15 20 250
1
2
3
4
5
6
7
Resid
ual S
tress[G
Pa]
Si Concentration [at.%]
Experiment
MD Simulation
Experiment : C.-S. Lee et al, Diam. Rel. Mater., 11, 198 (2002).
Residual Compressive Stress
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Atomic Bond Structure
0 5 10 15 20
0
10
20
30
40
50
60
70
80
sp
sp3
sp2
Bo
nd
Ratio
[%
]
Si Concentration [at.%]
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
eak
Pos
ition
(cm
-1)
Si Concetration (at.%)
Experiment : C.-S. Lee et al, Diam. Rel. Mater., 11 (2002) 198-203
Raman G-peak PositionMD Simulation
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2.54 Å
1.54 Å
1.0 1.5 2.0 2.5 3.0 3.5 4.0
0
2
4
6
C- CSatellite
C- C1st:1.54 A
Rad
ial D
istr
ibutio
n F
unc.
[g
(r)]
Distance [A]
C- C2nd:2.54 A
Radial Distribution of Pure a-C and Diamond
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Radial Distribution Function
1.0 1.5 2.0 2.5 3.0 3.5 4.0
0
3
6
9
12
15
18
212.54 A
20 at.%
5 at.%
3 at.%
1 at.%
0.5 at.%
C- C satellite
Si- Si1st,C- C2ndSi- C1st
Rad
ial D
istr
ibutio
n F
unc.
[g
(r)]
Distance [A]
C- C1st
Pure ta- C film0 5 10 15 20 25
0
1
2
3
4
5
6
7
Resid
ual S
tress[G
Pa]
Si Concentration [at.%]
Experiment
MD Simulation
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Carbon for Satellite Peak
93.1°94.2°
2.184 A
2.185 A
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60 80 100 120 140
0
20
40
60
80
100
120
0.5 at.% Si Incorporation
No
rmalized
Co
unt
Ratio
[%
]
Angle [Degree]
Pure ta- C
109.5° 120.0°
Bond Angle Distribution
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W-DLC by Hybrid Ion Beam Deposition
Sputter gun: Third elements addition to DLC (W, Ti, Si …);
Ion gun: Easy controlling the ion bombardment energy with high ion flux.
Wn+
H+, Cm+
A.-Y. Wang et al, Appl. Phys. Lett., 86, 111902 (2005).
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0 2 4 6 8 101.0
1.5
2.0
2.5
3.0
3.5
Res
idua
l str
ess
(GP
a)
W concentration (at.%)
(a)
-1 0 1 2 3 4 5 6 7 8 9 1015
20
25
30
35
40
45
100
120
140
160
180
200
Ela
stic
mod
ulus
(GP
a)
Har
dnes
s (G
Pa)
W concentration (at.%)
hardness
elastic modulus(b)
Stress & Mechanical Properties
21±3 GPa
170±15 GPa
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TEM Microstructures
8.6
4 nm
-W2C(102)
-W2C(101)
1.9
4 nm
W atoms are dissolved in a-C:H matrix.
Nano-crystalline -W2C phases evolve.
4 nm
3.6-W2C (101)
-W2C 4 nm
2.8
0 2 4 6 8 101.0
1.5
2.0
2.5
3.0
3.5
Res
idu
al s
tres
s (G
Pa)
W concentration (at.%)
(a)
Amorphous to crystalline WC1-x transition occurs.
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Raman & EELS Spectra
400 600 800 1000 1200 1400 1600 1800 2000
3.6
2.8
W 1.9 at.%
6.0
4.7
Inte
nsity
(a.u
.)
Wave number (cm-1)
8.6
(a)
0 1 2 3 4 5 6 7 8 9 10
1551
1554
1557
1560
1563
1566
1569
G-P
eak
posi
tion
(cm
-1)
W concentration (at.%)
(b)
I/I = 0.550.1
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TEM Microstructures
8.6
4 nm
-W2C(102)
-W2C(101)
1.9
4 nm
W atoms are dissolved in a-C:H matrix.
Nano-crystalline -W2C phases evolve.
4 nm
3.6-W2C (101)
-W2C 4 nm
2.8
0 2 4 6 8 101.0
1.5
2.0
2.5
3.0
3.5
Res
idu
al s
tres
s (G
Pa)
W concentration (at.%)
(a)
Amorphous to crystalline WC1-x transition occurs.
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90 100 110 120 130
0.00
0.08
0.16
0.24
0.32
0.40
0.48
0.56
0.64
Tota
l ene
rgy
vari
atio
ns, (
eV)
Bond angle (degree)
C-C bond W-C bond
Role of W atoms- ab initio calculation
C
CH
W
CH
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Conclusions
• Various properties of a-C films generated by MD simulation agrees well with those of experimentally obtained a-C films.– Brenner force field for C-C bond– Tersoff force field for Si-Si and Si-C bond
• Stress reduction mechanism based on the atomic scale structure analysis– Small amount of Si incorporation in a-C network effectively
relaxes the distorted bonds. – W atoms dissolved in a-C matrix play a role of pivot site w
here the atomic bond distortion can occur without inducing a significant increase in elastic energy.
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Newly Launched Project @ KIST
• Massive MD/MC simulation technology to understand atomic scale phenomena of 100 million atoms system.
• Electron transport analysis technology to characterize nano-device.
Next Generation Prototype TCAD for nano CMOS FET simulation
Next Generation Prototype TCAD for nano CMOS FET simulation
Effect of atomic scale interfacial structureon the performance of nano-scale CMOS device
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Technology Oriented CAD (TCAD)
• using computer simulations to develop and optimize semiconductor processing technologies and devices
• Process CAD + Device CAD
• using computer simulations to develop and optimize semiconductor processing technologies and devices
• Process CAD + Device CAD
Process CAD Device Structure Device CAD
Device Properties
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Next Generation TCAD for Nano-devices
• Atomic scale description of the devices • Electron transport in subatomic scale
and via non-continuum media
• Atomic scale description of the devices • Electron transport in subatomic scale
and via non-continuum media
Device StructureDevice CAD
Process CAD
Device Properties
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CMOS FET : Scale down issue
1~3nm
0.13 m
<10 nm
1. Atomic scale oxide-channel structure simulation
2. Device characterization for various interface structures
1. Atomic scale oxide-channel structure simulation
2. Device characterization for various interface structures
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Research Flow
3 Tflop Cluster Supercomputing Environment (KIST)
Process SimulationBased on Massice MD/MC simulation
Device Simulation Based on TB Theory and Electron Drift Theory
KIST KIAS
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KIST Supercomputer : grand.kist.re.kr
• Calculation Nodes : 512 nodes– Intel Xeon 2.4GHz Dual – RedHat7.3 Kernel 2.4.20 SMP– Myrinet PCI-X D/Cisco Gigabit SW– 2G PC2100 ECC SDRAM– IDE 80GB HDD
Storage Node
512 Computing Nodes
Myrinet
Public Network
Head Node
3.07 TFlops
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What we have to do
• Have a massive MD/MC code with wide range of applicability, which can cover various processes such as deposition, oxidation, diffusion, implantation and other nano-scale processes.
• Obtain oxide potentials for Si-O and Hf-O and integrate into the massive MD code.
• Visualize the 100 million atoms assembly and characterize the atomic scale structures (bulk and interface).