1. Characterization and Fabrication of Thin-Film Microcrystalline Silicon
薄膜微晶矽特性分析與研製
Student : Cheng Han Tsai (蔡承翰)
Advisor : Fuh Shyang Juang Ph. D.
2018/4/24

2. Outline Introduction Research motivation
Experiment and measurement method
Results and discussion
Effects of various ratios of hydrogen diluted silane gas on crystalline characteristics of microcrystalline silicon
Effects of different substrate temperatures on crystalline characteristics of microcrystalline silicon
Effects of various RF powers on crystalline characteristics of microcrystalline silicon
Effects of different pressure on crystalline characteristics of microcrystalline silicon
Conclusion
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3. Introduction
(a) Crystalline Si
(b) Polycrystalline Si
(c) Amorphous Si
(d) Microcrystalline Si
Identification
Amorphous silicon
Microcrystalline silicon
Polycrystalline silicon
Symbol
a-Si:H
μc-Si
Poly-Si
Phase
Single phase Amorphous
Two-phase Amorphous and crystalline
Single phase Crystalline with grain boundaries
Crystalline
0~40%
40~80%
80~95%
Grain size
None
<20nm
>20nm
Si- atom
H- atom
H-passivated defect
Coordination defect
Definition of crystalline
properties of thin film
silicon materials as used in
this thesis
Fabrication and Characterization of Silicon Thin Films Using Hot-Wire CVD for Solar Cell Applications, Dong-Sing Wuu 09/6/05
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4. Gas outlet (Vacuum pumping system)
Silicon Films Deposited by PECVD
Gases inlet
RF power
SiH4 e-
Advantages:
1. Large area process
2. Low temperature process
Disadvantage:
1. Low deposition rate
2. High equipment cost
3. Plasma bombardment
Cathode
Plasma
Substrate
e- + SiH4 → Si + 4H + e-
Gas outlet (Vacuum pumping system)
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5. e- + SiH4 激發、分解 解離形式 所需能量 (eV) SiH2+H2+e- SiH3+H+e- SiH+H2+H+e-
2.2
4.0
5.7
11.9
12.32
15.3 輸送
表面反應
(成膜)
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6. Surface diffusion model
Abundant hydrogen atom fill dangling bond and defect.
The diffusion ability in the reaction process production the thin film to have SiH3 which obtain the promotion.
Etching model
The hydrogen atom etching thin film interior weak Si-Si bond and the Si-H bond.
The reaction process production the SiH3 can the strong Si-Si bond crystalline structure.
Chemical annealing model
The hydrogen atom thorough thin film loose amorphous region will carry on arrange and bond of structure.
The amorphous state to transform into the microcrystalline state.
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7. μc-Si：contains amorphous tissues crystalline grains and grain boundaries
J. Appl. Phys, Vol.87, pp.3137 (1993)
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8. Deposition μc-Si:H by hydrogen dilution method
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9. Research motivation The random phase, unstable, not crystalline.
Thin film hydrogenate amorphous Si (a-Si:H)
The random phase, unstable, not crystalline.
The conductivity is not good.
After light illumination in amorphous Si thin film.
Dangling bond of production.
Hinder electronic and the hole mobility in solar cell, the electro-optical characteristic to reduce.
Called the Staebler-Wronski Effect (SWE).
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10. Research motivation Using hydrogen dilution method
Thin film hydrogenate microcrystalline Si (μc-Si:H)
Using hydrogen dilution method
The thin film deposition by the amorphous structure gradually transforms to the microcrystalline structure.
the hydrogen atom
fill the dangling bond and defect ,
etching thin film frail Si-Si bond and Si-H bond,
increases the thin film the crystalline and the grain size,
Potential: The hydrogenate microcrystalline Si (μc-Si:H) thin film as intrinsic absorbance layer.
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11. Experiment Flow Chart Cleaning corning glass substrate
and Si wafer substrate
Material structure
analyze
Raman、XRD
Experiment parameter design,
Deposition thin films
(Pressure 、Temperature 、
RF Power 、SiH4 、H2)
Ingredient analyze
FTIR
Surface analyze
AFM
Substrate cooling
Optical quality
analyze
UV/VIS/IR
Characteristic analyze
Dark conductive
、Ea
Cleaning chamber by CF4 and O2
Electrical analyze
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12. Screen schematic drawing by PECVD
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13. Schematic drawing by PECVD
RF Power
Plasma
Gate
Substrate
Load lock O2
CF4 H2
SiH4
Turbo pump
Dry pump
Machine pump
Machine pump
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14. Measurements Raman XRD FTIR UV/VIS/IR Characterize measure
Crystalline volume fraction, Xc
XRD
Crystalline grain size
FTIR
Hydrogen content, CH
UV/VIS/IR
Photon energy, Eg
Characterize measure
Active energy, Ea
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15. Calculation Crystalline volume fraction(Xc) method
Raman spectrum of μc-Si:H into three contributions: The peak around 520cm-1 corresponds to the crystalline phase, the peak around 510cm-1 corresponds to the defective crystalline phase and the peak around 480cm-1 corresponds to the amorphous phase. (Origin, Grapher)
I510+I520
Xc=
I480+I510+I520
The I is area under the three Gaussian peaks.
Jpn. J. Appl. Phys, Vol.32, pp (1993)
In Institut de Microtechnique. 2003, Universite de Neuchatel
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16. Calculation Grain size method
Using Scherrer formula in XRD-2Θ the diffraction graph 2Θ in 28.4 degree (111) characteristic peaks, calculates in the thin film to grain size formula to be as follows:
λ is the Cu Kα wavelength ( A), β is (111) characteristic peak half at high width, θ is (111) characteristic peak in the position.
FWHM (Full Width at Half Maximum)
Mat. Res. Soc. Symp. Proc, Vol.507, pp (1998)
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17. Calculation Hydrogen content(CH) method
The hydrogen content CH was obtained by numerical integration of the Si–H rocking–wagging mode at 640 cm-1. The complete procedure can be expressed by the following equations:
A=1.6×1019cm-2 is the proportionality constant, and Nsi=5×1022cm-3 is the atomic density of pure silicon.
FTIR: Fourier Transform Infrared Spectra
J. Appl. Phys. 80 (9), 1996
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18. FTIR features in the local structural groups, SiH1, SiH2, (SiH2)n, and SiH3
Frequency (cm-1)
Assignment
SiH1
2000
Stretch
Rock
SiH2
2090
890
Bend
(SiH2)n
845, 890
SiH3
2140
845, 890
Physical Review B, Vol.19 pp.4 (1979)
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19. Calculation Photon energy (Eg) method: Energy Bandgap
Eg can be extracted using the following formula:
where h is Planck’s constant, ν is the frequency of the radiation, α is the optical absorption coefficient, and B is the edge width parameter.
The optical absorption coefficient can be deduced by transmission T and reflection R data, t is the thickness of the film.
Absorption Spectra
Solar Energy Materials & Solar Cell , Vol.92, pp (2008)
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20. Calculation Active (activation) energy (Ea) method
evaporate two parallel rectangle (rectangular?) aluminum electrodes on sample surface,
by irradiation way, we can measure the dark current value under 100V. (dark conductivity)
μc-Si:H
Glass Al D t l
100V μ
Temperature rise range approximately in 50 to 150℃, Ea obtains may make slope of the chart by ln(σd) to 1/T.
σ0 is constant, k is Boltzmann constant, T is temperature.
Ea is activation Energy; ρ is conductivity
Physical Review B, Vol.35,
pp (1987)
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21. Metal mask D
The D width is 700μm
The l diameter is 500μm l
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22. Results and Discussion
1. Effect of various ratios hydrogen diluted silane gas on crystalline characteristics of microcrystalline silicon
Results and Discussion
Structure parameter table:
Analyze of growth rate
Run
Pressure
Temperature
RF Power
Flow rate (sccm)
SiH4/ SiH4+H2 (%)
Growth times (min)
Think (A)
Growth Rate (A/s)
SiH4 H2 T1
0.7torr
250。C
300W 25
975 1% 15
1806 2 T2 37
963
1.5%
3782
4.2 T3 50
950 2%
5137
5.7 T4 62
938
2.5%
6037
6.7 T5 75
925 3%
6711
7.4 T6 87
913
3.5%
6943
7.7 T7
100
900 4%
7489
8.3
1μm=1000nm=10000Å ※SiH4：H2 dilution of 40% SiH4
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23. Deposition rate
Run
SC 1%
SC 1.5%
SC 2%
Growth Rate (A/s) 2
4.2
5.7
SC 2.5%
SC 3%
SC 3.5%
SC 4%
6.7
7.4
7.7
8.3
Deposition rate increases with decreasing hydrogen dilution ratio.
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24. Results and Discussion
1. Effect of various ratios hydrogen diluted silane gas on crystalline characteristics of microcrystalline silicon
Results and Discussion
Structure parameter table:
Fixed think 5000A
Run
Pressure
Temperature
RF Power
Flow rate (sccm)
SiH4/ SiH4+H2 (%)
Growth times (min)
SiH4 H2 S1
0.7torr
250。C
300W 25
975 1%
41m40s S2 37
963
1.5%
19m48s S3 50
950 2%
14m36s S4 62
938
2.5%
12m24s S5 75
925 3%
11m15s S6 87
913
3.5%
10m24s S7
100
900 4%
10m01s
※SiH4：H2 dilution of 40% SiH4
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25. Raman Analyze
Raman spectrum of μc-Si:H into hydrogen dilution proportion [SC, SiH4/ SiH4+H2]: 1~4%
SC 1~3% have the microcrystalline phase.
but SC 3.5~4% is the amorphous phase.
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26. Crystalline volume fraction (Xc)
Run
SC 1%
SC 1.5%
SC 2%
SC 2.5%
SC 3%
SC 3.5%
SC 4%
Xc(%)
58.3
52.9 50
46.8
41.6 ×
I510+I520
Xc=
I480+I510+I520
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27. Crystalline volume fraction (Xc)
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28. Grain size(d) by XRD Analyze
Run
SC 1%
SC 1.5%
SC 2%
d(A)
47.1
39.7
37.5
SC 2.5%
SC 3%
SC 3.5%
SC 4% ×
d is the grain size
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29. Hydrogen content(CH) by FTIR Analyze
Run
SC 1%
SC 1.5%
SC 2%
CH(%)
4.6
4.9
5.8
SC 2.5%
SC 3%
SC 3.5%
SC 4%
6.5
6.9
8.6
8.8
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30. AFM image SC 1% Ra 29.1 nm SC 1.5% Ra 27.1 nm SC 2% Ra 24 nm Run SC 1%
21.7
20.3
15.6
10.1
SC 1.5%
Ra 27.1 nm
SC 2%
Ra 24 nm
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31. AFM image SC 2.5% Ra 21.7 nm SC 3% Ra 20.3 nm SC 3.5% Ra 15.6 nm SC 4%
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32. Photon Energy (Eg) Run SC 1% SC 1.5% SC 2% Eg(eV) 1.74 1.82 1.88
1.91
1.95
1.97
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33. Photon Energy
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34. Active Energy (Activation Energy, Ea)
μc-Si:H
Glass Al D t l
100V
Active Energy (Activation Energy, Ea)
Run
SC 1%
SC 1.5%
SC 2%
SC 2.5%
SC 3%
SC 3.5%
SC 4%
Ea(eV)
0.55
0.557
0.618
0.675
0.739
0.833
0.867
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35. 1. Effect of various ratios hydrogen diluted silane gas on crystalline characteristics of microcrystalline silicon
Summy
Deposition rate decrease with increasing the hydrogen dilution.
Crystalline volume fraction (Xc) and grain size (d) of the microcrystalline Si were enhanced by：
Increasing the hydrogen dilution.
The best crystalline (Xc~58.3%) and grain size (d~47.1A) by SC 1%.
When silane concentration SC> 3.5%, transform to the amorphous Si.
The hydrogen content (CH) in microcrystalline Si was reduced by：
The lower hydrogen content (CH~4.6%) by SC 1%.
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36. 1. Effect of various ratios hydrogen diluted silane gas on crystalline characteristics of microcrystalline silicon
Summy
The surface roughness (Ra) increase with increasing the crystalline volume fraction.
The photon energy (Eg) in microcrystalline Si was reduced by：
Increasing the hydrogen dilution.
But the grain size not large causes the photon energy value high.
The active energy (Ea) in microcrystalline Si was reduced by：
Compared with photon energy, discovery fermi level is the n- type.
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37. Results and Discussion
2. Effect of different substrate temperature on crystalline characteristics of microcrystalline silicon
Results and Discussion
Structure parameter table:
Run
Pressure
Temperature
RF Power
Flow rate (sccm)
SiH4/ SiH4+H2 (%)
Growth times (min)
SiH4 H2 C1
0.7torr
200℃
300W 25
975 1%
41m40s S1
250℃ C3
300℃ C4
350℃ C5
400℃
Change temperature condition
※SiH4：H2 dilution of 40% SiH4
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38. Deposition rate
Run
200℃
250℃
300℃
350℃
400℃
Growth Rate (A/s)
2.1 2
2.07
2.08
The deposition rate does not effect by the different substrate temperature.
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39. Raman Analyze
Raman spectrum of μc-Si:H into different substrate temperature, T: 200~400℃
More to crystalline the peak intensity with the temperature increases
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40. Crystalline volume fraction(Xc)
Run
200℃
250℃
300℃
350℃
400℃
Xc(%)
48.3
58.3
62.9
66.5
70.2
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41. Crystalline volume fraction(Xc)
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42. FTIR Analyze Run 200℃ 250℃ 300℃ 350℃ 400℃ CH(%) 5.9 4.6 4.5 3.8 3.6
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43. 2. Effect of different substrate temperature on crystalline characteristics of microcrystalline silicon
Summy
The deposition rate does not effect by the substrate temperature.
The crystalline volume fraction (Xc) of the microcrystalline Si were enhanced by ：
Increasing the substrate temperature.
The best crystalline (Xc~70.2%) in the temperature 400℃.
The hydrogen content (CH) in microcrystalline Si was reduced by：
Increasing the hydrogen dilution.
The lower hydrogen content (CH~3.6%) by 400℃.
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44. Results and Discussion
3. Effect of various RF powers on crystalline characteristics of microcrystalline silicon
Results and Discussion
Structure parameter table:
Run
Pressure
Temperature
RF Power
Flow rate (sccm)
SiH4/ SiH4+H2 (%)
Growth times (min)
SiH4 H2 W1
0.7torr
250℃
100W 25
975 1%
41m40s W2
200W S1
300W W4
400W W5
500W W6
600W
Change RF powers condition
※SiH4：H2 dilution of 40% SiH4
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45. Deposition rate
Run
100W
200W
300W
400W
500W
600W
Growth Rate (A/s)
1.43
1.71 2
2.37
2.88
3.21
Deposition rate increasing with increasing the RF powers.
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46. Raman Analyze
Raman spectrum of μc-Si:H into different RF Power, W:100~600W
More to crystalline the peak intensity with the RF Power reduction.
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47. Crystalline volume fraction(Xc)
Run
100W
200W
300W
400W
500W
600W
Xc(%)
65.8
59.7
58.3
49.7 46
42.3
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48. Crystalline volume fraction(Xc)
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49. FTIR Analyze Run 100W 200W 300W 400W 500W 600W CH(%) 4.3 4.7 4.6 5.4 6
6.4
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50. 3. Effect of various RF powers on crystalline characteristics of microcrystalline silicon
Summy
The deposition rate enhanced with increasing the RF power.
The crystalline volume fraction (Xc) of the microcrystalline Si were enhanced by ：
Decreasing the RF powers.
The best crystalline (Xc~65.8%) in the RF power 100W.
The hydrogen content (CH) in microcrystalline Si was reduced by：
The lower hydrogen content (CH~4.3%) by 100W.
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51. Results and Discussion
4. Effect of different pressure on crystalline characteristics of microcrystalline silicon
Results and Discussion
Structure parameter table:
Run
Pressure
Temperature
RF Power
Flow rate (sccm)
SiH4/ SiH4+H2 (%)
Growth times (min)
SiH4 H2 P1
0.6torr
250℃
300W 25
975 1%
41m40s S1
0.7torr P2
0.8torr P3
0.9torr
Change pressure condition
※SiH4：H2 dilution of 40% SiH4
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52. Deposition rate
Run
0.6torr
0.7torr
0.8torr
0.9torr
Growth Rate (A/s)
1.83 2
2.11
2.18
Deposition rate increasing with increasing the pressure.
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53. FTIR Analyze Run 0.6torr 0.7torr 0.8torr 0.9torr CH(%) 4.5 4.6 4.8
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54. 4. Effect of different pressure on crystalline characteristics of microcrystalline silicon
Summy
The deposition rate enhanced with decreasing the pressure.
The hydrogen content (CH) in microcrystalline Si was reduced by：
The hydrogen content not to bigger change on high rate process.
The lower hydrogen content (CH~4.5%) by 0.6torr.
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55. Conclusion
Effect of various ratios hydrogen diluted silane gas on crystalline characteristics of microcrystalline silicon ：
The silane concentration SC1~3% is microcrystalline Si, when SC> 3.5%, transform to the amorphous Si by total flow is 1000sccm.
The best crystalline (Xc~58.3%) and grain size (d~47.1A) by SC 1%.
The lower hydrogen content (CH~4.6%) by SC 1%.
The surface roughness (Ra) increase with increasing the crystalline volume fraction (Xc).
Because the oxygen atom mixes in the pollution to cause the fermi level is the n- type.
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56. Conclusion
Effect of different substrate temperature on crystalline characteristics of microcrystalline silicon ：
The best crystalline (Xc~70.2%) by 400℃.
The lower hydrogen content (CH~3.6%) by SC 400℃.
The best crystalline (Xc~65.8%) by 100W.
The lower hydrogen content (CH~4.3%) by 100W.
The lower hydrogen content (CH~4.5%) by 0.6torr.
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57. 附錄
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58. Device Voc (V) J (mA/cm2) FF (%) η (%) I layer 700nm 0.37 0.219 31.46
0.0255
I layer 1400nm
0.34
0.357
33.69
0.0409
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59. ~ Thanks For Your Attention ~
2018/4/24