本研究提供一個簡單且高效能的溼蝕刻製程技術，於 (100) 單晶矽製作金字塔結構(pyramid textures)。傳統上，利用氫氧化鉀(KOH)於矽晶片上產生非等向性蝕刻，以製作金字塔抗反射結構。由於，反應進行時會於矽晶片表面釋放出氫氣，所以通常會於溶液中加入異丙醇(Isopropyl Alcohol, IPA)來降低氣泡所帶來的影響。在本研究中，利用適當開口尺寸的金屬網目，放於矽晶片表面，如同遮蔽物般將離開矽晶片表面的氣泡捕捉於網目之間，這使得非等向性蝕刻反應進行時所產生的氣泡轉變為氣態遮罩。利用這個方法，我們成功製作出3µm ~ 8µm的金字塔結構，而400nm ~ 1000nm不同波長的反射率量測平均值則小於18%。

A simple and high efficient wet etching technique for fabricating pyramid textures on (100) Si wafer is proposed. Conventionally, pyramid textures were formed on Si wafers to reduce reflections using KOH anisotropic etching. Isopropyl Alcohol (IPA) is often added to the solution to abate the bubbling effect caused by hydrogen released form the Si surfaces during reaction. In this study, a metal net with proper opening dimension was used as a shelter to trap the hydrogen from leaving the surfaces of Si, and therefore turns the hydrogen gas into a gas-type etching mask during the anisotropic etching. In this way, pyramid textures with dimensions range from 3µm to 8µm were successfully fabricated. The measured average reflectivity of the texture for incident optical wave length from 400nm to 1000nm is less than 18%.

目錄

第一章 導論…………………………………………………....... 1
1-1太陽電能原理…………………………………………… 1
1-2影響效率之因素………………………………………… 3
1-3文獻回顧………………………………………………… 4
1-3-1金字塔抗反射結構之應用……………………….. 4
1-3-2金字塔結構的抗反射機制……………………….. 7
1-3-3傳統金字塔結構的製作方法與缺點…………….. 9

第二章 單晶矽非等向性蝕刻…………………………………... 10
2-1單晶矽的晶體結構…………………………………........ 12
2-2非等向性溼蝕刻之理論………………………………… 7
2-3非等向性溼蝕刻的反應機制與影響因素……………… 11
2-4利用罩幕效應形成金字塔抗反射結構………………… 12

第三章 實驗方法………………………………………………... 13
3-1實驗設備………………………………………………… 13
3-2實驗流程………………………………………………… 14
3-3光學量測………………………………………………… 16
3-4量測方法………………………………………………… 17
3-4-1系統光源…………………………………………. 17
3-4-2光檢器轉換………………………………………. 17
3-4-3量測………………………………………………. 19

第四章 實驗結果………………………………………………... 20
4-1不同參數製程之表面形態比較………………………… 20
4-1-1不同濃度………………………………………….. 20
4-1-2不同間距……………………………...................... 22
4-1-3不同時間………………………………………….. 24
4-1-4不同溫度………………………………………….. 26
4-1-5不同網目………………………………………….. 28
4-2不同參數製程之反射率光學量測……………………… 31
4-2-1不同時間………………………………………….. 31
4-2-2不同溫度………………………………………….. 32
4-2-3不同網目………………………………………….. 33

第五章 結論……………………………………………………... 34

參考文獻…………………………………………………………. 37

圖目錄

第一章 導論
圖1-1 太陽光光譜與各種太陽電池能量分佈圖………….. 2
圖1-2 p-n接面太陽能電池能帶圖………………………… 2
圖1-3具有逆金字塔結構之太陽能電池…………………... 4
圖1-4具金字塔結構之太陽能電池………………………... 5
圖1-5金字塔結構抗反射示意圖…………………………... 5

第二章 單晶矽非等向性蝕刻
圖2-1常用立方晶體米勒指標……………………………... 7
圖2-2矽原子上之懸浮鏈與氫氧根離子(OH-)反應：
(a) (111)晶面；(b) (100)晶面……………………………. 9
圖2-3水分子對不同鍵結密度矽分子所產生的
屏蔽效應…………………………………………………. 10
圖2-4氫氣泡形成罩幕效應示意圖………………………... 12

第三章 實驗方法
圖3-1非等向性溼蝕刻反應製置…………………………... 13
圖3-2實驗步驟流程圖……………………………………... 15
圖3-3光學量測示意圖……………………………………... 16
圖3-4光學量測流程圖……………………………………... 18

第四章 實驗結果
圖4-1 於0.5% KOH蝕刻10分鐘後之表面形態………… 21
圖4-2 於1% KOH蝕刻10分鐘後之表面形態…………... 21
圖4-3 於2% KOH蝕刻10分鐘後之表面形態…………... 22
圖4-4 控制間隙為1 mm蝕刻10分鐘後之表面形態……. 23
圖4-5 控制間隙為1.5 mm蝕刻10分鐘後之表面形態….. 23
圖4-6 控制間隙為2mm蝕刻10分鐘後之表面形態…….. 24
圖4-7 KOH蝕刻10分鐘後之SEM形態圖………………. 25
圖4-8 KOH蝕刻15分鐘後之SEM形態圖………………. 25
圖4-9 KOH蝕刻20分鐘後之SEM形態圖………………. 26
圖4-10於70℃KOH水溶液蝕刻後之SEM形態圖……… 27
圖4-11於80℃KOH水溶液蝕刻後之SEM形態圖……… 27
圖4-12於90℃KOH水溶液蝕刻後之SEM形態圖……… 28
圖4-13利用1mm網目KOH水溶液蝕刻後之
SEM形態圖……………………………………………… 29
圖4-14利用1.5mm網目於KOH水溶液蝕刻後之
SEM形態圖……………………………………………… 29

圖4-15利用2mm網目於KOH水溶液蝕刻後之
SEM形態圖……………………………………………… 30
圖4-16利用2.6mm網目於KOH水溶液蝕刻後之
SEM形態圖……………………………………………… 30
圖4-17不同時間條件下生成之金字塔結構反射率………. 31
圖4-18不同溫度條件下生成之金字塔結構反射率………. 32
圖4-19不同網目條件下生成之金字塔結構反射率………. 33

1. W. Hoagland, “Solar energy”, Sci. Amer, Vol. 273, pp. 170-173, 1995.
2. G. R. Davis, “Energy for planet earth”, Sci. Amer, Vol. 263, No. 3, pp. 21-27, 1990.
3. K. N. Amulya and J. Goldemberg, “Energy for the developing world”, Sci Amer, Vol. 263, No. 3, pp. 63-71, 1990.
4. S. M. Sze, Semiconductor Device Physics and Technology, 2nd edition, John Wiley & Sons, Inc., New York, 1981.
5. D. A. Neamen, “Semiconductor physics & devices”, 2nd editon, McGraw-Hill.
6. K. Bean, “Anisotropic etching of Silicon”, IEEE Transactions on Electron Devices, Vol. ED-25, No. 10, pp.1185-1193, 1978.
7. W. Shockley, H. J. Queisser, “Detailed balance limit on efficiency of p-n junction solar cells”, phys, Vol. 32, pp. 510-519, 1991.
8. C. T. Sah, “Reduction of Solar Cell Efficiency by Edge Defects Across the Back Surface Field Junction”, Solid State Electronics, Vol. 25, pp. 851-858, 1982.
9. M. A. Green, “Limits on the open-circuit voltage and efficiency of silicon solar cells imposed by intrinsic Auger process”, IEEE, Vol. Ed31.
10. J. Y. Lin, H. L. Hwang and C. Y. Sun, “Photovoltaic Improvement of Single-Crystalline Si Space Solar Cell”, National EDMS, p. 167
11. C. T. Sah, “Reduction of Solar Cell Efficiency Across the Back Surface Field Junction”, Solid State Electronics, Vol. 31, pp.451-457, 1984.
12. J. Zhao, A. Wang, M. A. Green, “24%efficient PERL structure silicon solar cells”, IEEE, Vol. 91, pp. 333-335.
13 J. Zhao, A. Wang, M. A. Green and S. R. Wenham, “Improvements in silicon solar cell performance”, IEEE, Vol. 90, pp. 399-401, 1991.
14. U. Gangopadhyay, K. Kim, S. K. Dhungel, P. K. Basu, J. Yi, “Low-cost texturization of large-area crystalline silicon solar cells using hydrazine mono-hydrate for industrial use”, Renewable Energy, Vol.31, pp. 1906-1915, 2006.
15. A. Parretta, A. Sarno, P. Tortora, H. Yakubu, P. Maddalena, J. Zhao, A Wang, “Angle-dependent reflectance measurements on photovoltaic materials and solar cells”, optics communicatons, Vol.172, pp. 139-151, 1999.
16. Xi Z, Yang D, Dan W, Jun C, Li X, Que D, “Investigation of texturization for monocrystalline silicon solar cell with different dinds of aldaline. Renew Energy Vol. 29, pp. 2101-2107, 2004.
17. 台灣專利公開號第200620441號
18. Gregory T. A. Kovacs, Nadim I. Maluf, Kurt E. Petersen, “Bulk Micromachining of Silicon”, Proceedings of the IEEE, Vol. 86, No. 8, August, pp.1536-1551, 1998.
19. M. Elwenspoek, “The form of etch rate minima in wet chemical anisotropic etching of silicon”, Journal of Micromechanical and Microengineering, Vol. 6, pp.405-409, 1996.
20. H. Seidel, L. Csepregi, A. Heuberger, and H. Baumgartel, “Anisotropic etching of crystalline silicon in alkaline solution-PartⅠ. Orientation dependence and behavior of passivation layer”, J. Electrochem. Soc., Vol. 137, No. 11, pp. 3612-3626, 1990.
21. H. Seidel, L. Csepregi, A. Heuberger, and H. Baumgartel, “Anisotropic etching of crystalline silicon in alkaline solution-PartⅡ. Influence of dopants ”, J. Electrochem. Soc., Vol. 137, No. 11, pp. 3626-3632, 1990.
22. D. B. Lee, “Anisotropic etching of silicon”, Journal of Applied physics, Vol. 40, No. 11, pp. 4569-4574,1969.
23. P. J. Jesketh, C. Ju, and S. Gowda, “Surface free energy model of silicon anisotropic etching “J. Electronchem. Soc., Vol. 140. No. 4, pp. 1080-1084, 1993.
24. D. L. Kendall, “On etching very narrow grooves in silicon”, Applied Physics Letters, Vol. 26, pp. 195-198, 1975.
25. M Elwenspoek, “The form of etch rate minima in wet chemical anisotropic etching of silicon”, Journal of Micro mechanical and Microengineering, Vol. 6, pp. 405-409, 1996.
26. 莊達人，VLSI製造技術，高立圖書有限公司，2004
27. E. D. Palik, O. J. Glembocki, I. Heard, P. S. Burno, L. Tenerz, “Etching roughness for (100) silicon surface in aqueous KOH”, J. Appl. Phys. Vol. 70, No. 6, pp. 3291-3300, 1991.