p型矽薄膜的應用在IC產業或是太陽能電池領域中佔有相當的比重，製造p型矽層的方法有許多種類，而在工業界較廣為利用的是離子佈植以及擴散的方式。離子佈植過程中會造成基板表面形成許多因離子轟擊造成的缺陷，必須以高溫熱退火(800oC)來將其修補。而擴散的方式也必須經由高溫的催化(硼約900oC)，使掺雜物在基板表面反應形成後，再利用熱擴散的方式達到預期的深度，這兩種製造p型矽薄膜的製程都有著因高溫造成的熱預算問題，對於後製程有很大的影響。
若利用鋁誘發結晶方式成長p型矽薄膜，可在較低溫(400oC)的溫度下完成。但載子濃度相較離子佈植和擴散法低(3x1018cm-3,後者約1019-1020cm-3)，導致可利用的價值相對下降。本實驗利用硼共濺鍍於鋁膜內的方式使硼存在於成長後的p型矽薄膜內，並提供電洞。在一定溫度下，硼在矽中的固相溶解度較鋁高，因此可以在低溫情況下(400oC)得到較傳統鋁誘發結晶高的載子濃度(1019cm-3)。
低溫達高掺雜的技術可應用的層面很廣，對以離子佈植和擴散方式製造的太陽能電池射極部份來說，此硼共濺鍍的方式可使高溫造成的熱預算問題降至最低。此外，太陽能電池中的背面電場部份是由網印方式形成，一樣必須經過700oC以上的熱處理才可完成背面電場的製作，由於鋁和矽的熱膨脹係數不同，高溫時易導致因熱膨脹造成的表面應變殘留，甚至使晶圓變形破裂。
因此本研究將硼共濺鍍應用於固相磊晶法上，使得在400oC即可達1019cm-3的掺雜濃度，不但突破了傳統鋁誘發結晶的載子濃度限制，也有機會將鋁誘發結晶法應用於現今太陽能電池或IC產業中製造p型矽薄膜的製程。

The Back-Surface-Field structure is usually fabricated by screen-printing technology, and the emitter is produced by ion implantation or diffusion in solar cell. Although all of these methods obtain continuous and high carrier concentration p-type silicon film, the processes must undergo a heat treatment above 800oC. It causes some critical issues such as thermal budget problem and residual strain energy results from different thermal expansion coefficient between silicon and aluminum.
In this research, we produced a continuous and p-type silicon film by aluminum induced crystallization (AIC) process to work as BSF or emitter. The advantages that fabricating p-type silicon film by AIC is the low temperature process. However, the carrier concentration obtained by AIC is only 3x1018cm-3 which is lower than other methods. It must surpass 1019cm-3, or the efficiency would decrease because of reduction of carrier lifetime caused by low carrier concentration.
We co-sputter with boron into aluminum film at first, and then boron atoms dissolve into silicon and provide holes after AIC process completes. It results in increase of carrier concentration while the annealing temperature keeps the same at 400oC. We expect the technology that produces high carrier concentration silicon film at low temperature can be used as BSF and emitter, and then gets better performance compared to conventional AIC process.

References
[1] K. Zweig and M. A. Green, Progr. Photovolt. Vol.8, 1, 2000.
[2] S. H. Kim, C. MacCracken, and J. Edmonds, Progr. Photovolt. Vol.8, 3, 2000.
[3] IMEC, Solar Cells Technology Group, Advances in OptoElectronics, , 2007
[4]A.Rohati, “Road to Cost –Effective Crystalline Silicon Photovoltaics” Proceedings of the 3rd World Conference on Photovoltaics Energy Conversion, Osaka, Japan, 2003
[5] Honsberg & Bowden, www.pveducation.org/pvcdrom, National Science Foundation
[6] Mohamed M.Hilali, “Understanding and Development of Manufacturable Screen-Printed Contacts On High Sheet-Resistance Emitter For Low-Cost Silicon Solar Cells”, Georgia Institute of Technology, 2005
[7] Vichai Meemongkolkiat, “Development of High Efficiency Monocrystalline Si Solar Cells Through Improved Optical and Electrical Confinement”, Georgia Institute of Technology, 2008
[8] P. Lijlgen, C. Leguijt, J.A. Eikelboom, R.A. Steeman and W.C. Sinke, P.F.A. Alkemade and E. Algra,” Aluminum Back-Surface Field Doping Profiles with Surface Recombination Velocities Below 200 cm/s” in 23rd IEEE PVSC, pp. 246-242, 1993
[9] Shreesh Narasimha, Ajeet Rohatgi, Fellow, IEEE, and A. W. Weeber, “An Optimized Rapid Aluminum Back Surface Field Technique for Silicon Solar Cells”, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 46, NO. 7, 1999
[10] J. Nijs, E. Demesmaeker, J. Szlufcik, J. Poortmans, L. Frisson, K. De Clercq, M. Ghannam, R. Mertens, and R. Van Overstraeten, “Latest efficiency results with the screen printing technology and comparison with the buried contact structure,” in 1st World Conf. Photovoltaic Energy Conversion, pp. 1242–1249, 1994
[11] Schneider, A. “Al BSF for Thin Screen-printed Multicrystalline Si Solar Cells”, 17th EPVSC in Munich, Germany, 2001
[12] A. Schneider, C. Gerhards, P. Fath, E. Bucher, R.J.S. Young, J.A. Raby,A.F. Carroll, “Bow Reducing Factors For Thin Screen-printed MC-Sl
Solar Cells with AL BSF” , in 29th IEEE PVSC pp.336-339, 2002
[13] H.H.C de Moor, A.W.Webber, J.Hoornstra, and W.C Sinke, “Fine-line Screen Printing For Silicon Solar Cells,” 6th Workshop on Crystalline Silicon Solar Cell Materials and Processes, Snowmass, Colorado, pp.154-170, 1996
[14] Ballif, C.; Huljic, D.M.; Willeke, G.; Hessler-Wyser, A., “Silver thick-film contacts on highly doped n-type silicon emitters: Structural and electronic properties of the interface”, Applied Physics Letters 82, Nr.12, S.1878-1880, 2003
[15] Oliver Nast, Stephan Brehme, Stephen Pritchard, Armin G. Aberle, Stuart R. Wenham, “Aluminium-induced crystallisation of siliconon glass for thin-film solar cells”, Solar Energy Materials & Solar Cells 65, 385-392, 2001
[16] G. Maini and G. Ottaviani, “Large area growth of <100>Si through Al film by solid epitaxy”, Applied Physics Letters, Vol. 31, No.2, 1977
[17] S-Y. Tsaur, G. W. Turner, and John C. C. Fan, “Efficient Si solar cells by low-temperature solid-phase epitaxy”, Appl. Phys. Lett. 39(9), 1981
[18] D.S.Kim, A.Das, K. Nakayashiki, B.Rounsaville, V.Meemongkolkat, A.Rohatgi, “SILICON SOLAR CELLS WITH BORON BACK SURFACE FIELD FORMED BY USING BORIC ACID”, Georgia Institute of Technology, School of Electrical and Computer Engineering
[19] M. OEHME and E. KASPER,”Abrupt Boron Profiles by Silicon-MBE”, International Journal of Modern Physics B5 Vol. 16, Nos. 28 & 29 4285-4288, 2002
[20] Ji Youn Lee, S Soo Hong Lee, “Boron Back Surface Field Using Spin-On Dopants by Rapid Thermal Processing”, Journal of the Korean Physical Society, Vol. 44, No. 6, pp. 1581_1586, 2004
[21] Photon International, ITRI/MCL, Taiwan (2010/05)
[22] PVNET European Roadmap for PV R&D, ITRI/IEK, Taiwan (2009/08)
[23] R. B. Bergmann, G. Oswald, M. Albrecht, and V. Gross, “Solid-phase
crystallized Si films on glass substrates for thin-film solar cells,” Sol.
Energy Mater. Sol. Cells, vol. 46, p. 147, 1997
[24] T. Matsuyama, T. Baba, T. Tsuyoshi, S. Tsuda, and S. Nakano, “Polycrystalline Si thin-film solar cell prepared by solid phase crystallization (SPC) method” Sol. En. Mat. and Sol. Cells 34, 285, 1994
[25] O.Nast, “The aluminum-induced layer exchange forming polycrystalline silicon on glass for thin-film solar cells”, 2000
[26] S. R. Herd, P. Chaudhari, and M. H. Brodsky,” Metal Contact Induced Crystallization in Films of Amorphous Silicon and Germanium”, J. Non-Crystall. Solids _7, 309, 1972
[27] L. Hultman, A. Robertsson, H. T. G. Hentzell, I. Engstrom, and P. A. Psaras, “ Crystallization of Amorphous Silicon During Thin-Film Gold Reaction”, J. Appl. Phys. 62, 3647,1987
[28] M. S. Ashtikar and G. L. Sharma, “Silicide Mediated Low Temperature Crystallization of Hydrogenated Amorphous Silicon in Contact with Aluminum”, J. Appl. Phys. 78, 913,1995
[29] C. Hayzelden and J. L. Batstone,” Silicide Formation and Silicide Mediated Crystallization of Nickel-Implanted Amorphous Silicon Thin Film”, J. Appl. Phys. 73, 8279,1993
[30] Z. Jin, G. A. Bhat, M. Yeung, H. S. Kwok, and M. Wong,” Nickel Induced Crystallization of Amorphous Silicon Thin Films”, J. Appl. Phys. 84, 194, 1998
[31] B. Bian, J. Yie, B. Li, and Z. Wu,” Fractal Formation in a-Si:H/Ag/a-Si:H Films after Annealing”, J. Appl. Phys. 73, 7402,1993
[32] G. Majni and G. Ottaviani, ”Large-area Uniform Growth of <100> Si through Al Films by Solid Epitaxy” Appl. Phys. Lett. 31, 125, 1977
[33] B. Y. Tsaur, G. W. Turner, and J. C. C. Fan, “Efficient Si Solar Cells by low-Temperature Solid-Phase Epitaxy ”Appl. Phys. Lett. 39, 749, 1981
[34] L. M. Koschier, S. R. Wenham, M. Gross, T. Puzzer, and A. B. Sproul, “Low
temperature junction and back surface field formation for photovoltaic devices,”
2nd world conference and exhibition on photovoltaic energy conversion , Vienna, p.1539, 1998
[35] A.S Bhuiyan, A. Martinez and D. Esteve, “A new Richardson plot for non-ideal Schottky diodes”, Thin Solid Films, p.93-100, 1988
[36] William F. Armitage, Jr., Everett E.Chrisman,” Fabrication of Photovoltaic Devices by Solid Phase Epitaxy”, Aug.28, (1979)
[37] European Journal of Scientific Research, ISSN 1450-216X Vol.24 No.3, pp.365-372, 2008
[38] D. Munoz et al., “Low temperature back-surface-field contacts deposited by hot-wire CVD for heterojunction solar cells”, Thin Solid Films, Volume 516, Issue 20, Pages 6782-6785 , 2008