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標題: 原子層沉積氧化鋁薄膜技術對單晶矽基板鈍化之研究
The Study of Atomic Layer Deposition Aluminum Oxide Passivation Effect on Crystalline Silicon Wafer
作者: Liu, Cheng-Chi
關鍵字: Al2O3;氧化鋁;passivation;ALD;鈍化;原子層沉積
出版社: 光電工程研究所
引用: [1] Kazmerski L, D. Gwinnwe, and A. Hicks, National Renewable Energy Laboratory NREL,(2009) [2] Dr. Richard Swanson National Renewable Energy Laboratory NREL (2008), and SVC (2009) [3] Enrichetta Susi.” Recombination Mechanisms in Crystalline Silicon: Bulk and Surface Contributions”, International Journal of Photoenergy. 1 (1999) [4] E. Yablonovitch and D. L. Allara,”Unusnally Low Surface-Recombination Velocity on Silicon and Germanium Surfaces”, Physical Review Letters. Vol. 57 (1986) [5] T.S. Horanyia and T. Pavelkaa,” In Situ Bulk Lifetime Measurement on Silicon with a Chemically Passivated Surface”, Applied Surface Science, 63 (1993) [6] W. Arndt, K. Graff, P. Heim, Proceedings of the ALTECH ‘95, Den Haag, Netherlands (1995) [7] B. Hoex and J. Schmidt,” Silicon surface passivation by atomic layer deposited Al2O3”, Journal of Applied Physics, 104 (2008) [8] W. Fiissel and M. Schmidt,” Defects at the Si/SiO2 interface: their nature and behaviour in technological processes and stress”, Nuclear Instruments and Methods in Physics Research , 177 183(1996) [9] J. Schmidt and A. Merkle, ” Surface Passivation of High-efficiency Silicon Solar Cells by Atomic-layer-deposited Al2O3”, Prog. Photovolt: Res. Appl. 16 (2008) [10] Jan Schmidt and Agnes Merkle, ” Atomic-Layer-Deposited Aluminum Oxide for the Surface Passivation of High-Efficiency Silicon Solar Cells”, Photovoltaic Specialists Conference, (2008) [11] D. Macvonald and A. Cuevas, ” The Trade-Off Between Phosphorus Gettering and Thermal Degradation in Multicrystalline Silicon”,16th Photovoltaic Solar Energy Conference (2000) [12] M. J. Chen and Y. T. Shih, “ Enhancement in the Efficiency of Light Emission from Silicon by a Thin Al2O3 Surface-Passivating Layer Grown by Atomic Layer Deposition at Low Temperature”, Journal of Applied Physics, 101 (2007) [13] V. Yelundur and A. Rohatgi,” PECVD SiNx Induced Hydrogen Passivation in String Ribbon Silicon”, Photovoltaic Specialists Conference (2000). [14] Stefan Dauwe and Lutz Mittelstadt,” Experimental Evidence of Parasitic Shunting in Silicon Nitride Rear Surface Passivated Solar Cells”, Prog. Photovolt, 10 (2002) [15] E. D. Tober and J. Kanicki,” Thermal Annealing of Light-Induced Metastable Defects in Hydrogenated Amorphous Silicon Nitride ”, Phys. Lett. 59 (1991) [16] T. Lauinger and J. Schmidt,” Record Low Surface Recombination Velocities on 1 Ωcm p-silicon Using Remote Plasma Silicon Nitride Passivation”, Appl. Phys. 68 (1996) [17] Myoung Yone Seo and Edward Namkyu Cho,” Characterization of Al2O3 Films grown by Electron Beam Evaporator on Si Substrates ”, IEEE(2010) [18] B. Hoex and J. Schmidt, “Excellent Passivation of Highly Doped p-type Si Surfaces by the Negative-Charge-Dielectric Al2O3”, Applied Physics 91 (2007) [19] J. Benick and A. Richter,” Effect of a Post-Deposition Anneal on Al2O3/Si Interface Properties ”, Photovoltaic Specialists Conference (2010) [20] J. Schmidt and A. Merkle,” Progress in the Surface Passivation of Silicon Solar Cells”, 23rd European Photovoltaic Solar Energy Conference, (2008) [21] G. Dingemans and P. Engelhart,” Firing Stability of Atomic Layer Deposited Al2O3 for C-Si Surface Passivation”, Photovoltaic Specialists Conference , (2009) [22] Jaran SRITHARATHIKHUN and Chandan BANERJEE,” Surface Passivation of Crystalline and Polycrystalline Silicon Using Hydrogenated Amorphous Silicon Oxide Film”, The Japan Society of Applied Physics 46 (2007) [23] G. Dingemans and W. M. M. Kessels,” Recent Progress in the Development and Understanding of Silicon Surface Passivation by Aluminum Oxide Photovoltaics”,25th Solar Energy Conference (2010) [24] J. Schmidt and F. Werner,” Surface Passivation of Silicon Solar Cells Using Industrially Relevant Al2O3 Deposition Techniques”, Photovoltaic Solar Energy Conference ( 2010) [25] R.W. Miles and K.M. Hynes,” Photovoltaic Solar Cells: an Overview of state-of-the-art Cell Development and Environmental Issues” Progress in Crystal Growth and Characterization of Materials 51 (2005) [26] R. Hezel and K. Jaeger,” Low-Temperature Surface Passivation of Silicon for Solar Cells”, The Electrochemical Society. 136 (1989) [27] G. Agostinelli and A. Delabie,” Very Low Surface Recombination Velocities on p-Type Silicon Wafers Passivated with a Dielectric with Fixed Negative Charge”, Solar Energy Materials & Solar Cells (2006) [28] B. Hoex and S. B. S. Heil,” Ultralow Surface Recombination of C-Si Substrates Passivated by Plasma-assisted Atomic Layer Deposited Al2O3 ”, Applied Physics Letters 89 (2006) [29] J. Benick and B. Hoex,” High efficiency n-type Si solar cells on Al2O3-passivated boron emitters ”, Applied Physics Letters 92 (2008) [30] J. Schmidt and F. Werner,” Surface Passivation of Silicon Solar Cells Using Industrially Relevant Al2O3 Deposition Techniques”, 25th European Photovoltaic Solar Energy Conference ( 2010) [31] 半導體材料測試與分析,楊德仁著,科學出版社,2010 [32] C.H. Shin and D.W. Kwak,” Nitrogen Effect on Negative Fixed Charges of Al2O3 Passivation Film In Crystalline Si Solar Cells”, Photovoltaic Specialists Conference (2010) [33] G. Dingemans and R. Seguin,” Silicon Surface Passivation by Ultrathin Al2O3 Films Synthesized by Thermal and Plasma Atomic Layer Deposition”, phys stat sol (2009) [34] G. Dingemans and P. Engelhart,” Comparison between Aluminum Oxide Surface Passivation Films Deposited with Thermal ALD, Plasma ALD and PECVD ”, Photovoltaic Specialists Conference (2010) [35] N. M. Terlinden and G. Dingemans,” Role of Field-Effect on C-Si Surface Passivation by Ultrathin 2–20 nm Atomic Layer Deposited Al2O3”, Applied Physics Letters 96 (2010) [36] J. J. H. Gielis and B. Hoex,” Negative Charge and Charging Dynamics In Al2O3 Films on Si Characterized by Second-Harmonic Generation”, Journal of Applied Physics 104 (2008) [37] B. Hoex and J. J. H. Gielis,” On the C-Si Surface Passivation Mechanism by the Negative-Charge dielectric Al2O3 ”, Journal of Applied Physics 104, (2008) [38] J. Irikawa and S. Miyajima,” Effects of Annealing and Atomic Hydrogen Treatment on Aluminum Oxide Passivation Layers for Crystalline Silicon Solar Cells ”, Japanese Journal of Applied Physics 50 (2011) [39] V. Verlaan and L. R. J. G. van den Elzen,” Composition and Bonding Structure of Plasma-assisted ALD Al2O3 Films”, Phys. Status Solidi C 7, (2010) [40] J. Buckley and B. De Salvo,” Reduction of Fixed Charges in Atomic Layer Deposited Al2O3 Dielectrics”, Microelectronic Engineering (2005) [41] Feng Zhang and Huili Zhu,” Al2O3/SiO2 Films Prepared by Electron-beam Evaporation as UV Antireflection Coatings on 4H-SiC ”, Applied Surface Science 254 (2008) [42] Jan Schmidt and Karsten Bothe,”Strusture and Ttransformation of the Metastable Boron- and Oxygen-related Defect Center in Crystalline Silicon”,Physical Review 69 (2004) [43] Yukie Yamamoto and Yukiham Uraoka,” Passivation Effect of Thin Deposited by Plasma Chemical Vapor Deposition for Thin Film c-Si Solar Cells ”, Photovoltaic Energy Conversion ( 2003)
Reduction of silicon substrate thickness can not only reduce material cost, but also improve the conversion efficiency of solar cells. Currently, silicon wafer thickness has been reduced to less than 200μm, however, thinner wafers require lower temperature process, and the surface defects thinner of wafer occupied the higher proportion of total defects, low-temperature surface passivation process is particularly interest in solar cell manufacture.

In this study, atomic layer deposition (ALD) of 30nm Al2O3 films at 200 ℃ in p-type substrate and annealed at 300 ℃ to 600 ℃ range in the environment of nitrogen and hydrogen gas mixture to observe the effect of passivation for Al2O3 layer. 500 ℃ annealing process is observed to have the best field-effect passivation effect, the wafer lifetime upgrade from 9 μs to 110 μs. Further, the stack double structure (a-Si1-xOx / Al2O3) has an even better passivation effect and improve lifetime to 191 μs. It is very suitable for p-type substrate.

The wafer were placed in the air for aging study, the lifetime is reduced by 70% in one week and lifetime recovered at 250 ℃ for just one minutes only. We also observed a high density blistering of 10um when passivated wafer annealed at 500 ℃ 30 minutes.

本實驗利用原子層磊晶方法(ALD,atomic layer deposition),在p-type基板上使用200℃的溫度成長30nm的Al2O3薄膜。實驗中使用300℃~600℃的退火溫度,觀察薄膜的鈍化效果,發現在氮氫混合氣體的環境下,經過500℃的退火過程,薄膜內部所產生的固定負電荷,能使晶片具有最佳的場效鈍化(field-effect passivation)效果,晶片的載子生命期從9 µs提升至110 µs ,且雙層疊加結構的鈍化層(a-Si1-xOx / Al2O3)具有更佳的鈍化效果,晶片載子生命期更能高達191 µs,非常適合做為p-type基板的鈍化層。
實驗中觀察到,將經過退火處理的晶片放置在空氣中一星期,晶片的鈍化效果下降30 %,利用250℃的加熱板進行加熱處理後,晶片的載子生命期恢復原狀。並且從實驗中也觀察到,經過500℃退火處理的晶片,利用光學顯微鏡觀察薄膜表面發現有孔洞產生,孔洞產生可能是加熱時薄膜內部的氫外擴散,或者是薄膜內鋁粒子因加熱氣散,使用不同條件的退火過程能有效降低孔洞的數目
其他識別: U0005-2407201111530100
Appears in Collections:光電工程研究所

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