The Study of Atomic Layer Deposition Aluminum Oxide Passivation Effect on Crystalline Silicon Wafer

• Main Authors: Cheng-Chi Liu, 劉正淇
• Other Authors: Chung-Yuan Kung
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/9d535b

碩士 === 國立中興大學 === 光電工程研究所 === 99 === 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.