Surface passivation of c-Si wafers using a-Si:H layers prepared in large-area radio frequency plasma enhanced chemical vapor deposition system

• Main Authors: Yi-Liang Liao, 廖苡良
• Other Authors: Lu-Sheng Hong
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/79gs73

碩士 === 國立臺灣科技大學 === 化學工程系 === 105 === Hydrogenated amorphous Si (a-Si:H) thin films were deposited on single crystal Si (c-Si) wafers to form a-Si:H/c-Si heterojuction structure in large-area(20×20 cm2) radio-frequency plasma-enhanced chemical vapor deposition (large-area RF-PECVD) system. Emphasis was placed upon exploring the characteristics of a-Si:H film prepared in large-area RF-PECVD system and finding the optimized condition to obtain the high quality film which has less defect and dense structure. We expect to promote minority carrier lifetime of c-Si with these high quality films. The result of experiment, when the discharge distance is 3 cm in large-area RF-PECVD system, it was found that film has a roughness layer thickness of 1.01 nm and a microstructure parameter of 0.165 at a minimum 1.59 mW / cm2 of plasma power density. When we deposited 30 nm a-Si:H on double side to passivate the polished silicon wafer, the as-deposited sample showes a minority carrier lifetime of 1170 µs. Therefore, we got more compact films at very low power density in large-area PECVD system. In addition, when the hydrogen dilution ratio is 3, we observed that the amorphous/epitaxy transition by employing RHEED technique. The a-Si:H/c-Si heterojuction prepared under this condition showes a very high minority carrier lifetime of 1430 µs even for the as-deposited state. A further heat treatment promoted minority carrier lifetime only a little bit to 1630 µs, corresponding an implied Voc of 718 mV. The microstruture parameter down from 0.15 to 0.034, it shows that produce less microvoid after annealing, and have the best passivation performance.