Development of Ultra-Clean Plasma Deposition Process

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DEVELOPMENT OF ULTRA-CLEAN PLASMA DEPOSITION PROCESS Toshihiro KAMEI and Akihisa MATSUDA Thin Film Silicon Solar Cells Superlab, ElectrotechnicalLaboratory, 1-1-4 Umezono Tsukuba 3058568, Japan ABSTRACT We have developed a new type of ultra-high vacuum plasma-enhanced chemical vapor deposition (UHV/PECVD) system. According to high sensitivity secondary ion mass spectrometry, device quality hydrogenated amorphous silicon (a-Si:H) films deposited at 250'C at a deposition rate of I A/s contains 1015 cm-3 of 0, 1015 cm-3 of C, and 1014 cm- 3 of N impurities, while low defect hydrogenated microcrystalline silicon (itc-Si:H) films deposited at 200'C at a very low rate of 0.1 A/s include 1016 cmn3 of 0, 101 cm- of C and 1016 cm 3 of N. These are the lowest concentrations of atmospheric contaminants for these kinds of materials observed so far. The essential features of the present UHV/PECVD system are an extremely low outgassing rate of 8x10-9 Torr-,/s, extremely low partial pressure of contaminant gas species