Characterization of High-Rate Deposited Microcrystalline Si Films Prepared using Atmospheric-Pressure Very High-Frequency Plasma

Abstract

Using stable plasma excited at atmospheric pressure by supplying 150-MHz very high-frequency (VHF) power, low-temperature and high-rate deposition of hydrogenated microcrystalline silicon (mc-Si:H) films is investigated. H2/SiH4 ratio and substrate temperature (Tsub) are varied as parameters under supplying an optimized VHF power density of 24 W/cm2. It is observed that increasing H2/SiH4 ratio leads to the improvement of both deposition rate and crystalline volume fraction (ICRS). It is worth to note that ICRS of approximately 72% is obtained even at H2/SiH4 = 0. The Tsub dependence of Raman crystallinity of the mc-Si:H films indicates that a highly crystallized mc-Si:H film grows even when Tsub is reduced down to 90 ºC. One of the contributing factors to this low-temperature deposition of mc-Si:H is the moderate heating effect of the growing film surface by the atmospheric-pressure VHF plasma while suppressing ion damage of the surface.