Hot-wire CVD-grown microcrystalline silicon films with and without initial growing layer modification by transformer-coupled plasma

Abstract

Microcrystalline Si (μc-Si) films have been deposited using five W wire filaments, 0.5 mm in diameter, for hot-wire chemical vapor deposition (HWCVD). We compared the HWCVD-grown films with and without modification of the initial growing layer by using a transformer-coupled plasma system. The W-wire filament temperature was maintained below 1600°C to avoid metal contamination by thermal evaporation of the filament. Deposition conditions were varied, including the H2 dilution ratio, with and without a seed-layer plasma treatment. From Raman analysis, we observed that the film crystallinity was strongly influenced by the H2 dilution ratio and weakly depended on the distance between the wire and the substrate. We were able to achieve a crystalline volume fraction of approximately 79% with a H2/SiH4 ratio of 80, a wire temperature of 1514°C, a substrate distance of 4 cm, and a chamber pressure of 38 mtorr. We investigated the influence of a plasma treatment during the initial stage of Si film formation for property variations in the HWCVD-grown μc-Si film. This article also deals with the influence of the H2 dilution ratio in crystallinity modification.