High Quality Hydrogenated Amorphous Silicon Thin Films with Enhanced Growth Rates for Surface Passivation in an Al2O3 Based ICP Reactor

Abstract

Plasma processing of materials in low frequency inductively coupled plasma (LF-ICP) reactors has limitations involving the presence of contaminant species found in the discharge. It has been shown in previous work through optical emission spectroscopy that a main source of contaminants were oxygen related species which were not part of the feedstock recipe. In this work, amorphous silicon thin films were grown on silicon substrates with a LF-ICP reactor. The dielectric top lid plays an important role in the reduction of oxygen species detected in the thin films. It was postulated that the source of the contaminants came from sputtering of the lids. The replacement of the conventional quartz (SiO2) lid with that of alumina (Al2O3) reduced the oxygen species present in the resulting discharge, which is often a source of contamination in the resulting thin films, impinging the passivation grade of the resulting films. The modified reactor configuration also resulted in increased hydrogenation and deposition rate of the thin films. The results show that alumina lids serve as a promising alternative in replacing the conventional quartz lids in LF-ICP reactors for materials processing, resulting in efficient power transfer to the plasma and films which are rid of contaminant species.