Effects of Addition of SiF4 During Growth of Nanocrystalline Silicon Films Deposited at 100°C by Plasma-Enhanced Chemical Vapor Deposition

Abstract

Structural properties of nanocrystalline silicon (nc-Si) films, deposited at 100°C using SiF4/SiH4/H2 by plasma-enhanced chemical vapor deposition, were investigated by changing the SiF4 flow rate, [SiF4]. At a certain low [SiF4] value (=[SiF4]S), both the crystallinity and the grain size had minimum values. The Raman peak shifts corresponded well with a change in stress, and films with [SiF4]S were suggested to be free from random stress in the local Si–Si networks. The photoluminescence spectra had the highest intensity and the highest peak energy at [SiF4]S. It was proposed that nc-Si films with high [SiF4] have microvoid-like grain boundaries with high densities of Si–F and SiH2 bonds, exhibiting an increase in crystallinity and susceptibility to O contamination after deposition. These results were interpreted in terms of the change in the etch rates by H and F radicals, depending on deposition temperature.