Effects of dilution ratio and seed layer on the crystallinity of microcrystalline silicon thin films deposited by hot-wire chemical vapor deposition

Abstract

We deposited microcrystalline silicon (μc-Si) by hot-wire chemical vapor deposition (HWCVD) at different thickness and dilution ratio, with and without seed layer. As the dilution ratio increased, we observed an increase in the amount of microcrystalline phase in the film, a change in the structure of the grains and a loss of the (220) preferential orientation. The films deposited over a seed layer had a larger fraction of crystalline phase than films deposited with the same parameters but without a seed layer. For high dilution ratios ( R=100), most of the film grows epitaxially at the interface with the Si substrate, but a microcrystalline film slowly replaces the single-crystal phase. For low dilution ratios ( R=14), the film starts growing mostly amorphously, but the amount of crystalline phase increases with thickness.