The effect of hydrogen dilution on the aminosilane plasma regime used to deposit nitrogen-rich amorphous silicon nitride

Abstract

The first hydrogen dilution study of ammonia/silane plasmas tuned to an aminosilane plasma regime is reported. The use of formal statistical experimental design techniques have enabled us to determine the effects that hydrogen dilution level, rf power density and substrate growth temperature have on various film properties. Hydrogen dilution of the ammonia/silane plasma reduced the amino (NH 2) content of the deposited nitride films while also driving the intrinsic film stress to compressive values. Increasing the substrate temperature also reduced the amino concentration, but drove the film stress tensile. It was therefore possible to control the film stress and produce nitride films that contained only NH and SiN bonds (with no detectable NH 2 or SiH bonds) by choosing a suitable combination of H 2 dilution level and growth temperature. Exodiffusion experiments on such ‘bond optimised’ films revealed only one hydrogen evolution peak at temperatures in excess of 900°C, with no ammonia exodiffusion detected.