Oxidation of PECVD SiNx thin films

The effect of heat treatment on the chemical structure of low-temperature plasma-enhanced chemical vapor deposited silicon nitride thin films is presented. The deposited films were heat treated to temperatures up to 1373 K in air. The chemical composition of the films was analysed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was found that the as-deposited films contained Si, N and H in varying proportions, depending on deposition and post-deposition treatment conditions. Upon heating to elevated temperatures, N lost from the films in two stages by different mechanisms. The decrease in N concentration at relatively low heat treatment temperatures (<673 K) is due to loss of N–H bonded N, whereas, the decrease at higher temperatures is due to the oxidation conversion of the SiNx matrix. Heating to high temperatures also resulted in the removal of H.