Silicon nitride films prepared by reactive plasma sputtering

Abstract

Silicon nitride films were prepared by reactive plasma sputtering in nitrogen at a pressure of 2×10 -4 Torr. The residual gas in the reactor during film sputtering was analysed. The chemical composition of the films was determined from infrared absorption spectra in the wavelength region 2.0–15.0 μm and by the elastic scattering of 3He particles. The best quality silicon nitride films were obtained in pure nitrogen at the minimum residual gas pressures. An absorption minimum at 11.0 μm in the infrared spectra, corresponding to the Si-N chemical bond in the Si 3N 4 molecule, was observed in our films, indicating that their composition was close to stoichiometric. With a residual hydrogen pressure above 10% or a residual oxygen pressure above 2% the generation of new chemical bonds Si-H, N-H and Si-O respectively was observed in the silicon nitride films.