The effect of Ar+ sputtering on the x-ray photoelectron spectra of plasma-deposited silicon nitride films

The effects of argon-ion sputtering and atmospheric exposure on the composition and structure of plasma-deposited (PD) silicon nitride films were studied using x-ray photoelectron spectroscopy. PD silicon nitride samples were transferred directly from the plasma deposition chamber into the analysis chamber without ambient exposure. Samples exposed to ambient oxidized, with an oxidation rate that depended upon deposition temperature. Ion energies of 500–4000 eV were used to sputter sample surfaces. Preferential sputtering was observed at all energies, with the lower energies creating less compositional and structural modification. Films deposited at lower temperatures exhibited pronounced preferential sputtering of nitrogen, particularly NHx species. Ion milling was found to be unacceptable as a means of surface cleaning PD silicon nitride since even qualitative N:Si composition trends were modified by sputtering.