Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel configuration using SiH4/NH3/Ar gas mixtures undergo post deposition chemical transformations when deposited at low temperatures. These dielectric films are found to oxidise over time on exposure to the ambient humid environment, when deposited at substrate temperatures T-delta less than or equal to 250 degrees C. Time evolution of these oxidation processes have been monitored through FTIR spectroscopy and ellipsometric analyses and substantiated with the deconvolution of the infrared spectra to track down intermediate oxidation species. For T(delta)less than or equal to 200 degrees C, we observe a fast oxidation process involving gradual elimination of the Si-N, N-H and Si-H peaks and simultaneous growth of Si-O and Si-OH peaks. Above this temperature, the oxidation process has been found to slow down considerably and for T-delta greater than or equal to 300 degrees C stable films are obtained. Based on these data, we discuss the possible film composition dependent oxidation pathway that can lead to Si-N bond rupture and creation of Si-O and Si-OH bonds. (C) 1998 Elsevier Science S.A.
