X-ray photoelectron spectroscopy has been used to study the composition of 100-Å thermally grown SiO2 films that have been thermally nitrided in ammonia. The SiOxNy/Si interface was studied both by chemical depth profiling of the oxynitride and by removal of the Si substrate with XeF2. It is found that N is distributed throughout the film, but with the concentration higher at the surface and in a region centered 25 Å from the film/substrate interface. The interface region itself is found to be oxygen-rich relative to the rest of the film. Possible models which can explain these results are discussed.

Thick oxide films (≈220 nm) have been nitrided heavily in ammonia. Dispersion analysis was performed on infrared transmission spectra of oxide, nitrided oxide, and CVD nitride films. The following conclusions may be drawn from the spectra: nitrided oxide is not the same material as CVD silicon nitride; nitridation results in significant loss of Si‐O asymmetric stretch intensity; and nitridation leads to the appearance of a spectral peak for planar triply bonded N‐Si asymmetric stretch analogous to that in trisilylamine. About 43% of the oxygen was replaced by nitrogen.

Chemical analysis has been made of 361-Å thermal oxide films nitrided in ammonia and also subsequently reoxidized in oxygen at 1000 °C, using techniques of ellipsometry and infrared spectrometry. The nitrided film is shown to have a three-layer structure consisting of 22 Å of 48% nitrogen, 334 Å of 17% nitrogen, and 7.4 Å of 100% nitrogen, where the fractions refer to % N/(N+O). After oxidation, the interface layer was unchanged and the surface merged into the bulk, the nitrogen content of which was reduced to 11%. The void content has also been determined.