X-ray photoelectron spectroscopy study of the chemical structure of thermally nitrided SiO2

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.