An X-ray photoelectron spectroscopy study of ultra-thin oxynitride films

Oxynitrides prepared by nitridation of 2 to 5 nm SiO2 films on silicon, were studied by X-ray photoelectron spectroscopy at two analyser exit angles. An iterative procedure was applied to obtain simultaneously the average nitrogen content and the thickness of the nitrided layer, mutually dependent via the electron transport properties of the layer matrix. Inelastic mean free paths and elastic corrections thereof were determined in accordance with ISO18118:2004(E), whereas a set of empirical relative sensitivity factors was used. The results reveal a significant increase of the 2 nm film thickness upon nitrogen incorporation of the order of 50 at.%, whereas the 5 nm films retain their thickness upon comparable extent of nitridation.