Electronic structure and bonding in silicon oxynitride films: An XPS study

Silicon oxynitride films on sapphire as well as silicon made by RF sputtering of silicon in a reactive atmosphere of O 2 and N 2 have been examined by X-ray photoelectron spectroscopy. Bremsstrahlung X-rays from the Mg anode have sufficient intensity to initiate the Si(KL 2.3L 2.3) Auger line, whose chemical line shift is about three times that of the Si(2p) level. There is a continuous shift in the Si(KLL) line as the oxygen in SiO 2 is replaced by nitrogen. From the peak shape and shifts of Si(KLL), N(KLL), O(KLL), Si(2p) and the valence band, we show that oxygen and nitrogen are mixed locally on an atomic scale. The thin films do not consist of regions of SiO 2 and Si 3N 4. This mixed condition persists even up to 1000°C.