X-ray photoelectron spectroscopy of thermal thin Ta2O5 films on Si

X-ray photoelectron spectra (XPS) have been recorded for thermally grown thin tantalum pentoxide films on Si. The peak decomposition technique was employed to identify the composition and the chemical states throughout the film. It is established that stoichiometric Ta2O5 detected at the surface of the layer is reduced to tantalum suboxides in its depth which amount increases in the depth of Ta2O5 film. The results show that even the films obtained at low oxidation temperature (673 K) have a two-layer structure (i.e. silicon dioxide at the interface and tantalum oxide above it) suggesting oxidation of silicon substrate in addition to oxidation of the tantalum film on Si. The interface between Si and this ultra thin SiO2 is not abrupt and the coexistence of Si–O and Ta–O bonding states in close proximity to the interface is found. The thicknesses of both, the tantalum oxide and the SiO2, as well as the width of the Si–SiO2 interface transition region are evaluated.