XPS sputter depth profiling of the chemical states for SrTiO₃/Si interface by O₂⁺ ion beams

Because the chemical states of the elements in SrTiO₃ thin film on Si are reduced by argon ion beam bombardment, it was impossible to sputter depth profile the chemical states of SrTiO₃ thin film by argon ion beams. In this paper, it is reported that the undistorted chemical states of Ti and Si at the SrTiO₃/Si interface can be determined with oxygen ion beams at the appropriate 70° angle of incidence, with which either metallic Ti is not oxidized or Ti in SrTiO₃ is not reduced. Under the sputter depth profiling conditions, the chemical state of Ti at the SrTiO₃/Si interface could be successfully characterized and the effects of post‐annealing at high temperature on the chemical state of Ti were studied. A significant number of Ti atoms in the metallic state were observed at the SrTiO₃/Si interface without any post‐annealing but all of them were oxidized to the Ti⁴⁺ chemical state after 2 h post‐annealing at the temperatures above 600°C under oxygen flow. The dielectric properties of SrTiO₃ thin films on Si were well correlated to the oxidation state of Ti and the broadening of the interface SiO₂ layer induced by post‐annealing at high temperature.