Study of oxide film with the hard X-ray photoelectron spectroscopy

We report the applications of a hard X-ray photoelectron spectroscopy to the characterization of SiO₂/Si(001) systems. Large escape depth of high-energy photoelectron enables us to probe buried layers and their interfaces in multilayer structures. Estimation of SiO₂ overlayer thicknesses up to 25 nm by angle resolved XPS was possible in SiO₂/Si(001) samples. Determination of the thickness profile of a wedged shape SiO₂ buried layer was successfully done in Ir (8 nm)/HfO₂ (2.2 nm)/thickness graded-SiO₂(0-10 nm)/Si(100). The Si 1s core level showed a SiO₂ thickness dependent shift, which was ascribed to fixed charge at the SiO₂-Si interface. Energy distribution of interface states at ultrathin thermal oxide/Si(100) interfaces were determined by Si 1s core level shift by applying gate bias in metal-oxide-semiconductor (MOS) structure with 5 nm Au gate electrodes. (author)