Application of high-energy synchrotron-radiation X-ray photoelectron spectroscopy to the depth profile analysis of oxide layer on Si(100) surfaces

The analyzing depth of X-ray photoelectron spectroscopy (XPS) depends on the inelastic mean free path (IMFP) of a photoelectron. Since the IMFP of a photoelectron is a function of its kinetic energy, the analyzing depth of XPS changes with the excitation energy. We apply this relationship to the depth profile analysis of XPS measurements by using energy tunable synchrotron radiation (SR) X-rays. For this purpose, a 'High-energy SR-XPS' has been constructed and applied to the depth profile analysis of the two kinds of oxide layer on Si(100) surfaces. These are, 1)the thermally oxidized surface, which is well defined as a thin uniform film of SiO2, and 2)the O2+-ion implanted surface, which has a depth distribution of oxide. The thickness of the oxide layer and the depth profile of the O2+-ion implanted layer have been estimated by measuring the intensities of elemental Si to the intensity of SiO2, which are observed from the Si ls XPS spectra at the various photon energies. The results obtained suggest that the present system is feasible for the depth profile analysis of thin films. (author)