Photoelectron spectroscopy studies of SiO2/Si interfaces

We describe state-of-the-art photoelectron spectroscopy studies of SiO2/Si interfaces that play fundamental roles in metal-oxide-semiconductor (MOS) field-effect transistors. We show comprehensive photoelectron spectra of SiO2/Si interfaces, which were taken from SiO2/Si samples of extremlye high-quality by the high-resolution photoelectron spectroscopy technique with either synchrotron or laboratory X-ray sources. The spectra discussed here include the Si 2p, the Si 1s, the O 2s, and N 1s core-level spectra, and the valence-band spectra. We perform quantitative analysis using selected values of the photoionization cross-section and the electron escape depth, which is governed by both inelastic scattering and elastic scattering in SiO2. On the other hand, we analyze peak energies by considering peak energy shifts that are due to several factors. Atomic structures are discussed in terms of intermediate oxidation states at SiO2/Si(1 0 0) interfaces and strained Si-O-Si bonds near the interfaces, while electronic structures are discussed in terms of valence-band offset at the interfaces and dielectric constants near the interfaces. Applications of photoelectron spectroscopy study to advanced oxide formation are also shown in terms of depth profiling of oxynitride films and interface structures of low-temperature oxide.