CHARACTERIZATION BY X-RAY PHOTOELECTRON-SPECTROSCOPY OF THE CHEMICAL-STRUCTURE OF SEMIINSULATING POLYCRYSTALLINE SILICON THIN-FILMS

The x-ray photoelectron spectroscopy (XPS) technique has been used to investigate the composition of semi-insulating polycrystalline silicon (SIPOS) films having oxygen contents of 10 and 35 at. % prepared by l ow pressure chemical vapor deposition. XPS analysis has demonstrated t hat the him compositions can be qualitatively described by means of th e five Si-SixO4-x tetrahedra (with 0 less than or equal to x less than or equal to 4 and integer) predicted by the statistical random bondin g model (RBM). However, the quantitative analysis of the XPS spectra h as demonstrated that the concentrations of the various tetrahedra foun d in the SIPOS films are remarkably different from those predicted by a statistical approach, i.e., by assuming that each Si atom forms with equal probability bonds with either Si or O. We have also found that the composition of high temperature (up to 1000 degrees C) annealed fi lms further departs from that predicted by the RBM model; indeed, the anneal promotes the decomposition of partially oxidized Si-SixO4-x tet rahedra in Si-Si-4 tetrahedra (that form Si nanocrystals) and Si-O-4 t etrahedra (that enrich the oxygen content of the amorphous phase). (C) 1996 American Vacuum Society.