XAFS characterization of buried SixNyOz samples

The microstructure and the near edge X-ray absorption fine structure (NEXAFS) signature of defect states in buried silicon oxynitrides is studied, as a function of the film composition, using extended X-ray absorption fine structure (EXAFS) and NEXAFS measurements at the N- and O-K edges. The films were fabricated by ion implantation of N2O+ into Si substrates. The NEXAFS spectra are characterized by two resonance lines, which appear 1.2 eV below and 0.5 eV above the N-K absorption edge, respectively. Based on the NEXAFS analysis results we propose that the first resonance line is attributed to the N pair defect while the second one, which is characteristic of N-rich samples, to N-dangling bonds. The EXAFS measurements reveal that the Si-O distance is constant and independent of the N concentration while the Si-N distance decreases with increasing oxygen content. In addition to that, regions of partially reacted Si (designated a-Si:N) are detected in samples were the (N/O) ratio exceeds the value of 2. Contrary to that, the mechanism of formation of the a-Si:N islands is inhibited as the oxygen concentration increases and the corresponding (N/O) ratio is less than 2. (C) 2002 Published by Elsevier Science B.V.