ON THE FORMATION OF SILICON OXYNITRIDE BY ION-IMPLANTATION IN FUSED-SILICA

The formation of silicon oxynitrides and nitrogen gaseous compounds as a consequence of implantation of nitrogen ions in silica glasses was investigated by XPS analysis. The presence of gaseous compounds is supported by the analysis of the effect of a double implantation: a nitrogen implantation followed by an argon irradiation. Moreover SEM analysis shows, for doses higher than 6 × 1017 N cm-2, a surface morphology characterized by blisters, which can be also ascribed to NO or N2 molecules. These structures are absent in the case of neon implantations. The distribution of nitrogen as a function of the implantation dose was measured by SIMS. With a dose >5 × 1016 cm-2, the nitrogen distribution showed a flat profile limiting the maximum attainable nitrogen concentration and, consequently, the stoichiometry of the SiOxNy compounds. An increase of the nitrogen concentration was obtained for nitrogen implantations in 29Si-preimplanted silica glasses. The nitrogen profile followed the distribution of the preimplanted silicon. © 1990.