ELECTRON-BEAM-INDUCED NITROGEN MIGRATION THROUGH A NITRIDED SILICON DIOXIDE THIN-FILM

Auger sputter depth profiles of very thin (15 nm) plasma-nitrided SiO2 films thermally grown on silicon wafers have been measured before and after bombardment with energetic electrons (1, 3, or 5 keV). Electron irradiation of the film induced nitrogen depletion at the vacuum/ die lectric interface and a nitrogen pile-up at the dielectric/silicon int erface. Our results indicate that this phenomenon is maximum for the l owest primary electron energy. This behavior could be understood on th e basis of an electron-stimulated Si-N bond decomposition and the crea tion of positive nitrogen ions. The released nitrogen ions could eithe r escape into the vacuum or migrate through the dielectric layer and p ile up at the dielectric/silicon interface due to the existence inside the layer of a non-uniform electric field, in agreement with recent t heoretical predictions.