Electron-beam-induced nitrogen migration through a nitrided silicon dioxide thin film

Abstract

Auger sputter depth profiles of very thin (15 nm) plasma-nitrided SiO 2 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/dielectric interface and a nitrogen pile-up at the dielectric/silicon interface. Our results indicate that this phenomenon is maximum for the lowest primary electron energy. This behavior could be understood on the basis of an electron-stimulated Si-N bond decomposition and the creation of positive nitrogen ions. The released nitrogen ions could either escape into the vacuum or migrate through the dielectric layer and pile up at the dielectric/silicon interface due to the existence inside the layer of a non-uniform electric field, in agreement with recent theoretical predictions.