Effect of near-interfacial nitrogen on the oxidation behavior of ultrathin silicon oxynitrides

Medium energy ion scattering has been used to study the role of nitrogen in the thermal oxidation kinetics of ultrathin silicon oxynitrides. Oxynitride films with different amounts of nitrogen near the SiOxNy/Si interface and pure (control) SiO2/Si films were reoxidized in dry O-18(2) under equivalent conditions. The spatial distribution of O-18 incorporated into the films was analyzed by high-resolution depth profiling methods. Analogous to the pure SiO2 case, we observed two distinct regions where oxygen incorporation into the oxynitride films occurs: at/near the interface and near the outer oxide surface. The (near) interface oxide growth reaction is found to be significantly retarded by the presence of near-interfacial nitrogen (with a higher degree of the retardation for higher concentrations of nitrogen). The presence of nitrogen near the interface does not affect the surface exchange reaction. (C) 1997 American Institute of Physics.