Isotopic labeling studies of interactions of nitric oxide and nitrous oxide with ultrathin oxynitride layers on silicon

The interaction of nitric ~NO! and nitrous (N2O! oxide with ultrathin ~;1.5–3.5 nm! oxide and oxynitride films on silicon has been studied by performing high resolution depth profiling using medium energy ion scattering and isotopic labeling methods. We observe that, after NO annealing at 850 °C, both O and N incorporate near the SiO2/Si interface. There is no nitrogen and little newly incorporated oxygen observed at the surface, implying that NO diffuses through the oxide film and dissociates and reacts at the interface. For N2O annealing, atomic oxygen resulting from decomposition of the gas can replace oxygen atoms in both oxide and oxynitride films. This replacement is most important at the surface, but also, to a smaller extent, occurs in the middle of the film. For ultrathin oxynitride films, oxide growth during reoxidation is faster in N2O than in pure O2. Atomic oxygen also influences the nitrogen distribution, which moves further into the film and accumulate at the new interface. We discuss the roles of atomic oxygen and peroxyl bridging oxygen species in explaining the observed phenomena. © 2000 American Institute of Physics. @S0021-8979~00!01303-7#