Bonding configurations of nitrogen absorption peak at 960 cm−1 in silicon oxynitride films

We investigated bonding configurations of nitrogen atoms in silicon oxynitride films, resulting in a 960 cm⁻¹ absorption peak, which is a higher frequency than that for ${\mathrm{Si}}_{\mathrm{3}}{\mathrm{N}}_{\mathrm{4}}$ (840 cm⁻¹). The 960 cm⁻¹ peak was observed in the films for which an $\mathrm{N}\text{\hspace{0.05em}1s}$ x-ray photoemission peak was observed with a binding energy of about 398.6 eV, which has been reported as a binding energy associated with the $\equiv \mathrm{Si–N–Si}\equiv$ structure. However, the 960 cm⁻¹ peak was absent in the films for which the $\mathrm{N}\text{\hspace{0.05em}1s}$ peak was observed at about 397.8 eV, being close to the binding energy associated with the ${\mathrm{Si}}_{\mathrm{3}}\mathrm{\equiv N}$ structure. We conclude that the absorption peak at 960 cm⁻¹ arises from the $\equiv \mathrm{Si–N–Si}\equiv$ structure of doubly bonded N atoms with two Si atoms, not affected by any oxygen atoms.