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 Si3N4 (840 cm−1). The 960 cm−1 peak was observed in the films for which an N 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 ≡Si–N–Si≡ structure. However, the 960 cm−1 peak was absent in the films for which the N 1s peak was observed at about 397.8 eV, being close to the binding energy associated with the Si3≡N structure. We conclude that the absorption peak at 960 cm−1 arises from the ≡Si–N–Si≡ structure of doubly bonded N atoms with two Si atoms, not affected by any oxygen atoms.