F. Esaka, K. Furuya, H. Shimada, M. Imamura, N. Matsubayashi,
T. Sato, A. Nishijima, A. Kawana, H. Ichimura, and T. Kikuchi
[J. Vac. Sci. Technol., Vol.15, No.5, pp.2521-2528, 1997]

Surface oxidation mechanisms of titanium nitride (TiN) and chromium nitride (CrN) films were studied by means of x-ray photoelectron (XPS) and absorption spectroscopy (XAS). In the N 1s XPS spectra of both the oxidized TiN and CrN films, a feature assigned to molecular nitrogen was observed in addition to a feature assigned to nitride. The assignment was confirmed by the N K-edge XAS spectra of the TiN and CrN films which exhibited an intense and narrow feature at 401.4 eV. Besides these features, the N 1s XPS spectra of the oxidized TiN films showed a third feature, which was assigned to Nx-Ti-OY like structures taking into account the change in the Ti 2p XPS spectra. However, no evident feature assigned to Nx-Ti-OY like structures was observed in the XAS spectra because of the overlapping with the nitride features. The above results indicated that the CrN films directly changed to chromium oxide (Cr₂O₃) with the formation of molecular nitrogen in the interstitial positions of the surface oxide layers, while the TiN films were oxidized to titanium oxide (TiO₂) through the formation of Nx-Ti-OY like structures. The formation of the Nx-Ti-OY like structures may allow the rapid diffusion of oxygen and hence lower the oxidation resistance of TiN films.