Formation of Silicon Oxynitride Films with Low Leakage Current Using N2/O2 Plasma near Atmospheric Pressure

We have fabricated ultrathin silicon oxynitride films using N2/O2 plasma near atmospheric pressure. The silicon oxynitride films whose composition was Si3N1.2O4.3, as evaluated by X-ray photoemission spectroscopy, showed a leakage current as low as 1.4×10-4 A/cm2 at 5 MV/cm. Given a capacitance equivalent thickness of 1.9 nm, the leakage current is lower by two orders of magnitude than that of the reported silicon oxynitride films. The conduction mechanism of the leakage current of the film was discussed using direct-tunneling-current simulation with Webtzel-Kramers-Brillouin approximation. We concluded that an increase in the effective tunneling mass of holes, which is probably due to the nitrogen atoms incorporated to Si3N1.2O4.3 films, is responsible for the decrease in the leakage current of silicon oxynitride films.