Nitrogen bonding structure in ultrathin silicon oxynitride films on Si(100) prepared by plasma nitridation

High-resolution core-level photoemission using synchrotron radiation is applied to the ultrathin SiON films on Si(100) nitrided by N₂ plasma, which gives a systematic view of the various transient or stable N chemical states. N0.3em0ex1s spectra disclose at least two characteristic nitrogen bonding states in addition to the well-established and thermally stable NSi₃ species. While the stable NSi₃ species are located near the interface, the extra high-binding energy states are distributed mainly in the surface region. Among these high-binding species, assigned reliably to the NO and NO₂ bonding states, only the NO species is quasi-stable up to 9000.2em0ex^∘C, surviving the post-annealing treatment. These oxidized N species convert to the stable NSi₃ mostly within the SiO₂ film. This result indicates that the NO and NO₂ species formed by energetic plasma process is kinetically trapped within the shallow part of the film. It is inferred that the quasi-stable NO species would play an important role in characterizing the physical and electrical properties of the plasma oxynitrides.