Chemical bonding structures of silicon oxynitride films grown by ionised N₂ and pure O₂ gas mixtures at low temperature

The ultrathin silicon oxynitride (SiO_xN_y) films were formed using the direct oxynitridation of Si using ionised N₂ and pure O₂ gas mixtures at the relatively low temperature (600°C). The in situ X-ray photoelectron spectroscopy (XPS) was used to assess the chemical composition and chemical state of the SiO_xN_y films. N 1s XPS spectra reveals that at least three characteristic N bonding states such as N≡Si₃, N-(SiO_x)₃ and N = Si₂-O bonds are formed in the SiO_xN_y films. As growth time increases, the N-(SiO_x)₃ bond is dominant in SiO_xN_y films, although N≡Si₃ bonds are mainly formed in the initial growth stage at the temperature of 600°C. As considering the absence of direct bonding between N and O atoms, the nitridation and oxidation processes are believed to proceed independently. The increase in the growth temperature leads to the breakdown of both N-(SiO_x) ₃ and N≡ = Si₃ bonds and transformation into N = Si₂-O bonding structure.