Infrared response of silicon oxynitrides investigated by high resolution electron energy loss spectroscopy

Silicon oxynitride films of various compositions were grown in situ by RF-plasma sputtering. The high-resolution electron-energy-loss spectra were analyzed in the framework of the dielectric theory after addition of a characteristic background structure. The evolution of the energy-loss peaks as a function of [N]/([N]+[O]) concentration ratio clearly exhibits a one-mode behavior. This suggests that sili- con oxynitride is characterized by a mixture of Si-O and Si-N bonds at the atomic level. An exponential frequency shift of the main peak is observed as a function of the concentration ratio. Infrared optical parameter values are provided for thermal and RF-plasma sputtered oxides, and for two compositions of RF-plasma SiOxNy[y/(y+x)=0.37 and 0.80] silicon oxynitrides.