FTIR and spectroscopic ellipsometry investigations of the electron beam evaporated silicon oxynitride thin films

FTIR and variable angle spectroscopic ellipsometer in conjunction with computer simulation were employed to investigate the electron beam evaporated SiOxNy thin films. FTIR showed a large absorption band located between 600 and 1250 cm−1, which indicates that Si–O and Si–N bands are overlap in SiOxNy films. A three layers model was used to fit the calculated data to the experimental ellipsometric spectra. The main layer was described by Cauchy model while the interface layer and the surface layer were described using Tauc–Lorenz oscillator and Bruggeman effective medium approximation, respectively. The thickness, the refractive index and the extinction coefficient were accurately determined. The refractive index at 630 nm was found to increase from 1.74 to 1.85 with increasing the film thickness from 191.6 to 502.2 nm. The absorption coefficient was calculated from the obtained extinction coefficient values and it has been used to calculate the Tauc and Urbach energies.