Spectroscopic ellipsometry and FTIR characterization of annealed SiOxNy:H films prepared by PECVD

We investigated the optical and the vibrational properties of amorphous SiOxNy:H thin films deposited on silicon substrate using the plasma enhanced chemical vapor deposition technique. The films are obtained with a ratio R = N2O/(N2O + NH3) = 0.62 at 200 °C of the deposited temperature, then annealed from 400 °C to 1000 °C. The characterization of the SiOxNy:H films is done by ellipsometry and FTIR techniques. In our ellipsometric investigation, we found that there is an impact of the annealing temperature on the volume fractions of SiO2, Si3N4 and H2 phases of the MG model. The refractive index changes between 1.836 and 1.853 and the film thickness decreases from 732.30 nm to 659.12 nm as the annealing temperature goes up from 200 °C to 1000 °C. The O/Si ratio of the SiOxNy:H films shifts from 0.116 to 0.278 and the N/Si ratio changes from 1.256 to 1.148. In the infrared study, the Si–O, Si–N, Si–H and N–H bonds are identified from FTIR measurements. Finally, a correlation between the SE and FTIR measurements was established to improve the quantitative analysis of the SiOxNy:H films composition. In that case, we used the optimized areas of the infrared bands to determine the concentration of the Si–O and Si–N bonds. Along with the annealing temperature, the concentration of the Si–O bonds increased from 2.02 × 1022 cm−3 to 4.83 × 1022 cm−3 whereas that of the Si–N bonds decreased from 37.96 × 1022 cm−3 to 16.62 × 1022 cm−3.