Deposition and characterization of SiON films using HMDS for photonics applications

Abstract

Silicon oxynitride (SiON) films were deposited using a thermal chemical vapour deposition (CVD) system in the temperature range of 760 to 820 °C with hexamethyldisilazane (HMDS), ammonia (NH3) and oxygen (O2) precursors. The deposited films were characterized by using ellipsometry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and energy dispersive analysis of x-rays (EDAX). The effect of deposition temperature on the physical and optical properties of deposited SiON films has been analysed. It has been observed that the refractive index of the deposited films increases with corresponding increase in deposition temperature. The compressive stress decreases in accordance with increase in deposition temperature. The peak position of Si–O–Si stretching vibration moves towards a lower wave number while FWHM increases with increase in the deposition temperature. The peak intensity of Si–H, Si–OH and N–H stretching peaks found to reduce with increasing the deposition temperature. This may be an indication of improvement in the quality of the deposited films. EDAX clearly shows the peaks corresponding to Si, N and O, which confirm successful growth of SiON films. These deposited silicon oxynitride films exhibit a very well controlled refractive index in the range of 1.54–1.74, which is very attractive for the application of SiON in photonic wave-guide devices.