Optimization of Fabrication Process for SiON/SiOx Films Applicable as Optical Waveguides

In this paper, the analysis of silicon oxynitride (SiON) films, deposited utilizing the plasma enhanced chemical vapor deposition (PECVD) process, for optical waveguides on silicon wafers is presented. The impact of N2O flow rate on various SiON film properties was investigated. The thickness and refractive index were measured by micro-spot spectroscopic reflectometry and confirmed by spectroscopic ellipsometry. The chemical composition of SiON films was analyzed using Secondary Ion Mass Spectrometry (SIMS). The surface roughness was analyzed using Atomic Force Microscopy (AFM). Increasing the N2O flow rate during deposition caused the deposition rate to increase and the refractive index to decrease. By changing the flow rate of gases into the chamber during the PECVD process, it is possible to precisely adjust the oxygen (O2) ratio and nitrogen (N2) ratio in the SiON film and thus control its optical properties. This was possibility utilized to fabricate SiON films suitable to serve as a waveguide core for optical waveguides with a low refractive index contrast.