Refractive index control of core layer using PECVD and FHD for silica optical waveguide

Silicon oxynitride (SiON) and GeO2–SiO2 layers as core layers deposited using the plasma-enhanced chemical vapor deposition (PECVD) and flame hydrolysis deposition (FHD), respectively. For PECVD technique, the deposition rate monotonically rises with increasing r.f. power from approximately 4.5 μm/h at the power of 60 W to 5.9 μm/h at the power of 180 W. As r.f. power increased from 60 to 180 W, refractive index (RI) of SiON films decreased from 1.5312 to 1.4620. For FHD technique, the RI increases from 1.4615 to 1.4809 with the increase in the GeCl4 flow rate from 30 to 100 sccm. Material grown by two processes, FHD and PECVD, exhibited the similar etching characteristics by inductively coupled plasma etching.