PECVD SiO2 and SiON films dependant on the rf bias power for low-loss silica waveguide

SiO2 and SiON films were deposited by radiofrequency plasma-enhanced chemical vapor deposition (rf PECVD) technique using SiH4 and N2O as precursor gases. The refractive index (n) decreases to 1.4480 with the increase of the rf bias power from 0 to 75 W and again increases to 1.4486 at the rf bias power of 100 W. A uniform accumulation of fine grains with the root-mean-square (RMS) surface roughness within the area ∼1.5 nm was detected and the grains pack together very densely. The thickness, refractive index, and surface morphology of the films were characterized by prism coupler, scanning electron microscopy (SEM) and atomic force microscopy (AFM).