Optical characterization of silica based waveguide prepared by plasma enhanced chemical vapor deposition

Silicon dioxide (SiO2) and silicon oxynitride (SiON) thick films used for cladding and core layer of silica based waveguides were fabricated by plasma enhanced chemical vapor deposition (PECVD) method, at a low temperature (320 degreesC) and from (SiH4+N2O+N-2) gas mixtures. The effects of deposition parameters on properties of SiO2 and SiON thick films were investigated by variations of SiH4, N-2, N2O flow ratio and RF power. The obtained SiO2 films had a high thickness and refractive index of 1.460 +/- 0.001 with the annealing process. FTIR and XPS revealed that deposited films were nearly stoichiometric composition with no presence of hydrogen content. SiON films had a 0.75 % higher refractive index than the cladding layer and a high thickness(> 5 mum).