Influences of silicon nano-crystallized structures on the optical performance of silicon oxynitride rib-type waveguides

Silicon oxynitride (SiON) films were deposited on p-type (100) silicon substrates by plasma enhanced chemical vapor deposition (PECVD), at the temperature of 300 °C, using silane (SiH4), nitrogen (N2), ammonia (NH3) and laughing gas (N2O) as gas precursors. The effects of the processing gas ratio of N2O/(N2 + NH3) on the optical properties, microstructure and chemical bonding evolutions of SiON material, and the influences of silicon nano-crystallized structures on the optical performance of SiON-based rib-type optical waveguides were studied. Microstructure evolutions analysis and optical measurements indicated that the refractive index and the extinction coefficient could be precisely determined by controlling the N2O/(N2 + NH3) ratio and the thermal annealing process. A greater density and dimension of silicon nano-crystallized structures resulted in more optical scattering effect phenomena occurring between the interface of silicon nano-crystallized structure and SiON matrix and more optical propagation loss.