N₂ doped SiO₂-SiON planar waveguides deposited by PECVD method

Silica based planar lightwave circuits (PLCs) have been applied to various kinds of wave-guided optical passive devices. Silicon dioxide (SiO₂) and silicon oxynitride (SiON) thick films have been deposited by plasma enhanced chemical vapor deposition (PECVD). SiO₂ and SiON films were obtained at low temperatures (< 350 °C) by the decomposition of appropriate mixtures of gasses under suitable rf power and gas flow ratio. After the deposition of the films, the films were annealed at 1050 °C in a nitrogen atmosphere for 3 h to remove absorption. The deposition rate monotonically rises with deposition condition from approximately 2.8 to 9.4 μm/h, refractive index of the films varied from 1.4582 to 1.5312. The silicon content of the films is independent of the deposition condition and for all layers it is from 32 to 35%. The thickness, refractive index and surface morphology of the films were characterized by prism coupler, scanning electron microscopy (SEM) and atomic force microscopy (AFM).