Influence of hydrogen on losses in silicon oxynitride planar optical waveguides

We have examined the influence of bonded hydrogen on the losses in silicon oxynitride (SiON) planar optical waveguides on silicon substrates having a silicon dioxide buffer layer. In the SiON layer grown by plasma enhanced chemical vapour deposition, hydrogen was mainly bonded to silicon as evidenced by strong absorption at 2160 cm -1 . The concentration of bonded hydrogen was reduced from 1.2 × 10 22 cm -3 to 5 × 10 21 cm -3 as the substrate temperature was raised from 100 to 300 °C. The corresponding change in the loss was from 1.5 to 1.2 dB cm -1 at 632.8 nm.