Minimizing hydrogen content in silicon oxynitride by thermal oxidation of silicon-rich silicon nitride

This work reports a detailed study of the re-oxidation effects on the hydrogen content and optical properties of silicon oxynitride films grown by plasma enhanced chemical vapor deposition (PECVD) with N2O, NH3 and SiH4 as the precursors. Results showed that the silicon oxynitride deposited with gas flow rates of NH3/N2O/SiH4 = 20/500/20 (sccm) has favorable properties for integrated waveguide applications. The refractive index of this layer is about 1.57 at 632.8 nm wavelength and the layer has a comparative low density of NH bonds. With a high temperature re-oxidation of the as-deposited film, the hydrogen content of the oxynitride film was reduced from 2.255 × 1022 to 6.98 × 1020 cm−3 which is attributed to the removal of excess silicon oxidation and hydrogen bonds.