Structural and optical properties of a-SiCN thin film synthesised in a microwave plasma at constant temperature and different flow of CH4 added to HMDSN/N2/Ar mixture

Amorphous SiCN (a-SiCN) thin films were deposited by microwave plasma assisted chemical vapour deposition (MPACVD) using N2, Ar, CH4 and vaporised hexamethyldisilazane (HMDSN) gases. The CH4 ratio (0 to 12%) effect on composition, structural and optical properties of thin layers synthesised at a constant growth temperature of 550 °C has been studied. It was found that layers are mainly composed of silicon nitride like compound and that CH4 addition leads to denser and smoother films. An augmentation of the refractive index from 1.72 to 2.05 and Tauc gap from 4.3 to 4.7 eV has also been measured with CH4 ratio increase from 0 to 12%. These results show that CH4 addition to the feed gas allows varying the composition, morphology and the optical properties of HMDSN a-SiCN based films.