B-Si-N composite thin films were prepared by the plasma enhanced chemical vapour deposition method of inductive couple. The purpose of this paper is a micro structual control of boron nitride film, so we added Si in this film. The source gases used were B2H6, SiH4 and N2. The rf power, tempareture of substrate and gas pressure during depositions were 20 W, 300°C and 2 × 10-2 Torr, respectively. The physical, mechanical and optical properties of the films were investigated by several methods to clarify the effect of Si content. The following results were obtained;
1) The prepared B-Si-N thin films were composed of two phases of BN and SiNx.
2) The hardness (Hv) of the thin films gradually decreased from 6, 000 to 3, 000 as Si content increaced from O to 48 at%.
3) The fracture toughness of the thin film improved dramatically when Si content exceeded 10 at%.
4) The transmission and refractive index within a range between 700 and 2, 000 nm in wavelength, were 95-99% and 1.4-1.9 respectively depending on Si content.
