Hydrogen-containing SiCN protective films for magneto-optical media

Three types of SiC-SiN film were investigated for protective layers of rare-earth transition-metal thin films. The SiC-SiN films were prepared by RF magnetron sputtering with varying combinations of target and reactive gas: (1) SiC/Ar and N₂, (2) Si/Ar, N₂, and CH₄, and (3) Si/Ar, NH₃, and CH ₄. The SiC-SiN films of the first and second types were chemically unstable. The films of the third type (SiCH:H) were stable and had good optical properties (transmittance, >90%; refractive index, 1.9-2.1). Deposition rates of SiCN:H films were 1.5 times greater than those of SiN films. Magnetooptical media of polycarbonate substrates using the SiCN:H films had high sensitivity and reliabilities. Optimum recording powers for the media using the SiCN:H films were 1-2 mW lower than for the media with SiN films at linear velocity 4-12 m/s. For the media with SiCN:H films no appreciable changes were observed in values of carrier-to-noise ratio and bit error rate after a 75°C-80% relative humidity aging test for over 1500 h and after a Z/AD test of over 40 cycles. These results can be explained on the assumption that hydrogen and carbon bound to Si and N make the SiCN:H film similar to organic structures with flexibility and hence improve affinities between the film and substrate