PHASE-CHANGE OPTICAL DISKS WITH HIGH WRITING SENSITIVITY USING A-SIN-H PROTECTIVE FILMS PREPARED BY ELECTRON-CYCLOTRON RESONANCE PLASMA CHEMICAL VAPOR-DEPOSITION

Hydrogenated amorphous silicon nitride (a-SiN:H) films prepared by electron cyclotron resonance plasma chemical vapor deposition (ECR-PCVD) technique are applied as the protective layers of phase-change optical disks. The properties of protective films and the disk structure are investigated with an aim toward improving the writing sensitivity and overwrite repeatability. The writing laser power required to obtain a sufficient carrier-to-noise ratio (C/N) of 53 dB can be as low as 11 mW at a linear velocity of 10 m/s. The erasability is more than 26 dB, the power tolerance is about 3 mW, and overwrite repeatability is 10(6) cycles. This is attributed to the superior protective film properties such as decreased thermal conductivity and excellent surface flatness.