| 摘要 |
PROBLEM TO BE SOLVED: To form a protective film having high corrosion resistance for a recording medium by keeping a substrate at a negative potential to the ground potential of a film forming device when a protective layer to protect a magnetic recording layer is to be formed. SOLUTION: A negative substrate bias is applied in a plasma CVD film forming process so as to control the energy of ions reaching the substrate. Thereby, the film quality of a carbon protective layer can be controlled as well as the coverage of the magnetic layer surface can be increased. A voltage to be applied is preferably -600 V or higher and -200 V or lower. Usually in an ion beam vapor deposition process, a substrate 20 is grounded, and a positive voltage V1 corresponding to the irradiation energy is added to a metal ion source 21, while a negative high voltage V2 corresponding to an ion drawing potential is applied on an ion accelerating zone 22, mass separation zone 23 and ion deceleration zone 24. By keeping the substrate at a negative potential V3 to the ground potential, a dense protective film having high hardness can be formed.
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