| 摘要 |
PURPOSE:To determine the center of rotation of grooves for information and the center of the through-hole of a disk-shaped substrate with good accuracy by depositing a metallic film on a base plate consisting of glass, etc. then subjecting the same to positioning and working by making use of a difference in light reflectivity. CONSTITUTION:A chromium film 13 is deposited by a sputtering to 700Angstrom thickness on the base plate 1 formed by depositing a 1,500Angstrom silicon oxide film 122 by an electron beam vapor deposition method on the surface of the soda lime glass substrate 12 subjected to precision polishing to a rectangular shape having 1.2mu thickness. A positive type photoresist film 14 is further coated to 1,000Angstrom thickness thereon by using a spin coating device and is subjected to prebaking to form the base plate. A photomask and the base plate are brought into tight contact with each other in such a manner that the chromium pattern 112 of the mask and the photoresist film 14 face each other. UV rays 15 are irradiated on the photoresist film to transfer the chromium pattern 112 to the photoresist film 14. The film is thereafter developed and etched to form the chromium pattern 13A corresponding to the grooves for information. The oxide silicon film 1122 is then dry etched with the chromium pattern 13A as a mask to form the grooves 16 for information to the concentrical shapes spaced at 2mum. The central position of the chromium pattern 13A is determined by using a microscope which permits reading in 1mum unit. A through-hole of 15 (+0.05, -0.0)mm diameter is bored by a shaping machine which can make precision positioning. A core bar is inserted into the hole and the base plate is formed to the disk shape of 130+ or -0.05mm outside diameter by rotary grinding. The chromium pattern 13A is finally removed by etching.
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