| 摘要 |
PROBLEM TO BE SOLVED: To enable an optical device to be used in a vacuum ultraviolet region of <=200 nm wavelength. SOLUTION: A fluorite (CaF2) with 2 inches diameter and 2 mm thickness is used for a substrate 11. A calcium fluoride (CaF2) film 12 with 0.434 μm film thickness is deposited on the substrate 11 with a resistance heating vacuum deposition device (a). Succeedingly a pattern of a chromium mask 13 is reduced baked to a positive photoresist on the substrate 11 using an i-line stepper with 365 nm wavelength λ. The etching is carried out with a parallel lithographic dry etching device using the developed resist pattern as a mask. As a chemical etching with a halogen type dry etching gas is generally not applicable to a fluoride compound of which the representative one is fluorite, the mixed gas of argon and hydrogen is used as an inert gas to etch the CaF2 film 12 on the substrate 11. Furthermore, by using masks 14, 15 and by repeating the above process a four-step diffraction optical device 16 is manufactured (b). |
