Claims
- 1. An optical lithography apparatus comprising:an illumination optical system that emits exposure light of a wavelength less than about 200 nm towards a mask having a pattern; and a projection optical system that projects an image of the pattern on the mask onto a substrate via the exposure light, wherein at least one of the illumination optical system and the projection optical system includes a light-transmitting optical member formed of crystalline calcium fluoride with a potassium content of less than about 0.5 ppm.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-252554 |
Sep 1998 |
JP |
|
Parent Case Info
This is a divisional of application(s) application Ser. No. 09/389,462 filed on Sep. 3, 1999 now U.S. Pat. No. 6,226,128.
US Referenced Citations (5)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0908716 A1 |
Apr 1999 |
EP |
10001310 A |
Jan 1998 |
JP |