US 7,371,703 B2
Optical glass suffering little change in refractive index by radiation of light
Akira Masumura, Sagamihara (Japan); Muneo Nakahara, Sagamihara (Japan); Satoru Matsumoto, Sagamihara (Japan); and Tatsuya Senoo, Sagamihara (Japan)
Assigned to Kabushiki Kaisha Ohara, Kanagawa-ken (Japan)
Filed on Sep. 18, 2003, as Appl. No. 10/666,232.
Application 10/666232 is a division of application No. 09/872842, filed on Jun. 01, 2001, granted, now 7,196,027.
Claims priority of application No. 2000-167377 (JP), filed on Jun. 05, 2000; and application No. 2000-330066 (JP), filed on Oct. 30, 2000.
Prior Publication US 2004/0063563 A1, Apr. 01, 2004
Int. Cl. C03C 3/247 (2006.01); C03C 3/16 (2006.01); C03C 3/17 (2006.01); C03C 3/102 (2006.01)
U.S. Cl. 501—44  [501/45; 501/46; 501/48] 7 Claims
 
7. A method of providing an optical glass for lenses of an optical system of an i-line stepper, said method comprising utilizing in said i-line stepper a lens made from an optical glass comprising, in mass %,
   
  P2O5  4-39%
  Al2O3  0-9%
  MgO  0-5%
  CaO  0-6%
  SrO  0-9%
  BaO  0-10%
  Y2O3 + La2O3 + Gd2O3 + Yb2O3 in the total amount of 0-20%
  Where
  Y2O3  0-10%
  La2O3  0-10%
  Gd2O3  0-20%
  and
  Yb2O3  0-10%
  TiO2  0-0.1%
  SnO2  0-1%
  As2O3  0-0.5%
  Sb2O3  0-0.5%
  AlF3  0-29%
  MgF2  0-8%
  CaF2  0-27%
  SrF2  0-27%
  BaF2 10-47%
  YF3  0-10%
  LaF3  0-10%
  GdF3  0-10%
  LiF  0-3%
  NaF  0-1%
  KF  0-1%
the total amount of F in one or more of the fluorides being 10-45% and
the total amount of one or more of MgF2, CaF2, SrF2 and BaF2 being
30-70%.