Optical: systems and elements – Mirror – Plural mirrors or reflecting surfaces
Patent
1996-04-01
1998-04-07
Shafer, Ricky D.
Optical: systems and elements
Mirror
Plural mirrors or reflecting surfaces
359861, 359355, 359366, 378 34, 378 70, 378 84, 355 67, G02B 510, G02B 1700, G21K 106, G21K 500
Patent
active
057371377
ABSTRACT:
A critical illumination condenser system, particularly adapted for use in extreme ultraviolet (EUV) projection lithography based on a ring field imaging system and a laser produced plasma source. The system uses three spherical mirrors and is capable of illuminating the extent of the mask plane by scanning either the primary mirror or the laser plasma source. The angles of radiation incident upon each mirror of the critical illumination condenser vary by less than eight (8) degrees. For example, the imaging system in which the critical illumination condenser is utilized has a 200 .mu.m source and requires a magnification of 26.times.. The three spherical mirror system constitutes a two mirror inverse Cassegrain, or Schwarzschild configuration, with a 25% area obstruction (50% linear obstruction). The third mirror provides the final pupil and image relay. The mirrors include a multilayer reflective coating which is reflective over a narrow bandwidth.
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Cohen Simon J.
Seppala Lynn G.
Carnahan L. E.
Sartorio Henry P.
Shafer Ricky D.
The Regents of the University of California
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