Reflective-Type Projection Optical System and Exposure Apparatus Equipped with the Reflective-Type Projection Optical System

Abstract

A reflective-type projection optical system has 8 reflective mirrors that form a reduced image of a first surface on a second surface. A first reflective imaging optical system (G 1 ) forms an intermediate image of the first surfaces and a second reflective imaging optical system (G 2 ) forms an image of the intermediate image on the second surface. The first reflective imaging optical system has, from the first surface side in order of light beam incidence, a first reflective mirror (M 1 ), a second reflective mirror (M 2 ), a third reflective mirror (M 3 ), and a fourth reflective mirror (M 4 ). The second reflective imaging optical system has, from the first surface side in order of light beam incidence, a fifth reflective mirror (M 5 ), a sixth reflective mirror (M 6 ), a seventh reflective mirror (M 7 ), and an eighth reflective mirror (M 8 ). At least one of the reflective surfaces of these 8 reflective mirrors is composed of a spherical surface.

1 . A reflective-type projection optical system for forming a reduced image of a first surface on a second surface, the optical system comprising a first reflective imaging optical system for forming an intermediate image of the first surface and a second reflective imaging optical system for forming an image of the intermediate image on the second surface;
 the first reflective imaging optical system comprising, from the first surface side in order of light beam incidence, a first reflective mirror, a second reflective mirror, a third reflective mirror, and a fourth reflective mirror; and   the second reflective imaging optical system comprising, from the first surface side in order of light beam incidence, a fifth reflective mirror, a sixth reflective mirror, a seventh reflective mirror, and an eighth reflective mirror; and   at least one of the reflective surfaces of the reflective mirrors being configured as a spherical surface, and the remaining reflective surfaces of the mirrors being configured as aspheric surfaces.   
   
   
       2 . The reflective-type projection optical system described in  claim 1 , wherein the fourth reflective mirror or the fifth reflective mirror is composed of a spherical surface. 
   
   
       3 . The reflective-type projection optical system described in  claim 1 , wherein the reflective mirror that requires a relatively severe manufacturing tolerance, from among the reflective mirrors, is composed of a spherical surface. 
   
   
       4 . The reflective-type projection optical system described in  claim 1 , wherein the reflective mirror with the relatively largest angle of incidence for the light rays incident upon the reflective surface, from among the reflective mirrors, has a spherical shape. 
   
   
       5 . The reflective-type projection optical system described in  claim 1 , wherein the reflective mirror with the surface area of the region reflecting light beams that contribute to imaging that is relatively smallest, from among the reflective mirrors, has a spherical shape. 
   
   
       6 . The reflective-type projection optical system described in  claim 1 , wherein the first reflective imaging optical system comprises, sequentially from the object side, a reflective mirror, a concave mirror, a convex mirror, and a concave mirror. 
   
   
       7 . The reflective-type projection optical system described in  claim 1 , wherein the second reflective imaging optical system comprises, sequentially from the object side, a concave mirror, a reflective mirror, a convex mirror, and a concave mirror. 
   
   
       8 .- 16 . (canceled) 
   
   
       17 . The reflective-type projection optical system described in  claim 1 , wherein the image-side numerical aperture NA is at least 0.20 or greater. 
   
   
       18 . An exposure apparatus comprising an illumination system for illuminating a pattern set on a first surface and the reflective-type projection optical system described in  claim 1  for exposing the pattern onto a photosensitive substrate on a second surface. 
   
   
       19 . The exposure apparatus described in  claim 18 , wherein the illumination system has a light source configured to supply X-rays as the exposure light, and further comprising a mask stage which holds the mask and moves the mask relative to the reflective-type projection optical system and a substrate stage which holds the photosensitive substrate and moves the photosensitive substrate relative to the reflective-type projection optical system. 
   
   
       20 . A reflective-type projection optical system comprising at least eight reflective mirrors for forming a reduced image of a first surface on a second surface, wherein:
 at least the mirror with the relatively largest angle of incidence for the light beams incident upon the reflective surfaces, from among the eight reflective mirrors, has a spherical surface.   
   
   
       21 . A reflective-type projection optical system comprising at least eight reflective mirrors for forming a reduced image of a first surface on a second surface, wherein:
 at least the mirror with the smallest surface area for reflecting light beams that contribute to imaging, from among the eight reflective mirrors, has a spherical surface.