Catadioptric reduction projection optical system

Abstract

A catadioptric reduction projection optical system having a first lens unit having negative refractive power and widening a light beam from a reticle, a prism type beam splitter for transmitting therethrough a light beam from the first lens unit, a concave reflecting mirror for returning the light beam emerging from the beam splitter to the beam splitter while converging it, and a second lens unit having positive refractive power and converging the light beam returned to the beam splitter and reflected by the beam splitter, and forming the reduced image of a pattern on the reticle on a wafer.

What is claimed is:  
     
         1 . A catadioptric reduction projection optical system for reduction-projecting the pattern of a first surface onto a second surface, including: 
 a first lens unit G 1  of negative refractive power for making a light beam from said first surface diverge;    a prism type beam splitter for transmitting therethrough or reflecting the light beam from said first lens unit G 1 ;    a concave reflecting mirror for returning the light beam emerging from said beam splitter to said beam splitter while condensing it; and    a second lens unit G 2  of positive refractive power for converging the light beam returned to said beam splitter and reflected by or transmitted through said beam splitter, and forming the reduced image of the pattern of said first surface on said second surface.    
     
     
         2 . A catadioptric reduction projection optical system according to    claim 1   , wherein the radius of curvature of said concave reflecting mirror is seventeen times to twenty-five times as great as the diameter of an exposure area on said second surface.  
     
     
         3 . A catadioptric reduction projection optical system according to    claim 1   , wherein the magnification of said concave reflecting mirror is 0.6 time to 1.1 times.  
     
     
         4 . A catadioptric reduction projection optical system according to    claim 1   , wherein the inclination of the off-axis principal ray incident on said concave reflecting mirror with respect to the optical axis is 5 degrees or less.  
     
     
         5 . A catadioptric reduction projection optical system for reduction-projecting the pattern of a first surface onto a second surface, including: 
 a prism type beam splitter for dividing the optical path of a light beam from said first surface into a reflection optical path and a transmission optical path;    a concave reflecting mirror disposed on one of the transmission optical path and the reflection optical path of the object light beam by said prism type beam splitter for returning the light beam from said object to said prism type beam splitter;    a first lens unit G 1  of negative refractive power disposed between said prism type beam splitter and said first surface for making the light beam from said first surface diverge; and    a second lens unit G 2  of positive refractive power for converging the light beam returned to said prism type beam splitter by said concave reflecting mirror and emerging from said prism type beam splitter, and forming the reduced image of the pattern of said first surface on said second surface.    
     
     
         6 . A catadioptric reduction projection optical system according to    claim 1   , wherein said prism type beam splitter has a polarizing beam splitter surface, and said projection optical system has a quarter wavelength plate disposed between said prism type beam splitter and said concave reflecting mirror.