Projection eposure apparatus and method

Abstract

The present invention relates to a projection exposure apparatus ( 10 ) for and method of imaging a reticle (R) having patterned surface onto a substrate (W) in photolithographic processes for manufacturing a variety of devices. The invention further relates to an optical system (C) having a folding member (M 1 ) suited to the projection exposure apparatus, and a method for manufacturing the optical system. The projection exposure apparatus comprises an illumination optical system (IS) and a reticle stage (RS) capable of holding the reticle so the normal line to its patterned surface is in the direction of gravity. The apparatus also includes a substrate stage (WS) capable of holding the substrate with its surface normal parallel to the direction of gravity. The optical system includes a first imaging optical system (A) comprising a concave reflecting mirror and a dioptric optical member arranged along a first optical axis. The first imaging optical system (A) forms an intermediate image of the patterned surface. The optical system also includes a second imaging optical system (B) having a second optical axis, and forms a reduced image of the intermediate image on the substrate. The first folding member is arranged in the optical path from the first imaging optical system to the second imaging optical system. The first and second imaging optical systems and the first and second folding members are positioned so that a reduced image of the pattered surface is formed parallel to the pattern surface of the reticle, and the first and second optical axes are positioned so that they are substantially parallel to the direction of gravity.

What is claimed is:  
     
         1 . An optical system comprising: 
 an optical element; and    a reference surface which is connected to the optical element, for adjusting the optical element.    
     
     
         2 . The optical system according to  claim 1 , further comprising a body which has the reference surface and which holds the optical element.  
     
     
         3 . The optical system according to  claim 2 , wherein the reference surface is perpendicular to an optical axis.  
     
     
         4 . The optical system according to  claim 3 , wherein the references surface has a reflecting surface.  
     
     
         5 . The optical system according to  claim 1 , wherein the reference surface is perpendicular to an optical axis.  
     
     
         6 . The optical system according to  claim 1 , wherein the reference surface has a reflecting surface.  
     
     
         7 . A projection system that makes first and second planes optically conjugate, comprising the optical system according to  claim 1 .  
     
     
         8 . A projection exposure apparatus that transfers an image of a pattern on a mask onto a substrate, comprising the optical system according to  claim 1 .  
     
     
         9 . An imaging method comprising the steps of: 
 preparing the projection optical system according to  claim 7 , and    forming an image on a first plane onto a second plane with the projection optical system.