Position measurement of optical elements in a lithographic apparatus

Abstract

A lithographic apparatus includes a projection system which includes a plurality of optical elements configured to project a beam of radiation onto a radiation sensitive substrate. The lithographic apparatus also includes a metrology frame structure which includes a part of one or more optical element measurement systems to measure the position and/or orientation of at least one of the optical elements. The plurality of optical elements, a patterning device stage, and a substrate stage are arranged such that, in a two dimensional view on the projection system, a rectangle is defined such that it envelops the plurality of optical elements, the patterning device stage, and the substrate stage. The rectangle is as small as possible. The metrology frame structure is positioned within the rectangle.

1 . A lithographic apparatus, comprising:
 a projection system comprising a plurality of optical elements configured to project a beam of radiation onto a radiation sensitive substrate; and   a metrology frame structure comprising a part of one or more optical element measurement systems to measure a position and/or an orientation of at least one of the optical elements,   wherein:
 the plurality of optical elements, a patterning device stage, and a substrate stage are configured so that, in a two dimensional view on the projection system, a rectangle envelops the plurality of optical elements, the patterning device stage, and the substrate stage; 
 the rectangle is as small as possible; 
 the metrology frame structure is positioned within the rectangle; and 
 the plurality of optical elements comprises an outer group of optical elements surrounding the metrology frame structure. 
   
     
     
         2 .- 21 . (canceled)