Polarization-modulating optical element

Abstract

A microlithography optical system includes a projection objective and an illumination system that includes a temperature compensated polarization-modulating optical element. The temperature compensated polarization-modulating optical element includes a first polarization-modulating optical element of optically active material, the first polarization-modulating optical element having a first specific rotation with a sign. The temperature compensated polarization-modulating optical element includes also includes a second polarization-modulating optical element of optically active material, the second polarization-modulating optical element having a second specific rotation with a sign opposite to the sign of the first specific rotation.

1 . An illumination optical apparatus which illuminates an object having a pattern with illumination light, the illumination optical apparatus comprising:
 a polarization modulating member made of an optical material with optical activity, the polarization modulating member having a thickness that varies with respect to azimuthal positions about an optical axis of the illumination optical apparatus, the polarization modulating member being arranged around the optical axis so as to surround the optical axis, a direction of an optic axis of the optical material being substantially coincident with a direction of the optical axis of the illumination optical apparatus,   wherein the polarization modulating member rotates a polarization direction of the illumination light so that the illumination light, being incident on the polarization modulating member in a linearly polarized state having the polarization direction along a single direction, is changed to a linearly polarized state having polarization directions being substantially coincident with an azimuthal direction about the optical axis at a pupil plane of the illumination optical apparatus, wherein the polarization modulating member has a region without optical activity in an area perpendicular to the optical axis, the region being on the optical axis, and   wherein the polarization modulating member has substantially constant thicknesses in at least two radial directions that are not parallel to each other.   
     
     
         2 . The illumination optical apparatus according to  claim 1 , wherein the illumination light is irradiated onto the object in a polarization state in which a principal component is S-polarized light. 
     
     
         3 . The illumination optical apparatus according to  claim 1 , wherein a first thickness of the polarization modulating member in an optical path of a first part of the illumination light is different from a second thickness of the polarization modulating member in an optical path of a second part of the illumination light, and
 the first part of the illumination light passes through a first portion of the pupil plane away from the optical axis, and the second part of the illumination light passes through a second portion of the pupil plane away from the optical axis, the first and second portions being different from each other.   
     
     
         4 . The illumination optical apparatus according to  claim 3 , wherein the first and second portions are included in an annular region about the optical axis. 
     
     
         5 . An exposure method which exposes a substrate to light via an object having a pattern, the exposure method comprising:
 holding the substrate by the stage;   illuminating the pattern with the light by using the illumination optical apparatus as defined in  claim 1 ; and   projecting an image of the pattern illuminated with the light onto the substrate held by the stage.   
     
     
         6 . The exposure method according to  claim 5 , wherein the substrate is exposed to the light through liquid. 
     
     
         7 . An exposure apparatus which exposes a substrate to light via an object having a pattern, the exposure apparatus comprising:
 a stage which holds the substrate,   the illumination optical apparatus as defined in  claim 1  which illuminates the pattern with the light; and   a projection optical system which projects an image of the pattern illuminated with the light onto the substrate held by the stage, wherein the polarization modulating member has a region without optical activity in an area perpendicular to the optical axis, the region being on the optical axis, and   wherein the polarization modulating member has substantially constant thicknesses in at least two radial directions that are not parallel to each other.   
     
     
         8 . The exposure apparatus according to  claim 7 , wherein the substrate is exposed to the light through liquid. 
     
     
         9 . The exposure apparatus according to  claim 7 , wherein the light is irradiated onto the object in a polarization state in which a principal component is S-polarized light. 
     
     
         10 . The exposure apparatus according to  claim 7 , wherein a first thickness of the polarization modulating member in an optical path of a first part of the light is different from a second thickness of the polarization modulating member in an optical path of a second part of the light, and
 the first part of the light passes through a first portion of the pupil plane away from the optical axis, and the second part of the light passes through a second portion of the pupil plane away from the optical axis, the first and second portions being different from each other.   
     
     
         11 . The exposure apparatus according to  claim 10 , wherein the first and second portions are included in an annular region about the optical axis. 
     
     
         12 . The illumination optical apparatus according to  claim 1 , further comprising a raster plate arranged in an optical path of the illumination light.