Illumination optical unit and optical system for euv projection lithography

Abstract

An illumination optical unit for EUV projection lithography serves for obliquely illuminating an illumination field, in which an object field of a downstream imaging catoptric optical unit and a reflective object to be imaged can be arranged. A pupil generating device of the illumination optical unit is embodied so that an illumination pupil results, which brings about a dependency of an imaging telecentricity against a structure variable of the object to be imaged. This dependency is such that a dependency of the imaging telecentricity against the structure variable of the object to be imaged on account of interaction of the oblique illumination with structures of the object to be imaged is at least partly compensated for. An optical system for EUV projection lithography also has an imaging catoptric optical unit alongside an illumination optical unit and can additionally have a wavefront manipulation device.

1 .- 11 . (canceled) 
     
     
         12 . An optical unit configured to obliquely illuminate an illumination field, the optical unit comprising:
 a pupil generating device configured so that, during operation of the optical unit, an illumination pupil brings about a dependency of an imaging telecentricity on a structure variable of an object in the illumination field so that a dependency of the imaging telecentricity on the structure variable of the object is at least partly compensated due to an interaction of the oblique illumination with structures of the object,   wherein the optical unit is an EUV projection lithography illumination optical unit.   
     
     
         13 . The optical unit of  claim 12 , wherein the optical unit is configured so that, during operation of the optical unit, the illumination pupil has a ring shaped ring pupil contribution and a compensation pupil contribution within the ring of the ring pupil contribution. 
     
     
         14 . The optical unit of  claim 12 , wherein the optical unit is configured so that, during operation of the optical unit, the illumination pupil has a dipole pupil contribution and a compensation pupil contribution outside dipoles of the dipole pupil contribution. 
     
     
         15 . The optical unit of  claim 14 , wherein the optical unit is configured so that during operation of the optical unit:
 the pupil plane has first and second main coordinates;   the object field has first and second main coordinates;   the first main coordinate of the object field is perpendicular to the illumination plane;   the second main coordinate of the object field is in the illumination plane;   the first main coordinate of the pupil plane corresponds to the first main coordinate of the object field;   the second main coordinate of the pupil plane corresponds to the second main coordinate of the object field; and   the illumination pupil is non-mirror asymmetric with respect to at least coordinate selected from the group consisting of the first main coordinate of the object field and the second main coordinate of the object field.   
     
     
         16 . The optical unit of  claim 13 , wherein the optical unit is configured so that during operation of the optical unit:
 the pupil plane has first and second main coordinates;   the object field has first and second main coordinates;   the first main coordinate of the object field is perpendicular to an illumination plane of incidence of the oblique illumination;   the second main coordinate of the object field is in the illumination plane of incidence of the oblique illumination;   the first main coordinate of the pupil plane corresponds to the first main coordinate of the object field;   the second main coordinate of the pupil plane corresponds to the second main coordinate of the object field; and   the illumination pupil is non-mirror asymmetric with respect to at least coordinate selected from the group consisting of the first main coordinate of the object field and the second main coordinate of the object field.   
     
     
         17 . The optical unit of  claim 12 , wherein the optical unit is configured so that during operation of the optical unit:
 the pupil plane has first and second main coordinates;   the object field has first and second main coordinates;   the first main coordinate of the object field is perpendicular to an illumination plane of incidence of the oblique illumination;   the second main coordinate of the object field is in the illumination plane of incidence of the oblique illumination;   the first main coordinate of the pupil plane corresponds to the first main coordinate of the object field;   the second main coordinate of the pupil plane corresponds to the second main coordinate of the object field; and   the illumination pupil is non-mirror asymmetric with respect to at least coordinate selected from the group consisting of the first main coordinate of the object field and the second main coordinate of the object field.   
     
     
         18 . An optical system, comprising:
 an optical unit according to  claim 12 ; and   a projection optical unit configured to image an object field into an image field,   wherein the illumination field of the optical unit coincides with the object field of the projection optical unit.   
     
     
         19 . The optical system of  claim 18 , further comprising an EUV light source. 
     
     
         20 . The optical system of  claim 18 , wherein the projection optical unit comprises a wavefront manipulator. 
     
     
         21 . The optical system of  claim 18 , wherein the optical unit is configured so that, during operation of the optical unit, the illumination pupil has a ring shaped ring pupil contribution and a compensation pupil contribution within the ring of the ring pupil contribution. 
     
     
         22 . The optical system of  claim 18 , wherein the optical unit is configured so that, during operation of the optical unit, the illumination pupil has a dipole pupil contribution and a compensation pupil contribution outside dipoles of the dipole pupil contribution. 
     
     
         23 . A method, comprising:
 providing an optical system according to  claim 12 ;   determining the object imaging variable which is dependent on the object structure variable of the object; and   predefining a compensation imaging parameter so that a structure dependent total imaging variable results,   wherein the total imaging variable lies within a predefined tolerance range of imaging variable values.   
     
     
         24 . A method of using an apparatus comprising an illumination optical unit and a projection optical unit, the method comprising:
 using the illumination optical unit to illuminate at least some structures of a reticle present in an object field or the projection optical unit; and   using the projection optical unit to project at least some of the illuminated structures of the reticle onto a light-sensitive material in an image field of the projection optical unit,   wherein the illumination optical unit is an optical unit according to  claim 12 .   
     
     
         25 . An apparatus, comprising:
 an illumination optical unit configured so that, during use of the illumination optical system, the illumination optical unit obliquely illuminates an illumination field; and   an imaging catoptric optical unit configured so that, during use of the imaging catoptric optical unit, the imaging catoptric optical unit images an object in an object field into an image field,   wherein:
 the object field of the imaging catoptric optical unit coincides with the illumination field of the illumination optical unit; 
 the imaging catoptric optical unit comprises a wavefront manipulation device configured so that, during use of the imaging catoptric optical unit, the wavefront manipulation device provides a wavefront of the imaging optical unit which brings about a dependency of an imaging focus shift on a structure variable of an object in the illumination field to at least partly compensate a dependency of the imaging focus shift on the structure variable; and 
 the optical unit is an EUV projection lithography illumination optical unit. 
   
     
     
         26 . The apparatus of  claim 25 , wherein the optical unit is configured so that, during operation of the optical unit, the illumination pupil has a ring shaped ring pupil contribution and a compensation pupil contribution within the ring of the ring pupil contribution. 
     
     
         27 . The apparatus of  claim 25 , wherein the optical unit is configured so that, during operation of the optical unit, the illumination pupil has a dipole pupil contribution and a compensation pupil contribution outside dipoles of the dipole pupil contribution. 
     
     
         28 . The apparatus of  claim 25 , wherein the optical unit is configured so that during operation of the optical unit:
 the pupil plane has first and second main coordinates;   the object field has first and second main coordinates;   the first main coordinate of the object field is perpendicular to the illumination plane;   the second main coordinate of the object field is in the illumination plane;   the first main coordinate of the pupil plane corresponds to the first main coordinate of the object field;   the second main coordinate of the pupil plane corresponds to the second main coordinate of the object field; and   the illumination pupil is non-mirror asymmetric with respect to at least coordinate selected from the group consisting of the first main coordinate of the object field and the second main coordinate of the object field.   
     
     
         29 . The apparatus of  claim 25 , further comprising an EUV light source. 
     
     
         30 . A method, comprising:
 providing an apparatus according to  claim 25 ;   determining an object imaging variable which is dependent on an object structure variable of the object; and   predefining a compensation imaging parameter so that a structure dependent total imaging variable results,   wherein the total imaging variable lies within a predefined tolerance range of imaging variable values.   
     
     
         31 . A method of using an apparatus comprising an illumination optical unit and a projection optical unit, the method comprising:
 using the illumination optical unit to illuminate at least some structures of a reticle present in an object field or the projection optical unit; and   using the projection optical unit to project at least some of the illuminated structures of the reticle onto a light-sensitive material in an image field of the projection optical unit,   wherein the apparatus is an apparatus according to  claim 25 .