Method for operating an illumination system of a microlithographic projection exposure apparatus

Abstract

A method of operating an illumination system of a microlithographic projection exposure apparatus is provided. A set of illumination parameters that describe properties of a light bundle which converges at a point on a mask to be illuminated by the illumination system is first determined. Optical elements whose optical effect on the illumination parameters can be modified as a function of control commands are furthermore determined, as well as sensitivities with which the illumination parameters react to an adjustment of the optical elements, induced by the control commands. The control commands are then determined while taking the previously determined sensitivities into account, such that deviations of the illumination parameters from predetermined target illumination parameters satisfy a predetermined minimisation criterion. These control commands are applied to the optical elements, before the mask is illuminated.

1 . (canceled) 
     
     
         2 . A method of operating an illumination system of a microlithographic projection exposure apparatus, the illumination system comprising an optical element having an optical effect on an incident light bundle, the optical effect being modifiable based on a control command, the method comprising:
 a) determining a set of illumination parameters that describe properties of the light bundle, the illumination parameters being weighted via multiplication by weighting factors;   b) determining a sensitivity with which the illumination parameters react to an adjustment induced by the control command;   c) determining the control command, while taking into account the sensitivity determined in b), so that deviations of the illumination parameters from a target set of illumination parameters satisfy a predetermined minimization criterion;   d) applying the control command determined in c) to the optical element; and   e) illuminating a mask with the light bundle.   
     
     
         3 . The method of  claim 2 , wherein, during operation of the microlithographic projection exposure apparatus, the light bundle converges at a point on the mask. 
     
     
         4 . The method of  claim 3 , wherein the properties of the light bundle comprise an intensity distribution of the light bundle at an exit pupil associated with the point on the mask. 
     
     
         5 . The method of  claim 4 , further comprising determining differences between the intensity distribution and a target intensity distribution. 
     
     
         6 . The method of  claim 5 , wherein the differences are characterized by an intensity modulation and a distortion. 
     
     
         7 . The method of  claim 3 , wherein the weighting factors depend on a general mask type or on the mask to be illuminated. 
     
     
         8 . The method of  claim 3 , wherein the weighting factors are determined while taking into account imaging properties of a projection objective which images the mask. 
     
     
         9 . The method of  claim 3 , further comprising determining the control command in c) via an iterative method that comprises modifying the control command until measurements reveal that the deviations of the illumination parameters from the target set of illumination parameters satisfy the predetermined minimization criterion. 
     
     
         10 . The method of  claim 3 , further comprising using simulations to determine the sensitivity in b). 
     
     
         11 . The method of  claim 3 , further comprising using measurements to determine the sensitivity in b). 
     
     
         12 . The method of  claim 3 , wherein the optical element comprises an optical element selected from a group consisting of:
 a light source having a modifiable position relative to an optical axis of the illumination system;   a diffractive optical element having a modifiable spatial orientation with respect to the optical axis of the illumination system;   a zoom objective comprising lens which that is displaceable along the optical axis of the illumination system;   an axicon group comprising two axicon elements having modifiable spacing;   a transmission filter in or in a vicinity of a pupil surface of the illumination system;   a transmission filter in or in a vicinity of a field plane of the illumination system;   a transmission filter between a pupil surface and a field plane of the illumination system; and   a variable-position lens in a condenser of the illumination system, by which ray bundles coming from secondary light sources are superimposed in a field plane.   
     
     
         13 . The method of  claim 3 , further comprising determining the illumination parameters in a) so that they are input quantities of a simulation program with which it is possible to calculate quantities that, for a particular mask, relate to the an arrangement and dimensions of structures which can be generated by imaging the mask on a support. 
     
     
         14 . The method according to  claim 2 , wherein the weighting factors depend on a general mask type or on the mask to be illuminated. 
     
     
         15 . The method according to  claim 2 , wherein the weighting factors are determined while taking into account imaging properties of a projection objective which images the mask. 
     
     
         16 . The method according to  claim 2 , further comprising determining the control command in c) via an iterative method that comprises modifying the control command until measurements reveal that the deviations of the illumination parameters from the target set of illumination parameters satisfy the predetermined minimization criterion. 
     
     
         17 . The method according to  claim 2 , further comprising using simulations to determine the sensitivity in b). 
     
     
         18 . The method according to  claim 2 , further comprising using measurements to determine the sensitivity in b). 
     
     
         19 . The method of  claim 2 , wherein the optical element comprises an optical element selected from a group consisting of:
 a light source having a modifiable position relative to an optical axis of the illumination system;   a diffractive optical element having a modifiable spatial orientation with respect to the optical axis of the illumination system;   a zoom objective comprising lens which that is displaceable along the optical axis of the illumination system;   an axicon group comprising two axicon elements having modifiable spacing;   a transmission filter in or in a vicinity of a pupil surface of the illumination system;   a transmission filter in or in a vicinity of a field plane of the illumination system;   a transmission filter between a pupil surface and a field plane of the illumination system; and   a variable-position lens in a condenser of the illumination system, by which ray bundles coming from secondary light sources are superimposed in a field plane.   
     
     
         20 . The method of  claim 2 , further comprising determining the illumination parameters in a) so that they are input quantities of a simulation program with which it is possible to calculate quantities that, for a particular mask, relate to the an arrangement and dimensions of structures which can be generated by imaging the mask on a support. 
     
     
         21 . The method of  claim 2 , further comprising:
 using the illumination parameters determined in a) as input quantities of a simulation program; and   using the simulation program to calculate quantities that, for a particular mask, relate to the an arrangement and dimensions of structures which can be generated by imaging the mask on a support.