Matching pupil determination

Abstract

A method for reducing apparatus performance variation. The method includes obtaining (i) a reference performance (e.g., CD) of a reference apparatus (e.g, a reference scanner), (ii) a set of initial leading degrees of freedom selected from a plurality of degrees of freedom of a plurality of pupil facet mirrors of an apparatus (e.g., to be matched scanner) that is selected to reproduce the reference performance, and (iii) exposure data related to one or more parameters (e.g., CD, overlay, focus, etc.) of the patterning process indicating a performance of the apparatus based on the set of initial leading degrees of freedom; and determining a matching pupil of the apparatus based on the set of initial leading degrees of freedom and the exposure data such that the matching pupil reduces a difference between the performance of the apparatus and the reference performance.

1 .- 14 . (canceled) 
     
     
         15 . A method comprising:
 obtaining (i) a reference performance, and (ii) a pupil measurement of a mirror of a plurality of pupil facet mirrors of an apparatus at a substrate level;   determining, by a computer system, imaging data based on the pupil measurement and a performance based on the imaging data; and   determining, by the computer system, a pupil of the apparatus such that the pupil reduces a difference between the performance of the apparatus and the reference performance.   
     
     
         16 . The method of  claim 15 , wherein the determining of the pupil is an iterative process, an iteration comprising:
 changing one or more degrees of freedom of the plurality of pupil facet mirrors;   computing, via modeling and/or simulation and based on the changed one or more degrees of freedom of the plurality of pupil facet mirrors, a current performance; and   determining a current difference between the current performance and the reference performance.   
     
     
         17 . The method of  claim 16 , wherein the changing one or more degrees of freedom include a change in orientation and/or intensity of one or more mirrors of the plurality of pupil facet mirrors. 
     
     
         18 . The method of  claim 15 , wherein the pupil measurement includes intensity and/or orientation of one or more mirrors of the plurality of pupil facet mirrors. 
     
     
         19 . The method of  claim 15 , wherein the reference performance is obtained from reference imaging data for a reference apparatus, the reference apparatus being different from the apparatus. 
     
     
         20 . The method of  claim 15 , wherein the reference performance is obtained from reference imaging data for the apparatus determined at a particular time of the patterning process. 
     
     
         21 . The method of  claim 15 , wherein the reference performance is generated from superimposition of aerial images of each mirror of the plurality of pupil facet mirrors. 
     
     
         22 . The method of  claim 21 , wherein the aerial images are generated, by modeling and/or simulation, for a far field location at a substrate level. 
     
     
         23 . The method of  claim 15 , wherein the imaging data is generated by superimposing aerial images of each mirror of a plurality of the pupil facet mirrors, each aerial image computed based on a respective intensity measurement of each such mirror. 
     
     
         24 . The method of  claim 15 , wherein the performance of the apparatus and the reference performance are related to a parameter of the patterning process including critical dimension and/or overlay. 
     
     
         25 . The method of  claim 15 , wherein the determined pupil minimizes the difference between the performance of the apparatus and the reference performance. 
     
     
         26 . The method of  claim 15 , further comprising adjusting performance of the apparatus based on the determined pupil. 
     
     
         27 . The method of  claim 26 , wherein the apparatus of the patterning process is a lithographic apparatus. 
     
     
         28 . A computer program product comprising a non-transitory computer-readable medium having instructions therein, the instructions, when executed by a computer system, configured to cause the computer system to at least:
 obtain (i) a reference performance, and (ii) a pupil measurement of a mirror of a plurality of pupil facet mirrors of an apparatus at a substrate level;   determine imaging data based on the pupil measurement and a performance based on the imaging data; and   determine a pupil of the apparatus such that the pupil reduces a difference between the performance of the apparatus and the reference performance.   
     
     
         29 . The computer program product of  claim 28 , wherein the instructions configured to determine the pupil operate in an iterative manner, an iteration comprising:
 change of one or more degrees of freedom of the plurality of pupil facet mirrors;   computation, via modeling and/or simulation and based on the changed one or more degrees of freedom of the plurality of pupil facet mirrors, of a current performance; and   determination of a current difference between the current performance and the reference performance.   
     
     
         30 . The computer program product of  claim 28 , wherein the pupil measurement includes intensity and/or orientation of one or more mirrors of the plurality of pupil facet mirrors. 
     
     
         31 . The computer program product of  claim 28 , wherein the reference performance is obtained from reference imaging data for a reference apparatus, the reference apparatus being different from the apparatus. 
     
     
         32 . The computer program product of  claim 28 , wherein the reference performance is obtained from reference imaging data for the apparatus determined at a particular time of the patterning process. 
     
     
         33 . The computer program product of  claim 28 , wherein the imaging data is generated by superimposing aerial images of each mirror of a plurality of the pupil facet mirrors, each aerial image computed based on a respective intensity measurement of each such mirror. 
     
     
         34 . The computer program product of  claim 28 , wherein the performance of the apparatus and the reference performance are related to a parameter of the patterning process including critical dimension and/or overlay.