Enhanced uniqueness for pattern recognition

Abstract

The present invention describes a test structure with a first set of features which is a subset of product features; and a second set of features adjacent to the first set of features, the second set occupying a smaller area than the first set and the second set being similar to the first set yet being distinguishable from surrounding structures.

We claim:  
     
         1 . A structure comprising: 
 a first set of features disposed in the scribeline, said first set of features being a subset of product features; and    a second set of features disposed adjacent to said first set of features, said second set occupying a smaller area than said first set, said second set being similar to said first set, said second set being distinguishable from surrounding structures.    
     
     
         2 . The structure of  claim 1  wherein critical dimension (CD) is measured on said first set of features.  
     
     
         3 . The structure of  claim 1  wherein said first set of features and said second set of features differ in spaces between features.  
     
     
         4 . The structure of  claim 1  wherein said first set of features and said second set of features differ in linewidths of features.  
     
     
         5 . The structure of  claim 1  wherein said first set of features and said second set of features have the same pitch for features.  
     
     
         6 . The structure of  claim 1  wherein said first set of features comprises a first array of holes.  
     
     
         7 . The structure of  claim 6  wherein said first array of holes comprises a 5-by-5 square array of holes.  
     
     
         8 . The structure of  claim 6  wherein said second set of features comprises a second array of holes.  
     
     
         9 . The structure of  claim 8  wherein said second array of holes differs from said first array of holes in size of array.  
     
     
         10 . The structure of  claim 8  wherein said second array of holes differs from said first array of holes in space between holes.  
     
     
         11 . The structure of  claim 8  wherein said second array of holes differs from said first array of holes in linewidths of holes.  
     
     
         12 . A method comprising: 
 extracting a subset from product features to form a first set of features;    extracting a small portion from said first set of features to form a template;    transforming said template into a second set of features by 
 rotating said template;  
 scaling spaces between features in said template;  
 scaling linewidths of features in said template;  
   merging said first set and said second set of features to form a test structure.    
     
     
         13 . The method of  claim 12  wherein critical dimension (CD) is measured on said first set of features.  
     
     
         14 . A method comprising: 
 storing a reference image of a test structure, said reference image comprising a first set of features and a second set of features, 
 said first set of features being a subset of product features,  
 said second set of features disposed adjacent to said first set of features, said second set occupying a smaller area than said first set, said second set being similar to said first set, said second set being distinguishable from surrounding structures;  
   capturing a test image of a sample, said test image having a plurality of portions;    performing pattern recognition of each of said portions relative to said reference image;    evaluating similarity of each of said portions to said reference image;    determining a score for each of said portions;    ranking said portions from highest score to lowest score; and    determining location on said sample of said portion with highest score.    
     
     
         15 . The method of  claim 14  wherein said score depends on said first set of features and said second set of features.  
     
     
         16 . The method of  claim 14  wherein said first set of features comprises a first array of holes and said second set of features comprises a second array of holes, said second array of holes differing from said first array of holes.