Patent ID: 11953448
Assignee: TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method for defect inspection, comprising:
receiving photomask having a surface and a plurality of patterns disposed on the surface;
obtaining a gray scale image of the photomask, using a scanner of a lithography system, wherein the gray scale image comprises a plurality of regions, and each of the regions has a gray scale value;
comparing the gray scale value of each region to a gray scale reference, using a computing system of the lithography system, to define a first group, a second group and an Nth group, wherein each of the first group, the second group and the Nth group has at least a region, and the region in the first group has a first difference between its gray scale value and the gray scale reference, the region in the second group has a second difference between its gray scale value and the gray scale reference, and the region in the Nth group has an Nth difference between its gray scale value and the gray scale reference;
performing a calculation according to the first difference, the second difference and the Nth difference to obtain a score in order to improve an inspection for an electrostatic discharge (ESD) defect by the computing system of the lithography system;
determining the photomask to have the ESD defect or to be free of the ESD defect according to the score obtained from the calculation, wherein the calculation is performed according to an equation (1):, Ws
     =
     
      
       
        ∑
        
         
          
           e
           1
          
          (
          G
          )
         
         
          G
          ⁢
          1
         
        
       
       +
       
        ∑
        
         
          
           e
           2
          
          (
          G
          )
         
         
          G
          ⁢
          2
         
        
       
       +
       
        ∑
        
         
          
           e
           3
          
          (
          G
          )
         
         
          G
          ⁢
          3
         
        
       
       +
       
        …
        ⁢
           
        
         ∑
         
          
           
            e
            n
           
           (
           G
           )
          
          
           G
           ⁢
           n
          
         
        
       
      
      
       ∑
       
        
         (
         G
         )
        
        
         
          G
          ⁢
          1
         
         ,
         
          G
          ⁢
          2
         
         ,
         G3
         ,
         
          …
          ⁢
          Gn
         
        
       
      
     
    
   
   
    
     (
     1
     )
    
   
  
 

wherein Ws is the score, G is an individual difference of a region in a first group G1, a second group G2, a third group G3 and a Nth group GN, and e1 is a first weighting factor, e2 is a second weighting factor, and en is an Nth weighting factor; and
performing an exposure operation using the photomask when the photomask is determined to be free of the ESD defect, or removing the photomask from the exposure operation when the photomask is determined to have the ESD defect.