Patent ID: 11914283
Assignee: AGC INC.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A reflective mask blank comprising a substrate and, on or above the substrate in order, a reflective layer for reflecting EUV light, a protective layer for protecting the reflective layer, and an absorbent layer for absorbing EUV light,
wherein the absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10%, and
a film thickness d of the absorbent layer satisfies a relationship of, [
  
   Math
   .
     
   1
  
  ]
 

 
  
   
    d
    
     M
     ⁢
     A
     ⁢
     X
    
   
   -
   
    
     (
     
      
       i
       ×
       6
      
      +
      1
     
     )
    
    ⁢
      
    nm
   
  
  ≤
  d
  ≤
  
   
    d
    
     M
     ⁢
     A
     ⁢
     X
    
   
   -
   
    
     (
     
      
       i
       ×
       6
      
       
      -
      1
     
     )
    
    ⁢
      
    nm
   
  
 

wherein the integer i is 0 or 1, and dMAX is represented by:, d
    
     M
     ⁢
     A
     ⁢
     X
    
   
   (
    
   nm
   )
  
  =
  
   
    13.53
    
     2
     ⁢
     n
     ⁢
       
     cos
     ⁢
     6
     ⁢
     °
    
   
   
    {
    
     
      INT
      ⁡
      (
      
       0.58
       
        1
        -
        n
       
      
      )
     
     +
     
      
       1
       
        2
        ⁢
        π
       
      
      ⁢
      
       (
       
        
         
          
           tan
            
          
          
           -
           1
          
         
         ⁢
         
          (
          
           
            -
            k
           
           
            1
            -
            n
           
          
          )
         
        
        +
        0.64
       
       )
      
     
    
    }
   
  
 

wherein n is a refractive index of the absorbent layer, k is an absorption coefficient of the absorbent layer, and INT(x) is a function of returning an integer value obtained by truncating a decimal part.