Patent ID: 11868054
Assignee: NOVA LTD.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 8:
9. A method for use in optical metrology measurements, the method comprising:
providing raw measured data indicative of measured spectral interferometric signals,
wherein a portion of the measured spectral interferometric signals has a signal intensity profile determined as, 2
   ⁢
   
    
     ❘
     "\[LeftBracketingBar]"
    
    
     
      E
      top
     
     (
     
      λ
      i
     
     )
    
    
     ❘
     "\[RightBracketingBar]"
    
   
   ⁢
   
    
     ❘
     "\[LeftBracketingBar]"
    
    
     
      E
      m
     
     (
     
      λ
      i
     
     )
    
    
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   ⁢
   cos
   ⁢
   
    (
    
     
      
       
        2
        ⁢
        π
       
       λ
      
      ⁢
      z
     
     +
     
      ϕ
      ⁡
      (
      
       λ
       i
      
      )
     
    
    )
   
  
  ,
 

wherein the measured spectral interferometric signals having a signal intensity profile determined as:, I
    ⁡
    (
    
     
      λ
      i
     
     ,
     z
    
    )
   
   =
   
    
     
      
       ❘
       "\[LeftBracketingBar]"
      
      
       
        E
        top
       
       (
       
        λ
        i
       
       )
      
      
       ❘
       "\[RightBracketingBar]"
      
     
     2
    
    +
    
     
      
       ❘
       "\[LeftBracketingBar]"
      
      
       
        E
        
         bot
         .
        
       
       (
       
        λ
        i
       
       )
      
      
       ❘
       "\[RightBracketingBar]"
      
     
     2
    
    +
    
     
      
       ❘
       "\[LeftBracketingBar]"
      
      
       
        E
        m
       
       (
       
        λ
        i
       
       )
      
      
       ❘
       "\[RightBracketingBar]"
      
     
     2
    
    +
    
     2
     ⁢
     
      
       ❘
       "\[LeftBracketingBar]"
      
      
       
        E
        top
       
       (
       
        λ
        i
       
       )
      
      
       ❘
       "\[RightBracketingBar]"
      
     
     ⁢
     
      
       ❘
       "\[LeftBracketingBar]"
      
      
       
        E
        m
       
       (
       
        λ
        i
       
       )
      
      
       ❘
       "\[RightBracketingBar]"
      
     
     ⁢
     cos
     ⁢
     
      (
      
       
        
         
          2
          ⁢
          π
         
         λ
        
        ⁢
        z
       
       +
       
        ϕ
        ⁡
        (
        
         λ
         i
        
        )
       
      
      )
     
    
   
  
  ;, wherein: Etop (λi) is a spectral amplitude of the electromagnetic field reflection from the top portion; Ebot. (λi) is a spectral amplitude of the electromagnetic field reflection from the bottom portion of the sample; Em(λi) is an electromagnetic field reflection from an interferometric mirror; λi is a wavelength of the illuminating electromagnetic field; z is a position of the interferometric minor; and ϕ(λi) is the spectral phase of the measured spectral interferometric signal; and
processing said raw measured data, said processing comprising:
extracting, from the raw measured data, the portion of the measured spectral interferometric signals, the portion of the measured spectral interferometric signals describing variation of a signal intensity with a change of an optical path difference during interferometric measurements, the portion of the measured spectral interferometric signals being independent of interferometric signals returned from a bottom portion of the sample in response to said illuminating electromagnetic field; and
determining, from the portion of the measured spectral interferometric signals, both spectral amplitude and phase of reflection of the illuminating electromagnetic field from the top portion of the sample, thereby determining a measured spectral signature characterizing the top portion of the sample;
wherein the measured spectral interferometric signals returned from the sample in response to illuminating electromagnetic field incident onto a top portion of the sample, the illuminating electromagnetic field comprises at least one spectral range to which said sample is substantially not absorbing on the top portion to be detected, thereby, presenting a parasitic signal that is separated from the top surface reflection.