Surface shape measuring apparatus

Abstract

In related art, consideration is not given to that a spatial distribution of scattered light changes in various direction such as forward/backward/sideways according to a difference in micro roughness. Particularly, although a step-terrace structure appearing on an epitaxial growth wafer produces anisotropy in the scattered light distribution, consideration is not given to this point in the related art. The invention includes a process in which light is illuminated to a sample surface, plural detection optical systems mutually different in directions of optical axes detect a spatial distribution of scattered light, and a spatial frequency spectrum of the sample surface is calculated.

1 . A signal processing apparatus comprising
 A memory which stores library;   A digital signal processor which obtains a continuous spatial frequency spectrum of micro roughness of a sample by using the library, and detection signals of plurality of detectors for detecting scattered light from the sample.   
     
     
         2 . The signal processing apparatus according to  claim 1 , wherein the library records a relation between a spatial frequency spectrum of a surface shape and an optical detection signal with respect to an already-known micro roughness. 
     
     
         3 . The signal processing apparatus according to  claim 2 , wherein the digital signal processor obtains a ratio of a sum of the detection signals, and one detection signal and obtains the spatial frequency spectrum by using the ratio and the library. 
     
     
         4 . The signal processing apparatus according to  claim 3 , wherein the digital processor obtains at least one of a surface roughness in a spatial frequency region in the spatial frequency spectrum of the micro roughness, a cut-off spatial frequency of the spatial frequency spectrum of the micro roughness, and a peak spatial frequency. 
     
     
         5 . The signal processing apparatus according to  claim 4 , wherein the digital processor performs a Fourier inverse transform of the spatial frequency spectrum of the micro roughness. 
     
     
         6 . The signal processing apparatus according to  claim 5 , wherein the digital processor uses random number to perform the Fourier inverse transform. 
     
     
         7 . The signal processing apparatus according to  claim 6 , wherein the continuous spatial frequency spectrum is expressed by a plurality of parameters. 
     
     
         8 . The signal processing apparatus according to  claim 7 , wherein the continuous spatial frequency spectrum is ABC type function, wherein the A denotes power at low spatial frequency side, B denotes cut-off, C relates to inclination of spectrum. 
     
     
         9 . The signal processing apparatus according to  claim 1 , wherein the digital signal processor obtains a ratio of a sum of the detection signals, and one detection signal and obtains the spatial frequency spectrum by using the ratio and the library. 
     
     
         10 . The signal processing apparatus according to  claim 1 , wherein the digital processor obtains at least one of a surface roughness in a spatial frequency region in the spatial frequency spectrum of the micro roughness, a cut-off spatial frequency of the spatial frequency spectrum of the micro roughness, and a peak spatial frequency. 
     
     
         11 . The signal processing apparatus according to  claim 1 , wherein the digital processor performs a Fourier inverse transform of the spatial frequency spectrum of the micro roughness. 
     
     
         12 . The signal processing apparatus according to  claim 1 , wherein the digital processor uses random number to perform the Fourier inverse transform. 
     
     
         13 . The signal processing apparatus according to  claim 1 , wherein the continuous spatial frequency spectrum is expressed by a plurality of parameters. 
     
     
         14 . The signal processing apparatus according to  claim 13 , wherein the continuous spatial frequency spectrum is ABC type function, wherein the A denotes power at low spatial frequency side, B denotes cut-off, C relates to inclination of spectrum.