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6.4.3 

6 - 63 

(4) Baseline 

Detection 

 

The baseline is a straight line having no slope, which is determined by the peak position 
attained before, the "baseline start point" and "baseline area".     
The start point of the baseline is located outside or inside the peak position, and it 
corresponds to a position of data having differential coefficient "dbase" in the following 
expression of profile differentiation.   

 

d

base

 =         .............................................................. (6.4.4) 

 

d

peak 

:  Differentiation coefficient of peak position   

B 

:  Baseline start point (1, 2, 4, 8)   

 

To determine the baseline, averaging is performed on a profile area included in a range 
specified with "baseline area".    For the "baseline start point", it is allowed to enter any one 
of 1, 2, 4 and 8.   

 
(5) Length 

Detection 

 

For length detection, an intersecting point of slope line and baseline is determined.     
Then an actual pattern dimension is calculated using the intersecting point data, 
magnification and correction coefficient.   

 
 
6.4.3.3  Threshold Level Method  
 
Described next is the threshold level algorithm.    In the same manner as for the linear 
approximation method, a smoothed profile "s (n)" is obtained.    Maximum and minimum values 
of the profile are determined in the edge detection area.    Then an intersecting point with "Th" 
given by the following expression is defined as the edge position.   
 

Th =                     

× T + s

min

.............................................. (6.4.5) 

 

s

max 

:  Max. value of profile in the vicinity of edge 

s

min 

:  Min. value of profile in the vicinity of edge 

T : Threshold 

(%) 

 
 

d

peak 

|B| 

s

max

 - s

min 

100