| 摘要 |
PURPOSE:To reduce the wear of a mask due to beam irradiation, by eliminating back ground level from a signal obtained by detecting a reflected beam, and finding a mark position on the basis of the signal in which noise component is eliminated and smoothing is done. CONSTITUTION:Charged particle beam Bi is radiated on a mask 4, generated reflection beam is received, and a signal including back ground level and noise component is output from a beam detector 5. A signal waveform resulting from elimination of the unnecessary ground component independent of the signal component can be obtained by a subtractor 6. Then the output of the subtractor 6 is input to a filter 9, and the elimination of noise and the smoothing of waveform are performed. After a trial function which best approximates a signal to the signal subjected to smoothing is obtained by a fitting circuit 10, center coodinates of the trial function are calculated by the next peak center determination circuit 11. Thus a very accurate trial function can be determined, so that a mark position is accurately obtained. Further the number of times of averaging by integrating can be extermely reduced. |
