| 摘要 |
PROBLEM TO BE SOLVED: To automatically determine whether or not auto-focus results are good.SOLUTION: Preliminary imaging is performed, wherein scan lines in a specific region of a shooting region of a sample are scanned with a charged particle beam while sequentially changing a focus point to obtain a preliminary image signal, and then a scan line having the maximum sharpness in the preliminary image signal is determined. Then, regular imaging of the shooting region of the sample is performed under a focusing state of a focusing means to obtain an auto-focus image. Whether or not the auto-focus image is good is determined by obtaining an image signal profile Fa(t) of the scan line at the maximum sharpness position in the preliminary imaging (step ST1), obtaining an image signal profile Fb(t) of a scan line in the regular imaging corresponding to the scan line having the maximum sharpness in the preliminary imaging (step ST2), comparing a degree of similarity S(t) calculated from the image signal profiles Fa(t) and Fb(t) with a threshold value T1 (step ST4), and then comparing a deviation ΔT of a value T at which the similarity S(t) has a maximum value with a threshold value T2 (step ST5). |
