| 摘要 |
PURPOSE:To make it possible to obtain an accurate focussing in the case of astigmatism and insufficient information from a sample by collecting information generated on the sample based on the condition of a constant focussing lense current and performing the collection in the integer period or the integer times period of 1/2 period of a circular scanning. CONSTITUTION:A circular scanning is performed while the current value Iobj of a focussing lense 11 is changed in steps and secondary electron beams, reflection electron beams or the like generated on a sample 1 are detected by radiating electron beams 20 at the integer period or the integer times period of 1/2 period of the circular scanning, in the period when the current value Iobj is not changed. The information such as the total or average of the absolute value of the differential value in the detected signals is calculated and stored. The current value Iobj of the focussing lense capable of radiating electron beams 20 on the sample 1 in the state of the minimum blur circle is obtained based on the comparison of the information. Therefore, it is possible to obtain the focussing device of an electron beam device which is effective even to a sample having insufficient information without the effect of astigmatism.
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