| CPC H01J 37/244 (2013.01) [H01J 37/1475 (2013.01); H01J 37/28 (2013.01); H01J 2237/24455 (2013.01); H01J 2237/2448 (2013.01); H01J 2237/24521 (2013.01)] | 20 Claims |

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1. A charged particle beam apparatus comprising:
a charged particle source generating a charged particle beam;
a deflector deflecting the charged particle beam;
a detector detecting secondary electrons emitted from an irradiation target in response to irradiation with the charged particle beam; and
a processor system, wherein
the processor system
(A) acquires a first time-series change in secondary electron detection-related quantity by repeatedly performing the following (A1) and (A2),
(A1) directly or indirectly maintains or changes a control amount applied to the deflector to a first control amount, and
(A2) acquires the secondary electron detection-related quantity based on an output from the detector, and
(B) acquires a time-series change in variation of the beam diameter of the charged particle beam based on the first time-series change.
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