| CPC H01J 37/3476 (2013.01) [G01B 7/003 (2013.01); G01B 7/004 (2013.01); G01D 5/145 (2013.01); H01J 37/3435 (2013.01)] | 20 Claims |

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1. A method, comprising:
providing a jig having a recess and a predetermined center within the recess;
defining a first area of the jig around the predetermined center by outward expansion from the predetermined center in a first distance;
measuring a plurality of first depths of the jig within the first area of the jig by a probe;
deriving a maximum first depth among the plurality of first depths;
defining a second area of the jig around a first position of the jig having the maximum first depth of the jig by outward expansion from the first position in a second distance;
measuring a plurality of second depths of the jig within the second area of the jig by the probe;
deriving a maximum second depth among the plurality of second depths;
comparing the maximum second depth with the maximum first depth; and
performing an operation if the maximum first depth is substantially greater than or equal to the maximum second depth, wherein the operation includes defining the first position of the jig having the maximum first depth of the jig as an exact center of the jig.
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