Beam detector, multi-charged-particle-beam irradiation apparatus, and adjustment method for beam detector
In one embodiment, a beam detector includes a first aperture plate including a first passage hole, a second aperture plate including a second passage hole that allows a single detection target beam passing through the first passage hole to pass therethrough, and a sensor detecting a beam current of the detection target beam passing through the second passage hole. The second aperture plate includes an electrically conductive material, a plurality of third passage holes are formed around the second passage hole, and the plurality of third passage holes allow light to pass therethrough.
1 . A beam-detector adjustment method comprising: applying observation light emitted from a light source to a first aperture plate through a second passage hole of a second aperture plate and a plurality of third passage holes around the second passage hole, the first aperture plate having a first passage hole being smaller than a beam pitch of multiple charged particle beams, the second passage hole allowing a single detection target beam of the multiple charged particle beams to pass therethrough, focusing an objective lens on the first aperture plate, observing an image formed by reflected light incident on an image sensor through the objective lens with the image sensor, and setting an image location of the first passage hole to a reference mark; and focusing the objective lens on the second aperture plate, observing an image formed by reflected light incident on the image sensor through the objective lens with the image sensor, and moving the second aperture plate to cause an image location of the second passage hole to coincide with the reference mark.
2 . The beam-detector adjustment method according to claim 1 , wherein the observation light emitted from the light source is blocked by a portion of the second aperture plate that is other than the second passage hole and the plurality of third passage holes without being transmitted through the portion.