Patent Number: 
Section: abstract

The present invention relates to a charged particle beam device (1) for inspecting or structuring a specimen (3) comprising a charged particle beam source (5) to generate a charged particle beam (7), a focussing lens (9) to focus the charged particle beam (7) onto the specimen (3), and an aperture system (13) for defining an aperture (6) for the charged particle beam (7). The aperture system (13) includes a first member (20) to block a first portion (7a) of the charged particle beam (7) between the charged particle beam source (5) and the focussing lens (9), a second member (30) to block a second portion (7b) of the charged particle beam (7) between the charged particle beam source (5) and the focussing lens (9), first means (24) for moving the first member (20) to adjust the size of the blocked first portion (7a) of the charged particle beam (7), and second means (34) for moving the second member (30) independently from the first portion (7b). With such aperture system (13), it is possible to freely adjust the size of the aperture (6) and align it to the optical axis (8) during operation.