Patent ID: 9136087
Filing Date: 2015-09-15
Classification: H01J

Abstract:
1. A method of investigating aberrations in a charged-particle lens system, the lens system having an object space comprising an object plane and an image space comprising an image plane, whereby an object placed on said object plane can be imaged by the lens system onto said image plane, the lens system further having an entrance pupil, the method comprising: selecting a fixed pivot point on said object plane; directing a charged-particle beam through said pivot point, entrance pupil and lens system and onto said image plane, said beam having a cross-sectional area of about 30% or less of the area of the entrance pupil; changing the orientation of said beam through said pivot point, so as to trace out an entrance figure on said entrance pupil and a corresponding image figure on said image plane; registering said image figure; repeating this procedure at a series of different focus settings of the lens system, thus acquiring a set of registered image figures at different focus settings; and analyzing said set so as to derive lens aberrations therefrom.