METHODS OF DETERMINING ABERRATIONS OF A CHARGED PARTICLE BEAM, AND CHARGED PARTICLE BEAM SYSTEM

A method of determining aberrations of a charged particle beam (11) focused by a focusing lens (120) with a given numerical aperture (NA) toward a sample (10) in a charged particle beam system is described. The method includes: (a.) simulating, based at least on the given numerical aperture (NA), one or more beam cross sections at one or more first defocus settings for each of two or more different values of a first beam aberration coefficient (C1) of a set of beam aberration coefficients (C1 . . . n), to provide a plurality of first simulated beam cross sections; (b.) extracting two or more values of a first aberration characteristic (˜C1) that is related to the first beam aberration coefficient (C1) from the plurality of first simulated beam cross sections; (c.) determining a first dependency between the first beam aberration coefficient (C1) and the first aberration characteristic (˜C1); (d.) taking one or more images of the sample at the one or more first defocus settings or at one or more second defocus settings, to provide one or more taken images, and retrieving one or more retrieved beam cross sections from the one or more taken images; (e.) extracting a retrieved value of the first aberration characteristic from the one or more retrieved beam cross sections; and (f.) determining an actual value of the first beam aberration coefficient based on the first dependency and based on the retrieved value of the first aberration characteristic.