公开(公告)号：US20230101108A1

公开(公告)日：2023-03-30

申请号：US17490522

申请日：2021-09-30

Applicant: FEI Company

Inventor： Ali MOHAMMADI-GHEIDARI ,  Peter Christiaan TIEMEIJER ,  Alexander HENSTRA ,  Tomas RADLICKA

IPC: H01J37/153 ,  H01J37/28 ,  H01J37/145 ,  H01J37/147

Abstract: An electron optical module for providing an off-axial electron beam with a tunable coma, according to the present disclosure includes a structure positioned downstream of an electron source and an electron lens assembly positioned between the structure and the electron source. The structure generates a decelerating electric field, and is positioned to prevent the passage of electrons along the optical axis of the electron lens assembly. The electron optical module further includes a micro-lens that is not positioned on the optical axis of the electron lens assembly and is configured to apply a lensing effect to an off-axial election beam. Aberrations applied to the off-axial electron beam by the micro-lens and the electron lens assembly combine so that a coma of the off-axial beam has a desired value in a downstream plane.