Electron microscope with particle optics corrector and corrector without 6th order axial aberration

摘要

PROBLEM TO BE SOLVED: To provide an electron microscope provided with a corrector having no sixth-order axial aberration. A corrector 5 has a central multi-pole element 2 having a length L that generates a 6-fold pole field ΨHP2 on a plane of symmetry 6, and a length L that generates 6-pole fields ΨHP1 and ΨHP3 having the same strength. It has two outer multipole elements 1, 3 of the same'and two circular lens doublets 7, 8 with circular lenses 7', 7'', 8', 8', and a central multipole 2 The strength of the 6-fold pole field of each of the outer multipoles 1 and 3 and the length of the pole, and the entire corrector 5 are astigmatism A2 on the 3rd axis, astigmatism A5 on the 6th axis, and 4th order. The on-axis three-lobe aberration (D4) and the sixth-order on-axis three-lobe aberration (D6) are selected to disappear. [Selection diagram] Fig. 1