Patent ID: 7781742

Claim:
A corrector for chromatic and aperture aberration correction in a scanning electron microscope or a scanning transmission electron microscope, the corrector comprising: a first multipole element generating a quadrupole field; a second multipole element disposed downstream of said first multipole element, said second multipole element generating quadrupole, octupole, and twelve pole fields for correcting aberrations of higher order, said quadrupole fields of said second multipole element comprising superposed magnetic and electric fields; a third multipole element disposed downstream of said second multipole element, said third multipole element generating quadrupole, octupole, and twelve pole fields for correcting aberrations of higher order, said quadrupole fields of said third multipole element comprising superposed magnetic and electric fields; a fourth multipole element disposed downstream of said third multipole element, said fourth multipole element generating a quadrupole field; and an additional twelve-pole element disposed between said second and said third multipole elements and supplied with current and/or voltage such that an octupole field is generated that is superposed by a twelve-pole field, wherein said first, second, third, and fourth multipole elements are consecutively disposed in an optical path, quadrupole fields of said first, second, third, and fourth multipole elements being consecutively rotated with respect to one another through 90° to facilitate chromatic aberration correction through interaction between magnetic and electric fields thereof using astigmatic intermediate images in said second and said third multipole elements, wherein aperture aberration correction is effected via quadruple and octupole fields, said additional twelve-pole element being arranged in such a fashion that said octupole and twelve-pole fields thereof are disposed between astigmatic intermediate images at which a beam cross section is round.