Imaging system for charged particles

Details Imaging system for charged particles Imaging system for charged particles

1992-09-04

1994-06-07

Berman, Jack I.

Radiant energy

With charged particle beam deflection or focussing

Magnetic lens

250311, H01J 37147, H01J 3729

Patent

active

053192079

ABSTRACT:
The invention relates to an imaging system for charged particles having a correction unit for correcting an objective lens. The correction unit essentially includes a beam deflector and a mirror which reflects the incoming particle beam. A first symmetry plane of the deflector is imaged in the mirror. The mirror images this first symmetry plane at an imaging scale of 1:1 in a second symmetry plane of the deflector. At the same time, the symmetry planes are either intermediate image planes or diffraction planes. With the high symmetry of the imaging system, the condition is achieved that the aberrations of the second order caused by a one-time passthrough through the deflector are cancelled after the second passthrough. The mirror can be so adjusted that its negative chromatic aberration compensates for the chromatic aberration of the objective lens and the other lenses. The spherical aberration can be compensated independently thereof with the aid of a hexapole which is centered in a diffraction plane.

REFERENCES:
patent: 4740704 (1988-04-01), Rose et al.
"Closed packed prism arrays for electron microscopy" by V. Kolarik et al, Optik, vol. 87, No. 1, 1991, pp. 1 to 12.
"Properties of a four-electrode adjustable electron mirror as an aberration corrector" by Zhifeng Shao et al, Review of Scientific Instruments, vol. 61, No. 4, 1990, pp. 1230 to 1235.
"Etude des aberrations du second ordre du microanalyseuur Ionique et de quelques autres systemes destines au filtrage d'images etendues" by M. Leleyter et al., Revue de Physique Applique, vol. 6, 1971, pp. 65 to 89.
"A theoretical Study of the hyperbolic electron mirror as a correcting element for spherical and chromatic aberration in electron optics" by G. F. Rempfer, Journal Applied Physics, vol. 67, No. 10, May 1990.
"Outline of a spherically corrected semiaplanatic medium-voltage transmission electron microscope" by H. Rose, Optik, vol. 85, No. 1 (1990).

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