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Proceedings Paper

Electrostatic aberration correction in low-voltage SEM
Author(s): Diederik J. Maas; Sander Henstra; Marcel Krijn; Sjoerd Mentink
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Paper Abstract

The resolution of a low-voltage scanning electron microscope is limited by the chromatic and spherical aberration of the objective lens. Any significant improvement of the resolution requires an aberration corrector or monochromator. Recently, correction of both Cc and Cs has been demonstrated in a SEM, using a combination of magnetic and electrostatic quadruples and octuples. This paper presents an alternative and purely electrostatic design which, like most quadrupole-octuple correctors, is based on the concept of creating a stigmatic path and correcting Cc in the two line foci. We propose a combination of strongly oscillating mono- and quadruple fields as dispersive elements. Our arrangement of the mono- and quadruple fields creates a thick non-focusing correcting elements, which corrects for Cc in one plane, while these fields act as a telescope (with magnification M=+/- 1) in the other plane. The telescopic properties of the correcting element in both planes reduce the chromatic magnification aberration of the corrector to acceptable proportions. To model our corrector realistically, the electrostatic potential has been computed for a 3D electron geometry with the EO-3D package from MEBS. From this the electrostatic potential has been computed for a 3D electrode geometry with the EO-3D package from MEBS. From this potential we extracted axial field functions for the monopole up to octuple fields. Ray tracing with these axial fields using MEBS's MULTIPOL package yields all aberrations up to fifth order. The numerical calculations show a resolution enhancement by a factor of 2 with a Cc and Cs corrector that is based on our novel correcting elements.

Paper Details

Date Published: 21 December 2001
PDF: 13 pages
Proc. SPIE 4510, Charged Particle Detection, Diagnostics, and Imaging, (21 December 2001); doi: 10.1117/12.451283
Show Author Affiliations
Diederik J. Maas, Philips Research Labs. (Netherlands)
Sander Henstra, FEI Co. (Netherlands)
Marcel Krijn, Philips Research Labs. (Netherlands)
Sjoerd Mentink, Philips Research Labs. (Netherlands)


Published in SPIE Proceedings Vol. 4510:
Charged Particle Detection, Diagnostics, and Imaging
Eric Munro; John A. Rouse, Editor(s)

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