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Electrostatic Aberration Correction in LV-SEM

Published online by Cambridge University Press:  02 July 2020

D.J. Maas
Affiliation:
Philips Research, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands
A. Henstra
Affiliation:
FEI Electron Optics, PO Box 218, 5600 MD Eindhoven, The Netherlands
M.P.C.M. Krijn
Affiliation:
Philips Research, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands
S.A.M. Mentink
Affiliation:
Philips Research, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands
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Extract

The resolution of a low-voltage electron microscope is limited by the chromatic and spherical aberration of the objective lens, see Fig. 1. The design of state-of-the-art objective lenses is optimised for minimal aberrations. Any significant improvement of the resolution requires an aberration corrector. Recently, correction of both Cc and Cs has been demonstrated in SEM, using a combination of magnetic and electrostatic quadrupoles and octupoles (Zach and Haider, 1995). The present paper presents an alternative design, which is based on a purely electrostatic concept, potentially simplifying the ease-of-use of an aberration corrected microscope.

In 1936 Scherzer showed that the fundamental lens aberrations of round lenses are positive definite, in absence of time-varying fields and/or space charge. Negative lens aberrations, required for the correction of Cc and Cs, can only be obtained using non-round lenses, e.g. quadrupoles and octupoles (Scherzer, 1947).

Type
Low Voltage Scanning Electron Microscopy and X-Ray Microanalysis
Copyright
Copyright © Microscopy Society of America

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References

References:

1.Scherzer, O., Z. Phys. 101 (1936) 593603CrossRefGoogle Scholar
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7. This research was supported by the Ministry of Economic Affairs of the Dutch national government under the metrology platform of MEDEA Project No. T618.Google Scholar