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Annular Focused Electron/Ion Beams for Combining High Spatial Resolution with High Probe Current

Published online by Cambridge University Press:  09 September 2016

Anjam Khursheed Open the ORCID record for Anjam Khursheed [Opens in a new window]  and
Wei Kean Ang
Anjam Khursheed*
Affiliation:
Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Singapore
Wei Kean Ang
Affiliation:
Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Singapore
*
* Corresponding author. [email protected]
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Abstract

This paper presents a proposal for reducing the final probe size of focused electron/ion beam columns that are operated in a high primary beam current mode where relatively large final apertures are used, typically required in applications such as electron beam lithography, focused ion beams, and electron beam spectroscopy. An annular aperture together with a lens corrector unit is used to replace the conventional final hole-aperture, creating an annular ring-shaped primary beam. The corrector unit is designed to eliminate the first- and second-order geometric aberrations of the objective lens, and for the same probe current, the final geometric aberration limited spot size is predicted to be around a factor of 50 times smaller than that of the corresponding conventional hole-aperture beam. Direct ray tracing simulation is used to illustrate how a three-stage core lens corrector can be used to eliminate the first- and second-order geometric aberrations of an electric Einzel objective lens.

Keywords

annular focused electron/ion beamsaberration correctionfocused electron/ion beam columnscore lensesobjective lens
Type
Instrumentation and Techniques Development
Information
Microscopy and Microanalysis , Volume 22 , Issue 5 , October 2016 , pp. 948 - 954
Copyright
© Microscopy Society of America 2016 

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