Annular Focused Electron/Ion Beams for Combining High Spatial Resolution with High Probe Current.
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.
Department of Electrical and Computer Engineering,National University of Singapore,4 Engineering Drive 3,Singapore 117576,Singapore.
Anjam
0000-0002-7905-4081
A
Khursheed
Department of Electrical and Computer Engineering,National University of Singapore,4 Engineering Drive 3,Singapore 117576,Singapore.
Wei Kean
WK
Ang
aberration correction; annular focused electron/ion beams; core lenses; focused electron/ion beam columns; objective lens