Influence of Einzel lens structure on the performance of a microcolumn fabricated through MEMS technology

Microcolumn, a miniaturized electron optical system, is a powerful tool in manipulating electron beam for maskless direct e-beam lithography and miniaturized low voltage SEM for surface inspection, testing, and metrology. The basic parts of microcolumn are electron emitter, source lens, deflector, and Einzel lens. There are still several challenges in optimization of each component for better performance of microcolumn for aberration-free high quality imaging and large field of view. For the improvement of microcolumn, we developed a fabrication technique of making thin electrostatic lens using micro-electromechanical systems (MEMS) processes. Two types of microcolumns have been assembled by varying the spaces between Einzel lens-electrodes, and their performance have been evaluated for the comparison. The scan range is found to be increased with reducing the gap between the lenses and increasing working distance. The effect of the spatial gap on the scan range and image is analyzed through simulation study on the electric potential and field strength.