Optimization of microcolumn electron optics for high-current applications

The optimization of electron-optical properties of a microcolumn for high-current, high-resolution applications in microcolumn arrays is discussed. The goal of the optimization is to increase the current available in the microcolumn to approximately 10–50 nA while maintaining a spot size sufficiently small for sub-100 nm technology (not larger than approximately 20–50 nm). To achieve this goal, it is necessary to operate the microcolumn as a two-lens electron-optical system. The electron-optical performance of the single-lens and two-lens microcolumn operational modes is compared at 1 keV beam energy, angular intensity of 100 μA/sr, and a working distance of 1 mm. The two-lens mode can achieve spot sizes from 25 to 50 nm for a wide range of beam currents, up to 50 nA. A two-lens microcolumn has been built and evaluated, and the experimental data is presented.