Optimization of microcolumn electron optics for high-current applications

The optimization of electron-optical properties of a microcolumn for high-c urrent, high-resolution applications in microcolumn arrays is discussed. Th e goal of the optimization is to increase the current available in the micr ocolumn to approximately 10-50 nA while maintaining a spot size sufficientl y 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 singl e-lens and two-lens microcolumn operational modes is compared at 1 keV beam energy, angular intensity of 100 muA/sr, and a working distance of 1 mm. T he two-lens mode can achieve spot sizes from 25 to 50 nm for a wide range o f beam currents, up to 50 nA. A two-lens microcolumn has been built and eva luated, and the experimental data is presented. (C) 2000 American Vacuum So ciety. [S0734-211X(00)14606-2].