An all-electrostatic small beam diameter, high probe current field emission electron probe

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Abstract
An all-electrostatic probe forming system is described. It is based on a two-element lens of the type described by Munro (1975), followed by an eight-pole electrostatic stigmator/deflector. The system can be used in a high resolution SEM with a probe current of the order of 5*10-9 A into a spot diameter of approximately 40 nm or as a high current probe (>10-7 A) into a spot diameter of less than 300 nm. The column has a long working distance, 55 mm, and two focus conditions: one at primary energies in the range 0.4-0.8 keV, the other at energies in the range 14-17 keV. Techniques for improved emission stability and extended operational life of the emitter (>3000 h) are discussed.