On the limits of miniature electron column technology

Abstract

Miniature columns or microcolumns are a relatively new class of electron beam columns fabricated entirely from silicon using advanced micromachining processes. The main characteristics of these columns are thermal field emission (TFE) sources, low voltage operation (typically <3keV), simple design (two lenses, no crossover), microfabricated lenses, and all electrostatic components. Current production versions of miniature columns achieve <10nm resolution at 1keV, and have demonstrated <6nm resolution at higher beam energies.^1,2 While this performance is suitable for most applications, previous studies of the electron optics of miniature electrostatic lenses show better performance should be attainable under “ideal” conditions.³In practice, achieving these conditions is challenging because, in addition to the manufacturing errors from the miniature optics, other subsystems can impose additional constraints. An understanding of the major contributors to column performance, whether optical or mechanical, is essential, and can provide a roadmap for further improvements in the existing technology.