E. Kratschmer et al., AN ELECTRON-BEAM MICROCOLUMN WITH IMPROVED RESOLUTION, BEAM CURRENT, AND STABILITY, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 13(6), 1995, pp. 2498-2503
We have built and tested a 1 keV electron-beam microcolumn that focuse
s 1 nA of beam current into a 10 nm full width half-maximum beam diame
ter at a working distance of 1 mm. The electron source is a miniaturiz
ed Zr/O/W Schottky field emitter with 150 mu A/sr angular emission cur
rent density operating at about 1800 K at a distance of only 100 mu m
from a silicon membrane extractor electrode, The actual microcolumn is
3.5 mm long assembled mainly from silicon membrane electrodes. Improv
ed einzel lens design and fabrication allowed the operation of this be
am focusing element in the accelerating mode. Spherical and chromatic
aberrations were reduced by factors of about 2-3, respectively, as com
pared to he retarding lens mode. Excellent beam current stability with
less than 1% variation over several hours has been observed. (C) 1995
American Vacuum Society.