Simulation of secondary electron emission from a stepped surface in scanning ion microscopes

Abstract

For the use of scanning ion microscopes in device metrology, secondary electron (SE) emission from step patterns formed on a silicon substrate is investigated by simulation. The entire surface of a step is irradiated by H, He, Ne, and Ga ions with energies of 10–50 keV to form the line profile of the SE yield. Because of their highly localized production of SEs, light-ion beams result in clearer peaks in the line profile than heavy-ion beams. The recoiling atoms and cascade electrons contribute to the height of the SE peak, but tend to broaden it as well. Both the peak height and width decrease with decreasing step height. The presence of an inclining side wall in the step largely decreases the peak height and increases the peak width. Reducing the ion energy decreases the height gradually, but produces no clear change in the width.