Surface effects in simulations of scanning electron microscopy images

Abstract. Background: Monte Carlo simulations of scanning electron microscopy (SEM) images ignore most surface effects, such as surface plasmons. Previous experiments have shown that surface plasmons play an important role in the emission of secondary electrons (SEs). Aim: We investigate the influence of incorporating surface plasmons into simulations of low-voltage critical dimension SEM (CD-SEM). Approach: We use a modified inelastic scattering model, derived for infinite flat surfaces, and apply it to nonflat, but smooth, geometries. This simplification captures most qualitative effects, including both surface plasmons and a reduced interaction with bulk plasmons near interfaces. Results: We find that the SE signal hardly changes when surface interactions are turned on for a perpendicularly incident beam. When the incident beam is perfectly parallel to a surface, the SE signal does significantly increase. However, the beam must be extremely close to the surface for this effect to be appreciable. An SEM is unable to produce a beam that is both narrow and parallel enough to be noticeably affected. Conclusions: The position of edges may appear shifted under specific circumstances. In realistic situations, it is unlikely to be a large effect.