FUNDAMENTAL LIMITS TO IMAGING RESOLUTION FOR FOCUSED ION-BEAMS

This article investigates the limitations on the formation of focused ion beam images from secondary electrons. We use the notion of the inf ormation content of an image to account for the effects of resolution, contrast, and signal-to-noise ratio and show that there is a competit ion between the rate at which small features are sputtered away by the primary beam and the rate of collection of secondary electrons. We fi nd that for small features, sputtering is the limit to imaging resolut ion, and that for extended small features (e.g., layered structures), rearrangement, redeposition, and differential sputtering rates may lim it the resolution in some cases. (C) 1996 American Vacuum Society.