A large current scanning electron microscope with MEMS-based multi-beam optics

Recently a multi-beam scanning electron microscope (MBSEM) has been developed, which delivers 196 focused beams to a sample, each of which has around 1nA. In this article a design for an optical system is described and analyzed which can focus all these beams onto a single spot, using an array of micro electron lenses. Although each individual micro lens will be of lower quality than a single macro objective lens, a system is obtained with larger beam current than the conventional SEM. The goal set in an example design is to focus a total current of 200nA within 50nm at a landing energy of 500eV.