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

• We designed a large current system, using a multi-electron beam SEM.
• The multi-electron beam SEM has 196 beamlets each of which has a current about 1 nA.
• The key challenge is to re-focus all beams onto a single spot at the sample.
• We describe the electron optical design of the MEMS-based multi-lens system.
• We show the calculation results by the electron optics design simulation program.

Recently a multi-beam scanning electron microscope (MBSEM) has been developed, which delivers 196 focused beams to a sample, each of which has around 1 nA. 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 200 nA within 50 nm at a landing energy of 500 eV.

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