A multiple beam charged particle optical system

摘要

The invention relates to a multiple beam charged particle optical system comprising a charged particle source for emitting a beam of charged particles, an aperture array element included between said source and a target. Each aperture of said aperture array element constitutes a current limiting aperture for a beamlet, said aperture array element being a single unit in which each aperture of said current limiting array is provided in communication with a separate hole in said aperture array element, wherein each hole has a larger diameter than said aperture in communication therewith, and each said hole has a diameter smaller than a thickness of said unit.