Reduced aberrations in an electron matrix lens through the use of offset apertures

Abstract

A design method for a low aberration matrix lens is developed. The matrix lens consists of an electrostatic lens array and beam limiting aperture array located outside of the lens array. It is shown that off‐axial aberrations, which are dominant in the outer lenses, can be reduced by shifting the aperture from the optical axis of each lens to its optimum position. Using this aperture shift effect, a low aberration matrix lens consisting of einzel lenses is designed for submicron electron beam exposure systems. An aberration of 0.1 μm is predicted for a 40 mm2 matrix lens with a beam half‐angle of 5 mrad.