Abstract
An electrostatic optical system has been designed to produce a submicron ion beam probe. The main task is to design a low spherical and low chromatic aberration accelerating–focusing lens for the ion gun and to design a combined focusing–deflection system with low deflection aberrations. The gun lens aberrations are minimized by using a parameter optimization method. Very low chromatic aberration coefficients of 3.1 or 6.9 mm are obtained for a working distance of 3 or 6 mm and for an acceleration ratio of 10. An analysis is made of the combined electrostatic focusing–deflection system using MOL concept. A practical electrostatic MOL system was developed which gives good overall deflection aberration performances. It has a theoretical resolution of 73 nm for a beam half‐angle of 5 mrad over a 0.8×0.8 mm scanning area and the resolution can be upward to 20 nm after dynamic correction of the deflection aberrations.
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