Design of a variable‐aperture projection and scanning system for electron beam

Results of design calculations of a variable‐aperture projection and scanning exposure system is presented. Use is made of newly developed aberration formulas for the focus deflection system, which can handle systems consisting of a set of focus and deflection coils with superimposed fields and of deflection coils arranged in rotated angular positions, taking into account the finiteness of the object. The aberration of less than 0.2 μm and the incident angle less than 1 mrad with the normal, at the corners of a 5×5 mm deflection field, is expected for the 25 μm (maximum) square and 3 mrad semi‐angle probe, in the linear MOL deflector, with object to image distange of 100 mm, consisting of only an axially symmetric lens and five linear deflectors without dynamic corrections.