Apparatus and method for projection ion beam lithography are described which allow formation of low distortion, large field, reduced images of a mask pattern at a wafer plane using an optical column of practical size. The column shown is comprised of an accelerating Einzel lens followed by a gap lens,...http://www.google.fr/patents/US4985634?utm_source=gb-gplus-shareBrevet US4985634 - Ion beam lithography
