Masked ion beam lithography system and method

Abstract

A masked ion beam lithography (MIBL) system and method is disclosed which is considerably more compact and economical than prior ion implantation devices. An H.sup.+ ion beam is extracted from a source in the form of an angularly expanding beam, and is transmitted through two lenses that sequentially accelerate the ions to energies in the range of 200-300 keV. The first lens focuses the beam so that it emerges from a crossover point with an amplified angular divergence at least three times the divergence of the initial beam, thereby considerably reducing the necessary column length. The second lens collimates the beam so that it can be directed onto a mask to expose resist on an underlying semiconductor substrate. A series of extraction electrodes are used to provide an initial point source beam with a desired angular expansion, and a specially designed sector magnet is positioned between the extraction mechanism and the first lens to remove particles heavier than H.sup.+ from the beam. Voltage ratios across the lenses and extraction electrodes can be varied in tandem, permitting control over the final beam energy by a simple voltage adjustment. The beam is aligned with the column axis and then steered into alignment with the mask channeling axis by a pair of octupole lenses.