Focused ion beam lithography-overview and new approaches

Focused Ion Beam (FIB) lithography has significant advantages over the electron beam counterpart in terms of resist sensitivity, backscattering and proximity effects. Applying the Top Surface Imaging (TSI) principal to FIB lithography could further enhance its capability. In this paper we review different FIB lithography processes which utilise both wet and dry development. As of further development of this technology, we report a novel lithography process which combines focused Ga⁺ ion beam (Ga⁺ FIB) exposure, silylation and oxygen dry etching. The Negative Resist Image by Dry Etching (NERIME) is a TSI scheme for DNQ/novolak based resists and can result in either positive or negative resist images depending on the extent of the ion beam exposure dose. The NERIME process can resolve nanometer resist patterns as small as 30nm yet maintaining high aspect ratio of up to 15. The proposed lithography scheme could be utilised for advanced prototype IC´s fabrication and critical CMOS lithography process steps.