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Focused ion beam (FIB) repair of opaque defects on photomasks, generally utilizes ion beam induced sputter etching. Surfaces which have been etched by this method sometimes suffer from a loss of transmissivity for several reasons. Among these are, incomplete removal of the chrome film, damage to the substrate from overetching, and implantation of gallium. In the lithography process, any one of these can result in printing of the repaired areas. In an effort to improve the transmissivity of etched areas, post-repair processes such as wet chemical or plasma etching of the substrate have been utilized. These types of processes demonstrate major disadvantages because of the change in reflectivity brought about by the etching action over the entire substrate surface, as well as the addition of another process step, which significantly reduces overall repair throughput. Seiko has developed a proprietary (patents pending) method of sputter etching opaque defects using FIB, resulting in opaque defect repair areas with greater than 97% trans-missivity and significantly reduced gallium concentration levels; without the need for any additional post-repair processing. This paper will present the results of lithography tests and auger anlayses that were conducted to compare our current technique of opaque defect repair with the new technique.
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