Effects of mask line-and-space ratio in replicating near-0.1-μm patterns in X-ray lithography

In replicating line-and-space ( L/S ) patterns by X-ray proximity printing, optimizing the mask duty together with mask contrast is crucial to obtain high resolution in the 0.1 µ m region. We have successfully replicated L/S down to the pitch of 0.18 µ m, and evaluated the effects of mask L/S ratio. It was confirmed that the mask L/S ratio is transferred to the replicated pattern more faithfully as the proximity gap becomes narrower, and the ratio should be about 1:1 to achieve large exposure latitude together with wide dose margin. The results of our calculation agreed well with the experimental results upon introducing novel criteria to estimate replicated pattern width. Exposure latitude for 0.1±0.01 µ m L/S replication using the gaps of 10 and 15 µ m was within ±12% with feasible pattern profiles, although the specification of measured mask L/S differed from the ideal one. Even for the gap of 20 µ m the exposure latitude remained within ±6%.