Fluorescent UV-curable resists for UV nanoimprint lithography

We developed fluorescent UV-curable resists for UV nanoimprint lithography to readily detect residual layer thickness and analyze its profile in addition to pattern defects by fluorescence microscopy. A fluorescent dye of rhodamine 6G, 2-[6-(ethylamino)-3-(ethylimino)-2,7-dimethyl-3Hxanthen- 9-yl]benzoic acid ethyl ester tetrafluoroborate 5a, showed sufficient durability of photobleaching in solution toward UV-light exposure at <350nm in the absence and presence of a radical photoinitiator. The decrease of fluorescence intensity from the dye in a UV-cured thin film of a radical photopolymerization resin PAK-01 was suppressed at approximately 5% in comparison with the fluorescence intensity before UV-curing at an exposure dose of 1.0 J cm^-2 monitored at 365 nm. It was confirmed that the fluorescence intensity of the UV-cured thin film showed a linear correlation to its thickness up to 100 nm. A dye-added PAK-01 resin was successfully available to UV nanoimprint. We demonstrated that the UV-cured thin film of the dye-containing resin was useful for facile confirmation and analysis of residual layer thickness in terms of its homogeneity.