Deformation of nanostructures on polymer molds during soft UV nanoimprint lithography.

Soft nanoimprint lithography (soft NIL) relies on a mechanical deformation of a resist by a patterned polymer used as a mold. Here, we report on the investigation of the nanopattern fidelity of the high pressure imprint process based on a perfluorinated polyether (PFPE) soft mold material. The perfluorinated polyether material was found to be well suited to transfer the mold pattern into the resist by a direct imprinting process at low cost. Moderate deformations of the polymer mold structures occurring during the high pressure imprint are systematically studied. Features of decreased size are found to be more sensitive to pattern distortions. An optimized pattern design with increased structure density and constant pattern ratio is developed to minimize deformation effects. Imprints performed on the basis of these design rules result in reduced deformations and repeal their size dependence. The improved pattern transfer, especially for small structural elements, turns the direct and cost-effective soft UV-NIL into an interesting technique also for patterning tasks in the lower nanometer range.