Thermal nanoimprint lithography using fluoropolymer mold

We studied the properties of a fluoropolymer based on perfluoropolyether (PFPE) as the mold material for thermal nanoimprint lithography. The PFPE mold was duplicated from a hard master mold by casting and thermal-curing of the PFPE pre-polymer mixture. The PFPE mold was able to pattern 100nm half-pitch grating into a resist, with the very fine line edge roughness of the master mold faithfully duplicated into the resist. This implies PFPE is capable of a resolution far beyond 100nm, which is consistent with its high elastic modulus (two orders higher than PDMS) extracted from nanoindentation experiment. It was found that the elastic modulus is much higher near the film surface than deep inside the film. This is a very desirable property for an imprint mold, as the relatively stiff top surface offers high resolution, whereas the more flexible bulk is important for a conformal contact with the substrate and easy demolding.