The ability to produce tough, cross-linked networks that can, if necessary, be rendered soluble by an external stimulus such as acid or heat is highly desirable for a number of applications. An acetal containing diacrylate, 2,2-di(acryloyloxy-1-ethoxy)propane (ADA) (1), was synthesized by transketalization with 2-hydroxyethyl acrylate. Its photopolymerization kinetics were measured by real-time FT-IR and its degradation in acidic organic solvents was evaluated. Additionally, a diacrylate cross-linker containing a thermally labile Diels-Alder (DA) linkage ( 2) was synthesized and its reversibility was evaluated using solid-state NMR spectroscopy. The DA cross-linker (2) and ADA (1) were evaluated for use in Step-and-Flash Imprint Lithography (S-FIL). Finally, a dimethacrylate cross-linker containing a thermally labile urethane-oxime linkage (10) was synthesized. Its copolymerization with methyl methacrylate and reversibility were evaluated by size exclusion chromatography (SEC) and 1 H NMR spectroscopy.

Progress in the semiconductor manufacturing industry depends upon continuous improvements in the resolution of lithographic patterning through innovative materials development and frequent retooling with expensive optics and radiation sources. Step and Flash Imprint Lithography is a low-cost, nanoimprint lithography process that generates nanopatterned polymeric films via the photopolymerization of low-viscosity solutions containing cross-linking monomers in a transparent template (mold). The highly cross-linked imprint materials are completely insoluble in all inert solvents, which poses a problem for reworking wafers with faulty imprints and cleaning templates contaminated with cured imprint resist. Degradable cross-linkers provide a means of stripping cross-linked polymer networks. The controlled degradation of polymers containing acetal- and tertiary ester-based cross-linkers is demonstrated herein. The viscosity and dose to cure are presented for several prepolymer formulations, along with imprint resolution and tensile modulus results for the cured polymers. Optimum conditions for de-cross-linking and stripping of the cross-linked polymers are presented, including demonstrations of their utility.

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