Transfer printing processes with resolution approaching 10 nm are not very common because pattern fidelity is often lost due to translational motion of the patterning molecules. To overcome this challenge, we describe here a photochemical transfer printing (PTP) process in which covalent bonds are formed between a nanopatterned master film formed by self-assembled poly(styrene)-block-poly(methyl methacrylate) (PS-b-PMMA) and solution-deposited conformal layer poly(styrenesulfonylazide-alt-maleic anhydride) in the solid state, where the pattern is fully stable. The monolayer of grafted PS-b-PMMA is then transferred to an initially blank replica film using a photopolymerizable liquid conformal layer possessing very low viscosity (hexanedioldiacrylate, 9 cP), which is known to promote dimensional uniformity in UV nanoimprint technology. The chemical nanopatterns transferred to the replica substrate is continuous and robust enough to successfully direct the self-assembly of new PS-b-PMMA films cast upon it after thermal annealing. The experiments in this work demonstrate patterning resolution down to 14 nm half-periodicity. The PTP process is mechanistically controlled by light and therefore can be spatially controlled by photomasks.
Bibliographical noteFunding Information:
The authors thank Guanyang Lin and Ralph Dammel of EMD Performance Materials, a subsidiary of Merck KGaA Darm-stadt, for providing a PS-b-PMMA used in this study. The authors thank Roel Gronheid, Paulina Rincon, Hari Pathangi, Nadia Vandenbroeck, and Boon Teik Chan of Imec vzw for providing chemically nanopatterned substrates for directed self-assembly. The authors thank Butch Cunningham for machining large-area clamps and suggesting the use of silicone rubber press pads. SEM was performed at the Microscopy and Imaging Facility of the Institute for Cellular and Molecular Biology at the University of Texas at Austin. Partial financial support for this work was provided by the Robert A. Welch Foundation (No. F-1709), the Norman Hackerman ARP, Nissan Chemical Industries, Ltd., a 3M Nontenured Faculty Grant, the Lam Research Corporation, the University of Minnesota, and a DuPont Young Professor Award.
© 2018 The Royal Society of Chemistry.