New methodologies for patterning micro- and nano- scale features in polymer thin films are desired because of their high technological relevance to a range of applications, including microelectronics and magnetic storage media fabrication. As device structures shrink in size with every new device generation, traditional lithography strategies (i.e., photoresists light exposed through photomasks within projection systems) are continually being challenged to reach targets. In recent years, complementary strategies are gaining more traction in academia and industry and one promising approach involves exploiting block copolymers (BCPs) that naturally self-assemble into domains ~1-100 nm in size. However, one major challenge is that their self-assembled structures must be directed into device relevant arrangements to be useful for manufacturing. I will provide an overview of our efforts in this area and then focus on a specific photochemical process for controlling BCP domain orientation in an area selected manner. Polymers with photoswitching surface energy, used as interfacial layers adjoining the BCP film, were synthesized with photoacid labile monomers. The interfacial polymers were designed to be either inherently neutral or preferential to a target BCP. Through patternwise exposure to 193nm light and subsequent reaction with photogenerated acid, the wetting characteristics of the interfacial material can be switched from neutral to preferential (N2P) or preferential to neutral (P2N). Thermal annealing of the BCP confined between patterned N2P or P2N interfacial layers resulted in alternating areas of perpendicular and parallel BCP domains within the same film. If adapted in tandem with directed self-assembly, this approach could enable new routes to customizable patterns for advanced microelectronics and memory devices.
Christopher J. Ellison is an Associate Professor and the Frank A. Liddell, Jr. Centennial Fellow in the McKetta Department of Chemical Engineering at the University of Texas at Austin. He is also affiliated with the Texas Materials Institute, the materials science and engineering program. He earned a B.S. in Chemical Engineering from Iowa State University in 2000. He received his Ph.D. in Chemical Engineering from Northwestern University in 2005 with Prof. John M. Torkelson where he studied physical aging and the glass transition in nanoconfined polymer thin films. From 2006-2008, he conducted postdoctoral research in the Department of Chemical Engineering and Materials Science at the University of Minnesota with Prof. Frank S. Bates where he studied the phase behavior of polydisperse block copolymers and nanofiber manufacturing methods. His group’s current research interests include block copolymer self-assembly in thin films, structure and dynamics of nanoconfined polymers, and light-activated chemistries for thin film patterning and fiber manufacturing. He is recipient of the National Science Foundation CAREER Award, DuPont Young Professor Award, 3M Nontenured Faculty Award and AIChE Owens Corning Early Career Award.