Supported by NSF Grant DMR 0425880

1. Organic Thin-films for Controlling the Orientation of Block Copolymer Domains Eungnak Han,1 Insik In,1 Young-Hye La, 2 Sang Min Park,2 Paul. F. Nealey,2 Padma Gopalan1 1Department of Materials Science and Engineering, 2Department of Chemical and Biological Engineering, University of Wisconsin, Madison, WI, USA. Paul F. Nealy, University of Wisconsin-Madison, DMR 0425880 Block copolymer lithography often requires surface modification to direct the orientation of the domains. We have demonstrated a new type of polymer brush containing a third comonomer (C) in the random copolymer brush P(A-r-B-r-C) to equalize the interfacial energies of the two blocks of a diblock copolymer (A-b-B). When third monomer (C) contains hydroxyl groups, multipoint covalent anchoring to silicon oxide results in neutral wetting surfaces [1]. These brushes offered a number of advantages over previous materials such as ease of synthesis, fast binding kinetics and effectiveness in very thin layers, an advantageous property for pattern transfer. It is often desirable to treat a wide range of substrates such as gold coated, glass, III-V semiconductors and other oxide surfaces in addition to Si for microelectronic applications. Room temperature negative-tone photoresist chemistry was exploited to generate ultra-thin neutral surfaces and to pattern alternate regions with neutral and preferential wetting characteristics. Here the third monomer (C) contains a photo-crosslinkable epoxy or acryloyl group [2]. Figure: (a) The P(S-r-MMA-r-HEMA) random copolymer binds to the silicon substrate through a thermal dehydration reaction, (b) the same brush modified to incorporate a acryloyl and (c) glycydyl group can be photocrossliked to silicon, gold coated, paper or glass substrate, (d) The photocrosslinkable films were patterned by exposure to UV irradiation (254 nm) through a TEM grid as a photo-mask. Successive washing resulted in preferential and neutral wetting patterns over unexposed and exposed regions, respectively, (e) Vertical lamella morphology in the exposed regions is clearly observed in the high resolution SEM images, and (f) The characteristic hole/island morphology for parallel lamella orientation is apparent in the SEM micrograph of the unexposed region. [1] I. In, Y. H. La, S. M. Park, P.F.Nealey, P.Gopalan, Langmuir 2006, 22, 7855 [2] E. Han, I. In, Y. H. La, S. M. Park, Y. Yang, P. F. Nealey, P. Gopalan, Advanced Materials 2007, 19, 4448. Supported by NSF Grant DMR 0425880