University of Wisconsin-Madison NSEC: Templated Synthesis and Assembly at the Nanoscale

1. Etching Amount (nm) Etching Time (s) Thrust 1: Direct Patternable Organic-Inorganic Hybrid Block Copolymer Template T. Hirai, M. Leolukman, C.C. Liu, E. Han, Y.J. Kim, Y. Ishida, T. Hayakawa, M.-A. Kakimoto, P.F. Nealey, P. Gopalan (a) (b) PMMA-b-PMAPOSS University of Wisconsin-MadisonNSEC: Templated Synthesis and Assembly at the Nanoscale 200 nm (c) PS-b-PMAPOSS 150 nm Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) has many advantages: it is very well studied, commercially available, and its blocks have nearly equal surface energies, which is advantageous for directed assembly. However, P(S-b-MMA) has a relatively small Flory-Huggins interaction parameter, , which precludes the formation of lamellar or cylindrical domains with dimensions less than 12 nm. We have achieved large values and smaller feature size by incorporating silicon in the monomers of one of the blocks. The inclusion of silicon is particularly attractive as it greatly increases the etch selectivity of the copolymer. We have synthesized a new series of polyhedral oligomeric silsesquioxane (POSS) containing block copolymers, made via living anionic polymerization. The bulk samples exhibit well defined microphase-separated structures with long-range order. The thin-film assembly of these organic-inorganic block copolymers PS-b-PMAPOSS and PMMA-b-PMAPOSS by solvent annealing on unmodified substrates, combined with the high etch selectivity between the blocks, and the ability to access very small domain sizes (<10 nm) makes these BCPs a unique and exciting material platform to create etch-resistant masks. (d) Figure. (a) Schematic illustration of the fabrication of silicon oxide line arrays and nanopore arrays. Lamella forming PS-b-PMAPOSS and cylinder forming PMMA-b-PMAPOSS were spin coated onto silicon substrate and exposed to solvent vapors to induce vertical orientation , (b) and (c) are the corresponding TEM images of bulk samples showing lamellar and PS cylindrical morphologies, and (d) plot of etch amount of PS, PMMA and PMAPOSS homopolymers with increasing etch time in O2 plasma.