Development of Block Co-Polymers as Self-Assembling Templates for Patterned Media
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0961-O01-07
Development of Block Co-Polymers as Self-Assembling Templates for Patterned Media Vishal Warke1,2, Michael L. Curry1, Martin Gerard Bakker1,2, Kunlun Hong3, Jimmy Mays3, Phillip Britt3, Xuefa Li4, and Jin Wang4 1 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, AL, 35487 2 Chemistry, The University of Alabama, Box 870336, Tuscaloosa, AL, 35487-0336 3 Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN, 37831 4 Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439
ABSTRACT Block copolymers that self-organize are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. Poly(styrene)Poly(methylmethacrylate) block co-polymers (PS-b-PMMA) of appropriate block length and PS to PMMA ratio self-assemble into a 2-D hexagonal phase in which the PS majority phase is continuous and surrounds cylinders of the minority, PMMA phase. For application of this phase to patterned media it is necessary that the cylinders of the minority phase be oriented perpendicular to the substrate surface. This can be achieved by a number of methods, including appropriate choice of substrate and use of a random co-polymer underlayer. We report here that indium tin oxide surfaces are also capable of inducing a perpendicular orientation in block co-polymers, likely due to the effect of surface roughness of the substrate. Use of an acetic acid wash causes the minority PMMA component can be induced to be rearranged, giving rise to pores perpendicular to the substrate. Using a conducting substrate such as Tantalum thin film on Silicon wafer, electrodeposition can be carried out into the open pores to produce arrays of magnetic nanopillars of 18 nm diameter. INTRODUCTION There is considerable interest in the use of block copolymers to generate the patterns needed for patterned media.1-2 Block copolymers consisting of immiscible components micro-phase separate to generate structures of definite shape and periodicity. The shape and periodicity are determined by the molecular weight, weight fraction of each block, and segmental interaction parameter (the Flory-Huggins parameter χ) of the polymers3. A major challenge in the use of these materials in patterned media is transferring the pattern from the block co-polymer to the magnetic media. This must be done either as a subtractive process; e.g. using the block co-polymer pattern as an ion-
milling mask, or by an additive process, i.e. growing the magnetic material into voids in the block copolymer. Diblock co-polymers consisting of poly(styrene)-blockpoly(methylmethacrylate) (PS-b-PMMA) are among the most widely used for pattern generation. We have focused on cylinder forming phases of these materials as we believe they have the greatest promise to produce patterned media with satisfactory aspect ratios for the individual bits. However, these types of block copolymers generally do not spontaneously orient perpendicular to the substrate, and so control of ori
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