Self-Assembly of Cylinder-Forming Block Copolymers on Ultrananocrystalline Diamond (UNCD) Thin Films for Lithographic Ap
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1203-J17-15
Self-Assembly of Cylinder-Forming Block Copolymers on Ultrananocrystalline Diamond (UNCD) Thin Films for Lithographic Applications Muruganathan Ramanathan *†; Seth B. Darling†; Anirudha V. Sumant†; Orlando Auciello†‡ †Center for Nanoscale Materials and ‡Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 ABSTRACT Block copolymers (BCPs) consist of two or more chemically distinct and incompatible polymer chains (or blocks) covalently bonded. Due to the incompatibility and connectivity constraints between the two blocks, diblock copolymers spontaneously self-assemble into microphaseseparated nanoscale domains that exhibit ordered 0, 1, 2 or 3 dimensional morphologies at equilibrium. Commonly observed microdomain morphologies in bulk samples are periodic arrangements of lamellae, cylinders, or spheres. Block copolymer lithography refers to the use of these ordered structures in the form of thin films as templates for patterning through selective etching or deposition. The self-assembly and domain orientation of block copolymers on a given substrate is critical to realize block copolymer lithography as a tool for large throughput nanolithography applications. In this work, we survey the morphology of cylinder-forming block copolymers by atomic force microscopy (AFM). Three kind of block copolymers were studied: a) poly(styrene-block-ferrocenyldimethylsilane), PS-b-PFS b) poly(styrene-blockmethylmethacrylate), PS-b-PMMA and c) poly(styrene-block-dimethylsiloxane) PS-b-PDMS. Block copolymers were dissolved in a neutral solvent for both blocks (toluene) in order to obtain solutions of various concentrations (1 and 1.5 wt %). From these solutions, films were prepared by spin casting on ultrananocrystalline diamond (UNCD) thin film substrates. Results indicate that PS-b-PFS exhibits chemical and morphological compatibility to the UNCD surface in terms of wetting and domain control. A systematic comparison of self-assembly of these polymers on silicon nitride substrates demonstrates that UNCD thin films would require pre-treatment to be considered as a substrate for BCP lithography. INTRODUCTION The quest for developing materials at the nanoscale is escalating since early this decade. As the dimension of the materials reduced from the bulk to a system composed of few tens of atoms at the nanoscale, fascinating properties in magnetism, catalysis, electronics, optics, mechanics and ferroelectricity emerged. The transition from fundamental science to real world applications, for instance, in the fields of energy (photovoltaics), electronics (miniaturized ultrahigh capacity storage devices), developmental biology (therapeutics) and biomedical engineering, greatly relies on developing nanostructured materials. Among the various nanostructures, nanowires receive special attention due to their relevance in many technological applications. 1, 2 Both bottom-up and top-down methodologies have been successfully implemented to develop nanowires of various materials. 3-8 In this work
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