Micro/Nanofabrication by Spin Dewetting on a Poly(Dimethylsiloxane) Mold
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1002-N05-11
Micro/Nanofabrication by Spin Dewetting on a Poly(dimethylsiloxane) Mold Nicholas Ferrell1, Aimee Bross2, and Derek Hansford1 1 Department of Biomedical Engineering, Ohio State University, 1080 Carmack Rd., 270 Bevis Hall, Columbus, OH, 43210 2 Nanoscale Patterning Laboratory, Ohio State University, 205 Dreese Laboratory, 2015 Neil Ave., Columbus, OH, 43210
ABSTRACT The process of spin dewetting was used to fabricate polymer micro and nanostructures from poly(methyl methacrylate) (PMMA), poly (propyl methacrylate) (PPMA), and polystyrene (PS). Polymer structures were formed on poly(dimethylsiloxane) (PDMS) molds by dewetting of a polymer solution during spin coating. Features were removed from the mold using heat and pressure to transfer the polymer to silicon or glass substrates. By varying the coating conditions, a variety of different polymer feature morphologies were obtained for a given PDMS mold geometry. In this study, the ability to fabrication polymer micro and nanostructures using spin dewetting was demonstrated on a variety of PDMS mold geometries. The effects of polymer solution concentration and mold feature size on the resulting polymer structures were examined. In addition, microfabricated PMMA structures were used as etch masks for anisotropic etching of silicon in an aqueous solution of tetramethylammonium hydroxide (TMAH). INTRODUCTION The ability to fabricate polymer micro and nanostructures is vitally important for applications ranging from microelectronics and MEMS to biomedical devices. Photolithography is the standard for fabrication of polymer microstructures. The ability to fabricate polymer microfeatures from inexpensive, chemically versatile materials using more cost effective processing techniques is highly advantageous. A number of techniques, many of which are based on soft lithography [1], have been developed for fabrication of polymer micro and nanostructures. These techniques include microtranfer molding [2], micromolding in capillaries [3], and micro-fluid-contact printing [4] among others. Controlled dewetting of polymers on surfaces has also been used for polymer microfabrication. This has primarily been achieved by patterning different surface chemistries on a substrate [5-7]. Here we introduce the process of spin dewetting as a method for fabrication of polymer micro and nanostructures from various polymer materials. This technique combines soft lithography, spin coating, and polymer dewetting to provide a method for fabricating structured polymer films and physically independent polymer microstructures from several different polymers. By varying polymer solution concentration, the dewetting behavior can be altered, thus allowing formation of features with geometries that are significantly different than the original mold. These microstructures can be used directly in device applications or as etch masks for further silicon processing. PMMA has previously been suggested as a masking material for silicon etching in KOH and TMAH [8-10]. Spin dewetting provides a simp
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