Formation of Nanometer-Scale Dot Arrays from Diblock Copolymer Templates
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Formation of Nanometer-Scale Dot Arrays from Diblock Copolymer Templates C. T. Black, K. W. Guarini, R. L. Sandstrom, S. Yeung,1 and Y. Zhang IBM T. J. Watson Research Center, Yorktown Heights, NY 10598 1 present address: University of California, Berkeley, CA 94720. ABSTRACT We have developed four different fabrication processes based on self-organizing diblock copolymers that all produce densely-spaced, uniformly-sized nanometer-scale dot arrays over large wafer areas. We demonstrate the versatility of these techniques through examples of dot arrays formed of metallic, insulating, and polymeric materials. These fabrication processes vary in complexity, utility, and degree of optimization, and we discuss the relative merits of each. The ability to create uniform nanoscale features below lithographic resolution limits may enable key applications in fields such as magnetic recording and microelectronics. INTRODUCTION We have been exploring self-organizing diblock copolymer thin films as general templates for patterning surfaces on length scales below lithographic resolution limits, and specifically for applications in microelectronics. For example, we have previously described our use of these polymer films as masks for reactive ion etching (RIE) in order to produce electrodes with increased surface area [1]. In addition, several other groups have been investigating various versions of surface patterning using diblock copolymers [2,3,4,5,6,7]. Here we describe processes for forming nanometer-scale dot arrays from polymer templates. Such structures may find use in applications such as magnetic media [5] or as quantum dots [2] and will also prove useful as masks for etching pillar structures with sub-lithographic dimensions [8]. We present four different methods for producing nanometer-scale dot arrays, all of which use diblock copolymer templates as a starting point for fabrication. First we demonstrate a method of producing self-assembled polymeric dots by adjusting the composition of the block copolymer itself. We also describe a process for forming arrays of silicon nitride dots that integrates the polymer template with conventional semiconductor fabrication techniques such as reactive ion etching and chemical vapor deposition. Both of these methods are attractive because they are entirely materials-compatible with silicon processing, and can therefore be used as steps in the fabrication of silicon devices. We have also developed an extremely versatile method for producing nanodot arrays using a liftoff technique. Finally, we describe a curious example of how a nanostructured surface affects the self-assembly of chemically-synthesized nanocrystals. POLYMER DOT ARRAYS Our previous experiments used diblock copolymers composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA), both because the behavior of these two polymers is well understood and because of their materials compatibility with standard semiconductor processing [1,9,10]. We have previously described details of the polymer template formation, and s
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