MRS Bulletin

Technical Feature

Technical Feature

Block Copolymer Lithography: Merging “Bottom-Up” with “Top-Down” Processes

Craig J. Hawker and Thomas P. Russell

Abstract

As the size scale of device features becomes ever smaller, conventional lithographic processes become increasingly more difficult and expensive, especially at a minimum feature size of less than 45 nm. Consequently, to achieve higher-density circuits, storage devices, or displays, it is evident that alternative routes need to be developed to circumvent both cost and manufacturing issues.

An ideal process would be compatible with existing technological processes and manufacturing techniques; these strategies, together with novel materials, could allow significant advances to be made in meeting both short-term and long-term demands for higher-density, faster devices. The self-assembly of block copolymers (BCPs), two polymer chains covalently linked together at one end, provides a robust solution to these challenges. As thin films, immiscible BCPs self-assemble into a range of highly ordered morphologies where the size scale of the features is only limited by the size of the polymer chains and are, therefore, nanoscopic.

While self-assembly alone is sufficient for a number of applications in fabricating advanced microelectronics, directed, self-orienting, self-assembly processes are also required to produce complex devices with the required density and addressability of elements to meet future demands. Both strategies require the design and synthesis of polymers that have well-defined characteristics such that the necessary fine control over the morphology, interfacial properties, and simplicity of processes can be realized. By combining tailored self-assembly processes (a “bottom-up” approach) with microfabrication processes (a “top-down” approach), the ever-present thirst of the consumer for faster, better, and cheaper devices can be met in very simple, yet robust, ways. The integration of novel chemistries with the manipulation of self-assembly will be treated in this article.

Keywords

  • block copolymer;
  • lithography;
  • nanoscale;
  • polymer;
  • self-assembly.

Craig J. Hawker is director of the Materials Research Laboratory at the University of California, Santa Barbara. Following his postdoctoral work with Jean Fréchet at Cornell University, he was a research staff member at the IBM Almaden Research Center from 1993 to 2004. His research focuses on the interface between organic and polymer chemistry with an emphasis on the design, synthesis, and application of well-defined macromolecular structures in biotechnology, microelectronics, and surface science. He has most recently been honored by the 2005 ACS Award in Applied Polymer Science and the 2005 Dutch Polymer Award, and he is listed as one of the top 100 most cited chemists worldwide over the last decade (1994–2004).

Hawker can be reached at University of California, Santa Barbara, Materials Research Laboratory, Santa Barbara, CA 93106, USA; tel. 805-893-7161, fax 805-893-4120, and e-mail hawker@mrl.ucsb.edu.

Thomas P. Russell has been a professor of polymer science and engineering at the University of Massachusetts Amherst since 1997. He is also director of the Materials Research Science and Engineering Center on Polymers, an associate director of MassNanoTech, and director of the Multi-University Research Initiative on Nanoscopic Assembly of Biologically Active Materials. He received his PhD degree in polymer science and engineering from UMass Amherst in 1979. From 1981 to 1996, he was a research staff member at the IBM Almaden Research Center in San Jose, Calif. His research interests include the surface and interfacial properties of polymers, phase transitions in polymers, directed self-assembly processes, the use of polymers as scaffolds and templates for the generation of nanoscopic structures, the interfacial assembly of nanoparticles, and the influence of supercritical fluids on phase transitions and dynamics in polymer thin films.

Russell is an associate editor of Macromolecules and a fellow of both the American Physical Society and the American Association for the Advancement of Science. He received the A.K. Doolittle Award in 1984, the Cooperative Research Award from the American Chemical Society in 2002, the Dutch Polymer Award in 2004, and the Polymer Physics Prize of the American Physical Society in 2005. He was name a Distinguished Professor in 2004.

Russell can be reached at the University of Massachusetts Amherst, Polymer Science and Engineering Department, Conte Polymer Research Center, 120 Governors Drive, Amherst, MA 01003-9263, USA; tel. 413-577-1516, fax 413-545-0082, and e-mail russell@mail.pse.umass.edu.

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