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Proceedings Paper

Contrast enhanced diffusion NMR: quantifying impurities in block copolymers for DSA
Author(s): Rudy Wojtecki; Ellie Porath; Ankit Vora; Alshakim Nelson; Daniel Sanders
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Paper Abstract

Block-copolymers (BCPs) offer the potential to meet the demands of next generation lithographic materials as they can self-assemble into scalable and tailorable nanometer scale patterns. In order for these materials to find wide spread adoption many challenges remain, including reproducible thin film morphology, for which the purity of block copolymers is critical. One of the sources of impurities are reaction conditions used to synthesize block copolymers that may result in the formation of homopolymer as a side product, which can impact the quality and the morphology of self-assembled features. Detection and characterization of these homopolymer impurities can be challenging by traditional methods of polymer characterization. We will discuss an alternate NMR-based method for the detection of homopolymer impurities in block copolymers – contrast enhanced diffusion ordered spectroscopy (CEDOSY). This experimental technique measures the diffusion coefficient of polymeric materials in the solution allowing for the ‘virtual’ or spectroscopic separation of BCPs that contain homopolymer impurities. Furthermore, the contrast between the diffusion coefficient of mixtures containing BCPs and homopolymer impurities can be enhanced by taking advantage of the chemical mismatch of the two blocks to effectively increase the size of the BCP (and diffusion coefficient) through the formation of micelles using a cosolvent, while the size and diffusion coefficient of homopolymer impurities remain unchanged. This enables the spectroscopic separation of even small amounts of homopolymer impurities that are similar in size to BCPs. Herein, we present the results using the CEDOSY technique with both first generation BCP system, poly(styrene)-b-poly(methyl methacrylate), as well as a second generation high-χ system.

Paper Details

Date Published: 21 March 2016
PDF: 6 pages
Proc. SPIE 9779, Advances in Patterning Materials and Processes XXXIII, 977922 (21 March 2016); doi: 10.1117/12.2218633
Show Author Affiliations
Rudy Wojtecki, IBM-Almaden Research Ctr. (United States)
Ellie Porath, Univ. of Chicago (United States)
Ankit Vora, IBM-Almaden Research Ctr. (United States)
Alshakim Nelson, Univ. of Washington (United States)
Daniel Sanders, IBM-Almaden Research Ctr. (United States)

Published in SPIE Proceedings Vol. 9779:
Advances in Patterning Materials and Processes XXXIII
Christoph K. Hohle; Rick Uchida, Editor(s)

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