Defining Chi for Block Copolymer Lithography

Published

January 11, 2023

Author(s)

Whitney Loo, Hongbo Feng, Thomas Ferron, Ricardo Ruiz, Daniel Sunday, Paul Nealey

Abstract

Block copolymer lithography, such as directed self-assembly, requires the design of nanostructured block copolymers with precise values of segregation strength, 20≤χN≤25, in order to balance covarying material properties and meet manufacturing requirements. Therefore, reliable methods of experimentally measuring the Flory-Huggins interaction parameter, χ, are needed in the intermediate segregation strength regime for systems without accessible order-disorder transition temperatures. We calculate χ_eff using strong segregation theory (SST), but due to discrepancies in L_0 from bulk versus thin film experiments, values of χ_eff using SST for were quantitatively inconsistent. Therefore, we propose to use the extent of mixing, quantified as a normalized interface width, w_m/L_0 where w_m is the interfacial width and L_0 is the block copolymer pitch, as a thermodynamic parameter. We experimentally measure w_m and L_0 for a series of lamellar A-b-(B-r-C) copolymers via resonant soft X-ray reflectivity to extract values of χ_eff N based on previous data collected for A-b-B copolymers. The extracted χ_eff values from comparisons of w_m/L_0 between the A-b-(B-r-C) copolymers and previous data on A-b-B copolymers agreed quantitatively between copolymers of different molecular weights. Block copolymers for lithographic applications are uniquely poised to use effect of mixing as a fundamental thermodynamic parameter due to their inaccessible order-disorder transition temperatures, intermediate values of χN, and the importance of w_m for line edge roughness metrics.

Citation

ACS Macro Letters

Pub Type

Journals

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Keywords

Lithography, Polymer, Block Copolymer, Reflectivity, X-ray

Citation

Loo, W. , Feng, H. , Ferron, T. , Ruiz, R. , Sunday, D. and Nealey, P. (2023), Defining Chi for Block Copolymer Lithography, ACS Macro Letters, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935216 (Accessed April 19, 2024)