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Design of surface patterns for optimization of thermodynamic driving forces for the directed self-assembly of block copolymers for lithographic applications

Abstract

It is well-established by theory and experiment that lamella forming block copolymers with characteristic periodicity, L0, can assemble lines-and-spaces over carefully crafted chemically patterned substrates comprised of stripes of width W that repeat with period LS. Where as previous works measure the efficacy of pattern designs for self-assembly through visual inspection of experimental images or examination of morphologies obtained from simulations, here we combine visual inspection over a large number of processing conditions with a new theoretical strategy that quantitatively measures the thermodynamic driving force of chemical patterns to produce a single grain of lines-and-spaces. The metric we use to describe the thermodynamic driving force is defined by the free-energy difference between the desired assembly of lines-and-spaces and the grain orientation with the lowest energy, referred to as the most-competitive assembly. Visualization of experimental systems using SEM-imaging provide a first-order approximation of the process windows in pattern design space in regards to W and the chemical contrast of the stripe and the background region, where the thermodynamic driving force is large enough to eliminate competitive grains. The strategy proposed in this work then uses complimentary molecular simulations to elucidate which combination of these pattern parameters provides the largest driving force through free-energy calculations obtained by thermodynamic integration and attempts to identify which pattern designs minimize the probability of assembling lamella that are stabilized at undesired angles to the patterned stripes. The combination of experiment and theory shows that narrow guiding stripes with width 0.4 ≤ W /L0 ≤ 0.8 that are highly preferential for one of the blocks are best for obtaining a directed self-assembly process flow that has the highest probability of assembling a desired grain orientation.

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Publication details

The article was received on 14 Apr 2017, accepted on 03 Aug 2017 and first published on 03 Aug 2017


Article type: Paper
DOI: 10.1039/C7ME00028F
Citation: Mol. Syst. Des. Eng., 2017, Accepted Manuscript
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    Design of surface patterns for optimization of thermodynamic driving forces for the directed self-assembly of block copolymers for lithographic applications

    G. P. Garner, P. Rincon Delgadillo, R. Gronheid, P. F. Nealey and J. J. de Pablo, Mol. Syst. Des. Eng., 2017, Accepted Manuscript , DOI: 10.1039/C7ME00028F

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