Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers

Richard A. Lawson, Andrew J Peters, Benjamin Nation, Peter J. Ludovice, Clifford L. Henderson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

Implementation of directed self-assembly (DSA) of block copolymers (BCPs) introduces a series of engineering challenges that have not been completely addressed in previous block copolymer and lithography studies. One of the required innovations for further DSA development and implementation is the accurate simulation of specific block copolymer chemistries and their interactions with interfaces. Many of the BCP simulation tools developed so far have limitations or difficulty in terms of matching many of the common issues found in experimental BCP systems such as polydispersity and different statistical segment lengths. One of the potentially most important issues is the fact that real BCPs often have block energy and/or density asymmetry, meaning that each block has a different homopolymer density and/or cohesive energy density (CED). A simulation of BCP behavior and DSA processes based on molecular dynamics (MD) of coarse-grained polymer chains has been developed that can independently parameterize and control the density and CED of each block to more accurately match the asymmetry found in experimental BCPs. This model was used to study the effect of block asymmetry on the order-disorder transition (ODT), domain scaling, and self-assembly of thin films of BCPs. BCPs whose blocks each have a different density show deviations from the mean-field ODT coexistence curve, exhibiting an order-disorder transition or co-existence curve that is asymmetric with shifts and tilts in the direction of majority highest density block. This impact of density and cohesive energy differences diblock copolymers on their phase behavior can explain some of the unexpected shapes found experimentally in BCP ODT curves. Asymmetry in the BCP block energy or density does not appear to have a significant effect on domain scaling behavior compared to the mean-field estimates. Self-assembly of thin films of BCPs with mismatches in CED shows significant deviations in the expected morphologies from ones simulated using equivalent densities and cohesive energy densities. The lowest CED block has a strong propensity to segregate to and wet the free interface at the top of the film because it has the lowest energy penalty for the loss of interactions with other chains at the free surface relative to the bulk. This gives rise to an effective skinning of the film by the lowest CED block for almost the entire potential range of underlayer compositions and film thicknesses. Such materials will be extremely difficult to successfully pattern transfer for a lithographically useful process because they will not form vertically aligned morphologies through the entire film thickness. This CED mismatch also gives rise to a large number of non-bulk morphologies and deviations from bulk behavior including changing vertical-to-horizontal morphologies through film depth, compression and expansion of domain sizes to match film thickness dimensions, and island and hole formation among others. Increasing the ΧN value can potentially suppress some of these non-idealities due to CED asymmetry, but the required ΧN to overcome these issues will differ from polymer to polymer depending on the magnitude of the CED asymmetry.

Original languageEnglish (US)
Title of host publicationAlternative Lithographic Technologies VI
PublisherSPIE
ISBN (Print)9780819499721
DOIs
StatePublished - Jan 1 2014
EventAlternative Lithographic Technologies VI - San Jose, CA, United States
Duration: Feb 24 2014Feb 27 2014

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume9049
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceAlternative Lithographic Technologies VI
CountryUnited States
CitySan Jose, CA
Period2/24/142/27/14

Fingerprint

Block Copolymers
Self-assembly
block copolymers
Self assembly
Block copolymers
self assembly
Simulation Study
Energy Density
flux density
Energy
Asymmetry
simulation
Order disorder transitions
asymmetry
energy
Disorder
disorders
Lowest
Film thickness
film thickness

Keywords

  • Block copolymer
  • Coarse grained
  • Cohesive energy density
  • Directed self-assembly
  • Domain scaling
  • Molecular dynamics
  • Order-disorder transition
  • Thin film morphologies

Cite this

Lawson, R. A., Peters, A. J., Nation, B., Ludovice, P. J., & Henderson, C. L. (2014). Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers. In Alternative Lithographic Technologies VI [90490S] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 9049). SPIE. https://doi.org/10.1117/12.2046603

Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers. / Lawson, Richard A.; Peters, Andrew J; Nation, Benjamin; Ludovice, Peter J.; Henderson, Clifford L.

Alternative Lithographic Technologies VI. SPIE, 2014. 90490S (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 9049).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Lawson, RA, Peters, AJ, Nation, B, Ludovice, PJ & Henderson, CL 2014, Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers. in Alternative Lithographic Technologies VI., 90490S, Proceedings of SPIE - The International Society for Optical Engineering, vol. 9049, SPIE, Alternative Lithographic Technologies VI, San Jose, CA, United States, 2/24/14. https://doi.org/10.1117/12.2046603
Lawson RA, Peters AJ, Nation B, Ludovice PJ, Henderson CL. Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers. In Alternative Lithographic Technologies VI. SPIE. 2014. 90490S. (Proceedings of SPIE - The International Society for Optical Engineering). https://doi.org/10.1117/12.2046603
Lawson, Richard A. ; Peters, Andrew J ; Nation, Benjamin ; Ludovice, Peter J. ; Henderson, Clifford L. / Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers. Alternative Lithographic Technologies VI. SPIE, 2014. (Proceedings of SPIE - The International Society for Optical Engineering).
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