Directed self-assembly of poly(styrene)-block-poly(acrylic acid) copolymers for sub-20nm pitch patterning

Jing Cheng, Richard A. Lawson, Wei Ming Yeh, Nathan D. Jarnagin, Andrew Peters, Laren M. Tolbert, Clifford L. Henderson

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

5 Scopus citations


Directed self-assembly (DSA) of block copolymers is a promising technology for extending the patterning capability of current lithographic exposure tools. For example, production of sub-40 nm pitch features using 193nm exposure technologies is conceivably possible using DSA methods without relying on time consuming, challenging, and expensive multiple patterning schemes. Significant recent work has focused on demonstration of the ability to produce large areas of regular grating structures with low numbers of defects using self-assembly of poly(styrene)-b-poly(methyl methacrylate) copolymers (PS-b-PMMA). While these recent results are promising and have shown the ability to print pitches approaching 20 nm using DSA, the ability to advance to even smaller pitches will be dependent upon the ability to develop new block copolymers with higher χ values and the associated alignment and block removal processes required to achieve successful DSA with these new materials. This paper reports on work focused on identifying higher χ block copolymers and their associated DSA processes for sub-20 nm pitch patterning. In this work, DSA using polystyrene-b-polyacid materials has been explored. Specifically, it is shown that poly(styrene)-b-poly(acrylic acid) copolymers (PS-b-PAA) is one promising material for achieving substantially smaller pitch patterns than those possible with PS-b-PMMA while still utilizing simple hydrocarbon polymers. In fact, it is anticipated that much of the learning that has been done with the PS-b-PMMA system, such as development of highly selective plasma etch block removal procedures, can be directly leveraged or transferred to the PS-b-PAA system. Acetone vapor annealing of PS-b-PAA (Mw=16,000 g/mol with 50:50 mole ratio of PS:PAA) and its self-assembly into a lamellar morphology is demonstrated to generate a pattern pitch size (L0) of 21 nm. The χ value for PS-b-PAA was estimated from fingerprint pattern pitch data to be approximately 0.18 which is roughly 4.5 times greater than the χ for PS-b-PMMA (χPS-b-PMMA ∼ 0.04).

Original languageEnglish (US)
Title of host publicationAlternative Lithographic Technologies IV
ISBN (Print)9780819489791
StatePublished - 2012
EventAlternative Lithographic Technologies IV - San Jose, CA, United States
Duration: Feb 13 2012Feb 16 2012

Publication series

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


ConferenceAlternative Lithographic Technologies IV
Country/TerritoryUnited States
CitySan Jose, CA


  • Flory Huggins parameter
  • directed self-assembly
  • poly(styrene)-b-poly(acid)
  • poly(styrene)-b-poly(acrylic acid)
  • χ


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