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Template-Polymer Commensurability and Directed Self-Assembly Block Copolymer Lithography



Daniel F. Sunday, Regis J. Kline, Elizabeth Ashley, Lei Wan, Kaniyal Patel, Ricardo Ruiz


The directed self assembly (DSA) of block copolymers (BCP’s) is being explored for lithographic patterning of features between 5 nm and 50 nm. The chemoepitaxial approach towards DSA utilizes a chemical template to promote long range ordering of the BCP and one of the key parameters for success is commensurability of the BCP with the template. In order to understand how this parameter impacts the result of the assembly process we patterned polystyrene–b-poly(methyl methacrylate) (PS-PMMA) on a radial template, where the commensurate pitch was in the center of the pattern. Three separate samples were prepared from the template, one where the PMMA was removed leaving a PS line grating and two where others where the underlying Si was etched to produce Si lines. Critical dimension small angle x-ray scattering (CDSAXS) was used to study the shape of the grating and the roughness. It was found that compression of the BCP does not result in significant changes to the either the shape or roughness of the lines, but that tension on the BCP results in a significant increase in roughness, although the average shape remained the same. An examination of the thermal behavior of the BCP and the scaling of the free energy suggests that there is greater room for error in patterning a BCP under tension than under compression. This is confirmed by SEM images which show that fingerprint regions appear once the BCP is stretched by 3 %, while no fingerprint regions were found in the compressed end of the sample.
Journal of Polymer Science Part B-Polymer Physics


Sunday, D. , Kline, R. , Ashley, E. , Wan, L. , Patel, K. and Ruiz, R. (2015), Template-Polymer Commensurability and Directed Self-Assembly Block Copolymer Lithography, Journal of Polymer Science Part B-Polymer Physics (Accessed April 15, 2024)
Created April 15, 2015, Updated March 17, 2017