Ionic Liquid for Directed Self-Assembly of PS-b-PMMA

• Published in: Journal of Photopolymer Science and Technology Vol. 29; no. 5; pp. 667 - 670
• Main Authors: Kawaue, Akiya, Matsumiya, Tasuku, Seo, Takehito, Maehashi, Takaya, Seshimo, Takehiro, Yamano, Hitoshi, Miyagi, Ken, Dazai, Takahiro, Chen, Xuanxuan, Rincon-Delgadillo, Paulina, Gronheid, Roel, Nealey, Paul F., Ohmori, Katsumi
• Format: Journal Article
• Language: English; Japanese
• Published: Hiratsuka The Society of Photopolymer Science and Technology(SPST) 01.01.2016; Japan Science and Technology Agency
• Subjects: Annealing; block copolymer; Block copolymers; directed self-assembly; Free surfaces; High temperature; high χ; Interaction parameters; ionic liquid; Ionic liquids; Ions; L0 shrink; Polymethyl methacrylate; Polystyrene resins; Self-assembly
• ISSN: 0914-9244; 1349-6336
• DOI: 10.2494/photopolymer.29.667

The most widely studied block copolymer (BCP) for directed self-assembly (DSA) is poly(styrene-block-methyl methacrylate) (PS-b-PMMA). However PS-b-PMMA has a limitation of patterning size in sub-10 nm because the Flory-Huggins interaction parameter (χ) of PS-b-PMMA is approximately 0.038 at room temperature. To obtain sub-10 nm patterning size, many high χ BCPs and systems have been studied. We investigate DSA of PS-b-PMMA with blended an ionic liquid (IL) via thermal annealing with free surface under nitrogen. L0 becomes larger than pure BCP by adding ILs in this system since χ parameter becomes higher. However there is a problem that long time (>30 min) and/or high temperature (>200 oC) annealing conditions causes L0 shrink than in mild annealing condition (200 oC /1 min). Here, we report IL design to prevent L0 shrink. The design of IL that we found in this study achieved less than 5 % L0 shrink at 215 oC for 30 min annealing.