Controlled Anisotropic Wetting by Plasma Treatment for Directed Self-Assembly of High‑χ Block Copolymers

• Published in: ACS applied materials & interfaces 2024-05, Vol.16 (21), p.27841-27849
• Main Authors: Putranto, Achmad Fajar, Petit-Etienne, Camille, Cavalaglio, Sébastien, Cabannes-Boué, Benjamin, Panabiere, Marie, Forcina, Gianluca, Fleury, Guillaume, Kogelschatz, Martin, Zelsmann, Marc
• Format: Article
• Language: English
• Subjects: Physics; Surfaces, Interfaces, and Applications
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.4c01657

The directed self-assembly (DSA) of block copolymers (BCPs) is a promising next-generation lithography technique for high-resolution patterning. However, achieving lithographically applicable BCP organization such as out-of-plane lamellae requires proper tuning of interfacial energies between the BCP domains and the substrate, which remains difficult to address effectively and efficiently with high-χ BCPs. Here, we present the successful generation of anisotropic wetting by plasma treatment on patterned spin-on-carbon (SOC) substrates and its application to the DSA of a high-χ Si-containing material, poly­(1,1-dimethylsilacyclobutane)-block-polystyrene (PDMSB-b-PS), with a 9 nm half pitch. Exposing the SOC substrate to different plasma chemistries promotes the vertical alignment of the PDMSB-b-PS lamellae within the trenches. In particular, a patterned substrate treated with HBr/O2 plasma gives both a neutral wetting at the bottom interface and a strong PS-affine wetting at the sidewalls of the SOC trenches to efficiently guide the vertical BCP lamellae. Furthermore, prolonged exposure to HBr/O2 plasma enables an adjustment of the trench width and an increased density of BCP lines on the substrate. Experimental observations are in agreement with a free energy configurational model developed to describe the system. These advances, which could be easily implemented in industry, could contribute to the wider adoption of self-assembly techniques in microelectronics, and beyond to applications such as metasurfaces, surface-enhanced Raman spectroscopy, and sensing technologies.