Facile Enhancement of Etching Selectivity in Block Copolymer Patterns via Surface-Localized SiO₂ Shielding Layer

Block copolymer (BCP) self-assembly offers a scalable route for nanoscale patterning in electronic and optical devices. However, conventional BCP systems like Polystyrene-block-polydimethylsiloxane (PS-b-PDMS) often face challenges in achieving high aspect ratio patterns due to limited etching selectivity and pattern instability during dry etching. In this study, we introduce a simple strategy to enhance etching selectivity by blending a small amount of PS-b-PDMS into Polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) films. Thermal annealing induces PS-b-PDMS migration to PS domains, forming a surface-localized shielding layer. During plasma etching, this layer is converted into an inorganic SiO2 layer, improving plasma resistance. This approach increases etch depth by∼25% while maintaining perpendicular lamellar alignment. Importantly, it does not require complex processing steps such as solvent annealing or surface modification. The strategy provides a practical and scalable method to achieve high-fidelity, high aspect ratio nanopatterns with enhanced etching performance suitable for large-area applications.