Dry-Etching Processes for High-Aspect-Ratio Features with Sub-10 nm Resolution High-χ Block Copolymers

Directed self-assembly of block copolymers (BCP) is a very attractive technique for the realization of functional nanostructures at high resolution. In this work, we developed full dry-etching strategies for BCP nanolithography using an 18 nm pitch lamellar silicon-containing block copolymer. Both an oxidizing Ar/O₂ plasma and a nonoxidizing H₂/N₂ plasma are used to remove the topcoat material of our BCP stack and reveal the perpendicular lamellae. Under Ar/O₂ plasma, an interfacial layer stops the etch process at the topcoat/BCP interface, which provides an etch-stop but also requires an additional CF₄-based breakthrough plasma for further etching. This interfacial layer is not present in H₂/N₂. Increasing the H₂/N₂ ratio leads to more profound modifications of the silicon-containing lamellae, for which a chemistry in He/N₂/O₂ rather than Ar/O₂ plasma produces a smoother and more regular lithographic mask. Finally, these features are successfully transferred into silicon, silicon-on-insulator, and silicon nitride substrates. This work highlights the performance of a silicon-containing block copolymer at 18 nm pitch to pattern relevant hard-mask materials for various applications, including microelectronics.