Sequential Self-Assembly of Polystyrene--Polydimethylsiloxane for 3D Nanopatterning Solvent Annealing.

This study aims to develop a strategy for the fabrication of multilayer nanopatterns through sequential self-assembly of lamella-forming polystyrene--polydimethylsiloxane (PS--PDMS) block copolymer (BCP) from solvent annealing. By simply tuning the solvent selectivity, a variety of self-assembled BCP thin-film morphologies, including hexagonal perforated lamellae (HPL), parallel cylinders, and spheres, can be obtained from single-composition PS--PDMS. By taking advantage of reactive ion etching (RIE), topographic SiO monoliths with well-ordered arrays of hexagonally packed holes, parallel lines, and hexagonally packed dots can be formed. Subsequently, hole-on-dot and line-on-hole hierarchical textures can be created through a layer-by-layer process with RIE treatment as evidenced experimentally and confirmed theoretically. The results demonstrated the feasibility of creating three-dimensional (3D) nanopatterning from the sequential self-assembly of single-composition PS--PDMS solvent annealing, providing an appealing process for nano-MEMS manufacturing based on BCP lithography.