Optimized Solvent Vapor Annealing for Long-Range Perpendicular Lamellae in PS-b-PMMA Films

We report a simple approach to fabricating highly stable, perpendicularly oriented lamellae through the self-assembly of high-molecular-weight polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). Using a solvent vapor annealing (SVA) process controlled by modulating the temperature gap between the chamber and bottom plate, followed by a subsequent thermal annealing process, the ordering stability of perpendicularly oriented lamellae was investigated. The temperature gap that regulates the solvent absorption and dewetting times of the swollen block copolymer (BCP) films was adjusted to enable the films to wet a neutral substrate, thereby facilitating ordering and structural development with no ordering failure. An optimized SVA process at a selected temperature gap of 5 °C was found to display the excellent long-term stability, at which highly ordered line arrays composed of perpendicularly oriented lamellae were confined to large-width (3.2 μm) topographic line patterns. This study also provides the effective time window for the SVA process, suggesting a simple and efficient route to fabricating long-range lateral ordering in BCP self-assembled structures.