(112i) UV Solvent Annealing for Morphology and Orientation Control in Self-Assembled PS-PDMS Thin Films

Block copolymers (BCPs) are of interest in nanotechnology because of their ability to self-assemble into two- and three-dimensional morphologies on the order of 10 nm. This is beyond the resolution limit of optical lithography and can be achieved more economically and efficiently than is possible with methods such as electron beam lithography and top-down patterning. However, the success of self-assembly is limited by the difficulty of controlling long range order and feature aspect ratio. Solvent vapor annealing is an effective method to control self-assembly in block copolymer films; however the swollen film morphology collapses when the solvents are removed. Therefore, ultraviolet (UV) curing was introduced into the solvent vapor annealing process to cross-link the block copolymer to preserve the structure in the swelled state. UV solvent vapor annealing facilitated BCP self-assembly, minimized defects, and increased the uniformity of self-assembled features of thin films of 53 kg/mol cylinder-forming polystyrene-polydimethylsiloxane (PS-PDMS) block copolymer (SD53). The UV-exposure-induced polymer cross-linking effectively preserved the self-assembled morphology swollen state and prevented structural collapse from fast solvent removal, resulting in a more uniform and well-ordered morphology.