Invited Talk: Photochemical Reactions for Replicating and Aligning Block Copolymer Thin Film Patterns

New methodologies for patterning micro- and nano- scale features in polymer thin films are desired because of their high technological relevance to a range of applications, including microelectronics fabrication. Here recent research will be described where light is used to photochemically replicate the patterns on the surface of block copolymer thin films. In general, directed self-assembly (DSA) of block copolymers (BCPs) could potentially complement or even supplant existing photolithographic techniques, but requires high-resolution guiding patterns to direct the block copolymer self-assembly into device-oriented structures over large areas. A facile replication procedure of the guiding patterns could increase the overall throughput of DSA given that making the original chemical guiding patterns can be relatively slow. Our strategy involves placing benzophenone-containing liquid compositions between the top surface of a block copolymer thin film and a transparent substrate. Upon irradiation the liquid composition solidifies and covalently binds to the BCP, thus creating a mirror-image copy of the original pattern on the transparent substrate. This replicated pattern serves to direct the assembly of a new BCP thin film, while the patterned wetting characteristics of the original substrate are recovered for use in further replication cycles. The process is scalable to large areas, takes less than 1 h, and occurs below the glass transition of the BCP.