(4bi) Block Copolymer Patterns Replicated By Photochemical Transfer Printing
Thin films of block copolymers are promising patterning templates for next generation microprocessors, hard drives, bio-arrays, and separation membranes because they rapidly self-assemble into periodic structures with characteristic feature sizes of 1-100 nm. However, guiding patterns must be employed in order to direct the self-assembly of BCP thin films into prescribed, device-oriented patterns or regular arrays with long-range order. Fabrication of these guiding patterns requires performing lithographic patterning with resolution near that of the BCP periodicity, which can be a relatively lengthy and expensive process step. Therefore, strategies to replicate the patterns formed with BCP thin films onto other substrates while recovering the original for more replication cycles could be practically useful because the guiding pattern would only have to be fabricated once. Here a procedure is described that uses light as an externally applied stimuli to facilitate the transfer printing of BCP top surface patterns from one substrate to another. Because photo-polymerizable liquid conformal layers are placed between the samples, the pattern is replicated continuously and over large areas. The strategy has been used to replicate patterns with periodicities as small as 20 nm, as well as films in which the self-assembled structures have been directed by an underlying guiding pattern. Additionally, efforts to improve process throughput and conformal layer uniformity will be described.