Dense self-assembly on sparse chemical patterns: Rectifying and multiplying lithographic patterns using block copolymers

A method to direct the self-assembly of block copolymers to enhance pattern resolution and control CD variation using sparse chemical patterns was investigated. The method provided both resolution enhancement and CD variation control for the guiding resist patterns. The sparse chemical pattern was made from a two-layer system consisting of a thin layer of patterned negative-tone resist on the top of a neutral underlayer made from a crosslinked film of poly(styrene-r-epoxydicyclopentadiene methacrylate). The robustness of the approach was found to be sufficient to allow higher frequency multiplication of the resist spatial frequency. The resolution enhancement and CD variation reduction was further extended to curved features. It was observed that the block copolymer self-assembly, which can form well-defined nanometer-scale features with sharp chemical contrast, may be considered as an additional 'structured' developer that can further rectify poor resist patterns by chemical affinity.