Date of Award
Doctor of Philosophy (PhD)
Chemistry & Biochemistry
Mark P. Stoykovich
Douglas L. Gin
David M. Walba
Self-assembly of block copolymer in thin films provides an attractive approach to fabricating nanoscale dots and lines (5~100 nm) rapidly and in parallel over wafer-scale areas. This PhD dissertation mainly studies using the cross-linking reaction based on epoxide incorporated in copolymers to control the nanostructures of self-assembled block copolymer in thin films.
Although control over the domain orientation and long-range order of block copolymer nanostructures self-assembled in thin films has been achieved using various directed self-assembly techniques, more challenging but equally important for many lithographic applications is the ability to precisely control the shape of the interface between domains. This dissertation details a novel layer-by-layer approach for controlling the interface profile of block copolymer nanostructures, and demonstrates the application of an undercut sidewall profile for an enhanced metal lift-off process for pattern transfer. Bilayer films of lamellar-forming poly(styrene-block-methyl methacrylate) were assembled and thermally cross-linked on wafer substrates in a layer-by-layer process. Undercut or negative sidewall profiles in the PS nanostructures are proven, through electron microscopy and optical transmission measurements, to provide better templates for the lift-off of Au nanowires by achieving complete and defect-free pattern transfer more than 3 times faster than comparable systems with vertical sidewall profiles.
Cross-linking and photopatterning of the self-assembled block copolymer morphologies provide further opportunities to structure self-assembled block copolymer materials for lithographic applications, and to also enhance the thermal, chemical or mechanical stability of such nanostructures to achieve robust templates for subsequent fabrication processes. We demonstrate that self-assembly and cross-linking of the reactive block copolymer materials in thin films can be decoupled into distinct, controlled process steps using solvent annealing and thermal treatment / ultraviolet exposure, respectively. Conventional optical lithography approaches can also be applied to the cross-linkable block copolymer materials in thin films and enables simultaneous structure formation across scales -- micrometer scale patterns achieved by photolithography and lamellar nanostructures with different periods via sequential self-assembly of the smaller symmetric block copolymer on the photopatterned self-assembled symmetric block copolymer in thin film.
He, Chunlin, "Self-assembled Nanostructures in Block Copolymer Thin Films for Nanofabrication" (2014). Chemistry & Biochemistry Graduate Theses & Dissertations. 133.