Block copolymer lithography provides an attractive route to the fabrication of nanoscale structures in functional materials such as metals, semiconductors, or dielectrics (e.g., metallic nanowire interconnects or inorganic magnetic bits).  The domain orientation and long-range order of block copolymer nanostructures self-assembled in thin films can be 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.  We have developed a layer-by-layer approach for controlling the interface profile of block copolymer nanostructures, and demonstrated an undercut sidewall profile for lift-off processes for pattern transfer.  Bilayer films of lamellar-forming poly(styrene-block-methyl methacrylate) were assembled and cross-linked on wafer substrates in a layer-by-layer process.  The top layer, while being directed to self-assemble on the lamellae of the underlying layer, had a tunable composition and polystyrene domain width independent from the underlying layers.  Undercut or negative sidewall profiles in the PS nanostructures, as shown through electron microscopy and optical transmission measurements, to yield better templates for the lift-off of Au nanowires by achieving complete and defect-free pattern transfer ~3-fold faster than comparable systems with vertical sidewall profiles.  More broadly, this layer-by-layer approach may enable sophisticated interface profiles and user-defined three-dimensional block copolymer nanostructures in thin films.

Interfacial profile control in cross-linkable block copolymers for improved pattern transfer

249th National Meeting (2015)

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