Creating Customized Patterns using Block Copolymer Directed Self-Assembly for Integrated Circuit Fabrication
HGST, a Western Digital Company
The directed self-assembly (DSA) of block copolymers (BCPs) has attracted significant interest as an extension to state-of-the-art lithography by enhancing resolution and improving dimensional uniformity. Typically, DSA offers a limited set of dense and highly periodic patterns. However, many applications require more complex, patterns customized according to design. At the scale of useful BCP features, this necessity for pattern customization tests ultimately exceeds the limits in both resolution and overlay accuracy for lithography tools. This talk will discuss recent advances toward customizable nanoscale fabrication based on the DSA of lamellae-forming polystyrene-block-poly (methyl methacrylate) thin films using underlying, partially inorganic chemical guiding patterns. To establish pattern placement tolerances, the first measurements of BCP feature registration with underlying guiding patterns are enabled by introducing pattern symmetry-breaking, in situ registration marks. These measurements reveal correlations affecting DSA placement accuracy and permit estimation of the minimum placement error possible. Furthermore, a new route to create customized BCP patterns is introduced by encoding chemical patterns with inorganic guiding lines and non-guiding “masking” features. Subsequent DSA and pattern transfer results in line-space gratings with gaps between lines and trim across lines dictated by the placement of guiding lines and masking features, respectively. Thermodynamic analysis reveals the rules governing chemical pattern and process design in order to achieve defect-free BCP assembly. This self-aligned, bidirectional customization scheme affords new opportunities for high-resolution, circuit-relevant patterning using DSA.
Gregory Doerk is a research staff member at HGST, investigating the fabrication of nanoimprint templates with sub-10 nm rectangular feature dimensions for patterned magnetic media, as well as new magnetic read and write head designs. He received his B.S. from Case Western Reserve University, and his Ph.D. in Chemical Engineering from the University of California, Berkeley. He performed his postdoctoral research at the IBM Almaden Research Center in block copolymer directed self-assembly for next-generation lithography, where he invented a new patterning process that is the basis for much of IBM’s ongoing efforts using block copolymers. Gregory’s research interests are centered on the intersection of “top down” and “bottom up” chemical processes for nanotechnology applications, and have spanned topics that include nanostructure synthesis, nanowire thermal characterization, and directed self-assembly processes.