Opportunities and Challenges for Directed Self-Assembly for Advanced Patterning

Directed self-assembly (DSA) of block copolymers (BCPs) is a promising technology for advanced patterning at future technology nodes, but significant hurdles remain for commercial implementation. The most widely studied material for DSA is poly(styrene-block-methyl methacrylate) (PS-PMMA), but the relatively weak segregation strength of PS-PMMA results in some limitations. This paper reports on these limitations for PS-PMMA and highlights a path to success through use of more strongly segregated "high-chi" block copolymers. In general, stronger segregation is predicted to lower defectivity at equilibrium, but unfortunately, kinetics of self assembly also becomes much slower as segregation strength increases. Recognizing diffusion is much faster for cylinder morphologies than lamellar ones, we have investigated new cylinder-forming BCPs that enable defect elimination with thermal annealing processes. In addition, a formulation strategy is presented that further improves the kinetics of the assembly process, enabling tremendous improvements in defectivity over simple BCP systems. Excitingly, successful chemoepitaxy DSA with a high-chi lamellar BCP is also demonstrated using a thermal annealing process and no top coat. These technologies hold promise to enable DSA with thermal annealing processing across pitches from 40 - 16 nm.