(393d) Fine Tuning the Interaction Parameter for Sub-10 Nm Block Copolymer Directed Self-Assembly

The directed self-assembly (DSA) of block copolymers (BCPs) is a lithographic process with significant promise for patterning sub-10nm features. Most demonstrations of DSA have utilized polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), however, its low interaction parameter (χ) prescribes a periodicity lower limit of ~ 22 nm. Patterning at smaller length scales will require the design of new materials that follow specific materials design requirements for BCP DSA. First, the BCPs must have equal surface energy between the polymer blocks to enable the formation of features perpendicular to the substrate with thermal annealing. Scaling down feature sizes while maintaining low defect densities is balanced by thermodynamic and kinetic properties of the BCP, which can be characterized by the Flory-Huggins interaction parameter, χ. Smaller features rely on higher values of χ, while it has been previously shown that the energy required for defect annihilation scales with χN. Therefore, in order to balance small feature sizes with low defectivity requirements, χN must lie in a moderate range of 15-20. In order to reach all of these design requirements, we have developed a high-throughput synthetic platform to synthesize library of A-b-(B-r-C) copolymers wherein a homopolymer of A is covalently bonded to a random copolymer of B and C. By tuning the composition of block B to C, we can easily tune χ for a variety of copolymer periodicities. In this presentation, we will show how we can adopt a single nanofabrication workflow to achieve the DSA of our copolymer library with sub-10 nm feature sizes and illustrate how tuning χ can improve the uniformity and roughness of our BCP patterns. We will also highlight a variety of pattern transfer techniques to copy the BCP pattern into other materials, such as silicon, for a variety of applications. We hope this work will uncover a new understanding between copolymer molecular properties and characteristics of the final pattern such as roughness.