Engineering Block Copolymer/Homopolymer Blend Assembly Pathways for Nanopattern Optimization

Photon shot noise and resist noise pose significant challenges to continued density scaling for nanopatterns printed using extreme ultraviolet lithography. By using lithographic patterns as chemical templates to direct the placement of block copolymer (BCP) domains, directed self-assembly (DSA) offers a promising corrective for maintaining high yields despite lithographic stochasticity by multiplying pattern density and/or reducing pattern roughness and variability at scales smaller than the nanopattern pitch. This application of BCP DSA requires both rapid ordering kinetics to completely remove assembly defects (e.g., dislocations) and sharp domain interfaces for optimal pattern smoothing. These requirements, however, entail using BCPs which are weakly or strongly segregated, respectively. This talk will present a potential solution to this dilemma using a two-step annealing process to engineer assembly pathways for symmetric neat BCPs and their blends with homopolymers. The first step involves controlled exposure to a solvent vapor with near neutral selectivity to both BCP blocks, resulting in a weakly segregated BCP system allowing for rapid self-assembly with low defectivity. In the second step the samples are thermally annealed to enable short-range polymer chain rearrangement that sharpens domain interfaces under strong segregation conditions. Importantly, the added homopolymers act as plasticizers for enhancing kinetics in the first step and can redistribute more rapidly within a domain than the BCP chains in the second step, imparting more flexibility for assembly process design. Using combinatorial spray deposition, high-throughput grazing-incidence small-angle x-ray scattering (GISAXS), and electron microscopy, we survey key assembly and pattern properties including pitch, domain interface width, pattern order and defectivity, and line roughness across a range of blend compositions and annealing conditions. Elaborating the relationship between structural properties, composition, and annealing processes for both directed and undirected assembly enables the identification and selection of optimal assembly pathways for DSA.