Direct Visualization of Block Copolymer Brush Monolayers in Lithographic Patterns via Metal Oxide Deposition

The directed self-assembly (DSA) of block copolymers (BCPs) is a lithographic process with significant promise for patterning sub-10nm features and for the use of pattern rectification in EUV lithography. Patterning at these small length scales will require both the design of new polymers that follow specific materials design requirements and tailored approaches to DSA. Here we utilize BCPs with A-b-(B-r-C) copolymer architecture which decouple thermodynamic and surface energy properties to allow for DSA via thermal annealing with low defectivity. Through the use of a high throughput, post synthetic modification, we are able to synthesize a library of A-b-(B-r-C) copolymers based on polystyrene-block-poly(glycidal methracylate) copolymers with copolymer periodicities, L₀, between 16-19 nm. While a full set of polymer mat and brushes for conventional DSA is not readily accessible to this new family of A-b-(B-r-C) polymers, we have developed a new, self-brushing chemoepitaxial DSA workflow. The B-r-C random block contains chemical functionality that allows for self-brushing to Si substrates. Through sequential rounds of DSA, the B-r-C domain of the copolymer grafts to the substrate and self-assembles into a phase-separated monolayer with the same spacing as the bulk pattern. We use metal oxide deposition via sequential infiltration synthesis (SIS) as a novel staining mechanism to directly visualize the block copolymer monolayers. The grafted monolayer increasing the guiding pattern of the substrate, resulting “self-healing” of the DSA defects and a large increase in the DSA processing window. We hope this work will uncover a new understanding between copolymer molecular properties and characteristics of the final pattern such as line edge and line width roughness.