Implementation of Directed Self-Assembly (DSA) as a viable lithographic technology for high volume manufacturing
will require significant efforts to co-optimize the DSA process options and constraints with existing work flows. These
work flows include established etch stacks, integration schemes, and design layout principles. The two foremost
patterning schemes for DSA, chemoepitaxy and graphoepitaxy, each have their own advantages and disadvantages.
Chemoepitaxy is well suited for regular repeating patterns, but has challenges when non-periodic design elements are
required. As the line-space polystyrene-block-polymethylmethacrylate chemoepitaxy DSA processes mature,
considerable progress has been made on reducing the density of topological (dislocation and disclination) defects but
little is known about the existence of 3D buried defects and their subsequent pattern transfer to underlayers. In this
paper, we highlight the emergence of a specific type of buried bridging defect within our two 28 nm pitch DSA flows
and summarize our efforts to characterize and eliminate the buried defects using process, materials, and plasma-etch
optimization. We also discuss how the optimization and removal of the buried defects impacts both the process window
and pitch multiplication, facilitates measurement of the pattern roughness rectification, and demonstrate hard-mask open
within a back-end-of-line integration flow. Finally, since graphoepitaxy has intrinsic benefits in terms of design
flexibility when compared to chemoepitaxy, we highlight our initial investigations on implementing high-chi block
copolymer patterning using multiple graphoepitaxy flows to realize sub-20 nm pitch line-space patterns and discuss the
benefits of using high-chi block copolymers for roughness reduction.