Non-Bulk Morphologies of Extremely Thin Block Copolymer Films Cast on Topographically Defined Substrates Featuring Deep Trenches: The Importance of Lateral Confinement

Directed self-assembly of block copolymers is evolving toward applications that are more defect-tolerant but still require high morphological control and could benefit from simple, inexpensive fabrication processes. Previously, we demonstrated that simply casting ultra-thin block copolymer films on topographically defined substrates leads to hierarchical structures with dual patterns in a controlled manner and unraveled the dependence of the local morphology on the topographic feature dimensions. In this article, we discuss the extreme of the ultraconfined thickness regime at the border of film dewetting. Additional non-bulk morphologies are observed at this extreme, which further elaborate the arsenal of dual patterns that could be obtained in coexistence with full placement control. It is shown that as the thickness confinement approaches its limit, lateral confinement imposed by the width of the plateaus becomes a critical factor influencing the local morphology.

Automated summary

By simply casting ultra-thin block copolymer films on topographically defined substrates, hierarchical structures with dual patterns can be achieved in a controlled manner, offering enhanced defect tolerance and simplified fabrication processes. The extreme of ultraconfined thickness regime at the border of film dewetting reveals additional non-bulk morphologies, expanding the possibilities for obtaining dual patterns alongside full placement control. The width of the plateaus becomes a critical factor influencing the local morphology as the thickness confinement approaches its limit.