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

Abstract

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.

Thickness-Controlled Phase Transitions of AB Diblock Copolymers in Asymmetric Ultrathin Films

“…Interestingly, the lamella-forming block copolymer film deposited on the plateaus gave rise to a morphology whose top view is a hexagonal “dot” pattern. This behavior was attributed to the local film thickness, the asymmetric surface affinities, and the topographical substrate. , Nevertheless, the formation mechanism of the hexagonal dot pattern by the lamella-forming block copolymer needs to be further elucidated theoretically.…”

“…This behavior was attributed to the local film thickness, the asymmetric surface affinities, and the topographical substrate. 46,47 Nevertheless, the formation mechanism of the hexagonal dot pattern by the lamella-forming block copolymer needs to be further elucidated theoretically.…”