Understanding block copolymer dynamics and mobility is critical for achieving perfection in polymer nanopatterns, a goal for fundamental science as well as technology applications. Here, we utilize temperature-controlled atomic force microscopy (AFM) to directly observe the dynamics and directed self-assembly of topographically-confined polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) in situ and above the glass transition temperature. Topographically confining the block copolymer in nanoscale lithographic channels induces global order in the polymer nanopattern: PMMA preferentially interacts with the silicon substrate, causing the domains to align with the channel walls and propagating linear alignment throughout the channel, thus providing control over the degrees of freedom and defect density in the polymer patterns. Imaging under these experimentally challenging thermal annealing conditions opens in situ observation and measurement of block copolymer dynamics and self-assembly, including interfacial fluctuations, pattern roughness, and defect behavior and annihilation. Moreover, even in perfectly aligned films, disorder persists in the form of thermal fluctuations at the interface between the polymer domains. Overall, this work seeks to understand how structural defects influence thermal fluctuations of the polymer pattern, and how this disorder defines the limits of perfection in polymer patterns.

Seeking perfection in polymer nanopatterns: In situ imaging of block copolymer dynamics with environmentally controlled high-speed AFM

ACS Fall 2021

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