Marangoni-Driven Patterning in Polymer Thin Film Supported on Shrinking Substrate for Resolution Enhancement

Abstract

The Marangoni effect causes liquids to flow toward localized regions with higher surface tension. In a polymer thin film, the flow induced by photochemically programmed surface tension gradients can be harnessed to manufacture patterned surfaces. Patterned polymer films are particularly useful for controlling adhesion, improving photonic device efficiency, and directing cellular alignment. In general, a broader range of accessible pattern resolutions and/or aspect ratios ensures a broader range of applications. However, because of the process flow for pattern formation, the final pattern periodicity of the Marangoni-driven features matches that of the initially prescribed surface energy pattern. To achieve better resolution without using sophisticated and complex tools, a shrinking (or pre-strained) polymer film was used as a substrate. The shrinking substrate could “contract or densify” the features along the substrate plane. Consequently, the resolution of the patterns formed on the shrinking substrate was improved by the shrinkage rate of the substrate compared with those formed on the non-shrinking substrate (i.e., silicon wafer).