Photo-Reconfigurable Azopolymer Etch Mask: Photofluidization-Driven Reconfiguration and Edge Rectangularization.

Directional photofluidization of azobenzene materials has provided unprecedented opportunities for the structural reconfiguration of circular holes, line gaps, ellipsoidal holes, and nanofunnel-shaped micro/nanoarchitectures. However, all the reconfigured structures have a parabolic or round wall due to the tendency of the photofluidized azobenezene materials to minimize the surface area, which limits their use as a reconfigurable etch-mask for the lithography process. In this work, a simple method is presented that can change the round walls of azopolymer architectures into rectangular walls, which is named rectangularization. By irradiating far-field light on reconfigured azopolymer in a conformal contact with a flat polydimethylsiloxane (PDMS) film, the round wall transforms to a rectangular one because the azopolymer adheres along the PDMS surface while being photofluidized. As a result, the rectangularization process creates a variety of structural features and sizes ranging from a few micrometers to 150 nm having a rectangular wall. By exploiting the rectangularization process, the concept of a photo-reconfigurable etch mask is achieved, which transfers the mask patterns to a silicon pattern with a high structural fidelity and imparts a considerable flexibility to the lithography process.