Designing Stable Photoresists Using Polymers With Photoinduced Reversible Solid‐to‐Liquid Transitions for Nanoimprint Lithography

Photoresists for nanoimprint lithography are critical materials for the fabrication of semiconductors, optical metamaterials, and flexible electronics. However, conventional photocuring-based photoresists are unstable to heat and ambient light, complicating their usage, storage, and transport. Furthermore, their irreversible photocuring nature renders defects in imprinted nanostructures permanent and complicates the cleaning of photoresist-contaminated molds. Herein, we overcome these limitations by designing azopolymer photoresists exhibiting photoinduced reversible solid-to-liquid transitions. Compared to conventional photoresists, the azopolymer photoresists exhibited superior thermo- and photostability. An azopolymer photoresist stored in our laboratory for over 10 years remained usable for nanoimprint lithography, demonstrating exceptional long-term stability. Additionally, the photoinduced reversible solid-to-liquid transitions of azopolymer photoresists enable defect correction in imprinted nanostructures. The linear chain structure of azopolymer photoresists facilitates the cleaning of photoresist-contaminated molds using solvents. The photoresists developed in this work combine long-term stability and high-resolution patterning, offering a promising approach among existing azo-based lithography strategies. This work demonstrates that azopolymers with photoinduced reversible solid-to-liquid transitions are stable photoresists with defect-correction and mold-cleaning capabilities for nanoimprint lithography.