Polymerizable Nonionic Perfluorinated Photoacid Generators for High-Resolution Lithography

Advanced photoresists must satisfy stringent sensitivity requirements while maintaining the ability to print ever-shrinking critical dimensions. However, the unavoidable acid diffusion associated with chemically amplified photoresists has led to a trade-off between resolution, line-edge roughness, and sensitivity, which presents a significant challenge for high-resolution lithography. To address this issue, a novel class of alkene-functionalized nonionic perfluorinated photoacid generators (PAGs) is developed. These fluorine-rich compounds significantly enhance the photochemical reactivity due to the introduction of abundant F-elements, thereby improving sensitivity. Upon irradiation by ultraviolet light or electrons, they generate long-chain perfluorinated sulfonic acids with large sizes and minimal diffusion ranges, effectively suppressing acid diffusion. Furthermore, by employing these polymerizable PAG monomers, PAG-bound polymers are synthesized that are likely to achieve higher resolution by minimizing acid diffusion. Lithography performance demonstrated patterning of sub-45 nm lines at an electron beam dose of 29 µC cm^-2. Overall, the developed perfluorinated PAGs and PAG-bound polymer photoresists are promising candidates for achieving high-sensitivity and high-resolution nano-patterning.