Non-ionic photo-acid generators for next-generation EUV photoresists

Current leading photoresists depend on ionic Photo-Acid Generators (PAGs) to provide strong acids that enable fast and robust deprotection chemistry. However, these ionic species are often poorly miscible with the hydrophobic organic polymers used in conventional photoresists, resulting in PAG inhomogeneity within the resist film. Non-ionic PAGs have shown improved miscibility and offer an alternative approach, resulting in lower defectivity and improved photosensitivity. Our program is focused on the design and synthesis of a series of non-ionic PAGs for EUV and DUV lithography. By modifying the PAG substitution, we demonstrate that we can tune both the pKa and photoactivity of the labile bond in the PAG, resulting in improved performance. Lastly, we evaluate the performance of the non-ionic PAG designs in both conventional acid deprotection-based photoresist polymers and next-generation photoresists based on an unzipping-type mechanism. Notably, the next-generation photoresists demonstrate faster photospeed in the presence of the non-ionic PAGs-despite their relatively low pKa as compared to currently leading ionic PAGs.