Microscopic Mechanisms of Reaction-Coupled Acid Diffusion in Chemically Amplified Photoresists

Diffusion in photoresists is a fundamental process that significantly impacts micro-nano manufacturing. However, it often intertwines with chemical reactions, leading to intricate kinetics that compounds our comprehension. Here, we successfully applied all-atom molecular dynamics simulations to simultaneously describe the diffusion of acids and the deprotection reactions they catalyze in extreme ultraviolet photoresists, which are critical materials for high-resolution patterning. The results show that acids hop between binding sites with the aid of the other species present in photoresists, akin to observations of ion transport in organic electrolytes. The deprotection reactions enable acids to overcome spatially prohibitive barriers. These chemical reactions also create local free volume, facilitating the motion of the organic matrix and consequently promoting acid movement. We show that by simultaneously describing diffusion and chemical reactions, atomic-level simulations can reproduce the features of experimental reaction dynamics, highlighting the potential of molecular modeling in advancing photoresist design. These insights broaden our understanding of diffusion in organic solids and serve as a theoretical reference in the development of photoresists for higher performances.