Acid diffusion detection in chemically amplified photoresists

Previous studies applied PAG-containing topcoats to PAG-free ArF resists with exposure and PEB, but the film thickness loss strategy lacked clarity on acid diffusion gradients and ion-pair transport at layer interfaces. This work uses GCIB ToF-SIMS depth profiling to monitor PAG distributions in top-coated bilayer structures before/after processing for different PAG formulations, analyzing interfacial ion-pair transport dynamics. Results show that different sized anions in CARs modulate acid diffusion lengths, optimizing lithographic performance via nanoscale control of acid transport kinetics. The influence of resin structure and PDI on photoacid diffusion was also systematically investigated, and the results confirmed that the regulation of photoacid diffusion cannot be simply achieved by PDI alone. The study provides molecular-level insights into acid diffusion mechanisms by bilayer model, guiding high-performance photoresist design.