Time dependent behavior of chemically amplified resist characterized under sub-millisecond post exposure bake

Chemically amplified photoresists require a post exposure bake (PEB) to catalytically deprotect the polymer backbone. However, excessive difiiision of the photo-generated acid during PEB results in resolution loss and line edge roughness. As both deprotection and diffusion are thermally activated processes, understanding their reaction kinetics as a function of temperature and time is potentially key to optimizing these two competing processes. In this work, we characterize the resist deprotection kinetics under laser PEB (/-PEB), utilizing continuous wave CO₂ laser thermal processing to shift the duration into sub-millisecond time frames at temperatures up to 500°C. At these temperatures and times, the extent of deprotection under /-PEB is comparable to that observed under conventional hot plate PEB conditions in the second time frames. Results show that, under isothermal conditions, deprotection has a power law dependence as a function of PEB duration, exhibiting second-order or higher order kinetics under second time frames but a first-order kinetics under /-PEB in sub-millisecond times.