Time Dependent Behavior of Chemically Amplified Resist Characterized under Sub-millisecond Post Exposure Bake

Abstract

Chemically amplified photoresists require a post exposure bake (PEB) to catalytically deprotect the polymer backbone. However, excessive diffusion of the photogenerated 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 (lPEB), 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 l-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 secondorder or higher order kinetics under second time frames but a first-order kinetics under lPEB in sub-millisecond times.