Deprotection reaction kinetics in chemically amplified photoresists determined by sub-millisecond post exposure bake

Abstract

Chemically amplified photoresists require a post exposure bake (PEB) to induce deprotection using a UV generated acid-catalyst. While reaction pathways for deprotection have been proposed, key challenges remain in modeling the reaction kinetics. In this work, we used a scanning line-focused laser beam as an alternate PEB method, to quantify the deprotection reaction kinetics of an ESCAP-type and a 193 nm model resist system at high temperatures in millisecond time frames. Results were compared with conventional PEB at 115°C for seconds time frames. Results show that the deprotection kinetics follow simple first-order reaction models only under laser PEB conditions, with more complex kinetics observed under hot plate PEB. FT-IR and NMR spectroscopies were used to characterize the reaction byproducts. Results suggest potential differences in deprotection mechanisms between the two PEB temperature and time regimes. The deprotection behavior obtained using this l-PEB technique enables a deeper understanding of the reaction kinetics of photoresists, critical for current DUV and future EUV technologies.