Unraveling the Reaction Mechanisms in a Chemically Amplified EUV Photoresist from a Combined Theoretical and Experimental Approach

TL;DR

This study combines experimental EUV photoemission spectroscopy and first-principles simulations to uncover a novel chemical reaction pathway in EUV photoresists, specifically the breakdown of the photoacid generator, advancing understanding of EUV lithography chemistry.

Contribution

It introduces a combined theoretical and experimental approach to study EUV-induced chemical changes in photoresists, revealing a previously unobserved reaction mechanism.

Findings

EUV-induced breakdown of the photoacid generator was observed.

EUV photoemission spectra linked to PAG degradation.

Combined approach provides insights into chemical dynamics during EUV exposure.

Abstract

Extreme ultraviolet (EUV) lithography has revolutionized high-volume manufacturing of nanoscale components, enabling the production of smaller, denser, and more energy efficient integrated circuit devices. Yet, the use of EUV light results in ionization driven chemistry within the imaging materials of lithography, the photoresists. The complex interplay of ionization, generation of primary and secondary electrons, and the subsequent chemical mechanisms leading to image formation in photoresists has been notoriously difficult to study. In this work, we deploy photoemission spectroscopy with a 92 eV EUV light source combined with first-principles simulations to unravel the chemical changes occurring during exposure in a model chemically amplified photoresist. The results reveal a surprising chemical reaction pathway, namely the EUV-induced breakdown of the photoacid generator (PAG), which is a critical component in the EUV mechanism. This previously unobserved reaction mechanism manifests as changes in intensity of the valence band peaks of the EUV photoemission spectrum, which are linked to degradation of the PAG via an advanced atomistic simulation framework. Our combined experimental and theoretical approach shows that EUV photoemission can simultaneously resolve chemical dynamics and the production of primary and secondary electrons, giving unique insights into the chemical transformation of photoresist materials. Our results pave the way for utilizing accessible, table-top EUV spectroscopy systems for observing EUV photoresist chemical dynamics, with the potential for time-resolved measurements of photoemission processes in the future.