New insights into high electron affinity photoacid generators and their impact on EUV chemically amplified resist performance

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Chemically Amplified Resist (CAR) materials have been engineered to adapt to the decreasing exposure wavelengths in advanced lithography. Significant advancements in Extreme Ultraviolet (EUV) CAR materials have led to improvements in resolution, line edge roughness, and sensitivity (RLS). As CAR-based EUV Lithography (EUVL) becomes essential for high-volume manufacturing, systematic optimization of these materials presents increased opportunities. In this context, stochastic variations in CAR have emerged as critical factors contributing to feature roughness and printing failures at tight pitches. Among the various sources of stochastic variation, EUV photon shot noise poses a substantial challenge. Addressing the drawbacks caused by photon shot noise without increasing the dose can be accomplished by enhancing the efficient utilization of the limited number of EUV photons at practical doses. This includes improving photoacid generation efficiency, which can help minimize uncertainties in acid concentration. In this report, we present findings from a recent study aimed at increasing resist sensitivity. Specifically, we report Density Functional Theory (DFT) modeling results that guided the design of novel Photoacid Generators (PAGs) with a broad range of electron affinity values. By utilizing this modeling approach, we designed and synthesized a series of new ionic PAGs featuring electron-deficient, electroactive cations with remarkably high electron-accepting capabilities. We discuss the correlation between the electronic structure of the newly engineered PAGs and their influence on CAR EUV lithography sensitivity. The implications of this approach for overall EUV lithography patterning performance will also be presented.

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