Extended model for chemically amplified resist with multiple photoacid generators

The chemically amplified resist, which contains photoacid generator (PAG), has been widely used in high-volume integrated circuit manufacturing. Conventional resist models represent postexposure bake (PEB) as a diffusion-reaction system involving the diffusion, neutralization, and amplification of unitary acid and quencher. However, when the resists with multiple PAGs are introduced for the advanced process, existing models fail to capture the complex chemical interactions of multiple PAGs. In this study, we propose an extended model that accounts for the formulation of multiple PAGs to improve the accuracy of the resist model. Our extended model distinguishes the acid-producing capacity of multiple PAGs and considers the effects of different diffusion, amplification, and neutralization rates on the protection group concentration among different acids. Thus, the model can capture more accurately the dynamics of resist response during the exposure and PEB processes. The exemplary simulations demonstrate that our model can offer superior simulation accuracy compared to the conventional physical model. By calibrating nearly 20 parameters in the proposed model, it achieves 59% and 26% reductions of the root mean square error of critical dimensions with different test patterns. Those results confirm the prediction accuracy of the proposed multi-PAG model, offering a valuable tool for simulating and optimizing the advanced lithography resist formulation.