Three-dimensional modeling of EUV photoresist using the multivariate Poisson propagation model

Background: As target feature sizes for EUV lithography shrink, it is becoming ever more important to understand the intricate details of photoresist materials, including the role of the “third dimension”—the dimension perpendicular to the wafer. With resist thicknesses shrinking toward the single-digit nanometer scale alongside target linewidths, small changes in resist performance in this dimension will have a greater overall effect on pattern quality. Aim: To use modeling to understand the effect that the third dimension has on resist performance, in particular the interplay between the third dimension and resist stochastics. Approach: We developed a three-dimensional version of the multivariate Poisson propagation model, a stochastic resist simulator. As a test case for the model, we explore the role of acid diffusion in the so-called third dimension by simulating 105 vias at a series of z-blur conditions. Results: Our model suggests that increased z-blur yields an improvement in both dose to size and pattern uniformity without sacrificing resolution. Conclusions: We have developed a 3D resist model that can simulate large numbers of contacts. Early results from the 3D model show improved patterning performance can be achieved by increasing the z-blur.