Feature-scale simulators have been employed to study plasma etching mechanisms, as they provide information that is difficult to obtain experimentally. However, in most simulation studies, the parameters are optimized by matching the simulated profile to the experimental one only at the end of the etching process, leaving open questions about the accuracy of the simulation during the etching process. In this study, we optimize the parameters of a three-dimensional feature-scale simulator, K-SPEED, by matching the time evolution of SiO2 trench features during physical sputtering. The simulation successfully reproduces key characteristics, including facet propagation at the mask, necking at the entrance, and tapering of the etch front. Using the optimized parameters, we further analyze the time evolution of a hole pattern, which is challenging to measure experimentally because the small hole size makes it difficult to slice through the center for cross-sectional inspection. The results reveal that the etch front in the trench reaches a greater depth than in the hole. This difference is explained by analyzing sputtering and redeposition: the redeposited flux in the trench remains bimodal along the opposite sidewalls, whereas in the hole it converges at the center, as the hole is enclosed in all lateral directions. This convergence intensifies passivation, which acts as an inhibitor against etching. These findings provide fundamental insights into geometry-dependent particle transport in high-aspect-ratio features.
Choi et al. (Sun,) studied this question.