Modeling the charging effect of the hardmask and silicon substrate during plasma etching in advanced nodes

Abstract

Profile non-idealities after plasma etching negatively affect the performance of advanced node devices. The charging effect is a well-known mechanism affecting the hardmask and substrate profiles. Unfortunately, directly characterizing this phenomenon in practical processes is extremely challenging. In this article, we propose a novel etching model to overcome this challenge by incorporating algorithms that simultaneously account for charging effects and particle reflection mechanisms. The model is able to reproduce the real-time profile evolution of both hardmask and substrate layers in an advanced nanoscale etching process. We calculate the electric field distribution induced by the surface charges accumulated on the hardmask, which affects both the trajectory of individual incident ions and the overall etching profiles. To validate our approach, we perform experiments of Si etching in Cl₂ plasma and compare the simulated profiles with scanning electron microscope images. The model also identifies the impact of the charging effect on profile defects, such as mask faceting, substrate bowing, and microtrenching. This work provides insights into the charging effect mechanism and its influence on the etching profile, ultimately providing new knobs for advanced process development and optimization.