Investigation of the Structure-Asymmetry Effects on Plasma Uniformity in a Capacitively Coupled Etching Reactor Using Two-Dimensional Particle-in-Cell and Fluid Simulations

The particle-in-cell (PIC) and fluid simulations are widely used in low-temperature capacitively coupled plasma equipment for semiconductor manufacturing processes. The fluid simulation has the advantage in treating complex gas chemistry but is inaccurate in a non-local regime where electron energy relaxation length (λε) is longer than the characteristic length (l) of the system. The non-local electron kinetics is observed primarily for low-pressure etching reactors. The asymmetric effects caused by the electrode shape and the sidewall can be considered only in multi-dimensional simulation. In this research, a two-dimensional PIC simulation analyzes the electron dynamics in symmetric and asymmetric structures. Asymmetric charge distributions on the electrode edge and the sidewall induces a radial electric field to form a radial electron flux, which affects the uniformity. We found that the non-local kinetics causes plasma nonuniformity, especially for a long electrode ^[1]. In the high-pressure regime (λε &lt; l), both PIC and fluid simulation show local kinetics. As a result, we suggest the criterion for choosing a simulation method when investigating plasma properties.<br/>[1] Chang Ho Kim <i>et al.</i>, <i>Plasma Sources Sci. Technol.</i> <b>30</b>, 065031 (2021).