Optimization of ion energy distribution and ion angular distribution by tuning chamber radius in inductively coupled plasma etching

A two-dimensional discharge model integrating fluid dynamics and electromagnetic field modules was developed to simulate ion energy and incident angle distributions in an inductively coupled plasma etching device, equipped with a focus ring and coil around an expansion chamber. Simulation results reveal the presence of an etching edge effect, which is that both ion energy and incident angle exhibit increased divergence near the wafer edge. This phenomenon is attributed to nonuniform plasma density in the expansion chamber, leading to inhomogeneous sheath thickness. By adjusting the driving chamber radius (Rd), the study demonstrates that Rd will influence the plasma density distribution and sheath thickness uniformity, thereby altering the ion transit time through the sheath. Consequently, the uniformity of the ion energy distribution and ion incident angle distribution is significantly affected. While Rd improves ion uniformity under specific conditions, its optimal value depends on both operating parameters and device geometric dimension. In this work, we illustrate this dependence using chamber height and process pressure as representative examples, with detailed results provided in the supplementary material.