Kinetic simulations of low-temperature plasmas used for plasma processing: ICP and feature-scale models

Low-temperature kinetic plasma simulations using Particle-in-Cell (PIC) and Monte Carlo methods (DSMC/MCC) for the chemistry can provide many advantages over fluid simulations, including detailed information about the Ion Energy Distribution Function (IEDF) and Ion Angular Distribution Function (IADF) that are critical for plasma processing. In this presentation, two different types of simulations illustrating the advantages of kinetic modeling are demonstrated. The first is a macroscopic-scale simulation of an Inductively Coupled Plasma (ICP). We demonstrate how implicit methods can make these challenging simulations feasible, and how process parameters such as neutral gas density and bias frequency affect the IEDF and IADF at the wafer surface. We also demonstrate a method of providing constant power to the plasma which decreases run-times to reach steady state and examine the steady-state ion fluxes and IEDFs/IADFs incident on the wafer as a function of bias frequency and waveform shape. Secondly, we discuss efforts to develop microscopic feature-scale simulation capabilities, e.g. for through-silicon vias or other high-aspect-ratio etch features wherein the trajectories of etching species may be affected by charge accumulation on feature sidewalls. Here, our recent efforts have focused on the development of self-consistent flux boundary conditions from macroscopic (sheath)-scale simulations that can be used as inputs for such feature-scale simulations.