Validation of Hybrid Electron Particle-In-Cell (PIC)-Ion Fluid Plasma Simulation Methodology for Low Pressure Capacitively Coupled Plasma (CCP) Chambers

Low-pressure (< 30 mTorr) capacitively coupled plasma (CCP) plasma sources provide the energetic sheaths that are vital in high-energy dielectric etching and high-quality film deposition applications. The kinetic behavior of electrons at low pressure cannot be adequately captured in the widely used fluid plasma models. The particle in cell (PIC) simulation methodology that accurately captures plasma behavior in this pressure range incurs prohibitively high computational cost especially when the chamber dimensions are large. In this paper, we present a hybrid PIC fluid simulation methodology where electrons are assumed to be particles while ions are treated as fluid where computational cost is reduced substantially due to reduced number of particles. The hybrid simulation methodology is compared against full PIC methodology for verification and the results are validated using experimental data. Ar, O₂, and their mixtures are simulated in a low-pressure axisymmetric single and dual-frequency RF powered CCP chamber. In this chamber, ion currents and ion energy distribution functions are measured at the grounded electrode using relatively calibrated field energy analyzer sensors for different process conditions along with the corresponding bulk plasma density at different radial positions using a Langmuir probe. We validate our hybrid PIC-fluid simulations using these measurements and discuss the computational advantages and disadvantages of the proposed methodology over full PIC modeling.