Dual frequency discharges give independent control of ion bombarding energy and plasma density. A high frequency RF source, between 20-80 MHz, controls the plasma density, while a low frequency RF source, between 1-20 MHz, sets the sheat bias and ultimately the ion impact energy. Particle-in-cell (PIC) simulations will be used to characterize the performance of such devices, including kinetic and nonlinear effects. Collisions with background gas are modeled with a Monte Carlo collision (MCC) model, including electron-neutral scattering, excitiation, ionization, and ion-neutral scattering and charge exchange.
One dimensional cylindrical simulations run in a matter of hours, and allow asymmetric electrodes. Preliminary PIC-MCC results compare favorably with global models. Two dimensional simulations are planned to correctly model the grounded third electrode (wall) of realistic ion etch reactors.
1Graduate Student (non-EECS)