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)
Magnetized DC discharges are used in plasma processing for sputtering deposition. Enhanced confinement of electrons is achieved using permanent magnets for magnetron configurations. While such processes are commonly used, the physics are complex and substantial deviations from analytic models are often seen, when such models are even available.
Using a kinetic description of plasmas including collisions with neutrals, particle-in-cell (PIC) methods will be used to accurately model DC discharges, both magnetized and unmagentized. Insight will be gained into the ion energy and angular distributions at the cathode, important to the sputtering deposition process.
Figure 1: Depiction of a DC discharge