Particle-in-cell modeling of electron beam generated plasma

Abstract

Plasmas generated using energetic electron beams are well known for their low electron temperature (Te) and plasma potential, which makes them attractive for atomic-precision plasma processing applications such as atomic layer etch and deposition. A 2-dimensional particle-in-cell (PIC) model for an electron beam-generated plasma in Argon confined by a constant applied magnetic field is described in this article. Plasma production primarily occurs in the path of the beam electrons in the center of the chamber. The resulting plasma spreads out in the chamber through non-ambipolar diffusion with a short-circuit effect allowing unequal electron and ion fluxes to different regions of the bounding conductive chamber walls. The cross-field transport of the electrons (and thus the steady-state characteristics of the plasma) are strongly impacted by the magnetic field. Te is anisotropic in the electron beam region, but low and isotropic away from the plasma production zone. The plasma density increases, and the plasma becomes more confined near the region of production when the magnetic field strengthens. The magnetic field reduces both electron physical and energy transport perpendicular to the magnetic field. Te is uniform along the magnetic field lines and slowly decreases perpendicular to it. Electrons are less energetic in the sheath regions where the sheath electric field repels and confines the low-energy electrons from the bulk plasma. Even though electron and ion densities are similar in the bulk plasma due to quasi-neutrality, electron and ion fluxes on the grounded chamber walls are unequal at most locations. Electron confinement by the magnetic field weakens with increasing pressure, and the plasma spread out farther from the electron beam region.

Study of synchronous RF pulsing in dual frequency capacitively coupled plasma

“…EDIPIC is open source and available on GitHub with the necessary documentation [20]. EDIPIC has been described recently by Rauf et al [21]. It uses a standard explicit leap-frog algorithm in Cartesian geometry, with the Boris scheme for particle advance [22].…”

Oblique streaming waves observed in multipactor-induced plasma discharge above a dielectric surface

“…Cross sections for these reactions are sourced from [6,7,67,68]. All the physical processes described above have been implemented in a well-benchmarked 2D Electrostatic Direct Implicit Particle-In-Cell (EDIPIC) code [66,[68][69][70][71], which has been used widely in low-temperature plasma studies such as radio-frequency plasma discharge [72,73], gas breakdown [67,74] and electron beam-generated plasma [68,70,75,76]. And such model is well validated against experimental measurements [77,78] and theoretical calculation [1] in terms of the threshold electric fields for the onset of multipactor phenomenon, and saturated surface charge densities from other PIC simulation [79].…”