Electron kinetics in capacitively coupled plasmas modulated by electron injection

Abstract

The controlling effect of an electron injection on the electron energy distribution function (EEDF) and on the energetic electron flux, in a capacitive radio-frequency argon plasma, is studied using a one-dimensional particle-in-cell/Monte Carlo collisions model. The input power of the electron beam is as small as several tens of Watts with laboratory achievable emission currents and energies. With the electron injection, the electron temperature decreases but with a significant high energy tail. The electron density, electron temperature in the sheath, and electron heating rate increase with the increasing emission energy. This is attributed to the extra heating of the energetic electrons in the EEDF tail. The non-equilibrium EEDF is obtained for strong non-local distributions of the electric field, electron heating rate, excitation, and ionization rate, indicating the discharge has transited from a volume heating (a-mode dominated) into a sheath heating (c-mode dominated) type. In addition, the electron injection not only modifies the self-bias voltage, but also enhances the electron flux that can reach the electrodes. Moreover, the relative population of energetic electrons significantly increases with the electron injection compared to that without the electron injection, relevant for modifying the gas and surface chemistry reactions.

Electron energy probability function modulation with external electron beam in capacitive coupled radio frequency discharges

“…Therefore, kinetic method, that is, the particle‐in‐cell/Monte‐Carlo‐collision (PIC/MCC) method, can cast some new lights in this problem. Previously, we have studied the kinetic impact of a thermal electron injection, from a rf powered electrode, in a rf argon discharge, where high density and high energetic (5 eV) electron flux is generated, as both the electron density and temperature increase. This energetic electron flux provides high energy delivering to the electrode, relevant for plasma‐surface chemistry, but is not preferred in plasma processing.…”

Numerical characterization of dual-frequency capacitively coupled plasmas modulated by electron beam injection

“…Modulation schemes to control the characteristic parameters of CCP mainly include dual-frequency (DF) or multi-frequency CCP [1,[5][6][7][8][9][10][11][12][13], hybrid CCP [14][15][16][17][18], external magnetic fields [19,20], electron beam (EB) injection CCP [21][22][23][24][25][26][27][28][29], and ion beam injection [30]. Recently, EB-driven approaches have gained considerable attention.…”

A novel capacitively coupled plasma driven by hollow cathode radio-frequency discharges

“…The hollow cathode discharge can only occur when the ion secondary emission coefficient is greater than 0.1. And the EB can improve ionization, increase plasma density, reduce ion energy, and modulate the energy distribution of electrons [19][20][21][22]. By numerical simulation, Haas et al found that electron temperature and energy distribution can be suppressed due to the high energy tail provided by the EB [19].…”

“…By numerical simulation, Haas et al found that electron temperature and energy distribution can be suppressed due to the high energy tail provided by the EB [19]. And the effects of the electron beam injected into CCP from the powered electrode and grounded electrode on modulation of the energy distribution were investigated, respectively, using a 1D PIC/MC simulation, by Zhang et al [20,21]. It was reported that compared with conventional CCPs, electron density skyrockets when the EB is injected, and the population of energetic electrons increases, too.…”