Passive inference of collision frequency in magnetized capacitive argon discharge

We demonstrate a self-consistent and complete description of electron dynamics in a typical electropositive radio frequency magnetron sputtering (RFMS) argon discharge with a dielectric target. The electron dynamics, including the electron power absorption dynamics in one radio frequency (RF) period, is studied via a fully kinetic 2d3v particle-in-cell/Monte Carlo collision (PIC/MCC) electrostatic simulation. The interplay between the fundamental plasma parameters is analyzed through their spatiotemporal dynamics. Due to the influence of magnetic trap on the electron transport, a spatially dependent charging that perturbs the electric potential is observed on the dielectric target surface, resulting in a spatially dependent ion energy distribution along the target surface. The E × B drift-to-discharge current ratio is in approximate agreement with Bohm diffusion. The electron power absorption can be primarily decoupled into the positive Ohmic power absorption in the bulk plasma region and the negative pressure-induced power absorption near the target surface. Ohmic power absorption is the dominant electron power absorption mechanism, mostly contributed by the azimuthal electron current. The power absorption due to electron inertial effects is negligible on time-average. Both the maximum power absorption and dissipation of electrons appear in the bulk plasma region during the second half of the RF period, implying a strong electron trapping in magnetron discharges. The contribution of secondary electrons is negligible under typical RFMS discharge conditions.

Section: Introductionmentioning

confidence: 99%

Electron dynamics in radio frequency magnetron sputtering argon discharges with a dielectric target

Zheng

Wang

et al. 2021

“…mode transition, and more wave modes arise more easily at higher pressures. This might be because, as the pressure is increased, collisions between the heated electrons and neutrals become more frequent, resulting in a shorter electron mean free path, which reduces electron transport parallel to the magnetic field and leads to a higher plasma density [32][33][34].…”

Section: Ne-p Rf At Different Pressuresmentioning

confidence: 99%

“…The effect of the magnetic field on the density variation is similar to the pressure. As the magnetic field is increased, plasma confinement in the radial direction is improved, causing a significant increase in the plasma density [17,33,34,39].…”

Section: Ne-p Rf In Different Bmentioning

confidence: 99%

The wave mode transition of argon helicon plasma

Cui,

Zhang,

et al. 2024

In this paper, multiple wave modes and transitions of argon helicon plasma excited by a half right-helical in a system without any reflection endplate are investigated experimentally and theoretically at increasing radio frequency (RF) powers and external magnetic fields. Experiments show that above a critical magnetic field strength and pressure (about 250 G and 0.3 Pa in this work), two to four distinct wave coupled modes and transitions were observed at increasing RF powers and/or magnetic fields. Theoretical analysis based on dispersion relationship show that in high magnetic field helicon wave of the lowest order of axial eigenmode is always excited firstly, then the higher order axial or radial mode, hence the plasma density increases after mode jumping. There are two mechanisms responsible for the wave mode transitions in the present system, i.e., axial and radial mode transitions owning to the change of axial and radial wavenumbers from a lower eigenmode to a higher one. Higher plasma density and magnetic field are helpful for achieving more higher-order modes of helicon waves.

“…The ion dynamics are barely affected due to their much larger mass. Over several decades, a series of theoretical [5][6][7][8][9][10][11][12][13][14][15][16][17] and experimental [18][19][20][21][22][23][24][25] investigations demonstrated the prominent performance of magnetized CCRF plasmas in enhancing power deposition.…”

Section: Introductionmentioning

confidence: 99%

Resonant electron confinement and sheath expansion heating in magnetized capacitive oxygen discharges

Sun

Zhang

Schulze

et al. 2023

In weakly magnetized capacitive radio frequency (RF) plasmas electrons accelerated into the plasma bulk by the expanding RF boundary sheath at one electrode can be returned to this electrode due to their gyromotion around an externally applied magnetic field oriented parallel to the electrodes. If the driving frequency and magnetic field are chosen so that the electron cyclotron frequency, ωce, equals half of the driving radio frequency, ωrf, such energetic beam electrons will be returned to the sheath during its expansion phase and, thus, will be confined and heated resonantly. This Magnetized RF Sheath Resonance (MRSR) effect is studied based on kinetic particle-in-cell simulations in weakly magnetized capacitively coupled oxygen plasmas. In comparison with electropositive argon plasmas, this resonance mechanism is found to be affected strongly by the electronegativity of oxygen discharges. In the unmagnetized case, low-pressure capacitive oxygen discharges operate in an electropositive mode, where nonlinear high-frequency sheath oscillations play an important role similar to previous observations in electropositive discharges with low electron densities. If the resonance condition is fulfilled (ωce/ωrf=1/2), the discharge efficiency is enhanced due to the MRSR effects, resulting in an increase in plasma density. Our numerical results demonstrate that this resonance effect is particularly efficient at low pressure and low electronegativity. However, in strongly electronegative discharges, the time it takes a typical resonant electron to return to the expanding sheath edge is found to be affected by drift and ambipolar electric fields in the plasma bulk, which cause a deviation from the resonance condition, resulting in a reduction of this type of resonance effect.