Physics of Radio-Frequency Plasmas (original) (raw)

Numerical Studies of the Low Pressure RF Plasma

ANU, 1990

A one-dimensional, electrostatic particle-in-cell code with non-periodic boundary conditions is used to simulate a low pressure capacitive rf plasma created between two planar electrodes. Ion and electron motion is included and ionising collisions by energetic electrons allow a steady state to be reached and maintained. Realistic values of mi/me are used but there is no attempt to model a real gas and, except for ionisation, no binary collision processes are considered. The simulation plasma is generated by driving one boundary with a sinusoidal rf voltage at a frequency of 10 MHz. The effects of scaling on the steady state, the structure and the impedance of the resulting discharge are investigated. Changes resulting from varying the amplitude of the driving voltage are examined and scaling laws for the plasma potential, electron density and power loss obtained. Sheath heating is shown to be the main electron heating process and power balance is checked. The structure of the rf sheath obtained in the simulation is compared to theoretical models of both the current driven and the voltage driven sheath. Disagreement in the maximum sheath width between the simulation and the model is ascribed to neglect of the period of sheath collapse and the use of an idealised electron density profile in the model. Sheath scaling is shown to underlie the variation of electron density and temperature with rf voltage. The electron sheath interaction is examined and found to differ considerably from current theoretical models. In the range of parameters investigated, it is essential to consider the distortion of the electron velocity distribution in the sheath. A beam-like distribution is observed when the sheath velocity changes rapidly near the time of sheath collapse and an instability develops when electrons are accelerated into the plasma as the sheath expands.

Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments

Plasma Physics and Controlled Fusion, 2012

Capacitive radio frequency (RF) discharge plasmas have been serving hi-tech industry (e.g. chip and solar cell manufacturing, realization of biocompatible surfaces) for several years. Nonetheless, their complex modes of operation are not fully understood and represent topics of high interest. The understanding of these phenomena is aided by modern diagnostic techniques and computer simulations. From the industrial point of view the control of ion properties is of particular interest; possibilities of independent control of the ion flux and the ion energy have been utilized via excitation of the discharges with multiple frequencies. 'Classical' dual-frequency (DF) discharges (where two significantly different driving frequencies are used), as well as discharges driven by a base frequency and its higher harmonic(s) have been analyzed thoroughly. It has been recognized that the second solution results in an electrically induced asymmetry (electrical asymmetry effect), which provides the basis for the control of the mean ion energy. This paper reviews recent advances on studies of the different electron heating mechanisms, on the possibilities of the separate control of ion energy and ion flux in DF discharges, on the effects of secondary electrons, as well as on the non-linear behavior (self-generated resonant current oscillations) of capacitive RF plasmas. The work is based on a synergistic approach of theoretical modeling, experiments and kinetic simulations based on the particle-in-cell approach.

AN INTRODUCTION TO BASIC PHENOMENA OF PLASMA PHYSICS

Shabd Publication, 2020

Plasma is a set of neutral and charged particles which reveals a number of collective behaviors. The very long range coulomb forces enable the charged particles in plasma to work together with one another simultaneously. The study of plasma is actually a really ancient area of investigation in plasma physics and it remains to be among the vital fields due to the crucial role of its in most plasma uses including plasma processing, fabrication of semiconductor systems, etching, etc. except the presence of just ions and electrons, the plasma in many instances, has a number of other species of ions like negative ions which impact the complete plasma behaviour. Within this paper we study about the fundamental ideas of plasma physics.

Conductivity of rf-heated plasma

1984

The electron velocity distribution of rf-heated plasma may be so far from Maxwellian that Spitzer conductivity no longer holds. A new conductivity for such plasmas is derived and the result can be put in a remarkably general form. The new expression should be of great• practical value in examining schemes for current rarap-up in tokamaks ' by means of lower-hybrid or other waves. DISCLAIMER This report i n prepared as an account of work sponsored by an agency of the United States Government.

Pattern Formation in Low-Pressure Radio-Frequency Plasmas due to a Transport Instability

Physical Review Letters, 2019

Pattern formation, observed experimentally in a radio-frequency plasma in annular geometry, and characterized by azimuthal symmetry breaking of the plasma parameters, is reported. The azimuthal modulation increases with increasing pressure in the range 1-300 Pa. These experimental observations are accurately described by a fluid model in which the transport coefficients are computed from a 0D Boltzmann kinetic equation. A linear stability analysis shows that unstable modulations develop at low and intermediate pressures, following an instability mechanism due to an energy transport effect-the instability mechanism lies in the sign of off-diagonal terms for the electron particles and energy fluxes expressed as functions of gradients of the plasma density and the electron temperature. This model is an excellent candidate to explain the occurrence of striations in radio-frequency plasmas.

Micro-arcing in radio frequency plasmas

Journal of Physics D: Applied Physics, 2004

Micro-arcing and breakdown of the wall plasma sheath in radio frequency (RF) plasmas is studied in a hollow cathode system, using a Langmuir probe to measure the floating potential. Micro-arcing was induced reproducibly by controlling the floating potential. By dc grounding the hollow cathode, a negative current can flow to ground resulting in a higher voltage sheath between the plasma and the earthed vacuum vessel. The wall arcing threshold of the plasma potential in this system is in the vicinity of 50 V. In the present system, the charging process to rebuild the plasma potential, which is about a few tens of milliseconds, is much slower than the microsecond discharge. The arcing frequency was found to depend strongly on the plasma potential and the pressure. We propose a mechanism for the dependence of the frequency of periodic micro-arcing based on the development of electron field emission sites. The measurement of floating potential is suggested as a useful parameter to monitor and prevent micro-arcing in RF plasmas.

Plasma Physics Division ( P ) Overview Plasma Physics Division ( P )

2010

P 4.1 Tu 11:40–12:10 B 305 Experiments and Simulations of Dusty Plasmas — ∙Andre Melzer P 4.2 Tu 12:10–12:40 B 305 Electrostatic microparticle propulsion for space flights — ∙Thomas Trottenberg, Viktor Schneider, Holger Kersten P 11.1 We 11:00–11:30 B 305 Intermittent plasma transport — ∙Thomas Windisch, Olaf Grulke, Thomas Klinger P 11.2 We 11:30–12:00 B 305 Structure formation in drift-wave turbulence — ∙Peter Manz, Mirko Ramisch, Ulrich Stroth P 11.3 We 12:00–12:30 B 305 Dynamic behaviour of dc discharges — ∙Detlef Loffhagen, Florian Sigeneger P 11.4 We 12:30–13:00 B 305 The numerical simulation of diffuse axial magnetic field vacuum arcs — ∙Andreas Hauser, Werner Hartmann, Andreas Lawall, Roman Renz, Norbert Wenzel P 15.1 Th 11:00–11:30 B 305 Hydrogen retention in tungsten from laboratory experiments to ITER — ∙Matej Mayer, Olga Ogorodnikova, Volker Rohde, Joachim Roth, pwi team, asdex upgrade team P 15.2 Th 11:30–12:00 B 305 Active control of tokamak instabilities by resonant m...

Recent Progress in Understanding the Physics of Plasma-Filled, High-Power Microwave Sources

AIP Conference Proceedings

The use of plasmas for generating high-power microwaves is studied for more than 50 years. During the 1990's Plasma-Assisted Slow-wave Oscillators (PASOTRONs) were invented and actively developed at Hughes Research Lab (HRL). These devices have a number of unique and attractive features. However, the experiments at HRL showed that to explore these features a better understanding of the physics is necessary. The present paper is focused on the recent studies of various physical issues, which are important for the pasotron operation. This theoretical and experimental activity resulted in more than doubling the pasotron efficiency (from about 20% to more than 50%) in the experiments carried out at the University of Maryland. CP625, High Energy Density and High Power RF: 5' * Workshop, edited by B. E. Carlsten