Ph. Belenguer

Numerical model of an ac plasma display panel cell in neon‐xenon mixtures

We present a self‐consistent 1D model of the discharge initiated in an ac plasma display panel cell. The model is based on a two‐moments fluid description of electron and ion transport, coupled with Poisson’s equation, and with a set of kinetic equations characterizing the evolution of the population of excited states leading to UV emission in neon‐xenon mixtures. Results are presented in a 90% neon, 10% xenon gas mixture, for a gap length of 100 μm and a gas pressure of 560 Torr at ambient temperature. Under the conditions above, and for typical sustaining voltages, the duration of the discharge current pulse predicted by the model is on the order of 10 ns while the UV emission lasts for about 5 μs. The UV production efficiency in the discharge is about 10% for a Ne‐Xe (90‐10) mixture. Results for other neon‐xenon mixtures are also discussed. The model also shows that a non‐negligible part of the UV production occurs in the transient ‘‘plasma column’’ and not only in the sheath region. Voltage transfer c...

Transition from a capacitive to a resistive regime in a silane radio frequency discharge and its possible relation to powder formation

Self‐consistent fluid and particle‐in‐cell models of radiofrequency glow discharges have been used to analyze the existence of different regimes experimentally observed in silane discharges. The discharge ionization mechanism changes from a situation where the ionization occurs during the expansion of the sheath to a situation where the bulk plasma plays a major role. We suggest that the transition is consistent with powder formation with increasing power. This leads to supplementary losses of electrons and then to an increase in the plasma electric field.

The concept of plasma cleaning in glow discharge spectrometry

A plasma cleaning procedure to improve elemental depth profiling of shallow layered materials by glow discharge spectrometry is proposed. The procedure is based on two approaches applied prior to depth profiling, either individually or sequentially. The first approach employs a plasma generated at low power, i.e. a “soft” plasma, for removal of contaminants adsorbed on the surface of the target material. In the second approach, sacrificial material is sputtered under normal conditions, e.g. those used for depth profiling, to clean the inner surface of the anode of the glow discharge source. It is demonstrated that plasma cleaning in glow discharge optical emission spectrometry and glow discharge time-of-flight mass spectrometry improves significantly the spectrum of the target material, particularly at the commencement of sputtering due to stabilisation of the plasma as a result of removal of contaminants. Furthermore, modelling and validation studies confirmed that the soft plasma cleaning does not sputter the target material.

Fundamental Properties of RF Glow Discharges: An Approach Based on Self—Consistent Numerical Models

Non thermal plasmas such as those generated by DC or RF glow discharges are attractive for plasma chemistry due to their ability to achieve high temperature chemistry at low gas temperature. In DC or RF glow discharges, the electrons carry the energy which is necessary to excite, dissociate or ionize the gas molecules and to create reactive species. The resulting plasma can be chemically reactive both in the gas phase and with the surfaces exposed to it. An important application of reactive plasma concerns the microelectronics industry and is related to VLSI (very large scale integration) processing.

Effect of anisotropy in the elastic scattering cross sections on the ionization source terms in glow discharges in argon

The main purpose of this work is to evaluate, using a Monte Carlo simulation, the extent to which anisotropy in the elastic electron-neutral scattering cross sections influences the spatial distribution of the electron-impact ionization profile in glow discharges in argon. We also briefly discuss the effect of anisotropic elastic scattering on the slowing down of an electron beam and on the transmission factor, the fraction of electrons emitted from the cathode that are not scattered back to the cathode. Monte Carlo simulations were performed using different functional forms for the anisotropy. We show that, for a given momentum transfer cross section and the assumption of isotropic scattering, the ionization profiles over a range of conditions in argon glow discharges in parallel plane electrode geometries are not significantly affected by the inclusion of higher order anisotropies in the elastic cross sections. The anisotropy in the elastic scattering cross section influences only slightly the electron ...

Modelling of discharges and non-thermal plasmas—applications to plasma processing

Abstract We present an overview of models of low pressure, non-thermal gas discharges as commonly used in plasma processing. Significant progress has been made in the past decade towards the goal of a self-consistent model of the electrical properties of discharges, whether d.c., r.f. or microwave discharges. These models are based on solutions of the charged particle transport equations coupled with Poissons equation for the electric field, and provide the space and time distribution of charged particle densities, current densities and electric field or potential. Some of the most sophisticated models also provide the electron and ion velocity distribution functions in the discharge at any point in space or time. It is now possible to describe reasonably accurately the physical properties of a discharge (including the plasma, the electrode regions and the walls) for two-dimensional cylindrical geometries, even for complex electrode configurations involving e.g. a hollow cathode or anode. A survey of the available models is presented here and we illustrate the current state of the art by results from one- and two-dimensional models of d.c., and transient discharges.

Numerical Model Of An Ac Plasma Display Panel Cell In Neon Xenon Mixtures

We present a self-consistent 1D model of the discharge initiated in an ac plasma display panel cell. The model is based on a two-moments fluid description of electron and ion transport, coupled with Poisson’s equation, and with a set of kinetic equations characterizing the evolution of the population of excited states leading to UV emission in neon-xenon mixtures. Results are presented in a 90% neon, 10% xenon gas mixture, for a gap length of 100 ,um and a gas pressure of 560 Torr at ambient temperature. Under the conditions above, and for typical sustaining voltages, the duration of the discharge current pulse predicted by the model is on the order of 10 ns while the UV emission lasts for about 5 p. The UV production efficiency in the discharge is about 10% for a Ne-Xe (90-10) mixture. Results for other neon-xenon mixtures are also discussed. The model also shows that a non-negligible part of the W production occurs in the transient “plasma column” and not only in the sheath region. Voltage transfer curves and margin obtained with this model are presented and compared with available experimental measurements.

Impact of the cathode material on the analytical glow discharge

RF-Glow Discharge Optical Emission Spectrometry is a well established technique for direct compositional depth profiling (CDP) analysis of solid, conducting and non-conducting samples. The technique is based on sputtering surface atoms and their subsequent excitation in the discharge1. The separation of sputtering and excitation makes the technique very little prone to matrix effects. The quantification procedure is based on the observation that emission yields depend strongly on the source impedance, which varies with the carrier gas density and the secondary electron emission yield of successively sputtered layers. Despite the apparent success1, it lacks theoretical back-up and its extension to non-conductive materials is difficult.

Power Deposition in Low Pressure, Capacitively Coupled RF Discharges

Capacitively coupled rf discharges are routinely used to produce plasmas for etching and deposition in semiconductor device fabrication. For example, the deposition of thin films of amorphous silicon for solar panels is a well-developed technology based on plasma production in rf excited discharges. The current efforts to improve device fabrication technologies involve developing a better understanding of the plasmas produced and their interactions with the surfaces. This requires an understanding of the rf discharge itself and the mechanisms of electrical power deposition in the gas. Intensive efforts in modeling and diagnosing rf plasmas over the past ten years have led to considerable progress in the understanding of the power deposition mechanisms in these discharges. Models ranging from simple equivalent circuits to sophisticated particle simulation techniques have been used and a consistent picture is emerging from the various models and the experimental results which provides a basis for understanding and optimizing rf discharges to enhance certain plasma properties (see the recent issue of IEEE Transactions on Plasma Science edited by Kushner and Gravest for an overview of the ongoing research in this active area). In this article we present model results to illustrate the range of phenomena determining the power deposition which come into play in these discharge conditions.