Beam plasma discharge at low magnetic field as plasma source for plasma processing reactor

The aims of the research are to study the nature of an effect detected earlier for the formation of ion flows from a beam plasma discharge and to determine possible applications of this effect. These flows propagate in a beam plasma discharge on a normal to the discharge axis. It has been found that the acceleration of ions is a consequence of the potential gradient between an area with a high level of microwave oscillations and a peripheral area of plasma. The results of physical experiments qualitatively correlate with computer simulation data. The analysis of the physical mechanism of the effect has enabled a way of effective control of the flow energy and density to be found. The capability to change the mean energy of the ion flow in the range from 20 up to 70 eV with increase in its density by an order has been demonstrated. A possible application of the effect is a novel plasma processing reactor for treatment of materials used in electronics engineering. In particular, soft etching technology of AlGaAs barrier layers in semiconducting AlGaAs/InGaAs/GaAs heterostructures has been demonstrated.     

Vacuum lithography using plasma polymerization and plasma development

A completely dry lithography has been proposed which involves plasma polymerization of methyl methacrylate (MMA) and plasma development with CCl₄. It was called vacuum lithography because all processes were performed in a vacuum. However, the developed pattern had a lower resolution than patterns produced by conventional lithography with a wet process. After several technical refinements, the quality of the resist and the developed pattern was markedly improved. In this paper, recent results will be reported.A gas-flow-type reactor was used instead of a bell-jar-type reactor because the morphology of plasma-polymerized MMA (PPMMA) varied with each experimental run which was performed with the same gas and discharge parameters. The monomer vapour was introduced downstream of the argon discharge, and the polymerized film was formed on the substrate placed further downstream in the mixed gas.The development of pattern was performed by etching with an Ar-O₂ mixture and with hydrogen gas instead of CCl₄ gas, because the etching rate of the resist was too high in a CCl₄ plasma and a clear pattern was not obtained. The evaluated sensitivity and γ value of PPMMA were 1000 μC cm^?2 and 1 respectively. MMA containing 5% tetramethyltin was also used as a monomer gas for plasma polymerization downstream of the argon discharge. In this case the sensitivity and γ value were 10 μC cm^?2 and 2 respectively.     

Multiphase electric-arc ac plasma generators for plasma technologies

Multiphase electric-arc ac plasma generators with a power of 10 to 500 kW are described, which are designed for use in plasma technologies. Results are given of the investigation of the characteristics of plasma generators for different operating modes, and the basic principles of operation of such plasma generators are described.     

Chemical-reaction dependence of plasma parameter in reactive silane plasma

Electron temperature in a silane glow-discharge plasma, being an important plasma parameter for determining photo-induced instability in the resulting hydrogenated amorphous silicon (a-Si:H), has been studied under various film-preparation conditions. We have used an optical-emission-intensity ratio of Si^* to SiH^* (I_si*/I_siH^*) which corresponds to the high-energy-tail slope of the electron-energy-distribution function in the plasma as a measure of electron temperature in a reactive silane glow-discharge plasma. We have found quite differently from the conventional non-reactive glow-discharge plasma such as hydrogen plasma that the electron temperature in the silane plasma is strongly modified by the substrate temperature (gas temperature) especially under high silane-gas partial-pressure condition. This anomalous behavior of the electron temperature in the silane plasma has been explained by means of gas-phase-polymerization reaction and electron-attachment process to the polymers in the plasma. The electron temperature has been remarkably reduced when a hydrogen-dilution method and a cathode-heating method are used which are considered to control polymer-formation reactions in the silane plasma together with utilization of conventional electron-temperature-controlling methods such as a very high plasma-excitation frequency and an application of magnetic field for electron-confinement. As a consequence of the reduction of electron temperature in the silane plasma, highly stabilized a-Si:H has been successfully obtained even under high growth rate conditions of 1.5 nm s^-1.     

A magnetic acceleration plasma facility for plasma shock peening

Set-up, function and application potential of pulsed magnetoplasmadynamic self-field accelerators are described. The focus is on the facility MAX (Magnetoplasmadynamic Accelerator-eXperiment). Here, a high power coaxial accelerator is investigated regarding space propulsion and processes aiming for metal treatment as potential applications.A certain amount of gas is accelerated via magnetic fields while the overall kinetic energy of the plasma has to be maximized. During plasma generation numerous parasitic effects are associated with the discharge of the device. Hence, the characterization of the facility in terms of power balance, functional behaviour and kinetic energy of the plasma is mandatory. The kinetic energy is of importance for both space propulsion and the mentioned plasma material treatment processes. Electrodynamic properties enabling the simulation with a snowplow model have been determined experimentally. The model provides a relation between the plasma movement and the electrodynamic properties. Results of the model are current and voltage histories but also statements on the kinetic energy of the plasma. Based on this calorimeters were designed, manufactured and integrated using adequate measurement technology, e.g. fast thermocouples and an infrared camera allowing for the determination of the temporal and spatial temperature histories on the calorimeters. A thermal analysis model was developed and applied to the calorimeter and compared with the measurements. Hence, the thermal energy could be determined which consequently led to an efficiency of 12% for a load voltage of 12 kV and an ambient pressure of 10⁻⁵ mbar.     

Stress-induced plasma volume change determined using plasma FT-IR spectra

Our purpose was to determine the plasma-volume (PV) change induced by a physical stress independent of the metabolic events that may interfere with physiological fluid shifts in to and out of the intravascular space. Our methods included using 178 exercise tests of varying duration and intensity for determination of PV change during exercise. Plasma Fourier transform infrared (FT-IR) spectra were used to compare hematocrit change to the total spectral area (4000-500 cm(-1)) and the protein and albumin concentration changes induced by exercise. Our results showed that exercise induced a raise in protein (+10.4 +/- 3.1%) and albumin (+9.8 +/- 3.3%) concentrations that significantly correlated with PV change (14.1 +/- 5.2% of plasma volume; P = 0.05 with protein and albumin concentration changes). However, evolution of the total spectral area obtained from rest-plasma (524 +/- 21 a.u.) and exercise-plasma (611 +/- 26 a.u.; +14.1 +/- 4.8%) FT-IR spectra showed a higher correlation level with PV change (r = 0.98; P = 0.005; S(x/y) = 1.26 a.u.). It is our conclusion that although exercise-induced changes in protein and albumin concentrations were found to correlate with PV change, the use of the total spectral area of the plasma FT-IR spectra allowed a more precise measurement of PV change.     

Chemical-reaction dependence of plasma parameter in reactive silane plasma

Electron temperature in a silane glow-discharge plasma, being an important plasma parameter for determining photo-induced instability in the resulting hydrogenated amorphous silicon (a-Si:H), has been studied under various film-preparation conditions. We have used an optical-emission-intensity ratio of Si¹ to SiH¹ (I_Si¹/I_SiH¹) which corresponds to the high-energy-tail slope of the electron-energy-distribution function in the plasma as a measure of electron temperature in a reactive silane glow-discharge plasma. We have found quite differently from the conventional non-reactive glow-discharge plasma such as hydrogen plasma that the electron temperature in the silane plasma is strongly modified by the substrate temperature (gas temperature) especially under high silane-gas partial-pressure condition. This anomalous behavior of the electron temperature in the silane plasma has been explained by means of gas-phase-polymerization reaction and electron-attachment process to the polymers in the plasma. The electron temperature has been remarkably reduced when a hydrogen-dilution method and a cathode-heating method are used which are considered to control polymer-formation reactions in the silane plasma together with utilization of conventional electron-temperature-controlling methods such as a very high plasma-excitation frequency and an application of magnetic field for electron-confinement. As a consequence of the reduction of electron temperature in the silane plasma, highly stabilized a-Si:H has been successfully obtained even under high growth rate conditions of 1.5 nm s⁻¹.     

Hydrocarbon plasma emission as a means to monitor plasma polymerization

A diagnostic feature of the optical emission from a toluene glow discharge is the relative intensities of the aromatic benzyl radical V spectrum band and the aliphatic CH A ²Δ-X ²Π band system. The evaluation of the relative intensities of these emissions allows a prediction of the chemical structural characteristics of the deposited polymer film which is independent of the reactor power level, pressure or flow rate.     

Production of low electron temperature ECR plasma for plasma processing

Low-electron-temperature ECR plasma with high electron density was realized under the mirror magnetic field configuration in the H₂ and the Ar/N₂ plasma. Especially, the electron temperature was observed to be less than 2 eV in the Ar/N₂ plasma. It was found from the calculation of particle and power balance in steady state that the decrease in the electron temperature observed in the Ar/N₂ plasma was due to the effect of the magnetic-mirror confinement of the N₂ plasma. Furthermore, our calculated results suggest that the effect of magnetic-mirror on the decrease in the electron temperature depends on the collisional cross section between electrons and neutral particles.     

A cold plasma cross made of three bullet-like plasma plumes

In contrast to other atmospheric pressure plasma jets, two perpendicular jet-like plasmas generated in ambient air by a special designed plasma device are reported. High-speed photographs taken by an ICCD camera with exposure time of 2 ns show that the horizontal part of the plasma is actually ignited by the vertical part of the plasma. Both the vertical and horizontal parts of the plasma are in fact a small bullet like volume of plasma traveling along different directions at high velocities. The horizontal plasma volume velocity is about half of the vertical plasma volume velocity at the same instant.     

Study on plasma discharge parameters in double-glow plasma surface alloying furnace

Double Langmuir probe technique was used for plasma diagnostics of discharge process in double-glow plasma alloying furnace. Investigated that the effect of changes of voltage of the source pole and air pressure on plasma parameters. Results show that plasma density increases, electron temperature decreases and potential of the probe decreases, with the rise of voltage of the source pole under condition of fixed cathode potential and fixed air pressure. During increasing of air pressure in furnace, electron temperature decreases and probe potential increases. The change of probe potential is smart at start of the measuring and probe potential goes to stabilization only when degas process goes to finishing.     

High speed plasma diagnostics for laser plasma interaction and fusion studies

Laser plasma interaction and fusion studies involve many high speed plasma diagnostics to determine the various parameters for explaining the physical processes taking place in plasma. Detection and analysis of short-term or transient radiations (X-ray and visible) are the bases for diagnosing the physical processes occurring during laser-plasma interaction or similar radiation-emitting processes. This paper reviews the development of various high speed plasma diagnostics which are not only applicable in determining the temporal, spatial and spectral properties of X-rays for this purpose but also have wide use in various other fields of research.     

A case of plasma component exchange using membrane plasma separator EVACURE™

Purpose:  Performed free coagulant hemodialysis to patients having hemorrhage with the hope to avoid aggravation of bleeding caused by anticoagulant agent from dialysis. Method:  Examined 19 cases of patients with bleeding tendency, whether it is possible to perform free coagulant hemodialysis by using PAES membrane, EVAL membrane, PS membrane, Cellulose triacetate membrane and Vitamin‐E modified‐dialysis membrane. Result:  With PAES membrane, the result showed a non‐ blockade rate of 91% after four hours and 100% after two hours. Therefore, blockade was prevented with a fairly high rate. In cases of blockade, most of them were possibly avoidable with a little contrivance as the reason were lack of establish blood flow rate, faulty position of a needle, etc. Conclusions:  By using PAES membrane, it was possible to perform free coagulant hemodialysis. In order to completely have no blockade of blood lines in the future, we must strive further on.     

Theory of plasma chemical transport etching of gold in a chlorine plasma

The behavior of the reactive ion etching of gold in a chlorine plasma reported earlier is shown in this paper to be interpretable in terms of a theory of chemical vapor transport, modified to account for the effect of species generated in the plasma and transported across the plasma sheaths to the reacting surfaces. The interpretation of the experiments in terms of such a theory is required because the volatile compound of gold generated at the etched surface must be transported to another surface where it is consumed by a reaction which is the reverse of etching, and gold is deposited. It is shown that the mass transport of the volatile product is not only due to the differences in temperature between the surfaces where the reactions occur, but is also driven by differences in the surface reaction effective free energy. These free energy differences arise from differences in the transport of the plasma-produced species across the plasma sheaths to the reacting surfaces. The dependences of the etch rate on the film area (the “loading”), on the gas flow and on the relative temperatures of the surfaces between which transport occurs also arise from these considerations and explain the salient features of the reactive ion etching of gold in a chlorine plasma.     

Universal plasma electron source

The construction of universal plasma electron sources that allows to generate both focused electron beams and large cross-section beams within stationary and pulse mode of operation is proposed, without any essential change in the construction of the source. The special feature of the source is the stability of electron beam parameters over a wide range of pressure (up to 10⁻² mbar), which makes it possible to use it in difficult vacuum conditions caused by intensive gas emission from the treated surface. High stability of the focused electron beam parameters is achieved due to a special configuration of electric and magnetic fields in the region of electron extraction. Generating large cross-section beams, a weak dependence of beam parameters of gas pressure, is achieved by using the method of double-grid stabilization of the emitting plasma surface. Physical processes causing an increase in parameter stability are discussed.     

Proton radiography in plasma

Generation of high intensity and well collimated multi-energetic proton beams from laser-matter interaction extends the possibility to use protons as a diagnostic tool to image imploding target in Inertial Confinement Fusion (ICF) experiments. Due to the very large mass densities reached during implosion, protons traveling through the target undergo a very large number of collisions. Therefore the analysis of experimentally obtained proton images requires care and accurate numerical simulations using both hydrodynamic and Monte Carlo codes. The impact of multiple scattering needs to be carefully considered by taking into account the exact stopping power for dense matter and for the underdense plasma corona. In our paper, density, temperature and ionization degree profiles of the imploding target are obtained by 2D hydrodynamic simulations performed using CHIC code. Proton radiography images are simulated using the Monte Carlo code (MCNPX; adapted to correctly describe multiple scattering and plasma stopping power) in order to reconstruct the complete hydrodynamic history of the imploding target. Finally we develop a simple analytical model to study the performance of proton radiography as a function of initial experimental parameters, and identify two different regimes for proton radiography in ICF.