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Plasma Science, IEEE Transactions on

Issue 6 • Date Dec. 1998

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Displaying Results 1 - 21 of 21
  • 1998 Index IEEE Transactions on Plasma Science Vol. 26 - Author Index

    Page(s): 1750 - 1758
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    Freely Available from IEEE
  • Subject index

    Page(s): 1758 - 1772
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    Freely Available from IEEE
  • Ion dose uniformity for planar sample plasma immersion ion implantation

    Page(s): 1669 - 1679
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    In spite of recent progress on plasma immersion ion implantation (PIII) in semiconductor processing, for example, formation of silicon on insulator and shallow junctions, ion dose, and energy uniformity remains a major concern. We have recently discovered that the sample stage (chuck) design can impact ion uniformity significantly. Using a theoretical model, we have investigated three different chuck designs and conclude that insulators on the stage can alter the adjacent electric field and ion trajectories. Even though the conventional stage design incorporating a quartz shroud reduces the load on the power supply and contamination, it yields ion dose and energy nonuniformity unacceptable to the semiconductor industry. Thus, for semiconductor applications, the stage should be made of a conductor, preferably silicon or silicon coated materials and free of quartz View full abstract»

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  • Effect of air and oxygen content on the dielectric barrier discharge decomposition of chlorobenzene

    Page(s): 1695 - 1699
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    Experiments were performed on the plasma-assisted decomposition of dilute concentrations of chlorobenzene in air/oxygen and argon/oxygen gas mixtures at atmospheric pressure using a coaxial geometry single dielectric barrier discharge for different oxygen concentrations and energy densities. The results show that the decomposition process requires higher energy densities using air mixtures compared to argon/oxygen mixtures and is not linearly dependent on the oxygen content for a given energy density. The main decomposition products detected in the offgas were carbon dioxide and carbon monoxide View full abstract»

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  • Low pressure plasma immersion ion implantation of silicon

    Page(s): 1661 - 1668
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    Mono-energetic plasma immersion ion implantation (PIII) into silicon can be attained only under collisionless plasma conditions. In order to reduce the current load on the high voltage power supply and modulator and sample heating caused by implanted ions, the plasma pressure must be kept low (<1 mtorr). Low pressure PIII is therefore the preferred technique for silicon PIII processing such as the formation of silicon on insulator. Using our model, we simulate the characteristics of low pressure PIII and identify the proper process windows of hydrogen PIII for the ion-cut process. Experiments are conducted to investigate details in three of the most important parameters in low pressure PIII: pulse width, voltage, and gas pressure. We also study the case of an infinitely long pulse, that is, dc PIII View full abstract»

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  • Effects of discharge frequency on plasma characteristics and etching characteristics in high density Cl2 plasma: comparison of ultrahigh-frequency plasma and radio-frequency plasma

    Page(s): 1621 - 1627
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    We investigated the effects of discharge frequency on the characteristics of polycrystalline-silicon etching rates and on the etching selectivity on the gate oxide (SiO2). An ultrahigh-frequency (UHF) plasma excited at 500 MHz was found to possess a wider process window for highly selective polycrystalline silicon etching than did an inductively coupled plasma excited at 13.56 MHz. The ionization rate in the UHF plasma is nearly constant at discharge pressures from 3-20 mtorr because the discharge frequency is higher than the electron-collision frequency in that plasma View full abstract»

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  • The atmospheric-pressure plasma jet: a review and comparison to other plasma sources

    Page(s): 1685 - 1694
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    Atmospheric-pressure plasmas are used in a variety of materials processes. Traditional sources include transferred arcs, plasma torches, corona discharges, and dielectric barrier discharges. In arcs and torches, the electron and neutral temperatures exceed 3000°C and the densities of charge species range from 1016-1019 cm-3. Due to the high gas temperature, these plasmas are used primarily in metallurgy. Corona and dielectric barrier discharges produce nonequilibrium plasmas with gas temperatures between 50-400°C and densities of charged species typical of weakly ionized gases. However, since these discharges are nonuniform, their use in materials processing is limited. Recently, an atmospheric-pressure plasma jet has been developed, which exhibits many characteristics of a conventional, low-pressure glow discharge. In the jet, the gas temperature ranges from 25-200°C, charged-particle densities are 10 11-1012 cm-3, and reactive species are present in high concentrations, i.e., 10-100 ppm. Since this source may be scaled to treat large areas, it could be used in applications which have been restricted to vacuum. In this paper, the physics and chemistry of the plasma jet and other atmospheric-pressure sources are reviewed View full abstract»

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  • Quasi-neutral particle simulation of magnetized plasma discharges: general formalism and application to ECR discharges

    Page(s): 1592 - 1609
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    We have developed an electrostatic particle-in-cell/Monte Carlo (PIC/MC) simulation method for magnetized discharges, in which both internal electric fields and sheath potentials are determined from the requirement of quasineutrality within the bulk plasma, rather than by solving Poisson's equation. Thus the electric field is not sensitive to statistical noise which may occur in the small quantity ne-n i. Sheaths are treated self consistently as thin potential barriers, and the Bohm criterion for ion flux into the sheath is imposed as a boundary condition. Electron plasma oscillations do not appear in the model, and the debye length is essentially set to zero. Thus time steps and spatial gridding can be chosen to represent the characteristic macroscopic time and space scales of interest, which may be orders of magnitude larger than the plasma frequency/debye length scales. The simulation technique correctly represents kinetic features such as non-Maxwellian distributions and Landau damping and can be used for either collisional or collisionless plasmas. We present results from an axisymmetric simulation of an electron cyclotron resonance (ECR) discharge in low-pressure argon, which show that the discharge is strongly affected by cross-field ion flows, even when the vessel walls are insulators. We also present analytic calculations based on the model, which afford new insights into cross-field transport in a metallic vessel and show that the classic Simon diffusion can be strongly inhibited by the effect of sheath potentials View full abstract»

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  • Inductive plasma sources for plasma implantation and deposition

    Page(s): 1653 - 1660
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    External and reentrant radio frequency inductive plasma sources are developed for plasma ion implantation and deposition processes in a 1.8 m3 vacuum vessel. Plasma densities in the range 1016 -1017 m-3 desirable for the above processes. External plasma sources could not yield the required plasma densities because of high particle losses in the transition region between the source and the main vessel. The particle losses are clarified through experiments and analysis, with and without multipole magnetic confinement. Reentrant plasma sources eliminate transmission losses and yield high plasma densities with good spatial uniformity View full abstract»

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  • Accuracy of the equivalent circuit model using a fixed beam impedance for klystron gain cavities

    Page(s): 1745 - 1749
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    Most small-signal calculations of the modulation in a klystron's gain cavity use an equivalent circuit which includes a fixed beam impedance. Comparing this calculation to the gain calculated self-consistently, we note there are appreciable errors in both the calculated amplitude and phase of the cavity's modulation. These errors may lead to large accumulated errors in determining either the tube's small-signal or large-signal gain. Both techniques are used in a comparison with an existing S-band klystron View full abstract»

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  • Structural analysis of silicon dioxide and silicon oxynitride films produced using an oxygen plasma

    Page(s): 1700 - 1712
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    Plasma grown silicon dioxide and oxynitride layers are shown to represent, for microelectronic applications, a good alternative method to conventional thermally grown layers. Fast growth rates, together with good electrical properties are demonstrated, at low process temperatures. Growth kinetics of SiO2 layers synthesized both in RF and microwave plasma anodization systems are presented for a wide range of substrate temperatures in the range (90-560°C). Structural properties of the films can be affected during preparation, due to radiation from the plasma and particle bombardment. For the SiO2 layers obtained by RF anodization at 300°C, these surface structural features were investigated by scanning electron microscopy; bulk and interface dielectric properties of the layers were analyzed by spectroellipsometry. The results were correlated with electrical properties and data coming from the growth kinetics. It was found that the properties of the layers, both structural and electrical, are strongly dependent on the growth regime (linear or parabolic). Silicon oxynitride films produced by plasma anodization of silicon nitride layers are investigated by spectroellipsometry and Auger electron spectroscopy. These results are correlated with electrical measurements and used to explain the changes in film properties View full abstract»

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  • Effects of plasma parameters on viscosity

    Page(s): 1738 - 1744
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    A numerical code is developed to study the effect of ion density and temperature (as well as ion pressure and temperature gradients) on the amplitude of the local maxima of the poloidal viscosity with respect to the poloidal Mach number using the model developed by Shaing (1993). The sum of the poloidal viscosity and ion-neutral collisions is determined from the dependence of the plasma radial current on the radial electric field in a biased electrode experiment. The experimental results in the interchangeable module stellarator agree qualitatively with the predictions of the numerical calculation regarding the effects of variation of ion density and temperature on viscosity View full abstract»

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  • Transport of a cathodic arc plasma in a straight, magnetized duct

    Page(s): 1645 - 1652
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    Measurements are presented of the transport of a supersonic, cathodic-arc plasma through a straight, magnetized duct. These measurements are compared to previous work on curved ducts, in order to illuminate the effect of duct curvature on the transport. The axial ion flux through the straight duct decays as ions are lost to the walls. This decay is exponential, with a scale length of seven duct radii; this is two to three times longer than in most experiments on curved ducts. The scale length is independent of the magnetic field strength for fields from 5-40 mT. (For this range of magnetic fields, the electron Larmor radius varies from 0.03-0.003 duct radii; while the ion Larmor radius varies from 4-0.5 duct radii.) This differs from previous experiments with curved ducts, where the attenuation length generally increases with magnetic field. Also in contrast to experiments on curved ducts, biasing the duct wall to positive voltages similar to the ion energy produces only a slight decrease in the ion losses to the wall. The observed scale length for ion loss and its independence from the magnetic field strength are in quantitative agreement with a plasma fluid simulation. Differences in plasma transport through straight and curved ducts are discussed View full abstract»

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  • The effect of subsurface doping on gate oxide charging damage

    Page(s): 1628 - 1634
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    The effect of wells and substrate type on gate oxide charging damage during plasma processing, and more specifically plasma immersion ion implantation, is modeled. The simulation combines the equations governing the plasma currents and integrated circuit device models to determine the gate oxide stressing voltage during implantation. Depending on the substrate type and the surface potential (Vs), a depletion region may exist, reducing the gate oxide voltage, and hence the gate oxide damage. In addition, well structures, by the nature of their capacitance, modulate Vs, altering the oxide stressing voltage. For most PIII implant conditions, gate oxides with p-type channel doping will be damaged more than those oxides with n-type channel doping. Experimental results confirm the substrate and well effects on plasma charging damage View full abstract»

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  • Velocity distributions in magnetron sputter

    Page(s): 1635 - 1644
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    Results of the particle simulation of magnetron sputter are presented. Using a kinetic code, we obtain the spatial profiles of plasma density, potential, and velocity distribution function, along with the electron temperature, the ion density, the current density, and the deposition profiles at the anode surface. The result of simulation is compared with the Child-Langmuir law applied to the magnetron discharge and the global model. The velocity distribution function of electrons is Maxwellian, but that of ions is non-Maxwellian near the cathode with the majority in the energy range below 50 eV View full abstract»

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  • Plasma-assisted deposition of a three-layer structure by vacuum and gas arcs

    Page(s): 1680 - 1684
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    The durability and adhesion of thin coatings often depends on the structure and properties of the layer intermediate between the coating and the substrate, especially in the case where the layer and the substrate are highly different in microhardness. With a vacuum arc and a hot-cathode arc, a process has been arranged which involves cleaning of the surface, nitration of the article, and deposition of a coating. As a result, a three-layer composition has been produced which consists of a TiN layer of thickness up to 5 μm and microhardness 20 GPa, an intermediate Fe4N layer of thickness up to 8 μm and microhardness 7.5 GPa, and a nitrated layer of thickness up to 100 μm with a gradually varying microhardness. With the TiN layer showing high adhesion, the coating has a durability three of four times greater than that of a coating produced with the use of a conventional technology View full abstract»

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  • Cathodic-arc plasma density, radial profile, and total plasma inventory as measured by microwave interferometer and Faraday cup

    Page(s): 1718 - 1723
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    The total amount of plasma, peak plasma density, and plasma density radial profile are derived from a series of measurements of ion current density (with a Faraday cup) and integrated electron line density (with a microwave interferometer) for a cathodic arc derived plasma. Comparisons are made between cathode material (erbium and titanium), arc current, background gas pressure, and the presence or absence of a series magnetic solenoid around the coaxial anode and cathode View full abstract»

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  • The application of time delay method for analysis of processes which initiate electrical breakdown in 1.3 mbar nitrogen

    Page(s): 1733 - 1737
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    The contributions of ions and neutral active states to secondary electron emission in the afterglow has been analyzed of the time delay method. The dependencies of mean value of time delay on relaxation time, overvoltage, and glow current have been discussed. The analysis of validity of Laue distribution for time delay has been performed, becoming the criterion for estimation of the main cause of breakdown. Thus, afterglow can be divided in three regions: one each for the role of charged and neutral species in initiation of subsequent breakdown, and third, as the transitional one View full abstract»

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  • Role of plasma-aided manufacturing in semiconductor fabrication

    Page(s): 1610 - 1620
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    A brief review is presented of the application of plasma-aided manufacturing to semiconductor fabrication. Emphasis is placed on current state-of-the-art techniques for which plasma physics plays a significant role and on current problems that remain to be solved View full abstract»

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  • Diagnostics of an inductively coupled plasma in oxygen

    Page(s): 1724 - 1732
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    Spatial time-integrated and space-time resolved profiles of excited atoms of oxygen were measured by optical emission spectroscopy for inductively coupled plasma (ICP) in oxygen. The discharge was sustained by a single turn coil supplied by 13.56 MHz RF generator delivering 100 and 200 W of power. The spatial emission profiles give the anatomy of the discharge required in order to understand the basic kinetics of ICP. Two types of nonuniformities are observed, azimuthal anisotropy and radial nonuniformity, both caused by spatially dependent energy supply to the electrons. Our experimental results show that oxygen is much more affected by azimuthal anisotropy and radial nonuniformity than argon. It is due to a different role of metastable atoms in kinetics of excitation, whereby stepwise excitation in oxygen is less probable than in argon. Optical emission data are supplemented by Langmuir probe measurements of electron densities and plasma potentials. Electrons gain energy from the time varying fields close to the coil, and the energy is not redistributed along the radius before it is dissipated in excitation, thus the observations are not consistent with the nonlocal theory predictions for the range of pressures, geometry, and power covered in this paper View full abstract»

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  • Simulation of boron nitride sputtering process and its comparison with experimental data

    Page(s): 1713 - 1717
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    In the paper, TRIM and TRIDYN simulation codes were used to simulate the sputtering processes of boron nitride (BN) films during bombardment of ions. The TRIM and TRIDYN codes are applicable to the simulation of sputtering processes of different target materials with amorphous and polycrystalline structure. The results of the simulations are compared with experimental data. The sputtering experiments of polycrystalline hexagonal BN (h-BN) and cubic BN (c-BN) films were performed in a Commonwealth Scientific Corporation (CSC) 38-cm ion beam source device. The comparison of calculated and experimental results indicated that a) the experimental sputtering yields of h-BN and c-BN films bombarded with Ar+ ions versus the angle of incidence are in reasonable agreement with the calculated results; b) the sputtering yields of h-BN and c-BN bombarded with Ar+ are nearly of the same values versus the angle of incidence-preferential sputtering of h-BN was not found; c) the calculated sputtering. Yields of BN as a function of Ar+ ion energy are very sensitive to values of the surface binding energy (SEE); and d) surface binding energy between 2 and 3 eV for BN appears to be reasonable for the simulation of sputtering process of h-BN and c-BN films View full abstract»

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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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