Bulletin of the American Physical Society
2005 58th Gaseous Electronics Conference
Sunday–Thursday, October 16–20, 2005; San Jose, California
Session UH2: Glows II |
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Chair: Y. Sakai, Hokkaido University Room: Doubletree Hotel Cedar |
Thursday, October 20, 2005 8:00AM - 8:15AM |
UH2.00001: Analysis of the spatiotemporal behaviour of a He-Xe column plasma by self-consistent modelling Detlef Loffhagen, Florian Sigeneger The positive column plasma of a glow discharge constitutes a typical representative of a non-equilibrium plasma. Large effort has been spent in recent years to get a deeper understanding of its inherent temporal and spatial dynamics. This presentation reports on a new self-consistent method for the analysis of the space- and time-dependent behaviour occurring in a cylindrical, axially homogeneous column plasma of low-pressure glows. The model consists of hydrodynamic equations for all charged and neutral particles in the plasma, Poisson's equation describing the behaviour of the radial space charge field, the balance equation of the discharge current for the determination of the axial electric field and the time-dependent, radially inhomogeneous Boltzmann equation providing transport and rate coefficients of the electrons. First results obtained for the spatiotemporal evolution of a He-Xe mixture plasma containing 2\% of xenon in a discharge tube with a radius of 9 mm at a gas pressure of 2.5 Torr and given time-dependence of the discharge current are discussed. Starting from a homogeneous and field-free initial situation the transition to steady state at a discharge current of 60 mA is considered showing large structural changes in space and time for the electric field and the particle and flux densities of the different plasma components. [Preview Abstract] |
Thursday, October 20, 2005 8:15AM - 8:30AM |
UH2.00002: Self pulsing microdischarge in argon Antoine Rousseau, Xavier Aubert Microdischarge is generated in the hole made in a conductor-dielectric-conductor sandwich in pure argon [1]. At low discharge current, the plasma is confined inside the micro-hole and the voltage increases with the current (abnormal regime). At higher current the plasma is expended in the backside cathode region and the voltage is insensitive to the discharge current (normal regime). Between these two stable operating mode, for intermediate current value self-pulsing current oscillations are observed [2]. It is shown that the self-pulsing frequency is a linear function of the averaged current and depends only on the pxD product, for a wide range of hole diameter D and gas pressure p. Time resolved optical emission spectroscopy measurements performed in the cathode backside indicate that such oscillations are caused by short plasma expansions (2-5 $\mu $s) towards the cathode backside and correspond to a transient change between the abnormal and normal regime. The related pulse duration does not depend on the averaged current. Authors thank L.C. Pitchford, J.P. Boeuf and V. Puech for discussions. \newline \newline [1] K. H. Schoenbach, R. Verhappen, T. Tessnow, F. E. Peterkin, W. W. Byszewski, Appl. Phys. Lett. \textbf{68} (1996) 13 \newline [2] D.D. Hsu and D. B. Graves J. Phys. D: Appl. Phys. 36 (2003) 2898. [Preview Abstract] |
Thursday, October 20, 2005 8:30AM - 8:45AM |
UH2.00003: Spatiotemporal development of low-pressure low-current discharges in argon Dragana Mari\'c, Zoran Petrovi\'c We present analysis of time and space resolved development of low-pressure, low-current discharges in argon. We detect light emission by an intensified charge coupled device (ICCD) camera and support those recordings by voltage-current measurements. The goal was to extend the knowledge of kinetics of formation and maintenance of different modes of discharge -- low current diffuse Townsend discharge, constricted normal glow and abnormal glow discharge. We have performed measurements at $pd=$ 150 Pa$\cdot$cm and 45 Pa$\cdot$cm. Special care was taken in recording of the spatiotemporal development of discharge oscillations and constrictions. The development of glow and abnormal glow discharges was recorded in 2 dimensions, revealing radial dependence of the discharge and showing radial development of constrictions. During oscillations at low currents there are both axial and radial oscillations of the ionized gas. [Preview Abstract] |
Thursday, October 20, 2005 8:45AM - 9:00AM |
UH2.00004: Kinetics of electrons in BF$_3$ O. \v{S}a\v{s}i\'c, Z. Lj. Petrovi\'c, Z. Raspopovi\'c, L. Godet, S. Radovanov We have used the available data for electron scattering cross sections for electrons in BF$_3$ to calculate the transport coefficients for electrons. Monte Carlo simulation was used to perform calculations for a broad range of $E/N$ for DC and RF fields. Even though the drift velocity does not show the negative differential conductivity (NDC), the shape of the cross sections is such that it supports the NDC so the drift velocity has a broad plateau from 20 Td to 80 Td. The diffusion is very anisotropic with $D_T/D_L$ ratio of up to 4. One may expect the kinetic phenomena that were observed for other gases with Ramsauer Townsend minimum and large vibrational cross sections to take place. These calculations will be taken as the basis for interpretation or modelling of electron kinetics in pulsed plasma sources of ions for implantation during the glow and afterglow periods. [Preview Abstract] |
Thursday, October 20, 2005 9:00AM - 9:15AM |
UH2.00005: Radial distribution of plasma parameters in a BF$_{3}$ discharge Ludovic Godet, Svetlana Radovanov, Rajesh Dorai, Gilles Cartry, Christophe Cardinaud The radial distributions of discharge parameters in a pulsed DC plasma doping system have been studied using measurements of time-resolved electron density, relative ion density, plasma potential and electron temperature in BF$_{3}$ and Ar plasmas during active discharges. The effects of the electric field on the radial distribution of the plasma parameters are investigated. These measurements could be taken as the basis for interpreting on-wafer uniformity. Negative plasma potentials are observed when using a hollow cathode to create plasma while implanting at ultra low energies. The kinetics of plasma generation during the pulse-on phase has been discussed. [Preview Abstract] |
Thursday, October 20, 2005 9:15AM - 9:30AM |
UH2.00006: Time resolved energy distribution of ions from a cathode sheath in a plasma doping system in BF$_{3}$ Ludovic Godet, Svetlana Radovanov, Ziwei Fang, James Buff, Gilles Cartry, Christophe Cardinaud The time resolved energy distribution of ions present in a BF$_{3}$ glow discharge was sampled from the cathode sheath in a plasma doping system (PLAD). Plasma is generated by applying negative voltage pulses to a wafer in the presence of low pressure gas. An energy analyzer was placed behind the biased wafer and configured to measure the energy of ions striking the wafer during the pulse-on and pulse-off periods. The electrostatic optics and axial potential distribution in the energy analyzer were optimized to provide the best ion transmission efficiency. For very low energy implantation, a hollow cathode is used to create and maintain the plasma. The hollow cathode modifies the electric field in such a manner that the effective anode to cathode gap is reduced which in turn increases the plasma density and reduces the sheath thickness. The effects of the hollow cathode and the anode gap on the ion energy distribution are presented. The electron energy distribution function, measured with a Langmuir probe, and plasma sheath parameters are discussed. [Preview Abstract] |
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