Bulletin of the American Physical Society
71st Annual Gaseous Electronics Conference
Volume 63, Number 10
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session QR3: Inductively Coupled Plasmas |
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Chair: Birk Berger, University Cottbus Room: Oregon Convention Center A106 |
Thursday, November 8, 2018 2:00PM - 2:15PM |
QR3.00001: Inductively Coupled Plasma with Ferromagnetic Core for Space Propulsion Valery Godyak Inductively Coupled Plasma, (ICP) enhanced with ferromagnetic core, (MFICP) has proven having many benefits comparing to conventional coreless ICPs [1]. Superior efficiency and spatial selectivity for rf power injection, ability to work at low rf frequency and longevity are main advantages of FMICP that are already utilized in lighting and plasma processing of materials. A comparison of two MFICP based embodiments for space propulsion (the ion thruster and the plasma cathode for ion beam neutralizing) with similar devices based on traditional ICP, Helicon and Microwave concepts is given in this presentation. It is shown that both FMICP based devices have superior plasma generation efficiency, simpler construction and more compact comparing to ion thrusters and plasma cathodes based on traditional concepts. Apart of efficiency and longevity FMICP has many others features beneficial for space propulsion that are discussed in this presentation. [1] V. A. Godyak, Ferromagnetic Enhanced Inductive Plasma Sources, J. Phys. D: Appl. Phys., 46, 283001, 2013. [Preview Abstract] |
Thursday, November 8, 2018 2:15PM - 2:30PM |
QR3.00002: Oxygen metastable molecule densities in inductively-coupled plasmas in pure O$_{2}$ measured by VUV absorption Jean-Paul Booth, Abhyuday Chatterjee, Olivier Guaitella, Nelson de Oliveira, Laurent Nahon, Colin Western Oxygen molecules possess two metastable states (the a$^{1}$$\Delta$$_{g}$ at 0.98 eV and the b$^{1}$$\Sigma$$^{+}$ 1.64 eV). Models have suggested that both can play an important role in the neutral and charged particle kinetics plasmas in pure O$_{2}$ at low pressures. We have used the DESIRS vacuum ultraviolet beamline and Fourier-Transform spectrometer at Synchrotron Soleil to record the absorption spectra of inductively-coupled plasmas (ICP) in O$_{2}$, as a function of gas pressure (5-50 mTorr) and injected RF power. This allowed determination of the absolute line densities of O$_{2}$ in the X, a and b states (using a new calculation of the line strength in the case of b$^{1}$$\Sigma$$^{+}$). At high RF power the a$^{1}$$\Delta$$_{g}$ state density saturates at 10-15 \% of that of the ground state, whereas the b$^{1}$$\Sigma$$^{+}$ state density remains at less than 1\%. The implications of these measurements on the plasma kinetics will be discussed. [Preview Abstract] |
Thursday, November 8, 2018 2:30PM - 2:45PM |
QR3.00003: Complex Transients in Power Modulated Inductively Coupled Chlorine Plasmas Vincent M Donnelly, Tyler List, Tianyu Ma, Priyanka Arora, Steven Shannon Time-dependent studies of power-modulated chlorine inductively-coupled plasmas will be presented. Power was modulated between high and low states. Time-resolved optical emission, power delivery, and Langmuir probe measurements revealed at least two periodic steady-state conditions upon switching from high to low power: a ``normal'' mode in which electron temperature (T$_{\mathrm{e}})$ remains constant, while electron and ion number densities (n$_{\mathrm{e}}$ and n$_{\mathrm{+}})$ and optical emission spectroscopic (OES) intensities smoothly drop to a level roughly equal to the fractional drop in power, and an ``abnormal'' mode in which T$_{\mathrm{e}}$ n$_{\mathrm{e}}$, n$_{\mathrm{+}}$ and OES intensities plummet before rising to values more commensurate with the drop in power. Whether the plasma operates in the normal or abnormal mode is sensitive to settings on the matching network pressure and pulsing parameters. The ignition delays can be qualitatively understood with the power balance model commonly used to explain instability-induced, self-modulation in highly electronegative plasmas, caused by the slower time response of negative ions compared with electrons. [Preview Abstract] |
Thursday, November 8, 2018 2:45PM - 3:00PM |
QR3.00004: Kinetic Model of Stochastic Heating in the INCA Discharge Uwe Czarnetzki A novel concept for tailored collisionless electron heating has been demonstrated experimentally for the first time [1]. A planar array of small coils generates a phase correlated vortex electric field structure with well-defined resonances in velocity space. The discharge based on this concept operates efficiently at low pressures and has the property of easy upscaling to square-meter size. The basic idea was first proposed in 2014 and studied by simulation [2]. Here, the stochastic heating mechanism is analyzed by two complementary analytical models [3]. It is shown that the heating is indeed non-local in the plane of the vortex fields but local in the vertical coordinate. The mean heating power per area, the complex conductivity, the complex damping constant, and an effective stochastic collision frequency are calculated. Conditions for effective stochastic heating are provided. In addition the role of elastic collisions is investigated. Good agreement between theory and experiment is obtained. [1] Ph. Ahr, T.V. Tsankov, J. Kuhfeld, U. Czarnetzki, submitted to PSST, arXiv:1806.02043 (2018). [2] U. Czarnetzki and Kh. Tarnev, Physics of Plasmas 21, 123508 (2014). [3] U. Czarnetzki, submitted to PSST, arXiv:1806.00505 (2018) [Preview Abstract] |
Thursday, November 8, 2018 3:00PM - 3:15PM |
QR3.00005: INCA - Inductive Discharge Array Philipp Ahr, Tsanko V. Tsankov, Jan Kuhfeld, Uwe Czarnetzki A novel low pressure inductive discharge and stochastic electron heating concept is demonstrated experimentally for the first time~[1]. Here, electrons are collisionlessly heated in a phase-correlated vortex field array, as proposed theoretically in [2]. These periodic vortex fields are produced by an array of $6\times 6$ small inductive planar coils. Easy upscaling to $m^2$-size is possible. Design considerations together with results from various diagnostics are presented. The experimental data show consistently efficient and homogeneous plasma production at pressures below 1 Pa as well as the presence of super energetic electrons. The efficient heating is further demonstrated by the velocity distribution of the electrons. The presented results agree well with theory~[3]. Possible applications for this new plasma source include large area processing and space propulsion.\par \noindent [1] Ph Ahr \textit{et al}, submitted to \textit{Plasma Sources Sci.\ Technol.} (2018), arXiv:1806.02043\par \noindent [2] U Czarnetzki and Kh Tarnev, \textit{Phys.\ Plasmas} \textbf{21} (2014) 123508\par \noindent [3] U Czarnetzki, submitted to \textit{Plasma Sources Sci.\ Technol.} (2018), arXiv:1806.00505 [Preview Abstract] |
Thursday, November 8, 2018 3:15PM - 3:30PM |
QR3.00006: Multi-zone Equilibrium of ICP Discharge for Plasma Processing. Mechanism of Electron Heating Vladimir Nagorny ICP discharges and plasma sources are quite common in semiconductor plasma processing. Many observations, plasma measurements and simulations were published through the years. However theoretical considerations are limited to a case when plasma equilibrium can be characterized as quasi-global. In a real processing plasma this kind of equilibrium is unstable. Here we analyze a situation when equilibrium consists of at least two zones. In a cylindrical case a thin, band-like zone confining all hot electrons, where efficient electrons heating and plasma generation occurs, absorbs almost all the energy from the coil and is linked on one side to the wall adjacent to induction coil. On the other side this band is linked to the second - plasma transfer zone, which is fed by the energy and particles escaping from the first zone. The second zone is also linked to surrounding walls. In a way, this structure of ICP discharge reminds a glow discharge structure. The self-sustaining plasma generating zone functions similar to a cathode fall, and the plasma transfer zone - similar to a positive column. The number of plasma generating zones depends on the number of coils and construction of the coil, and usually more than one plasma generating zones are linked to a common plasma transfer zone. [Preview Abstract] |
Thursday, November 8, 2018 3:30PM - 3:45PM |
QR3.00007: Investigation on the radio-frequency power transfer efficiency in an inductively coupled hydrogen plasma source with an expansion region Hong Li, Fei Gao, De-Qi Wen, Wei Yang, Peng-Cheng Du, You-Nian Wang The radio-frequency (RF) power transfer efficiency is experimentally and numerically investigated in an inductively coupled hydrogen plasma source with an expansion region. The fundamental plasma properties are obtained by means of a Langmuir probe. The effect of the antenna coil turns, N, is also studied in a range of 3 - 9 turns. It is found that more coil turns can significantly enhance the power transfer efficiency. Moreover, the experimental results show that the power transfer efficiency first increases and then reaches the maximum with increasing the applied power. The peak of the power transfer efficiency shifts consistently from 1 Pa to higher pressures with increasing the applied power and N. In order to reproduce the experimental results and give a comprehensive knowledge of the power absorption mechanism, a self-consist hybrid model is carried out. The numerical results and the analytic solutions in the limit cases can well explain the various trends of the power transfer efficiency obtained in the experiment. [Preview Abstract] |
Thursday, November 8, 2018 3:45PM - 4:00PM |
QR3.00008: Consequences of E-H transitions in Impendence Matching of Pulsed Inductively Coupled Plasmas Chenhui Qu, Steven Lanham, Peng Tian, Carl Smith, Kristopher Ford, Joel Brandon, Steven Shannon, Mark J. Kushner Pulsed inductively coupled plasmas (ICPs) are used for selective etching in microelectronics fabrication. Due to disparities in the input impendence of the plasma reactor and the output impedance of the power supply, impedance matching networks (IMN) with variable capacitors are used to maximize transmitted power into the plasma. During a pulsed cycle, the impedance of the ICP can change faster than the capacitors in the IMN can be adjusted, resulting in power to the ICP being unmatched for part of the cycle. In halogen gases, the electron density during the inter-pulse afterglow can decrease by factors of 10-100 resulting in the next power-pulse beginning with an E-H (electrostatic-inductive) transition. The change in reactance of the ICP during the E-H transition further challenges impedance matching. Results from a computational investigation of impedance matching to pulsed ICPs sustained in Ar/Cl$_{\mathrm{2}}$ at 10s mTorr will be discussed for conditions where an E-H transition occurs at power-on. IMN and transmission line models were interfaced to the Hybrid Plasma Equipment Model for these conditions. IMN settings were chosen to best match the pulse at different times during the cycle -- early matching emphasized power deposition in the E-mode and late matching emphasized the H-mode. [Preview Abstract] |
Thursday, November 8, 2018 4:00PM - 4:15PM |
QR3.00009: Predictive Model of E-H Mode Transition Power Level Shaun Smith, David Coumou Inductively Coupled Plasma sources driven by RF power are well adopted for high-volume manufacturing of semiconductor devices. The vexing challenge to the utility of these plasma processing reactors is the existence of the E-H mode transition. Industry notably avoids the process region associated with this transition, where plasma instabilities prohibit reliable RF power delivery. Simulation of the electrical properties of the power delivery circuit coupled with a simple model of the plasma response are shown to be sufficient to quantitatively predict the power level of the E-H transition as well as suggest a mechanism for the mode transition. This modeling is compared with experiment to show behavior which is explained by the presented model. This work provides support for a self-consistent model of the E-H instability based on the power flow stability of the power delivery system [Preview Abstract] |
Thursday, November 8, 2018 4:15PM - 4:30PM |
QR3.00010: Numerical study of the influence of faraday shield on RF neutral beam ion sources Zhen-Hua Bi, Yi Hong, Lu Liu, Yang Zhang, Wen Yan, Ying Song, Dongping Liu A high-density RF ion source is an essential part in neutral beam injector. In high power discharge status, RF ion source will suffer from ultra-high heat flux and ion irradiation. It will reduce the service life of the source reactor. One possible way to solve this problem is to introduce a water-cooled faraday shield, which could effectively protect the dielectric lateral wall from the heat load of the plasma. The faraday shield generally shapes as a cage like grid structure to avoid the eddy current. However, it will also harm for the coupling effect between the source power and plasma. To study this effect, a 3D fluid model is introduced to investigate the plasma parameters basing on the RF inductively coupled plasma (ICP) reactor with faraday shield behavior. Fluid equations are solved by COMSOL Multiphysics software. H2 is taken as the working gas. Due to the limitation of the fluid model, the pressure is taken as 5 Pa so the H negative reactions are omitted in this study. The simulation results show that, when the faraday shield shapes from optically open to optically close, the plasma peak density decreases, while the spatial distribution has less influence. [Preview Abstract] |
Thursday, November 8, 2018 4:30PM - 4:45PM |
QR3.00011: A global model of a microwave driven inductively coupled small-scale plasma jet Michael Klute, Horia Eugen Porteanu, Wolfgang Heinrich, Peter Awakowicz, Ralf Peter Brinkmann Microwave driven plasmas-jets play an important role in many technical applications. These plasma jets are usually excited in the capacitive mode, also called E-mode. This mode, however, couples considerable power to ions which limits the jet efficiency and gives rise to negative side effects. The inductive coupling, known as H-mode, eliminates these disadvantages and is attractive for large scale plasmas. To realize the H-mode also for a plasma jet source of much smaller size, Porteanu et al. [1] proposed an inductive coupling via a specially designed resonator. This work presents a global model of the new device based on the volume-integrated balances of particle number and electron density, and a series representation of the electromagnetic field in the cavity. Therefore an infinite number of modes can be found ordered by the azimuthal wave number m. These modes essentially determine the electromagnetic behavior of the plasma and differ from ordinary cavity modes. The mode m=0 can be identified with the inductive mode and will be called H-mode, the mode m=1 is the capacitive mode and will be called E-mode. For a given microwave power, several equilibrium points exist and a hysteresis in the E to H transition is observed. [1]Porteanu et al. Plasma Sources Sci.Technol.22, 2013 [Preview Abstract] |
Thursday, November 8, 2018 4:45PM - 5:00PM |
QR3.00012: Floating-wire-assisted remote generation of high-density atmospheric pressure inductively coupled plasma Thi-Thuy-Nga Nguyen, Minoru Sasaki, Hidefumi Odaka, Takayoshi Tsutsumi, Kenji Ishikawa, Masaru Hori Atmospheric pressure plasma (APP) has been intensively studied due to the miniaturization of equipment size and the reduction of energy consumption. Among the APP sources, the inductively coupled plasma (ICP) sources are potentially used for high-density plasma generation. Without an additional external power supply, the ICP has difficulty in igniting discharges at atmospheric pressure. By placing a long floating wire inside the power source, the plasma can ignite easily and extend to a remote region. Here we report an atmospheric pressure inductively coupled plasma source that is designed by a 200-mm-high quartz tube with a long floating wire placed inside and a three-turn copper coil. When 100 W of a very high frequency power was applied, a large-area plasma with an electron density of 10$^{\mathrm{14}}$ cm$^{\mathrm{-3}}$ and a low gas temperature less than 850 K was remotely generated at downstream region where was 140 mm far from the coil region center, and the plasma discharge was more than 170 mm in length. This APP source could be developed to produce a high-density plasma for high-rate and large-scale etching applications. [Preview Abstract] |
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