Bulletin of the American Physical Society
68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015; Honolulu, Hawaii
Session KW3: Modeling and Simulation II |
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Chair: Christopher Moore, Sandia National Laboratories Room: 305 AB |
Wednesday, October 14, 2015 1:30PM - 2:00PM |
KW3.00001: Heavy particle transport in sputtering systems Invited Speaker: Jan Trieschmann This contribution aims to discuss the theoretical background of heavy particle transport in plasma sputtering systems such as direct current magnetron sputtering (dcMS), high power impulse magnetron sputtering (HiPIMS), or multi frequency capacitively coupled plasmas (MFCCP). Due to inherently low process pressures below one Pa only kinetic simulation models are suitable. In this work a model appropriate for the description of the transport of film forming particles sputtered of a target material has been devised within the frame of the OpenFOAM [1] software (specifically dsmcFoam [2]). The three dimensional model comprises of ejection of sputtered particles into the reactor chamber, their collisional transport through the volume, as well as deposition of the latter onto the surrounding surfaces (i.e. substrates, walls). An angular dependent Thompson energy distribution [3] fitted to results from Monte-Carlo simulations is assumed initially. Binary collisions are treated via the M1 collision model [4], a modified variable hard sphere (VHS) model. The dynamics of sputtered and background gas species can be resolved self-consistently following the direct simulation Monte-Carlo (DSMC) approach or, whenever possible, simplified based on the test particle method (TPM) with the assumption of a constant, non-stationary background at a given temperature. At the example of an MFCCP research reactor the transport of sputtered aluminum is specifically discussed. For the peculiar configuration and under typical process conditions with argon as process gas the transport of aluminum sputtered of a circular target is shown to be governed by a one dimensional interaction of the imposed and backscattered particle fluxes. The results are analyzed and discussed on the basis of the obtained velocity distribution functions (VDF).\\[4pt] [1] OpenFOAM, www.openfoam.org.\\[0ex] [2] T.J. Scanlon \textit{et al.}, Comp. Fluids \textbf{39}, 2078 (2010).\\[0ex] [3] M. Stepanova, S.K. Dew, J. Vac. Sci. Technol. A \textbf{19}, 2805 (2001).\\[0ex] [4] A. Kersch \textit{et al.}, J. Appl. Phys. \textbf{75}, 2278 (1994). [Preview Abstract] |
Wednesday, October 14, 2015 2:00PM - 2:15PM |
KW3.00002: A Vlasov-BCA method for numerical simulations of the plasma sheath structure in presence of a material releasing wall Davide Curreli, Rinat Khaziev, Shane Keniley, Steven Marcinko We present a coupled Vlasov-BCA (Binary Collision Approximation) method for the simulation of the plasma sheath in presence of a material-releasing wall. The method couples a Vlasov solver of a multi-species plasma with an improved version of the TRIDYN code including surface dynamic composition, multi-component targets, and surface roughness effects. The classical problem of defining proper boundary conditions into a Vlasov code is solved by using at the boundary distribution functions calculated thanks to the BCA module. A standard kernel smoother is adopted to control the noise level of the distributions predicted by the BCA. When solved in one dimension the method is computationally inexpensive and allows to resolve the plasma sheath structure in presence of material sputtering, backscattering, and implantation, for both mono-component and multi-component targets. From the moments of the distribution functions, the particle and heat fluxes of both the plasma and the material species can be easily derived. [Preview Abstract] |
Wednesday, October 14, 2015 2:15PM - 2:30PM |
KW3.00003: A zero-equation turbulent electron transport model for cross-field migration and its implementation in a 2-D hybrid plasma Hall thruster simulation Mark Cappelli, Chris Young, Eusnun Cha, Eduardo Fernandez We present a simple, zero-equation turbulence model for electron transport across the magnetic field of a plasma Hall thruster and integrate this model into 2-D hybrid particle-in-cell simulations of a 72 mm diameter laboratory thruster operating at 400 W. The turbulent transport model is based on the assumption that the primary means of electron energy dissipation is the turbulent eddy cascade in the electron fluid to smaller scales. Implementing the model into 2-D hybrid simulations is relatively straightforward and leverages the existing framework for solving the electron fluid equations. We find that the model captures the strong axial variation in the mobility seen in experiments. In particular, it predicts the existence of a strong transport barrier which anchors the region of plasma acceleration. The model also captures the time-averaged experimental discharge current and its fluctuations due to ionization instabilities. We observe quantitative agreement with recent laser induced fluorescence measurements of time-averaged xenon ion and neutral velocities along the channel centerline. [Preview Abstract] |
Wednesday, October 14, 2015 2:30PM - 2:45PM |
KW3.00004: Development Of Sputtering Models For Fluids-Based Plasma Simulation Codes Seth Veitzer, Kristian Beckwith, Peter Stoltz Rf-driven plasma devices such as ion sources and plasma processing devices for many industrial and research applications benefit from detailed numerical modeling. Simulation of these devices using explicit PIC codes is difficult due to inherent separations of time and spatial scales. One alternative type of model is fluid-based codes coupled with electromagnetics, that are applicable to modeling higher-density plasmas in the time domain, but can relax time step requirements. To accurately model plasma-surface processes, such as physical sputtering and secondary electron emission, kinetic particle models have been developed, where particles are emitted from a material surface due to plasma ion bombardment. In fluid models plasma properties are defined on a cell-by-cell basis, and distributions for individual particle properties are assumed. This adds a complexity to surface process modeling, which we describe here. We describe the implementation of sputtering models into the hydrodynamic plasma simulation code USim, as well as methods to improve the accuracy of fluids-based simulation of plasmas-surface interactions by better modeling of heat fluxes. [Preview Abstract] |
Wednesday, October 14, 2015 2:45PM - 3:00PM |
KW3.00005: 2D-Combined ICP/CCP numerical modeling for RF plasma source Masaru Miyashita, Kei Ikeda, Syuta Ochi A numerical investigation of sputtering distribution on antenna cover in Radio Frequency (13.56MHz) plasma(RF plasma) source by energetic ions bombardment has been performed including influences of static electric field from voltage of antenna and of inductive electric field from current of antenna. In order to validate the developed technique, the static electron heating distribution and the inductive electron heating distribution in simulation are compared. The comparison shows the static electric field is shielded in the sheath of the high electron density (10$^{17}$m$^{-3}$) plasma and the plasma is sustained by inductive electric field from current of antenna. The deep sheath potential in simulation is generated over the region of large vulnerable in experiment. The numerical simulation technique with calculating static electric field and inductive electric field is important for development of the RF plasma source with large current and long life time. [Preview Abstract] |
Wednesday, October 14, 2015 3:00PM - 3:15PM |
KW3.00006: Plasma Characteristics for Curved Capacitive Source using Plasma Modeling Kallol Bera, John Forster, Mani Subramani, Umesh Kelkar Capacitively coupled plasma (CCP) in curved configuration has been investigated for plasma density and power deposition distribution using plasma modeling. In the CCP model, charged particle densities are determined by solving transport equations using drift-diffusion approximation. The electron temperature is solved using electron energy equation. The electric (scalar) potential is derived from Poisson equation. A semi-circular annular configuration consisting of inner curved surface as powered electrode and outer curved surface as grounded electrode is used. Ar plasma at moderate pressure (a few Torr) has been simulated at 13.56 MHz. A negative dc bias develops at the powered electrode that is smaller than grounded electrode. Stronger electric field leads to stronger power deposition and correspondingly higher plasma density near the powered electrode. As straight segments are added to the semi-circular configuration, it is found that plasma drifts away from the curved region to the straight region. Further addition of semi-circular and straight segments reduces DC bias to zero as the powered electrode and grounded electrode areas become equal. However, plasma is observed to be stronger near the straight region compared to curved region as plasma drifts away from the curved region to straight region. [Preview Abstract] |
Wednesday, October 14, 2015 3:15PM - 3:30PM |
KW3.00007: Student Award Finalist: Advances in the three-dimensional simulation of streamer discharges Jannis Teunissen, Ute Ebert We have implemented a 2D and 3D streamer model inside AFiVO, a simulation framework that we have recently developed. We use numerical techniques such as adaptive mesh refinement, parallel multigrid and a novel implementation of photoionization to push simulations to new limits. This allows us to study the interaction of two streamers in 3D, the branching of streamers in 3D, or the propagation of a streamer over a dielectric surface. Simulations in 2D also benefit, allowing for a relatively interactive exploration of parameter regimes. We present highlights of the new simulation possibilities. [Preview Abstract] |
Wednesday, October 14, 2015 3:30PM - 3:45PM |
KW3.00008: Pulsed surface discharges in nitrogen and in air: experiments and simulations Anna Dubinova, Dirk Trienekens, Ute Ebert, Sander Nijdam We study positive streamer discharges in nitrogen and in air propagating near or on the surface of a dielectric rod. The discharge is launched from a needle, and propagates towards a dielectric rod which is placed directly under the needle. In some cases, when the discharge attaches to the rod it moves along it with a velocity larger than in the gas without the rod, and in other cases it moves more slowly. We aim at understanding this dynamics of streamer interaction with dielectrics and the mechanisms of streamer propagation along the surface. We have developed a cylindrically symmetric model based on the fluid streamer model in local field approximation. Our model allows us to analyze the interplay of photoionization, photoelectron emission from the rod and dielectric polarization of the rod, and voltage pulse shape, amplitude and repetition frequency. We compare the morphology and the velocity of the simulated surface streamers with those measured in dedicated experiments. In the experiments, we use stroboscopic imaging with an ICCD camera to retrieve streamer velocity and shape. [Preview Abstract] |
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