Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session FT2: Plasma Modeling and Simulations I |
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Chair: Haruaki Akashi, National Defense Academy, Japan Room: Classroom 203 |
Tuesday, October 23, 2012 3:30PM - 4:00PM |
FT2.00001: Simulations of Plasma Sources for Semiconductor Device Manufacturing Invited Speaker: Peter Ventzek First being applied to etching [1] and deposition [2] more than four decades ago, plasma unit processes are now ubiquitous in the semiconductor industry. However, in many cases the use of plasma discharges for semiconductor process development has far outpaced our fundamental understanding of plasma unit processes. Fortunately, state-of-the-art modeling and simulation is now applied both in the capitol equipment and device manufacturing sectors fortified by close relationships with academic institutions and national laboratories globally. The simulation tableau, modeling and simulation for semiconductor device manufacturing community may be broken into the following categories: new concept development, new process development, equipment physics and equipment engineering. This presentation will focus on simulation modalities that highlight how the physics of production equipment result in beneficial processes. Two classes of examples with be provided. [3] The first will illustrate the behavior of microwave plasma source; the second will explore the electron kinetics associated of capacitively coupled plasma sources. The common thread linking these topics is the importance of the frequency dependence of the electron energy distribution function (eedf) to the fidelity of the simulation results. With respect to the microwave driven plasma sources, in addition to comparing predictions of different modeling approaches to experimental data, the relationship between the microwave network and the plasma dynamics in addition will be highlighted. While the criticality of the eedf to all of capacitively coupled systems will be discussed, particular focus is paid to dc augmented capacitively coupled sources where management of how the ballistic electron population reaches the substrate is critical to process results. Fluid, test particle and full particle-in-cell Monte Carlo simulations will be used to illustrate different discharge behavior.\\[4pt] [1] H. Abe et al. Jpn. J. Appl. Phys. 12, 154 (1973)\\[0pt] [2] L.L. Alt et al. J. Electrochem Soc. 110, 465 (1963)\\[0pt] [3] see companion papers by Upadhyay et al. and Kaganovich et al. [Preview Abstract] |
Tuesday, October 23, 2012 4:00PM - 4:15PM |
FT2.00002: ABSTRACT WITHDRAWN |
Tuesday, October 23, 2012 4:15PM - 4:30PM |
FT2.00003: The effect of frequency-dependent electron swarm parameters on fluid modeling of high-frequency CCP discharges Rochan Upadhyay, Shankar Mahadevan, Ikuo Sawada, Mirko Vukovic, Peter Ventzek, Laxminarayan Raja Fluid models are computationally the most feasible approach for the multidimensional simulation of reactive CCPs. Fluid models require the specification of species reaction-rate and transport coefficients. For electrons, these closure terms are dependent on the assumed/computed EEDF that depend on the excitation frequency. However the excitation frequency dependence of these electron properties for fluid models are rarely discussed. Here we explore the significance of frequency-dependent electron transport and reaction rate coefficients for high-frequency CCP discharges. We use pre-computed electron properties from a zero-dimensional electron Boltzmann solver which are used in the simulation of an argon CCP at 60MHz and pressures of 15 mTorr and 100 mTorr. A high-resolution computational mesh is developed and used to overcome any uncertainty associated with numerical discretization. We report significant differences in the pre-computed electron reaction-rate and transport coefficients for a 60 MHz EEDF compared to direct-current EEDF or assumed Maxwellian EEDF. The effects of these differences on the discharge structure are found to be significant; clearly emphasizing the importance of using frequency-dependent electron properties in high-frequency CCP models. [Preview Abstract] |
Tuesday, October 23, 2012 4:30PM - 4:45PM |
FT2.00004: Two-Dimensional (z-$\theta$) Hybrid Fluid-PIC Simulation of Enhanced Cross-field Electron Transport in an Annular \textit{E}$\times$\textit{B} Discharge Cheryl Lam, Eduardo Fernandez, Mark Cappelli We use a numerical model to study quasi-coherent plasma fluctuations and their impact on cross-field electron transport. We consider the case of an annular discharge, subject to a radial magnetic field and an axial electric field. Motivated by experimental evidence of anomalously high electron mobility across the magnetic field in Hall thruster discharges, we choose a two-dimensional axial-azimuthal (z-$\theta$) simulation geometry. The model includes a continuously-replenished heavy (Xe) neutral background, with an imposed radial magnetic field and an applied axial electric potential. We use a hybrid fluid-Particle-In-Cell treatment; the ion and neutral species are treated as collisionless particles, while the electrons are treated as a fluid continuum. Using numerical simulations to resolve the azimuthal electron dynamics, we focus on understanding the role played by fluctuations, particularly those that propagate with components perpendicular to both the applied electric and magnetic fields. Preliminary simulations predict dispersive ``tilted'' wave fluctuations in the plasma density and electron velocities. These fluctuations appear to contribute to an enhanced overall electron mobility, which is significantly higher than that based on classical scattering. [Preview Abstract] |
Tuesday, October 23, 2012 4:45PM - 5:00PM |
FT2.00005: A new approach for the determination of electron transport coefficients Markus M. Becker, Detlef Loffhagen Hydrodynamic models are commonly used for the theoretical description of gas discharge plasmas at moderate and high pressure. The full set of hydrodynamic equations is frequently simplified by means of the drift-diffusion approximation for electron particle and energy densities. Their diffusion coefficients and mobilities are usually determined from the solution of the zero-dimensional Boltzmann equation using expansion techniques and are finally incorporated into the fluid model as functions of the mean electron energy. The present contribution points out that common approaches are subject to serious restrictions regarding the description of nonlocal phenomena. A new drift-diffusion model for the treatment of the electron transport is suggested which avoids some of the drawbacks of the classical approaches. In particular, it is shown that the new model provides a better approximation of the electron heat flux, which is known to be crucial for an accurate description of the electron component in non-thermal discharge plasmas. To demonstrate its applicability, results for spatially one dimensional argon glow discharge plasmas at low and atmospheric pressure are presented and discussed. [Preview Abstract] |
Tuesday, October 23, 2012 5:00PM - 5:15PM |
FT2.00006: Comparison of a Global Model to Semi-Kinetic Fluid Simulations for Atmospheric Pressure Radio- Frequency Capacitive Discharges Kari Niemi, Deborah O'Connell, Timo Gans A global model of a homogeneous plasma bulk oscillating between electron-free rf sheaths is developed. Particle and power balance, including ohmic heating loss for bulk electrons and ions in the sheaths, yields bulk electron temperature and density. Explicit time dependence of the reduced bulk electric field and, correspondingly, of the total ionization rate and electron transport coefficients is accounted for. Results as a function of the rf power density for a gas mixture of 0.5 vol\% oxygen in helium at atmospheric pressure within a 1mm discharge gap are presented and compared to a 1D-fluid simulation, which is capable to describe the electron dynamics despite of a limited plasma-chemical reaction scheme. The quality of agreement is critically analysed and correlated to the individual global model assumptions. Possibilities of coupling the global model to comprehensive discharge chemistry models are discussed. [Preview Abstract] |
Tuesday, October 23, 2012 5:15PM - 5:30PM |
FT2.00007: Analytical Model for the Microwave Driven Double ICP Plasma Jet Ali Arshadi, Denis Eremin, Thomas Mussenbrock, Ralf Peter Brinkmann, Peter Awakowicz, Horia-Eugen Porteanu, Roland Gesche, Klaus Wandel For many technical applications, microwave driven plasma jets are possible alternatives to conventional RF plasma sources. Their construction is uncomplicated and they have the advantages of small size and large electrical efficiency. The microwave driven double ICP plasma jet is a recently developed variant. The core of the device is a cavity resonator with a resonance frequency close to 2 GHz. In good approximation, the resonator can be described as a circuit of two cylindrical one-turn coils parallel to a planar capacitor. Inside the coils are ceramic tubes which contain the plasma. Electromagnetic fields in the bulk and sheath reagion can be computed based on Maxwell's equations and the cold plasma model considering boundary conditions and the electric field due to the source on metalic cavity. A comparison of the simulation results with experimental data is performed. [Preview Abstract] |
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