Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session JW2: Capacitively Coupled Plasmas IIFocus
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Chair: Shahid Rauf, Applied Materials, Inc Room: 2a |
Wednesday, October 12, 2016 8:30AM - 9:00AM |
JW2.00001: Experimental and simulation study of capacitively coupled electronegative discharges Invited Speaker: Aranka Derzsi The application of tailored voltage waveforms, generated by using multiple harmonics of a base frequency, for the excitation of capacitive RF discharges has been recently introduced as a new method to control the ion flux and ion energy distribution at the electrodes. In plasma processing of surfaces complex mixtures of electronegative, reactive gases (e.g. CF$_{\mathrm{4}}$, O$_{\mathrm{2}})$ are usually required. Therefore, the question of whether this new approach to control ion properties can be applied efficiently to such systems is of exceptional importance. Here the electron heating and ionization dynamics, the possibilities and limitations of the efficient control of plasma parameters by voltage waveform tailoring in low-pressure capacitively coupled electronegative discharges are presented. The focus is on geometrically symmetric O$_{\mathrm{2}}$ plasmas, which are investigated by PIC/MCC simulations and experimental methods. O$_{\mathrm{2}}$ discharges driven by impulse-type and sawtooth-type voltage waveforms composed of a maximum of four consecutive harmonics are studied. Experimental results on the dc self-bias voltage, as well as the spatiotemporal distribution of the plasma emission are compared with simulation data for a wide range of operating conditions (fundamental driving frequencies of 5 MHz -- 15 MHz, at pressures of 50 mTorr -- 700 mTorr). Transitions between electron power absorption due to sheath expansion and the drift-ambipolar mode were induced both by changing the number of harmonics or by changing the gas pressure. A good agreement between simulation and experiment is found, which shows that the collision-reaction model for O$_{\mathrm{2}}$ discharges underlying the simulations describes reasonably the complicated chemistry of oxygen plasmas. An investigation of the dependence of the discharge characteristics on the surface destruction coefficient of the O$_{\mathrm{2}}$(a$^{\mathrm{1}}\Delta_{\mathrm{g}})$ singlet metastable molecules revealed the crucial role of these species, which strongly affects the negative ion balance of the plasma. [Preview Abstract] |
Wednesday, October 12, 2016 9:00AM - 9:15AM |
JW2.00002: Plasma Self-organization in Moderately High Pressure Capacitively Coupled RF Discharge. Anton Kobelev, Kallol Bera, John Forster, Alexander Smirnov Numerical simulation and experimental study of plasma self-organization in rf capacitively coupled discharge consisting of conductive plate with the rows of holes or slots between powered and return electrodes have been performed. It has been observed experimentally that there is a set of holes with increased luminosity in an almost periodic manner separated by darker holes in Ar discharge at 13.56 MHz at moderately high pressure (a few Torr). Two-dimensional Ar and He plasma simulations have been performed using electron kinetic model with non-local approach for multiple slots in the conductive plate. The result for Ar plasma shows that an initial perturbation of plasma density inside one slot increases, if initial perturbation is two times higher than that inside the rest of slots. The electron current enhances in this one slot that affects neighboring slots. Increase in electron current increases power deposition, and enhances plasma density further in this slot. If plasma density perturbation is increased in three neighboring slots, the perturbations inside all slots except one are damped. The slot with strong plasma density affects up to eight neighboring slots, which is close to periodicity observed experimentally. For He plasma, initial perturbation inside the slot dies down similar to experimental observation. [Preview Abstract] |
Wednesday, October 12, 2016 9:15AM - 9:30AM |
JW2.00003: Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics Giannis Tsigaras, Nikolaos Spiliopoulos, Eleftherios Amanatides, Dimitrios Mataras Despite the steps forward in the plasma processing of materials, there are still open issues concerning the design of plasma systems and the effective control of plasma parameters. In this work, a comparison between different methods for the measurement and calculation of discharge electrical characteristics is presented. The measurements were accomplished in a laboratory scale cylindrical 13.56 MHz CCP reactor and three different methods were tested: (a) A two port network based technique (b) A distributed element model method and (c) A method based on the solution of the wave equation. The differences between the results of these techniques are discussed in terms of the assumptions that are adopted in each of them. Moreover, the effect of electrode geometry on plasma electrical and microscopic properties was investigated. Two different electrodes were used and changes on the power transfer, plasma current and impedance were monitored together with variations of spatiotemporal emission in 13.56 MHz Ar discharges. Finally, the calculated delivered power error as a function of small measured errors for each method is presented. [Preview Abstract] |
Wednesday, October 12, 2016 9:30AM - 9:45AM |
JW2.00004: Fluid Modeling of a Very High Frequency Capacitively Coupled Reactor Rochan Upadhyay, Laxminarayan Raja, Peter Ventzek, Toshihiko Iwao, Kiyotaka Ishibashi Very High Frequency Capacitively Coupled Plasma (VHF-CCP) discharges have been studied extensively for semiconductor manufacturing applications for well over a decade. Modeling of these discharges however poses significant challenges owing to complexity associated with simulation of multiple coupled phenomena (electro-static/magnetic fields and plasma physics) over different scales and the representation of these phenomena in a computational framework. We present 2D simulations of a self-consistent plasma with the electromagnetic field represented using vector and scalar potentials. For a range of operating conditions, the ratio of capacitive and inductive power, calculated using empirical correlations available in the literature, are matched by adjusting both the electrostatic and electromagnetic fields in a decoupled manner. We present results using this model that demonstrate most of the important VHF-CCP discharge phenomena reported in the literature, such as electromagnetic wave versus electrostatic heating and its impact on plasma non-uniformity, wave resonances, etc. while realizing a practically feasible computational model. [Preview Abstract] |
Wednesday, October 12, 2016 9:45AM - 10:00AM |
JW2.00005: Consistent kinetic simulation of plasma and sputtering in low temperature plasmas Frederik Schmidt, Jan Trieschmann, Thomas Mussenbrock Plasmas are commonly used in sputtering applications for the deposition of thin films. Although magnetron sources are a prominent choice, capacitively coupled plasmas have certain advantages (e.g., sputtering of non-conducting and/or ferromagnetic materials, aside of excellent control of the ion energy distribution). In order to understand the collective plasma and sputtering dynamics, a kinetic simulation model is helpful. Particle-in-Cell has been proven to be successful in simulating the plasma dynamics, while the Test-Multi-Particle-Method can be used to describe the sputtered neutral species. In this talk a consistent combination of these methods is presented by consistently coupling the simulated ion flux as input to a neutral particle transport model. The combined model is used to simulate and discuss the spatially dependent densities, fluxes and velocity distributions of all particles. [Preview Abstract] |
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