Bulletin of the American Physical Society
70th Annual Gaseous Electronics Conference
Volume 62, Number 10
Monday–Friday, November 6–10, 2017; Pittsburgh, Pennsylvania
Session SR3: Capacitively Coupled Plasmas |
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Chair: Rochan Upadhyay, Esgee Technologies Inc. Room: Oakmont Junior Ballroom |
Thursday, November 9, 2017 1:30PM - 1:45PM |
SR3.00001: The effects of realistic heavy particle induced secondary electron emission coefficients on the electron power absorption dynamics in capacitively coupled plasmas Julian Schulze, Manaswi Daksha, Aranka Derzsi, Sebastian Wilczek, Jan Trieschmann, Thomas Mussenbrock, Peter Awakowicz, Zoltan Donko The effects of implementing energy-dependent secondary electron emission coefficients (SEEC) for ions and fast neutrals in PIC/MCC simulations of single and dual frequency capacitive discharges operated in argon are investigated. The surface conditions are taken into account, i.e. clean (heavily sputtered) and dirty (e.g. oxidized) metal surfaces are used. In single-frequency discharges the pressure and voltage at which the transition between the $\alpha $- and $\gamma $-mode occurs are found to be significantly different compared to simulations based on constant SEECs and to strongly depend on the surface conditions. In classical dual-frequency discharges the effective SEEC significantly increases as a function of the low-frequency voltage amplitude for dirty surfaces due to its effect on the heavy particle energies at the electrodes. This is found to negatively influence the quality of the separate control of ion properties at the electrodes. These new results on the separate control of ion properties indicate significant differences compared to previous results obtained with constant SEECs. [Preview Abstract] |
Thursday, November 9, 2017 1:45PM - 2:00PM |
SR3.00002: Nonlinear electromagnetics model of an asymmetrically driven capacitive discharge M.A. Lieberman, Emi Kawamura, A.J. Lichtenberg, De-Qi Wen It is well-known that standing waves exist in high frequency driven capacitive discharges and that capacitive sheaths can nonlinearly excite driving frequency harmonics near the series resonance that can be spatially near-resonant. The powered-electrode/plasma/grounded-electrode structure of an asymmetrically excited cylindrical discharge forms a three electrode system in which both $z$-symmetric and $z$-antisymmetric radially propagating wave modes exist. We develop a nonlinear electromagnetics model with radially- and time-varying sheath widths, incorporating both modes and plasma skin effects. The discharge is modeled as a uniform density bulk plasma with homogeneous or Child law sheaths at the electrodes, incorporating their nonlinear voltage versus charge relations. The model includes a finite power source resistance and a self-consistent calculation of the dc bias voltages. The resulting set of nonlinear partial differential equations is solved numerically to determine the symmetric and antisymmetric mode amplitudes and the nonlinearly-excited radially-varying harmonics of the two modes. Results are given for a 60 MHz, 10~mTorr chlorine discharge in a 50~cm diameter, 5~cm height chamber with a 30~cm diameter powered electrode. [Preview Abstract] |
Thursday, November 9, 2017 2:00PM - 2:15PM |
SR3.00003: Nonlinear interaction of capacitive discharges and power matching networks Frederik Schmidt, Jan Trieschmann, Ralf Peter Brinkmann, Thomas Mussenbrock External lumped element circuits attached to capacitively coupled plasmas are widely used e.g., in matching networks to maximize the absorbed power. At low pressures the plasma current often consists not only of a single driving-frequency but also of nonlinearly excited harmonics, which have been shown to be of strong influence on the absorbed power and, therefore, the plasma density [1]. The interaction between these harmonics and the external lumped element circuit has to be taken into account in order to achieve maximum power transfer from generator to plasma. For a full understanding of the underlying physics of this coupling a simulation which considers both the plasma and the circuit dynamics can provide useful insights. In this work a method is presented for coupling an equivalent circuit of the plasma to an electrical circuit composed of linear elements modeled with ngSPICE~[2]. This is used to investigate the nonlinear interaction of the matching network and capacitive discharges and especially its unexpected influence on the electron heating. \footnotetext[1]{T. Mussenbrock \textit{et al.}, Appl. Phys. Lett. \textbf{88}, 151503 (2006).} \footnotetext[2]{http://ngspice.sourceforge.net} [Preview Abstract] |
Thursday, November 9, 2017 2:15PM - 2:30PM |
SR3.00004: Customizing Capacitively Coupled Plasma Properties with Triple-Frequency Power Sources Chenhui Qu, Peng Tian, Shuo Huang, Mark J. Kushner As features sizes continue to shrink, control of reactive fluxes to wafers in capacitively coupled plasmas (CCPs) for semiconductor fabrication must become more precise. To achieve this control, additional frequencies having larger dynamic range are being investigated. In this paper, control of plasma properties in triple-frequency (TF) CCPs is computationally investigated, and compared to dual-frequency (DF) systems. The range of frequencies investigated are a few MHz to 100 MHz, with a standard configuration being two lower frequencies on the bottom electrode, and the high frequency on the top electrode. Electron energy distributions (EEDs) and reactant fluxes to the substrate in process relevant gas mixtures such as Ar/C$_{\mathrm{4}}$F$_{\mathrm{8}}$/O$_{\mathrm{2}}$, will be discussed while individually varying the power at different frequencies. The influence of the geometry (e.g., gap spacing and where power is applied) and the consequences of phase off-sets between frequencies in DF and TF systems on EEDs will also be discussed. [Preview Abstract] |
Thursday, November 9, 2017 2:30PM - 3:00PM |
SR3.00005: Tailoring charged particle distribution functions and chemical kinetics in non-thermal plasmas using multiple frequency excitation Invited Speaker: A. R. Gibson Plasmas driven by multiple frequencies in the radio-frequency range are used extensively in low-pressure plasma processing applications. In recent years, much research has focussed on a particular class of multiple frequency waveform composed of two or more harmonics of a given fundamental frequency with specific phase shifts between them. These are often termed ``tailored voltage waveforms''. Numerous publications have identified favourable control of ion energy distribution functions (IEDFs), crucial for surface processing applications, in low-pressure plasmas driven by these waveforms. However, the application of tailored voltage waveforms for the optimisation of alternative applications of low-temperature plasmas is less commonly studied. In this contribution, tailored voltage waveforms are explored for the control of the electron energy distribution function (EEDF), key for reactive species production, in atmospheric pressure plasma jets using experimental measurements and numerical simulations. Experimental measurements using phase resolved optical emission spectroscopy (PROES) show that tailoring the shape of the driving voltage waveform through changing the fundamental frequency, number of harmonics, and phase shift between them, has a pronounced effect on the spatio-temporal plasma emission. One-dimensional numerical simulations for the same conditions show excellent agreement with PROES measurements and are used to demonstrate wide ranging control of the EEDF and reactive species production as the shape of the voltage waveform is changed. [Preview Abstract] |
Thursday, November 9, 2017 3:00PM - 3:15PM |
SR3.00006: Investigation of Capacitively Coupled Plasma with electron beam by impedance analysis Inshik Bae, Hongyoung Chang In etching process, one of the key issue is to obtain high self-bias voltage for high ion energy. Therefore dual or triple frequencies Capacitively Coupled Plasma (CCP) has been widely used in etching process. However, if electron beam is added to CCP, the powered plate becomes negatively charged and it brings high self-bias voltage. Therefore we have investigated the dual frequencies CCP with electron beam because of its interesting property. Usually, Langmuir probe is widely used to investigate the plasma but we investigated the CCP with electron beam plasma by impedance analysis instead. The impedance analysis does not affect the plasma and it shows overall circuit characteristics of the plasma. Therefore it has some advantages compared with the Langmuir probe. However, it is not widely used analysis method so we studied the impedance analysis method and compared it with Langmuir probe. [Preview Abstract] |
Thursday, November 9, 2017 3:15PM - 3:30PM |
SR3.00007: Experimental evidence of nonlinear standing wave effect excited by higher harmonics in very high frequency capacitive discharges Kai Zhao, Yong-Xin Liu, You-Nian Wang Previous theory and experiment have demonstrated that the standing wave effect in very-high-frequency (VHF) capacitive discharge can cause severe plasma non-uniformity. In this work, the spatial distribution of electromagnetic field in a 100 MHz capacitively coupled argon discharge has been measured utilizing a newly designed high-frequency magnetic probe, combined with a resonance hairpin probe to determine the plasma density. Our results show that the radial profile of plasma density exhibits a center-peaked distribution at 3 Pa, suggesting a pronounced standing wave effect. Observed from the FFT spectra of the magnetic measurement results, it is found that the fundamental frequency component of magnetic field tends to be linear increased with the radial position, whereas its higher harmonic components turn out to be maximum at the positions between the reactor center and the electrode edge. Furthermore, with the increase of the harmonic order, the position corresponding to the maximum magnetic field can be clearly observed to shift toward to the reactor center. These results has demonstrated that the nonuniformity of the plasma density dominated by the standing wave effect could primarily ascribed to the higher harmonics close to the reactor center. [Preview Abstract] |
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