Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session GT2: Capacitively Coupled Plasmas I |
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Chair: Aranka Derzsi, Hungarian Academy of Sciences Room: 2a |
Tuesday, October 11, 2016 4:00PM - 4:15PM |
GT2.00001: Influence of the normal modes on the plasma uniformity in large scale CCP reactors. Denis Eremin, Ralf Peter Brinkmann, Thomas Mussenbrock, Barton Lane, Masaaki Matsukuma, Peter Ventzek Large scale capacitively coupled plasmas (CCP) driven by sources with high frequency components often exhibit phenomena which are absent in relatively well understood small scale CCPs driven at low frequencies. Of particular interest are such phenomena which affect discharge parameters of direct relevance to the plasma processing applications. One of such parameters is plasma uniformity. By using a self-consistent 2d3v Particle-in-cell/Monte-Carlo (PIC/MCC) code parallelized on GPU we have been able to show that uniformity of the plasma generated is influenced predominantly by two factors, the ionization pattern caused by high-energy electrons and the average temperature of low-energy plasma electrons. The heating mechanisms for these two groups of electrons appear to be different leading to different transversal (radial) profiles of the corresponding factors, which is well captured by the kinetic PIC/MCC code. We find that the heating mechanisms are intrinsically connected with excitation of normal modes inherent to a plasma-filled CCP reactor. In this work we study the wave nature of these phenomena, such as their excitation, propagation, and interaction with electrons. [Preview Abstract] |
Tuesday, October 11, 2016 4:15PM - 4:30PM |
GT2.00002: Striations in electronegative capacitively coupled radio frequency plasmas Julian Schulze, Yong-Xin Liu, Edmund Schuengel, Ihor Korolov, You-Nian Wang, Zoltan Donko Self-organized spatial structures in the light emission from the ion-ion capacitive radio frequency plasma of an electronegative gas (CF$_{\mathrm{4}})$ are observed experimentally by Phase Resolved Optical Emission Spectroscopy for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These ``striations'' are found to be generated by a resonance between the external driving radio-frequency and the eigenfrequency of the ion-ion plasma that leads to a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma. The growth of the instability is followed by the numerical simulations [1]. The presentation introduces this effect conceptually and explains its physical origin. [1] Y.-X. Liu et al. 2016 Phys. Rev. Lett. accepted for publication [Preview Abstract] |
Tuesday, October 11, 2016 4:30PM - 4:45PM |
GT2.00003: Parametric investigations of striations in electronegative capacitively coupled radio-frequency plasmas Yong-Xin Liu, Edmund Schungel, Ihor Korolov, Zoltan Donko, Julian Schulze, You-Nian Wang Striated structures in light emission have been observed by Phase Resolved Optical Emission Spectroscopy (PROES) and analyzed based on particle-based kinetic simulations in capacitively coupled rf CF4 plasmas. On this basis, we conduct a systematic study on the effects of external parameters on the striated structure by PROES and particle-based kinetic simulations. Our results exhibit that at 100 Pa pressure and 300 V voltage amplitude striations generally occur within a certain driving frequency range, i.e., between 2 MHz and 18 MHz, and the distance between the ion density maxima decreases with rising driving frequency. A mode discharge transition from the “drift-ambipolar” into “striation” mode could be observed by increasing the pressure or rf voltage. The reasons for these observations are further understood by the analytical solution of a simply model of the ion-ion plasma. [Preview Abstract] |
Tuesday, October 11, 2016 4:45PM - 5:00PM |
GT2.00004: Two Dimensional Particle-in-cell/Monte Carlo (PIC/MC) Simulation of Radio Frequency Capacitively Coupled Plasmas with a Dielectric Side Wall Boundary Yue Liu, Jean-Paul Booth, Pascal Chabert The majority of previous two dimensional (usually fluid) simulations of radio frequency capacitively coupled plasmas have focused on geometrically-asymmetric reactors (with a much larger grounded electrode than power electrode), which produces a strong dc self-bias. However, a commonly-used geometry comprises electrodes of equal area surrounded by a dielectric side wall, but this has not been widely simulated. We have developed a two dimensional (Cartesian) PIC/MC code based on the work of Hongyu Wang, Wei Jiang and Younian Wang, to simulate argon plasmas in this kind of chamber. Even using a thick dielectric, a peak in plasma density and electron power deposition is adjacent to the dielectric. The profiles of the electron and ion fluxes show that the period-averaged currents to the powered electrode are not locally balanced; the electron flux peaks closer to the dielectric edge, before dropping sharply. Finally, the effect of the dielectric thickness on the surface charge distribution and the angular distributions of ions arriving at boundaries is examined. [Preview Abstract] |
Tuesday, October 11, 2016 5:00PM - 5:15PM |
GT2.00005: Virtual IED sensor at an rf-biased electrode in low-pressure plasma Maria Bogdanova, Dmitry Lopaev, Sergey Zyryanov, Alexander Rakhimov The majority of present-day technologies resort to ion-assisted processes in rf low-pressure plasma. In order to control the process precisely, the energy distribution of ions (IED) bombarding the sample placed on the rf-biased electrode should be tracked. In this work the “Virtual IED sensor” concept is considered. The idea is to obtain the IED “virtually” from the plasma sheath model including a set of externally measurable discharge parameters. The applicability of the “Virtual IED sensor” concept was studied for dual-frequency asymmetric ICP and CCP discharges. The IED measurements were carried out in Ar and H$_2$ plasmas in a wide range of conditions. The calculated IEDs were compared to those measured by the Retarded Field Energy Analyzer. To calibrate the “Virtual IED sensor”, the ion flux was measured by the pulsed self-bias method and then compared to plasma density measurements by Langmuir and hairpin probes. It is shown that if there is a reliable calibration procedure, the “Virtual IED sensor” can be successfully realized on the basis of analytical and semianalytical plasma sheath models including measurable discharge parameters. [Preview Abstract] |
Tuesday, October 11, 2016 5:15PM - 5:30PM |
GT2.00006: Precise measurements of neutral gas temperature using Fiber Bragg Grating sensor in Argon capacitively coupled plasmas Daoman Han, Zigeng Liu, Yongxin Liu, Wei Peng, Younian Wang Neutral gas temperature was measured using Fiber Bragg Grating sensor (FBGs) in capacitively coupled argon plasmas. Thermometry is based on the thermal equilibrium between the sensor and neutral gases, which is found to become faster with increasing pressure. It is also observed that the neutral gas temperature is higher than the room temperature by 10\textasciitilde 120 ${^\circ}$depending on the experiental conditions, and gas temperature shows significant non-uniformity in space. In addition, radial profiles of neutral temperature at different pressures, resemble these of ion density, obtained by a floating double probe. Specifically, at low pressure, neutral gas temperature and ion density peak at the center of the reactor, while the peak appears at the edge of the electrode at higher pressure. The neutral gas heating is mainly caused by the elastic collisions of Ar$+$ with neutral gas atoms in the sheath region after Ar$+$ gaining a certain energy. [Preview Abstract] |
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