Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session ET2: Capacitively Coupled Plasmas I |
Hide Abstracts |
Chair: Thomas Mussenbrock, University of Cottbus, Germany Room: Century II |
Tuesday, October 29, 2019 1:45PM - 2:00PM |
ET2.00001: The Influence of $\gamma$- and $\delta$-Electrons on the Nonlocal Power Absorption in Capacitively Coupled Plasmas Katharina Noesges, Aranka Derzsi, Benedek Horvath, Julian Schulze, Thomas Mussenbrock, Ralf Peter Brinkmann, Sebastian Wilczek The generation of secondary electrons (SEs) in low pressure capacitively coupled radio frequency (CCRF) discharges is one part of the plasma surface interaction which strongly affects the electron dynamics. However, SEs, in particular electron induced SEs ($\delta$-electrons), are frequently neglected in theory and simulations. Especially at small gap sizes and high sheath voltages, the $\delta$-electrons dominate the ionization process and can significantly increase the plasma density. With the separation of $\gamma$-electrons and $\delta$-electrons, the electron power gain as well as the generation of each species can be understood on a nanosecond timescale. In order to study this issue, 1d3v particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations of a symmetric CCRF discharge are performed in the low pressure regime ($p \approx 1$ Pa). In this work, the gap size is varied and the effects of the nonlocal and nonlinear dynamics of $\gamma$-electrons and $\delta$-electrons on the discharge are investigated by using a realistic model for the electron-surface interactions. It is shown, that particularly for small gap sizes ($L_{\rm{gap}} < 30$ mm) the $\delta$-electrons dominate the discharge population of electrons in the range of 50\%. [Preview Abstract] |
Tuesday, October 29, 2019 2:00PM - 2:15PM |
ET2.00002: Surface processes in capacitive radio frequency discharges driven by tailored voltage waveforms Aranka Derzsi, Julian Schulze The influence of voltage waveform tailoring on the surface processes in multi-frequency Ar discharges with Cu electrodes are discussed, based on PIC/MCC simulations with realistic models for the description of the interaction of plasma particles with the boundary surfaces. We focus on the domain of low-pressures, where at high voltages the plasma particles can reach the electrodes at high energies and can induce significant secondary electron emission, as well as sputtering of the surface material. The variation of the mean energy of heavy-particles (ions and fast neutrals) at the electrodes by adjusting the phase angle of the driving harmonics influences the surface processes involving these particles. As the sputtering yields are functions of the bombarding heavy-particle energies, tuning the control parameter for the particle energies allows control of the flux of sputtered atoms at both electrodes. [Preview Abstract] |
Tuesday, October 29, 2019 2:15PM - 2:30PM |
ET2.00003: Secondary electron effect on sustaining capacitively coupled discharges: A hybrid modeling investigation of the ionization rate Ying-Ying Wen, Yu-Ru Zhang, Yuan-Hong Song, You-Nian Wang A one-dimensional fluid/Monte Carlo hybrid model was used to quantitatively study the secondary electron (SE) effect on sustaining the discharge by examining the ionization induced by bulk electrons (BEs) and SEs under different external discharge parameters. In single frequency discharges, the results indicate that as the voltage increases, SEs gain more energy from the stronger electric field. Therefore, the ionization region induced by SEs expands and the ionization rate becomes comparable to and even exceeds that of BEs. As the pressure increases, the ionization of SEs increases, and SEs gradually dominate the discharge. Besides, the profile of the SE ionization rate varies from flat to saddle-shape, due to the energy loss at the discharge center at higher pressures. When the discharge gap expands, the electron density in the case without SEs increases linearly, whereas the value first increases and then decreases in the model with SEs taken into account. In direct current (DC)/RF sources, the ionization induced by SEs first increases gently and then decreases with increasing DC voltage. Finally, the effect of SE in a pulsed discharges is studied. [Preview Abstract] |
Tuesday, October 29, 2019 2:30PM - 2:45PM |
ET2.00004: Spatio-temporal analysis of electron power absorption in low pressure CCPs operated in O2 Mate Vass, Sebastian Wilczek, Julian Schulze, Trevor Lafleur, Zoltan Donko, Ralf Peter Brinkmann The power absorption in electronegative CCPs at low pressures indicates complex electron dynamics that are still not fully understood. Therefore we present a spatio-temporally resolved analysis of electron power absorption in low pressure oxygen CCPs based on the first two moments of the Boltzmann-equation [1]. The spatio-temporal results are obtained self-consistently from 1d3v Particle-In-Cell / Monte Carlo Collision simulations. In contrast to typical theoretical models of electron heating, we observe significant ohmic heating and an attenuation of ambipolar heating at low pressures due to the strong electronegativity of the discharge. \\ \\$[1]$ Schulze J, Donk\'o Z, Lafleur T, Wilczek S, Brinkmann R P 2018 {\it Plasma Sources Sci. Technol.} {\bf 27}(5) 055010 [Preview Abstract] |
Tuesday, October 29, 2019 2:45PM - 3:00PM |
ET2.00005: Effect of driving frequency on electron heating mechanism and plasma parameters in a symmetric capacitive discharge under constant power density condition Nishant Sirse, Sarveshwar Sharma, Miles Turner Using particle-in-cell simulation technique, the effect of driving frequency on electron heating mechanism and plasma parameters is studied in a symmetric capacitively coupled argon plasma under constant power density conditions. It is observed that the plasma density first decreases and then increases with an increase in driving frequency suggesting a change in the heating mode transition. The time-averaged electron heating near to the sheath edge continue to increase with driving frequency, however, after the transition frequency, the negative and positive heating is observed near to the sheath edge and bulk plasma respectively. At higher driving frequencies, high frequency modulation in the instantaneous sheath edge position is observed, which trigger the multiple beams of electrons into the plasma. The electron sheath interaction and triggering of multiple beams of electrons is further studied for constant electron response time. Finally, the variation in the electron and ion energy distribution function is discussed. [Preview Abstract] |
Tuesday, October 29, 2019 3:00PM - 3:15PM |
ET2.00006: Student Excellence Award Finalist: A potential remedy for etched trench deformations based on voltage waveform tailoring and electric field reversal Florian Krüger, Sebastian Wilczek, Thomas Mussenbock, Julian Schulze The etching of sub micrometer high-aspect-ratio (HAR) features into dielectric materials in technological radio frequency plasmas is limited by the accumulation of positive surface charges inside etch trenches, causing reduced etch rates and feature deformations. These charge effects are, at least partially, caused by a difference in angle and velocity distributions of ions and electrons. Here, we demonstrate that using Voltage Waveform Tailoring, electric field reversals adjacent to the wafer can be generated and used to accelerate electrons into HAR features and compensate positive surface charges. Based on 1d3v Particle-in-Cell/Monte Carlo simulations of a capacitively coupled plasma operated in argon at 1 Pa, we study the effects of different voltage waveforms on this electric field reversal as well as on the electron velocity and angular distribution function at the wafer. We find that the angle of incidence of electrons relative to the surface normal can be strongly reduced and the electron velocity perpendicular to the wafer can be significantly increased by choosing appropriate waveforms. [Preview Abstract] |
Tuesday, October 29, 2019 3:15PM - 3:30PM |
ET2.00007: Electric field reversal and electron heating mode transition induced by magnetic field in capacitive oxygen discharges Li Wang, De-Qi Wen, Yuan-Hong Song, You-Nian Wang Using a one-dimensional Particle In Cell/Monte Carlo collision (PIC/MCC) model, we investigate the influence of magnetic field on capacitive oxygen discharges. When a magnetic field is imposed parallel to the electrode surfaces, the electron density is significantly increased due to their confinement by the magnetic field and the enhanced ionization efficiency, which is accompanied by a decreased electronegativity. More interestingly, when a driving frequency 13.56 MHz is set, electric field reversal and electron heating mode transition are observed by increasing the magnitude of magnetic field. From a comparison between the results from the PIC simulation and an analytical model, the reversed electric field is found to be induced by Lorentz force. When the discharge is conducted under a high frequency, i.e. 40.68 MHz, high frequency oscillations adjacent to the expanding sheath edges are weakened even disappear with the increase of the magnetic field, compared with the results obtained without applying the magnetic field. The disappearance of the oscillations also accompanied with an evident enhancement of electron heating by the electric field reversal. [Preview Abstract] |
Tuesday, October 29, 2019 3:30PM - 3:45PM |
ET2.00008: Electron heating in magnetized capacitively coupled discharges Bocong Zheng, Thomas Schuelke, Qi Hua Fan It is known that in capacitively coupled discharges, a small transverse magnetic field can induce a heating mode transition from a pressure-heating dominated state to an Ohmic-heating dominated state. Here, by using a particle-in-cell/Monte Carlo collision code, \textit{ASTRA}, and a moment analysis of the Boltzmann equation, we demonstrate that the enhancement of Ohmic heating is induced by the Hall current in the \textbf{\textit{E}} \texttimes \textbf{\textit{B}} direction. As the magnetic field increases, the Ohmic heating in the \textbf{\textit{E}} \texttimes \textbf{\textit{B}} direction dominates the total electron power absorption. The time-averaged pressure heating can be negative under strong magnetic fields. Electric field reversals are observed during the sheath collapse phase, because the motion of electrons is prohibited by the transverse magnetic field and cannot follow the sheath collapse, resulting in a reversed ambipolar electric field. The ratio of Ohmic heating in different directions can be well approximated from the electron gyration, the voltage, and the collision frequencies, implying that the electron heating of a magnetized CCP discharge can be estimated from the unmagnetized CCPs. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700