Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session UF24: Plasma Modeling of Diverse Systems II |
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Chair: Astrid Raisanen, University of Michigan Room: Virtual GEC platform |
Friday, October 8, 2021 10:15AM - 10:30AM |
UF24.00001: Microwave Discharge Modeling with Resonance Power Absorption Xiaopu Li, Kallol Bera, Shahid Rauf Microwave discharges have become increasingly popular to produce reactive neutral and charged species at low electron temperature. For example, atmospheric-pressure micro-discharges have been extensively studied for electrical and biomedical applications. In semiconductor manufacturing, large-area microwave discharges can provide both high plasma density and low ion energy leading to high process throughput with low wafer damage in a wide process parameter space [1]. Theoretically, resonance power absorption has been proposed by Aliev et al for the efficient microwave heating mechanism [2]. The mode transition from under-dense to over-dense has been confirmed experimentally by Sugai et al [3]. In this study, microwave discharges at 2.45 GHz were investigated numerically in a cylindrical reactor with an azimuthal slot antenna. A fluid-based plasma model was coupled with the microwave power deposition from a frequency-domain electromagnetic solver. The under-dense to over-dense transition has been explored in Ar discharges at various power levels. The over-dense discharge shows high plasma density and low electron temperature because of the resonance power absorption near the critical density. Effect of the effective collision frequency was discussed in terms of plasma physics and numerical stability. The study provides a feasible model to design and control microwave discharges for large-area semiconductor processing. |
Friday, October 8, 2021 10:30AM - 10:45AM |
UF24.00002: Hybrid kinetic-continuum model for simulations of laser-induced plasma plumes Alexey N Volkov, Omid Ranjbar, Michael A Stokes, Zhibin Lin A two-dimensional hybrid computational model is developed for simulations of plumes induced by irradiation of metal targets by short and ultrashort laser pulses. The model includes a thermal model of the irradiated target and kinetic-continuum model of plasma plume. The thermal model is based on the heat conduction for short pulses and two-temperature model, which accounts for finite time of electron-phonon coupling in metals, for ultra-short pulses. The kinetic model of plasma flow is implemented in the form of the direct simulation Monte Carlo (DSMC) method generalized for plasma flows. The DSMC method is combined with both equilibrium ionization model based on Saha equations and non-equilibrium model, when the molar fractions of ions are calculated based on kinetic rates of ionization and recombination. The absorption model accounts for multiphoton ionization and inverse Bremsstrahlung. The model is applied for simulations of plasma plumes induced by irradiation of copper targets to the range of laser parameters, when the non-equilibrium effects are important for predicting the plasma shielding effect in material processing applications. |
Friday, October 8, 2021 10:45AM - 11:00AM |
UF24.00003: 3D PIC-MCC simulations of positive air-methane streamers for plasma-assisted combustion Dennis Bouwman, Jannis Teunissen, Ute Ebert We investigate the properties of positive streamers in a stochiometric air-methane mixture, motivated by plasma-assisted combustion. For this purpose we have performed large-scale simulations using a 3D particle-in-cell model. Methane requires additional electron impact cross sections that we have discussed in a recent paper Bouwman et al. (2021) [https://arxiv.org/pdf/2106.01935.pdf], and the photoionization of air (needed for positive streamer propagation) is reduced due to photon absorption by methane. We find that methane influences the dynamic poperties in several ways, mainly due to the short photoionization length: (1) the front becomes more unstable and branches often. (2) the velocity decreases while the maximum electric field increases (3) the tail of the EEDF is enhanced, with energies of 200 eV observed in a background field of 24 kV cm-1. Moreover, from our simulations we extract quantities relevant for plasma-assisted combustion at different applied voltages. For instance, we calculate the density of deposited energy which shows a very high peak exceeding 10 kJ m-3 which has the potential to evolve into an ignition kernel. Moreover we calculate the density of relevant chemical species and radicals produced by a streamer. |
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