It is recognized that standing wave effects appearing in large-area, very-high-frequency capacitively coupled plasma (CCP) reactors cause center-high plasma non-uniformity. Using a high-frequency magnetic probe, we present a direct experimental diagnostic of the nonlinear standing waves and bulk ohmic electron power absorption dynamics in low pressure CCP discharges for different driving frequencies of 13.56, 30, and 60 MHz. The design, principle, calibration, and validation of the probe are described in detail. Spatial structures of the harmonics of the magnetic field, determined by the magnetic probe, were used to calculate the distributions of the harmonic current and the corresponding ohmic electron power deposition, providing insights into the behavior of nonlinear harmonics. At a low driving frequency, i.e. 13.56 MHz, no remarkable nonlinear standing waves were identified and the bulk ohmic electron power absorption was observed to be negligible. Here, the harmonic magnetic field/current was found to increase dramatically with the driving frequency, due to decreased sheath reactance and more remarkable nonlinear standing waves at a higher driving frequency, leading to the enhancements of the ohmic heating and the plasma density in the bulk, specifically at the electrode center. At a high driving frequency, i.e. 60 MHz, the high-order harmonic current density and the corresponding ohmic electron power absorption exhibited a similar node structure, with the main peak on axis, and one or more minor peaks between the electrode center and the edge, contributing to the center-high profile of the plasma density.
Zhao, Kai, et al. "Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges." Plasma Science and Technology, vol. 23, no. 11, Sep. 2021. https://doi.org/10.1088/2058-6272/ac1cce
Zhao, Kai, Liu, Yongxin, Zhang, Quanzhi, Economou, Demetre J., & Wang, Younian (2021). Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges. Plasma Science and Technology, 23(11). https://doi.org/10.1088/2058-6272/ac1cce
Zhao, Kai, Liu, Yongxin, Zhang, Quanzhi, et al., "Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges," Plasma Science and Technology 23, no. 11 (2021), https://doi.org/10.1088/2058-6272/ac1cce
@article{osti_1979462,
author = {Zhao, Kai and Liu, Yongxin and Zhang, Quanzhi and Economou, Demetre J. and Wang, Younian},
title = {Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges},
annote = {It is recognized that standing wave effects appearing in large-area, very-high-frequency capacitively coupled plasma (CCP) reactors cause center-high plasma non-uniformity. Using a high-frequency magnetic probe, we present a direct experimental diagnostic of the nonlinear standing waves and bulk ohmic electron power absorption dynamics in low pressure CCP discharges for different driving frequencies of 13.56, 30, and 60 MHz. The design, principle, calibration, and validation of the probe are described in detail. Spatial structures of the harmonics of the magnetic field, determined by the magnetic probe, were used to calculate the distributions of the harmonic current and the corresponding ohmic electron power deposition, providing insights into the behavior of nonlinear harmonics. At a low driving frequency, i.e. 13.56 MHz, no remarkable nonlinear standing waves were identified and the bulk ohmic electron power absorption was observed to be negligible. Here, the harmonic magnetic field/current was found to increase dramatically with the driving frequency, due to decreased sheath reactance and more remarkable nonlinear standing waves at a higher driving frequency, leading to the enhancements of the ohmic heating and the plasma density in the bulk, specifically at the electrode center. At a high driving frequency, i.e. 60 MHz, the high-order harmonic current density and the corresponding ohmic electron power absorption exhibited a similar node structure, with the main peak on axis, and one or more minor peaks between the electrode center and the edge, contributing to the center-high profile of the plasma density.},
doi = {10.1088/2058-6272/ac1cce},
url = {https://www.osti.gov/biblio/1979462},
journal = {Plasma Science and Technology},
issn = {ISSN 1009-0630},
number = {11},
volume = {23},
place = {United States},
publisher = {IOPScience},
year = {2021},
month = {09}}
University of Michigan, Ann Arbor, MI (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Natural Science Foundation of China (NSFC); China Postdoctoral Science Foundation; Fundamental Research Funds for the Central Universities; National Science Foundation (NSF)
Grant/Contract Number:
SC0001939
OSTI ID:
1979462
Journal Information:
Plasma Science and Technology, Journal Name: Plasma Science and Technology Journal Issue: 11 Vol. 23; ISSN 1009-0630
