Do-Yeon Hwang

Korea Research Institute of Standards and Science

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H. J. Yeom

Korea Research Institute of Standards and Science

Jung‐Hyung Kim

Korea Research Institute of Standards and Science

Hyo‐Chang Lee

Korea Aerospace University

Ga‐Won Lee

Dongduk Women's University

Gwang-Seok Chae

Korea Aerospace University

S Park

Korea Research Institute of Standards and Science

Young-Joo Kim

Yonsei University

Young-Gi Kim

Korea Institute of Fusion Energy

Cooperative Institutions

Korea Research Institute of Standards and Science

Daejeon University

Yonsei University

Chungnam National University

Korea University of Science and Technology

Seoul National University

Samsung (South Korea)

Korea Advanced Institute of Science and Technology

Korea Aerospace University

Dongduk Women's University

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Transmission spectrum analysis of ceramic-shielded microwave cutoff probes in low-pressure plasmas

Journal of Applied Physics (2024)

Do-Yeon Hwang H. J. Yeom Ga‐Won Lee Jung‐Hyung Kim Hyo‐Chang Lee

In this study, the influence of ceramic shield characteristics, including thickness and geometry, on the transmission spectrum and electron density measurements of a ceramic shield cutoff probe (CSC) was investigated to measure high-density or process plasma. Through electromagnetic simulations and circuit modeling, we examined the measurement characteristics of the CSC based on different ceramic shield geometries. When the ceramic shield is sufficiently thin, it does not affect the CSC wave transmission characteristics. However, for a thick ceramic shield, a cutoff frequency shift of up to 3% toward the lower side can occur. This shift is attributed to the electrical properties of the ceramic material, which can function as a parasitic capacitor. In addition, when fabricating a CSC, depending on the shape of the ceramic shield or the method used to couple it with the CSC body, a cutoff frequency shift can occur toward the lower side. The simulation results were validated through experiments, revealing a cutoff frequency shift toward the lower side of up to 18.0% in the simulations and up to 11.6% in the experiments. The findings of this study could assist in high-density or processing plasma measurements using cutoff probes.

Cutoff frequency

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10.1063/5.0214696

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Analysis of the transmission spectrum of the microwave cutoff probe influenced by the sheath around the probe

Journal of Applied Physics (2023)

H. J. Yeom Young-Gi Kim Gwang-Seok Chae Do-Yeon Hwang Jung‐Hyung Kim

We investigated the effect of the sheath around the probe tips on the transmission spectrum of a cutoff probe using an electromagnetic simulation and a circuit model. Our results show that the width of the sheath can change the transmission spectrum, which can affect the absolute value of the electron density. In a real-world cutoff probe structure, this effect may become apparent in a low-density plasma or when a high bias voltage is applied to the plasma. The key factor is capacitance, which contains the sheath component. In the case of a low-density plasma, the change in the sheath capacitance of the sheath region contributes to the shift in the resonant frequency. For thick sheath widths, at least a 5% discrepancy can occur between the actual plasma frequency and the measurement owing to variations in the capacitance, particularly the sheath components surrounding the probe. We expect that this study will facilitate reduction in the measurement error and uncertainty in microwave cutoff probe measurements, particularly when applied to low-density plasma measurements.

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Debye sheath

10.1063/5.0145958

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Measurement of electron density in high-pressure plasma using a microwave cutoff probe

Journal of Applied Physics (2024)

S Park H. J. Yeom Do-Yeon Hwang Young-Joo Kim Hyo‐Chang Lee

Despite the widespread applications of high-pressure plasma in semiconductor and display industry, such as deposition and ashing process, the use of cutoff probes for diagnosing high-pressure plasma was rarely studied. In this study, we investigated a method of measuring electron density in a cutoff probe using the resonance peak in a high-pressure plasma environment. This method is validated through both electromagnetic wave simulations and experimental methodologies. Our findings reveal that the proposed method demonstrates discrepancies of less than 1.47% compared to the input plasma frequency in the results of electromagnetic wave simulations at a gas pressure of 10 mTorr, while at 2.5 Torr, it exhibited a maximum discrepancy of 13.3% when selecting resonance frequencies lower than the electron–neutral collision frequency. This discrepancy at high pressure is reduced to within 1.92% by selecting a resonance frequency higher than the electron–neutral collision frequency. Also, the feasibility of these electron density measurements has been confirmed under conditions of high gas pressure where the cutoff frequency is not measurable, as evidenced by both simulation and experimental results. Our research on the diagnostic methods in high-pressure plasmas could significantly enhance the measurement and interpretation of plasma parameters in various industrial processes.

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10.1063/5.0233192

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