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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. [ABSTRACT FROM AUTHOR]

In this study, we examined the potential errors in plasma-density measurements using the cutoff probe method under various structural conditions, such as tip distance and length. Our studies indicate that under conditions of thin sheath thickness, the length or distance of the metal tips on the cutoff probe has a slight effect on the plasma transmission spectrum or cutoff frequency. However, under conditions with a notably thick sheath, the structure of the probe tip can cause an error of up to 2% between the measured cutoff frequency and actual plasma frequency. Consequently, for precise measurements of plasma density using the cutoff probe method, it is imperative to maintain a probe tip distance exceeding five times the sheath width and utilize a sufficiently long probe tip length. This finding is anticipated to provide essential guidelines for the design and fabrication of effective cutoff probes and enhance the accuracy of plasma-density measurements using a cutoff probe. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Herein, we investigated the effect of a dielectric film on the transmission spectrum of a bar-type flat cutoff probe (BCP). By conducting electromagnetic wave simulations, we found that placing a dielectric film with a thickness of 1 mm or less on the sensor did not affect the measurement of the BCP under thin sheath condition. However, a film thickness of 1 mm or more results in a low-frequency shift in the cutoff frequency. The shift in the cutoff frequency was related not only to the film thickness, but also to the dielectric constant of the film and sheath width, which could be understood through a circuit model of the BCP. The calculated results were experimentally validated using alumina plates of various thicknesses. Consequently, our findings demonstrate that measuring the electron density on a BCP is feasible even when a dielectric film is deposited, thereby improving the accuracy of the measurement. [ABSTRACT FROM AUTHOR]

Real-time monitoring of plasma parameters at the wafer plane is important because it significantly affects the processing results, yield enhancement, and device integrity of plasma processing. Various plasma diagnostic sensors, including those embedded in a chamber wall and on-wafer sensors, such as flat-cutoff sensors, have been developed for plasma measurements. However, to measure the plasma density on the wafer surface in real-time when processing plasma with bias power, such as in the semiconductor etching process, one must analyze the transmission spectrum of the flat-cutoff sensor in an environment with bias power applied. In this study, the transmission-spectrum and measured plasma-density characteristics of an electrode-embedded flat-cutoff sensor are analyzed via electromagnetic simulations and experiments under applied bias power. Our findings indicate that the flat-cutoff sensor accurately measures the plasma density, which is equivalent to the input plasma density under low bias power. Conversely, under high bias power, the plasma density measured by the sensor is lower than the input plasma density. Also, a thick-sheath layer is formed owing to the high bias power, which may complicate the measurement of plasma parameters using the flat-cutoff sensor. Plasma diagnostics using a flat-cutoff sensor in thick-sheath environments can be achieved by optimizing the flat-cutoff sensor structure. Our findings can enhance the analysis of plasma parameters on-wafer surfaces in processing environments with bias power applied. [ABSTRACT FROM AUTHOR]