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Computational Study on Transmission Spectra Considering Coaxial Cable of Cutoff Probes
염희중,채광석,김정형,이효창 한국진공학회 2024 Applied Science and Convergence Technology Vol.33 No.2
As nanoelectronic devices continue to shrink in response to demands for smaller and faster low-power, high-density devices, wasteful fabrication techniques are being replaced with methods that predetermine processing windows based on plasma parameter measurements. A cutoff probe comprising coaxial cables wrapped in Teflon is typically used for this measurement. However, because Teflon can be destroyed under highdensity plasma conditions, a change in the dielectric material of the coaxial cable may be considered for process plasma or high-density plasma measurements. However, the nature of these changes has not been examined. Hence, this study analyzes the plasma measurement characteristics of a cutoff probe using electromagnetic wave simulations and a plasma equivalent circuit model focusing on the dielectric permittivity and thickness of the coaxial cable-based cutoff probe. According to the results, as the dielectric constant of the insulator of the coaxial cable increased from 1 to 20, the transmission intensity at the cutoff frequency decreased from –68 to –81 dB. Furthermore, with the increased thickness of the insulator, the transmission intensity at the cutoff frequency increased from –80 to –64 dB. The characteristic changes are explained using a circuit model that verifies that changes to the insulator’s dielectric constant and thickness affect the characteristic impedance of the cable, but not the plasma density measured by the cutoff probe. Nevertheless, the intensity of the observed transmission spectrum is affected. Hence, these findings are expected to contribute to the optimization of cutoff probes used for high-density plasma parameter measurements.
박찬원,염희중,이효창,김정형 한국진공학회 2023 Applied Science and Convergence Technology Vol.32 No.5
As a radio frequency (RF) power and plasma process monitoring sensor, a voltage current (VI) probe has been utilized and developed to monitor and optimize plasma processes in semiconductor fabrication. However, many components are needed to deliver the RF power from the power supply to the plasma electrodes such as an RF connector and RF cable which affect the RF power transmission efficiency. Therefore, it is necessary to analyze the characteristics of RF power transmission lines with respect to the external parameter configuration using a VI probe. In this study, we investigated the characteristics of RF signals using a VI probe for various RF power transmission lines, including the VI probe installation position, RF connector type, and RF cable length. The RF signals were measured as a function of the input power in a lowpressure argon discharge. Consequently, the RF power loss was significant when long RF cables were used for the transmission line. Analyzing the characteristics of RF transmission lines using a VI probe can improve the reliability of RF measurement properties for plasma processing applications.
윤민영,염희중,정종렬,김정형,이효창 한국진공학회 2023 Applied Science and Convergence Technology Vol.32 No.2
Among the next-generation semiconductor manufacturing processes, plasma-assisted atomic layer etching (ALE) has garnered significant attention along with an increase in demand for damage-free and precise process technology. In typical ALE, an atomic layer is etched in each cycle by repeating a modification step through a chemical reaction using a reactive gas and a removal step through physical etching. Polymer-rich fluorocarbon gases, such as C4F8 and C4F6, are generally used as reactive gases for ALE to protect the sidewalls of high-aspect-ratio patterns. Compared with C4F8, C4F6 has a lower global warming potential and an excellent etch selectivity, thus, it can be a candidate for next-generation etching gas. Among the plasma sources for ALE, inductively coupled plasma (ICP) is widely used because of its low plasma potential and low electron temperature. Moreover, the ion energy and electron density in an ICP can be independently controlled using an additional bias system. In ALE performed using a radiofrequency (RF)-biased ICP, the plasma characteristics change in each step, because the reactive gas is injected and purged in the modification step, and a bias is applied in the removal step. Hence, an ALE process design or a recipe tuning based on an understanding of the plasma characteristics in each step is required for precisely controlling the process. This review introduces and discusses ALE process and plasma characteristics using RF-biased ICP and C4F6 (Hexafluoro-1,3-butadiene).
원통형 홀추력기에서 다중 하전된 이온을 고려한 제논 플라즈마 단순 모델
이장재,김시준(구성),이영석,염희중,성인호,정원녕,유신재 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
플라즈마 홀 추력기에서 내부 중심코어가 없는 형태의 원통형 홀 추력기(CHT)는 고리형 홀 추력기(AHT)에 비해 높은 이온 전류를 갖고 1보다 큰 연료 효율을 보였다. 이는 AHT에 비해 CHT 내 생성된 다중 하전된 이온의 높은 비율이 기여한 것임을 실험적으로 확인된 바 있다. 본 연구에서는 CHT 내 제논 플라즈마에 대한 간단한 글로벌 모델을 통해 다중 하전된 이온의 비율을 이론적으로 확인하였다. 전자 밀도에 대한 이온 및 가스 밀도, 전자 및 가스 온도 등 플라즈마 변수를 확인하였고, 높은 전자 밀도 영역에서 다중 하전된 이온의 비율이 높음을 확인하였다. 각 입자에 대한 상대 반응률을 통해 이온 밀도 계산 결과에 대해 해석하였다.