• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.969-972
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. In this paper the effect of doping amounts of $Al_2O_3$ on the electrical, optical and morphological properties were investigated experimentally, The results show that the structural and electrical properties of the film are highly affected by the doping. The optimum growth conditions were obtained for films doped with 2 wt% of Al203 which exhibit a resistivity of $8.5{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 91.7 % for 840 nm in film thickness in the wavelength range of the visible spectrum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.143-146
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• 2003

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The influence of the substrate temperature, working gas pressure and discharge power on the electrical, optical and morphological properties were investigated experimentally. The consideration on the effect of doping amounts of Al on the electrical and optical properties of ZnO thin film were also carried out. ZnO:Al films with the optimum growth conditions showed resistivity of $9.42{\times}10^{-4}\;{\Omeg}-cm$ and transmittance of 90.88% for 840nm in film thickness in the wavelength range of the visible spectrum.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.78-80
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• 2018

본 논문은 용량성 결합 플라즈마 응용 시스템을 위한 전류형 토폴로지 기반의 전력 변환장치 구조를 제안한다. 제안된 시스템은 독립적으로 제어된 두 개의 고 정밀 펄스 전류를 부하로 출력하는 병렬 연결된 전류형 전력 변환장치로 구성된다. 전체 회로 토폴로지는 네 가지 세부 부분; 바이어스 전류 발생기, 바이어스 전류 모듈레이터, 슬롭 전류 발생기, 슬롭 전류 모듈레이터로 구성되어 있다. 제안된 시스템은 빠른 과도 특성을 위해 1200V/90A급 SiC MOSFET 스위치를 사용하였다. 제안된 전력 변환장치는 4.5kV의 출력전압, 40A급 출력전류와 100ns급 전류 상승/하강 특성을 충족시키도록 설계되었다. 본 연구는 펄스 전류형 전력 변환회로를 제안함으로써 전압형 전력 변환장치에 비해 전압 스파이크 및 전압 파형 왜곡을 줄여 보다 정확한 출력 전압을 발생시킴으로써 용량성 결합 플라즈마 시스템의 안정도 및 정밀도를 향상시킬 수 있다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1408-1409
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• 2007

In this paper, we developed a hybrid simulation model of carbon laser ablation under the Ar plasmas consisted of fluid and particle methods. Three kinds of carbon particles, which are carbon atom, ion and electron emitted by laser ablation, are considered in the computation. In the present modeling, we adopt capacitively coupled plasma with ring electrode inserted in the space between the substrate and the target, graphite. This system may take an advantage of ${\mu}m$-sized droplets from the sheath electric field near the substrate. As a result, in Ar plasmas, carbon ion motions were suppressed by a strong electric field and were captured in Ar plasmas. Therefore, a low number density of carbon ions were deposited upon substrate. In addition, the plume motions in Ar gas atmosphere was also discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.408-411
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• 2003

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The influence of the substrate temperature, working gas pressure, discharge power and doping amounts of Al on the electrical, optical and morphological properties were investigated experimentally. The effect of bias voltage on the electrical properties of ZnO thin film were also studied. Films with lowest resistivity of $5.4{\times}10^{-4}\;{\Omega}-cm$ have been achieved in case of films deposited at 1mtorr, $400^{\circ}C$ with a substrate bias of +10V for 840nm in film thickness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.939-942
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors were Prepared by using the capacitively coupled RF magnetron sputtering method. In this paper the effect of RF discharge power on the electrical, optical and structural properties were investigated experimentally. The results show that the structural and electrical properties of the film are highly affected by the variation of RF discharge power. The optimum growth conditions were obtained for films doped with 2 wt% of $Al_2O_3$ and 200 W in RF discharge power, which exhibit a resistivity of $10.4{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 89.66 % for 1000nm in films thickness in the wavelength range of the visible spectrum.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.93-93
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• 2016

Large scale integrated circuits (LSIs) has been improved by the shrinkage of the circuit dimensions. The smaller chip sizes and increase in circuit density require the miniaturization of the line-width and space between metal interconnections. Therefore, an extreme precise control of the critical dimension and pattern profile is necessary to fabricate next generation nano-electronics devices. The pattern profile control of plasma etching with an accuracy of sub-nanometer must be achieved. To realize the etching process which achieves the problem, understanding of the etching mechanism and precise control of the process based on the real-time monitoring of internal plasma parameters such as etching species density, surface temperature of substrate, etc. are very important. For instance, it is known that the etched profiles of organic low dielectric (low-k) films are sensitive to the substrate temperature and density ratio of H and N atoms in the H2/N2 plasma [1]. In this study, we introduced a feedback control of actual substrate temperature and radical density ratio monitored in real time. And then the dependence of etch rates and profiles of organic films have been evaluated based on the substrate temperatures. In this study, organic low-k films were etched by a dual frequency capacitively coupled plasma employing the mixture of H2/N2 gases. A 100-MHz power was supplied to an upper electrode for plasma generation. The Si substrate was electrostatically chucked to a lower electrode biased by supplying a 2-MHz power. To investigate the effects of H and N radical on the etching profile of organic low-k films, absolute H and N atom densities were measured by vacuum ultraviolet absorption spectroscopy [2]. Moreover, using the optical fiber-type low-coherence interferometer [3], substrate temperature has been measured in real time during etching process. From the measurement results, the temperature raised rapidly just after plasma ignition and was gradually saturated. The temporal change of substrate temperature is a crucial issue to control of surface reactions of reactive species. Therefore, by the intervals of on-off of the plasma discharge, the substrate temperature was maintained within ${\pm}1.5^{\circ}C$ from the set value. As a result, the temperatures were kept within $3^{\circ}C$ during the etching process. Then, we etched organic films with line-and-space pattern using this system. The cross-sections of the organic films etched for 50 s with the substrate temperatures at $20^{\circ}C$ and $100^{\circ}C$ were observed by SEM. From the results, they were different in the sidewall profile. It suggests that the reactions on the sidewalls changed according to the substrate temperature. The precise substrate temperature control method with real-time temperature monitoring and intermittent plasma generation was suggested to contribute on realization of fine pattern etching.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1485-1490
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• 2014

$SF_6$ gas has been used for power transformers or gas insulated switchgears, because it has the superior insulation property and the stable structure chemically. It has been, however, one of global warming gases and required to reduce the its amount. Some papers have reported that its amount could be reduced by mixing with other gases, such as $N_2$, $CF_4$, $CO_2$ and $C_4F_8$ and their mixture gases would cause the synergy effect. In this paper, we investigated the characteristics of DC plasmas on $SF_6$ mixture gases with $N_2$ at atmospheric pressure. $N_2$ gas is one of cheap gases and has been reported to show the synergy effect with mixing $SF_6$ gas, even though $N_2$ plasmas have electron-positive characteristics. 38 kinds of $SF_6/N_2$ plasma particles, which consisted of an electron, two positive ions, five negative ions, 30 excitation and vibration particles, were considered in a one dimensional fluid simulation model with capacitively coupled plasma chamber. The results showed that the joule heating of $SF_6/N_2$ plasmas was mainly caused by positive ions, on the other hand electrons acted on holding the $SF_6/N_2$ plasmas stably. The joule heating was strongly generated near the electrodes, which caused the increase of neutral gas temperature within the chamber. The more $N_2$ mixed-ratio increased, the less joule heating was. And the power consumptions by electron and positive ions increased with the increase of $N_2$ mixed-ratio.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.409-409
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• 2010

솔라셀은 차세대 대체 에너지 소스로 최근 큰 각광을 받고 있다. 솔라셀의 제조에 있어 가장 중요한 공정은 마이크로 결정질 및 비결정질 실리콘(uC-Si:H and a-Si:H) 박막을 증착하는 PECVD (Plasma Enhanced CVD)공정이다. 현재까지 이 증착공정을 위한 플라즈마 소스로 CCP(Capacitively Coupled Plasma)가 주로 사용되어 왔다. 그러나, CCP를 플라즈마 소스를 사용한 경우 솔라셀 대량 생산 적용시 다른 방법들에 비해 긴 공정 시간이 해결해야 할 문제점으로 대두되었다. 본 발표에서는 솔라셀의 대량 생산을 위한 마이크로 결정질 실리콘 박막 증착에 있어 현 시점에서 해결되어야 할 문제점에 대해 고찰해 보고자 한다. 현재까지 이러한 문제점들을 해결하기 위해 적용되어 왔던 플라즈마 소스들을 나열하고 이러한 플라즈마 소스에 대한 특성 및 문제점들을 고찰한다. 또한, PECVD 공정상의 문제점을 해결하기 위한 플라즈마 조건을 플라즈마 벌크에서의 전자에너지 분포를 기준으로 제시하고자 한다. 솔라셀용 결정질 실리콘 박막 증착용 플라즈마 소스로 hollow cathode 방전이 가장 유력시되고 있다. 본 연구에서는 CCP 플라즈마에서 hollow cathode 방전시 발생되는 플라즈마 특성에 대한 기초 연구를 제시한다. 기초 연구를 위해 다양한 불활성 가스인 아르콘, 헬륨, 크립톤 가스에 13.56 MHz의 RF 파워를 인가하고 방전되는 플라즈마 밀도 변화를 관찰하였다. 특히, 다양한 hole diameter에서 발생되는 플라즈마 밀도의 변화를 기존 평면 CCP 플라즈마의 밀도에 비교하여 분석함으로써 hole diameter에 따른 효과를 관찰하였다. 이러한 결과는 PIC 시뮬레이션을 통해 얻은 전자에너지 분포함수를 바탕으로 메커니즘을 논의하고자 한다. 마지막으로 솔라셀용 PECVD공정을 위해 고밀도 플라즈마 소스의 필요성뿐 만 아니라 대면적 소스의 구현에 대한 문제점을 고찰하였다. 대면적 공정에서 가장 중요한 핵심 연구 이슈는 공정 균일도를 높이는 것이다. CCP 플라즈마 소스에서 전극의 크기가 대면적화 됨에 따라 발생되는 전자기파 효과에 의한 불균일도에 대해 RF 전자기장 시뮬레이션을 통해 확인하고, 균일도 확보를 위한 방안에 대한 논의하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.478-478
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• 2012

Recently, there are many researches in order to increase the deposition rate (D/R) and improve film uniformity and quality in the deposition of microcrystalline silicon thin film. These two factors are the most important issues in the fabrication of the thin film solar cell, and for the purpose of that, several process conditions, including the large area electrode (more than 1.1 X 1.3 (m2)), higher pressure (1 ~ 10 (Torr)), and very high frequency regime (VHF, 40 ~ 100 (MHz)), have been needed. But, in the case of large-area capacitively coupled discharges (CCP) driven at frequencies higher than the usual RF (13.56 (MHz)) frequency, the standing wave and skin effects should be the critical problems for obtaining the good plasma uniformity, and the ion damage on the thin film layer due to the high voltage between the substrate and the bulk plasma might cause the defects which degrade the film quality. In this study, we will propose the new concept of the large-area multi-electrode (a new multi-electrode concept for the large-area plasma source), which consists of a series of electrodes and grounds arranged by turns. The experimental results with this new electrode showed the processing performances of high D/R (1 ~ 2 (nm/sec)), controllable crystallinity (~70% and controllable), and good uniformity (less than 10%) at the conditions of the relatively high frequency of 40 MHz in the large-area electrode of 280 X 540 mm2. And, we also observed the SEM images of the deposited thin film at the conditions of peeling, normal microcrystalline, and powder formation, and discussed the mechanisms of the crystal formation and voids generation in the film in order to try the enhancement of the film quality compared to the cases of normal VHF capacitive discharges. Also, we will discuss the relation between the processing parameters (including gap length between electrode and substrate, operating pressure) and the processing results (D/R and crystallinity) with the process condition map for ${\mu}c$-Si:H formation at a fixed input power and gas flow rate. Finally, we will discuss the potential of the multi-electrode of the 3.5G-class large-area plasma processing (650 X 550 (mm2) to the possibility of the expansion of the new electrode concept to 8G class large-area plasma processing and the additional issues in order to improve the process efficiency.