• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.182.2-182.2
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• 2016

Hollow cathode discharge(중공 음극)는 음극 표면에서 발생되는 2차 전자를 이용하여 높은 밀도의 플라즈마를 만들 수 있는 장점이 있다. 전원으로 microwave, RF, DC, pulsed dc등을 사용할 수 있으며 박막의 증착, 식각 등에 응용 가능하다. 물리적 현상으로는 중공 음극 재료 표면 물질의 가열 및 이온 스퍼터링, 2차 전자의 가열, 자기장 인가 구조의 경우 전자 거동이 있다. PIC(particle-in-cell)방식의 모델링과 fluid model을 이용한 방법이 있는데 본 연구에서는 상용 fluid model software인 ESI사의 CFD-ACE+를 사용하여 모델링 하였다. 구동 주파수는 13.56 MHz의 상용 고주파 전원과 보다 낮은 1 MHz, 100 kHz의 수치 모델을 이용하여 HF, MF, LF 영역에서의 동작 특성을 해석하였다. 1차적으로는 가스 유동의 특성을 2D, 3D로 조사하였고 플라즈마 거동은 2차원을 주로 진행하였으며 계산 시간이 오래 거리는 3차원 모델을 하나 만들어 그 특성을 조사하였다.

• Journal of the Korean institute of surface engineering
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• v.28 no.5
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• pp.267-275
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• 1995

Electron beam can provide convenient way to heat the substrate during Hollow Cathode Discharge (HCD) ion plating of Ti(C, N)films. Densification of columnar structrue is enhanced by longer duration of electron beam heating(EBH). While strong(111) texture is identified always to be formed, the amount of (200) oriented grains which coherently interfaced with carbide particles of the substrate increased with heating(EBH). In turns, these crystallogaphical change lead to the increase of micro hardness and adhesion of coating. Adhesion of Ti(C, N) films increased more dramatically in case of ASP30 substrate of which carbide particles dispersed more finely than M42. Therefore, it could be concluded that both the density of film and interfacial structure can affect the adhesion property. Overheating of substrate could be resulted in low adhesion resistance due to high residual stress developed in the film.

• Journal of the Korean Chemical Society
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• v.41 no.2
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• pp.113-116
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• 1997

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.11a
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• pp.57-57
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• 1998

최근 건식도금 분야에 있어서 경제성의 확보를 위해 고속 증착에 관한 연구가 활발히 진행 중에 있다. 이러한 고속 증착의 방법으로서는 high current arc, laser arc, hollow cathode discharge 및 magnetron sputtering법 등이 대두되고 있다. 특히 이중 magnetron sputtering 법은 고밀도의 박막을 고속으로 증착활 수 있는 장점으로 인해 고속 증착의 효과적인 방법으로 크게 대두되고 있다. 이러한 magnetron sputtering 법을 이용한 고속 증착에 관한 연구는 Cu, Ag와 같은 순수 금속 박막의 경우 $1~3\mu\textrm{m}/min$의 증착율까지 확보한 연구결과가 이미 발표되 고 있다. 그러나 이러한 고속 증착에 관한 연구들은 순금속 박막의 증착에 한정되어 있고 화합물 박막의 고속 증착에 관한 연구결과는 거의 전무한 결과이다. 따라서 본 연구에서는 magnetron sputtering 법을 이용하여 Ti계와 Cr계의 화합물 박막을 고속으로 증착하였다. 포한 박막의 증착율 및 특성 분석을 위혜 a-step, XRD 및 SEM을 이용하였다. 본 연구의 결과 $0.25~0.38\mu\textrm{m}/min$. 증착율을 확보하였으며 XRD 분석을 통하여 화합물 박막의 합성여부를 확인하였고, 박막의 미소 경도값도 2300~2500HK의 값을 얻었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.540-543
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• 2011

This work is devoted to an experimental investigation on conceptual design of dual consecutive stage micro plasma thruster (${\mu}PT$). Optimization study on the thruster configuration has been performed for various electrode gap distances from 1 mm to 2 mm and the hole diameter from 0.3 mm to 2 mm depending on desired operating conditions and corresponding nozzle design requirement. The operation of ${\mu}PT$ at low pressure from $10^{-1}$ Torr to $10^{-4}$ Torr and at various argon flow rates ranging from 5 sccm to 300 sccm has been studied to understand the physic of plasma and the gas dynamics in details. The specific impulse can reach up to 3000-4000 seconds at low power consumptions from 1 to 5 W. Image of exhaust plume from ${\mu}PT$ will be provided and electrical characteristics is also mentioned in this paper.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.254-254
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• 2013

마그네트론 스퍼터링은 그 단순한 구조로 인하여 신뢰성과 확장성이 높은 기술이다, 이로 인해 DLC, ITO 등의 산업 분야에서 많이 사용하는 박막 공정 기술이다. 하지만 인듐과 같은 희토류 금속의 가격이 최근 상승함에 따라 나타난 낮은 타겟 효율성의 문제와 낮은 파워 밀도로 인한 기판의 추가적인 bias 추가에 따른 비용상승, 그리고 reactive 스퍼터링 시 낮은 증착률 등의 문제점들 또한 존재한다. 이러한 단점들을 해결하기 위해 많은 연구들이 이루어 졌으며, 높은 파워 밀도를 위해 High power Impulse Plasma Magnetron Sputtering (HIPIMS) 기술과 타겟 사용률을 높이기 위한 High Target Utilization Sputtering (HITUS) 등의 기술 등이 개발되었다. 본 연구에서는 직류 전원을 사용한 High density Plasma Sputtering System (HIPASS)이라 명하는 고밀도 원거리 플라즈마 소스를 이용한 스퍼터링 이용해 증착한 박막의 특성을 연구 하였다. Hollow cathode discharge에서 발생한 고밀도 플라즈마가 외부 유도 자장 코일에 의하여 타겟 표면까지 도달하게 되며, 스퍼터링 타겟의 고전압 bias에 의해 플라즈마 이온들이 가속이 이루어져 스퍼터링 공정이 이루어 지게 된다. 본 연구의 공정에서 타겟 사용 효율은 최대 90%까지 이며, 원거리 플라즈마 소스에서의 이온으로 스퍼터링을 실시함으로 인해 스퍼터링 전압과 전류의 독립적인 조절이 가능 하다. 본 연구에서 HIPASS을 이용하여 기판에 추가적인 전압 인가 없이 Ti 타겟과 아르곤/질소 혼합가스를 사용하여 TiN 박막을 증착 하였다. TiN의 증착률은 약 44 nm/min였으며, 이 박막의 XRD 분석 결과 TiN (111), (200), (220) 면들이 관찰이 되었다. 높은 스퍼터링 입자 에너지에서 증착 된 TiN 박막에서 우선적으로 나타나는(200)과 (220) 면들이, 본 실험에서는 기판에 추가적인 전압인가 없이도 우선방위 성장을 보였다. 이 박막의 micro-hardness 측정 결과 약 34.7 GPa이며, 이는 UBM 이나 HIPIMS에서 보여주는 결과에 준하거나 그 이상의 수치이다. 이와 같은 결과는 본 연구에서 사용한 HIPASS 증착 공정이 높은 스퍼터링 입자 에너지를 가지기에 고밀도의 TiN 박막이 증착 된 결과로 볼 수 있다.

• Journal of the Korean Chemical Society
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• v.38 no.1
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• pp.34-40
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• 1994

First observation of uranium using a diode laser was published recently. The experiment was performed by the optogalvanic spectroscopy using diode lasers. A laser source causes the current change in a hollow cathode discharge lamp when metal atoms in plasma absorb the diode laser light. The optogalvanic signal is collected by detecting the current change. This work is the extended investigation of our previous research, the uranium detection using a diode laser. New electronic transitions of uranium and thorium in 775∼850 nm were investigated using diode lasers. In addition, the Rb(Ⅰ) optogalvanic spectra at 780.02 nm and 794.76 nm were studied. The Rb(Ⅰ) spectrum at 780.02 nm showed the isotopic features and hyperfine splittings. This work provides a key idea that the diode lasers are useful in the specrochemical analysis of the radioactive actinides that have a rich spectrum with transitions which can be easily reached with AlGaAs diode lasers. Also, this study shows that the diode lasers can be an important tool to find the spectroscopic parameters of actinides and rare earth elements which have not known.

• Analytical Science and Technology
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• v.11 no.1
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• pp.1-7
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• 1998

This study focuses on developing a controlling and analyzing software for the portable atomic emission spectrometer equipped with an electrothermal vaporizer(ETV) that can perform the in-situ trace analysis of heavy metal ions dissolved in water. The software works well for a notebook PC and it is exclusively developed for the real time analysis with a line filter and a photomultiplier light detector. The program is designed to operate under Windows 95 environment and either Korean or English can be used as a main language. The Delphi 2.0 language software is mainly used for programing. The program is designed to make a calibration curve and the system users can get the analytical data in a short time. And a final report can be generated without having difficulties. This software can be easily modified for other analytical atomic spectrometers.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.146-147
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• 2011

Processing a large area substrate for liquid crystal display (LCD) or solar panel applications in a capacitively coupled plasma (CCP) reactor is becoming increasingly challenging because of the size of the substrate size is no longer negligible compared to the wavelength of the applied radio frequency (RF) power. The situation is even worse when the driving frequency is increased to the Very High Frequency (VHF) range. When the substrate size is still smaller than 1/8 of the wavelength, one can obtain reasonably uniform process results by utilizing with methods such as tailoring the precursor gas distribution by adjustingthrough shower head hole distribution or hole size modification, locally adjusting the distance between the substrate and the electrode, and shaping shower head holes to modulate the hollow cathode effect modifying theand plasma density distribution by shaping shower head holes to adjust the follow cathode effect. At higher frequencies, such as 40 MHz for Gen 8.5 (2.2 m${\times}$2.6 m substrate), these methods are not effective, because the substrate is large enough that first node of the standing wave appears within the substrate. In such a case, the plasma discharge cannot be sustained at the node and results in an extremely non-uniform process. At Applied Materials, we have studied several methods of modifying the standing wave pattern to adjusting improve process non-uniformity for a Gen 8.5 size CCP reactor operating in the VHF range. First, we used magnetic materials (ferrite) to modify wave propagation. We placed ferrite blocks along two opposing edges of the powered electrode. This changes the boundary condition for electro-magnetic waves, and as a result, the standing wave pattern is significantly stretched towards the ferrite lined edges. In conjunction with a phase modulation technique, we have seen improvement in process uniformity. Another method involves feeding 40 MHz from four feed points near the four corners of the electrode. The phase between each feed points are dynamically adjusted to modify the resulting interference pattern, which in turn modulate the plasma distribution in time and affect the process uniformity. We achieved process uniformity of <20% with this method. A third method involves using two frequencies. In this case 40 MHz is used in a supplementary manner to improve the performance of 13 MHz process. Even at 13 MHz, the RF electric field falls off around the corners and edges on a Gen 8.5 substrate. Although, the conventional methods mentioned above improve the uniformity, they have limitations, and they cannot compensate especially as the applied power is increased, which causes the wavelength becomes shorter. 40 MHz is used to overcome such limitations. 13 MHz is applied at the center, and 40 MHz at the four corners. By modulating the interference between the signals from the four feed points, we found that 40 MHz power is preferentially channeled towards the edges and corners. We will discuss an innovative method of controlling 40 MHz to achieve this effect.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.361-366
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• 2010

Purpose: HCD ion plating apparatus by hollow cathod discharge method was fabricated and TiN films were deposited on stainless steel by this apparatus with increasing in $N_2$ gas flow and the fine color changes of TiN films were analyzed. Methods: The spectroradiometer and spectrophotometer were used to observe optically the fine color changes of TiN thin films, and XPS was used to analyze the compositions of TiN thin films with increasing in $N_2$ gas flow. Results: The color coordinate of TiN thin film with $N_2$ 120 sccm gas flow showed (0.382, 0.372) which had the mixed colors of gold and silver, and the color coordinate changed to the increasing value of (x,y) with increasing in $N_2$ gas flow which indicated the deep gold color. It was found that the slopes of the reflectances at 550nm were increased with increasing in $N_2$ gas flow. And from the Ti scans using XPS, it was found that the peak heights of 455 eV derived from TiN composition were increased with increasing in $N_2$ gas flow, while the peak heights of 459 eV from $TiO_2$ composition were decreased. Conclusions: The results obtained above were that the color of TiN film with 120 sccm $N_2$ gas flow had been observed from the mixed color of silver and gold due to TiC, $N_2$, TiN on the surface and TiN, $N_2$ inside film, and the color of TiN films changed a deep gold color with increasing in $N_2$ gas flow due to increasing TiN composition.