• 한국진공학회지
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• 제19권5호
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• pp.331-340
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• 2010

초고주파 다중 중공 음극 방전을 이용한 플라즈마 화학 기상 증착 장치를 3차원 수치 모델링하였다. 기본적인 방전 특성을 파악하기 위하여 알곤 플라즈마를 40 MHz, 100 V, 133.3 Pa (1 Torr)의 조건에 대해서 계산하였다. 6 mm 직경의 홀을 20 mm 간격으로 배열하였고 전극 간격은 10 mm를 가정하였다. 피크 플라즈마 밀도는 홀의 하부 중앙에서 $5{\times}10^{11}#/cm^3$ 였으며 전자 온도는 접지 상태로 가정한 기판과 챔버 벽면 주위에서 가장 높았다. 준안정 상태에 의한 2단 이온화 속도는 전자 충돌에 의한 직접 이온화보다 10배 가량 높았다. 수소에 대한 계산에서는 이온화 이외의 다양한 에너지 소모 경로가 있어서 방전의 국재화가 잘 이루어지지 않았다.

• 한국진공학회지
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• 제19권1호
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• pp.36-44
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• 2010

관경이 수 mm인 세관 램프 내부에서 플라즈마의 확산을 조사하기 위하여 이극성(ambipolar) 확산방정식을 해하였다. 반경 방향의 확산에 의한 유리관 벽에서의 플라즈마 소멸 특성시간은 $\tau_r\;=\;(r_0/2.4)^2/D_a$로 주어진다. 반경 $r_0{\sim}1\;mm$이고 이극성 확산계수 $D_a{\sim}0.01\;m^2/s$ 이면, $\tau_r{\sim}17\;{\mu}s$이다. 이는 램프의 교류전원 구동에서 플라즈마를 유지하기 위한 구동 최소 주파수 ~30 kHz에 해당한다. 고전압이 인가되는 전극부에 발생한 고밀도의 플라즈마가 양광주로 확산되는 특성시간은 $\tau_z{\sim}0.1\;s$이다. 고밀도 플라즈마 경계에서의 시간에 대한 확산속도는 $t{\sim}10^{-6}\;s$일 때 $u_D{\sim}10^2\;m/s$이고, $t{\sim}10^{-3}\;s$이면 그 속도는 $u_D{\sim}1\;m/s$로 느려진다. 따라서 램프 길이 ~1 m에 대하여 전극부에서 생성된 고밀도 플라즈마가 양광주 전체로 확산되는 시간은 수 초가 걸린다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.31-36
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• 2003

We investigated dry etching of GaAs and AlGaAs in a high density planar inductively coupled plasma system with $BCl_3$ and $BCl_3/Ar$ gas chemistry. A detailed process study as a function of ICP source power, RIE chuck power and $BCl_3/Ar$ mixing ratio was performed. At this time, chamber pressure was fixed at 7.5 mTorr. The ICP source power and RIE chuck power were varied from 0 to 500 W and from 0 to 150 W, respectively. GaAs etch rate increased with the increase of ICP source power and RE chuck power. It was also found that etch rate of GaAs in $BCl_3$ gas with 25% Ar addition was superior to that of GaAs in a pure $BCl_3$ (20 sccm $BCl_3$) plasma. The result was same with AlGaAs. We expect that high ion-assisted effect in $BCl_3$/Ar plasma increased etch rates of both materials. The GaAs and AIGaAs features etched at 20 sccm $BCl_3$ and $15BCl_3/5Ar$ with 300 W ICP source power, 100 W RIE chuck power and 7.5 mTorr showed very smooth surfaces(RMS roughness < 2 nm) and excellent sidewall. XPS study on the surfaces of processed GaAs also proved extremely clean surfaces of the materials after dry etching.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.1127-1130
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• 2003

The characteristics of silicon nitride films deposited in a planar coil reactor using a simple high-density inductively coupled plasma chemical vapor deposition technique have been investigated. The process gases used during silicon nitride deposition cycle were pure nitrogen and a mixture of silane and helium. It has been pointed out that the strong H-atom released from the growing SiN film and Si-N bond healing are responsible for the improved electrical and passivation properties of SiN.

• Transactions on Electrical and Electronic Materials
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• 제15권3호
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• pp.164-169
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• 2014

We investigated the etching characteristics of $HfAlO_3$ thin films in $O_2/Cl_2/Ar$ and $O_2/BCl_3/Ar$ gas, using a high-density plasma (HDP) system. The etch rates of the $HfAlO_3$ thin film obtained were 30.1 nm/min and 36 nm/min in the $O_2/Cl_2/Ar$ (3:4:16 sccm) and $O_2/BCl_3/Ar$ (3:4:16 sccm) gas mixtures, respectively. At the same time, the etch rate was measured as a function of the etching parameter, namely as the process pressure. The chemical states on the surface of the etched $HfAlO_3$ thin films were investigated by X-ray photoelectron spectroscopy. Auger electron spectroscopy was used for elemental analysis on the surface of the etched $HfAlO_3$ thin films. These surface analyses confirm that the surface of the etched $HfAlO_3$ thin film is formed with nonvolatile by-product. Also, Cl-O can protect the sidewall due to additional $O_2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.75-79
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• 2003

We studied InP etch results in high density planar inductively coupled $BCl_3$ and $BCl_3$/Ar plasmas. The investigated process parameters were ICP source power, RIE chuck power, chamber pressure and $BCl_3$/Ar gas composition. It was found that increase of ICP source power and RIE chuck power raised etch rate of InP, while that of chamber pressure decreased etch rate. Etched InP surface was clean and smooth (RMS roughness < 2 nm) with a moderate etch rate ($300\;{\sim}\;500\;{\AA}/min$) after the planar $BCl_3/Ar$ ICP etching. It may make it possible to open a new regime of InP etching with $CH_4/H_2$ - free plasma chemistry. Some amount of Ar addition (< 50%) also improved etch rates of InP, while too much Ar addition reduced etch rates of InP.

• 한국표면공학회지
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• 제29권6호
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• pp.824-828
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• 1996

Co-based alloy thin films ddeposited by fcing targets sputtering(FTS) were investigated for use in high-density magnetic recording media to determine how their magnetic properties are dependent on the sputtering conditions, and thus to find appropriate parameters that allow the sputtering and thin films to meet the specificiations for magnetic properties. FTS can discharge at lower working gas pressure than other sputtering methods such as dcmagnetron sputteing because the plasma is sufficiently confined by a magnetic field applied perpendicular to both of the target planes, which results in plasma-free substrates. Co-Cr-Ta films were deposited by FTS on glass and silicon substrates at substrate temperature between room temperature and $350^{\circ}C$, and at argon gas pressure between 0.1 and 10mTorr. The films were also deposited on polyimide tapes at substrate temperature of $130^{\circ}C$ and argon gas pressure of 1 mTorr. The effective advantages of Ta as an additional element were investigated, using the same films on the tapes. As a result of the experiment, it was found that better magnetic properties were obtained in the ranges of higher temperature and lower argon gas pressure with background pressure in thr range of $1.5 \times 10^{-6}$ Torr. Ta addition at 2 to 4 atomic percent almost havled the Co-Cr grain sizes, indicating that Ta addition at an appropriate atomic percent is effective for improving the microstructure and characteristics of Co-Cr films.

• 한국가금학회:학술대회논문집
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• 한국가금학회 2000년도 제17차 정기총회 및 학술발표
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• pp.14-35
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• 2000

There have been growing interests in olive oil, which is attributed to the beneficial health effects of the Mediterranean diet. Numerous studies suggest that oleic acid, the major fatty acid in olive oil, may contribute to less incidence of coronary heart disease(CHD) in the Mediterranean area. Although the major effects of high monounsaturated fatty acid(MUFA) consumption on lowered plasma cholesterol are generally attributed to the consequential replacement of saturated fatty acid in diets, some studies have shown a modest cholesterol lowering effect of MUFA alone when it replaces dietary carbohydrate at an equal amount of energy. Furthermore, MUFA increases the level of the protective high-density lipoprotein cholesterol more than polyunsaturated fatty acid(PUFA) does when these two classes of fatty acids replace carbohydrates in the diet. It has been generally recommended that optimal dietary fat should be rich in MUFA, such as oleic acid, low in saturated fatty acids and provide adequate amounts of PUFA. However, no conclusive observations have been made yet mainly due to a difficulty in controlling the proportion of oleic acid without adjusting the levels of the other fatty acids to be constant, which could also affect plasma cholesterol levels. Recent findings also suggest that dietary PUFA results in higher tendency toward lipid peroxidation whereas with MUFA the susceptibility of low density lipoprotein to oxidative stress is reduced. More studies are needed to clarify the effects of MUFA on reducing the incidence of CHD.

• 한국분말재료학회지
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• 제30권5호
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• pp.436-441
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• 2023

Molybdenum-tungsten (Mo-W) alloy sputtering targets are widely utilized in fields like electronics, nanotechnology, sensors, and as gate electrodes for TFT-LCDs, owing to their superior properties such as high-temperature stability, low thermal expansion coefficient, electrical conductivity, and corrosion resistance. To achieve optimal performance in application, these targets' purity, relative density, and grain size of these targets must becarefully controlled. We utilized nanopowders, prepared via the Pechini method, to obtain uniform and fine powders, then carried out spark plasma sintering (SPS) to densify these powders. Our studies revealed that the sintered compacts made from these nanopowders exhibited outstanding features, such as a high relative density of more than 99%, consistent grain size of 3.43 ㎛, and shape, absence of preferred orientation.

• 천문학회보
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• 제37권1호
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• pp.97-97
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• 2012

Hinode/XRT has observed coronal mass ejections (CMEs) since it launched on Sep. 2006. Observing programs of Hinode/XRT, called 'CME watch', perform several binned observations to obtain large FOV observations with long exposure time that allows the detection of faint CME plasmas in high temperatures. Using those observations, we determine the upper limit to the mass of hot CME plasma using emission measure by assuming the observed plasma structure. In some events, an associated prominence eruption and CME plasma were observed in EUV observations as absorption or emission features. The absorption feature provides the lower limit to the cold mass while the emission feature provides the upper limit to the mass of observed CME plasma in X-ray and EUV passbands. In addition, some events were observed by coronagraph observations (SOHO/LASCO, STEREO/COR1) that allow the determination of total CME mass. However, some events were not observed by the coronagraphs possibly because of low density of the CME plasma. We present the mass constraints of CME plasma and associated prominence as determined by emission and absorption in EUV and X-ray passbands, then compare this mass to the total CME mass as derived from coronagraphs.