• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.95-95
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• 2013

박막 공정 기술은 반도체 및 디스플레이뿐만 아니라 대부분의 전자소자에 적용되는 매우 중요한 기술이다. 그 중, 마그네트론 스퍼터링 공정은 플라즈마를 이용하여 금속 및 세라믹 등의 벌크 물질을 박막으로 증착 가능한 가장 널리 사용되는 방법 중의 하나이다. 하지만, Fe, Co, Ni 같은 강자성체 재료는 공정이 불가능하며, 스퍼터링 타겟 효율이 40% 이하이고, 제한적인 방전압력 범위 및 전류 상승에 의한 높은 전압 인가 제한이 있다는 단점이 있다. 본 연구에서 사용된 고밀도 플라즈마 소스를 적용한 고효율 스퍼터링 시스템은 할로우 음극을 이용한 원거리에서 고밀도 플라즈마를 생성하여 전자석 코일을 통해 자석이 없는 음극으로 이온을 수송시켜 스퍼터링을 일으킨다. 따라서 강자성체 재료의 스퍼터링이 가능하며, 90% 이상의 타겟 사용 효율 구현 및 기존 마그네트론 스퍼터링 대비 고속 증착이 가능하다. 또한, $10^{-4}$ Torr 압력영역에서 방전 및 스퍼터링이 가능하다. 타겟 이온 전류를 타겟 인가 전압과 관계없이 0~4 A까지, 타겟 이온 전류와 상관없이 타겟 인가 전압을 70~1,000 V 이상까지 독립적으로 제어가능하다. 또한 TiN과 같은 질소 반응성 공정에서 반응성 가스인 질소를 40%까지 넣어도 타겟에 수송되는 이온의 양에 영향이 없다. 할로우 음극 방전 전류 40 A에서 발생된 플라즈마의 이온에너지 분포는 55 eV에서 가우시안 분포를 보였으며, 플라즈마 포텐셜인 sheath drop은 74 V 였다. OES를 통한 광학적 진단 결과, 전자석에 의한 이온빔 초점에 따라 플라즈마 이온화율을 1.8배까지 증가시킬 수 있으며, 할로우 음극 방전 전류가 60~100 A로 증가하면서 플라즈마 이온화율을 6배까지 증가 가능하다. 또한, 타겟 이온 전류와 관계없이 타겟 인가 전압을 300~800 V로 증가시킴에 따라 Ar 이온 밀도의 경우 1.4배 증가, Ti 이온 밀도의 경우 2.2배 증가시킬 수 있었으며, TiN의 경우 증착 속도도 16~44 nm/min으로 제어가 가능하다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.816-820
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• 2013

We investigated the characteristics of the silicon oxy-nitride and nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) at the low temperature with a varying $NH_3/N_2O$ mixing ratio and a fixed $SiH_4$ flow rate. The deposition temperature was held at $150^{\circ}C$ which was the temperature compatible with the plastic substrate. The composition and bonding structure of the nitride films were investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Nitrogen richness was confirmed with increasing optical band gap and increasing dielectric constant with the higher $NH_3$ fraction. The leakage current density of the nitride films with a high NH3 fraction decreased from $8{\times}10^{-9}$ to $9{\times}10^{-11}(A/cm^2$ at 1.5 MV/cm). This results showed that the films had improved electrical properties and could be acceptable as a gate insulator for thin film transistors by deposited with variable $NH_3/N_2O$ mixing ratio.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.886-891
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• 2008

Contact glow discharge electrolysis(CGDE) is an unconventional electrolysis where plasma is sustained by D.C. glow discharge between an electrode and the surface of electrolyte surrounding it at high voltage. In this study, the behavior of CGDE in NaCl solution and the depolymerization of fucoidan by CGDE were investigated. After onset of CGDE, increase of voltage enhanced Glow discharge which resulted in low current density and low temperature in NaCl electrolyte. From the variation of molecular weight of fucoidan with the reaction time, it was demonstrated that the degradation of fucoidan followed a first-order rate law. Molecular weight of fucoidan treated with CGDE was about 40 times lower compared to initial fucoidan without content decrease of sulfate and fucos.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.701-709
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• 2011

In semiconductor wafer fabrication, etching is one of the most critical processes, by which a material layer is selectively removed. Because of difficulty to correct a mistake caused by over etching, it is critical that etch should be performed correctly. This paper proposes a new approach for etch endpoint detection of small open area wafers. The traditional endpoint detection technique uses a few manually selected wavelengths, which are adequate for large open areas. As the integrated circuit devices continue to shrink in geometry and increase in device density, detecting the endpoint for small open areas presents a serious challenge to process engineers. In this work, a high-resolution optical emission spectroscopy (OES) sensor is used to provide the necessary sensitivity for detecting subtle endpoint signal. Partial Least Squares (PLS) method is used to analyze the OES data which reduces dimension of the data and increases gap between classes. Support Vector Machine (SVM) is employed to detect endpoint using the data after PLS. SVM classifies normal etching state and after endpoint state. Two data sets from OES are used in training PLS and SVM. The other data sets are used to test the performance of the model. The results show that the trained PLS and SVM hybrid algorithm model detects endpoint accurately.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1993-1998
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• 2011

Semiconductor industry needs to have fine patterns in order to fabricate the high density integrated circuit. For nano-scale patterns, hard-mask is used to multi-layer structure which is formed by CVD (chemical vaporized deposition) process. In this work, we prepared single-layer hard-mask by using organic-inorganic hybrid polymer for spin-on process. The inorganic part of hard-mask was much easier etching than photo resist layer. Beside, the organic part of hard-mask was much harder etching than substrate layer. We characterized the optical and morphological properties to the hard mask films using organic-inorganic hybrid polymer, and then etch rate of photo resist layer and hard-mask film were compared. The hybrid polymer prepared from organic and inorganic materials was found to be useful hard-mask film to form the nano-patterns.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.430-430
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• 2007

In this study, the nematic liquid crystal (NLC) alignment effects treated on the ZnO thin film layers using ion beam irradiation were successfully studied for the first time. The ZnO thin films were deposited on indium-tin-oxide (ITO) coated glass substrates by rf-sputter and The ZnO thin films were deposited at the three kinds of rf power. The used DuoPIGatron type ion beam system, which can be advantageous in a large area with high density plasma generation. The ion beam parameters were as follows: energy of 1800 eV, exposure time of 1 min and ion beam current of $4\;mA/cm^2$ at exposure angles of $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$. The homogeneous and homeotropic LC aligning capabilities treated on the ZnO thin film surface with ion beam exposure of $45^{\circ}$ for 1 min can be achieved. The low pretilt angle for a NLC treated on the ZnO thin film surface with ion beam irradiation for all incident angles was measured. The good LC alignment treated on the ZnO thin film with ion beam exposure at rf power of 150 W can be measure. For identifying surfaces topography of the ZnO thin films, atomic force microscopy (AFM) was introduced. After ion beam irradiation, test samples were fabricated in an anti-parallel configuration with a cell gap of $60{\mu}m$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.8
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• pp.13-19
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• 2001

We report on the fabrication and characterization of $Al_{0.3}Ga_{0.7}N$ HFETs with different barrier layer thickness which were grown using plasma-assisted molecular beam epitaxy (PAMBE). The barrier thickness of $Al_{0.3}Ga_{0.7}N$/GaN HFETs could be optimized in order to maximize 2 dimensional electron gas induced by piezoelectric effect without the relaxation of $Al_{0.3}Ga_{0.7}N$ layer. $Al_{0.3}Ga_{0.7}N$/GaN (20 nm/2 mm) HFET with 0.6 ${\mu}m$-long and 34 ${\mu}m$-wide gate shows saturated current density ($V_{gs}=1\;V$) of 1.155 A/mm and transconductance of 250 ms/mm, respectively. From high frequency measurement, the fabricated $Al_{0.3}Ga_{0.7}N$/GaN HFETs showed $F_t=13$ GHz and $F_{max}=48$ GHz, respectively. The uniformity of less than 5% could be obtained over the 2 inch wafer. In addition to the optimization of epi-layer structure, the relation between breakdown voltage and high frequency characteristics has been examined.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.3
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• pp.263-270
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• 2017

This study was conducted to investigate the dietary supplementation of fruiting body of Hericium erinaceus (HE) mushroom on lipid profiles of serum and histological changes of the liver in rats with high fat and cholesterol diet. Five-week old female Sprague-Dawley albino rats were divided into three groups of 8 rats each: The normal control diet (NC group), high fat and cholesterol diet (HFC group), and HFC diet supplemented with 5% fruiting powder of Hericium erinaceus (HFC+HE group). In the HFC+HE group, serum total cholesterol, low density lipoprotein, and triglyceride concentrations were significantly reduced compared with the NC group. Body weight gain of those in the HFC+HE group were lower than those in the HFC group; whereas HFC+HE had no effect on the levels of plasma albumin, creatinine, blood urea nitrogen, uric acid, glucose, and total protein. The enzyme activities related to the liver function, such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), and, alkaline phosphatase (ALP), were lower in the NC group than in the HFC group, but without significance. Feeding the mushroom increased the excretion of total lipid and cholesterol. A histopathological analysis showed that the those in the HFC group developed hepatic steatosis, whereas those in the HFC+HE group developed small fat droplet. In conclusion, these results suggest that 5% HE supplementation to HFC diet provided health benefits by acting on lowering atherogenic lipid profile in rats with high fat and cholesterol diet.

• Korean Journal of Clinical Laboratory Science
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• v.53 no.3
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• pp.241-248
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• 2021

The present study was conducted to assess the relationship between aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio and pulse pressure in Korean adults with hypertension. Data from 1,515 adults from the sixth Korean National Health and Nutrition Examination Survey (KNHANES VI-3, 2015) were analyzed. There were several key findings in the present study. First, aspartate aminotransferase (odds ratio [OR], 1.018; 95% confidence interval [CI], 1.002 to 1.033), alanine aminotransferase (OR, 0.982; 95% CI, 0.969 to 0.996), and aspartate aminotransferase/alanine aminotransferase ratio (OR, 1.367; 95% CI, 1.027 to 1.819) were the independent factors determining high pulse pressure. Second, after adjusting for related variables [age, gender, smoking, alcohol consumption, regular exercise, total cholesterol (TC), triglycerides (TGs), high-density lipoprotein-cholesterol (HDL-C), fasting plasma glucose (FPG), body mass index (BMI), and waist circumference (WC)], the ORs of high pulse pressure with the 1st quartile as a reference were significantly higher in the 4th quartile of aspartate aminotransferase/alanine aminotransferase ratio [1.632 (95% CI, 1.113~2.393)]. The high pulse pressure was positively associated with aspartate aminotransferase and alanine aminotransferase/alanine aminotransferase ratio in Korean adults with hypertension, but was inversely associated with alanine aminotransferase.

• The Journal of Korean Medicine
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• v.27 no.3 s.67
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• pp.107-131
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• 2006

Background and Aims: Dansamtongmek-tang (DSTMT) and Dansamsengmek-san (DSSMS) have been used for many years as therapeutic agents for the acute stage of cerebrovascular disease, hypertension and hyperlipidemia in Oriental medicine, but the effects of DSTMT and DSSMS on hyperlipidemia and safety for cell damage are not yet well-known. This study was done to investigate the effects of DSTMT and DSSMS on hyperlipidemia. Methods: In vivo test: after administering DSTMT and DSSMS to SHR and ICR occurred hyperlipidemia for 3 weeks, we analyzed body weight, cholesterol levels. TG, HDL-chol, LDL-chol, LDH in plasma, brain, liver and kidney tissue, and DNA by RT-PCR. In vitro test: after administering DSTMT and DSSMS to human hepatocellular carcinoma in hypoxia, we observed cell cohesion by light microscope, analyzed the inflow of Ca2+ by confocal laser scanning microscope and DNA by RT-PCR. Results: DSTMT significantly decreased the levels of triglyceride and increased the levels of HDL-cholesterol in SHR, and significantly decreased the levels of LDL-cholesterol and body weight and increased the levels of HDL-cholesterol in ICR. DSSMS significantly decreased body weight, total cholesterol levels, LDL-cholesterol, LDH and cardiac risk factor (CRE) in SHR and significantly decreased the levels of total cholesterol, triglyceride, LDL-cholesterol, LDH and CRF in ICR. DSTMT had an effect on protecting cells from damage by inhibiting production of p53 mRNA, and in DSSMS, by inhibiting production of p53 mRNA and p21 mRNA after hypoxia. DSTMT effectively blocked off Ca2+ at low density, but DSSMS effectively blocked off Ca2+ at high density. Both DSTMT and DSSMS had an effect on inhibiting lipid metabolism by blocking off production of apo B mRNA. Conclusions: These results suggest that DSTMT and DSSMS might be usefully applied for treatment of hyperlipidemia and suppression of brain damage.