• Journal of the Korean Vacuum Society
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• v.5 no.2
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• pp.169-174
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• 1996

The applications of the high density plasma sources to the etching in semiconductor fabrication process are actively studied because of the more strict requirement from the dry etching process due to shrinking down of the critical dimension. But in the oxide etching with the high density plasma sources, abundant fluorine atoms released from the flurocarbon feed gas make it difficult to get the highly selective $SiO_2/Si$ etching. In this study, to improve the $SiO_2/Si$ etch selectivity through the control of the radical loss channels, we propose the wall heating , one of methods of controlling loss mechanisms. With appearance mass spectroscopy(AMS) and actinometric optical emission spectroscopy(OES), the increase of both radicals impinging on the substrate and existing in bulk plasma, and the decrease of the fluorine atom with wall temperature are observed. As a result, a 40% improvement of the selectivity was achieved for the carbon rich feed gas.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.25-35
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• 2013

The intramolecular magnetic coupling constant (J) values of diradical-based magnet models (S1-S5) were studied using unrestricted density functional theory. The model systems were designed with series of oxoverdazyl radicals (o-Ver(N) and o-Ver(C)) linked through a benzene coupler. They were divided according to either connectivity of the radical (C or N) or geometrical topology (meta- and para-) of benzene coupler. Reasonable relationship was found between spin density distribution and sign of J value. With our results we determined ferromagnetic (positive J value) and antiferromagnetic (negative J value) interactions. J values were also calculated along the twisting movement by the scan of dihedral angles between the radical and the coupler. An overall trend was found as absolute value of J decreased over increasing torsion angles.

• Bulletin of the Korean Chemical Society
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• v.29 no.3
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• pp.539-540
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• 2008

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.816-823
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• 1996

Chlorine containing high density plasmas are widely used to etch various materials in the microelectronic device fabrication. In this study, the characteristics of inductively coupled $Cl_2(O_2/N_2$) plasmas and their effects on the formation of silicon etching have been investigated using a Langmuir probe, quadrupole mass spectrometry(QMS), X-ray photoelectron spectroscopy(XPS), and Scanning Electron Microscopy(SEM). The addition of oxygen for chlorine plasmas reduced ion current densities and chlorine radical densities compared to the nitrogen addition by the recombination of oxygen with chlorine. Also, when silicon is etched in $Cl_2/O_2$ plasmas, etch products recombined with oxygen such as $SiCl_xO_y$ emerged. However, when nitrogen is added to chlorine, etch products recombined with nitrogen or Si-N bondings on the etched silicon surface were not found. All the silicon etch characteristics were dependent on the plasma conditions such as ion density, radical density, etc. As a result sub micron vertical silicon trench etch profiles could be effectively formed using optimized etch conditions for $Cl_2/O_2\; and \;Cl_2/N_2$ gas combinations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.2
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• pp.95-100
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• 1998

A helical inductively coupled plasma asher, which produces low energy and high density plasma, has been built and investigated for photoresist stripping process. Oxygen ion density in the order of $10^{11}/cm^3$ is measured by Langmuir probe, and higher oxygen radical density is observed by Optical Emission Spectrometer. As RF source power is increased, the plasma density and thus photoresist stripping rate are increased. Independent RF bias power to the wafer stage provides a dc bias to the wafer and an ability to add the ion assisted reaction. At 1 KW of the source power, the coupling mechanism of the RF power to the plasma is changed from the inductive mode to the capacitive one at about 1 Torr. This change causes the plasma density and ashing rate decreases abruptly. The critical pressure of the mode change becomes larger with larger RF power.

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.2
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• pp.189-195
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• 2013

This study was designed to analyze the effects of methanol extracts and solvent fractions of the young branch of Prunus persica on scavenging activity of ROS, RNS and inhibiting activity of oxidative modification in human LDL induced by copper ion or free radical generator. The scavenging capacities of the fractions on DPPH radical, superoxide radical, nitric oxide and peroxynitrite were exhibited the highest in ethylacetate fraction, followed by butanol fraction. In the copper-induced LDL oxidative modification system, the highest antioxidant activity was revealed in ethylacetate fraction, and butanol fraction exhibited a similar activity. However, solvent fractions of the young branch of Prunus persica showed a relatively low antioxidant activity in the AAPH-mediated LDL oxidation. In addition, ethylacetate and butanol fractions also inhibited the copper-mediated LDL oxidation in the REM assay, which was comparable to that of the positive controls, including EDTA, ascorbic acid and BHT. Futhermore, a content of total phenolics in these two fractions was higher than that of the other fractions. These results indicated that ethylacetate and butanol fractions of the young branch of Prunus persica were useful for the prevention of the free radical- or metal ion-induced oxidative damages.

• Journal of Environmental Science International
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• v.21 no.7
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• pp.845-853
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• 2012

Diethyl phthalate (DEP) is widely spread in the natural environment as an endocrine disruption chemicals (EDs). Therefore, in this study, ultrasound (US) and ultraviolet (UVC), including various applied power density (10-40 W/L), UV wavelengths (365 nm, 254 nm and 185 nm) and frequencies (283 kHz, 935 kHz) were applied to a DEP contaminated solution. The pseudo-first order degradation rate constants were in the order of $10^{-1}$ to $10^{-4}\;min^{-1}$ depending on the processes. Photolytic and sonophotolytic DEP degradation rate also were high at shortest UV wavelength (VUV) due to the higher energy of photons, higher molar absorption coefficient of DEP and increased hydroxyl radical generation from homolysis of water. Sonolytic DEP degradation rate increased with increase of applied input power and the dominant reaction mechanism of DEP in sonolysis was estimated as hydroxyl radical reaction by the addition of t-BuOH, which is a common hydroxyl radical scavenger. Moreover, synergistic effect of were also observed for sonophotolytic degradation with various UV irradiation.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3738-3742
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• 2013

The reaction mechanism of $SiF_2$ radical with HNCO has been investigated by the B3LYP method of density functional theory(DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/$6-311++G^{**}$ level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)/$6-311++G^{**}$//B3LYP/$6-311++G^{**}$ level. $SiF_2+HNCO{\rightarrow}IM3{\rightarrow}TS5{\rightarrow}IM4{\rightarrow}TS6{\rightarrow}OSiF_2CNH(P3)$ was the main channel with low potential energy, $OSiF_2CNH$ was the main product. The analyses for the combining interaction between $SiF_2$ radical and HNCO with the atom-in-molecules theory (AIM) have been performed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.103-103
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• 2010

Dependence of radical and ion densities on Plasma Parameters is theoretically investigated in $Cl_2$/Ar plasma discharges. Firstly, a set of reliable rate coefficients is obtained by direct calculations with cross section data set and by comparing them with previously reported values. Then, some global discharge simulations are performed for ICP(inductively coupled plasma) discharges and the results are compared with experimental results. Finally, the validated data set is used to analyze the dependence of radical and ion densities, which are usually not easy to be measured, on electron density arid temperature.

• Korean Journal of Pharmacognosy
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• v.40 no.2
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• pp.143-149
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• 2009

Among aging diseases, the most basic problem is a decrease in bone mineral density. Patients with osteoporosis are steadily increasing in the world. This study was investigated to show the relationship between osteoporotic effects and oxidative damage. Water extracts of 15 medicinal plants and ethanol extracts of 14 medicinal plants with known anti-osteoporotic effects, were tested for their radical scavenging activity using DPPH, ABTS, SRSA and FRAP assay. Water extract of Cornus officinalis, Rubus coreanus and ethanol extract of Rubus coreanus, Viscium album var. coloratum, Cimicifuga heracleifolia showed about 15-20 mg/g of total phenolic contents. Water extract of Cornus officinalis, Rubus coreanus and Epimedium koreanum showed high radical scavenging activity. Ethanol extract of Drynaria fortunei, Cornus officinalis, Rubus coreanus, Gentiana scabra and Astragalus membranaceus showed high radical scavenging activity. Water extract of Drynaria fortunei, Cornus officinalis, Nelumbo nucifera, Epimedium koreanum, and Gentiana scabra showed very strong protective effect against oxidative damage to DNA. These results suggest the correlation between anti-osteoporotic effects and antioxidative effects.