• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.285-285
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• 2011

EUVL (Extreme Ultra Violet Lithography) is one of competitive lithographic technologies for sub-30nm fabrication of nano-scale Si devices that can possibly replace the conventional photolithography used to make today's microcircuits. Among the core EUVL technologies, mask fabrication is of considerable importance since the use of new reflective optics having a completely different configuration compared to those of conventional photolithography. Therefore new materials and new mask fabrication process are required for high performance EUVL mask fabrication. This study investigated the etching properties of SnO2 (Tin Oxide) as a new absorber material for EUVL binary mask. The EUVL mask structure used for etching is SnO2 (absorber layer) / Ru (capping / etch stop layer) / Mo-Si multilayer (reflective layer) / Si (substrate). Since the Ru etch stop layer should not be etched, infinitely high selectivity of SnO2 layer to Ru ESL is required. To obtain infinitely high etch selectivity and very low LER (line edge roughness) values, etch parameters of gas flow ratio, top electrode power, dc self - bias voltage (Vdc), and etch time were varied in inductively coupled Cl2/Ar plasmas. For certain process window, infinitely high etch selectivity of SnO2 to Ru ESL could be obtained by optimizing the process parameters. Etch characteristics were measured by on scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Detailed mechanisms for ultra-high etch selectivity will be discussed.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.568-571
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• 2001

Food wastewater eluted from the three-stage methane fermentation system developed in this lab showed high concentrations of TCOD, BOD, T-N and T-P. Because the effluent of biological filter chamber (BFC) still had high concentration of nitrogen and organic material, the effluent was treated with algal periphyton system using algae. The removal rates of COD, T-N and T-P wer 96, 98 and 91%, respectively, in this system. The grown algae could digested byy waterfleas using the ecological food chain system. Food wastewater is better than algal culture medium for growth of waterflea, Moima Macrocopa. During 12days, the individual of waterflea increased to 180 in the food wastewater containing a T-N concentration of 150 mg/ ${\ell}$.

• BMB Reports
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• v.45 no.5
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• pp.275-280
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• 2012

Nicotinic acetylcholine receptors (nAChRs) are a diverse family of homo- or heteropentameric ligand-gated ion channels. Understanding the physiological role of each nAChR subtype and the key residues responsible for normal and pathological states is important. ${\alpha}$-Conotoxin neuropeptides are highly selective probes capable of discriminating different subtypes of nAChRs. In this study, we performed homology modeling to generate the neuronal ${\alpha}3$, ${\beta}2$ and ${\beta}4$ subunits using the x-ray structure of the ${\alpha}1$ subunit as a template. The structures of the extracellular domains containing ligand binding sites in the ${\alpha}3{\beta}2$ and ${\alpha}3{\beta}4$ nAChR subtypes were constructed using MD simulations and ligand docking processes in their free and ligand-bound states using ${\alpha}$-conotoxin GIC, which exhibited the highest ${\alpha}3{\beta}2$ vs. ${\alpha}3{\beta}4$ discrimination ratio. The results provide a reasonable structural basis for such a discriminatory ability, supporting the idea that the present strategy can be used for future investigations on nAChR-ligand complexes.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.136-136
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• 2003

In fiber optic networks, system size and cost can be significantly reduced by development of optical components through planar optical waveguides. One important step to realize the compact optical devices is to develop planar optical amplifier to compensate the losses in splitter or other components. Planar amplifier provides optical gain in devices less than tens of centimeters long, as opposed to fiber amplifiers with lengths of typically tens of meters. To achieve the same amount of gain between the planar and fiber optical amplifier, much higher Er doping levels responsible for the gain than in the fiber amplifier are required due to the reduced path length. These doping must be done without the loss of homogeniety to minimize Er ion-ion interactions which reduce gain by co-operative upconversion. Sol-gel process has become a feasible method to allow the incorporation of Er ion concentrations higher than conventional glass melting methods. In this work, Er-doped $SiO_2$-A1$_2$ $O_3$ films were prepared by two different method via sol -Eel process. Tetraethylorthosilicate(TEOS)/aluminum secondary butoxide [Al (OC$_4$ $H_{9}$)$_3$], methacryloxypropylcnethoxysaane(MPTS)/aluminum secondary butofde [Al(OC$_4$ $H_{9}$)$_3$] systems were used as starting materials for hosting Er ions. Er-doped $SiO_2$-A1$_2$ $O_3$ films obtahed after heat-treating, coatings on Si substrate were characterized by X-ray din action, FT-IR, and N-IR fluorescence spectroscopy. The luminescence properties for two different processing procedure will be compared and discussed from peak intensity and life time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.388-388
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• 2010

In this study, Ferroelectric vinylidene fluoride-trifluoroethylene (VF2-TrFE) copolymer films were directly deposited on degenerated Si (n+, $0.002\;{\Omega}{\cdot}cm$) using by spin coating method. A 1~5 wt% diluted solution of purified vinylidene fluoride-trifluoroethylene (VF2:TrFE = 70:30) in a dimethylformamide (DMF) solvent were prepared and deposited on silicon wafers at a spin rate of 2000 ~ 4000 rpm for 2 ~ 30 seconds. After annealing in a vacuum ambient at 100 ~ $200^{\circ}C$ for 60 min, upper aluminum electrodes were deposited by vacuum evaporation for electrical measurement. X-ray diffraction results showed that the VF2-TrFE films on Si substrates had $\beta$-phase of copolymer structures. The capacitance on highly doped Si wafer showed hysteresis behavior like a butterfly shape and this result indicates clearly that the copolymer films have ferroelectric properties. The typical measured remnant polarization ($P_r$) and coercive filed ($E_c$) values were about $5.7\;{\mu}C/cm^2$ and 710 kV/em, respectively, in an applied electric field of ${\pm}$ 1.5 MV/em. The gate leakage current densities measured at room temperature was less than $7{\times}10^{-7}\; A/cm^2$ under a field of 1 MV/cm.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.429.2-429.2
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• 2014

ZnO nanowire is known as synthesizable and good mechanical properties. And, stimuli-responsive polymer is widely used in the application of tunable sensing device. So, we combined these characteristics to make precise tunable sensing devise. In this work, we investigate the dependence of ZnO nanowire alignment and morphology on si substrate using nanosphere template with various conditions via hydrothermal process. Also, pH-temperature dependant tuning ability of nanostructure was studied. The brief experimental scheme is as follow. First, Zno seed layer was coated on a si wafer ($20{\times}20mm$) by spin coater. And then $1.15{\mu}m$ sized close-packed PS nanospheres were formed on a cleaned si substrate by using gas-liquid-solid interfacial self-assembly method. After that, zinc oxide nanowires were synthesized using hydrothermal method. Before the wire growth, to specify the growth site, heat treatment was performed. Finally, NIPAM(N-Isopropylacrylamide) was coated onto as-fabricated nanostructure and irradiated by UV light to form the PNIPAM network. The morphology, structures and optical properties are investigated by FE-SEM(Field Emission Scanning electron Microscopy), XRD(X-ray diffraction), OM(Optical microscopy), and WCA(water contact angle).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.05a
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• pp.41-41
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• 2003

텅스텐(W)은 높은 thermal stability 와 process compatibility 및 우수한 corrosion r resistance 둥으로 integrated circuit (IC)의 gate 및 interconnection 둥으로의 활용이 대두되고 있으며, 차세대 thin film transistor liquid crystal display (TFT-LCD)의 gate 및 interconnection m materials 둥으로 사용되고 았다. 그러나, 이러한 장점을 가지고 있는 팅스텐 박막이 실제 공정상에 적용되가 위해서는 건식 식각이 주로 사용되는데, 이는 wet chemical 을 이용한 습식 식각을 사용할 경우 낮은 etch rate, line width 의 감소 및 postetch residue 잔류 동의 문제가 발생하기 때문이다. 또한 W interconnection etching 을 하기 위해서는 높은 텅스텐 박막의 etch rate 과 하부 layer ( (amorphous silicon 또는 poly-SD와의 높은 etch selectivity 가 필수적 이 라 할 수 있다. 그러 나, 지금까지 연구되어온 결과에 따르면 텅스탠과 하부 layer 와의 etch selectivity 는 2 이하로 매우 낮게 관찰되고 았으며, 텅스텐의 etch rate 또한 150nm/min 이하로 낮은 값을 나타내고 있다. 따라서 본 연구에서는 halogen-based inductively coupled plasma 를 이용하여 텅스텐 박막 식각시 여러 가지 첨가 가스에 따른 높은 텅스탠 박막의 etch rate 과 하부 layer 와의 높은 etch s selectivity 를 얻고자 하였으며, 그에 따른 식각 메커니즘에 대하여 알아보고자 하였다. $CF_4/Cl_2$ gas chemistry 에 첨 가 가스로 $N_2$와 Ar을 첨 가할 경 우 텅 스텐 박막과 하부 layer 간의 etch selectivity 증가는 관찰되지 않았으며, 반면에 첨가 가스로 $O_2$를 사용할 경우, $O_2$의 첨가량이 증가함에 따라 etch s selectivity 는 계속적으로 증가렴을 관찰할 수 있었다. 이는 $O_2$ 첨가에 따라 형성되는 WOF4 에 의한 텅스텐의 etch rates 의 감소에 비하여, $Si0_2$ 등의 형성에 의한 poly-Si etch rates 이 더욱 크게 감소하였기 때문으로 사료된다. W 과 poly-Si 의 식각 특성을 이해하기 위하여 X -ray photoelectron spectroscopy (XPS)를 사용하였으며, 식각 전후의 etch depth 를 측정하기 위하여 stylus p pmfilometeT 를 이용하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.477-477
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• 2008

For more than three decades, the gate dielectrics in CMOS devices are $SiO_2$ because of its blocking properties of current in insulated gate FET channels. As the dimensions of feature size have been scaled down (width and the thickness is reduced down to 50 urn and 2 urn or less), gate leakage current is increased and reliability of $SiO_2$ is reduced. Many metal oxides such as $TiO_2$, $Ta_2O_4$, $SrTiO_3$, $Al_2O_3$, $HfO_2$ and $ZrO_2$ have been challenged for memory devices. These materials posses relatively high dielectric constant, but $HfO_2$ and $Al_2O_3$ did not provide sufficient advantages over $SiO_2$ or $Si_3N_4$ because of reaction with Si substrate. Recently, $HfO_2$ have been attracted attention because Hf forms the most stable oxide with the highest heat of formation. In addition, Hf can reduce the native oxide layer by creating $HfO_2$. However, new gate oxide candidates must satisfy a standard CMOS process. In order to fabricate high density memories with small feature size, the plasma etch process should be developed by well understanding and optimizing plasma behaviors. Therefore, it is necessary that the etch behavior of $HfO_2$ and plasma parameters are systematically investigated as functions of process parameters including gas mixing ratio, rf power, pressure and temperature to determine the mechanism of plasma induced damage. However, there is few studies on the the etch mechanism and the surface reactions in $BCl_3$ based plasma to etch $HfO_2$ thin films. In this work, the samples of $HfO_2$ were prepared on Si wafer with using atomic layer deposition. In our previous work, the maximum etch rate of $BCl_3$/Ar were obtained 20% $BCl_3$/ 80% Ar. Over 20% $BCl_3$ addition, the etch rate of $HfO_2$ decreased. The etching rate of $HfO_2$ and selectivity of $HfO_2$ to Si were investigated with using in inductively coupled plasma etching system (ICP) and $BCl_3/Cl_2$/Ar plasma. The change of volume densities of radical and atoms were monitored with using optical emission spectroscopy analysis (OES). The variations of components of etched surfaces for $HfO_2$ was investigated with using x-ray photo electron spectroscopy (XPS). In order to investigate the accumulation of etch by products during etch process, the exposed surface of $HfO_2$ in $BCl_3/Cl_2$/Ar plasma was compared with surface of as-doped $HfO_2$ and all the surfaces of samples were examined with field emission scanning electron microscopy and atomic force microscope (AFM).

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.282-293
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• 2021

This paper examines gamma-ray shielding properties of SBC-Bx glass system with the chemical composition of 40SiO₂-10B₂O₃-xBaO-(45-x)CaO- yZnO- zMgO (where x = 0, 10, 20, 30, and 35 mol% and y = z = 6 mol%). Mass attenuation coefficient (µ/ρ) which is an essential parameter to study gamma-ray shielding properties was obtained in the photon energy range of 0.015-15 MeV using PHITS Monte Carlo code for the proposed glasses. The obtained results were compared with those calculated by WinXCOM program. Both the values of PHITS code and WinXCOM program were observed in very good agreement. The (µ/ρ values were then used to derive mean free path (MFP), electron density (N_eff), effective atomic number (Z_eff), and half value layer (HVL) for all the glasses involved. Additionally, G-P method was employed to estimate exposure buildup factor (EBF) for each glass in the energy range of 0.015-15 MeV up to penetration depths of 40 mfp. The results reveal that gamma-ray shielding effectiveness of the SBC-Bx glasses evolves with increasing BaO content in the glass sample. Such that SBC-B35 glass has superior shielding capacity against gamma-rays among the studied glasses. Gamma-ray shielding properties of SBC-B35 glass were compared with different conventional shielding materials, commercial glasses, and newly developed HMO glasse. Therefore, the investigated glasses have potential uses in gamma shielding applications.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.766-772
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• 1996

Undoped $SnO_x$ thin films were deposited on Si(100) substrate by using reactive ioassisted deposition technique (R-IAD). In order to investigate the effect of initial oxygen content and heat treatment on the oxidation state and crystalline structure of tin oxide films, $SnO_x$ thin films were post-annealed at 400~$600^{\circ}C$ for 1 hr. in a vacuum ~$5 \times 10^{-3}$ -3/ Torr or were directly deposited on the substrate of $400^{\circ}C$ and the relative arrival ration ($Gamma$) of oxygen ion to Sn metal varied from 0.025 to 0.1, i.e., average impinging energy ($E_a$) form 25 to 100 eV/atom. As $E_a$ increased, the composition ratio of $N_ON{sn}$ changed from 1.25 to 1.93 in post-annealing, treatment and 1.21 to 1.87 in in-situ substrate heating. In case of post-annealing, the oxidation from SnO to $SnO_2$ was closely related to initial oxygen contents and post-annealing temperature, and the perfect oxidation of $SnO_2$ in the film was obtained at higher than $E_a$=75 eV/atom and $600^{\circ}C$. The temperature for perfect oxidation of $SnO_2$ was reduced as low as $400^{\circ}C$ through in-situ substrate heating. The variation of the chemical state of $SnO_x$ thin films with changing $E_a$'s and heating method were also observed by Auger electron spectroscopy.