• Journal of the Korean institute of surface engineering
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• v.40 no.3
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• pp.117-124
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• 2007

The ITO films were deposited on glass substrates by RF-superimposed dc reactive magnetron sputtering and were annealed in $N_2$ vacuum furnace with temperatures in the range of $403K{\sim}573K$ for 30 minutes. Electrical, optical and structural properties of ITO films were examined with varying annealing temperatures from 403 K to 573 K. The resistivity of as-deposited ITO films was $5.4{\times}10^{-4}{\Omega}cm$ at the sputter conditions of applied RF/DC power of 200/200 W, $O_{2}$ flow of 0.2 seem and Ar flow of 0.2 seem. As a result of annealing in the temperature range of $403K{\sim}573K$, the crystallization occurred at 423 K that is lower than the crystallization temperature caused by a conventional sputtering method. And the resistivity decreased from $5.4{\times}10^{-4}{\Omega}cm\;to\;2.3{\times}10^{-4}{\Omega}cm$, the carrier concentration and mobility of ITO films increased from $4.9{\times}10^{20}/cm^3\;to\;6.4{\times}10^{20}/cm^3$, from $20.4cm^2/Vsec\;to\;41.0cm^2/Vsec$, respectively. The transmittance of ITO films in visible became higher than 90% when annealed in the temperature range of $423K{\sim}573K$. High quality ITO thin films made by RF-superimposed dc reactive magnetron sputtering and annealing in $N_2$ vacuum furnace will be applied to transparent conductive oxides of the advanced flat panel display.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.175-180
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• 2015

A facile soft chemical synthesis route is used to grow nano-buds of copper hydroxide [$Cu(OH)_2$] thin films on stainless steel substrate[SS]. Besides different chemical methods for synthesis of $Cu(OH)_2$ nanostructure, the chemical bath deposition (CBD) is attractive for its simplicity and environment friendly condition. The structural, morphological, and electro-chemical properties of $Cu(OH)_2$ thin films are studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurement techniques. The results showed that, facile chemical synthesis route allows to form the polycrystalline, granular nano-buds of $Cu(OH)_2$ thin films. The electrochemical properties of $Cu(OH)_2$ thin films are studied in an aqueous 1 M KOH electrolyte using cyclic voltammetry. The sample exhibited supercapacitive behavior with $340Fg^{-1}$ specific capacitance. Moreover, electrochemical capacitive measurements of $Cu(OH)_2/SS$ electrode exhibit a high specific energy and power density about ${\sim}83Wh\;kg^{-1}$ and ${\sim}3.1kW\;kg^{-1}$, respectively, at $1mA\;cm^{-2}$ current density. The superior electrochemical properties of copper hydroxide ($Cu(OH)_2/SS$) electrode with nano-buds like structure mutually improves pseudocapacitive performance. This work evokes scalable chemical synthesis with the enhanced supercapacitive performance of $Cu(OH)_2/SS$ electrode in energy storage devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.241.2-241.2
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• 2013

최근, 비정질 산화물 반도체 thin film transistor (TFT)는 수소화된 비정질 실리콘 TFT와 비교하여 높은 이동도와 큰 on/off 전류비, 낮은 구동 전압을 가짐으로써 빠른 속도가 요구되는 차세대 투명 디스플레이의 TFT로 많은 연구가 진행되고 있다. 한편, 기존의 MOSFET 제작 시 우수한 박막을 얻기 위해서는 $500^{\circ}C$ 이상의 높은 열처리 온도가 필수적이며 이는 유리 기판과 플라스틱 기판에 적용하는 것이 적합하지 않고 높은 온도에서 수 시간 동안 열처리를 수행해야 하므로 공정 시간 및 비용이 증가하게 된다는 단점이 있다. 따라서, 본 연구에서는 RF sputter를 이용하여 증착된 비정질 InGaZnO pesudo MOSFET 소자를 제작하였으며, thermal 열처리와 microwave 열처리 방식에 따른 전기적 특성을 비교 및 분석하고 각 열처리 방식의 열처리 온도 및 조건을 최적화하였다. P-type bulk silicon 위에 산화막이 100 nm 형성된 기판에 RF 스퍼터링을 이용하여 InGaZnO 분말을 각각 1:1:2mol% 조성비로 혼합하여 소결한 타겟을 사용하여 70 nm 두께의 InGaZnO를 증착하였다. 연속해서 Photolithography 공정과 BOE(30:1) 습식 식각 과정을 이용해 활성화 영역을 형성하여 소자를 제작하였다. 제작 된 소자는 pseudo MOSFET 구조이며, 프로브 탐침을 증착 된 채널층 표면에 직접 접촉시켜 소스와 드레인 역할을 대체하여 동작시킬 수 있어 전기적 특성을 간단하고 간략화된 공정과정으로 분석할 수 있는 장점이 있다. 열처리 조건으로는 thermal 열처리의 경우, furnace를 이용하여 각각 $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$에서 30분 동안 N2 가스 분위기에서 열처리를 실시하였고, microwave 열처리는 microwave를 이용하여 각각 400 W, 600 W, 800 W, 1000 W로 20분 동안 실시하였다. 그 결과, furnace를 이용하여 열처리한 소자와 비교하여 microwave 를 통해 열처리한 소자에서 subthreshold swing (SS), threshold voltage (Vth), mobility 등이 개선되는 것을 확인하였다. 따라서, microwave 열처리 공정은 향후 저온 공정을 요구하는 MOSFET 제작 시의 훌륭한 대안으로 사용 될 것으로 기대된다.

• 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.

• 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.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.5-8
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• 2007

We have investigated the superconducting properties and surface morphology of $Sm_xBa_yCu_3O_{6+z}$ thin films deposited on LMO/IBAD-MgO/Hastelloy which prepared with different composition ratio by co-evaporation method(EDDC, Evaporation using Drum in Dual Chambers). We observed the composition ratio of SmBCO thin films by EDS analysis. We fabricated SmBCO thin film with critical current density of $1.5{\times}10^6A/cm^2$ at composition ratio of SM:Ba:Cu=1.10:2.01:3(at 77 K self-field). And, we confirmed that substitution of Sm-Ba did not occur at Cu rich phase by EDS analysis.

• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.215-221
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• 2005

Thermoelectric bismuth telluride thin films were prepared on $SiO_{2}$/Si substrate with co-sputtering of bismuth and tellurium targets. The effects of deposition temperature on surface morphology, crystallinity and electrical transport properties were investigated. Hexagonal crystallites were clearly visible at the surface of films deposited above $290 ^{\circ}C$. Change of dominant phase from rhombohedral $Bi_2Te_3$ to hexagonal BiTe was confirmed with X-ray diffraction analysis. The deviation from stoichiometric composition at high deposition temperature resulted in the change of structural and electrical characteristics. Seebeck coefficients of all samples have negative value, indicating the prepared $Bi_XTe_Y$ films are n-type thermoelectric. Optimum of Seebeck coefficient and power factor were obtained at the deposition temperature of $225 \^{circ}$C (about -55 $\mu$V/K and $3\times10^{-4}$ W/$k^{2}$m, respectively). Deterioration of thermoelectric properties at higher temperature.

• Journal of the Korean Magnetics Society
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• v.5 no.1
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• pp.42-47
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• 1995

FeN thin films for inductive recording heads were sputter deposited using RF diode sputtering mehtod from a pure iron target onto 7059 glass substrates, and their magnetic properties were measured. The magnetic properties were greatly affected by film thickness, gas pressure, sputter power and flow ratio of $N_{2}$ to Ar. Single layer FeN films with their thickness varied from $1,000\;{\AA}$ to $6,000\;{\AA}$ were doposited. 800 W sputter power, 3 mT gas pressure, $N_{2}$ to Ar flow ratio of 6.6 : 100 were the sputtering conditions. Up to 7 layers of FeN films having total thickness of $6,000\;{\AA}$ were deposited using $SiO_{2}$ of $30\;{\AA}$ thickness as intermediate layers and their coercivity and saturation magnetization were measured. The sputtering conditions were the same as those in the single layer films. Easy axis coercivity of the single layer FeN films gradually decreased as their thickness was increased, but for the films with their thicknesses above $3,000\;{\AA}$, the coercivity changed very little. As the number of the FeN layers were increased, the coercivity decreased We estimated the grain size of FeN films from the FWHM (Full Width at Half Maximum) of X-ray diffraction peaks. The grain size steadily decreased from about $200\;{\AA}$ to $120\;{\AA}$ as the number of layers were increased. Minimum hard axis coercivity of 0.4 Oe was obtained when the number of layers was four. Maximum relative permeability was 2,900 when the number of layers was three. The cut off frequeocy of the multilayer films were above 100 MHz.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.4
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• pp.127-134
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• 2015

Aluminum nitride (AlN) single crystals have attracted much attention for a next-generation semiconductor application because of wide bandgap (6.2 eV), high thermal conductivity ($285W/m{\cdot}K$), high electrical resistivity (${\geq}10^{14}{\Omega}{\cdot}cm$), and high mechanical strength. The bulk AlN single crystals or thin film templates have been mainly grown by PVT (sublimation) method, flux method, solution growth method, and hydride vapor phase epitaxy (HVPE) method. Since AlN suffers difficulty in commercialization due to the defects that occur during single crystal growth, crystalline quality improvement via defects analyses is necessary. Etch pit density (EPD) analysis showed that the growth misorientations and the defects in the AlN surface exist. Transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD) analyses were employed to investigate the overall crystalline quality and various kinds of defects. TEM studies show that the morphology of the AlN is clearly influenced by stacking fault, dislocation, second phase, etc. In addition EBSD analysis also showed that the zinc blende polymorph of AlN exists as a growth defects resulting in dislocation initiator.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.574-577
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• 2011

In this study, we use the $2.5cm{\times}7.5cm$ soda lime glass as the substrate. We used the ultrasonicator. Glass was dipped in the acetone, methanol and DI water respectively for 10 minutes. Ar(99.99%)gas was used as the sputtering gas. We varied the RF power between 100~175 W with 25 W steps. Base pressure was kept by turbo molecular pump at $3.0{\times}10^{-6}$ torr. Working pressure was kept by injection of Ar gas. ZnS thin films were deposited with the radio frequency magnetron sputtering technique at various temperatures and sputtering powers. It is also clearly observed that, the intensity of the (111) XRD peak increases with increasing the RF power. Electrical properties were measured by hall effect methods at room temperature. The resistivity, carrier concentration, and hall mobility of ZnS deposited on glass substrate as a function of sputtering power. It can be seen that as the sputtering power increase from 100 to 175 W, the resistivity of the films on glass decreased significantly from $8.1{\times}10^{-2}$ to $1.2{\times}10^{-3}\;{\Omega}{\cdot}cm$. This behavior could be explained by the effect of the sputtering power on the mobility and carrier concentration. When the RF power increases, the carrier concentration increases slightly while the resistivity decreases significantly. These variation originate from improved crystallinity and enhanced substitutional doping as the sputtering power increases.