• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.24-28
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• 2007

The etching of zinc oxide (ZnO) thin films has been studied using a high density plasma in a $Cl_2/Ar$ gas. The etch characteristics of ZnO thin films were systematically investigated on varying $Cl_2$ concentration, coil rf power, dc-bias voltage, and gas pressure. With increasing $Cl_2$ concentration, the etch rate of ZnO thin film increased, the redeposition around the etched patterns decreased but the sidewall slope of the etched patterns slanted. As the coil rf power and dc-bias voltage increased, the etch rates of ZnO thin films increased and etch profiles of ZnO thin films were improved. With increasing gas pressure, the etch rate of ZnO thin films slightly increased but little change in etch profile was observed. Based on these results, the optimal etching conditions of ZnO thin film were selected. Finally, the etching of ZnO thin films with a high degree of anisotropy of approximately $75^{\circ}{\sim}80^{\circ}$ without the redepositions and residues was successfully achieved at the etching conditions of 20% $Cl_2$ concentration, coil rf power of 1000 W, dc-bias voltage of 400 V, and gas pressure of 5 mTorr.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.255-264
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• 2013

Cobalt aluminate ($CoAl_2O_4$) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, $CoAl_2O_4$ is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, $CoAl_2O_4$ pigments were synthesized by polymerized complex method and solid state reaction. Then $CoAl_2O_4$ pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE $L^*a^*b^*$. The XRD patterns of $CoAl_2O_4$ show single phase spinel structure. The particle size of $CoAl_2O_4$ measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained $CoAl_2O_4$ pigments could be confirmed through CIE $L^*a^*b^*$ measurement.

• Journal of the Korean GEO-environmental Society
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• v.15 no.7
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• pp.5-11
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• 2014

Both ultraviolet (UV) and ultrasound (US) systems are used in degrading of organic contaminants and they can thus be applicable simultaneously as an UV/US hybrid system in attempts further to increase the degradation efficiency. The pseudo-first order degradation rate constants with the UV, US and UV/US hybrid irradiation were 2.60, 10.34, and $14.81{\times}10^{-3}min^{-1}$, respectively. It was observed that the synergistic effect of UV/US hybrid system for degrading the bis (2-ethylhexyl) phthalate (DEHP). The highest rate of DEHP degradation was found during UV/US hybrid irradiation and the synergistic effect factor (SEF) was calculated to be 1.15 based on the pseudo-first order degradation rate constants. Results indicate that synergistic effect of UV/US hybrid system is closely correlated to the enhancement of sonochemical reactivity with the UV-US interaction of increasing the formation rate of OHby providing additional $H_2O_2$ production through the pyrolysis of water molecules during UV/US hybrid irradiation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.174-174
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• 2009

현재 전자부품용으로 사용되는 유리프리트의 경우 PbO계를 주로 사용하고 있다. 최근 환경규제에 따른 PbO 사용이 제한됨에 따라 이를 대체할 Pb-free 유리 조성에 대한 연구가 활발히 진행 중이다. Pb-free계로서는 $Bi_2O_3$계, $B_2O_3$계가 주로 연구되고 있으나 소성 온도가 $500^{\circ}C$이상으로 높고 또한 $Bi_2O_3$ 계는 중금속이기 때문에 문제가 있다. 본 연구에서는 $400^{\circ}C$ 미만 소성이 가능한 SnO-$P_2O_5$계를 기본 조성계로 선택하고 열적, 전기적, 화학적 특성을 개선하기 위해 $R_2O_3$(R=Al, B), RO(R=Mg, Zn, Ca, Ba) 를 첨가하였다. 개선된 조성으로 샘플을 만들고 이를 대상으로 실제 전자부품 생산 공정에 적용 실험을 진행 하였다. 실험에 사용된 전자 부품은 소형 칩 베리스터로 생산 공정에서 코팅용 유리프리트와 파우더를 절연체로서 전면에 코팅하게 된다. 유리프리트를 코팅함으로서 누설 전류를 차단하고 생산 공정시 베리스터 내부를 보호하게 된다. 실험에 사용된 샘플의 열적 특성은 TMA로, 전기적 절연 특성은 고 절연저항 측정기로 측정하였고 내 산성과 내 알칼리성도 측정하였다. 샘플을 이용하여 완성된 칩 베리스터의 성능은 고온, 내습 신뢰성 TEST(고온:$150^{\circ}C$ 12HR, 내습:$85^{\circ}C$-85%12HR)로 실험하여 합부판정 (Leakage current <10uA)을 내려 완성품과 불량품을 가려내었다.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.37.1-37
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• 2000

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.320-320
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• 1999

• Journal of Korean Society of Environmental Engineers
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• v.29 no.7
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• pp.846-851
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• 2007

This study was performed to compare and to examine the degradation efficiencies and degradation mechanism of pentachlorophenol(PCP) by UV, $UV/H_2O_2$, $Fe^{2+}$, $Fe^{2+}/H_2O_2$, and $UV/Fe^{2+}/H_2O_2$ processes. The pseudo-first order rate constant was compared in each process. The addition of $H_2O_2$ increased the rate constant by 13 times compared to the reaction with UV alone. The reaction rate in $Fe^{2+}$ reaction with PCP increased 4 times and 7.25 times by adding 180 mM $H_2O_2$ and 16 mM $H_2O_2$, respectively. Compared to that with $Fe^{2+}/H_2O_2$, the rate constant of the reaction with UV alone reaction increased 3.1 times. These results indicates the enhancement of reaction rate is closely related to the generation of OH radical. The degree of the iron sludge production observed in $Fe^{2+}/H_2O_2$ reaction was significantly reduced by irradiating UV in this process.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.47-51
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• 2013

Chemical mechanical polishing (CMP) has become one of the key processes in wafer level stacking technology for 3D stacked IC. In this study, two-step CMP process was proposed to polish $Cu/SiO_2$ hybrid bonding surface, that is, Cu CMP was followed by $SiO_2$ CMP to minimize Cu dishing. As a result, Cu dishing was reduced down to $100{\sim}200{\AA}$ after $SiO_2$ CMP and surface roughness was also improved. The bonding interface showed no noticeable dishing or interface line, implying high bonding strength.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.208.1-208.1
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• 2015

최근, 차세대 투명 디스플레이 구동소자로서 산화물 반도체를 이용한 Transparent Amorphous Oxide Semiconductor (TAOS) 기술이 큰 주목을 받고 있다. 산화물 반도체는 기존의 a-Si에 비해 우수한 전기적인 특성과 낮은 구동전압 그리고 넓은 밴드 갭으로 인한 투명성의 장점들이 있다. 그리고 낮은 공정 온도에서도 제작이 가능하기 때문에 유리나 플라스틱과 같은 다양한 기판에서도 박막 증착이 가능하다. 하지만 기존의 furnace를 이용한 열처리 방식은 낮은 온도에서 우수한 전기적인 특성을 내기 어려우며, 공정 시간이 길어지는 단점들이 있다. 따라서 본 연구에서는 산화물 반도체중 In-Ga-Zn-O (IGZO)와 In-Sn-O(ITO)를 각각 채널 층과 게이트 전극으로 이용하였다. 또한 마이크로웨이브 열처리 기술을 이용하여 기존의 열처리 방식에 비해 에너지 전달 효율이 높고 짧은 시간동안 저온 공정이 가능하며 우수한 전기적인 특성을 가지는 투명 박막 트랜지스터를 구현 하였다. 본 실험은 glass 기판위에서 진행되었으며, RF sputter를 이용하여 ITO를 150 nm 증착한 후, photo-lithography 공정을 통하여 하부 게이트 전극을 형성하였다. 이후에 RF sputter를 이용하여 SiO2 와 IGZO 를 각각 300, 50 nm 증착하였고, patterning 과정을 통하여 채널 영역을 형성하였다. 또한 소자의 전기적인 특성 향상을 위해 마이크로웨이브 열처리를 1000 Watt로 2 분간 진행 하였고, 비교를 위하여 기존 방식인 furnace 를 이용하여 N2 분위기에서 $400^{\circ}C$로 30분간 진행한 소자도 병행하였다. 그 결과 마이크로웨이브를 통해 열처리한 소자는 공정 온도가 $100^{\circ}C$ 이하로 낮기 때문에 glass 기판에 영향을 주지 않고 기존 furnace 열처리 한 소자보다 전체적으로 전기적인 특성이 우수한 것을 확인 하였다.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.669-678
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• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.