• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1117-1120
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• 2001

Chemical mechanical planarization(CMP) has emerged as the planarization technique of choice in both front-end and back-end integrated circuit manufacturing. Conventional CMP process utilize a polyurethane polishing pad and liquid chemical slurry containing abrasive particles. There have been serious problems in CMP in terms of repeatability and defects in patterned wafers. Since IBM's official announcement on Copper Dual Damascene(Cu2D) technology, the semiconductor world has been engaged in a Cu2D race. Today, even after~3years of extensive R&D work, the End-of-Line(EOL) yields are still too low to allow the transition of technology to manufacturing. One of the reasons behind this is the myriad of defects associated with Cu technology. Especially, dishing and erosion defects increase the resistance because they decrease the interconnection section area, and ultimately reduce the lifetime of the semiconductor. Methods to reduce dishing & erosion have recently been interface hardness of the pad, optimization of the pattern structure as dummy patterns. Dishing & erosion are initially generated an uneven pressure distribution in the materials. These defects are accelerated by free abrasive and chemical etching. Therefore, it is known that dishing & erosion can be reduced by minimizing the abrasive concentration. Minimizing the abrasive concentration by using Ce$O_2$ is the best solution for reducing dishing & erosion and for removal rate. This paper introduce dishing & erosion generating mechanism and a method for developing a semi-rigid abrasive pad to minimize dishing & erosion during CMP.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.212-220
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• 2002

The finishing process for die and mold manufacturing is very important because it influences the final quality of products. Injection molds need higher quality surface than general purpose dies and molds. Conventional polishing can not make mold surface down to nanometer roughness efficiently because of their loading and glazing. This paper focused on the development of fixed abrasive pad using water swelling mechanism of polymer binder network. Self-conditioning was recognized as the long term polishing stabilization tool without any loading or glazing because water makes fixed abrasives free by swelling of the pad. Consequently, stable nano-polishing process has been applied on the injection mold, from the experimental results with polished surface roughness of Ra 15.1nm on STD-11 die steel.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.4
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• pp.17-24
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• 2003

Chemical mechanical polishing(CMP) has been applied for planarization of topography after patterning process in semiconductor fabrication process. Tungsten CMP is necessary to build up interconnects of semiconductor device. But the tungsten dishing and the oxide erosion defects appear at end-point during tungsten CMP. It has been known that the generation of dishing and erosion is based on the over-polishing time, which is determined by pattern selectivity. Fixed abrasive pad takes advantage of decreasing the defects resulting flam reducing pattern selectivity because of the lower abrasive concentration. The manufacturing technique of fixed abrasive pad using hydrophilic polymers is introduced in this paper. For application to tungsten CMP, chemicals composed of oxidizer, catalyst, and acid were developed. In comparison of the general pad and slurry for tungsten CMP, the fixed abrasive pad and the chemicals resulted in appropriate performance in point of removal rate, uniformity, material selectivity and roughness.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.164-171
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• 2014

A highly sensitive and selective non-enzymatic glucose sensor has gained great attention because of simple signal transformation, low-cost, easily handling, and confirming the blood glucose as the representative technology. Until now, glucose sensor has been developed by the immobilization of glucose oxidase (GOx) on the surface of electrodes. However although GOx is quite stable compared with other enzymes, the enzyme-based biosensors are still impacted by various environment factors such as temperature, pH value, humidity, and toxic chemicals. Non-enzymatic sensor for direct detecting glucose is an attractive alternative device to overcome the above drawbacks of enzymatic sensor. Many efforts have been tried for the development of non-enzymatic sensors using various transition metals (Pt, Au, Cu, Ni, etc.), metal alloys (Pt-Pb, Pt-Au, Ni-Pd, etc.), metal oxides, carbon nanotubes and graphene. In this paper, we show that Ni-based nano-particles (NiNPs) exhibit remarkably catalyzing capability for glucose originating from the redox couple of $Ni(OH)_2/NiOOH$ on the surface of ITO electrode in alkaline medium. But, these non-enzymatic sensors are nonselective toward oxidizable species such as ascorbic acid the physiological fluid. So, the anionic polymer was coated on NiNPs electrode preventing the interferences. The oxidation of glucose was highly catalyzed by NiNPs. The catalytically anodic currents were linearly increased in proportion to the glucose concentration over the 0~6.15 mM range at 650 mV versus Ag/AgCl.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.230.2-230.2
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• 2014

스퍼터링 공정은 보통 수백 eV로 가속된 이온에 의한 고체 타겟으로부터 입자의 방출로서 정의할 수 있다. 스퍼터된 입자는 열에너지보다 운동에너지가 크며 박막성장은 저에너지의 입자충격, 불활성 가스이온, 타겟부터 산란된 입자에 의하여 지배된다. 본 연구는 직경 2인치의 원형 Cr 타겟을 셔터를 닫고 예비 스퍼터링 할 때 셔터(SUS 304 0.1t)가 전자기력을 받아서 기계적으로 진동하는 현상을 규명하고자 하였다. 셔터의 하단부를 챔버의 중심축에 고정시켜서 타겟과 평행하도록 수 cm 떨어뜨려서 위치한 뒤 직류 마그네트론 플라즈마를 발생시켰을 때 DC power에 따라서 각각 움직임을 동영상촬영을 진행하였고, 셔터의 중심을 실로 매달아서 자유롭게 움직일 수 있도록 한 뒤 플라즈마가 발생했을 때 기계적인 움직임을 중점적으로 관찰했다. 움직임의 차이를 비교하기 위해서 셔터의 크기를 줄여가며 일정한 DC power에서 실험을 진행했고, 자세한 관찰을 위해서 초고속카메라(210 fps)로 짧은 순간의 변화를 비교했다. 실험조건은 5, 10 mTorr, DC power 30, 40, 50, 70, 100 W, Ar 30 sccm, 셔터의 크기 10, 20, 30, 40, 50, 60 mm로 실시했다. 압력이 낮아질수록, 셔터의 크기가 작을수록, DC power가 커질수록 움직임변화가 커졌고, 진동수가 빨라지는 것을 확인했다. F=qE=ma를 통해서 실험에서 촬영한 동영상을 근거로 거리측정을 통해 실험에서 얼마의 전기장이 인가되어 있는지 예측하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.146-146
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• 2012

영상 분석을 통하여 하천의 표면유속을 산정하는 표면영상유속계(SIV)는 기존 유속측정 방법들에 비해 간편하고, 효율적이며 짧은 시간에 원하는 영역의 유속장을 산정할 수 있다는 장점을 가지고 있다. 하지만 현장 상황에 따라 분석을 위한 변수들을 달리 적용하고 있기 때문에 사용자마다 유속 결과가 달라질 수 있다는 단점이 있다. 이에 본 연구에서는 표면영상유속계의 측정 불확도 산정을 위해 기지의 유속 분포와 추적자 분포를 가진 인공 영상들을 제작하였다. 이 인공 영상들은 입자영상유속계(PIV)의 불확도 분석에 많이 사용되는 표준 PIV 영상과 유사한 것이다. 이 인공 영상을 이용하여 영상의 취득과 처리에 관련된 여러 변수가 최종 유속장에 미치는 영향을 분석하였다. 연구된 변수에는 상관창의 크기, 탐색창의 크기, 추적 입자의 농도, 면외 속도와 평균 영상 속도, 두 영상간의 시간 간격이 포함된다. 상호상관법을 이용하여 고정확도의 결과를 얻기 위해, 상관창의 크기는 상관창 안에 포함되는 입자의 수가 충분할 만큼 커야 하며, 추적 입자의 농도가 정확도에 크게 영향을 미치는 것을 확인하였다. 또한, 상호상관법을 이용하여 정확도 높은 유속측정 결과를 얻기 위해서는 최적 시간간격 또는 평균 영상 유속이 선택되어야 함을 보였다.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.734-741
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• 1999

Al2O3/t-ZrO2 particulate composites were prepared by sintering at 150$0^{\circ}C$ and 1$600^{\circ}C$ for 2h in air and microstructure and mechanical properties of the composites were investigated. Although most ZrO2 particles existed at Al2O3 grain boundaries a few ZrO2 particles within Al2O3 grains. Al2O3 grain growth was depressed due to the pinning effect by ZrO2 particles. During sintering coarsening of intergranular ZrO2 particles occurred as a results of the elimination of ZrO2 intraagglomerate grain boundaries and the coalescence of dragged ZrO2 particles by migrating Al2O3 grain boundries. Changes in mechanical properties of Al2O3 composites were dependant on microstructure of Al2O3 matrix and on size and structure of dispersed ZrO2.

• The KIPS Transactions:PartA
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• v.13A no.6 s.103
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• pp.501-510
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• 2006

The self-organizing super peer ring P2P search scheme improves search performance of the existing unstructured peer-to-peer systems, in which super peers with high capacity constitute a ring structure and all peer in the system utilize the ring for publishing or querying their keys. In this paper, we further improves the performance of the self-organizing ring by adaptively changing its super peer ratio according to the status of the entire system. By using PSO, the optimized super peer ratio can be maintained within the system. Through simulations, we show that our self-organizing super peer ring optimized by PSO outperforms not only the fixed super peer ring but also the self-organizing super ring with fixed ratio in the aspect of query success rate.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.8
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• pp.450-457
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• 2015

In this research a adsorbent, PVA-Zeolite bead, was prepared by immobilizing zeolite with PVA. The results of XRD and SEM analysis showed that the prepared PVA-Zeolite beads had porous structure and the zeolite particles were in mobilized within the internal matrix of the beads. The adsorption properties of Sr ion and Cs ion with the adsorbent were studied by different parameters such as effect of pH, adsorption rate, and adsorption isotherm. The adsorption of Sr ion and Cs ion reached equilibrium after 540 minutes. The adsorption kinetics of both ions by the PVA-Zeolite beads were fitted well by the pseudo-second-order model more than pseudo-first-order model. The equilibrium data fitted well with Langmuir isotherm model. The maximum adsorption capacities of Sr ion and Cs ion calculated from Langmuir isotherm model were 52.08 mg/g and 58.14 mg/g, respectively. The external mass transfer step was very fast compared to the intra-particle diffusion step in the adsorption process of Cs ion and Sr ion by the PVA-Zeolite beads. This result implied that the rate controlling step was the intra-particle diffusion step.

• Clean Technology
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• v.15 no.3
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• pp.194-201
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• 2009

Reductive reactivity of zero-valent iron nanoparticles was investigated for removal of nitrate-nitrogen which is considered one of the major water pollutants. To elucidate the difference in reactivity between preparation methods, iron nanoparticles were synthesized respectively from microemulsion and aqueous solution of ferric ions. Iron nanoparticles prepared from microemulsion were deposited on aluminum by electrophoretic method, and their reaction kinetics was compared to that of the same nanoparticles suspended in aqueous batch reaction. With an approximation of pseudo-first-order reaction, rate constants for suspended nanoparticles prepared from microemulsion and dilute aqueous solution were $3.49{\times}10^{-2}min^{-1}$ and $1.40{\times}10^{-2}min^{-1}$, respectively. Iron nanoparticles supported on aluminum showed ca. 30% less reaction rate in comparison with the identical nanoparticles in suspended state. However, supported nanoparticles showed the superior effectiveness in terms of nitrate-nitrogen removal per zero-valent iron input especially when excess amounts of nitrates were present. Iron nanoparticles deposited on aluminum maintained reductive reactivity for more than 3 hours, and produced nitrogen gas as a final reduction product of nitrate-nitrogen.