• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.247-251
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• 2004

반도체 소자의 제조에 있어 실리콘 표면에 성장한 자연산화막을 제거하기 위해 일반적으로 습식 세정 기술이 이용되어 왔다. 하지만 소자의 최소 선폭(design rule)이 nano급으로 고집적화 됨에 따라 contact hole 바닥의 자연산화막을 깨끗이 제거하는데 있어서 그 한계를 나타나고 있다. 이에 대한 효과적인 대안 공정으로 가스 건식 세정 기술이 연구되고 있다. 본 논문에서는 한 번에 50매 이상의 웨이퍼를 처리함으로써 생산성 측면에서 월등한 배치식 설비에서 원거리 플라즈마(remote plasma) 장치에서 2.450Hz의 마이크로웨이브(${\mu}$-wave)에 의해 형성시킨 수소라디칼과 $NF_3$ 가스를 이용하여 실리콘에 결함을 주지 않고 자연산화막을 선택적으로 제거하는 공정에 대해 고찰하였다. AFM을 이용한 표면분석, TEM을 이용한 물성분석, 그리고 ToF-SIMS 및 XPS를 이용한 화학 분석을 습식 및 건식 세정을 비교 평가한 결과, 건식 세정 공정이 실리콘 표면에 결함을 주지 않고 자연산화막을 제거 할 수 있음을 확인하였다. 산화막$(SiO_2)$, 질화막$(Si_3N_4)$, 그리고 다결정 실리콘(Poly-Si) 등의 각 막질별 식각 특성을 고찰하였으며, $NH_3$의 캐리어 가스인 $N_2$의 주입량을 조절함으로써 수소라디칼 형성 효율의 개선이 가능하였으며, 이로부터 게이트와 소스/드레인 사이를 절연하기 위해 이용되는 질화막의 식각 선택비를 2배 정도 개선할 수 있었다. nano급 소자에 실장하여 평가한 결과에서 불산(HF)에 의한 습식 세정 방식에 비하여 약 $20{\sim}50%$ 정도의 contact 저항 감소 효과가 있음이 확인되었다.두 소자 모두 $40mA/cm^2$ 에서 이상적인 화이트 발란스와 같은(0.33,0.33)의 색좌표를 보였다.epsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.한 관심이 높아지고 있다. 그러나 고 자장 영상에서의 rf field 에 의한 SAR 증가는 중요한 제한 요소로 부각되고 있다. 나선주사영상은 SAR 문제가 근원적으로 발생하지 않고, EPI에 비하여 하드웨어 요구 조건이 낮아 고 자장에서의 고속영상방법으로 적합하다. 본 논문에서는 고차 shimming 을 통하여 불균일도를 개선하고, single shot 과 interleaving 을 적용한 multi-shot 나선주사영상 기법으로 $100{\times}100$에서 $256{\times}256$의 고해상도 영상을 얻어 고 자장에서 초고속영상기법으로 다양한 적용 가능성을 보였다. 연구에서 연구된 $[^{18}F]F_2$가스는 친핵성 치환반응으로 방사성동위원소를 도입하기 어려운 다양한 방사성의 약품개발에 유용하게 이용될 수 있을 것이다.었으나 움직임 보정 후 영상을 이용하여 비교한 경우, 결합능 변화가 선조체 영역에서 국한되어 나타나며 그 유의성이 움직임 보정 전에 비하여 낮음을 알 수 있었다. 결론: 뇌활성화 과제 수행시에 동반되는 피험자의 머리 움직임에 의하여 도파민 유리가 과대평가되었으며 이는 이 연구에서 제안한 영상정합을 이용한 움직임 보정기법에 의해서 개선되었다. 답이 없는 문제, 문제 만들기, 일반화가 가능한 문제 등으로 보고, 수학적 창의성 중 특히 확산적 사고에 초점을 맞추어 개방형 문제가 확

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.99-104
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• 2007

Porous silicon exhibiting dual optical properties, both $Febry-P{\acute{e}}rot$ fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type silicon wafer (boron-doped, <100> orientation, resistivity ; $1-10{\Omega}cm$). Two different types of porous silicon, fresh porous silicon (Si-H terminated) and oxidized porous silicon (Si-OH terminated)by the thermal oxidation, were prepared. Then the samples were exposed to the vapor of various organics, such as methanol, acetone, hexane, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic vapors for sensing VOC's. These surface-modified samples showed unique respond in both reflectivity and photoluminescence with various organic vapors. While polar molecules exhibit greater quenching photoluminescence, molecules having higher vapor pressure show greater red shift for reflectivity.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.909-914
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• 2007

Fluorine compounds are the essential chemicals for wet processes of semiconductor and LCD production line. Problems of conventional treatments for fluoride wastewater are their high operation costs and low fluoride removal capacity. In this study, cement paste containing various Ca-bearing hydrates such as portlandite, calcium silicate hydrate(CSH), and ettringite was investigated for fluoride removal. The objectives of this study are to assess the feasibility of using cement paste cured mixture of cement and water as an alternative agent for treatment of fluoride wastewater and to investigate fluoride removal capacity of the cement paste. The performance of cement paste was comparable to that of lime in the kinetic test. In column experiment where the effluent fluoride concentrations were below 0.5 mg/L. Then the leached calcium reached the maximum level of 800 mg/L. The nitrate reduced to the level of less than 10 mg/L. Nitrate in the wastewater was exchanged with interlayer sulfate of these cement hydrate LDHs. Phosphate concentration could be reduced to 10 mg/L by forming calcium phosphate. These results indicate that the cement paste generally has advantageous characteristics as an economical and viable substitute for lime to remove fluoride.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.638-644
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• 2017

Pitch based activated carbon fibers for electric double layer capacitor (EDLC) electrodes were treated by oxyfluorination via varying the ratio of fluorine and oxygen gases to improve high power property. As the partial pressure of fluorine increased, the oxyfluorinated activated carbon fibers showed an increase of linear fluorine functional groups. While the oxygen functional groups increased, no changes was observed with respect to the partial gas pressure. The specific surface area and pore volume decreased due to the etching reaction on the activated carbon fiber surface through oxyfluorination, but the mesopore volume increased about 4.5 times. In the case of activated carbon fibers treated with 50% of the fluorine gas partial pressure, the specific capacitance increased to about 29% and 61% at scan rates of 5 and 50 mV/s, respectively. The improvement of the specific capacitance was believed to be due to the introduction of oxygen and fluorine functional groups on the activated carbon fiber surface and the increase of mesopores through oxyfluorination.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.313-313
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• 2014

GaN계 물질 기반의 광 반도체는 조명 및 디스플레이 관련 차세대 광원으로 많은 관심을 받고 있고, 효율 증대를 위한 에피, 소자 구조 및 패키지 등의 많은 연구가 진행되고 있다. 특히, 투명 전극을 이용한 광 추출 효율의 증가에 대한 연구는 전체 외부양자효율을 증가시키는 중요한 기술로 각광을 받고 있다. 이러한 투명전극은 가시광 영역의 빛을 투과하면서도 전기 전도성을 갖는 기능성 박막 전극으로 산화인듐주석이 널리 사용되고 있으나 인듐 가격의 상승과 산화인듐주석 전극 자체의 크랙 특성으로 인하여 많은 문제점이 지적되고 있다. 이러한 문제를 극복하기 위하여 GaN계 발광 다이오드에 있어서 산화인듐주석 투명 전극의 대체 물질들에 대한 많은 연구들이 활발하게 이루어 지고 있다. 특히, 투명전극 층으로 사용되는 산화인듐주석 대체 박막으로 산화아연에 대한 연구가 각광을 받고 있는 실정이다. 또한, 발광 다이오드의 효율 증가를 위해 발광소자에 표면 요철 구조 형성과 나노구조체 형성 등 박막 표면의 구조 변화를 통한 광추출효율 향상에 대한 많은 연구가 진행되고 있다. 본 연구에서는 산화아연 박막을 투명전극으로 사용하였으며 광추출효율 향상을 위해 산화아연 투명전극에 패터닝을 형성하고, 그 위에 산화아연 나노막대를 형성하여 기존에 사용하던 산화아연 투명전극보다 우수한 추출효율 및 전류 퍼짐 향상 구조를 제안하고 이에 따른 LED 소자의 광추출효율 향상을 연구하였다. 금속유기화학증착법을 이용하여 c-면 사파이어 기판에 n-GaN, 5주기의 InGaN/GaN 다중양자우물 구조 및 p-GaN의 간단한 LED구조를 성장한 후, p-GaN층 상부에 원자층 증착법을 이용하여 투명전극인 산화아연 박막을 60 nm 두께로 증착하였다. 산화아연 투명전극만 증착한 LED-A와 이후 0.1% HCl을 이용한 습식식각을 통하여 산화아연 투명전극에 육각형 모양의 패턴을 형성한 LED-B, 그리고 LED-B위에 전기화학증착법을 이용하여 $1.0{\mu}m$의 산화아연 나노 막대를 증착한 LED-C를 제작하였다. LED-A, -B 및 -C에 대한 표면 구조는 SEM이미지를 통하여 확인한 바 산화아연의 육각 패턴과 그 상부에 산화아연의 나노막대가 잘 형성된 것을 확인하였다. I-L 분석으로부터 패턴이 형성되지 않은 산화아연 투명전극으로만 구성된 LED-A에 비하여 산화아연 투명 전극에 육각 패턴을 형성한 LED-B의 전계 발광 세기가 더욱 큰 것을 확인하였다. 또한, 육각 패턴에 산화아연 나노막대를 성장시켜 융합구조를 형성한 LED-C에서는 LED-B와 -A보다 더 큰 전계 발광세기를 확인할 수 있었다. 특히, 인가 전류가 고전류로 갈수록 LED-C의 발광세기가 더욱 강해지는 것으로 효율저하현상 또한 나노융합구조의 LED-C에서 확인할 수 있었다. 이는 기존 산화아연 투명전극에 육각형의 패턴 및 나노막대융합구조를 형성할 경우 전류퍼짐현상을 극대화 할 뿐 아니라, 추가적인 광추출효율 향상 효과에 의해 질화갈륨 기반LED 소자의 광효율이 증가된 것으로 판단된다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.486-493
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• 2003

Schottky type A $l_{0.33}$G $a_{0.67}$N ultraviolet photodetectors were fabricated on the MOCVD grown AlGaN/ $n^{＋}$-GaN and AlGaN/AlGaN interlayer/ $n^{＋}$-GaN structures. The grown layers have the carrier concentrations of -$10^{18}$, and the mobilities were 236 and 269 $\textrm{cm}^2$/V.s, respectively. After mesa etching by ICP etching system, the Si3N4 layer was deposited for passivation between the contacts and Ti/AL/Ni/Au and Pt were deposited for ohmic and Schottky contact, respectively. The fabricated Pt/A $l_{0.33}$G $a_{0.67}$N Schottky diode revealed a leakage current of 1 nA for samples with interlayer and 0.1$\mu\textrm{A}$ for samples without interlayer at a reverse bias of -5 V. In optical measurement, the Pt/A $l_{0.33}$G $a_{0.67}$N diode with interlayer showed a cut-off wavelength of 300 nm, a prominent responsivity of 0.15 A/W at 280 nm and a UV-visible extinction ratio of 1.5x$10^4./TEX>.

• Korean Chemical Engineering Research
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• v.45 no.1
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• pp.32-38
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• 2007

A batch Process has a multi-way data structure that consists of batch-time-variable axis, so the statistical modeling of a batch process is a difficult and challenging issue to the process engineers. In this study, We applied a statistical process control technique to the general batch process data, and implemented a fault-detection and Statistical process control system that was able to detect, identify and diagnose the fault. Semiconductor etch process and semi-batch styrene-butadiene rubber process data are used to case study. Before the modeling, we pre-processed the data using the multi-way unfolding technique to decompose the data structure. Multivariate regression techniques like support vector regression and partial least squares were used to identify the relation between the process variables and process condition. Finally, we constructed the root mean squared error chart and variable contribution chart to diagnose the faults.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.791-799
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• 1996

The purpose of this study was to compare the shear bond strength of adhesion bridge by various resin cements. One hundred and foully 1st premolars were used. The teeth were cut below 2mm from CEJ and the coronal portions were used. The coronal portions were embeded with the acrylic resin and trimmed with sic paper until the flat plane with ${\phi}$ 4mm above acrylic resin sticks in height 5mm were casted with nonprecious metal and the using surfaces were treated with sic paper from #200 to #1200 and polished with alminum oxide paste. And then, the using surfaces were sandblasted and treated with the electrochemical etching. The teeth were divided into three groups of fourty two each. In group I, teeth and specimens were cemented with Panavia 21 In group II, teeth and specimens were cemented with Superbond In group I, teeth and specimens were cemented with All-Bond & composite resin cement Each group was subdivided into three subgroups according to the storage period ; one-day storage, fifteen-day storage, and thirty-day storage. The special jig was made. Then, the specimen and jig were mounted to Instron Universal Testing Machine and the failure were measured. The results were as follows. 1. There was statisfically significant difference between the failure loads of group I and group II and III after one day storage(P<0.01), 2. There was statisfically significant difference between the failure loads of group II and group I and III and between group I and group III at fifteen day storage(P<0.01). 3. There was statisfically significant difference between the failure loads of group I and II and group III after thirty day storage(P<0.01). 4. There was statisfically significant difference between the failure loads of one day storage and fifteen and thirty days storages in group III (P<0.01).

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.588-596
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• 2006

The surface of polystyrene membrane treated by Ar, $O_2$ plasma, and the effects were observed before and after the treatment and permeability of $CO_2$, $N_2$ and selectivity of $CO_2$ relative to $N_2$ was measured using continuous flow gas permeation analyzer (GPA). The mole ratio of O over C in the surface was increased from 0 to 0.179 with Ar plasma treatment and route mean square of surface was increased from $15.86{\AA}$ to $71.64{\AA}$. Therefore the contact angle was decreased from $89.16^{\circ}$ to $18.1^{\circ}$. Thus Plasma treatments made surface of membrane tend to be highly hydrophilic. The optimum condition for the $CO_2$ permeability and ideal selectivity of the plasma treated membrane was as follows: the measurement of Ar (60 W, 2 min, $70^{\circ}C$) plasma treatment was $1.14{\times}10^{-12}[m^3(STP){\cdot}m/m^2{\cdot}sec{\cdot}atm]$ and 4.22. In the case of $O_2$ plasma treatment, the contact angle was decreased at $13.56^{\circ}$ with increase of O/C ratio ($0.189{\AA}$) and route mean square of surface ($57.10{\AA}$). The optimum condition for the $CO_2$ permeability and ideal selectivity of the plasma treated membrane was as follows: the measurement of $O_2$ (90 W, 2 min, $70^{\circ}C$) plasma treatment was $7.1{\times}10^{-12}[m^3(STP){\cdot}m/m^2{\cdot}sec{\cdot}atm]$ and 11.5. After plasma treatment, the changes of membrane surface were all subtly linked with both cross-linking and etching effects. Finally, it was confirmed that the gas permeation capacity and selectivity of the modified membrane with plasma could be improved by an appropriate control of the plasma conditions such as treatment time, the power input and sort of plasma gas.