3,506 research outputs found
Improved morphological stability of CoSi2 layer by in situ growth on polycrystalline silicon using reactive chemical vapor deposition
No full textCoSi2 layers have been grown in situ on undoped polycrystalline silicon by reactive chemical vapor deposition of Co(eta (5)-C5H5)(CO)(2) at 650 degreesC, and their stability has been investigated in the temperature range from 800 to 1000 degreesC. The CoSi2 layers grown by the in situ method had grains with a strong (111) orientation, while no (111) orientation appeared in the CoSi2 layers grown by the conventional two-step method where CoSi formed first and transformed to CoSi (2). The stability of the CoSi (2) layers grown by the in situ process was improved by 100 degreesC over that of the CoSi2 layers grown by the conventional two-step process. The CoSi2 layers grown in situ on a large-grained polycrystalline silicon were stable up to 950 degreesC. The effect of stability improvement by the in situ growth was more pronounced when the grains of the polycrystalline silicon had a small size. The improved stability of the CoSi2 layers grown in situ may be mainly due to the formation of a uniform CoSi2 layer with the grains of (111) orientation. (C) 2001 The Electrochemical Society.The Korea Science and Engineering Foundation ~KOSEF! financially supported this work.
Korea Institute of Science and Technology assisted in meeting the publication
costs of this artice
Effect of heavy arsenic doping on the in-situ growth of epitaxial COSi2 on (100) si using reactive chemical vapor deposition
No full textA COSi2 layer was grown in-situ on heavily arsenic-doped Si by reactive chemical vapor deposition of a Co(eta(5)-C5H5)(CO)(2) precursor at 650 degrees C. The nucleation and growth mechanism were investigated in comparison with those on undoped Si. In the initial deposition stage, discrete COSi2 plates with a large area of the {111} coherent planes were nucleated with a deeper penetration depth and a higher density of twinned structure compared to the plates on undoped Si. A thicker CoSi2 layer is necessary for an epitaxial layer with uniform thickness on the heavily arsenic-doped Si. Analyses of the X-ray rocking curve and residual stress indicated that the high As concentration in COSi2 reduced the lattice mismatch between Si and CoSi2 and reduced the lattice strain.This work was financially supported by the Korea Research Foundation through the Center for Nano Interface Research(KRF-2005-005-J09702)
Cobalt metallorganic chemical vapor deposition and formation of epitaxial CoSi2 layer on Si(100) substrate
No full textAn epitaxial CoSi2 layer was grown on Si(100) substrate by the diffusion of Co from a cobalt-carbon film without the use of an interlayer, which is usually required between the Si and cobalt layers for the formation of epitaxial CoSi2 layers. Co-C and pure Co layers were deposited by metallorganic chemical vapor deposition using the Co precursor cyclopentadienyl dicarbonyl cobalt, Co(eta(5)-C5H5)(CO)(2), and cobalt carbonyl, Co-2(CO)(8), at 350 and 200 degrees C, respectively. The CoSi2 layer was epitaxially grown on Si(100) substrate from Co-C by ex situ rapid thermal annealing at 800 degrees C in N-2 ambient. However, the polycrystalline CoSi2 layer was formed from pure Co film under the same annealing conditions. The supply of Co to the interface by diffusion in the Co-C film seems to be lower enough than in the pure Co film, resulting in an epitaxial CoSi2 layer on Si(100) substrate. (C) 1999 The Electrochemical Society. All rights reserved.The Korea Advanced Institute of Science and Technology assisted in meeting the publication costs of this article
In situ growth of an epitaxial CoSi2 layer on a Si(100) substrate by reactive chemical-vapor deposition using a cobalt metallorganic source
No full textUniform epitaxial CoSi2 layers have been grown in situ on a (100) Si substrate at temperatures above 600 degrees C by reactive chemical-vapor deposition of cyclopentadienyl dicarbonyl cobalt, Co(eta(5)-C5H5)(CO)(2). Co-rich phases such as Co2Si and CoSi were suppressed during cobalt metallorganic chemical-vapor deposition at substrate temperatures above 500 degrees C. A thin carbon layer was found on the top of the epitaxial CoSi2 layer grown on the Si substrate due to incomplete decomposition of the cobalt metallorganic source and diffusion of Co into the Si substrate. In spite of the existence of a surface carbon layer, an ion channeling minimum yield, chi(min), of 8% in Rutherford backscattering/channeling spectrometry has been achieved in the epitaxial layer, indicating a nearly perfect epitaxial order. The carbon pileup on the surface of the CoSi2 layer at the initial stage of Co deposition seems to play the role of a cobalt diffusion barrier, avoiding the formation of Co-rich phases. (C) 1999 American Institute of Physics. [S0003-6951(99)02021-5].The authors thank Dr. Dong Kyun Sohn in the R&D division of LG Semicon Co. Ltd. for useful discussions on RBS and TEM analysis
망막전막이 있는 녹내장환자에서 내경계막제거술 후 시야 변화
No full textPURPOSE: To report visual field changes after internal limiting membrane (ILM) peeling for macular epiretinal membrane (ERM) according to the severity of glaucoma.
METHODS: A retrospective review of 37 eyes from 37 patients who underwent ILM peeling to treat ERM. Standard automated perimetry (Humphrey visual field 24-2 program) was performed preoperatively and postoperatively. Based on the Advanced Glaucoma Intervention Study (AGIS) scoring system of preoperative visual field, patients were classified into the early glaucoma (AGIS = 2) group. Postoperative visual field sensitivity at each point was compared with the preoperative value.
RESULTS: Out of 37 eyes, 15 eyes had early glaucoma and 22 had advanced glaucoma. Eyes from both groups had poor postoperative visual field parameters. For eyes with advanced glaucoma, the visual field index was significantly reduced and the visual field damage was larger and wider compared to those with early glaucoma. In both groups, visual field impairment was greater on the nasal side than on the temporal side, and visual acuity was not significantly different. Postoperatively, the macular ganglion cell-inner plexiform layer thickness was decreased, especially on the temporal side of advanced glaucoma.
CONCLUSIONS: Visual field impairment was greater and wider in eyes with advanced glaucoma than in those with early glaucoma after ILM peeling in patients with ERM.목적: 망막전막이 있는 녹내장환자에서 내경계막제거술 후 녹내장 시야 손상 정도에 따라 시야 변화의 차이가 있는지 알아 보고자한다.
대상과 방법: 아주대학교병원 안과에서 특발망막전막으로 진단받고 내경계막제거술을 시행받은 녹내장환자들을 대상으로 수술 전과 후에 시야검사와 빛간섭단층촬영검사를 후향적으로 조사하였다. 수술 전 시행한 시야검사에서 Advanced Glaucoma Intervention Study (AGIS) scoring system을 통해 녹내장 정도를 판단하였으며, AGIS score가 1점 이하인 경우 초기 녹내장으로, AGIS score가 2점 이상인 경우 진행된 녹내장으로 분류하여 시야검사 지표를 비교 분석하였다.
결과: 총 37안(37명) 중 초기 녹내장은 15안, 진행된 녹내장은 22안이었다. 초기 녹내장과 진행된 녹내장 모두에서 내경계막제거술 후 시야검사 지표가 악화되었다. 진행된 녹내장에서 초기 녹내장에 비해 visual field index 감소가 의미 있게 더 크고, 시야 손상 범위가 더 넓게 나타났다. 두 군 모두 수술 후 비측 시야 손상이 더 두드러지게 나타났으며, 황반부 신경절세포-내망상층과 망막신경 섬유층 두께는 감소하였다. 특히 진행된 녹내장의 이측에서 의미 있는 황반부 신경절세포-내망상층 두께 감소를 보였다. 시력은 수술 전후 의미 있는 변화를 보이지 않았다.
결론: 망막전막이 있는 녹내장환자에서 내경계막제거술 후 초기 녹내장에 비해 진행된 녹내장에서 시야 손상의 진행이 더 깊고 넓게 나타났다
On identifying and estimating the cycle time of product development process
No full textA timely introduction of a new product has become invaluable to the firm since the competitors are capable of introducing new or similar products once the driving technology becomes available. In order to generate a high profit from a new product, managers in other departments, such as marketing and production, have to plan ahead of time so that a seamless series of operations can be executed from product development to mass production. Needless to say, a competitive edge is given to the firm with better knowledge on product development process. Such knowledge, nonetheless, is not easy to acquire since a typical product development process is a complex network of many relationships among activities, which we call patterns. In addition to its complex topology, the product development process is often uncertain, iterative, and evolving over time; therefore, even studying individual islands of relationships (patterns) is challenging. Although there were some existing models that shed lights on some of these patterns, very little has been done to systematically analyze the product development process as a whole. In this paper, we develop analytical models that capture essential properties, including uncertainty, iteration and evolution, and estimate the cycle time of each pattern. With our proposed models, the cycle time of a set of patterns (or the whole product development process) can be effectively estimated. As demonstrated in a case study, our model provides valuable insights on how product development process progresses over time, while, the corresponding time estimate can help managers to set appropriate manufacturing and marketing strategies
Hydrogen plasma pretreatment effect on the deposition of aluminum thin films from metalorganic chemical vapor deposition using dimethylethylamine alane
No full textTo study the effect of pretreatment of substrates on the deposition behavior of Al thin films, the surfaces of TiN and SiO2 substrates were exposed to hydrogen plasma or Ar plasma before Al deposition. The Al films were deposited by the pyrolysis of dimethylethylamine alane (DMEAA). A uniform Al film was deposited by the hydrogen plasma exposure to a SiO2 substrate, while island grains were grown by the Ar plasma exposure. The pretreatments of a TiN substrate did not affect the deposition rate of the Al film. The concentration of OH radicals at the SiO2 surface was increased by the hydrogen plasma treatment. We suggest a model in which OH radicals enhance the adsorption of DMEAA on a SiO2 surface, resulting in a larger number of nucleation sites. (C) 1999 American Vacuum Society. [S0734-2101(99)04003-8]
Growth behavior and thermal stability of epitaxial CoSi2 layer from cobalt-carbon films on (100) Si substrate
No full textA uniform epitaxial CoSi2 layer was grown on (100) Si substrate by rapid thermal annealing at 800 degrees C in N-2 ambient without capping layers from an amorphous cobalt-carbon film. The amorphous cobalt-carbon film was deposited on Si substrate by the pyrolysis of cyclopentadienyl dicarbonyl cobalt, Co(eta(5)-C5H5)(CO)(2), at 350 degrees C. The discrete epitaxial CoSi2 layers with {111} and (100) faceted interfaces were formed on (100) Si substrate at the initial stage of reaction between Co and Si. Annealing at elevated temperatures lowered the roughness of the CoSi2/Si interface. The leakage current measured on the junction, fabricated with the epitaxial CoSi2 layer and annealed at 1000 degrees C for 30 s, was as low as that of the as-fabricated junction without silicide. The result indicates that epitaxial (100) CoSi2 is thermally stable at temperatures even above 1000 degrees C and has potential application to the salicide process in subhalf micron devices. (C) 1999 American Institute of Physics. [S0021-8979(99)05618-2]
Field emission characteristics of CoSi2/TiN-coated silicon emitter tips
No full textA CoSi2/TiN bilayer was coated on Si emitter tips and the emission characteristics of the tips were investigated. The CoSi2 layer was grown in situ by a reactive chemical vapor deposition of cyclopentadienyl dicarbonyl cobalt at 650 degreesC and then the TiN was deposited on the CoSi2 layer at 550 degreesC by a reactive sputtering of Ti with gas a reactive gas. The CoSi2 layer was conformally coated on the Si tips and the TiN layer adhered well to the CoSi2 layer. The CoSi2/MN-coated emitters showed a low turn-on voltage due to the low work function by TiN and a steep current increase caused by CoSi2. The current fluctuation of the CoSi2/TiN-coated Si emitter was smaller than that of the TiN-coated emitter. The long-term emission stability of the CoSi2/TiN-coated Si emitter was also greatly improved compared to the CoSi2-coated emitter because of the superior high temperature stability of the TiN layer. (C) 2002 Elsevier Science B.V. All rights reserved
Growth of in situ CoSi2 layer by metalorganic chemical vapor deposition on Si tips and its field-emission properties
No full textWe prepared Si emitters coated with a metalorganic chemical vapor deposited CoSi2 layer to improve emission properties. The CoSi2 layer was grown in situ by reactive chemical vapor deposition of cyclopentadienyl dicarbonyl cobalt at 650 degreesC. The CoSi2 layer was conformally deposited on the Si emitter tips and had a twinned structure at the epitaxial CoSi2/Si interface in the partial region. The CoSi2-coated Si emitters showed an enhanced emission due to the increase in the number of emitting sites from the Fowler-Nordheim plot. The fluctuation of emission current was reduced by the CoSi2 coating. But the long-term stability was not much improved, which may be due to the decrease of the field enhancement factor and the number of emitting sites of the CoSi2-coated Si tip. (C) 2001 American Vacuum Society
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