• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.78-78
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• 2017

Pure Titanium and alloy have been widely used in dental implants and orthopedics due to their excellent mechanical properties, biocompatibility and corrosion resistance. However, due to the biologically inactive nature of Ti metal implants, it cannot bind to the living bone immediately after transplantation into the body. In order to improve the bone bonding ability of titanium implants, many attempts have been made to alter the structure, composition and chemical properties of titanium surfaces, including the deposition of bioactive coatings. The PEO method has the advantages of short experiment time and low cost. These advantages have attracted attention recently. Recently, many metal ions such as silicon, magnesium, zinc, strontium, and manganese have received attention in this field due to their impact on bone regeneration. Silicon (Si) in particular has been found to be essential for normal bone and cartilage growth and development. Zinc (Zn) plays very important roles in bone formation and immune system regulation and promotes bone metabolism and growth. Manganese (Mn) is an essential trace metal found in all tissues and is required for normal amino acid, lipid, protein and carbohydrate metabolism. The objective of this work was research on the corrosion behavior of Si, Zn and Mn-doped hydroxyapatite on the PEO-treated surface. Anodized alloys was prepared at 270V~300V voltage in the solution containig Zn, Si, and Mn ions. Ion release test was carried out using potentidynamic and AC impedance method in 0.9% NaCl solution. The surface characteristics of PEO treated Ti-6Al-4V alloy were investigated using XRD, FE-SEM, AFM and EDS.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.282-287
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• 1998

Dependence of magnetoresistance on base pressure and deposition rates of each Fe, Co, Cu layers in the $Fe(50{\AA}/[Co(17{\AA})/Cu(24{\AA})]_20$ multilayer thin films, prepared by dc magnetron sputtering on Corning glass, were investigated. AFM analysis, X-ray diffraction analysis, vibrating sample magnetometer analysis, and magnetoresustance measurement (4-probe method) were performed. The multilayer films deposited under low base pressure increases magnetoresistance ratio by preventing oxidation. Annealing for the samples at a moderate temperature allowed larger textured grain with no loss in the periodicity. Magnetoresistance ratio of the annealed multilayers was increased due to the increase antiferromagnetically coupled fraction of the film after annealing. Optimization of deposition rate was greater than 1 $\AA$/s for Fe, and 2.8 $\AA$/s for Cu. Deposition rate of Co showed a tendency of increasing of magnetoresistance ratio due to the formation of flat magnetic layer in case of high deposition rate of Co.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.45-48
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• 2003

The polishing mechanism of W-CMP process has been reported as the repeated process of passive layer formation by oxidizer and abrasion action by slurry abrasives. Thus, it is important to understand the effect of oxidizer on tungsten passivation layer in order to obtain higher removal rate (RR) and very low non-uniformity (NU%) during W-CMP process. In this paper, we investigated the effects of oxidizer on W-CMP process with three different kinds of oxidizers, such as $H_2O_2$, $Fe(NO_3)_3$, and $KIO_3$. In order to compare the removal rate and non-uniformity of three oxidizers, we used alumina-based slurry of pH 4. According to the CMP tests, three oxidizers showed different removal mechanism on tungsten surface. Also, the microstructures of surface layer by AFM image were greatly influenced by the slurry chemical, composition of oxidizers. The difference in removal rate and roughness of tungsten surface are believed to caused by modification in the mechanical behavior of $Al_2O_3$ abrasive particles in CMP slurry. Our stabilized slurries can be used a guideline and promising method for improved W-CMP process.

• Journal of Sensor Science and Technology
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• v.18 no.3
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• pp.239-244
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• 2009

We fabricated nano-templates by low temperature BCP(block copolymer) process at 180 $^{\circ}C$, then we deposited 10 nm-thick $TiO_2$ layers with ALD(atomic layer deposition) at low temperature of 150 $^{\circ}C$. Through FE-SEM analysis, we confirmed the successful formation of the groove-type(width of crest : 30 nm, width of trough : 18 nm) and the cylinder-type(diameter : 10 nm, distance between hole : 25 nm) templates. Moreover, after $TiO_2$-ALD processing, we confirmed the deposition of the uniform nano layers of $TiO_2$ on the nano-templates. Through AFM analysis, the pitches of the crest-through(in groove-type) and hole-hole(in cylinder-type) were the same before and after $TiO_2$-ALD processing. In addition, we indirectly determined the existence of the uniform $TiO_2$ layers on nano-templates as the surface roughness decreased drastically. We successfully fabricated nano-template at low temperature and confirmed that the three-dimensional nano-structure for sensor application could be achieved by $TiO_2$-ALD processing at extremely low temperature of 150 $^{\circ}C$.

• Applied Science and Convergence Technology
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• v.25 no.3
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• pp.56-60
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• 2016

The ALD process is an adequate technique to meet the requirements that come with the downscaling of semiconductor devices. To obtain thin films of the desired standard, it is essential to understand the thermal decomposition properties of the precursors. As such, this study examined the thermal decomposition properties of TEMAHf precursors and its effect on the formation of $HfO_2$ thin films. FT-IR experiments were performed before deposition in order to analyze the thermal decomposition properties of the precursors. The measurements were taken in the range of $135^{\circ}C-350^{\circ}C$. At temperatures higher than $300^{\circ}C$, there was a rapid decrease in the absorption peaks arising from vibration of $Sp^3$ C-H stretching. This showed that the precursors experienced rapid decomposition at around $275^{\circ}C-300^{\circ}C$. $HfO_2$ thin films were successfully deposited by Atomic Layer Deposition (ALD) at $50^{\circ}C$ intervals between $150^{\circ}C$ to $400^{\circ}C$; the deposited films were characterized using a reflectometer, X-ray photoelectron spectroscopy (XPS), Grazing Incidence X-ray Diffraction (GIXRD), and atomic force microscopy (AFM). The results illustrate the relationship between the thermal decomposition temperature of TEMAHf and properties of thin films.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.528-532
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• 2002

Anodic $TiO_2$film on Ti substrate was fabricated at 180V in sulfuric acid solutions containing phosphoric acid and hydrogen peroxide. Effects of the anodizing conditions on the morphology of the oxide layers, and chemical states of the component elements of the layers were studied primarily using SEM, XRD, AFM, and XPS. The pores in the oxide layer was not uniform in size, shape, and growth direction particularly near the interface between the substrate and the oxide layer, compared with those of the surface layer. The formation of irregular type of pores seemed to be attributed to spark discharge phenomena which heavily occurred during increasing the anodic voltage. The pore diameter and the cell size increased, and the number of cells per unit area decreased with the increasing time. From the XPS results, it was shown that component elements of the electrolytes, P and S, existed in the chemical states of $PO_4^{-3}$ , $P_2$$O_{5}$, $SO_4^{-2}$ , $SO_3^{-2}$ , P, S, etc., which were penetrated from the electrolytes into the oxide layer during anodization.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.72-72
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• 2001

Plasma polymerized thin films have been deposited on Si(lOO) substrates at $25-400^{\circ}C$ using thiophene ($C_4H_4S$) precursor by plasma assisted chemical vapor deposition (PACVD) method for low-dielectric device application. In order to compare physical properties of the as-grown thin films, the effects of the plasma power, gas flow ratio and deposition temperature on the dielectric constant and thermal stability were mainly studied. XRD and TED studies revealed that the as-grown thin films have highly oriented amorphous polymer structure. XPS data showed that the polymerized thin films that grown under different RF power and deposition temperature as well as different gas ratio of $Ar:H_2$ have different stoichiometric ratio of C and S compared with that of monomer, indicating a formation of mixture polymers. Moreover, we also realized that oxygen free and thermally stable polymer thin films could be grown at even $400^{\circ}C$. The results of SEM, AFM and TEM showed that the polymer films with smooth surface and sharp interface could be grown under various deposition conditions. From the electrical property measurements such as I-V and C-V characteristics, the minimum dielectric constant and the best leakage current were obtained to be about 3.22 and $10-11{\;}A/\textrm{cm}^2$, respectively.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.435-444
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• 2001

WC-( $Ti_{1-x}$ A $l_{x}$) N coatings of constant changing Al concentration were deposited on S45C substrates by high-ionization sputtered PVD method. The Al concentration could be controlled by using evaporation source for Al and fixing the evaporation rate of the metals (i.e, WC- $Ti_{0.86}$A $l_{0.14}$N, WC- $Ti_{0.72}$A $l_{0.28}$N, and WC- $Ti_{0.58}$A $l_{0.42}$N). The corrosion behavior of WC-( $Ti_{1-x}$ A $l_{x}$)N coatings in a deaerated 3.5% NaCl solution was investigated by electrochemical corrosion tests and surface analyses. The measured galvanic corrosion currents between coating and substrate indicated that WC- $Ti_{0.72}$A $l_{0.28}$N coating showed the best resistance of the coating tested. The results of potentiodynamic polarization tests showed that the WC- $Ti_{0.72}$A $l_{0.28}$N coating deposited with 32W/c $m^2$ of Al target revealed higher corrosion resistance. This indicated that the WC- $Ti_{0.72}$A $l_{0.28}$N coating is effective in improving corrosion resistance. In EIS, the WC- $Ti_{0.72}$A $l_{0.28}$N coating showed one time constant loop and increased a polarization resistance of coating ( $R_{coat}$) relative to other samples. Compositional variations of WC-( $Ti_{1-x}$ A $l_{x}$)N coatings were analyzed by EDS and XRD analysis was performed to evaluate the crystal structure and compounds formation behavior. Surface morphologies of the films were observed using SEM and AFM. Scratch test was performed to measure film adhesion strength.strength. adhesion strength.strength.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.189-190
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• 2011

Cu가 기존 배선물질인 Al을 대체함에 따라 resistance-capacitance (RC) delay나 electromigration (EM) 등의 문제들이 어느 정도 해결되었다. 그러나 지속적인 배선 폭의 감소로 배선의 저항 증가, EM 현상 강화 그리고 stability 악화 등의 문제가 지속적으로 야기되고 있다. 이를 해결하기 위한 방법으로 Cu alloy seed layer를 이용한 barrier 자가형성 공정에 대한 연구를 진행하였다. 이 공정은 Cu 합금을 seed layer로 사용하여 도금을 한 후 열처리를 통해 SiO2와의 계면에서 barrier를 자가 형성시키는 공정이다. 이 공정은 매우 균일하고 얇은 barrier를 형성할 수 있고 별도의 barrier와 glue layer를 형성하지 않아 seed layer를 위한 공간을 추가로 확보할 수 있는 장점을 가지고 있다. 또한, via bottom에 barrier가 형성되지 않아 배선 전체 저항을 급격히 낮출 수 있다. 합금 물질로는 초기 Al이나 Mg에 대한 연구가 진행되었으나, 낮은 oxide formation energy로 인해 SiO2에 과도한 손상을 주는 문제점이 제기되었다. 최근 Mn을 합금 물질로 사용한 안정적인 barrier 형성 공정이 보고 되고 있다. 하지만, barrier 형성을 하기 위해 300도 이상의 열처리 온도가 필요하고 열처리 시간 또한 긴 단점이 있다. 본 실험에서는 co-sputtering system을 사용하여 Cu-V 합금을 형성하였고, barrier를 자가 형성을 위해 300도에서 500도까지 열처리 온도를 변화시키며 1시간 동안 열처리를 실시하였다. Cu-V 공정 조건 확립을 위해 AFM, XRD, 4-point probe system을 이용하여 표면 거칠기, 결정성과 비저항을 평가하였다. Cu-V 박막 내 V의 함량은 V target의 plasma power density를 변화시켜 조절 하였으며 XPS를 통해 분석하였다. 열처리 후 시편의 단면을 TEM으로 분석하여 Cu-V 박막과 SiO2 사이에 interlayer가 형성된 것을 확인 하였으며 EDS를 이용한 element mapping을 통해 Cu-V 내 V의 거동과 interlayer의 성분을 확인하였다. PVD Cu-V 박막은 기판 온도에 큰 영향을 받았고, 200 도 이상에서는 Cu의 높은 표면에너지에 의한 agglomeration 현상으로 거친 표면을 가지는 박막이 형성되었다. 7.61 at.%의 V함량을 가지는 Cu-V 박막을 300도에서 1시간 열처리 한 결과 4.5 nm의 V based oxide interlayer가 형성된 것을 확인하였다. 열처리에 의해 Cu-V 박막 내 V은 SiO2와의 계면과 박막 표면으로 확산하며 oxide를 형성했으며 Cu-V 박막 내 V 함량은 줄어들었다. 300, 400, 500도에서 열처리 한 결과 동일 조성과 열처리 온도에서 Cu-Mn에 의해 형성된 interlayer의 두께 보다 두껍게 성장 했다. 이는 V의 oxide formation nergyrk Mn 보다 작으므로 SiO2와의 계면에서 산화막 형성이 쉽기 때문으로 판단된다. 또한, V+5 이온 반경이 Mn+2 이온 반경보다 작아 oxide 내부에서 확산이 용이하며 oxide 박막 내에 여기되는 전기장이 더 큰 산화수를 가지는 V의 경우 더 크기 때문으로 판단된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.434-435
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• 2012

Plasma enhanced chemical vapor deposition (PECVD) silicon dioxide thin films have many applications in semiconductor manufacturing such as inter-level dielectric and gate dielectric metal oxide semiconductor field effect transistors (MOSFETs). Fundamental chemical reaction for the formation of SiO2 includes SiH4 and O2, but mixture of SiH4 and N2O is preferable because of lower hydrogen concentration in the deposited film [1]. It is also known that binding energy of N-N is higher than that of N-O, so the particle generation by molecular reaction can be reduced by reducing reactive nitrogen during the deposition process. However, nitrous oxide (N2O) gives rise to nitric oxide (NO) on reaction with oxygen atoms, which in turn reacts with ozone. NO became a greenhouse gas which is naturally occurred regulating of stratospheric ozone. In fact, it takes global warming effect about 300 times higher than carbon dioxide (CO2). Industries regard that N2O is inevitable for their device fabrication; however, it is worthwhile to develop a marginable nitrous oxide free process for university lab classes considering educational and environmental purpose. In this paper, we developed environmental friendly and material cost efficient SiO2 deposition process by substituting N2O with O2 targeting university hands-on laboratory course. Experiment was performed by two level statistical design of experiment (DOE) with three process parameters including RF power, susceptor temperature, and oxygen gas flow. Responses of interests to optimize the process were deposition rate, film uniformity, surface roughness, and electrical dielectric property. We observed some power like particle formation on wafer in some experiment, and we postulate that the thermal and electrical energy to dissociate gas molecule was relatively lower than other runs. However, we were able to find a marginable process region with less than 3% uniformity requirement in our process optimization goal. Surface roughness measured by atomic force microscopy (AFM) presented some evidence of the agglomeration of silane related particles, and the result was still satisfactory for the purpose of this research. This newly developed SiO2 deposition process is currently under verification with repeated experimental run on 4 inches wafer, and it will be adopted to Semiconductor Material and Process course offered in the Department of Electronic Engineering at Myongji University from spring semester in 2012.