• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.28-33
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• 2020

Plasma etching process employs high density plasma to create surface chemistry and physical reactions, by which to remove material. Plasma chamber includes silicon-based materials such as a focus ring and gas distribution plate. Focus ring needs to be replaced after a short period. For this reason, there is a need to find materials resistant to erosion by plasma. The developed chemical vapor deposition processing to produce silicon carbide parts with high purity has also supported its widespread use in the plasma etch process. Silicon carbide maintains mechanical strength at high temperature, it have been use to chamber parts for plasma. Recently, besides the structural aspects of silicon carbide, its electrical conductivity and possibly its enhanced life time under high density plasma with less generation of contamination particles are drawing attention for use in applications such as upper electrode or focus rings, which have been made of silicon for a long time. However, especially for high purity silicon carbide focus ring, which has usually been made by the chemical vapor deposition method, there has been no study about quality improvement. The goal of this study is to reduce surface roughness and depth of damage by diamond tool grit size and tool dressing of diamond tools for precise dimensional assurance of focus rings.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.539-545
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• 2014

Contact resistivity between silver electrodes and the emitter layer of a silicon solar cell wafer has been measured using either the circular transmission line method or the linear transmission line method. The circular transmission line method has an advantage over the linear transmission line method, in that it does not require an additional process for mesa etching to eliminate the leakage current. In contrast, the linear transmission line method has the advantage that its specimen can be acquired directly from a silicon solar cell. In this study, measured resistance data for the calculation of contact resistivity is compared for these two methods, and the mechanism by which the linear transmission line method can more realistically reflect the impact of the width and thickness of a silver electrode on contact resistivity is investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.185.2-185.2
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• 2016

The plasma density is an essential plasma parameter describing plasma physics. Furthermore, it affects the throughput and uniformity of plasma processing (etching, deposition, ashing, etc). Therefore, a novel technique for plasma density measurement has been attracting considerable attention. Microwave probe is a promising diagnostic technique. Various type of cutoff, hairpin, impedance, transmission, and absorption probes have been developed and investigated. Recently, based on the basic type of probes, modified flat probe (curling and multipole probes), have been developing for in situ processing plasma monitoring. There is a need for comparative study between the probes. It can give some hints on choosing the reliable probe and application of the probes. In this presentation, we make attempt of numerical study of different kinds of microwave probes. Characteristics of frequency spectrum from probes were analyzed by using three-dimensional electromagnetic simulation. The plasma density, obtained from the spectrum, was compared with simulation input plasma density. The different microwave probe behavior with changes of plasma density, sheath and pressure were found. To confirm the result experimentally, we performed the comparative experiment between cutoff and hairpin probes. The sheath and collision effects are corrected for each probe. The results were reasonably interpreted based on the above simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1297-1303
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• 2015

The internal chromium plating of a long-axis tube is widely used in military and industrial application, with the thick hard plating formed using a mixed solution of Chromium acid and catalytic $H_2SO_4$. A large-caliber gun can endure a high explosive force as a result of the increased stiffness and wear resistance provided by this internal hard chromium surface. The internal chromium layer of a tube is prone to exfoliation caused by the high kinetic energy of the projectile and high pressure of the explosion. Therefore, we reviewed the plating process. Chromium plating comprises many steps, including the removal of Grease, water cleaning, electrolytic abrasion, etching, plating, water cleaning, and hydrogen brittleness removal. The exfoliated chromium plating layer is affected by the adhesion property of the plating. In particular, the Fe concentration of the electrolyte affects the adhesion property. The optimum Fe concentration for effectively suppressing the exfoliation of the plating layer was established by using a scanning electron microscope to determine the surface roughness, and the effectiveness was proved in an adhesion test, etc.

• Journal of Periodontal and Implant Science
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• v.38 no.4
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• pp.595-602
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• 2008

Purpose: Ti-6Al-4V alloy is widely used as an implant material because of its good biocompatibility and good mechanical property compared with commercial pure titanium. Otherwise, toxicity of aluminum and vanadium in vivo has been reported. Ti-8Ta-3Nb alloy is recently developed in the R&D Center for Ti and Special Alloys and it was reported that this alloy has high mechanical strength, no cytotoxicity and similar biocompatibility to commercial pure titanium, but many studies are needed for its clinical use. In these experiment, we carried out different surface treatment on each Ti-8Ta-3Nb alloy disks, then cultured cell on it and assessed biological response. Materials and Methods: cpTi, Ti-6Al-4V, Ti-8Ta-3Nb alloy disks were prepared and carried out sandblasting and acid etching (SLA) or alkali-heat treatment (AH) on the Ti-8Ta-3Nb alloy disks. We cultured primary rat calvarial cells on each surface and assessed early cell attachment and proliferation by scanning electron microscopy, cell proliferation, alkaline phosphatase activity. Result: The rates of cell proliferation on the cpTi, Ti-8Ta-3Nb AH disks were higher than others (p<0.05) and alkaline phosphatase activity was significantly enhanced on the Ti-STa-8Nb AH disks(p<0.05). Conclusion: Most favorable cell response was shown on the Ti-8Ta-3Nb AH surfaces. It is supposed that alkali-heat treatment of the Ti-8Ta-3Nb alloy could be induced earlier bone healing and osseointegration than smooth surface.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.4
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• pp.259-267
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• 2002

We present a novel 3D fabrication method with single X-ray process utilizing an X-ray mask in which a micro-actuator is integrated. An X-ray absorber is electroplated on the shuttle mass driven by the integrated micro-actuator during deep X-ray exposures. 3D microstructures are revealed by development kinetics and modulated in-depth dose distribution in resist, usually PMMA. Fabrication of X-ray masks with integrated electrothermal xy-stage and electrostatic actuator is presented along with discussions on PMMA development characteristics. Both devices use $20-\mu\textrm{m}$-thick overhanging single crystal Si as a structural material and fabricated using deep reactive ion etching of silicon-on-insulator wafer, phosphorous diffusion, gold electroplating, and bulk micromachining process. In electrostatic devices, $10-\mu\textrm{m}-thick$ gold absorber on $1mm{\times}1mm$ Si shuttle mass is supported by $10-\mu\textrm{m}-wide$, 1-mm-long suspension beams and oscillated by comb electrodes during X-ray exposures. In electrothermal devices, gold absorber on 1.42 mm diameter shuttle mass is oscillated in x and y directions sequentially by thermal expansion caused by joule heating of the corresponding bent beam actuators. The fundamental frequency and amplitude of the electrostatic devices are around 3.6 kHz and $20\mu\textrm{m}$, respectively, for a dc bias of 100 V and an ac bias of 20 VP-P (peak-peak). Displacements in x and y directions of the electrothermal devices are both around $20{\;}\mu\textrm{m}$at 742 mW input power. S-shaped and conical shaped PMMA microstructures are demonstrated through X-ray experiments with the fabricated devices.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.603-612
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• 2000

Corrosion characteristics on the 12Cr alloy steel of turbine blade was electro-chemically investigated in 3.5wt% NaCI and 12.7wt% Na2S04 solution, respectively. Electro-chemical polarization test, Huey test and Oxalic acid etching test were previously conducted to estimate corrosion susceptibility of the material. And, using the horizontal corrosion fatigue tester, corrosion fatigue characteristics of 12Cr alloy steel in distilled water, 3.5wt% NaCI solution, and 12.7wt%(1M) Na2S04 solution were also fracture-mechanically estimated and compared their results. Parameter considered was room temperature, 60'C and 90'C. Corrosion fatigue crack length was measured by DC potential difference method.Obtained results are as follows,1) 12Cr alloy steel showed high corrosion rate in 3.5wt% NaCI solution and Na2S04 solution at high tempratue.2) Intergranular corrosion sensitivity of 12 Cr alloy was smaller than austenitic stainless steel.3) Corrosion fatigue crack growth rate in 3.5wt% NaCI and 12.7wt%(IM) Na2S04 solution is entirely higher than in the distilled water, and also increased with the temperature increase.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1051-1054
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• 2000

We developed the micro CSF (celebrospinal fluid) shunt valve with surface and bulk micromachining technology in polymer MEMS. This micro CSF shunt valve was formed with four micro check valves to have a membrane connected to the anchor with the four bridges. The up-down movement of the membrane made the CSF on & off and the valve characteristic such as open pressure was controlled by the thickness and shape of the bridge and the membrane. The membrane, anchor and bridge layer were made of the $O_2$ RIE (reactive ion etching) patterned Parylene thin film to be about 5~10 microns in thickness on the silicon wafer. The dimension of the rectangular nozzle is 0.2＊0.2 $\textrm{mm}^2$ and the membrane 0.45 mm in diameter. The bridge width is designed variously from 0.04 mm to 0.12 mm to control the valve characteristics. To protect the membrane and bridge in the CSF flow, we developed the packaging system for the CSF micro shunt valve with the deep RIE of the silicon wafer. Using this package, we can control the gap size between the membrane and the nozzle, and protect the bridge not to be broken in the flow. The total dimension of the assembled system is 2.5＊2.5 $\textrm{mm}^2$ in square, 0.8 mm in height. We could precisely control the burst pressure and low rate of the valve varing the design parameters, and develop the whole CSF shunt system using this polymer MEMS fabricated CSF shunt valve.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.281-281
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• 2014

The field emission properties of GaN are reported in the present study. To be a good field emitter, it requires a low work function, high aspect ratio, and strong mechanical stability. In the case of GaN, it has a quite low work function (4.1eV) and strong chemical/mechanical/thermal stabilities. However, so far, it was difficult to fabricate vertical GaN nanostructures with a high aspect ratio. In this study, we successfully achieved vertically well aligned GaN nanostructures with chemical vapor-phase etching methods [1] (Fig. 1). In this method, we chemically etched the GaN film using hydrogen chloride and ammonia gases at high temperature around $900^{\circ}C$. This process effectively forms vertical nanostructures without patterning procedure. This favorable shape of GaN nanostructures for electron emitting results in excellent field emission properties such as a low turn-on field and long term stability. In addition, we observed a uniform fluorescence image from a phosphor film attached at the anode part. The turn-on field for the GaN nanostructures is found to be about $0.8V/{\mu}m$ at current density of $20{\mu}A$/cm^2. This value is even lower than that of typical carbon nanotubes ($1V/{\mu}m$). Moreover, threshold field is $1.8V/{\mu}m$ at current density of $1mA$/cm^2. The GaN nanostructures achieved a high current density within a small applied field range. We believe that our chemically etched vertical nanostructures are the promising structures for various field emitting devices.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.47-53
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• 2013

We have investigated the traits of clad metals in hot-rolled clad steel plates, including the sensitization and mechanical properties of STS 316 steel plate and carbon steel (A516), under various specific circumstances regarding post heat treatment, multilayered welds, and thick or repeated welds for repair. For evaluations, sectioned weldments and external surfaces were investigated to reveal the degree of sensitization by micro vickers hardness, tensile, and etching tests the results were compared with those of EPR tests. The clad steel plates were butt-welded using FCAW and SAW with the time of heat treatment as the variable, a that was conducted at $625^{\circ}C$, for 80, 160, 320, 640, and 1280 min. Then, the change in corrosion resistance was evaluated in these specimens. With carbon steel (A516), as the heat treatment time increased, the annealing effect caused the tensile strength to decrease. The micro-hardness gradually increased and decreased after 640 min. The elongation and contraction of the area also increased gradually. The oxalic acid etch test and EPR test on STS316 and the clad metal showed STEP structure and no sensitization. From the test results on multi-layered and repair welds, it could be concluded that there is no effect on the corrosion resistance of clad metals. The purpose of this study was to suggest some considerations for developing on-site techniques to evaluate the sensitization of stainless steels.