• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.301-306
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• 2000

This paper describes on the fabrication of a SOI substrate by SDB technology and electrochemical etch-stop. The surface of the thinned SDB SOI substrate is more uniform than that of grinding or polishing by mechanical method, and this process was found to be a very accurate method for SOI thickness control. During electrochemical etch-stop, leakage current versus voltage curves were measured for analysis of the open current potential(OCP) point, the passivation potential(PP) point and anodic passivation potential. The surface roughness and the controlled thickness selectivity of the fabricated a SDB SOI substrate were evaluated by using AFM and SEM, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.50-56
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• 2004

Finishing is the final process in molds manufacturing and consumes much process time. Also, it influences on surface quality of molds. But, there are few systematic methods to control the process. In this work, basic experiments were carried out to study the machining characteristics of the finishing tools. From the experiments, critical surface roughness and wear coefficient are suggested to reduce the number of finishing steps and to plan a systematic finishing procedure. Comparison experiments were carried out between the expert's method and the new method, which is based on the results of this research. From the experiments, it is verified that the systematic method takes less time and generates less form error in the machined surface than the worker's method.

• Applied Science and Convergence Technology
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• v.25 no.2
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• pp.32-35
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• 2016

Using conventional deposition techniques, we demonstrate a method to fabricate ultra-smooth 10 nm silver films without using a wetting layer or co-depositing another material. The argon working pressure plays a crucial role in achieving an excellent surface flatness for silver films deposited by DC magnetron sputtering on an InP substrate. The formation of ultra-smooth silver thin films is very sensitive to the argon pressure. At the optimum deposition condition, a uniform silver film with an rms surface roughness of 0.81 nm has been achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.431-436
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• 2000

This paper describes on the fabrication of a SOI substrate by SDB technology and electrochemical etch-stop. The surface of the thinned SDB SOI substrate is more uniform than that of grinding or polishing by mechanical method and this process was found to be a very accurate method for SOI thickness control. During electrochemical etch-stop leakage current versus voltage curves were measured for analysis of the open current potential(OCP) point the passivation potential(PP) point and anodic passivation potential. The surface roughness and the controlled thickness selectivity of the fabricated a SDB SOI substrate were evaluated by using AFM and SEM respectively.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.98-105
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• 2000

The projectors using liquid crystal display(LCD) have faults such as low optical efficiency, low brightness and even heat generation. To solve these problems reflective-type spatial light modulators based on MEMS (Microelectromechanical Systems) technology have emerged. Digital Micromirror DeviceTM(DMDTM), which was already developed by Texas Instruments Inc., and Thin-film Micromirror ArrayTM(TMATM), which has been recently developed by Daewoo Electronics Co., are the representative examples. The display using TMATM has particularly much higher optical efficiency than other projectors. But the micromirrors manufactured by semiconductor processes have inevitable distortion because of the limitations of the manufacturing processes, so that the distortions of their surfaces have great influence on the optical efficiency of the projector. This study investigated the effects of mirror flatness on the optical performance, including the optical efficiency, of the TMATM projector. That is to say, as a part of the efforts to enhance the performance of the TMATM projector, how much influence the form errors of a micromirror surface exert on the optical efficiency and the modulation of gray scale of the projector were analyzed through a pertinent modeling and simulations.

• Journal of the Korean Magnetics Society
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• v.16 no.2
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• pp.136-139
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• 2006

The tunneling magnetoresistance (TMR) ratios of magnetic tunnel junctions (MTJs), in general, decrease abruptly above 250$^{\circ}C$ due to Mn interdiffusion from an antiferromagnet IrMn layer to a ferromagnetic CoFe and/or a tunnel barrier. To improve thermal stability, we prepared MTJs with nano-oxide layers. Using a MTJ structure consisting of underlayer CoNbZr 4/bufferlayer CoFe 10/antiferromaget IrMn 7.5/pinned layer CoFe 3/tunnel barrier AlO/freelayer CoFe 3/capping CoNbZr 2 (nm), we placed a nano-oxide layer (NOL) into the underlayer or bufferlayer. Then, the thermal, structural and magneto-electric properties were measured. The TMR ratio, surface flatness, and thermal stability of the MTJs with NOLs were promoted.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.42-50
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• 2016

Overlay welding affects the chemical components and weld hardness by dilution of the lamination layer thickness, which determines the surface properties. This study experimentally investigates different numbers of layers for overlay welding monel materials, which are anti-corrosion materials. The Fe content, weldability of the base metal and monel materials, hardness, and surface flatness were examined. Each evaluation was carried out after overlay welding with three layers on the base material and pipe base material of the plate. The Fe content was evaluated by analyzing the constituents of each layer. The Fe content was satisfactory in the three layers. The weldability of the laminate specimens was evaluated by a bending test. The hardness and bead flatness of the laminate specimens were evaluated by micro Vickers and 3D measurements. The hardness was highest in the heat-affected zone with one layer, and it decreased with increasing lamination. In the case of bead flatness, there is a sharp difference in the deviation with increasing numbers of laminations, which should be considered carefully.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.141-141
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• 2000

In situ surface magneto-optic Kerr effect(SMOKE), X-ray photoelectron spectroscopy(XPS) and low energy electron diffraction(LEED) were used to study magnetic and structural properties of ultrathin Fe films grown on the Pd(111) surface. The SMOKE measurement showed strong enhancement of ferromagnetism after proper annealing process. Simultaneous changes in morphology was checked by LEED and XPS. After room temperature Fe deposition. longitudinal magnetization appeared above a critical thickness between 2.0 and 2.5 monolayers. When annealed at 450K, 2.0 monolayer Fe film exhibited boty longitudinal and polar magnetizations while 3.0 and 5.5 monolayer films showed little changes. After annealing at 600K, both magnetizations were totally destroyed in 2.0 monolayer film, but longitudinal magnetization was enhanced in 3.0 monolayer film. In the case of 5.5 monolayer film, it was only after 660K annealing that the enhancement of the longitudinal magnetization was observed. It was concluded that the surface flatness and the amount of intermixing were critical in the development of surface magnetism of this system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.162-163
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• 2013

Single-crystal InGaZnO (IGZO) thin films were spontaneously formed as periodic layered structure along the c-axis by thermal treatment at high temperature. when the IGZO superlattice were synthesized by sol-gel method, the effects of preferred growth orientations and the flatness of ZnO buffer layer were investigated. $InGaO_3(ZnO)_2$ superlattice were favorably formed on ZnO buffer layer with single preferred orientation. Futhermore, it showed relatively high Seebeck coefficient and power factor.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.350-355
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• 2000

The fabrication of sapphire wafer in C plane has been developed by horizontal Bridgeman method and GaN based semiconductor epitaxial growth has been carried out in metal organic chemical vapour deposition. The single crystalline ingot of sapphire has been utilized for 2 inch sapphire wafers and wafer slicing and lapping machines were designed. These several steps of lapping processes provided the mirror-like surface of sapphire wafer. The measurements of the surface flatness and the roughness were carried out by the atomic force microscope. The GaN thin film growth on the developed wafer was confirmed the wafer quality and applicability to blue light emitting devices.