• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.391-394
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• 2002

Transparent conductive oxides (TCO) are necessary as front electrode for most thin film solar cell. In our paper, transparent conducting aluminum-doped Zinc oxide films (ZnO:Al) were prepared by rf magnetron sputtering on glass (Corning 1737) substrate as a variation of the deposition condition. After deposition, the smooth ZnO:Al films were etched in diluted HCl (0.5%) to examine the electrical and surface morphology Properties as a variation of the time. The most important deposition condition of surface-textured ZnO films by chemical etching is the processing pressure and the substrate temperature. In low pressures (0.9 mTorr) and high substrate temperatures ($\leq$30$0^{\circ}C$), the surface morphology of films exhibits a more dense and compact film structure with effective light-trapping to apply the silicon thin film solar cells.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1468-1476
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• 1996

Surface integrity is dictated by the fabrication process of the metal part. In this work, steel specimens were prepared under various mechine conditions to achieve different degrees of deformation state. The tribological characteristics of the speciments were tested using a pin-on-disk type apparatus and other surface characterization tools. It is shown that though frictional characteristics are similar, the wear rate is significantrly affected by the properties of the surface. In the case of steel, surface cracks resulted in high wear despite the relatively high hardness of the specimen. Also, the sliding action were found to reduce the residual stress on the surface. These results indicate that there is a strong relationship between surface integrity and the tribological properties of steel, and therefore the machining condition should be optimized woth respect to tribological performance of a steel part.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.597-602
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• 2000

In a MEMS(micro-electro mechanical system), the fluid may slip near the surface of a solid and have a discontinuous temperature profile. A numerical prediction in this slip flow region can provide a reasonable guide for the design and fabrication of micro devices. The compressible Navier-Stokes equation with Maxwell/smoluchowski boundary condition is solved for two simple systems; couette flow and pressure driven flow in a long channel. We found that the couette flow could be regarded as an incompressible system in low speed regions. For the pressure driven flow system, we observed nonlinear distribution of pressure in the long channel and numerical results showed a good agreement with the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.47-54
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• 2009

Spin coaters are the essential instruments in micro-fabrication processes, which apply uniform thin films to flat substrates. In this research, a spin coater diagnosis system is developed to detect the abnormal operation of TFT-LCD process in real time. To facilitate the real-time data acquisition and analysis, the circular-buffered continuous data transfer and the short-time Fourier transform are applied to the fault diagnosis system. To determine whether the system condition is normal or not, a steady-state detection algorithm and a frequency spectrum comparison algorithm using confidence interval are newly devised. Since abnormal condition of a spin coater is rarely encountered, algorithm is tested on a CD-ROM drive and the developed program is verified by a function generator. Actual threshold values for the fault detection are tuned in a spin coater in process.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.288-289
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• 2009

We report an optimum fabrication condition for formation of concave lens shaped core cross-section of silica single-mode fibers with hydrofluoric (HF) acid solutions and arc discharge. A desired depth of curved cross-section of the silica fiber core and its surface smoothness were obtained with optimized concentration of the HF solution, etching time, and arc discharge condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.14-17
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• 1992

To analyze Nonvolatile SNOSFET(polySilicon-Nitride-Oxide-Semiconductor Field Effect Transistor) memory device, two dimensional numerical computer simulation program was developed. The equation discretization was performed by the Finite difference method and the solution was derived by the Iteration method. The doping profile of n-channel device which was fabricated by 1Mbit CMOS process was observed. The electrical potential and the carrier concentration distribution to applied bias condition were observed in the inner of a device. As a result of the write and the erase to memory charge quantity, the threshold voltage shift is expected. Therefore, without device fabrication, the operating characteristics of the device was observed under various the processing and the operating condition.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.178-186
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• 2009

Most of automotive plastic parts are injection molding products. Inspection of total product is impossible, because number of product to inspect is too many and various. Condition-based Monitoring was proposed to decrease cost and time for inspecting. In this research, a system that predicts quality of part at fabrication point of time, and confirms informations through the internet was developed. Cavity sensors were installed inside of mold, and gathered signals as measuring, and through this process Sensor-based Monitoring system can be observed manufacturing of a part. Monitoring system transmits signals to client through the internet, and finally developed system provides manufacturing informations and predictions of quality as web-based monitoring.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.210-215
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• 1994

In the CMOS device, Counter doping is needed to adjust threshold voltage because of the difference between n-MOSFET and p-MOSFET well doping concentration when n+ polysilicon gate is used. Therefore buried channel is formed in the p-channel MOSFET degrading properties. So well doping concentration and doping condition should be considered in fabrication process and device design. Here we are to extract the initial process condition using simulation and fabricate p-MOSFET device and then compare the subthreshold characteristics of simulated and fabricated device.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.245-256
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• 1995

SMC(Sheet Molding Compound), a thermoset composite material which consists of unsaturated polyester resin, fiberglass strands, fillers, and various chemical additives for curing agent, has been widely used in fabrication of structural components. The mechanical properties of molded SMS parts are strongly dependent on material flow results during compression molding process, while such flow in molds is affected by material characteristics. For numerical simulation of SMC molding process, estimation of material property of SMC must be accomplished. In this study, flow resistance of SMC was estimated through a simple compression test using a lubricant with grease oil under the constant strain rate condition at various temperatures and the result was compared with other material data available in the literature. The accuracy of the experimentally determined flow resistance was tested by finite element analyses of compression molding of SMC. Simulation results were compared with experimental results under the plane strain condition.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.300-303
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• 2002

In recent days the more use of CFRP composite is in the airplane, and sport goods, etc., the mote necessity of research on it in this engineering. In this research, the CFRP composite specimen are fabricated by 48 CFRP plies with 6 orientation angles. and the specimens are drilled with 4tools The results are analyzed with consideration of cutting force, type of tools and fabrication condition. The specimens with each drilling conditions are also investigated with SEM. The optimal drilling conditions such as drill types and cutting force with respect to the fabricating condition are studied.