• Journal of the Semiconductor & Display Technology
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• v.22 no.2
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• pp.81-86
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• 2023

Recently, there has been an increased demand for light-emitting diode (LED) due to the growing emphasis on environmental protection. However, the use of GaN-based sapphire in LED manufacturing leads to the generation of defects, such as dislocations caused by lattice mismatch, which ultimately reduces the luminous efficiency of LEDs. Moreover, most inspections for LED semiconductors focus on evaluating the luminous efficiency after packaging. To address these challenges, this paper aims to detect defects at the wafer stage, which could potentially improve the manufacturing process and reduce costs. To achieve this, image processing and deep learning-based defect detection techniques for Sapphire Epi-Wafer used in Green LED manufacturing were developed and compared. Through performance evaluation of each algorithm, it was found that the deep learning approach outperformed the image processing approach in terms of detection accuracy and efficiency.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.18.1-18.1
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• 2008

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.83.1-83
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• 2000

• Proceedings of the Materials Research Society of Korea Conference
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• 1997.05a
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• pp.31-31
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• 1997

• Proceedings of the Optical Society of Korea Conference
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• 1997.08a
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• pp.87-87
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• 1997

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.231-238
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• 2015

Sapphire single crystals have been highlighted for epitaxial of gallium nitride films in high-power laser and light emitting diode industries. Among the many crystal growth methods, vertical Bridgman process is an excellent commercial method for growing high quality sapphire crystals with c-axis. In this study, the thermally induced stress in Sapphire during the vertical Bridgman crystal growth process was investigated using a finite element model. A vertical Bridgman process of 2-inch Sapphire was considered for the model. The effects of vertical and transverse temperature gradients on the thermal stress during the process were discussed based on the finite element analysis results.

• Tribology and Lubricants
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• v.33 no.3
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• pp.106-111
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• 2017

Sapphire is an anisotropic material with excellent physical and chemical properties and is used as a substrate material in various fields such as LED (light emitting diode), power semiconductor, superconductor, sensor, and optical devices. Sapphire is processed into the final substrate through multi-wire saw, double-side lapping, heat treatment, diamond mechanical polishing, and chemical mechanical polishing. Among these, chemical mechanical polishing is the key process that determines the final surface quality of the substrate. Recent studies have reported that the material removal characteristics during chemical mechanical polishing changes according to the crystal orientations, however, detailed analysis of this phenomenon has not reported. In this work, we carried out chemical mechanical polishing of C(0001), R($1{\bar{1}}02$), and A($11{\bar{2}}0$) substrates with different sapphire crystal planes, and analyzed the effect of crystal orientation on the material removal characteristics and their correlations. We measured the material removal rate and frictional force to determine the material removal phenomenon, and performed nano-indentation to evaluate the material characteristics before and after the reaction. Our findings show that the material removal rate and frictional force depend on the crystal orientation, and the chemical reaction between the sapphire substrate and the slurry accelerates the material removal rate during chemical mechanical polishing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.75-80
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• 2013

Single crystal sapphire being used in high technology industry is a brittle material with a high hardness and excellent physical properties. ELID(Electrolytic In-Process Dressing) grinding technology was applied to material removal machining process of single crystal sapphire wafer. Ultrasonic vibration which added to material using ultrasonic table was adopted to efficient ELID grinding of sapphire materials. The evaluation of the ground surface of single crystal sapphire wafer was carried out by means of surface measuring by using AFM(Atomic Force Microscope), surface roughness tester and optical microscope device. As the results of experiment, it was shown that more efficient grinding was conducted when using ultrasonic table. In case of using #170 grinding wheel, surface roughness of ELID ground specimen in using ultrasonic table was superior to ELID ground specimen without ultrasonic table. However, In case of using #2000 grinding wheel, surface roughness of ELID ground specimen in using ultrasonic table was inferior to ELID ground specimen without ultrasonic table.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.3
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• pp.129-134
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• 2013

Sapphire wafers are used as an important substrate for the production of blue LED (light emitting diode) and the LED's performance largely depends on the quality of the sapphire single crystals. There are several crystal growth methods for sapphire crystals and Kyropoulos method is an efficient way to grow large diameter and high-quality sapphire single crystals with low dislocation density. During Kyropoulos growth, the convection of molten melt is largely influenced by the hot zone geometry such as crucible shape, heater and refractory arrangements. In this study, CFD (computational fluid dynamics) simulations were performed according to the bottom/side ratios (per unit of the crucible surface area) of heaters. And, based on the results of analysis, the molten alumina flows and remelting phenomena were analyzed.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.45-49
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• 2014

In this study, we grew non-polar ZnO nanostructure on (1-102) R-plane sapphire substrates. As for growth method of ZnO, we used hydrothermal synthesis which is known to have the advantages of low cost and easy process. For growth of non-polar, the deposited AZO seed buffer layer with of 80 nm on R-plane sapphire by radio frequency magnetron sputter was annealed by RTA(rapid thermal annealing) in the argon atmosphere. After that, we grew ZnO nanostructure on AZO seed layer by the added hexamethylenetramine (HMT) solution and sodium citrate at $90^{\circ}C$. With two types of additives into solution, we investigated the structures and shapes of ZnO nanorods. Also, we investigate the possibility of formation of 2D non-polar ZnO layer by changing the ratio of two additives. As a result, we could get the non-polar A-plane ZnO layer with well optimized additives' concentrations.