• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.113-120
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• 1994

Silicon flow sensor that can detect the velocity and direction of air flow was designed and fabricated by integrated circuit process and bulk micromachining technique. The flow sensor consists of three-layered dielectric diaphragm, a heater at the center of the diaphragm, and four thermopiles surrounding the heater at each side of diaphragm as sensing elements. This diaphragm structure contributes to improve the sensitivity of the sensor due to excellent thermal isolation property of dielectric materials and their tiny thickness. The flow sensor has good axial symmetry to sense 2-D air flow with the optimized sensing position in the proposed structure. The sensor is fabricated using CMOS compatible process followed by the anisotropic etching of silicon in KOH and EDP solutions to form I$\mu$ m thick dielectric diaphragm as the last step. TCR(Temperature Coefficient of Resistance) of the heater of the fabricated sensors was measured to calculate the operating temperature of the heater and the output voltage of the sensor with respect to flow velocity was also measured. The TCR of the polysilicon heater resistor is 697ppm/K, and the operating temperature of the heater is 331$^{\circ}C$ when the applied voltage is 5V. Measured sensitivity of the sensor is 18.7mV/(m/s)$^{1/2}$ for the flow velocity of smaller than 10m/s.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.168-169
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• 2000

We have tried to enhance the density of the near-field optical memory and to improve the recording/readout speed. The current optical memory has the limitation in both density and speed. This barrier due to the far-field nature can be overcome by the use of the near-field$^{(1)}$ . The optical data storage density can be increased by reducing the size of the nanometric aperture where the near-field is obtained. To fabricate the aperture in precise dimension, we applied the orientation-dependent / anisotropic etching property of crystal Si often employed in the field of MEMS$^{(2)}$ . And so we fabricated the 10$\times$10 aperture array. This array will be also the indispensable part for speeding up. One will see the possibility of the multi-tracking pickup in the phase changing type memory through this array$^{(3)}$ . This aperture array will be expected to write the bit-mark whose size is about 100nm. We will show the recent result obtained. (omitted)

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1131-1137
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• 2015

Gallium nitride (GaN) is a promising material for next-generation high-power applications due to its wide bandgap, high breakdown field, high electron mobility, and good thermal conductivity. From a structure point of view, the vertical device is more suitable to high-power applications than planar devices because of its area effectiveness. However, it is challenging to obtain a completely upright vertical structure due to inevitable sidewall slope in anisotropic etching of GaN. In this letter, we design and analyze the enhancement-mode n-channel vertical GaN MOSFET with variation of sidewall gate angle by two-dimensional (2D) technology computer-aided design (TCAD) simulations. As the sidewall slope gets closer to right angle, the device performances are improved since a gradual slope provides a leakage current path through the bulk region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1642-1648
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• 2006

This paper describes enhancement of the mixing efficiency of a multilamination micro mixer by adding a number of recirculation zones downstream of the mixing zone. Numerical simulation was employed to estimate the mixing efficiency and the pressure drop under various conditions. Numerical results indicated that recirculation micro mixer brought about not only the increase of the mixing efficiency but also the decrease of the pressure drop. Micro mixers were fabricated using photosensitive glass by anisotropic wet etching technique. The width and height of the micro channel were $150{\mu}m$ and $500{\mu}m$, respectively. The performance of micro mixer was measured using color intensity variation of the fluid. Except for extremely low Re below 40, the recirculation micro mixer of the present study showed improved mixing. And the enhancement of the mixing increased as Re rose. When Re increased beyond 400, more than 90% of the mixing was observed in the experiment.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.114-114
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• 2012

Metal-oxide-semiconductor field-effect transistors (MOSFETs)의 critical dimension (CD)가 sub 45 nm로 줄어듬에 따라 기존에 gate dielectric으로 사용하고 있는 SiO2에서 발생되는 high gate leakage current 때문에 새로운 high dielectric constant (k) 물질들이 연구되기 시작하였다. 여러 가지 high-k 물질 중에서, aluminum-oxide (Al2O3)는 높은 dielectric constant (~10)와 전자 터널링 barrier height (~2eV) 등을 가지기 때문에 많은 연구가 되고 있다. 그러나 Al2O3를 anisotropic한 patterning을 하기 위해 주로 사용되고 있는 halogen-based 플라즈마 식각 과정에서 나타나는 Al2O3와 하부 layer간의 낮은 식각 selectivity 뿐만 아니라 표면에 발생되는 defect, stoichiometry modification, roughness 변화 등의 많은 문제점들로 인하여 device performance가 감소하기 때문에 이를 해결하기 위한 많은 연구들이 진행중이다. 따라서 본 연구에서는 실리콘 기판위의 atomic layer deposition (ALD)로 증착된 Al2O3를 BCl3/Ar 중성빔을 이용하여 원자층 식각한 후 식각 특성을 분석해 보았다. Al2O3 표면을 BCl3로 absorption시킨 후 Ar 중성빔으로 desorption 시키는 과정에서 volatile한 aluminum-chlorides와 boron oxychloride가 형성되어 layer by layer로 제거됨을 관찰 할 수 있었다.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.127-135
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• 1994

We investigated the bonding interfaces of directly-bonded Si-Si and $Si-Sio_{2}$/Si wafer pairs. By the angle lapping-delineation, anisotropic etching, and (FIR)-TEM observation methods, we studied on the interface defects and the transient region originated from the interface stress, the various types of voids, the formation and stability of interfacial oxide. We also compared the interface image of the bonded $Si-Sio_{2}$ with that of a typically grown $Si-Sio_{2}$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.100.2-100.2
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• 2012

Surface texturing of crystalline silicon is carried out in alkaline solutions for anisotropic etching that leads to random pyramids of about $10{\mu}m$ in size. Recently textured pyramids size gradually reduced using new solution. In this paper, we investigated that texture pyramids size had an impact on emitter property and front electrode (Ag) contact. To make small (${\sim}3{\mu}m$) and large (${\sim}10{\mu}m$) pyramids size, texturing times control and one side texturing using a silicon nitride film were carried out. Then formation and quality of POCl3-diffused n+ emitter in furnace compare with small and large pyramids by using SEM images, simulation (SILVACO, Athena module) and emitter saturation current density (J0e). After metallization, Ag contact resistance was measured by transfer length method (TLM) pattern. And surface distributions of Ag crystallites were observed by SEM images. Also, performance of cell which is fabricated by screen-printed solar cells is compared by light I-V.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.483-493
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• 1995

The microstructural changes during semi-solid state processing of hypereutectic Al-Si alloy has been investigated in the present study. Stirring of semi-solid slurry results in the morphological changes of the primary Si particles, i.e. from angular rod shape to near-spherical shape. Besides the spherodization of primary Si particles, the average particle size increases, especially, at much higher rate in the final stage than that in the early stage of stirring. Various microstructure characterization techniques, such as anisotropic etching, SEM imaging and ECP analysis, reveal that the spherodization of primary Si particles occurs by the combinations of the mechanisms of coalescence, fracture, and wear of the individual particles. Isothermal shearing of hypereutectic Al-Si at $580^{\circ}C$ shows that spherical ${\alpha}-Al$ particles are formed by the dissociation of Al-Si eutectic structure at the early stage of isothermal shearing. The spherical ${\alpha}-Al$ particles gradually grow by the mechanisms of Ostwald ripening and coalescence of the particles.

• Journal of Information Display
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• v.11 no.2
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• pp.84-90
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• 2010

This paper presents the effects of a dielectric layer and an electrolyte on the driving performance of an electrowetting on dielectric (EWOD)-based liquid lens. The range of tunable focal length of the EWOD-based liquid lens was highly dependent on the conditions of the dielectric layer, which included an inorganic oxide layer and an organic hydrophobic layer. Moreover, experiments on the physical and optical durability of electrolyte by varying temperature conditions, were conducted and their results were discussed. Finally, the lens with a truncated-pyramid silicon cavity having a sidewall dielectrics and electrode was fabricated by anisotropic etching and other micro-electromechanical systems (MEMS) technologies in order to demonstrate its performance. The lens with $0.6-{\mu}m$-thick $SiO_2$ layer and 10 wt% LiCl-electrolyte exhibited brilliant focal-length tunability from infinity to 3.19 mm.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.2
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• pp.132-139
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• 2000

This paper reports a novel micromachining process based on UV-LIGA process and (110) silicon anisotropic etching for fabrication of a high-aspect-ratio comb actuator. The comb electrodes are fabricated by (110) SILICON comb structure considering the etch-rate-ratio between (110) and (111) planes and lateral etch rate of a beam-type structure. The fabricated structure was$ 400\mum \; thick\; and\; 18\mum$ wide comb electrodes separated by $7\mim$ so that the height-gap ratio was about 57. Also considering resonant frequency of the comb actuator and the frequency-matching between sensing and driving mode for gyroscope application, we designed the number, width, height and length of the spring structures. Electroplated gold springs on both sides of the seismic mass were $15\mum\; wide,\; 14\mum\; thick\; and \; 500\mum$ long. The fabricated comb actuator had resonant frequency ay 1430Hz, which was calculated to be 1441Hz. The proposed fabrication process can be applicable to the fabrication of a high-aspect-ratio comb actuator for a large displacement actuator and precision sensors. Moreover, this combined process enables to fabricate a more complex structure which cannot be fabricate only by surface or bulk micromachining.