• 한국정밀공학회지
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• 제23권10호
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• pp.103-112
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• 2006

This paper describes a theoretical analysis and experimental verification on the performances of a vacuum-compatible air bearing, which is designed with a cascaded exhaust scheme to minimize the air leakage in a vacuum environment. The design of the vacuum-compatible air bearing equipped with the differential exhaust system requires great care because several design parameters, such as the number of exhaust stages, diameter of exhaust tube, pumping speed of a vacuum pump, and bearing clearance greatly influence the air leakage and thus degree of vacuum. In this study, a performance analysis method was proposed to estimate the performances of the air bearing, such as load capacity, stiffness, and air leakage. Results indicate that the load capacity and stiffness of the air bearing was improved as its boundary pressure, which was determined by the $1^{st}$ exhaust method, was lowered, and the dominant factors on the chamber's degree of vacuum were the number of exhaust stages, exhaust tube diameter and bearing clearance. A vacuum chamber and air bearing stage using porous pad were fabricated to verify the theoretical analysis. The results demonstrate that chamber pressure up to an order of $10^{-3}$ Pa was achieved with the air bearing stage operating inside the chamber, and this analysis method was valid by comparing predicted values with experimental data, for the mass flow rates from the porous pad, and pressures at each exhaust port and chamber, respectively.

• 반도체디스플레이기술학회지
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• 제8권2호
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• pp.31-35
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• 2009

In the silicon wafer polishing process, the mounting stage of silicon wafer on the ceramic carrier block has been using the polishing template which utilizes the porous surface instead of traditional wax mounting method. Here in this article, the experimental study is carried out in order to study the wafer demounting by water jet and the effects of operating conditions such as the water jet flowrate and the number of water jet nozzles on the wafer demounting time. It is found that the measured wafer demounting time is inversely proportional to the water flowrate per nozzle, regardless of number of nozzles used; implying that the stagnation pressure by the water jet impingement is the dominant key factor. Additionally, by using the transparent disk instead of wafer, the air bubble formation and growth is observed under the disk, making the passage of water flow, and subsequently demounting the wafer from the porous pad.

• 한국분말재료학회지
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• 제18권2호
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• pp.112-121
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• 2011

This study investigated the effect of solvent on the fabrication of Ni-free Fe-based alloy nano powders by employing the PWE (pulsed wire evaporation) in liquid and compared the alloy particles fabricated by three different methods (PWE in liquid, PWE in Ar, plasma arc discharge), for high temperature oxidation-resistant metallic porous body for high temperature soot filter system. Three different solvents (ethanol, acetone, distilled water) of liquid were adapted in PWE in liquid process, while X-ray diffraction (XRD), field emission scanning microscope (FE-SEM), and transmission electron microscope (TEM) were used to investigate the characteristics of the Fe-Cr-Al nano powders. The alloy powder synthesized by PWE in ethanol has good particle size and no surface oxidation compared to that of distilled water. Since the Fe-based alloy powders, which were fabricated by PWE in Ar and PAD process, showed surface oxidation by TEM analysis, the PWE in ethanol is the best way to fabricate Fe-based alloy nano powder.

• 분석과학
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• 제25권3호
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• pp.164-170
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• 2012

시아노아크릴레이트 훈증법은 비다공성 표면에 유류된 잠재지문을 현출할 때 효과적이다. 본 연구는, 진공챔버에서 시아노아크릴레이트를 훈증할 때 온도, 습도, 훈증 방법 등이 잠재지문 현출에 미치는 영향을 확인한 후 최적 반응 조건을 찾는데 있다. 진공챔버의 온도가 높을수록 시아노아크릴레이트 증발량은 증가했지만, 지문 융선에서 시아노아크릴레이트의 중합반응은 $30^{\circ}C$에서 가장 잘 일어났다. 상대습도가 40%, 50% 조건에서는 좋은 상태의 지문이 현출되었지만, 30%보다 낮거나 60%보다 높은 조건에서는 지문 융선에서 시아노아크릴레이트 중합반응 속도가 느려졌다. 진공챔버에서 시아노아크릴레이트를 자연적으로 증발시키는 방법보다는 $OMEGA-PRINT^{TM}$ dispersal pads와 수산화나트륨을 포함한 솜을 이용해 시아노아크릴레이트 훈증하는 방법이 효과적이란 사실을 확인할 수 있었다. 진공챔버에서 시아노아크릴레이트 처리시간은 상대습도에 비해 큰 영향을 주지 않았다.

• 대한두개안면성형외과학회지
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• 제17권4호
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• pp.218-221
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• 2016

Temporal hollowing is a common complication that occurs after coronal approach surgeries. However, temporal hollowing without previous nerve damage or trauma history is rare. Herein, we present a patient with cryptogenic temporal hollowing. A 22-year-old man without any history of craniofacial interventions or trauma presented with temporal hallowing. Magnetic resonance imaging revealed fatty degeneration of the left temporalis muscle. Electromyography and nerve conduction study showed no signs of neurologic abnormalities. The patient received autologous fat injection of 30 mL harvested from the left thigh using the modified Coleman technique. Temporal hollowing is commonly caused by atrophy of the superficial temporal fat pad. Its incidence is reported to be as high as 6% after coronal approach operation. Augmentation using porous hydroxyapatite or titanium mesh is a treatment option. Autologous fat graft can also be an option for mild to moderate temporal hollowing. In this case, a patient with no history of trauma, surgery, or myogenic disease developed temporal hollowing. Further study of the little-known cryptogenic form of temporal hollowing is warranted.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.78-78
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• 2007

In semiconductor devices, Cu has been used for the formation of multilevel metal interconnects by the damascene technique. Also lower dielectric constant materials is needed for the below 65 nm technology node. However, the low-k materials has porous structure and they can be easily damaged by high down pressure during conventional CMP. Also, Cu surface are vulnerable to have surface scratches by abrasive particles in CMP slurry. In order to overcome these technical difficulties in CMP, electro-chemical mechanical planarization (ECMP) has been introduced. ECMP uses abrasive free electrolyte, soft pad and low down-force. Especially, electrolyte is an important process factor in ECMP. The purpose of this study was to characterize KOH and $KNO_3$ based electrolytes on electro-chemical mechanical. planarization. Also, the effect of additives such as an organic acid and oxidizer on ECMP behavior was investigated. The removal rate and static etch rate were measured to evaluate the effect of electro chemical reaction.

• 센서학회지
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• 제5권5호
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• pp.21-29
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• 1996

(111), $n/n^{+}/n$ 3층 구조의 실리콘 기판을 HF 용액 내에서 양극반응시켜 선택확산된 $n^{+}$ 층에 다공질 실리콘층(Porous Silicon Layer : PSL)을 형성한 후, 이를 5% NaOH 수용액에서 식각하여 미세구조를 제조하는 다공질 실리콘 식각법을 이용한 실리콘 미세구조의 제조법으로 8개의 빔을 갖는 압저항형 실리콘 가속도센서를 제조하였다. 제조된 가속도센서의 매스 패드(mass pad)의 반경, 빔 길이, 빔 폭, 그리고 빔 두께는 각각 $700\;{\mu}m$, $50;{\mu}m$, $100\;{\mu}m$, $7\;{\mu}m$ 였다. 자동차의 응용을 위하여 50g 범위의 가속도를 측정할 수 있도록 진동질량은 2 mg으로 제조하였다. 이때, 진동질량을 부가하는 방법은 Pb/Sn/Ag 솔더 페이스트를 매스 패드에 디스펜싱한 후, 3-zone reflow 장치를 사용하여 열처리하였다. 제조된 가속도센서의 충격응답에 대한 감쇠시간은 약 30 ms로 나타났으며, 가산회로로 합한 출력의 감도는 2.9 mV/g이며, 비선형특성은 full scale 출력에서 2%이하로 측정되었다. 그리고 각 브릿지의 편차는 ${\pm}5%$ 미만으로 나타났다. 또한 측정된 타축감도는 약 4% 이하로 나타났으며, 시뮬레이션 결과로 부터 얻은 센서의 공진주파수는 2.15 KHz이었다.