• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.156-159
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• 2002

Film Bulk Acoustic wave Resonator (FBAR) using thin piezoelectric films can be fabricated as monolithic integrated devices with compatibility to semiconductor process, leading to small size, low cost and high Q RF circuit elements with wide applications in communications area. This paper presents a MMIC compatible Suspended FBAR using surface micromachining. It is possible to make Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$membrane by using surface micromachining and its good effect is to remove the substrate silicon loss. FBAR was made on 2$\mu\textrm{m}$ multi-layered membrane using CVD process. According to our result, Fabricated film bulk acoustic wave resonator has two adventages. First, in the respect of device Process, our Process of the resonator using surface micromachining is very simple better than that of resonator using bull micromachining. Second, because of using the multiple layer, thermal expansion coefficient is compensated, so, the stress of thin film is reduced.

• 정보저장시스템학회논문집
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• 제1권2호
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• pp.175-181
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• 2005

SiOB is an essential part of slim optical pickup, where the silicon mirror, LD stand, silicon PD are integrated and LD is flip chip bonded. SiOB is fabricated with bulk micromachining. Especially the fabrication of silicon wafer with stepped concave areas has many extraordinary difficulties. As a matter of fact, experiences and knowledges are rare in the fabrication of the highly stepped silicon wafer. The difficulties occurring in the integration of PD and SiOB, and highly stepped patterning, and silicon mirror roughness and how-to-solve will be discussed.

• 한국정밀공학회지
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• 제23권2호
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• pp.146-153
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• 2006

Acceleration sensors have widely been used in the various fields of industry. In recent years, micromachining accelerometers have been developed and commercialized by the micromachining technique or MEMS technique. Typical structure of such sensors consist of a cantilever beam and a vibrating mass fabricated on Si wafers using etching. This study investigates the feasibility of powder blasting technique for microfabrication of sensor structures made of the pyrex glass alternating the existing Si based acceleration sensor. First, as preliminary experiment, effect of blasting pressure, mass flow rate of abrasive and no. of nozzle scanning on erosion depth of pyrex and soda lime glass is studied. Then the optimal blasting conditions are chosen for pyrex sensor. Structure dimensions of designed glass sensor are 2.9mm and 0.7mm for the cantilever beam length and width and 1.7mm for the side of square mass. Mask material is from aluminium sheet of 0.5mm in thickness. Machining results showed that tolerance errors of basic dimensions of glass sensor ranged from 3um in minimum to 20um in maximum. This results imply the powder blasting can be applied for micromachining of glass acceleration sensors alternating the exiting Si based sensors.

• 한국레이저가공학회지
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• 제11권1호
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• pp.12-18
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• 2008

Laser micromachining is a promising technique to fabricate the micro-scale devices. However, there remains important challenges to reducethe redeposition of ablated materials around the laser irradiated zone and to get a smooth surface, especially for metal and semiconductor materials. To achieve the high-quality micromachined devices, various methods have been developed. Liquid-assisted micromachining can be a good solution to overcome the previously mentioned problems. During the laser ablation process, the liquid around the solid sample dramatically changes the ablation characteristics, such as ablation rate, surface profile, formation of debris, and so on. In this investigation, we conducted the laser micromachining of Si in various liquid environmental conditions, such as liquid types, liquid thickness. In addition, using nanoscale time-resolved shadowgraphy technique, we observed the ablation process in liquid environments to understand the mechanism of liquid-assisted laser micromachining.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.725-730
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• 1996

The key process in silicon surface micromachining is the selective etching of a sacrificial layer to release the silicon microstructure. The newly developed anhydrous HF/$CH_3$OH gas phase etching of TEOS (teraethylorthosilicate) sacrificial layers onto the polysilicon and the nitride substrates was employed to release the polysilicon microstructures. A residual product after TEOS etching onto the nitride substrate was observed on the surface, since a SiOxNy layer is formed on the TEOS/nitride interface. The polysilicon microstructures are stuck to the underlying substrate because SiOxNy layer does not vaporize. We found that the only sacrificial etching without any residual product and stiction is TEOS etching onto the polysilicon substrate.

• 마이크로전자및패키징학회지
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• 제6권1호
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• pp.81-89
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• 1999

Micromachining을 이용하여 기존의 전자 물품 감시에 사용되는 자기공명센서의 소형화 공정을 연구하였다. 설계 한 구조는 Free Standing Membrane형 과 Diving Board형의 두 가지이며 각자에 대해 적합한 공정 조건을 수립하고 실제로 그 구조를 형성해 보았다. 멤브레인형의 경우는 센서 모양을 여러 가지 형태로 쉽게 바꿀 수 있는 반면에 그 크기가 실리콘 기판의 두께에 의존하여 소형화하는데 한계가 있었으며 다이빙 보드형의 경우 소형화에도 유리하고 센서의 자기변형이 보다 자유로운 구조였다. 실리콘 질화막은 일반 반도체 공정에서의 조건보다 Si의 함량을 크게 하여 열처리 없이도 저응력의 박막형성이 가능하였으며 탄성계수 값이 크지 않아 센서 부분의 자기변형을 크게 구속하지 않아 센서물질의 지지층으로 유리한 물질이었다. 또한 스퍼터링으로 증착된 텅스텐은 자성 센서 물질로 연구되고 있는 Fe-B-Si물질에 대한 식각 선택도가 높아 구조 형성 공정 중 보호 층으로 사용된 후 제거될 수 있음을 알 수 있었다. 따라서 지지층으로 실리콘 질화막을 사용하고 보호층으로 텅스텐 박막을 사용한 다이빙 보드형 구조가 전자 물품 감시(EAS)용 센서의 소형화에 유리 할 것으로 생각된다.

• 센서학회지
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• 제5권1호
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• pp.71-77
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• 1996

마이크로머시닝의 구조재료인 다결정 Si이 희생산화막의 영향을 받음을 고려하여 다결정 Si을 열산화시킨 다결정-산화막을 새로운 희생산화막의 재료로서 제안하고 평가하였다. 다결정-산화막상에 성장시킨 다결정 Si은 통상의 희생산화막상에 성장시키는 경우보다 grain size가 증가하였고, XRD결과를 통해 (111) texture의 증가와, 부가적인 (220) texture가 형성됨을 관찰하였다. 또한, 다결정-산화막상에 성장시킨 다결정 Si의 경우, 그 응력이 작고 균일한 분포를 나타내었다.

• 한국전기전자재료학회논문지
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• 제15권11호
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• pp.958-962
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• 2002

This paper reports on the fabrication of free-standing microstructures by DRIE (deep reactive ion etching). SOI (Si-on-insulator) structures with buried cavities are fabricated by SDB (Si-wafer direct bonding) technology and electrochemical etch-stop. The cavity was formed the upper handling wafer by Si anisotropic etch technique. SDB process was performed to seal the formed cavity under vacuum condition at -760 mmHg. In the SDB process, captured air and moisture inside of the cavities were removed by making channels towards outside. After annealing (100$0^{\circ}C$, 60 min.), the SDB SOI structure with a accurate thickness and a good roughness was thinned by electrochemical etch-stop in TMAH solution. Finally, it was fabricated free-standing microstructures by DRIE. This result indicates that the fabrication technology of free-standing microstructures by combination SDB, electrochemical etch-stop and DRIE provides a powerful and versatile alternative process for high-performance bulk micromachining in MEMS fields.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권6호
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• pp.303-306
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• 2001

STFR were fabricated on the floating membrane which was formed by SOI-micromachining process. The floating membranes having a thickness range of $3{\sim}15{\mu}m$ could be simply formed by micromachining the directly-bonded and thinned SOI substrate. The STFR device fabricated on the $15{\mu}m$-thick membrane showed resonance frequency of fr = 1.65 GHz, coupling coefficient of Keff2 = 2.4 %, and series and parallel quality factors of Qs = 91.7 and Qp = 87.7, respectively.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권12호
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• pp.597-600
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• 2002

Film Bulk Acoustic wave Resonator (FBAR) using thin piezoelectric films can be made as monolithic integrated devices with compatibility to semiconductor process, leading to small size and low cost, high Q RF circuit elements with wide applications in communications area. This paper presents a MMIC compatible suspended FBAR using surface micromachining. Membrane is composed $Si_3N_4SiO_2Si _3N_4$ multi layer and air gap is about 50${\mu}{\textrm}{m}$. Firstly, We perform one dimensional simulation applying transmission line theorem to verify resonance characteristic of the FBAR. Process of the FBAR is used MEMS technology. Fabricated FBAR resonate at 2.4GHz, $K^2_{eff}$ and Q are 4.1% and 1100.