• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.803-810
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• 2009

Micromirrors have a wide range of applications such as optical switches, laser scanners, and digital projection displays. Due to their low performances and high costs, however, practical applications of micromirrors are quite limited. At present micromirrors demand not only a better design but also a simple fabrication process. In this study a twisting-type micromirror that can be driven by two thermal bimorph actuators bending in opposite directions is designed from electro-thermo-mechanical theories and fabricated through a simple MEMS process. Each actuator consists of $SiO_2$ and gold thin-film layers. Simplified analytical model has been built to optimize the performance of micromirror. Due to unexpected resistance increase of metal film and alignment mismatch during fabrication process, experimental rotation angles of micromirrors are about $11^{\circ}$ at applied voltages less than 0.6V. From numerical simulation and analytical studies, however, the next design can provide rotation angles over $20^{\circ}$ at the same applied voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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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.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.11
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• pp.1-5
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• 2010

We developed a novel micro-electro mechanical systems (MEMS) test socket using silicon on insulator (SOI) substrate with the cantilever array structure. We designed the round shaped cantilevers with the maximum length of $350{\mu}m$, the maximum width of $200{\mu}m$ and the thickness of $10{\mu}m$ for $650{\mu}m$ pitch for 8 mm x 8 mm area and 121 balls square ball grid array (BGA) packages. The MEMS test socket was fabricated by MEMS technology using metal lift off process and deep reactive ion etching (DRIE) silicon etcher and so on. The MEMS test socket has a simple structure, low production cost, fine pitch, high pin count and rapid prototyping. We verified the performances of the MEMS test sockets such as deflection as a function of the applied force, path resistance between the cantilever and the metal pad and the contact resistance. Fabricated cantilever has 1.3 gf (gram force) at $90{\mu}m$ deflection. Total path resistance was less than $17{\Omega}$. The contact resistance was approximately from 0.7 to $0.75{\Omega}$ for all cantilevers. Therefore the test socket is suitable for BGA integrated circuit (IC) packages tests.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.871-874
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• 2004

Fabrication of a high-resolution shadow mask, or called nanostencil, is presented. This high-resolution shadowmask is fabricated by a combination of MEMS processes and focused ion beam (FIB) milling. 500 nm thick and 2x2 mm large membranes are made on a silicon wafer by micro-fabrication processes of LPCVD, photolithography, ICP etching and bulk silicon etching. Subsequent FIB milling enabled local membrane thinning and aperture making into the thinned silicon nitride membrane. Due to high resolution of FIB milling process, nanoscale apertures down to 70 nm could be made into the membrane.

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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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.

• Journal of the Korean institute of surface engineering
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• v.47 no.6
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• pp.362-367
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• 2014

We report the design, fabrication of a $Si_3N_4$ probe and calculation of its mechanical properties for DPN(dip pen nanolithography), which consists of dual tips. Concept of dual tip probe is to employ individual tips on probe as either an AFM tip for imaging or a writing tip for nano patterning. For this, the dual tip probe is fabricated using low residual stress $Si_3N_4$ material with LPCVD deposition and MEMS fabrication process. On the basis of FEM analysis we show that the functionality of dual tip probe for imaging is dependent on the dimensions of dual tip probe, and high ratio of widths of beam areas is preferred to minimize curvature variation on probe.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.197-205
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• 2005

Development of the packaging is one of the critical issues for commercialization of the RF-MEMS devices. RF MEMS package should be designed to have small size, hermetic protection, good RF performance and high reliability. In addition, packaging should be conducted at sufficiently low temperature. In this paper, a low temperature hermetic wafer level packaging scheme for the RF-MEMS devices is presented. For hermetic sealing, Au-Sn eutectic bonding technology at the temperature below $300{\times}C$ is used. Au-Sn multilayer metallization with a square loop of $70{\mu}m$ in width is performed. The electrical feed-through is achieved by the vertical through-hole via filled with electroplated Cu. The size of the MEMS Package is $1mm\times1mm\times700{\mu}m$. By applying $O_2$ plasma ashing and fabrication process optimization, we can achieve the void-free structure within the bonding interface as well as via hole. The shear strength and hermeticity of the package satisfy the requirements of MIL-STD-883F. Any organic gases or contamination are not observed inside the package. The total insertion loss for the packaging is 0.075 dB at 2 GHz. Furthermore, the robustness of the package is demonstrated by observing no performance degradation and physical damage of the package after several reliability tests.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.4
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• pp.149-154
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• 2004

This paper presents a silicon probe tip for vertical probe card application. The silicon probe tip was fabricated using MEMS technology such as porous silicon micromachining and deep- RIE (reactive ion etching). The thickness of the silicon epitaxial layers was 5 ${\mu}{\textrm}{m}$ and 7 ${\mu}{\textrm}{m}$, respectively. The width and length were 40 ${\mu}{\textrm}{m}$ and 600 ${\mu}{\textrm}{m}$, respectively. The probe structure was a multilayered structure and was composed of Au/Ni-Cr/Si$_3$N$_4$/n-epi layers. The height of the curled probe tip was measured as a function of the annealing temperature and time. Resistance characteristics of the probe tip were measured using a touchdown test.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.1
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• pp.11-16
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• 2005

This paper presents fabrication process and experimental results of two different types of flexible MEMS biosensors based on polymer/metal multilayer processing techniques. One type of a biosensor is a microelectrode array (MEA) for nerve signal monitoring through implanting the MEA into a living body, and another is a tactile sensor capable of being mounted on an arbitrary-shaped surface. The microelectrode array was fabricated and its electrical characteristics have been examined through in vivo and in vitro experiment. For sensitive skin, flexible tactile sensor array was fabricated and its sensitivity has been analyzed. Mechanical flexibility of these biosensors has been achieved by using a polymer, and it is verified by implanting a MEA to an animal and mounting the tactile sensor on an arbitrary-shaped surface.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.601-606
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• 2016

In this paper, an energy harvester is developed that has advantages regarding piezoelectric noise minimization, mass production, and an easily available environmental energy source, electromagnetic induction, as well as low-frequency bandwidth and high amplitude. A process for fabricating a three-dimensional multilayered planar coil using micro-electro-mechanical systems (MEMS) on a flexible printed circuit board FPCB is introduced. Optimal shape and size were calculated via internal resistance and inductance, and a prototype was fabricated through the MEMS procedure while considering the possibility of mass production. Although the internal resistance matched the designed value, the electromotive force generated did not reach the intended amount. The main reason for the decrease in efficiency was the low area of coil outskirt exposed to the magnetic field while there was relative motion between the magnet and the coil.