• Journal of Sensor Science and Technology
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• v.17 no.6
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• pp.425-428
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• 2008

This paper describes the resonant characteristics of polycrystalline SiC micro resonators. The $1{\mu}m$ thick polycrystalline 3C-SiC cantilevers with different lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonance was measured by a laser vibrometer in vacuum at room temperature. For the $100{\sim}40{\mu}m$ long cantilevers, the fundamental frequency appeared at $147.2kHz{\sim}856.3kHz$. The $100{\mu}m$ and $80{\mu}m$ long cantilevers have second mode resonant frequency at 857.5.kHz and 1.14.MHz, respectively. Therefore, polycrystalline 3C-SiC resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.251-253
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• 2002

We have fabricated a novel Vertical Trench Hall-Effect Device sensitive to the magnetic field parallel to the sensor chip surface for non-contact angular position sensing applications. The Vertical Trench Hall-Effect Device is built on SOI wafer which is produced by silicon direct bonding technology using bulk micromachining, where buried $SiO_2$ layer and surround trench define active device volume. Sensitivity up to 150 V/AT is measured.

• Laser Solutions
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• v.6 no.3
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• pp.37-45
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• 2003

Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric pressure is studied with emphasis on the vaporization model, especially recondensation ratio over the Knudsen layer. Furthermore, parametric studies are carried out to analyze the effect of laser fluence and background pressure on surface ablation and the dynamics of ablation plume. In the numerical calculation, the temperature, pressure, density, and vaporization flux on a solid substrate are obtained by a heat-transfer computation code based on the enthalpy method. The plume dynamics is calculated considering the effect of mass diffusion into the ambient air and plasma shielding. To verify the computation results, experiments for measuring the propagation of a laser induced shock wave are conducted as well.

• 한국ITS학회:학술대회논문집
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• 2004.11a
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• pp.224-227
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• 2004

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.182-189
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• 2000

A micro-vacuum sensor was fabricated for the measurement of the vacuum level in micro-space. The fact that the field emission current was dependent on the environmental vacuum level was employed as an operating principle. The fabricated lateral-type field emitter triode with a cathode, a gate and a anode separated by using the surface micromachining process showed the emission current variation in the range of $1.20{\sim}2.42\;{\mu}A$ for the vacuum range of $10^{-5}{\sim}10^{-8}\;Torr$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.641-644
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• 2005

The study on the interaction forces of some biological materials is important to understanding biological phenomena and their application to practical purpose. This paper introduces a measuring technique for biological adhesive forces using the AFM(Atomic Force Microscope). Since no standardized thesis on adhesive forces exist, the adhesive forces is defined as adhesive forces against a hardened surface of biological materials. To grant the results are meaningful, which is based on the understanding the surface characteristics of biological materials using the AFM, a nominal value of average adhesive force per unit area should be measured. Therefore the modified AFM probe with small micro glass bead was proposed so that it can guarantee the required contact area for measuring the average adhesive forces. A pyrex glass substrate with circular patterns, which was fabricated by micromachining technique, is introduced in order to controll the contact area. The two types of mussel adhesive proteins, Celltak and recombinant-MGFP5, were tested by the proposed measuring method. The test results show that the adhesive force of the mussel adhesive proteins can be reliably measured by use of this method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.709-713
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• 2004

Characteristics of laser-assisted wet etching of titanium in phosphoric acid were investigated to examine the feasibility of this method for fabrication of high aspect ratio microchannels. Laser power, number of scans, etchant concentration, position of beam waist and scanning speed were taken into consideration as the major process parameters exerting the temperature distribution and the cross sectional profile of etched channels. Experimental results indicated that laser power influences on both etch width and depth while number of scans and scanning speed mainly affect on the etch depth. At a low etchant concentration, the cross sectional profile of an etched channel becomes a U-shape but it gradually turns into a V-shape as the concentration increases. On the other hand, surface of the laser beam focus with respect to the sample surface is found to be a key factor determining the bubble dynamics and thus the process stability. It is demonstrated that metallic microchannels with different cross sectional profiles can be fabricated by properly controlling the process parameters. Microchannels of aspect ratio up to 8 with the width and depth ranges of 8∼32 m and 50∼300 m, respectively, were fabricated.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.603-605
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• 1995

We present a novel method. to fabricate surface micromachined structures without their sticking on the substrate. An anhydrous HF/$CH_3OH$ vapor-phase etching (VPE) of sacrificial $SiO_2$ layers was employed to release 0.5-2 {\mu}m$ thick polysilicon cantilevers. The fabricated structures were observed using scanning electron microscope and 3-dimensional optical microscope. The results show that we can successfully make cantilever beams up to 1200{\mu}m$ long without sticking. Annealing effects on residual stress of polysilicon microstructures were also investigated. Anneal ins at 1100$^{\circ}C$ for 1 hour was found to be effective to release the residual stress of the polysilicon microstructures. These VPE and anneal ins techniques will be useful in surface micromachining technologies.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2230-2232
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• 2000

This paper reports an electrostatically driven and electromagnetically sensed planar vibratory gyroscope based on a surface-bulk combined micromachining. The fabricated structure has comb electrodes which are 400${\mu}m$ thick, 18${\mu}m$ wide, 600${\mu}m$ long and separated by 7${\mu}m$ so that the height-gap ratio is about 57. It also has electroplated gold springs which are 15${\mu}m$ wide, 14${\mu}m$ thick and 500${\mu}m$ long on both sides of the seismic mass. The open-loop characteristics of fabricated gyroscope at atmospheric pressure are measured on a rate table. The fabricated gyroscope has a sensitivity of 30mV/deg/sec, and a resolution of 0.1deg/sec at atmospheric pressure. It is expected that non linearity of full scale output is less than 0.8% with. the dynamic range of $\pm$500deg/sec.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.349-352
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• 2009

This paper describes the fabrication and characteristics of micro heaters built on AlN($0.1{\mu}m$)/3C-SiC($1{\mu}m$) suspended membranes by surface micromachining technology. In this work, 3C-SiC and AlN films are used for high temperature environments. Pt thin film was used as micro heaters and temperature sensor materials. The resistance of temperature sensor and the power consumption of micro heaters were measured and calculated. The heater is designed for operating temperature up to about $800^{\circ}C$ and can be operated at about $500^{\circ}C$ with a power of 312 mW. The thermal coefficient of the resistance(TCR) of fabricated Pt resistance of temperature detector(RTD)'s is 3174.64 ppm/$^{\circ}C$. A thermal distribution measured by IR thermovision is uniform on the membrane surface.