• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.2004-2006
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• 1996

A thermally driven polysilicon micro actuator has been fabricated using surface micromachining techniques. It consists of P-doped polysilicon as a structural layer and TEOS (tetracthylorthosilicate) as a sacrificial layer. The polysilicon was annealed for the relaxation of residual stress which is the main cause to its deformation such as bending and buckling. And the newly developed HF VPE (vapor phase etching) process was also used as an effective release method for the elimination of sacrificial TEOS layer. The thickneas of polysilicon is $2{\mu}m$ and the lengths of active and passive polysilicon cantilevers are $500{\mu}m$ and $260{\mu}m$, respectively. The actuation is incurred by die thermal expansion due to the current flow in the active polysilicon cantilever, which motion is amplified by lever mechanism. The moving distance of polysilicon micro actuator was experimentally conformed as large as $21{\mu}m$ at the input voltage level of 10V and 50Hz square wave. The actuating characteristics are investigated by simulating the phenomena of heat transfer and thermal expansion in the polysilicon layer. The displacement of actuator is analyzed to be proportional to the square of input voltage. These micro actuator technology can be utilized for the fabrication of MEMS (microelectromechanical system) such as micro relay, which requires large displacement or contact force but relatively slow response.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.109-110
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• 2006

In bio applications, high temperature coefficient of resistance (TCR) at $30^{\circ}C{\sim}40^{\circ}C$ is especially important for a temperature sensor. In this work, single phase-vanadium dioxide ($VO_2$) thin films for temperature sensor were fabricated by reactive DC magnetron sputtering and post-annealing method. VOx thin films deposited by reactive sputtering in a controlled $Ar/O_2$ atmosphere can be transformed into single phase-$VO_2$ films by post-annealing in $N_2$ atmosphere. The grown $VO_2$ thin films have a moderate resistance at room temperature and very high TCR at room temperature and transition temperature, respectively 2.88%/K and 15.8%/K. A detailed structural characterization is performed by SEM, XRD and RBS. SEM morphology image indicates that grains of fabricated $VO_2$films are homogeneous and ball-like in shape. A fact that the films contain only single phase-$VO_2$ is obtained by XRD and RBS analysis. After deposition, the sensors were fabricated by micromachining technology. Silicon nitride membrane and black nickel were used for a thermal isolation structure and absorption layer. In the vicinity of room temperature, the TCR of sensors was enough high to apply for bio sensors.

• Journal of Sensor Science and Technology
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• v.10 no.5
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• pp.304-313
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• 2001

In this research, we investigate wet-etching properties of GaAs in $NH_4OH-H_2O_2-H_2O$, and develop the fabrication method of GaAs microstructures with rectangular cross section using (001) GaAs substrate. For obtaining wet-etching properties with respect to crystallographic orientation, the etch rates and cross-section etch profiles of (001) GaAs with 16 different compositions and the undercut rates with 5 different compositions are measured using $NH_4OH-H_2O_2-H_2O$ mixed solutions. From these experimental data, a new GaAs micromachining method in bulk (001) GaAs is proposed, and used to fabricate a released microbridges with a rectangular cross section. The developed GaAs micromachining method can be very useful for low-loss, highly-tunable capacitors for RF components and for integration with GaAs optical components.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.20-23
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• 2003

Piezoelectric powder with the composition of PbTiO$_3$-PbZrO$_3$-Pb(Mn$\_$1/3/Nb$\_$2/3/)O$_3$ and small particle size of 0.3 $\mu\textrm{m}$ was investigated for low-temperature firing of PZT thick films. PbTiO$_3$-PbZrO$_3$-Pb(Mn$\_$1/3/Nb$\_$2/3)O$_3$ ceramics showed dense microstructure and superior piezoelectric properties, electromechanical coupling factor (k$\_$p/) of 0.501 and piezoelectric constant (d$\_$33/) of 224. The PZT paste was made of the powder and organic vehicles, and screen-printed on Pt(450nm)/YSZ(110nm)/SiO$_2$(300nm)/Si substrates and fired at 800∼900$^{\circ}C$. Any interface reaction between the PZT thick film and the bottom electrode was not observed in the PZT thick films. The PZT thick film fired at 800$^{\circ}C$ showed moderate electrical properties, the remanent polarization(p$\_$r/) of 16.0 ${\mu}$C/$\textrm{cm}^2$, the coercive field(E$\_$c/) of 36.7 ㎸/cm, and dielectric constant ($\varepsilon$$\_$r/) of 531. Low-temperature sinterable piezoelectric composition and high activity of fine particles reduced the sintering temperature of the thick film. This PZT thick film could be utilized for piezoelectric microactuators or microsensors that require Si micromachining technology.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2108-2110
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• 2004

In this paper, a novel tunable bandpass filter using tunable series inductors and MEMS switches for wireless LAN applications was proposed. The proposed tunable filter was fabricated using a micromachining technology and performances of the fabricated filter were estimated. The filter consists of spiral inductors, MIM capacitors and direct-contact type MEMS switches, and its frequency tunability is achieved by changing the inductance that is induced by ON/OFF actuations of the MEMS switches. The actuation voltage of the MEMS switches was 58 V, and the measured center frequencies were 2.55 GHz and 5.1 GHz, respectively. The passband insertion loss and 3-dB bandwidth were 4.2 dB and 22.5 % at 2.55 GHz, and 5.2 dB and 23.5 % at 5.1 GHz, respectively.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.106-109
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• 2012

A low power methane gas sensor with microheater was fabricated by silicon bulk micromachining technology. In order to heat up the sensing layer to operating temperature, a platinum (Pt) micro heater was embedded in the gas sensor. The line width and gap of the microheater was 20 ${\mu}m$ and 4.5 ${\mu}m$, respectively. Zinc oxide (ZnO) nanowhisker arrays were grown on a sensor from a ZnO seed layer using a hydrothermal method. A 200 ml aqueous solution of 0.1 mol zinc nitrate hexahydrate, 0.1 mol hexamethylenetetramine, and 0.02 mol polyethylenimine was used for growing ZnO nanowhiskers. Temperature distribution of the sensor was analyzed by infrared thermal camera. The optimum temperature for highest sensitivity was found to be $250^{\circ}C$ although relatively high (64%) sensitivity was obtained even at as low a temperature as $150^{\circ}C$. The power consumption was 72 mW at $250^{\circ}C$, and only 25 mW at $150^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1871-1876
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• 2004

We demonstrate a novel fabrication technology for the microneedle array that can be used in the medical test field, which is transdermal drug delivery and blood analyte sampling. Previous researchers have used silicon-processed micromachining, a reactive ion etching, and molding techniques for the fabrication of microneedle array. However, these fabrication techniques have somewhat limitations apply to the microneedle array fabrication according to its application. Inclined LIGA process is suggested to overcome these problems. This process provides easier, sharper and longer out-of-plane microneedle array structure than conventional silicon-processed fabrication method did. Additionally, because of the advantage of the LIGA process based on mold fabrication for mass production, the polymer, PMMA(PolyMethylMethAcrylate), based microneedle array is useful as the mold base of nickel electroplating process; on the other hand, silicon-processed microneedle array is used in itself. In this research, we fabricate different types of out-of-plane microneedle array, which have different shape of tip, base and hole structure, using the inclined LIGA process. The fabricated microneedles have proper mechanical strength, height and sharpness to puncture human hand epidermis or dermis with less pain and without needle tip break during penetrating the skin.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.42-47
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• 1998

We have fabricated electron-optical lens for micro E-beam system that can overcome the limitation of current E-beam lithography. Our electron-optical lens consists of multiple silicon electrodes which were fabricated by micromachining technology and assembled by anodic bonding. The assembled system was installed in UHV chamber to observe the emission characteristics of focused electrons by the electro-optical lens. We used STM(Scanning Tunneling Microscope) tip for electron source. By performing lithography with the focused electrons with PMMA(poly-methylmethacrylate) as E-beam resist. We could draw 0.13${\mu}{\textrm}{m}$ nano-scale lines.

• 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 $10^{-5}{\sim}10^{-8}\;Torr$.

• Journal of Sensor Science and Technology
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• v.12 no.1
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• pp.24-33
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• 2003

This research is about a comfort sensing system for human environmental monitoring using a one-bodied humidity and temperature sensor and an air flow sensor. The thermal comfort that a human being feels in indoor environment has been known to be influenced mostly by six parameters, i.e. air temperature, radiation, air flow, humidity, activity level and clothing thermal resistance. Considering an environmental monitoring, we have designed and fabricated a one-bodied humidity and temperature sensor and an air flow sensor that detect air relative humidity, temperature and air flow in human environment using surface micromachining technologies. Micro-controller calculates a PMV (predicted mean vote) and CSV (comfort sensing vote) with sensing signals and display a PMV on LCD (liquid crystal display) for human comfort on indoor climate. Our work has demonstrated that a comfort sensing system can provide an effective means of measuring and monitoring the indoor comfort sensing index of a human being. Experimental results with simulated environment clearly suggest that our comfort sensing system can be used in many applications such as air conditioning system, feedback controlling in automobile, home and hospital etc..