• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.98-105
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• 2000

The projectors using liquid crystal display(LCD) have faults such as low optical efficiency, low brightness and even heat generation. To solve these problems reflective-type spatial light modulators based on MEMS (Microelectromechanical Systems) technology have emerged. Digital Micromirror DeviceTM(DMDTM), which was already developed by Texas Instruments Inc., and Thin-film Micromirror ArrayTM(TMATM), which has been recently developed by Daewoo Electronics Co., are the representative examples. The display using TMATM has particularly much higher optical efficiency than other projectors. But the micromirrors manufactured by semiconductor processes have inevitable distortion because of the limitations of the manufacturing processes, so that the distortions of their surfaces have great influence on the optical efficiency of the projector. This study investigated the effects of mirror flatness on the optical performance, including the optical efficiency, of the TMATM projector. That is to say, as a part of the efforts to enhance the performance of the TMATM projector, how much influence the form errors of a micromirror surface exert on the optical efficiency and the modulation of gray scale of the projector were analyzed through a pertinent modeling and simulations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.10
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• pp.859-864
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• 2000

Recently IR detecting devices using MEMS have been actively studied. Microbolometer, one of these devices, detects the change of resistivity as the change of temperature of the device by absorbing IR, IR absorbing materials for microbolometer should have high TCR value and low noise characteristics which depends on resistivity. We fabricated multi-layer VOx thin films to improve the IR detectivity of uncooled IR devices and analyzed IR absorbing characteristics. We fabricated multi-layer VOx thin films by RF reactive sputtering method on SiNx substrate and changed characteristics using the different thickness of V and V$_2$O$\_$5/ thin films. Then we annealed them under 300$\^{C}$. The TCR (Temperature Coefficient of Resistance) measurement was carried out to estimate the IR detectivity of multi-layer VOx thin films. XRD (X-Ray Diffraction) analysis was carried out to estimate the IR detectivity of multi-layer VOx thin films. ZXRD (X-Ray Diffraction) analysis was used to find out phases and structures of V and V$_2$O$\_$5/ thin films. AES (Auger Electron Spectroscopy) analysis was used to find out composition of multi-layer VOx thin films before and after annealing. We obtained the optimum thickness range of V and V$_2$O$\_$5/ thin films from the result of AES analysis. We changed the thickness of V$_2$O$\_$5/ about 20 to 150 $\AA$ and thickness of V about 10 to 20 $\AA$. As the result of this, TCR value of multi-layer VOx thin films was about -2%/k and the resistivity was ∼1Ωcm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1133-1137
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• 2011

A novel technique for the fabrication of a glass micropipette-based thermal sensor was developed utilizing inexpensive thermocouple materials. Thermal fluctuation with a resolution of ${\pm}0.002$ K was measured using the fabricated thermal probe. The sensors comprise unleaded low-melting point solder alloy (Sn) as a core metal inside a borosilicate glass pipette coated with a thin film of Ni, creating a thermocouple junction at the tip. The sensor was calibrated using a thermally insulated calibration chamber, the temperature of which can be controlled with a precision of ${\pm}0.1$ K and the thermoelectric power (Seebeck coefficient) of the sensor was recorded from 8.46 to $8.86{\mu}V$/K. The sensor we have produced is both cost-effective and reliable for thermal conductivity measurements of micro-electromechanical systems (MEMS) and biological temperature sensing at the micron level.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.631-634
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• 2009

Recent advances in wireless communication, electronics, MEMS device, sensor and battery technology have made it possible to manufacture low-cost, low-power, multi-function tiny sensor nodes. A large number of tiny sensor nodes form sensor network through wireless communication. Sensor networks represent a significant improvement over traditional sensors, research on Zigbee wireless image transmission has been a topic in industrial and scientific fields. In this paper, we design a Zigbee wireless image sensor node and multimedia monitoring server system. It consists of embedded processor, memory, CMOS image sensor, image acquisition and processing unit, Zigbee RF module, power supply unit and remote monitoring server system. In the future, we will further improve our Zigbee wireless image sensor node and monitoring server system. Besides, energy-efficient Zigbee wireless image transmission protocol and interworking with mobile network will be our work focus.

• Journal of Information Display
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• v.8 no.2
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• pp.10-14
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• 2007

A blazed $GxL^{TM}$ device is described as having high optical efficiency (> 70% for RGB lasers), and high contrast ratio (> 10,000:1), and that is highly reliable when used in a large-area laser projection system. It has a robust design and precise stress control technology to maintain a uniform shape (bow and tilt) of more than 6,000 ribbons, a $0.25-{\mu}m$ CMOS compatible fabrication processing and planarization techniques to reduce fluctuation of the ribbons, and a reliable Al-Cu reflective film that provided protection against a high-power laser. No degradation in characteristics of the GxL device is observed after operating a 5,000- lumen projector for 2,000 hours and conducting 2,000 temperature cycling tests at $-20^{\circ}C$ and $+80^{\circ}C$. At the 2005 World Exposition in Aichi, Japan the world's largest laser projection screen with a size of 2005 inches (10 m ${\times}$ 50 m) and 6 million pixels (1,080 ${\times}$ 5,760) was demonstrated.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.657-661
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• 2003

The elastic moduli or fracture strengths of multi-layered film (SiO$_2$/po1y-Si/SiN/SiO$_2$, 2.77 $\mu\textrm{m}$ thick), CVD diamond film (1.6 $\mu\textrm{m}$ thick), SiO$_2$ film (1.0 $\mu\textrm{m}$ thick) and SiN film (0.43 $\mu\textrm{m}$ thick) made for the membrane of ink-jet printer head were measured with cantilever beam bending method using nanoindenter after fabricating in the form of micro cantilever beam (${\mu}$-CLB). And the elastic moduli of ${\mu}$-CLB of SiO$_2$ film and SiN film were compared with the value of each film on silicon substrate determined with nanoindentation method. The results showed that the modulus and strength of multi-layered film decrease from 68.08 ㎬ and 2.495 ㎬ to 56.53 ㎬ and 1.834 ㎬, respectively as the width of CLB increases from 18.5 $\mu\textrm{m}$ to 58.5 $\mu\textrm{m}$. And the elastic moduli of SiO$_2$ and SiN films measured with ${\mu}$-CLB bending method are 68.16 ㎬ and 215.45 ㎬, respectively and the elastic moduli of these films on silicon substrate measured with nanoindentation method are 98.78 ㎬ and 219.38 ㎬, respectively. These results show that with ${\mu}$-CLB bending technique, moduli can be measured to within 2%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.2
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• pp.397-407
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• 2015

In this paper, we designed 1 chip IC for 3-axis gyroscope and 3-axis accelerometer used for various IoT/M2M mobile devices such as smartphone, wearable device and etc. We especially focused on analysis of gyroscope noise and proposed new architecture for removing various noise generated by gyroscope MEMS and IC. Gyroscope, accelerometer and geo-magnetic sensors are usually used to detect user motion or to estimate moving distance, direction and relative position. It is very important element to designing a low noise IC because very small amount of noise may be accumulated and affect the estimated position or direction. We made a mathematical model of a gyroscope sensor, analyzed the frequency characteristics of MEMS and circuit, designed a low noise, compact and low power 1 chip 6-axis inertial sensor IC including 3-axis gyroscope and 3-axis accelerometer. As a result, designed IC has 0.01dps/${\sqrt{Hz}}$ of gyroscope sensor noise density.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.171-176
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• 2000

The physical and electrical characteristics of MgO and Pt thin-films on it, deposited by reactive sputtering and rf magnetron sputtering, respectively, were analyzed with annealing temperature and time by four-point probe, SEM and XRD. Under annealing conditions of $1000^{\circ}C$ and 2 hr, MgO thin-film had the properties of improving Pt adhesion to $SiO_2$ and insulation without chemical reaction to Pt thin-film, and the sheet resistivity and the resistivity of Pt thin-film deposited on it were $0.1288\;{\Omega}/{\square}$ and $12.88\;{\mu}{\Omega}{\cdot}cm$, respectively. We made Pt resistance pattern on $SiO_2$/Si substrate by lift-off method and fabricated thin-film type Pt-RTD(resistance thermometer device) for micro thermal sensors by Pt-wire, Pt-paste and SOG(spin-on-glass). In the temperature range of $25{\sim}400^{\circ}C$, the TCR value of fabricated Pt-RTD with thickness of $1.0{\mu}m$ was $3927\;ppm/^{\circ}C$ close to the Pt bulk value. Resistance values were varied linearly within the range of measurement temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.918-924
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• 2009

In this paper, we designed micro-structured electromagnetic transducers for energy harvesting and verified the performance of proposed transducers using finite element analysis software, COMSOL Multiphysics. To achieve higher energy transduce efficiency, around the magnetic core material, three-dimensional micro-coil structures with high number of turns are fabricated using semiconductor fabrication process technologies. To find relations between device size and energy transduce efficiency, generated electrical power values of seven different sizes of transducers ($3{\times}3\;mm^2$, $6{\times}6\;mm^2$, $9{\times}9\;mm^2$, $12{\times}12\;mm^2$, $15{\times}15\;mm^2$, $18{\times}18\;mm^2$, and $21{\times}21\;mm^2$) are analyzed on various magnetic flux density environment ranging from 0.84 T to 1.54 T and it showed that size of $15{\times}15\;mm^2$ device can generate $991.5\;{\mu}W$ at the 8 Hz of environmental kinetic energy. Compare to other electromagnetic energy harvesters, proposed system showed competitive performance in terms of power generation, operation bandwidth and size. Since proposed system can generate electric power at very low frequency of kinetic energy from typical life environment including walking and body movement, it is expected that proposed system can be effectively applied to various pervasive computing applications including power source of embodied medical equipment, power source of RFID sensors and etc. as an secondary power sources.

• Journal of Magnetics
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• v.10 no.3
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• pp.122-127
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• 2005

New classes of LC resonators for micro magnetic sensor device were proposed and fabricated. The first type LC resonator (Type I) consists of a small piece of microwire and two cylindrical electrodes at the end of the microwire without direct contact to its ferromagnetic core. In type I resonator the ferromagnetic core of the microwire and cylindrical electrodes act as an inductor and two capacitors respectively to form a LC circuit. The second type LC resonator (Type II) consists of a solenoidal micro-inductor with a bundle of soft magnetic microwires as a core. The solenoidal micro-inductors fabricated by MEMS technique were $500\sim1,000\;\mu{m}$ in length with $10\sim20$ turns. A capacitor is connected in parallel to the micro-inductor to form a LC circuit. A tiny glass coated $CO_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire was fabricated by a glass-coated melt spinning technique. A supergiant magneto-impedance effect was found in a type I resonator as much as 400,000% by precise tuning frequency at around 518.51 MHz. In type II resonator the changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. The phase angle between current and voltage was also strongly dependent on the magnetic field. The drastic increments of magnetoimpedance at near the resonance frequency were observed in both types of LC resonators. Accordingly, the sudden change of the phase angle, as large as $180^{\circ}C$, evidenced the occurrence of the resonance at a given external magnetic field.