• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.13-19
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• 2009

A 440MHz wireless and passive surface acoustic wave (SAW) based chemical sensor was developed on a $41^{\circ}YX\;LiNbO_3$ piezoelectric substrate for simultaneous measurement of $CO_2$ gas and relative humidity (RH) using a reflective delay line pattern as the sensor element. The reflective delay line is composed of an interdigital transducer (IDT) and several shorted grating reflectors. A Teflon AF 2400 and a hydrophilic $SiO_2$ layer were used as $CO_2$ and water vapor sensitive films. The coupling of mode (COM) modeling was conducted to determine optimal device parameters prior to fabrication. According to simulation results, the device was fabricated and then wirelessly measured using the network analyzer. The measured reflective coefficient $S_{11}$ in the time domain showed high signal/noise (S/N) ratio, small signal attenuation, and few spurious peaks. In the $CO_2$ and humidity testing, high sensitivity ($2^{\circ}/ppm$ for $CO_2$ detection and $7.45^{\circ}/%$RH for humidity sensing), good linearity and repeatability were observed in the $CO_2$ concentration ranges of $75{\sim}375ppm$ and humidity levels of $20{\sim}80%$RH. Temperature and humidity compensations were also investigated during the sensitivity evaluation process.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.414-420
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• 1999

The oxide sacrificial layer technology is one of the key technologies in surface micromachining. However, the commonly used aqueous HF solutions, including the $NH_4F$ buffered HF solutions (BHF), are known to attack the Al metal layers during the oxide sacrificial etch. A mixed $NH_4F$/HF/glycerine aqueous solution of 4:1:2 ratio is known to have the best etch selectivity between oxide and AI, but even this sacrificial etchant has a significant etch rate for AI. This paper reports an extensive experimental study on various concentration ratios for HF, $NH_4F$ and glycerine, and develops the optimal mixture ratio for sacrificial etching. At the $NH_4F$/HF/glycerine ratio of 2:1:4, the etch selectivity between PSG and Al improves by approximately 6 times over the previously known best selectivity, to a value of 7,700. At this condition, the measured etch rate of PSG film is approximately $2.1\;{\mu}m/min$, which is sufficiently fast. The developed sacrificial etchant allows the addition of a Al metal layer in surface micromachining, without the worry of Al layer erosion during sacrificial etch.

• Journal of Sensor Science and Technology
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• v.6 no.5
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• pp.385-391
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• 1997

An objection of this study is to develop a measuring circuit of a gauge using radioisotope for compaction control. The gauge developed in this study makes use of radioisotope with the activity exempted from domestic atomic law and consists of measuring circuits for gamma-rays and thermal neutrons, a high voltage supply unit, and a microprocessor. To obtain meaningful numbers of pulse counts, parallel five and two circuits are provided for gamma-rays and thermal neutrons, respectively. Being simple in electrical characteristics of G-M detector for gamma-rays, pulses are counted through only a shaping circuit. Very small pulses generated from He- 3 proportional detector for thermal neutrons are amplified to the maximum of 50 [dB] and a window comparator accepts only pulses with meaning. To minimize effects of natural environmental radiation and electrical noise, circuits are electrostatically shielded and pulses made by ripples are eliminated by taking frequency of high voltage supplied to the circuit and pulse height of ripples into consideration. One-chip microprocessor is applied to process various counts, results are stored and the gauage is made capable to communicate with PC. Enough and meaningful numbers of pulses are counted with the prototype gauage for compaction control.

• Korean Journal of Optics and Photonics
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• v.30 no.2
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• pp.37-47
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• 2019

A reflecting omnidirectional optical system with four spherical and aspherical mirrors, for use with long-wavelength infrared light (LWIR) for night surveillance, is proposed. It is designed to include a collecting pseudo-Cassegrain reflector and an imaging inverse pseudo-Cassegrain reflector, and the design process and performance analysis is reported in detail. The half-field of view (HFOV) and F-number of this optical system are $40-110^{\circ}$ and 1.56, respectively. To use the LWIR imaging, the size of the image must be similar to that of the microbolometer sensor for LWIR. As a result, the size of the image must be $5.9mm{\times}5.9mm$ if possible. The image size ratio for an HFOV range of $40^{\circ}$ to $110^{\circ}$ after optimizing the design is 48.86%. At a spatial frequency of 20 lp/mm when the HFOV is $110^{\circ}$, the modulation transfer function (MTF) for LWIR is 0.381. Additionally, the cumulative probability of tolerance for the LWIR at a spatial frequency of 20 lp/mm is 99.75%. As a result of athermalization analysis in the temperature range of $-32^{\circ}C$ to $+55^{\circ}C$, we find that the secondary mirror of the inverse pseudo-Cassegrain reflector can function as a compensator, to alleviate MTF degradation with rising temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1254-1260
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• 2009

CDMA tele-Controller system is designed with a low power consumption 8 bit microcontroller, ATmega 2560. ATmega 2560 microcontroller consists of 4 UART (Universal asynchronous receiver/transmitter) ports, 4 kbytes EEPROM, 256 kbytes flash memory, 4 kbytes SRAM. 4 URAT is used for CDMA modem, communication for GPS module, EEPROM is used for saving a configuration for program running, a flash memory of 256 kbytes is used for storing a F/W(Firm Ware), and SRAM is used for stack, storing memory of global variables while program running. We have tested the communication distance between the coast station and sea by the fabricated control board using 800 MHz CDMA modem and GPS module, which is building for the navigational aid management system by remote control. As a results, the receiving signal strength is above -80 dBm, and then the characteristics of the control board implemented more than 10 km in the distance of the communication.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.781-784
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• 2005

Twenty four types of thermopile for micro spectrometer infrared sensors were fabricated on low-stress $Si_3N_4$ membranes with $1.2{\mu}m-thickness$ using MEMS technology. Poly-Si thin film with thickness of 3500 ${\AA}$ as the first thermocouple material, was deposited by LPCVD method. And aluminum thin film with thickness of 6000 ${\AA}$ as the second thermocouple material, was deposited by sputtering method. Thermopile were designed and fabricated for optimum conditions by five parameters of thermocouple numbers (16 ${\sim}$ 48), thermocouple line widths (10 ${\mu}m$ ${\sim}$ 25 ${\mu}m$), thermocouple lengths (100 ${\mu}m$ ${\sim}$ 500 ${\mu}m$), membrane areas ($1^2\;mm^2$ ${\sim}$ $2.5^2\;mm^2$) and junction areas (150 ${\mu}m^2$ ${\sim}$ 750 ${\mu}m^2$), respectively. Electromotive forces of fabricated thermopile were measured 1.1 mV ${\sim}$ 7.4 mV at $400^{\circ}C$. It was thought that measurement results could be used for thermopile infrared sensors optimum structure for micro spectrometers.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.1-9
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• 2010

Three-dimensional (3-D) integration is an emerging technology, which vertically stacks and interconnects multiple materials, technologies, and functional components such as processor, memory, sensors, logic, analog, and power ICs into one stacked chip to form highly integrated micro-nano systems. Since CMOS device scaling has stalled, 3D integration technology allows extending Moore's law to ever high density, higher functionality, higher performance, and more diversed materials and devices to be integrated with lower cost. The potential benefits of 3D integration can vary depending on approach; increased multifunctionality, increased performance, increased data bandwidth, reduced power, small form factor, reduced packaging volume, increased yield and reliability, flexible heterogeneous integration, and reduced overall costs. It is expected that the semiconductor industry's paradiam will be shift to a new industry-fusing technology era that will offer tremendous global opportunities for expanded use of 3D based technologies in highly integrated systems. Anticipated applications start with memory, handheld devices, and high-performance computers and extend to high-density multifunctional heterogeneous integration of IT-NT-BT systems. This paper attempts to introduce new 3D integration technologies of the chip self-assembling stacking and 3D heterogeneous opto-electronics integration for realizng the super-chip.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.150-150
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• 2016

디스플레이, 센서 등 전자소자는 소형화 단계를 지나 인체 부착형 소자로의 발전을 요구하고 있다. 부착형 소자에서는 접착력과 큰 마찰력이 필요하지만 마찰특성이 더 중요하므로 인체 및 물체의 마찰을 위해서는 다양한 표면에 대항하는 마찰 특성과 내구성이 요구되며 이를 위해 개코도마뱀 또는 딱정벌레, 말벌날개와 같은 자연모사형 건식 마찰 방식에 대한 연구가 활발히 진행되고 있다. 그러나 기존 폴리머를 이용하여 자연모사형 마이크로/나노 구조 형성은 기계적으로 가공된 금형 몰딩을 통한 매무 복잡한 공정을 요구된다. 본 연구에서는 이러한 복잡한 공정을 통한 마찰재 제작을 단순화하기 위해서 플라즈마 표면처리를 활용하여 나노구조 형성하는 방법을 소개하고자 하며, 건식 접착 및 마찰용 폴리머 소재(PDMS(Poly dimethyl siloxane))에 따른 표면구조 변화와 표면에너지 및 화학결합 변화에 대한 연구를 수행하였다. 플라즈마 표면처리를 위해서 자체 개발한 선형이온소스를 활용하였으며 입사에너지에 따라 표면형상 변화를 주사전자현미경을 활용하여 관찰하였다. 표면에너지 변화는 접촉각측정기를 활용하였으며, Tribology tester(Ball on disk)를 활용하여 마찰특성을 평가하였다. PDMS(Poly dimethyl siloxane)는 입사에너지가 증가함에 따라 주름형태 구조 크기가 증가하는 것을 관찰하였고, 플라즈마 처리를 통해 표면에너지 및 마찰력 증가를 관찰하였다. 그리고 플라즈마 처리 후 표면에너지 변화인 FOTS(Trichloro-(1H,1H,2H,2H- perfluorooctyl) silane) 처리를 통하여 표면에너지 감소와 마찰력이 절반으로 감소하였다. 본 연구 결과는 나노구조에 따라 표면형상 및 표면에너지 변화에 따른 PDMS의 마찰력 변화를 확인하였고, 이러한 특성을 활용하여 마찰재와 피부 부착형 접착 패치에 응용이 가능할 것으로 기대된다.

• Journal of the Korean Vacuum Society
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• v.16 no.1
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• pp.52-57
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• 2007

The interaction force between biomolecules(DNA-DNA, antigen-antibody, ligand-receptor, protein-protein) defines not only biomolecular function, but also their mechanical properties and hence bio-sensor. Atomic force microscopy(AFM) is nowadays frequently applied to determine interaction forces between biological molecules and biomolecular force measurements, obtained for example using AFM can provide valuable molecular-level information on the interactions between biomolecules. A proper modification of an AFM tip and/or a substrate with biomolecules permits the direct measurement of intermolecular interactions, such as DNA-DNA, protein-protein, and ligand-receptor, etc. and a microcantilever-based sensor appeared as a promising approach for ultra sensitive detection of biomolecular interactions.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.475-475
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• 2013

Cuprous oxide ($Cu_2O$)는 밴드갭이 2.17 eV p-type 산화물 반도체로써 태양에너지 변환기, photocatalysis (광촉매작용), 센서, 스위칭 메모리 등 응용이 다양한 재료이다. 산화물 반도체의 기본 특성은 나노/마이크로 범위 안에서 재료의 표면형태, 크기, 구조와 형상 공간방향등에 크게 영향을 받는다. 그렇기 때문에 원하는 $Cu_2O$ 특성을 얻기 위해서 성장 거동을 아는 것은 매우 중요하다. RF 마그네트론 스퍼터법으로 rod 성장 사례는 잘 알려지지 않았다. 그래서 RF 마그네트론 스퍼터법 $Cu_2O$ rod 형성 실험을 통하여 $Cu_2O$ 형성과 성장 거동을 알아보았다. RF 마그네트론 스퍼터법으로 $Cu_2O$ rod를 glass 기판 위에 Cu metal target을 이용하여 형성시켰다. $Cu_2O$ rod 합성을 위해 기판온도 및 산소분압 O2/(Ar+O2)=3%, 5%, 7% 증착시간 등을 변화시켜 실험하였다. 성장된 rod의 분석은 XRD, SEM으로 확인하였다. 성장 거동은 증착온도와 증착시간에 차이를 보였다. 증착온도 $550^{\circ}C$에서 rod가 생성되는 것을 관찰하였다. 증착시간이 길어질수록 rod 길이가 길어지고 일정 시간이 지나면 rod의 길이 성장보다는 두께(폭)가 성장하는 것을 확인하였다. 증착온도 $550^{\circ}C$ 그리고 산소분압 3%, 5%, 7% 조건에서 rod 합성 실험을 하였을 때 3%, 5% 조건에서 rod의 성장을 확인하였다. 이때 3%, 5% 산소분압에 따라 rod의 모양이 변화하였다. 하지만 7% 조건에서는 rod가 성장하지 않았다. 이유는 3%, 5%에서는 Cu metal peak을 확인하였지만, 7% 조건에서는 Cu metal peak이 없었다. 이로부터 Cu metal이 $Cu_2O$ rod 생성에 영향을 미치는 중요한 요소임을 예상할 수 있었다.