• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.56-56
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• 2003

최근 정보통신 분야의 급격한 발달로 인하여 무선통신에 사용되는 주파수 영역 또한 계속 높아짐에 따라 대역통과 필터 소자의 삽입 손실, 소비 전력, 크기, MMIC화에 대한 많은 연구가 진행되고 있다 압전 현상을 이용한 박막형 공진기가 이러한 요구를 충족시키고, 현재의 SAW filter를 대체할 소자로 떠오르고 있다. 본 실험에서는 단결정 미세 구조를 만들 수 있고, 압전 효과 또한 우수하며, Surface Micromachining보다 비교적 제조 공정이 간단하고 선택적 에칭이 가능한 Bulk Micromachining을 이용하여 Si$_3$N$_4$ Membrane을 이용한 중심주파수 5.2GHz인 두께 진동모드 Film Bulk Acoustic Wave Resonator(FBAR)를 제작하고 공진기의 고주파 특성을 평가하였다. Membrane구조 형성을 위해 Backside면인 Si$_3$N$_4$, Si은 RIE(Reactive Ion Etching)와 선택적 에칭용액인 KOH로 각각 에칭하여 Membrane을 갖는 구조로 중심주파수 5.2GHz인 두께 진동모드 FBAR를 설계 및 제조하였다. 체적 탄성파 공진 현상은 r.f Magnetron Sputtering법으로 증착한 AIN 압전박막과 Mo전극으로부터 발생 가능하였다. 본 연구에서는 0.9$\mu\textrm{m}$-Si$_3$N$_4$ Membrane을 이용해 FBAR를 제작/평가하고, RIE을 통해 Membrane을 제거해 가면서 공진기의 특성 즉, Quality factor와 유효전기기계결합계수(K$_{eff}$) 및 S parameter특성을 비교 측정해 보았다. 측정해본 결과 Membrane Free일때가 훨씬더 공진 특성이 우수함을 볼 수 있다

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.24-25
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• 2006

In this paper, ZnO thin films were prepared on p-Si(100) by RF magnetron sputtering. Before the depostion, the substrates were pre-heated to 500, 400, 300, $200^{\circ}C$ or not. During the deposition, the substrates were cooled down naturally or kept and then the films were investigated by XRD(X-ray diffraction) and SEM (scanning micro scope). It is showed the most outstanding result that the film was prepared on the substrate were cooled from $400^{\circ}C$. When the substrate was cooled from a certain temperature during deposition, it could be improve the c-axis orientation and useful for application of SAW(surface acoustic wave) filter and FBAR(film bulk acoustic wave resonator) device.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.362-367
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• 2005

Ultrasonic backward radiation profile is frequency-dependent when the incident region has deptional gradient of acoustical properties or multi-layers. Until now, we have measured the profiles of principal frequencies of an used transducers so that it was not easy to characterize the frequency dependence of the SAW(surface acoustic wave) from the backward radiation profile. We tried to measure the spectral backward radiation profiles using DFP(digital filer package) in a Lecroy DSO(digital storage oscilloscope). The measured spectral profiles showed that the steel specimen of #1200 surface treatment have 2% SAW velocity dispersion of the loaded case and the severly rusty steel specimen have the very big changes in the shape and pattern of the spectral profile. It is concluded that the spectral backward radiation profiles could be very effective tool to evaluate the frequency dependence of surface area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.9
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• pp.813-821
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• 2013

In this paper, a vital signal sensor based on impedance variation of resonator is presented. Proposed vital signal sensor can detect the vital signal, such as respiration and heart-beat signal. System is composed of resonator, oscillator, surface acoustic wave (SAW) filter, and power detector. The cyclical movement of a dielectric such as a human body, causes the impedance variation of resonator within the near-field range. So oscillator's oscillation frequency variation is effected on resonator's resonant frequency. SAW filter's skirt characteristic of frequency response can be transformed a small amount of frequency deviation to a large variation. Aim to enhance the existing sensor detection range, proposed sensor operates in 870 MHz ISM band, and detect respiration and heart-beat signal at distance of 120 mm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.103-107
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• 2003

The inductively coupled plasma(ICP) etching process was selected to fabricate RF Surface Acoustic Wave(SAW) filters and a Pt thin film was sputtered on a $LiTaO_3$ substrate applied to electrode materials to reduce the spurious response and improve the power durability. Steep sidewall pattern was achieved employing $C_4F_8/Ar/Cl_2$ gas chemistry. We investigated an etching mechanism and parameter dependence of the Pt thin film about $C_4F_8$ addition. Sidewall etch angle was about $80^{\circ}$ at the $C_4F_8$ 20% mixing ratio. Fabricated SAW filter is consists of some series and parallel arm SAW resonators which work as impedance elements and show capacitance characteristics at out of the passband. It can be modified for $800{\sim}900\;MHz$ RF filters. External matching circuits were unnecessary.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.112-112
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• 2009

In this study, the effect of a long post-deposition thermal annealing(600 and 1000 $^{\circ}C$) on the surface acoustic wave (SAW) properties of polycrystalline (poly) aluminum-nitride (AlN) thin films grown on a 3C-SiC buffer layer was investigates. The poly-AlN thin films with a (0002) preferred orientation were deposited on the substrates by using a pulsed reactive magnetron sputtering system. Experimental results show that the texture degree of AlN thin film was reduced along the increase in annealing temperature, which caused the decrease in the electromechanical coupling coefficient ($k^2$). The SAW velocity also was decreased slightly by the increase in root mean square (RMS) roughness over annealing temperature. However, the residual stress in films almost was not affect by thermal annealing process due to small lattice mismatch different and similar coefficient temperature expansion (CTE) between AlN and 3C-SiC. After the AlN film annealed at 1000 $^{\circ}C$, the insertion loss of an $IDT/AlN/3C-SiC/SiO_2/Si$ structure (-16.44 dB) was reduced by 8.79 dB in comparison with that of the as-deposited film (-25.23 dB). The improvement in the insertion loss of the film was fined according to the decrease in the grain size. The characteristics of AlN thin films were also evaluated using Fourier transform-infrared spectroscopy (FT-IR) spectra and X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.3
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• pp.1-7
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• 1999

A single RF transceiver evaluation board have been developed for the purpose of application to the 900MHz band transceiver contained RF-IC chip And environment test was evaluated. The RF-IC chipset includes LNA(Low Noise Amplifier), down-conversion mixer, AGC(Automatic Gain Controller), switched capacitor filter and down sampling mixer. The RF evaluation board for the testing of chipset contained various external matching circuits, filters such as RF/IF SAW(Surface Acoustic Wave) filter and duplexer and power supply circuits. With the range of 2.7~3.3V the operated chip revealed moderate power consumption of 42mA. The chip was well operated at the receiving frequency of 925~960MHz. Measurement result is similar to general RF receiving specification of the 900MHz digital mobile phone.

• Korean journal of food and cookery science
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• v.23 no.1 s.97
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• pp.99-106
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• 2007

This study investigated the effect of UV-B irradiation on the quality of Pleurotus ostreatus. The changes of vitamin $D_2$ contents, color value and flavor pattern in mushrooms were analyzed by high-performance liquid chromatography (HPLC), chromameter and gas chromatography - surface acoustic wave (GC-SAW) electronic nose. By exposure to UV-B irradiation (0 kj/m$^2$, 10 kj/m$^2$, 20 kj/m$^2$), vitamin $D_2$ content increased from 0 (control) to 48.50 g/g (DM: dry matter, 10 kj/m$^2$) and 61.58 g/g (DM, 20 kj/m$^2$). Although there was no significant difference in L, a, b values among the three groups, flavor changes were detected by GC-SAW electronic nose. The number of peaks increased from 10 in the control group (0 kj/m$^2$), to 14 and 15 for the 10 kj/m$^2$ and 20 kj/m$^2$ groups, respectively. Nevertheless, the changes of flavor pattern were not detrimental to the mushroom quality. These results suggested that UV-B irradiation is an effective method to increase the vitamin $D_2$ content without degrading the quality.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.382-389
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• 1997

We present the results on the applicability of the polycrystalline AIN thin films for a surface acoustic wave filter operating at 800 MHz frequency. The films show the FWHM of 3 .deg. from th X-ray rocking curve, which indicates that the c-axis of the films is pre- ferentially oriented along the growth direction. The fabricated band pass filters exhibit the center frequency of 865 MHz with 3dB band-width of 45 MHz. From the measured frequency response, the electro-mechanical coupling constant of 0.8% and the SAW velocity of 5,709 m/s are obtained. Thus, we conclude that the sputtered AIN films are feasible for the fabrication of uper UHF band SAW filters.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1545_1546
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• 2009

This paper reports a novel wireless love-wave biosensor on $41^{\circ}$ YX $LiNbO_3$ piezoelectric substrate and $SiO_2$ guiding layer for Immunoglobulin G (IgG) detection by protein binding. Different from the traditional biosensors based on surface acoustic wave (SAW) oscillator structured by delay line/resonators, a 440MHz reflective delay line consists of SPUDTs and three reflectors placed on $41^{\circ}$ YX $LiNbO_3$ in a row was fabricated as the sensor element. Good linearity, reproducibility, and high sensitivity were observed in the IgG concentration range 1~65nM. Unique advantages as high sensitivity, passive and simple measurement system are present over currently available other biosensors.