• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.193.2-193
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• 2000

• 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

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1039-1044
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• 2002

Film Bulk Acoustic Resonator (FBAR) using thin piezoelectric films can be made as monolithic integrated devices with compatibility to semiconductor process, leading to small size, low cost and high Q RF circuit elements with wide applications in communications area. This paper presents an MMIC compatible suspended FBAR using SOI micromachining. It is possible to make a single crystal silicon membrane using a SOI wafer In fabricating active devices, SOI wafer offers advantage which removes the substrate loss. FBAR was made on the 12㎛ silicon membrane. Electrode and Piezoelectric materials were deposited by RF magnetron sputter. The maximum resonance frequency of FBAR was shown at 2.5GHz range. The reflection loss, K$^2$$\_$eff/, Q$\_$serise/ and Q$\_$parallel/ in that frequency were 1.5dB, 2.29%, 220 and 160, respectively.

• Proceedings of the Korea Crystallographic Association Conference
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• 2007.11a
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• pp.40-40
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• 2007

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.905-909
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• 2007

Crystalline and micro-structural characteristics of ZnO thin films which were deposited on p-Si(100) with cooling naturally down of pre-heated substrate during RF magnetron sputter deposition, were investigated by XRD and SEM in this paper. The film which was prepared on the substrate which was pre-heated to $400^{\circ}C$ before deposition and then cooled naturally down during deposition, showed the most outstanding c-axis preferred orientation. The ZnO thin film having the best crystalline result were applied to SMR type FBAR device and resonance properties of the device were investigated by network analyzer. It showed that resonance frequency was 2.05 GHz, return loss was -30.64 dB, quality factor was 3169 and electromechanical coupling factor was 0.4 %. This deposition method would be very useful for application of surface acoustic wave filter or film bulk acoustic wave resonator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.57-60
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• 2003

This paper describes the modeling and simulation results for film bulk acoustic resonators(FBAR). We present the frequency tuning mechanisms, analytical solutions of the wave equation and the influence of the thickness of the electrodes. The impedance for PZT based FBAR is derived utilizing proper boundary conditions and their material parameters. Ferroelectrics-based RF filter composed of FBARs are designed.

• ETRI Journal
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• v.36 no.2
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• pp.317-320
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• 2014

A balanced RF duplexer with low interference in an extremely narrow bandgap is proposed. The Long-Term Evolution band-7 duplexer should be designed to prevent the co-existence problem with the WiFi band, whose fractional bandgap corresponds to only 0.7%. By implementing a hybrid bulk acoustic wave (BAW) structure, the temperature coefficient of frequency (TCF) value of the duplexer is successfully reduced and the suppressed interference for the narrow bandgap is performed. To achieve an RF duplexer with balanced Rx output topology, we also propose a novel balanced BAW Rx topology and RF circuit block. The novel balanced Rx filter is designed with both lattice- and ladder-type configurations to ensure excellent attenuation. The RF circuit block, which is located between the antenna and the Rx filter, is developed to simultaneously function as a balance-tounbalance transformer and a phase shift network. The size of the fabricated duplexer is as small as $2.0mm{\times}1.6mm$. The maximum insertion loss of the duplexer is as low as 2.4 dB in the Tx band, and the minimum attenuation in the WiFi band is as high as 36.8 dB. The TCF value is considerably lowered to $-16.9ppm/^{\circ}C$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.18-26
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• 2001

In this paper, the resonant characteristics and modes of the film bulk acoustic wave resonator (FBAR) used in 1~2 GHz frequency region are analyzed by it's input impedance which was calculated by three dimensional finite element method formulated as eigenvalue problem using electro-mechanical wave equation and boundary condition. It was extracted that the resonant and the spurious characteristics considering the effects of electrode area and shape variation and unsymmetry of upper and lower electrode. Those effects couldn't be analyzed by on dimensional analysis, e.g. Mason equivalent model. The simulation result was confirmed by comparing with the simulation data from Mason model analysis and the measured data of the ZnO FBAR fabricated using micro-machining technique. Also, through the simulation of the area variations of FBAR, it was obtained that the optimum ratio of length and thickness is 20:1 and the minimum ratio is 5:1 to operate thickness vibration mode.

• 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 information and communication convergence engineering
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• v.5 no.4
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• pp.316-319
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• 2007

This paper presents some methods to improve the resonance characteristics of film bulk acoustic-wave resonator (FBAR) devices. The FBAR devices were fabricated on multilayer Bragg reflectors (BR) into which very thin chromium (Cr) adhesion layers were inserted, followed by several kinds of thermal annealing processes. These methods resulted in an excellent device improvement in terms of return loss and Q-factors.