Papers by Author: Ying Chung Chen

Abstract: This paper describes the design and fabrication of dual-mode film bulk acoustic resonator (TFBAR) devices to construct wafer level dual-band T-ladder type filters. The T-ladder type filters is selected in this study for its high quality and simple fabrication processes. The c-axis-tilted ZnO thin films to obtain dual-mode TFBAR devices have been investigated. The characteristics of dual-mode TFBAR devices appeared by off-axis deposition of ZnO thin films with the RF magnetron sputtering. The top and bottom electrodes consisted of titanium (Ti) and platinum (Pt) layers are deposited by dual-gun DC sputtering system. The pass-band width of filters is controlled by the mass loading on the dual-mode. The frequency response is measured using an HP8720 network analyzer and a CASCADE probe station.

Abstract: This paper reports a dual-mode film bulk acoustic resonator (FBAR) device combined with Au/Cr layer to construct a liquid sensor. In order to obtain a liquid sensor with high sensitivity, the dual-mode FBAR with piezoelectric layer of ZnO thin film has been investigated. The dual-mode characteristics of FBAR appeared by off-axis deposition of ZnO thin film with the RF magnetron sputtering. The top and bottom electrodes consisted of a titanium (Ti) and a platinum (Pt) layers were deposited by dual-gun DC sputtering system. Owing to the chemical stability, the Pt layer is not only a perfect bottom electrode but also an etching stop layer. The gold layer (Au) is adopted for the formation of sensory area. In order to improve the adhesion between the Au layer and the Pt layer, a chromium (Cr) layer was deposited onto the backside cavity of the FBAR device before the Au layer was deposited by a DC sputter. The Au/Cr layer is used as the binding layer with analytes of DI water because of its hydrophile. The frequency response is measured using an HP8720 network analyzer and a CASCADE probe station. The resonant frequencies of longitude and shear modes in air appear at 2262.5 MHz and 1012.5MHz, whereas the resonant frequencies of longitude and shear modes in DI water are 2062.5 MHz and 955MHz, respectively.

Abstract: In this study, an SMR-based filter was fabricated by dc/rf magnetron sputtering and photolithography, and a thermal annealing treatment was adopted to improve the frequency response. The SMR-based filter is composed of a ZnO piezoelectric thin film onto SiO2/W Bragg reflector. ZnO thin films were prepared by two-step sputtering with various deposition temperatures to obtain good piezoelectric properties. ZnO layers deposited at the temperature of 200 °C exhibit a highly c-axis preferred orientation, good crystalline characteristics and low surface roughness. The filter is thermal treated by a rapid thermal annealing (RTA) technique. The thermal annealing treatment has improved the film properties of ZnO layers, resulting in a higher c-axis preferred orientation and a lower surface roughness of ZnO films than those of as-deposited ZnO films. The atomic ratio of Zn to O in ZnO film approaches one at the annealing temperature of 400 °C, which results in a comparatively oxidized stoichiometric ZnO film. Finally, the frequency response of the annealed filter is improved, and a lower insertion loss is obtained.

Abstract: Aluminum nitride (AlN) is one of the most popular piezoelectric materials for high frequency resonators, filters and sensors. The piezoelectric property, i.e. electromechanical coupling coefficient, of AlN thin film is highly related to its crystalline orientation. AlN thin films with various c-axis-tilted angles can be fabricated by the RF sputtering technique. The crystallization and grain growth orientations of AlN thin film are examined by XRD, SEM, and TEM, while the bonding condition and nano-mechanical properties are investigated by a raman system and a nano-indentation technique.

Abstract: In this study, ferroelectric thin films of SrBi2Ta2O9 (SBT) or bilayered SrBi2Ta2O9/ Ba(Zr0.1Ti0.9)O3 (SBT/BZT) are successfully deposited on Si substrate under the optimal RF magnetron sputtering conditions, and their electrical and ferroelectric characteristics are discussed. Ferroelectric thin films are deposited on Si substrate under the RF power of 80 W, chamber pressure of 10 mTorr, substrate temperature of 550oC, and different oxygen concentrations. The surface morphology of deposited thin films is observed from the FESEM images, and the memory windows and leakage current of the Al/SBT/BZT/Si (MFS) structure are measured by an impendence phase analyzer and a semiconductor parameter analyzer, respectively. The memory window, capacitance and leakage current density of MFS structures under different oxygen concentrations are also reported. We find that the memory window of bilayered SBT/BZT structure shows larger than one of single layer SBT structure.

Abstract: Most commercial ZnO varistors containing Bi2O3 exhibit excellent varistor properties, but they have a few drawbacks due to Bi2O3 having high volatility and reactivity and higher sintering temperature. In this study, V2O5 is added as the varistor forming oxide to lower down the sintering temperature of ZnO varistors for the further developing the chip Varistor array by using the Ag as the inner electrode. It is found that the sintering temperature of V2O5-added ZnO will be lower down to about 600oC. But the addition of V2O5 has no improvement in the electrical characteristics, and they need many additives to obtain the high performance. For that, the nonlinear properties in these Varistors can be improved by incorporation of some oxide additives. Different MnOx oxides (MnO, MnO2, and Mn3O4) and CoOx oxides (CoO and Co3O4)are used as the minor oxide additives. The influences of different MnOx and CoOx oxides on the nonlinear voltage–current density (V-I) characteristics and the nonlinear exponent (α) of V2O5-ZnO varistor will be well developed.

Abstract: The effects of Nb2O5 content upon the microwave characteristics of ZnTa2−xNbxO6 ceramics are investigated. The appropriate sintering temperatures of ZnTa2−xNbxO6 ceramics slightly decrease with the increase of Nb2O5 content, and the densities and dielectric constants of ZnTa2−xNbxO6 ceramics linearly decrease with the increase of Nb2O5 content. As the Nb2O5 content increases, the Q×f value of ZnTa2−xNbxO6 ceramic first decreases, reaches a minimum value at x=1.0, then increases and reaches a maximum value at x=2.0. The τf values of ZnTa2−xNbxO6 ceramics are positive for x≤0.3, and change to negative ones as x≥0.6.

Abstract: In this study, the effects of oxygen gas plasma on the surface treatment of Ba(Zr0.1Ti0.9)O3 (BZT) films are investigated. The influence of plasma on the structure is developed by using X-ray diffraction patterns and the electrical characteristics are developed by using the MIM and MFIS capacitor structure. Experiment results clearly indicate that the electrical characteristics of BZT film have improved effectively within oxygen plasma surface treatment.

Abstract: In this present work, we adopt conventional solid state reaction techniques to obtain CaCu3Ti4O12 (CCTO) ceramics and the dielectric properties of polycrystalline CCTO samples sintered in the temperature range 900 − 1100°C were investigated. X-ray diffraction (XRD) patterns show no obvious change in crystal phase with various sintering temperature. However, experimental results show that the dielectric properties of CCTO ceramics are very sensitive to processing parameters and the dependence of dielectric constant and loss tangent of CCTO ceramic on processing can be obtained. The effect of sintering conditions on the surface microstructures and the electrical properties of CCTO ceramics are also discussed in this study.

Abstract: Bi4Ti3O12 thin films were deposited on Pt/Ti/Si(p-100) substrate by RF magnetron sputtering at room temperature, and crystallized in a RTA furnace at temperature of 675°C for 10 minutes. SIMS analysis identifies that bismuth content in the Bi4Ti3O12 thin film reduced slightly from the surface into a depth of approximately 200 nm. XRD patterns revealed (117) phase was dominated regardless the film thickness, and the intensity of the other peaks increased with the increase of film thickness. (200) peak became dominant when the thickness of films were greater than 680 nm. SEM observation showed that the grains were stripe plate-like, and the grain size increased with the increase of film thickness. Dielectric constant increased with the increase of film thickness, and kept around a certain value with the thickness ranging from 300 to 640 nm, then it rose again as the film thickness above 680 nm. The leakage current and electrical breakdown also strongly depended on the film thickness.