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This paper focuses on the fabrication of film bulk acoustic-wave resonator (FBAR) comprising an aluminum nitride (AlN) piezoelectric thin film sandwiched between two metal electrodes and located on a silicon substrate with a low-stress silicon nitride (Si 3 N 4 ) support membrane for high frequency wireless applications, and analyzes the optimization of the thin AlN film deposition parameters on Mo electrodes using the reactive RF magnetron sputter system. Several critical parameters of the sputtering process such as RF power and Ar/N 2 flow rate ratio were studied to clarify their effects on different electrodes characteristics of the AlN films. The experiment indicated that the process for Mo electrode was easier compared with that of the Pt/Ti or Au/Cr bi-layer electrode as it entailed only one photo resist and metal deposition step. Besides, Pt/Ti or Au/Cr electrodes reduced the resonance frequency due to their high mass density and low bulk acoustic velocity. Compared with the case of the Al bottom electrode, there is no evident amorphous layer between the Mo bottom electrode and the deposited AlN film. The characteristics of the FBAR devices depend not only upon the thickness and quality of the AlN film, but also upon the thickness of the top electrode and the materials used. The results indicate that decreasing the thickness of either the AlN film or the top electrode increases the resonance frequency. This suggests the potential of tuning the performance of the FBAR device by carefully controlling AlN film thickness. Besides, increasing either the thickness of the AlN film or higher RF power has improved a stronger c-axis orientation and tended to promote a narrower rocking curve full-width at half-maximum (FWHM), but increased both the grain size and the surface roughness. An FBAR device fabricated under optimal AlN deposition parameters has demonstrated the effective electromechanical coupling coefficient (k 2 eff ) and the quality factor (Q f x ) are about 1.5% and 332, respectively. sputtering, thin film, piezoelectricThe rapid growth of wireless mobile telecommunication systems has led to an increasing demand for high-frequency oscillators, filters and duplexers capable of operating in the 0.5 to 5 GHz frequency range. Conventionally, microwave ceramic resonators and surface acoustic wave (SAW) resonators have been applied in this frequency range. However, microwave ceramic resonators tend to be physically bulky, while SAW resonators demonstrate a relatively poor sensitivity to temperature and have high insertion losses and limited power handling characteristics. Moreover, SAW devices must be generally interfaced at the board level rather than directly at the chip level. Micromachined thin film bulk acoustic-wave resonators (FBARs) have been developed to address the limitations of these conventional devices. Compared with microwave ceramic resonators and SAW resonators, FBAR devices have the advantages of low cost and enhanced electrical performance, and are characterized by low insertion losses, hig...

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The design and construction of wide-band and high efficiency acoustical projector has long been considered an art beyond the capabilities of many smaller groups. Langevin type piezoelectric transducers have been the most candidate of sonar array system applied in underwater communication. The transducers are fabricated, by bolting head mass and tail mass on both ends of stacked piezoelectric ceramic, to satisfy the multiple, conflicting design for high power transmitting capability. The aim of this research is to study the characteristics of Langevin type piezoelectric transducer that depend on different metal loading. First, the Mason equivalent circuit is used to model the segmented piezoelectric ceramic, then, the impedance network of tail and head masses is deduced by the Newton's theory. To obtain the optimal solution to a specific design formulation, PSPICE controlled-source programming techniques can be applied. A valid example of the application of PSPICE models for Langevin type transducer analysis is presented and the simulation results are in good agreement with the experimental measurements. acoustical projector, Langevin type, piezoelectric transducer, stacked piezoelectric ceramic, Mason model, controlled-source, PSPICE In many underwater acoustical applications, electromechanical systems are often composed of a group of identical piezoelectric ceramic segments that are interconnected "mechanically in series and electrically in parallel" [1] so as to produce reinforced mechanical motion for high-power sound generation. In an air backed Langevin type transducer construction application, some practical consideration is in demand [2] , e.g. the head mass is constructed as an alignment shank on the ceramic end and a large flat radiation surface to attain a large radiating loading in the water medium, the tail mass is configured as a horn structure to reduce the transmission power in the air medium

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