Abstract
SiO/sub 2/ under layer between Al electrodes and Li/sub 2/B/sub 4/O/sub 7/ substrate has been shown to provide effective substrate protection both during device fabrication and for long-term device operation. To investigate the parametric dependencies of the basic SAW device parameters in the Al/SiO/sub 2//45/spl deg/-X-Z Li/sub 2/B/sub 4/O/sub 7/ structure, an experimental study was conducted. Isolated solid-electrode transducers and 2-electrode-per-wavelength reflection gratings of different metallization ratio and fabricated with different metal and SiO/sub 2/ layer thickness were measured and analyzed. This paper discusses the dependencies of the SAW velocity, the effective electromechanical coupling, the electrode reflectivity, the transducer static capacitance, and the SAW propagation loss on the metallization ratio and the metal and SiO/sub 2/ layer thickness, as well as versus ambient temperature. Several unexpected results are highlighted. Among these are (1) some unusual dependencies of the SAW velocity on electrode width and SiO/sub 2/ layer thickness, and (2) some rather strong temperature dependencies of the effective electromechanical coupling and the electrode reflectivity. Impact of these behaviors on practical device design, fabrication and performance is also discussed.
Published Version
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