A Review of SiO2 Thin Film Technology for Temperature Compensated SAW Devices

This paper describes a review of SiO2 thin film technology for temperature compensated SAW devices. The SiO2 thin film is widely used for SAW devices because of good temperature co-efficient of frequency (TCF). The authors proposed the SAW devices on the SiO2 /Al/LiNbO3 structure for their sufficient electromechanical coupling factor in addition to good temperature co-efficient of frequency. However, in order to use SiO2 /Al/LiNbO3 structure, it is important to suppress spurious responses. In this paper, the suppression method of the spurious response of the Rayleigh mode and the transceiver mode are reviewed. Furthermore, for the narrow duplex gap application, SiO2 thickness must be increased to achieve the good TCF characteristics. This spurious suppression technique could be applied to the thicker SiO2 structure. Also, this paper describes the suppression of another spurious response, which appears near the first shear wave as the SiO2 thickness increases. These techniques could be applied to the filters and duplexers, and the SAW devices could exhibit the excellent performances.

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