Coupling of interdigital transducer to plate modes in a slotted acoustically-thin membrane

1 February 1983

journal article
Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Electron Device Letters

Vol. 4 (2) , 35-38
https://doi.org/10.1109/edl.1983.25638

Abstract

Piezoelectric coupling with an interdigital transducer (IDT) to plate modes in a composite ZnO-SiO2-Si membrane that is thinner than an acoustic wavelength has been examined for possible use in forming on-chip filters or resonators. Tests at 80 MHz on a composite membrane approximately 45 µm thick with IDT's having a 76 µm period indicates preferential coupling to the lowest quasi-symmetric plate wave having a phase velocity roughly 60% higher than that of the ordinary surface-acoustic-wave (SAW) on the unthinned portion of the same silicon wafer. Results are presented for a resonator made on such a structure in which end reflectors are single slots etched in the membrane. Numerical calculations confirm the observation and reveal that the electromechanical coupling coefficient is 1.4% as compared with 0.1% for ordinary SAW's on semi-infinite substrate.

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