Thin film bulk acoustic wave filter

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 49; no. 4; pp. 535 - 539
• Main Authors: Ylilammi, M., Ella, J., Partanen, M., Kaitila, J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic wave devices, piezoelectric and piezoresistive devices; Acoustic waves; Acoustics; Applied sciences; Bridge circuits; Electronics; Exact sciences and technology; Film bulk acoustic resonators; Fundamental areas of phenomenology (including applications); Glass; Ladders; Microwave filters; Physics; Resonator filters; Resonators; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Semiconductor thin films; Silicon; Silicon nitride; Silicon substrates; Thin films; Transduction; acoustical devices for the generation and reproduction of sound; Transistors; Zinc oxide; Acoustic wave device; Thin film device; Bulk wave; Equivalent circuit; Acoustic resonator; Longitudinal wave; Acoustic wave filter; Modeling
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/58.996574

Thin film bulk acoustic wave (BAW) resonators (FBAR) are fabricated on a silicon nitride bridge using a ZnO piezolayer on a glass substrate and surface micromachining by standard thin film technology. These resonators exhibit a coupling constant k/sub t//sup 2/=7.8% at the first thickness extensional wave mode and are used as impedance elements in a ladder filter in the 1-GHz frequency band of mobile telecommunications. An electrical equivalent circuit is used to characterize the properties of the resonators and to show how the performance of the filter depends on the parameters of the resonators. 2.5% bandwidth, 2.8-dB insertion loss, and 35-dB selectivity are obtained in a filter with six resonators. The technology can be used to manufacture miniature microwave filters without any additional inductances.