High-Frequency Surface Acoustic Wave Resonator Filter Composed of ZnO/High-Density Electrode/Quartz Structure

Abstract

In this paper, we describe the development of a radio frequency (RF) narrow-band surface acoustic wave (SAW) resonator filter composed of a ZnO/high-density metal electrode/quartz structure. First, theoretical analyses were performed to obtain a sufficient reflection coefficient and an appropriate electromechanical coupling factor, where ZnO thickness, type of electrode material, electrode thickness, and metallization ratio were used as variables. Second, one-port SAW resonators were fabricated to confirm the results of the above calculation, and a good agreement between the calculation and measurement results was obtained. Next, an RF narrow-band SAW resonator filter consisting of ZnO/Au interdigital transducer (IDT)/32° YX quartz was fabricated, and a minimum insertion loss of 2.08 dB, a -3 dB bandwidth of 3.9 MHz (0.054%), and an excellent temperature coefficient of frequency (TCF) of 4.0 ppm/°C were simultaneously achieved.