Frequency response study of surface acoustic wave devices with SiOxNy film using LiTaO3 substrate

Abstract

In an attempt to suppress the frequency variation of a surface acoustic wave device caused by dielectric film deposition on an interdigital transducer (IDT) electrode, we fabricated a one-port resonator and examined the correlation with frequency response and refractive index when a SiOxNy film is deposited. Our data showed that the resonator frequency changes as the refractive index of the SiOxNy film changes. We also found that the frequency drift caused by the SiOxNy deposition can be suppressed if the refractive index is kept in a certain range. Then, we performed a finite element method spectral domain analysis to calculate frequency response using the Young’s modulus obtained in this experiment. The calculated frequency response indicated that the refractive index of the SiOxNy film needs to be altered in accordance with the IDT electrode thickness. We suggest that one of the effective ways of controlling the frequency response is to manage the refractive index of SiOxNy.