Study for Temperature Coefficient of Frequency of Surface Acoustic Wave Devices with SiOxNy Film Using LiTaO3 Substrate

The dielectric film formed as a passivation film on the Interdigital Transducer (IDT) electrode of the Surface Acoustic Wave (SAW) device affects the frequency and the Temperature Coefficient of Frequency (TCF) of the SAW device. Since it is known that the sound velocity and Temperature Coefficient of Velocity (TCV) of the SiOxNy film have a correlation with its own refractive index, we fabricated a one-port resonator with dielectric films with different refractive indexes deposited respectively on IDT electrodes and we investigated whether it is possible to control the frequency and TCF of the one-port resonator by manipulating the refractive index of the dielectric film. This study uncovered that the TCF of the one-port resonator, as well as the resonant frequency, correlates with the refractive index of the dielectric film deposited on the IDT electrode. Here, it is considered that the behavior of the resonant frequency and TCF of the one-port resonator are influenced by the sound velocity and TCV of the dielectric film deposited on the IDT electrode and the SAW energy distribution.