Different DC response in thickness and lateral field excitation film bulk acoustic resonators

This paper describes different DC response in Thickness Field Excitation (TFE) and Lateral Field Excitation (LFE) Film Bulk Acoustic Resonators (FBAR). As DC voltage was applied to TFE FBAR, the resonant frequency shifted linearly with a sensitivity of -4.5 ppm/V. This DC response was independent of temperature (from room temperature to 80 °C). On the other hand, DC voltage did not have an apparent impact on the quality factor (Q). In the case of LFE FBAR, DC voltage cannot alter the resonant frequency. However, an enhanced Q was observed with increasing voltage. This was a result of the acoustoelectric amplification effect due to the lower acoustic velocity in LFE FBAR.