4E-6 Electric Field Sensitivity of Thin Film Resonators Based on Piezoelectric AlN Thin Films

Thin film bulk acoustic wave resonators (FBAR), solidly mounted resonators (SMR), and thin film plate acoustic resonators (FPAR) based on piezoelectric aluminum nitride (AlN) are all attractive candidates for monolithically integrated filters, sensors and oscillators operating in the gigahertz frequency range. This work aims at performing a systematic study of the DC electric field sensitivity of FBAR, SMR and FPAR devices fabricated with the same technology and utilizing membranes with comparable thicknesses. Further, the results are presented in terms of the electric field coefficient of frequency (ECF) which is supposed to be a thickness independent value under certain assumptions. The ECF coefficients of the devices under study were extracted from the frequency shift in the recorded frequency spectra. No hysteresis effects are observed during the measurements. Finally, a novel frequency tuning concept for FPARs based on biasing the distributed reflectors, thus shifting the frequency stopband edges, is reported. The effects studied can be utilized for active temperature compensation circuits as well as for static voltage sensors