Thermally compensated ZnO film bulk acoustic resonator for RF application above 5GHz frequency

We present a study of the effect of introducing two-series air gap capacitor and tailoring the oxide in thin-film bulk acoustic resonator (FBARs) for thermal compensation at a frequency > 5 GHz. This approach reduces the temperature coefficient of frequency value of ZnO FBAR upto 0.011 ppm /^∘ C within the industrial temperature range at 5.45 GHz frequency. The quality factor of the compensated FBARs is 1100 with a motional impedance of 38 Ω . This exceeds significantly the quality factor of uncompensated FBARs ( ∼ 120). Additionally, we report on the stress and strain required to obtain an optimal design of compensated FBARs.