New modeling of TFBAR and on-wafer inductor effects on the TFBAR ladder filter performance

In this paper, a new modeling methodology for thin film bulk acoustic resonators (TFBAR) is presented and the formulations for each lumped element in the model are also presented. The proposed model has three optimization variables which is half of the modified Butterworth-Van Dyke (MBVD) model, and as a result the curve fitting for the measured data is much faster and more accurate than any other conventional models. In addition, two types TFBAR ladder filters are designed and fabricated to analyze the effects of on-wafer inductor integration. Fabricated on-wafer spiral inductor reveals the Q-factor of 9 at 2 GHz and the inductor integrated filters have approximately 10 to 12 dB out-of-band rejection improvement compared to the original filters.