A novel approach to integrate multiple Film Bulk Acoustic Resonators (FBAR) with different frequencies in a single chip

An approach of integrating multiple film bulk acoustic resonators (FBAR) with different frequencies is presented. Conventional FBAR structures were modified by adding a patterned tuning layer on top of Metal/AlN/Metal film stack. By controlling the dimensions of the periodic tuning pattern, resonance frequencies can be modulated due to mass loading effects. As a result, multiple-frequency resonators can be lithographically defined by a single deposition/patterning processing sequence. From finite element analysis, it was found that the pitch of the periodic tuning layer pattern had to be smaller than the characteristic dimension of the resonator, the membrane thickness, to avoid distortion of the resonance peak and to maintain resonator performance. This approach may lead to a viable solution for future integrated multi-mode radio RF front end.