High-frequency monolithic thin-film piezoelectric-on-substrate filters

Abstract

A class of micromachined acoustic filters is presented in which the number of individual resonant structures is reduced to 1 (monolithic filter). This resonant structure is comprised of a stack of thin-film piezoelectric-on-silicon. Symmetric and anti-symmetric resonance modes (dual modes) of the silicon structure are piezoelectrically excited and coupled to realize a 2-pole narrowband filter. High-order lateral bulk acoustic resonance modes of a rectangular plate are utilized to design dispersed-frequency UHF filters fabricated on a single substrate. Thickness mode filters are also realized at GHz frequencies using a new interdigitated electrode design. Additionally, it is shown that the filter bandwidth can be controlled by changing the dimensions of the resonant structure and the electrode pattern. Narrowband lateral mode filters with filter Q’s larger than 300 at ~440 MHz and thickness mode filters with filter Q’s in the range of 150–900 at ~3.1 GHz are demonstrated.

Foreword

“…The third paper, by Muralt et al [3], highlights the impact of material parameters for GHz applications; monolithic thinfilm piezoelectric-on-substrate high-frequency filters are addressed by Abdolvand and Ayazi [4] in the fourth paper. The fifth paper (Ikehashi et al [5]) outlines a lithographical bending control method for piezoelectric actuator fabrication for MEMS applications.…”

“…Of the piezoelectric papers, Al Ahmad and Plana [1] describe the displacement detection of thin-film AlN using capacitance measurements while Menéndez et al [2] report a design methodology for microwave acoustic filters. The third paper, by Muralt et al [3], highlights the impact of material parameters for GHz applications; monolithic thin-film piezoelectric-on-substrate high-frequency filters are addressed by Abdolvand and Ayazi [4] in the fourth paper. The fifth paper (Ikehashi et al [5]) outlines a lithographical bending control method for piezoelectric actuator fabrication for MEMS applications.…”