Background and History. Resonator and Filter Topologies. Baw Device Basics. Design and Fabrication of BAW Devices. FBAR Resonators and Filters. Comparison with SAW Devices. Films Deposition for BAW Devices. Characterization of BAW Devices. Monolithic Integration. System-in-Package (SiP) Integration. Index.

RF bulk acoustic wave filters for communications

Film bulk acoustic resonators (FBARs) having frame elements and filters including the resonators are described.

Piezoelectric resonator structures and electrical filters having frame elements

An acoustic resonator comprises a first electrode a second electrode and a piezoelectric layer disposed between the first and second electrodes. The acoustic resonator further comprises a reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer. An overlap of the reflective element, the first electrode, the second electrode and the piezoelectric layer comprises an active area of the acoustic resonator. The acoustic resonator also comprises a bridge adjacent to a termination of the active area of the acoustic resonator.

Acoustic resonator structure comprising a bridge

An acoustic wave device includes: a piezoelectric film made of an aluminum nitride film containing a divalent element and a tetravalent element, or a divalent element and a pentavalent element; and an electrode that excites an acoustic wave propagating through the piezoelectric film.

Acoustic wave device

An acoustic resonator comprises a first electrode and second electrode comprising a plurality of sides. At least one of the sides of the second electrode comprises a cantilevered portion. A piezoelectric layer is disposed between the first and second electrodes. An electrical filter comprises an acoustic resonator.

Acoustic resonator structure having an electrode with a cantilevered portion

A method for manufacturing a filter device is provided. The filter device comprises a coupled resonator at a first site, a shunt resonator at a second site and a series resonator at a third site, the coupled resonator comprising a first and a second resonator. The method comprising a step of providing a substrate with a piezoelectric layer sandwiched between a first electrode and a first part of a second electrode at the first site and the second site, the piezoelectric layer sandwiched between the first electrode and a second part of the second electrode at the third site. The method further comprising the step of forming a coupling layer on the second electrode, the step of forming a further piezoelectric layer sandwiched between a further first electrode and a further second electrode at the third site and the step of removing the coupling layer at the second and third sites.

Integrated coupled resonator filter and bulk acoustic wave devices

An apparatus includes a stacked crystal filter and a bulk acoustic wave resonator, which are acoustically coupled.

Bulk acoustic wave device

A bulk acoustic wave (BAW) filter device includes a first port, a second port, a first coupled resonator filter stage, a second coupled resonator filter stage and a filter section. The first coupled resonator filter stage includes a first BAW resonator connected to the first port and a second BAW resonator acoustically coupled to the first BAW resonator. The second coupled resonator filter stage includes a third BAW resonator connected to the second port and a fourth BAW resonator acoustically coupled to the third BAW resonator. The filter section includes a fifth BAW resonator, the fifth BAW resonator connected between the second BAW resonator and the fourth BAW resonator.

Coupled resonator filter with a filter section

Designing bulk acoustic wave resonators for RF filter applications is governed by the need for a high quality factor (Q-value), a large piezoelectric coupling and the purity of the main resonance. The most powerful method to suppress spurious modes is terminating the edges of the resonators by a specific border region with a different eigenresonance. In this paper, we demonstrate the design constraints according to the dispersion diagrams and discuss specific realizations of this border regions, particularly for resonators of dispersion type II. Contrary to mirror type resonators with monotonic dispersion branches, membrane resonators comprising AlN as the piezoelectric layer show a negative slope in the main dispersion branch. Consequently, a border region of higher eigenresonance frequency is required for spurious mode suppression. Based on dispersion calculations and FEM simulations, we demonstrate how it has to be designed and discuss the sensitivity to processing induced layer thickness variations. The additional modes emerging between series and parallel resonance are analyzed and related to the respective branches of the dispersion diagram

4E-3 Spurious Mode Suppression in BAW Resonators

Designing bulk acoustic wave resonators for RF filter applications is governed by the need for a high quality factor (Q-value), a large piezoelectric coupling and the purity of the main resonance. The most powerful method to suppress spurious modes is terminating the edges of the resonators by a specific border region with a different eigenresonance. In this paper, we demonstrate the design constraints according to the dispersion diagrams and discuss specific realizations of this border regions, particularly for resonators of dispersion type II. Contrary to mirror type resonators with monotonic dispersion branches, membrane resonators comprising AlN as the piezoelectric layer show a negative slope in the main dispersion branch. Conse- quently, a border region of higher eigenresonance frequency is required for spurious mode suppression. Based on dispersion calculations and FEM simulations, we demonstrate how it has to be designed and discuss the sensitivity to processing induced layer thickness variations. The additional modes emerging between series and parallel resonance are analyzed and related to the respective branches of the dispersion diagram.

Robert Thalhammer

Papers

Integrated coupled resonator filter and bulk acoustic wave devices

Bulk acoustic wave device

Coupled resonator filter with a filter section

4E-3 Spurious Mode Suppression in BAW Resonators

Spurious mode suppression in BAW resonators