Avago Technologies Wireless IP (singapore) Pte. Ltd.

Avago Technologies Wireless Ip, Pte. Ltd.

Avago Technologies General IP (singapore) Pte. Ltd.

Stephen Ellis

John Dwight Larson, Iii

Yury Oshmyansky

Naghmeh Sarkeshik

Richard C Ruby

Paul A Bradley

A substrate defining a cavity comprising a wide, shallow first portion and a narrow, deep second portion is provided. The first portion of the cavity extends into the substrate from the front side of the substrate and is filled with sacrificial material. The second portion extends deeper into the substrate from the first portion. A device structure is fabricated over the sacrificial material. A release etchant is introduced from the back side of the substrate via the second portion of the cavity to remove from the first portion of the cavity the sacrificial material underlying the device structure. Removing from the first portion of the cavity the sacrificial material underlying the device structure by introducing the release etchant from the back side of the substrate via the second portion of the cavity allows the release etch to be performed without exposing the device structure to the release etchant. This allows the device structure to incorporate materials that have a low etch selectivity with respect to the sacrificial material.

Suspended device and method of making

The band-pass filter has an upper film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, and, between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material. Each of the FBARs has opposed planar electrodes and a piezoelectric element between the electrodes. The acoustic decoupler controls the coupling of acoustic energy between the FBARs. Specifically, the acoustic decoupler couples less acoustic energy between the FBARs than would be coupled by direct contact between the FBARs. The reduced acoustic coupling gives the band-pass filter desirable in-band and out-of-band properties.

Decoupled stacked bulk acoustic resonator band-pass filter with controllable pass bandwith

One embodiment of the film acoustically-coupled transformer (FACT) includes a decoupled stacked bulk acoustic resonator (DSBAR) having a lower film bulk acoustic resonator (FBAR) an upper FBAR stacked on the lower FBAR, and, between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material. Each FBAR has opposed planar electrodes with a piezoelectric element between them. The FACT additionally has first terminals electrically connected to the electrodes of one FBAR and second terminals electrically connected to the electrodes of the other FBAR. Another embodiment has decoupled stacked bulk acoustic resonators (DSBARs), each as described above, a first electrical circuit interconnecting the lower FBARs, and a second electrical circuit interconnecting the upper FBARs. The FACT provides impedance transformation, can linking single-ended circuitry with balanced circuitry or vice versa and electrically isolates primary and secondary. Some embodiments are additionally electrically balanced.

Film acoustically-coupled transformer

The film acoustically-coupled transformer (FACT) has a first and second decoupled stacked bulk acoustic resonators (DSBARs). Each DSBAR has a lower film bulk acoustic resonator (FBAR), an upper FBAR atop the lower FBAR, and an acoustic decoupler between them FBARs. Each FBAR has opposed planar electrodes and a piezoelectric element between the electrodes. A first electrical circuit interconnects the lowers FBAR of the first DSBAR and the second DSBAR. A second electrical circuit interconnects the upper FBARs of the first DSBAR and the second DSBAR. In at least one of the DSBARs, the acoustic decoupler and one electrode of the each of the lower FBAR and the upper FBAR adjacent the acoustic decoupler constitute a parasitic capacitor. The FACT additionally has an inductor electrically connected in parallel with the parasitic capacitor. The inductor increases the common-mode rejection ratio of the FACT.

Film acoustically-coupled transformer with increased common mode rejection

The decoupled stacked bulk acoustic resonator (DSBAR) device has a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, and an acoustic decoupler between the FBARs. Each of the FBARs has opposed planar electrodes and a layer of piezoelectric material between the electrodes. The acoustic decoupler has acoustic decoupling layers of acoustic decoupling materials having different acoustic impedances. The acoustic impedances and thicknesses of the acoustic decoupling layers determine the acoustic impedance of the acoustic decoupler, and, hence, the pass bandwidth of the DSBAR device. Process-compatible acoustic decoupling materials can then be used to make acoustic decouplers with acoustic impedances (and pass bandwidths) that are not otherwise obtainable due to the lack of process-compatible acoustic decoupling materials with such acoustic impedances.

Pass bandwidth control in decoupled stacked bulk acoustic resonator devices

The encapsulated film bulk acoustic resonator (FBAR) device comprises a substrate, an FBAR stack over the substrate, an element for acoustically isolating the FBAR stack from the substrate, encapsulant covering the FBAR stack, and an acoustic Bragg reflector between the top surface of the FBAR stack and the encapsulant. The FBAR stack comprises an FBAR and has a top surface remote from the substrate. The FBAR comprises opposed planar electrodes and a piezoelectric element between the electrodes. The acoustic Bragg reflector comprises a metal Bragg layer and a plastic Bragg layer juxtaposed with the metal Bragg layer. The large ratio between the acoustic impedances of the metal of the metal Bragg layer and the plastic material of the plastic Bragg layer enables the acoustic Bragg reflector to provide sufficient acoustic isolation between the FBAR and the encapsulant for the frequency response of the FBAR device to exhibit minor, if any, spurious artifacts arising from undesirable acoustic coupling between the FBAR and the encapsulant.

Film bulk acoustic resonator (FBAR) devices with simplified packaging

The film bulk acoustic resonator (FBAR) device comprises a substrate, an acoustic Bragg reflector over the substrate, a piezoelectric element over the acoustic Bragg reflector, and a remote-side electrode over the piezoelectric element. The acoustic Bragg reflector comprises a metal Bragg layer juxtaposed with a plastic Bragg layer. The large ratio between the acoustic impedances of the plastic material of the plastic Bragg layer and the metal of the metal Bragg layer provides sufficient acoustic isolation between the FBAR and the substrate for the frequency response of the FBAR device to exhibit minor, if any, spurious artifacts arising from undesirable acoustic coupling between the FBAR and the substrate.

Cavity-less film bulk acoustic resonator (FBAR) devices

The band-pass filter has first terminals, second terminals, a first decoupled stacked bulk acoustic resonator (DSBAR), a second DSBAR, and an electrical circuit connecting the first DSBAR and the second DSBAR in series between the first terminals and the second terminals. Each DSBAR has a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs. Each FBAR has opposed planar electrodes and a piezoelectric element between the electrodes.

Decoupled stacked bulk acoustic resonator-based band-pass filter

The film acoustically-coupled transformer (FACT) has decoupled stacked bulk acoustic resonators (DSBARs), a first electrical circuit and a second electrical circuit. Each of the DSBARs has a lower film bulk acoustic resonator (FBAR), an upper FBAR and an acoustic decoupler. The upper FBAR is stacked on the lower FBAR and the acoustic decoupler is located between the FBARs. Each FBAR has opposed planar electrodes and a piezoelectric element between the electrodes. The first electrical circuit interconnects the lower FBARs. The second electrical circuit interconnects the upper FBARs. The FBARs of one of the DSBARs differ in electrical impedance from the FBARs of another of the DSBARs. The FACT has an impedance transformation ratio greater than 1:m, where m is the number of DSBARs. The actual impedance transformation ratio depends on the ratio of the impedances of the FBARs.

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Pleasanton, CA, United States of America

Stephen Ellis