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US 2025/0357907 A1Published application
Tuning acoustic resonators with back-side coating
AssigneeMurata Manufacturing Co., Ltd.
InventorSean McHugh
Life of this patent
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Abstract
A filter device is provided a substrate; a piezoelectric layer attached to the substrate; a conductor pattern on a first surface of the piezoelectric layer and including a plurality of interdigital transducers of a plurality of resonators that each have interleaved fingers at s respective diaphragm; a first dielectric layer over at least the interleaved fingers of the plurality of interdigital transducers and on the first surface of the piezoelectric layer; and a second dielectric layer on the second surface of the piezoelectric layer that is opposite the first surface. The second dielectric layer provides a more uniform dielectric coating on the second surface of the piezoelectric layer than a coating of the at least one first dielectric layer that is over the interleaved fingers.
Claims20
A filter device comprising:
- a substrate;
- a piezoelectric layer attached to the substrate;
- a conductor pattern on a first surface of the piezoelectric layer and including a plurality of interdigital transducers of a plurality of resonators that each have interleaved fingers at respective diaphragms of the piezoelectric layer that are over one or more cavities, the plurality of resonators including a plurality of shunt resonators and a plurality of series resonators in a ladder filter circuit;
- at least one first dielectric layer over at least the interleaved fingers of the plurality of interdigital transducers and on the first surface of the piezoelectric layer;
- and
- at least one second dielectric layer on the second surface of the piezoelectric layer that is opposite the first surface,
- wherein the at least one second dielectric layer of each of the plurality of shunt resonators has a thickness that is greater than a thickness of the at least one second dielectric layer of all of the plurality of series resonators,
- wherein the at least one second dielectric layer provides a more uniform dielectric coating on the second surface of the piezoelectric layer than a coating of the at least one first dielectric layer that is over the interleaved fingers of the plurality of interdigital transducers and on the first surface of the piezoelectric layer,
- wherein the interleaved fingers of at least one interdigital transducer of the plurality of interdigital transducers has a width that is less than 0.5 times a pitch of the at least one interdigital transducer, and
- wherein the pitch is a center-to-center spacing between at least two adjacent fingers of the at least one interdigital transducer.
7 more elements
A bulk acoustic resonator filter comprising:
- a series laterally-excited bulk acoustic resonator comprising:
- a substrate of the series laterally-excited bulk acoustic resonator having a base and an intermediate layer;
- a piezoelectric layer of the series laterally-excited bulk acoustic resonator attached to the intermediate layer of the series laterally-excited bulk acoustic resonator, and a portion of the piezoelectric layer of the series laterally-excited bulk acoustic resonator disposed over a cavity of the series laterally-excited bulk acoustic resonator;
- an interdigital transducer of the series laterally-excited bulk acoustic resonator comprising interleaved fingers disposed on the piezoelectric layer of the series laterally-excited bulk acoustic resonator;
- a first dielectric layer of the series laterally-excited bulk acoustic resonator on a first surface of the piezoelectric layer and over the interleaved fingers of the interdigital transducer of the series laterally-excited bulk acoustic resonator;
- and
- a second dielectric layer of the series laterally-excited bulk acoustic resonator on a second surface of the piezoelectric layer of the series laterally-excited bulk acoustic resonator that is opposite the first surface,
- wherein a thickness of the second dielectric layer of the series laterally-excited bulk acoustic resonator is greater than a thickness of the first dielectric layer of the series laterally-excited bulk acoustic resonator;
- a shunt laterally-excited bulk acoustic resonator comprising:
- a substrate of the shunt laterally-excited bulk acoustic resonator having a base and an intermediate layer;
- a piezoelectric layer of the shunt laterally-excited bulk acoustic resonator attached to the intermediate layer of the shunt laterally-excited bulk acoustic resonator, and a portion of the piezoelectric layer disposed over a cavity of the shunt laterally-excited bulk acoustic resonator;
- an interdigital transducer of the shunt laterally-excited bulk acoustic resonator comprising interleaved fingers disposed on the piezoelectric layer of the shunt laterally-excited bulk acoustic resonator;
- a first dielectric layer of the shunt laterally-excited bulk acoustic resonator on a first surface of the piezoelectric layer and over the interleaved fingers of the interdigital transducer of the shunt laterally-excited bulk acoustic resonator;
- and
- a second dielectric layer of the shunt laterally-excited bulk acoustic resonator on a second surface of the piezoelectric layer of the shunt laterally-excited bulk acoustic resonator that is opposite the first surface,
- wherein a thickness of the second dielectric layer of the shunt laterally-excited bulk acoustic resonator is greater than a thickness of the first dielectric layer of the shunt laterally-excited bulk acoustic resonator,
- wherein the second dielectric layer of the shunt laterally-excited bulk acoustic resonator has a thickness that is greater than a thickness of the second dielectric layer of the series laterally-excited bulk acoustic resonator.
14 more elements
A filter device comprising:
- a piezoelectric layer;
- a conductor pattern on a first surface of the piezoelectric layer and including interleaved fingers a plurality of interdigital transducers of a plurality of resonators, the plurality of resonators including a plurality of shunt resonators and a plurality of series resonators in a ladder filter circuit;
- at least one first dielectric layer over at least the interleaved fingers of the plurality of interdigital transducers and on the first surface of the piezoelectric layer;
- and
- at least one second dielectric layer on the second surface of the piezoelectric layer that is opposite the first surface,
- wherein the at least one second dielectric layer at each of the plurality of shunt resonators has a thickness that is greater than a thickness of the at least one second dielectric layer at all of the plurality of series resonators, and
- wherein the at least one second dielectric layer at at least one resonator of the plurality of resonators is uniform.
4 more elements
Dependencies are inferred from the claim text.