Solidly-mounted transversely-excited film bulk acoustic resonator with recessed interdigital transducer fingers

Patent metadata

Field	Value
Publication number	US-2025062739-A1
Application number	US-202418936644-A
Country	US
Kind code	A1
Filing date	Nov 4, 2024
Priority date	Jun 15, 2018
Publication date	Feb 20, 2025
Grant date	—

Abstract

An acoustic resonator is provided that includes a substrate; an acoustic Bragg reflector supported by the substrate; a piezoelectric layer above the acoustic Bragg reflector and opposite the substrate, the piezoelectric plate having at least one groove extending into a surface thereof; and an interdigital transducer (IDT) having a plurality of interleaved fingers with at least one finger is disposed in the at least one groove of the piezoelectric plate, respectively.

First claim

What is claimed:

1 . A bulk acoustic resonator comprising:
a substrate; a piezoelectric layer having at least one groove in a surface thereof; an acoustic Bragg reflector between the substrate and the piezoelectric layer; and an interdigital transducer (IDT) having a plurality of interleaved fingers with at least one finger disposed in the at least one groove of the piezoelectric layer, wherein the at least one groove extends completely through the piezoelectric layer.

2 . The bulk acoustic resonator according to claim 1 , wherein the piezoelectric layer is directly attached to a surface of the acoustic Bragg reflector and the at least one groove extends through the piezoelectric layer and to the surface of the acoustic Bragg reflector.

3 . The bulk acoustic resonator according to claim 1 , wherein the IDT and the piezoelectric layer are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric layer, the primary shear acoustic mode being a bulk shear mode where acoustic energy propagates along a direction substantially orthogonal to the surface of the piezoelectric layer.

4 . The bulk acoustic resonator according to claim 3 , wherein the direction substantially orthogonal to the surface of the piezoelectric layer is also normal to a primary direction of an electric field created between the plurality of interleaved fingers of the IDT.

5 . The bulk acoustic resonator according to claim 1 , wherein the acoustic Bragg reflector is sandwiched directly between the substrate and the piezoelectric layer.

6 . The bulk acoustic resonator according to claim 1 , wherein all of the plurality of interleaved fingers of the IDT are disposed in respective grooves in the piezoelectric layer.

7 . The bulk acoustic resonator according to claim 1 , wherein the piezoelectric layer is a rotated z-cut lithium niobate plate.

8 . The bulk acoustic resonator according to claim 1 , wherein the surface of the piezoelectric layer is a top surface of the piezoelectric layer that is opposite to a bottom surface facing the acoustic Bragg reflector and the IDT is disposed on the top surface of the piezoelectric layer.

9 . The bulk acoustic resonator according to claim 8 , further comprising a dielectric layer disposed on at least the top surface of the piezoelectric layer over and between the interleaved fingers of the IDT.

10 . A bulk acoustic resonator comprising:
a substrate; a piezoelectric layer having a plurality of grooves in a surface of the piezoelectric layer; an acoustic Bragg reflector between the substrate and the piezoelectric layer; and an interdigital transducer (IDT) having a plurality of interleaved fingers disposed in the plurality of grooves, respectively, wherein at least one groove of the plurality of grooves extends completely through the piezoelectric layer.

11 . The bulk acoustic resonator according to claim 10 , wherein the piezoelectric layer is directly attached to a surface of the acoustic Bragg reflector and the plurality of grooves extends through the piezoelectric layer and to the surface of the acoustic Bragg reflector.

12 . The bulk acoustic resonator according to claim 11 , wherein the IDT and the piezoelectric layer are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric layer, the primary shear acoustic mode being a bulk shear mode where acoustic energy propagates along a direction substantially orthogonal to the surface of the piezoelectric layer.

13 . The bulk acoustic resonator according to claim 11 , wherein the acoustic Bragg reflector is sandwiched directly between the substrate and the piezoelectric layer.

14 . The bulk acoustic resonator according to claim 11 , wherein the surface of the piezoelectric layer is a top surface of the piezoelectric layer that is opposite to a bottom surface facing the acoustic Bragg reflector and the IDT is disposed on the top surface of the piezoelectric layer, and wherein a dielectric layer is disposed on at least the top surface of the piezoelectric layer over and between the interleaved fingers of the IDT.

15 . A filter device comprising:
a plurality of bulk acoustic resonators, at least one of the plurality of bulk acoustic resonators comprising:
a substrate;
a piezoelectric layer having at least one groove in a surface thereof;
an acoustic Bragg reflector between the substrate and the piezoelectric layer; and
an interdigital transducer (IDT) having a plurality of interleaved fingers with at least one finger disposed in the at least one groove of the piezoelectric layer,
wherein the at least one groove extends completely through the piezoelectric layer.

16 . The filter device according to claim 15 , wherein the piezoelectric layer of the at least one bulk acoustic resonator is directly attached to a surface of the acoustic Bragg reflector and the at least one groove extends through the piezoelectric layer and to the surface of the acoustic Bragg reflector.

17 . The filter device according to claim 15 , wherein the IDT and the piezoelectric layer of the at least one bulk acoustic resonator are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric layer, the primary shear acoustic mode being a bulk shear mode where acoustic energy propagates along a direction substantially orthogonal to the surface of the piezoelectric layer.

18 . The filter device according to claim 15 , wherein the acoustic Bragg reflector of the at least one bulk acoustic resonator is sandwiched directly between the substrate and the piezoelectric layer.

19 . The filter device according to claim 15 , wherein all of the plurality of interleaved fingers of the IDT of the at least one bulk acoustic resonator are disposed in respective grooves in the piezoelectric layer.

20 . The filter device according to claim 15 , wherein, for the at least one bulk acoustic resonator:
the surface of the piezoelectric layer is a top surface of the piezoelectric layer that is opposite to a bottom surface facing the acoustic Bragg reflector and the IDT is disposed on the top surface of the piezoelectric layer, a dielectric layer is disposed on at least the top surface of the piezoelectric layer over and between the interleaved fingers of the IDT.

Assignees

• Murata Manufacturing Co

Inventors

• Plesski Viktor

Classifications

• H03H9/13

  for networks consisting of piezoelectric or electrostrictive materials (for networks using surface acoustic waves H03H9/145) · CPC title

• H03H9/54

  comprising resonators of piezoelectric or electrostrictive material (comprising resonators using surface acoustic waves H03H9/64) · CPC title

• H03H3/02

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H03H9/02015

  Characteristics of piezoelectric layers, e.g. cutting angles · CPC title

• H03H9/568

  consisting of a ladder configuration · CPC title