Transversely-excited film bulk acoustic resonator with recessed rotated-Y-X cut lithium niobate

Patent metadata

Field	Value
Publication number	US-12283944-B2
Application number	US-202318313779-A
Country	US
Kind code	B2
Filing date	May 8, 2023
Priority date	Jun 15, 2018
Publication date	Apr 22, 2025
Grant date	Apr 22, 2025

Abstract

Acoustic resonator devices, filters, and methods are disclosed. An acoustic resonator includes a substrate, a lithium niobate plate having front and back surfaces, wherein Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 0° and less than or equal to 60°. An interdigital transducer (IDT) is formed on the piezoelectric plate.

First claim

It is claimed:

1. An acoustic resonator device comprising:
a substrate;
a piezoelectric plate supported by the substrate and having a diaphragm that spans a cavity; and
an interdigital transducer (IDT) on a surface of the piezoelectric plate and having interleaved fingers on the diaphragm,
wherein the piezoelectric plate comprises lithium niobate with Euler angles that are [0°, β, 0°], where β is greater than or equal to 26° and less than or equal to 34°, and
wherein the piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm, 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 plate, which is also transverse to a primary direction of a laterally-excited electric field created between the interleaved fingers of the IDT.

2. The acoustic resonator device of claim 1 , wherein the substrate comprises a combination of materials and the cavity extends in the substrate.

3. The acoustic resonator device of claim 1 , wherein β is about 30°.

4. An filter device comprising:
a substrate;
a piezoelectric plate supported by the substrate and having a plurality of diaphragms that span a plurality of cavities, respectively; and
a conductor pattern including a plurality of interdigital transducers (IDTs) on a surface of the piezoelectric plate such that interleaved fingers of each of the plurality of IDTs are on a respective diaphragm of the plurality of diaphragms,
wherein the piezoelectric plate comprises lithium niobate with Euler angles that are [0°, β, 0°], where β is greater than or equal to 26° and less than or equal to 34°, and
wherein the piezoelectric plate and the plurality of IDTs are each configured such that a radio frequency signal applied to the respective IDT excites a primary shear acoustic mode in the respective diaphragm, 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 plate, which is also transverse to a primary direction of a laterally-excited electric field created between the interleaved fingers of the IDT.

5. The acoustic resonator device of claim 1 , wherein the direction of acoustic energy is substantially orthogonal to opposing front and back surfaces of the diaphragm.

6. The acoustic resonator device of claim 1 , wherein the piezoelectric plate has a thickness in a direction orthogonal to a surface of the diaphragm that is greater than or equal to 200 nm and less than or equal to 1000 nm.

7. The acoustic resonator device of claim 6 , wherein the interleaved fingers of the IDT have a pitch that is greater than or equal to 2 times the thickness of the piezoelectric plate and less than or equal to 20 times the thickness of the piezoelectric plate.

8. The acoustic resonator device of claim 7 , wherein:
the interleaved fingers of the IDT have a width in a direction perpendicular to a direction in which the interleaved fingers extend, and
the pitch is greater than or equal to 2 times the width and less than or equal to 20 times the width of the interleaved fingers.

9. The acoustic resonator device of claim 1 , further comprising a dielectric layer on the surface of the piezoelectric plate and between the interleaved fingers of the IDT.

10. The filter device of claim 4 , wherein β is about 30°.

11. The filter device of claim 4 , wherein the direction of acoustic energy is substantially orthogonal to opposing front and back surfaces of the respective diaphragm.

12. The filter device of claim 4 , wherein the piezoelectric plate has a thickness in a direction orthogonal to a surface of the respective diaphragm that is greater than or equal to 200 nm and less than or equal to 1000 nm.

13. The filter device of claim 12 , wherein the interleaved fingers of each IDT have a pitch that is greater than or equal to 2 times the thickness of the piezoelectric plate and less than or equal to 20 times the thickness of the piezoelectric plate.

14. The filter device of claim 13 , wherein:
the interleaved fingers of each IDT have a width in a direction perpendicular to a direction in which the interleaved fingers extend, and
the pitch is greater than or equal to 2 times the width and less than or equal to 20 times the width of the interleaved fingers.

15. The filter device of claim 4 , wherein the substrate comprises a combination of materials and the plurality of cavities each extend in the substrate.

16. The filter device of claim 4 , wherein:
the plurality of IDTs form a plurality of acoustic resonators that includes a shunt resonator and a series resonator, and
a thickness of a first dielectric layer over the shunt resonator is greater than a thickness of a second dielectric layer over the series resonator.

Assignees

• Murata Manufacturing Co

Inventors

• Yantchev Ventsislav
• Plesski Viktor
• Garcia Bryant

Classifications

• H10N30/877

  Conductive materials · CPC title

• H03H9/564

  implemented with thin-film techniques · CPC title

• H03H3/02 Primary

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

• H03H2003/023

  the resonators or networks being of the membrane type · CPC title

• H03H9/02039

  consisting of a material from the crystal group 32, e.g. langasite, langatate, langanite · CPC title