XBAR resonators with non-rectangular diaphragms

Patent metadata

Field	Value
Publication number	US-12301212-B2
Application number	US-202418414205-A
Country	US
Kind code	B2
Filing date	Jan 16, 2024
Priority date	Jun 15, 2018
Publication date	May 13, 2025
Grant date	May 13, 2025

Abstract

Acoustic resonator devices, filter devices, and methods of fabrication are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. At least a portion of an edge of the diaphragm is at an oblique angle to the fingers.

First claim

What is claimed:

1. An acoustic resonator device comprising:
a substrate;
a piezoelectric layer attached either directly or via one or more intermediate layers to the substrate and including a portion that forms a diaphragm over a cavity that has an edge at a portion of a perimeter of the cavity;
an interdigital transducer (IDT) at a surface of the piezoelectric layer and having a pair of busbars with a plurality of interleaved fingers extending therefrom,
wherein the IDT is configured to excite a primary shear acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT,
wherein the primary shear acoustic mode excites a bulk shear wave that propagates in a direction substantially normal to a surface of the piezoelectric layer and that is transverse to a primarily lateral direction of an electric field created by the plurality of interleaved fingers of the IDT, and
wherein a respective side of at least one finger of the plurality of interleaved fingers extends from a respective busbar of the pair of busbars at an oblique angle therefrom.

2. The acoustic resonator device of claim 1 , wherein at least a portion of the edge of the diaphragm extends at an angle that is oblique to a direction in which the plurality of interleaved fingers extend on the diaphragm.

3. The acoustic resonator device of claim 1 , wherein the pair of opposing busbars extend in a direction substantially parallel to each other.

4. The acoustic resonator device of claim 1 , wherein the plurality of interleaved fingers of the IDT have a mark to pitch ratio that is greater than 0.05 and less than 0.5, where the mark is a width of at least one finger of the plurality of interleaved fingers and the pitch is a center-to-center spacing between any two adjacent fingers of the plurality of interleaved fingers.

5. The acoustic resonator device of claim 1 , wherein the plurality of interleaved fingers are substantially parallel to each other and extend in a first direction, and an electric field generated by the plurality of interleaved fingers extends in a second direction normal to the first direction.

6. The acoustic resonator device of claim 5 , wherein at least a portion of the edge of the diaphragm extends at an angle in a range from 5 degrees to 25 degrees to the second direction.

7. The acoustic resonator device of claim 1 , wherein a Z-axis of the piezoelectric layer is normal to opposing front and back surfaces thereof, and the piezoelectric layer comprises lithium niobate.

8. The acoustic resonator device of claim 1 , wherein each finger of the plurality of interleaved fingers extends from a respective busbar of the pair of busbars at an oblique angle therefrom.

9. An acoustic resonator device comprising:
a substrate;
a piezoelectric layer attached either directly or via one or more intermediate layers to the substrate;
an interdigital transducer (IDT) at a surface of the piezoelectric layer and having a pair of busbars with a plurality of interleaved fingers extending therefrom,
wherein the IDT is configured to excite a primary shear acoustic mode in the piezoelectric layer in response to a radio frequency signal applied to the IDT,
wherein the primary shear acoustic mode excites a bulk shear wave that propagates in a direction substantially normal to a surface of the piezoelectric layer and that is transverse to a primarily lateral direction of an electric field created by the plurality of interleaved fingers of the IDT, and
wherein a respective side of at least one finger of the plurality of interleaved fingers extends from a respective busbar of the pair of busbars at an oblique angle therefrom.

10. The acoustic resonator device of claim 9 , wherein the piezoelectric layer includes a portion that forms a diaphragm over a cavity that has an edge at a portion of a perimeter of the cavity.

11. The acoustic resonator device of claim 10 , wherein at least a portion of the edge of the diaphragm extends at an angle that is oblique to a direction in which the plurality of interleaved fingers extend on the piezoelectric layer.

12. The acoustic resonator device of claim 9 , wherein the plurality of interleaved fingers are substantially parallel to each other and extend in a first direction, and an electric field generated by the plurality of interleaved fingers extends in a second direction normal to the first direction.

13. The acoustic resonator device of claim 11 , wherein at least a portion of the edge of the diaphragm extends at an angle in a range from 5 degrees to 25 degrees to the second direction.

14. The acoustic resonator device of claim 9 , wherein the pair of opposing busbars extend in a direction substantially parallel to each other.

15. The acoustic resonator device of claim 9 , wherein a Z-axis of the piezoelectric layer is normal to opposing front and back surfaces thereof, and the piezoelectric layer comprises lithium niobate.

16. The acoustic resonator device of claim 9 , wherein each finger of the plurality of interleaved fingers extends from a respective busbar of the pair of busbars at an oblique angle therefrom.

17. The acoustic resonator device of claim 9 , wherein the plurality of interleaved fingers of the IDT have a mark to pitch ratio that is greater than 0.05 and less than 0.5, where the mark is a width of at least one finger of the plurality of interleaved fingers and the pitch is a center-to-center spacing between any two adjacent fingers of the plurality of interleaved fingers.

18. A filter device comprising:
a plurality of acoustic resonators that each comprise:
a substrate;
a piezoelectric layer attached either directly or via one or more intermediate layers to the substrate and including a portion that forms a diaphragm over a cavity that has an edge at a portion of a perimeter of the cavity;
an interdigital transducer (IDT) at a surface of the piezoelectric layer and having a pair of busbars with a plurality of interleaved fingers extending therefrom,

wherein the IDT of each of the plurality of acoustic resonators is configured to excite a primary shear acoustic mode in the respective diaphragm in response to a radio frequency signal applied to the IDT,
wherein the primary shear acoustic mode excites a bulk shear wave that propagates in a direction substantially normal to a surface of the respective piezoelectric layer and that is transverse to a primarily lateral direction of an electric field created by the plurality of interleaved fingers of the respective IDT, and
wherein a respective side of at least one finger of the plurality of interleaved fingers of at least one of the plurality of acoustic resonators extends from a respective busbar of the pair of busbars at an oblique angle therefrom.

19. The filter device of claim 18 , wherein, for at least one of the plurality of acoustic resonators, at least a portion of the edge of the diaphragm extends at an angle that is oblique to a direction in which the plurality of interleaved fingers extend on the diaphragm.

20. The filter device of claim 18 , wherein, for at least one of the plurality of acoustic resonators, the plurality of interleaved fingers of the IDT have a mark to pitch ratio that is greater than 0.05 and less than 0.5, where the mark is a width of at least one finger of the plurality of interleaved fingers and the pitch is a center-to-center spacing between any two adjacent fingers of the plurality of interleaved fingers.

Assignees

• Murata Manufacturing Co

Inventors

• Yantchev Ventsislav
• Turner Patrick
• Plesski Viktor
• Koskela Julius
• Hammond Robert B

Classifications

• H10N30/877

  Conductive materials · CPC title

• H03H9/605

  consisting of a ladder configuration · CPC title

• H03H9/562

  comprising a ceramic piezoelectric layer · CPC title

• H03H9/02039

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

• H03H3/02

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