Surface acoustic wave electroacoustic device for reduced transversal modes

Patent metadata

Field	Value
Publication number	US-12231111-B2
Application number	US-202117302224-A
Country	US
Kind code	B2
Filing date	Apr 27, 2021
Priority date	Apr 30, 2020
Publication date	Feb 18, 2025
Grant date	Feb 18, 2025

Abstract

Aspects of the disclosure relate to an electroacoustic device that includes a piezoelectric material and an electrode structure that includes a first busbar and a second busbar along with electrode fingers arranged in an interdigitated manner and including a first plurality of fingers connected to the first busbar and a second plurality of fingers connected to the second busbar. The electrode structure further includes a first conductive structure disposed between each of the first plurality of fingers and disposed between the first busbar and the second plurality of fingers. The electrode structure further includes a second conductive structure disposed between each of the second plurality of fingers and disposed between the second busbar and the first plurality of fingers. The first conductive structure and the second conductive structure each have a height that is less than a height of the second plurality of fingers.

First claim

What is claimed is:

1. An electroacoustic device, comprising:
a piezoelectric material; and
an electrode structure, comprising:
a first busbar and a second busbar;
electrode fingers arranged in an interdigitated manner and comprising a first plurality of fingers connected to the first busbar and a second plurality of fingers connected to the second busbar;
a first conductive structure disposed in a plurality of respective regions between adjacent fingers of the first plurality of fingers and disposed between the first busbar and the second plurality of fingers, the first conductive structure having a height that is less than a height of the first plurality of fingers; and
a second conductive structure disposed in a plurality of respective regions between adjacent fingers of the second plurality of fingers and disposed between the second busbar and the first plurality of fingers, the second conductive structure having a height that is less than a height of the second plurality of fingers.

2. The electroacoustic device of claim 1 , wherein the height of the first conductive structure is less than half of the height of the first plurality of fingers, wherein the height of the second conductive structure is less than half of the height of the second plurality of fingers.

3. The electroacoustic device of claim 1 , wherein the height of the first conductive structure is between 5 and 20 nanometers, wherein the height of the second conductive structure is between 5 and 20 nanometers.

4. The electroacoustic device of claim 1 , wherein the first conductive structure is adjacent to and connected to the first busbar, wherein the second conductive structure is adjacent to and connected to the second busbar.

5. The electroacoustic device of claim 1 , wherein the electrode fingers have a central region with a first trap region and a second trap region respectively located on boundaries of the central region, wherein a structural characteristic of the electroacoustic device is different in the first trap region and the second trap region relative to the central region.

6. The electroacoustic device of claim 5 , wherein the structural characteristic corresponds to a portion of each of the electrode fingers having an increased width or increased height within the first trap region and the second trap region relative to the within the central region.

7. The electroacoustic device of claim 5 , wherein the structural characteristic corresponds to at least one of a dielectric material positioned over the trap regions, a mass loading within the trap regions, or a structural effect of a trimming operation.

8. The electroacoustic device of claim 5 , wherein an acoustic velocity in a region of the electroacoustic device defined by the first conductive structure and the second conductive structure is higher than in a region of the electroacoustic device defined by the first trap region, the second trap region, and the central region.

9. The electroacoustic device of claim 8 , wherein the acoustic velocity in the first trap region and the second trap region is lower than the acoustic velocity in the central region.

10. The electroacoustic device of claim 5 , wherein a dimension of the trap region in the direction in which the electrode fingers extend is between one-half of a pitch of the electrode fingers and twice the pitch of the electrode fingers.

11. The electroacoustic device of claim 1 , wherein the electrode fingers have a central region with a first trap region and a second trap region respectively located on boundaries of the central region, wherein an acoustic velocity in a region of the electroacoustic device defined by the first trap region and the second trap region is lower than in a region of the electroacoustic device defined by the central region.

12. The electroacoustic device of claim 1 , wherein a dimension of the first conductive structure in the direction in which the electrode fingers extend is between 1.25 times and 4 times a wavelength for an operating frequency of the electroacoustic device.

13. The electroacoustic device of claim 1 , wherein the electrode fingers extend in a direction normal to a direction of the first busbar and the second busbar.

14. The electroacoustic device of claim 1 , wherein the electrode fingers extend in a direction normal to a direction of the first conductive structure and the second conductive structure.

15. The electroacoustic device of claim 1 , wherein the piezoelectric material comprises lithium tantalate (LiTa03).

16. The electroacoustic device of claim 1 , further comprising:
a substrate;
a trap rich layer forming a portion of or being disposed on the substrate; and
a layer of dielectric material disposed on the substrate, the piezoelectric material disposed on the layer of dielectric material.

17. The electroacoustic device of claim 1 , further comprising:
a substrate; and
a compensation layer disposed on the substrate, the piezoelectric material disposed between the electrode structure and the compensation layer.

18. The electroacoustic device of claim 1 , wherein the electroacoustic device is at least a part of a SAW resonator that forms part of a filter circuit.

19. The electroacoustic device of claim 18 , wherein the filter circuit is part of a transceiver.

20. A method for forming an electroacoustic device, comprising:
forming a layer of a piezoelectric material; and
forming an electrode structure on or above the piezoelectric material, forming the electrode structure comprising:
forming a first busbar and a second busbar;
forming electrode fingers arranged in an interdigitated manner, where forming the electrode fingers comprises forming a first plurality of fingers connected to the first busbar and forming a second plurality of fingers connected to the second busbar;
forming a first conductive structure disposed in a plurality of respective regions between adjacent fingers of the first plurality of fingers, the first conductive structure formed with a height that is less than a height of the first plurality of fingers; and
forming a second conductive structure disposed in a plurality of respective regions between adjacent fingers of the second plurality of fingers, the second conductive structure formed with a height that is less than a height of the second plurality of fingers.

21. The method of claim 20 , wherein the electrode fingers have a central region and a first trap region and a second trap region respectively located on boundaries of the central region, wherein the method further comprises adjusting or forming a structural characteristic of the electroacoustic device in the first and second trap regions to reduce an acoustic velocity.

22. An electroacoustic device, comprising:
a piezoelectric material; and
an electrode structure, comprising:
a first busbar and a second busbar;
electrode fingers arranged in an interdigitated manner and connected to either the first busbar or the second busbar; and
means for controlling an acoustic velocity in a first region between the first busbar and the electrode fingers and in a second region between the second busbar and the electrode fingers, the means for controlling an acoustic velocity having a height that is less than a height of the electrode fingers and disposed in a plurality of respective regions between adjacent fingers of the electrode fingers.

23. The electroacoustic device of claim 22 , wherein the means for controlling an acoust

Assignees

• Rf360 Singapore Pte Ltd

Inventors

• Mayer Markus
• Geselbracht Philipp
• Ammann Stefan
• Ebner Thomas
• Sabbagh Manuel

Classifications

• H03H9/25

  Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)} · CPC title

• H03H9/02559

  of lithium niobate or lithium-tantalate substrates · CPC title

• H03H9/145 Primary

  for networks using surface acoustic waves · CPC title

• H03H9/725

  Duplexers · CPC title

• H03H9/6496

  Reducing ripple in transfer characteristic · CPC title