Piezoelectric element

Patent metadata

Field	Value
Publication number	US-12457902-B2
Application number	US-202217694730-A
Country	US
Kind code	B2
Filing date	Mar 15, 2022
Priority date	Sep 17, 2019
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

A piezoelectric element includes a piezoelectric layer, a first electrode layer, a second electrode layer, and a connecting electrode. The piezoelectric layer includes first and second surfaces, and a through-hole. The second electrode layer is adjacent to the second surface of the piezoelectric layer. The second electrode layer faces the through-hole. The second electrode layer includes silicon as a major component. The connecting electrode is on a connecting surface of the second electrode layer, and the connecting surface faces the through-hole. The connecting electrode is made of a metal. A surface roughness of the connecting surface is greater than a surface roughness of a major surface. The major surface is a portion, other than the connecting surface, of a surface of the second electrode layer, and the surface is adjacent to the piezoelectric layer.

First claim

What is claimed is:

1. A piezoelectric element comprising:
a piezoelectric layer including a first surface, a second surface opposed to the first surface, and a through-hole extending from the first surface to the second surface;
a first electrode layer adjacent to the first surface of the piezoelectric layer;
a second electrode layer adjacent to the second surface of the piezoelectric layer, at least a portion of the second electrode layer being opposed to the first electrode layer with the piezoelectric layer interposed therebetween, the second electrode layer facing the through-hole; and
a connecting electrode on a connecting surface of the second electrode layer, the connecting surface facing the through-hole;
wherein
the second electrode layer includes silicon as a major component;
the connecting electrode is made of a metal; and
a surface roughness Ra of the connecting surface is greater than a surface roughness Ra of a major surface, the major surface being a portion, other than the connecting surface, of a surface of the second electrode layer, the surface being adjacent to the piezoelectric layer.

2. The piezoelectric element according to claim 1 , wherein the connecting surface is located inward relative to the major surface in the second electrode layer in a direction perpendicular or substantially perpendicular to the second surface.

3. The piezoelectric element according to claim 2 , wherein
the major surface is covered with a silicon oxide film;
the connecting surface is not covered with a silicon oxide film or is covered with a silicon oxide film; and
the silicon oxide film covering the connecting surface is thinner than the silicon oxide film that covers the major surface.

4. The piezoelectric element according to claim 2 , wherein a minimum distance between the connecting surface and the major surface in the direction perpendicular or substantially perpendicular to the second surface is greater than or equal to about 5 nm.

5. The piezoelectric element according to claim 1 , wherein
the surface roughness Ra of the connecting surface is about 30 nm or greater and less than about 1 μm; and
the surface roughness Ra of the major surface is less than about 1 nm.

6. The piezoelectric element according to claim 5 , wherein the surface roughness Ra of the major surface is greater than about 0.05 nm.

7. The piezoelectric element according to claim 4 , wherein a width of a portion of the connecting electrode on the connecting surface in a direction parallel or substantially parallel to the second surface is greater than the minimum distance between the connecting surface and the major surface in the direction perpendicular to the second surface.

8. The piezoelectric element according to claim 2 , wherein a width of a portion of the connecting electrode on the connecting surface in a direction parallel or substantially parallel to the second surface is greater than a maximum distance between the connecting electrode and an inner surface of the through-hole.

9. The piezoelectric element according to claim 2 , wherein
the second electrode layer includes an internal surface connecting the connecting surface and the major surface to each other in the direction perpendicular or substantially perpendicular to the second surface; and
the connecting electrode is on the internal surface.

10. The piezoelectric element according to claim 1 , wherein the connecting electrode is in ohmic contact with the connecting surface of the second electrode layer.

11. The piezoelectric element according to claim 1 , wherein the connecting electrode extends continuously along the connecting surface, the inner surface of the through-hole, and the first surface.

12. The piezoelectric element according to claim 1 , wherein the second electrode layer includes a doped single-crystal silicon layer.

13. The piezoelectric element according to claim 1 , wherein the piezoelectric layer is made of a single-crystal material including lithium niobate or lithium tantalate.

14. The piezoelectric element according to claim 1 , wherein an intermediate layer is between the second electrode layer and the piezoelectric layer.

15. The piezoelectric element according to claim 1 , further comprising:
a base portion supporting a multilayer body including at least the first electrode layer, the piezoelectric layer, and the second electrode layer; wherein
the base portion is adjacent to the second electrode layer of the multilayer body, and, as viewed in a stacking direction of the multilayer body, the base portion has a ring shape along a periphery of a surface of the multilayer body, the surface being a surface adjacent to the base portion.

16. The piezoelectric element according to claim 15 , wherein the multilayer body includes a through-slit communicating with an opening located inward of the base portion as viewed in the stacking direction.

Assignees

• Murata Manufacturing Co

Inventors

• Kishimoto Yutaka
• Ikeuchi Shinsuke
• Suzuki Masayuki
• Kurokawa Fumiya

Classifications

• H10N30/8542

  Alkali metal based oxides, e.g. lithium, sodium or potassium niobates · CPC title

• H10N30/87

  Electrodes or interconnections, e.g. leads or terminals · CPC title

• H10N30/082

  by etching, e.g. lithography · CPC title

• H10N30/06

  Forming electrodes or interconnections, e.g. leads or terminals · CPC title

• H10N30/2042

  Cantilevers, i.e. having one fixed end · CPC title