US-20260128724-A1 - FILTER APPARATUS

US20260128724A1US 20260128724 A1US20260128724 A1US 20260128724A1US-20260128724-A1

Abstract

A filter apparatus includes a first piezoelectric substrate including first and second main surfaces, a first resonator including a functional electrode on the first main surface, a second piezoelectric substrate including third and fourth main surfaces, a second resonator including a functional electrode on the third main surface, a support between the first and third main surfaces and providing a space between the first and third main surfaces, and a through electrode passing through the first piezoelectric substrate and electrically coupled to one of the first and second resonators. A thickness of the first piezoelectric layer is smaller than a thickness of the second piezoelectric layer.

Inventors

Yasunobu Hayashi
Yasumasa TANIGUCHI

Assignees

MURATA MANUFACTURING CO., LTD.

Dates

Publication Date: 20260507
Application Date: 20251231
Priority Date: 20230726

Claims (20)

1 . A filter apparatus comprising: a first piezoelectric substrate including a first main surface and a second main surface opposed to each other; at least one first resonator including a functional electrode on the first main surface; a second piezoelectric substrate including a third main surface on a first piezoelectric substrate side and a fourth main surface opposed to the third main surface; at least one second resonator including a functional electrode on the third main surface; a support between the first main surface and the third main surface and providing a space between the first main surface and the third main surface; and a through electrode passing through the first piezoelectric substrate and electrically coupled to any one of the at least one first resonator and the at least one second resonator; wherein the first piezoelectric substrate includes a first supporting substrate and a first piezoelectric layer stacked on the first supporting substrate, the first main surface including a main surface of the first piezoelectric layer; the second piezoelectric substrate includes a second supporting substrate and a second piezoelectric layer stacked on the second supporting substrate, the third main surface including a main surface of the second piezoelectric layer; and a thickness of the first piezoelectric layer is less than a thickness of the second piezoelectric layer.
2 . The filter apparatus according to claim 1 , wherein a material of the first piezoelectric layer and a material of the second piezoelectric layer are the same.
3 . The filter apparatus according to claim 1 , further comprising at least one ladder filter including the at least one first resonator and the at least one second resonator; wherein at least one of the at least one first resonator included in the at least one ladder filter is a series arm resonator of the ladder filter.
4 . The filter apparatus according to claim 3 , wherein the at least one first resonator includes a plurality of first resonators; a plurality of first resonators among the plurality of first resonators are included in the at least one ladder filter; and all of the plurality of first resonators included in the ladder filter are series arm resonators of the ladder filter.
5 . The filter apparatus according to claim 1 , wherein at least one ladder filter including the at least one first resonator and the at least one second resonator is provided; and at least one of the at least one first resonator included in the at least one ladder filter is a parallel arm resonator of the ladder filter.
6 . The filter apparatus according to claim 5 , wherein the at least one first resonator includes a plurality of first resonators; a plurality of first resonators among the plurality of first resonators are included in the at least one ladder filter; and all of the plurality of first resonators included in the ladder filter are parallel arm resonators of the ladder filter.
7 . The filter apparatus according to claim 1 , wherein the functional electrode of the first resonator includes a first IDT electrode on the first piezoelectric layer and including a plurality of first electrode fingers; the functional electrode of the second resonator includes a second IDT electrode on the second piezoelectric layer and including a plurality of second electrode fingers; and a thickness of the first IDT electrode and a thickness of the second IDT electrode are different from each other.
8 . The filter apparatus according to claim 1 , wherein the functional electrode of the first resonator includes a first IDT electrode on the first piezoelectric layer and including a plurality of first electrode fingers; the functional electrode of the second resonator includes a second IDT electrode on the second piezoelectric layer and including a plurality of second electrode fingers; and a material of the first IDT electrode and a material of the second IDT electrode are different from each other.
9 . The filter apparatus according to claim 1 , wherein the functional electrode of the first resonator includes a first IDT electrode on the first piezoelectric layer and including a plurality of first electrode fingers; the functional electrode of the second resonator includes a second IDT electrode on the second piezoelectric layer and including a plurality of second electrode fingers; and in plan view, an extension direction of the plurality of first electrode fingers intersects an extension direction of the plurality of second electrode fingers.
10 . The filter apparatus according to claim 1 , wherein the functional electrode of the first resonator includes a first IDT electrode on the first piezoelectric layer and including a plurality of first electrode fingers; the functional electrode of the second resonator includes a second IDT electrode on the second piezoelectric layer and including a plurality of second electrode fingers; the filter apparatus further includes: a first dielectric film on the first piezoelectric layer and covering the first IDT electrode; and a second dielectric film on the second piezoelectric layer and covering the second IDT electrode; and a thickness of the first dielectric film and a thickness of the second dielectric film are different from each other.
11 . The filter apparatus according to claim 1 , wherein a cut-angle of the first piezoelectric layer and a cut-angle of the second piezoelectric layer are different from each other.
12 . The filter apparatus according to claim 1 , wherein a material of the first piezoelectric layer and a material used for the second piezoelectric layer are different from each other.
13 . The filter apparatus according to claim 1 , wherein the functional electrode of the first resonator includes a first IDT electrode on the first piezoelectric layer and including a plurality of first electrode fingers; and the functional electrode of the second resonator includes a second IDT electrode on the second piezoelectric layer and including a plurality of second electrode fingers.
14 . The filter apparatus according to claim 1 , wherein the first piezoelectric substrate includes a first intermediate layer between the first supporting substrate and the first piezoelectric layer; the second piezoelectric substrate includes a second intermediate layer between the second supporting substrate and the second piezoelectric layer; and a thickness of the first intermediate layer and a thickness of the second intermediate layer are different from each other.
15 . The filter apparatus according to claim 1 , wherein the first piezoelectric substrate includes a first intermediate layer between the first supporting substrate and the first piezoelectric layer; the second piezoelectric substrate includes a second intermediate layer between the second supporting substrate and the second piezoelectric layer; and a material of the first intermediate layer and a material of the second intermediate layer are different from each other.
16 . The filter apparatus according to claim 1 , wherein the first piezoelectric substrate includes a first intermediate layer between the first supporting substrate and the first piezoelectric layer; the second piezoelectric substrate includes a second intermediate layer between the second supporting substrate and the second piezoelectric layer; and in plan view, a first outer circumferential edge is located outside a second outer circumferential edge, the first outer circumferential edge being an outer circumferential edge of a portion of the through electrode passing through the first piezoelectric layer, and the second outer circumferential edge being an outer circumferential edge of a portion of the through electrode passing through the first intermediate layer.
17 . The filter apparatus according to claim 1 , wherein, in plan view, a first outer circumferential edge is located outside a third outer circumferential edge, the first outer circumferential edge being an outer circumferential edge of a portion of the through electrode passing through the first piezoelectric layer, and the third outer circumferential edge being an outer circumferential edge of a portion of the through electrode passing through the first supporting substrate.
18 . The filter apparatus according to claim 1 , wherein the first piezoelectric substrate includes a first intermediate layer between the first supporting substrate and the first piezoelectric layer; the second piezoelectric substrate includes a second intermediate layer between the second supporting substrate and the second piezoelectric layer; and where, in plan view, a first outer circumferential edge is an outer circumferential edge of a portion of the through electrode passing through the first piezoelectric layer, a second outer circumferential edge is an outer circumferential edge of a portion of the through electrode passing through the first intermediate layer, a first point is a point at which a line drawn from a center of the through electrode intersects the first outer circumferential edge, and a second point is a point at which the line intersects the second outer circumferential edge; and a dimension defined as a distance between the first point and the second point is equal to or smaller than a dimension defined as a thickness of the first intermediate layer.
19 . The filter apparatus according to claim 18 , wherein at least one of the at least one first resonator and the at least one second resonator is configured to generate bulk waves in a thickness share mode as a main mode; and the at least one of the at least one first resonator and the at least one second resonator is configured such that d/p is about 0.5 or less, where d denotes a thickness of the piezoelectric layer and p denotes an electrode finger pitch.
20 . The filter apparatus according to claim 1 , wherein the first supporting substrate and the second supporting substrate are different from each other in terms of ψ in Euler angles (φ, θ, ψ).

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Japanese Patent Application No. 2023-121295 filed on Jul. 26, 2023 and is a Continuation Application of PCT Application No. PCT/JP 2024/022942 filed on Jun. 25, 2024. The entire contents of each application are hereby incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to filter apparatuses each including multiple acoustic wave resonators. 2. Description of the Related Art Heretofore, filter apparatuses including acoustic wave resonators have been widely used as filters for mobile phones and the like. International Publication No. WO2006/008940 discloses an example of a piezoelectric filter as a filter apparatus. In this piezoelectric filter, a pair of piezoelectric substrates are bonded together with a bonding layer. A hollow space is formed between the pair of piezoelectric substrates. An interdigital transducer (IDT) and electrode pads are provided on a main surface of each of the piezoelectric substrates so as to be located in the hollow space. In one of the substrates, through holes are provided so as to pass through the substrate. One end portion of each through hole is coupled to an outer electrode. The other end portion of the through hole is coupled to the electrode pad. In order to form through holes in manufacturing of the piezoelectric filter described in International Publication No. WO2006/008940, the through holes are provided in the piezoelectric substrate. The electrode pads are used as stoppers in the process of forming the through holes. However, in reality, the electrode pads tend to be worn out during the process of forming the through holes. For this reason, the reliability of the piezoelectric filter may deteriorate. SUMMARY OF THE INVENTION Example embodiments of the present invention provide filter apparatuses each able to reduce or prevent deterioration of reliability. A filter apparatus according to an example embodiment of the present invention includes a first piezoelectric substrate including a first main surface and a second main surface opposed to each other, at least one first resonator including a functional electrode on the first main surface, a second piezoelectric substrate including a third main surface located on a first piezoelectric substrate side and a fourth main surface opposed to the third main surface, at least one second resonator including a functional electrode on the third main surface, a support between the first main surface and the third main surface and defining a space between the first main surface and the third main surface, and a through electrode passing through the first piezoelectric substrate and electrically coupled to any one of the at least one first resonator and the at least one second resonator. The first piezoelectric substrate includes a first supporting substrate and a first piezoelectric layer stacked on the first supporting substrate, the first main surface including a main surface of the first piezoelectric layer. The second piezoelectric substrate includes a second supporting substrate and a second piezoelectric layer stacked on the second supporting substrate, the third main surface including a main surface of the second piezoelectric layer. A thickness of the first piezoelectric layer is less than a thickness of the second piezoelectric layer. Filter apparatuses according to example embodiments of the present invention are each able to reduce or prevent deterioration of reliability. The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevational sectional view of a filter apparatus according to a first example embodiment of the present invention. FIGS. 2A and 2B are schematic elevational sectional views illustrating steps for providing through electrodes in a piezoelectric substrate in the first example embodiment of the present invention. FIGS. 3A and 3B are schematic elevational sectional views illustrating steps of forming through holes in a piezoelectric substrate in order to provide the through electrodes in the piezoelectric substrate in the first example embodiment of the present invention. FIG. 4 is a schematic plan view of a first resonator in the first example embodiment of the present invention. FIG. 5 is a schematic plan view for explaining the widths and others of the through electrodes. FIG. 6 is a diagram showing a relationship between the thickness of the piezoelectric layer and TCFa in the resonator in the first example embodiment of the present invention. FIG. 7 is a diagram showing a relationship between the thickness of the piezoelectric layer and TCFr in the resonator in the first example embodiment of the present invent