# US 9,438,201 B2 · Composite substrates for acoustic wave elements, and acoustic wave elements

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- Number: US 9,438,201 B2
- Document ID: US9438201B2
- Status: Granted
- Kind: B2
- Application number: 14/835,938
- Filed: 2015-08-26
- Published: 2015-12-17
- Granted: 2016-09-06
- Earliest claimed: 2013-03-21
- Assignees: NGK Insulators, Ltd.
- Applicants: Ngk Insulators, Ltd.
- Inventors: Yuji Hori; Tomoyoshi Tai
- Web page: https://patentgrep.com/patent/US9438201B2

## CPC

- H03H 9/02102: {of temperature influence (cutting angles H03H9/02015)}
- H03H 9/02834: {of temperature influence (cut angles H03H9/02543)}
- H03H 9/02228: {Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer}
- H03H 9/02574: {of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate}
- H03H 9/25: Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)}
- H03H 9/6489: {Compensation of undesirable effects}
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

A composite substrate for an acoustic wave element includes a support substrate 1 and a propagation substrate 3 for propagating an acoustic wave. The propagation substrate is bonded to the support substrate 1 and composed of a piezoelectric single crystal. The propagation substrate 3 includes a surface lattice distortion layer 11 in which crystal lattices of the piezoelectric single crystal are distorted.

## Claims

### Claim 1

A composite substrate for an acoustic wave element: said acoustic wave element comprising a support substrate and a propagation substrate for propagating an acoustic wave, said propagation substrate being bonded to said support substrate and comprising a piezoelectric single crystal;
wherein said propagation substrate comprises a bonding face to be bonded to said support substrate and a surface on the opposite side of said bonding face;
wherein said propagation substrate comprises a surface lattice distortion layer on the side of said surface on the opposite side of said bonding face and in which crystal lattices of said piezoelectric single crystal are distorted; and
wherein said surface lattice distortion layer has a thickness of 15 nm or smaller.

### Claim 2 (depends on 1)

The composite substrate of claim 1, wherein said thickness of said surface lattice distortion layer is 3 nm or smaller.

### Claim 3 (depends on 1)

The composite substrate of claim 1, wherein said surface lattice distortion layer comprises a plurality of layers observed by a transmittance type electron microscope.

### Claim 4 (depends on 1)

The composite substrate of claim 1, wherein said acoustic wave comprises a surface acoustic wave, a Lamb wave-type acoustic wave or a bulk acoustic wave.

### Claim 5 (depends on 4)

The composite substrate of claim 4, wherein said acoustic wave element comprises a surface acoustic wave filter or a resonator.

### Claim 6 (depends on 1)

The composite substrate of claim 1, wherein said support substrate and said propagation substrate are bonded to each other directly or through an adhesive layer.

### Claim 7 (depends on 6)

The composite substrate of claim 6, wherein said adhesive layer comprises an organic adhesive layer having a thickness of 0.1 to 1.0 μm.

### Claim 8 (depends on 1)

The composite substrate of claim 1, wherein said piezoelectric single crystal is selected from the group consisting of single crystals of lithium niobate, lithium tantalate and lithium niobate-lithium tantalate solid solution.

### Claim 9 (depends on 1)

The composite substrate of claim 1, wherein said support substrate comprises a material selected from the group consisting of silicon, sapphire, aluminum nitride sintered body, alumina, silicon carbide sintered body, silicon nitride sintered body, borosilicate glass and quartz glass.

### Claim 10 (depends on 1)

The composite substrate of claim 1, wherein said propagation substrate has a thickness of 0.1 to 40 μm.

### Claim 11 (depends on 1)

The composite substrate of claim 1, wherein said acoustic wave element comprises an electrode pattern provided on said propagation substrate.

### Claim 12 (depends on 11)

The composite substrate of claim 11, wherein said acoustic wave element comprises a surface acoustic wave filter or a resonator.