# US 5,998,907 A · Surface acoustic wave devices and their manufacturing method

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- Number: US 5,998,907 A
- Document ID: US5998907A
- Status: Granted
- Kind: A
- Application number: 09/087,079
- Filed: 1998-05-29
- Granted: 1999-12-07
- Earliest claimed: 1997-06-02
- Assignees: Matsushita Electric Industrial Co., Ltd.
- Inventors: Yutaka Taguchi; Kazuo Eda; Osamu Kawasaki; Yosihiro Tomita; Keiji Onishi; Shun-ichi Seki; Akihiko Namba; Hiroki Sato; Tetsuyosi Ogura
- Web page: https://patentgrep.com/patent/US5998907A

## CPC

- H03H 9/02834: {of temperature influence (cut angles H03H9/02543)}
- H03H 9/02574: {of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate}
- H03H 9/02921: {Measures for preventing electric discharge due to pyroelectricity}
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

A surface acoustic wave device has a main substrate; a comb-like electrode formed on one of the main surfaces of said main substrate; and a supplementary substrate joined with the other main surface of said main substrate, wherein said supplementary substrate has a smaller thermal expansion coefficient and a larger thickness than said main substrate.

## Claims

### Claim 1

A surface acoustic wave devices comprising
a laminated main substrate formed by directly joining a first piezoelectric monocrystal substrate having a first polarizing direction with a second piezoelectric monocrystal substrate having a second polarizing direction opposite the first polarizing direction;
a comb-like electrode formed on a first main surface of said main substrate; and
a supplementary substrate joined to a second main surface of said main substrate, said supplementary substrate having a smaller thermal expansion coefficient and a larger thickness than said main substrate.

### Claim 2

A surface acoustic wave devices comprising:
a laminated main substrate formed by directly joining a first piezoelectric monocrystal substrate having a first polarizing direction with a second piezoelectric monocrystal substrate having a second polarizing direction opposite the first polarizing direction;
a comb-like electrode formed on a first main surface of said main substrate; and
a supplementary substrate joined to a second main surface of said main substrate, said supplementary substrate having a larger thermal expansion coefficient and a smaller thickness than said main substrate.

### Claim 3 (depends on 1)

A surface acoustic wave device according to claim 1, wherein said first main surfaces, including said comb-like electrode, is covered with a film mainly comprising silicon oxide.

### Claim 4 (depends on 2)

A surface acoustic wave device according to claim 2, wherein said first main surface, including said comb-like electrode, is covered with a film mainly comprising silicon oxide.

### Claim 5 (depends on 1)

A surface acoustic wave device according to claim 1, wherein an insulating film is provided at a junction interface between said main substrate and said supplementary substrate.

### Claim 6 (depends on 5)

A surface acoustic wave device according to claim 5, wherein said insulating film is an inorganic film mainly comprising silicon oxide.

### Claim 7 (depends on 1)

A surface acoustic wave device according to claim 1, wherein a thickness of said main substrate is larger than one surface acoustic wavelength.

### Claim 8 (depends on 1)

A surface acoustic wave device according to claim 1, wherein a conductive film is provided at a junction interface between said main substrate and said supplementary substrate.

### Claim 9 (depends on 8)

A surface acoustic wave device according to claim 8, wherein a thickness of said main substrate is almost equal to one surface acoustic wavelength.

### Claim 10 (depends on 1)

A surface acoustic wave device according to claim 1, wherein said main substrate is formed from a material selected from the group consisting of lithium tantalate, lithium niobate, Langasite, and lithium borate.

### Claim 11 (depends on 1)

A surface acoustic wave device according to claim 1, wherein said supplementary substrate is formed from glass or silicon.