Surface acoustic wave filter and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-11356076-B2
Application number	US-202017134228-A
Country	US
Kind code	B2
Filing date	Dec 25, 2020
Priority date	Jan 22, 2020
Publication date	Jun 7, 2022
Grant date	Jun 7, 2022

Abstract

In a surface acoustic wave filter according to an embodiment, a thickness of a piezoelectric crystal substrate bonded over a support substrate made of an oxide crystal is 0.05 to 0.5 μm, and an odd-order harmonic is used.

First claim

What is claimed is:

1. A surface acoustic wave filter comprising:
an oxide crystal substrate;
a piezoelectric crystal substrate bonded over the oxide crystal substrate; and
an IDT (Interdigital Transducer) electrode formed over the piezoelectric crystal substrate, wherein
a thickness of the piezoelectric crystal substrate is 0.05 to 0.5 μm, and
an odd-order harmonic is used.

2. The surface acoustic wave filter according to claim 1 , wherein the odd-order harmonic is a third harmonic.

3. The surface acoustic wave filter according to claim 1 , wherein
a width w of each of electrode fingers of the IDT electrode is 0.2 to 1.5 μm, and
a ratio w/p between the width w and a pitch p of the electrode fingers is 0.7 to 0.9.

4. The surface acoustic wave filter according to claim 1 , wherein
the oxide crystal substrate is a quartz-crystal substrate, and
the piezoelectric crystal substrate is a LiTaO 3 substrate.

5. The surface acoustic wave filter according to claim 4 , wherein
the oxide crystal substrate is an AT-cut 0-90° X-propagation quartz-crystal substrate, and
the piezoelectric crystal substrate is a 36-45° Y-cut X propagation LiTaO 3 substrate.

6. A method for manufacturing a surface acoustic wave filter, comprising the steps of:
(a) bonding a piezoelectric crystal substrate having a thickness of 0.05 to 0.5 μm over an oxide crystal substrate; and
(b) forming an IDT (Interdigital Transducer) electrode over the piezoelectric crystal substrate, wherein
a thickness of the piezoelectric crystal substrate is 0.05 to 0.5 μm, and
the surface acoustic wave filter uses an odd-order harmonic.

7. The method for manufacturing the surface acoustic wave filter according to claim 6 , wherein the odd-order harmonic is a third harmonic.

8. The method for manufacturing the surface acoustic wave filter according to claim 6 , wherein
a width w of each of electrode fingers of the IDT electrode is 0.2 to 1.5 μm, and
a ratio w/p between the width w and a pitch p of the electrode fingers is 0.7 to 0.9.

9. The method for manufacturing the surface acoustic wave filter according to claim 6 , wherein
the oxide crystal substrate is a quartz-crystal substrate, and
the piezoelectric crystal substrate is a LiTaO 3 substrate.

10. The method for manufacturing the surface acoustic wave filter according to claim 9 , wherein
the oxide crystal substrate is an AT-cut 0-90° X-propagation quartz-crystal substrate, and
the piezoelectric crystal substrate is a 36-45° Y-cut X propagation LiTaO 3 substrate.

Assignees

• Japan Steel Works Ltd

Inventors

• Kishida Kazuhito
• Kakio Shoji
• Mizuno Jun

Classifications

• H03H9/02551

  of quartz substrates · CPC title

• H03H9/02574 Primary

  of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate · CPC title

• H03H3/08

  for the manufacture of resonators or networks using surface acoustic waves · CPC title

• H03H9/145 Primary

  for networks using surface acoustic waves · CPC title

• H03H9/02157

  Dimensional parameters, e.g. ratio between two dimension parameters, length, width or thickness · CPC title