Surface acoustic wave device and manufacturing method therefor, and communications equipment

• US 8,097,178 B2
• Filed: 03/25/2008
• Issued: 01/17/2012
• Est. Priority Date: 08/27/2004
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Obara, Ikuo, Makibuchi, Daisuke, Muraoka, Kunihiko, Iioka, Kiyohiro
• Primary Examiner(s): CULBERT, ROBERTS P
• Application Number:
  US12/055,097
• Publication Number:
  US 20080179278A1
• Time in Patent Office: 1,393 Days
• Field of Search: 216/58, 310/313.R, 310/313.B
• US Class Current: 216/58
• CPC Class Codes: H03H 3/08 for the manufacture of resonators or networks using surface acoustic waves
• CPC Class Codes: H03H 9/02614 Treatment of substrates, e.g. curved, spherical, cylindrical substrates ensuring closed round-about circuits for the acoustical waves
• CPC Class Codes: H03H 9/02921 Measures for preventing electric discharge due to pyroelectricity

Abstract

A surface acoustic wave device configured by forming an oxide layer 2 on a piezoelectric substrate 1 composed of a lithium tantalate single crystal or a lithium niobate single crystal and having weak pyroelectric properties having a lower oxygen content than a stoichiometric composition ratio, and forming thereon an IDT electrode 3. There is no static destruction of a minute electrode due to the pyroelectric effect of the piezoelectric substrate having weak pyroelectric properties, and frequency characteristics are not degraded.

Claims

1. A method of manufacturing a surface acoustic wave device, comprising the steps of:

forming an oxide layer in a surface of a piezoelectric substrate, wherein the piezoelectric substrate has weak pyroelectric properties, is composed of a lithium tantalate single crystal or a lithium niobate single crystal, and has an oxygen content lower than a stoichiometric composition ratio; and

forming an IDT electrode on a surface of the oxide layer on the piezoelectric substrate.

2. The method according to claim 1, wherein

the step of forming the IDT electrode comprises forming a metal film on the surface of the piezoelectric substrate, and

dry-etching the formed metal film, and

the oxide layer, excluding a region between electrode fingers of the IDT electrode, is removed by the dry-etching.

3. The method according to claim 2, further comprising the step of forming a region having an oxygen content increased by being further oxidized after the IDT electrode is formed.

4. A method of manufacturing a surface acoustic wave device, comprising the steps of:

forming an IDT electrode on a surface of a piezoelectric substrate, wherein the piezoelectric substrate has weak pyroelectric properties, and is composed of a lithium tantalate single crystal or a lithium niobate single crystal; and

forming an oxide layer on the surface of the piezoelectric substrate with the IDT electrode formed thereon by using the IDT electrode as a mask,

wherein a conductivity of the oxide layer is in a range from 1×

10<sup>−

12</sup>/Ω

cm to 1×

10<sup>−

10</sup>/Ω

cm.