Surface acoustic wave element, surface acoustic wave device using the same, and method for manufacturing surface acoustic wave element and surface acoustic wave device

• US 20030020376A1
• Filed: 07/26/2002
• Published: 01/30/2003
• Est. Priority Date: 07/26/2001
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Watanabe, Masanobu, Sakaguchi, Kenji, Takatori, Mitsushi
• Granted Patent: US 6,911,762 B2
• Time in Patent Office: Days
• US Class Current: 310/364
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/0508 being stacked
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 24/03 Manufacturing methods
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/15153 the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H01L 2924/15165 Monolayer substrate
• CPC Class Codes: H01L 2924/15787 Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/16195 Flat cap [not enclosing an internal cavity]
• CPC Class Codes: H03H 9/059 consisting of mounting pads or bumps
• CPC Class Codes: H03H 9/1071 the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the SAW device

Abstract

A surface acoustic wave device includes a surface acoustic wave element, a packaging case, and a packaging electrode. The surface acoustic wave element has a piezoelectric substrate, an interdigital transducer, an electrode pad, an intermediate electrode, an upper electrode, and a bump electrode. The intermediate electrode is preferably made of NiCr including about 30 weight percent of Cr. The electrode pad and upper electrode are made of Al. The bump electrode is press-bonded to the packaging electrode with an ultrasonic wave or heat applied to the bump electrode. The resulting surface acoustic wave device has excellent characteristics and the surface acoustic wave element is not removed or peeled from the packaging case during a drop test.

Claims

1. A surface acoustic wave element comprising:

a piezoelectric substrate;

an interdigital transducer disposed on a main surface of the piezoelectric substrate;

an electrode pad disposed on the main surface of the piezoelectric substrate;

an intermediate electrode disposed on the electrode pad;

an upper electrode disposed on the intermediate electrode; and

a bump electrode disposed on the upper electrode;

wherein

the intermediate electrode is a metal layer having a tensile stress that is lower than approximately 10⁶ Pa and an adhesion strength to one of the electrode pad and the upper electrode that is higher than approximately 10⁷ Pa.

2. A surface acoustic wave element according to claim 1, wherein the intermediate electrode includes NiCr containing about 15 to about 30 weight percent of Cr.

3. A surface acoustic wave element according to claim 1, wherein the intermediate electrode includes NiCr containing about 18 to about 28 weight percent of Cr.

4. A surface acoustic wave clement according to claim 2, wherein the NiCr is deposited by evaporation.

5. A surface acoustic wave element according to claim 1, wherein the upper electrode includes one of Al and an alloy containing Al.

6. A surface acoustic wave device comprising:

a packaging case comprising a packaging electrode;

a cover for hermetically sealing the packaging case; and

a surface acoustic wave element including;

a piezoelectric substrate;

an interdigital transducer disposed on a main surface of the piezoelectric substrate;

an electrode pad disposed on the main surface of the piezoelectric substrate;

an intermediate electrode disposed on the electrode pad;

an upper electrode disposed on the intermediate electrode; and

a bump electrode disposed on the upper electrode and connected to the packaging electrode;

wherein

the intermediate electrode is a metal layer having a tensile stress that is lower than approximately 10⁶ Pa and an adhesion strength to one of the electrode pad and the upper electrode that is higher than approximately 10⁷ Pa.

7. A surface acoustic wave device according to claim 6, wherein the intermediate electrode includes NiCr containing about 15 to about 30 weight percent of Cr.

8. A surface acoustic wave device according to claim 6, wherein the intermediate electrode includes NiCr containing about 18 to about 28 weight percent of Cr.

9. A surface acoustic wave device according to claim 7, wherein the NiCr is deposited by evaporation.

10. A surface acoustic wave device according to claim 6, wherein the upper electrode includes at least one of Al and an alloy containing Al.

11. A method for manufacturing a surface acoustic wave element, comprising the steps of:

patterning an interdigital transducer and an electrode pad on a main surface of a piezoelectric substrate;

applying a resist to cover the electrode pad except a portion thereof and the interdigital transducer;

forming an intermediate electrode of a metal layer on the portion of the electrode pad using the resist as a mask;

forming an upper electrode on the intermediate electrode using the resist as a mask;

removing the resist; and

forming a bump electrode on the upper electrode;

wherein

the metal layer has a tensile stress that is lower than approximately 10⁶ Pa and an adhesion strength to one of the electrode pad and the upper electrode that is higher than approximately 10⁷ Pa.

12. A method for manufacturing a surface acoustic wave element according to claim 11, wherein the intermediate electrode includes NiCr containing about 15 to about 30 weight percent of Cr.

13. A method for manufacturing a surface acoustic wave element according to claim 11, wherein the intermediate electrode includes NiCr containing about 18 to about 28 weight percent of Cr.

14. A method for manufacturing a surface acoustic wave element according to claim 12, wherein the NiCr is deposited by evaporation.

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

patterning an interdigital transducer and an electrode pad on a main surface of a piezoelectric substrate;

applying a resist to cover the electrode pad except a portion thereof and the interdigital transducer;

forming an intermediate electrode of a metal layer on the portion of the electrode pad using the resist as a mask;

forming an upper electrode on the intermediate electrode using the resist as a mask;

removing the resist;

forming a bump electrode on the upper electrode; and

pressing the bump electrode to a packaging electrode of a packaging case while applying an ultrasonic wave or heat such that the bump electrode is bonded to the packaging electrode;

wherein

the metal layer has a tensile stress that is lower than approximately 10⁶ Pa and an adhesion strength to one of the electrode pad and the upper electrode that is higher than approximately 10⁷ Pa.

16. A method for manufacturing a surface acoustic wave device according to claim 15, wherein the intermediate electrode includes NiCr containing about 15 to about 30 weight percent of Cr.

17. A method for manufacturing a surface acoustic wave device according to claim 15, wherein the intermediate electrode includes NiCr containing about 18 to about 28 weight percent of Cr.

18. A method for manufacturing a surface acoustic wave device according to claim 16, wherein the NiCr is deposited by evaporation.