JP2000286671A - Piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric vibrator which can be maintained in a highly reliable state by stabilizing a bonded film. SOLUTION: A piezoelectric vibrator is provided with a piezoelectric diaphragm 12 having a piezoelectric diaphragm 11 and a frame-like section 15 which is integrally connected to the base-end section of the piece 1 and surrounds the periphery of the piece 11 and a pair of lid bodies 14 which are bonded to both side faces of the diaphragm 12 through bonding films 17 and airtightly seal the piece 11 without disturbing the vibration of the piece 11. Corrosion of the bonding films 17 is prevented by using metallic films used for anodic bonding as the films 17 and substantially inactivity the exposed sections 20 of the films 17 exposed to the atmosphere by oxidation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrator used for a portable telephone, a portable information terminal and the like.

[0002]

2. Description of the Related Art As a structure of a conventional crystal resonator, for example, as shown in FIG. 5, a crystal resonator plate 63 in which a crystal resonator element 61 and a frame 62 are integrally formed is provided with a crystal resonator. A recess 64 defining a space that does not hinder the vibration of the piece 61
For example, there is known a crystal resonator which has a structure in which a pair of lids 65 having a structure is bonded via a bonding film 66 made of a metal material, for example.

[0003]

However, in the above-described structure, the bonding film 66 is exposed to the air near the end of the quartz vibrating plate 63, that is, corrosion occurs when the bonding film 66 comes into contact with the air. As a result, there is a problem that the bonding between the quartz vibrating plate 63 and the lid 65 becomes unstable. Further, due to such a problem, it is difficult to obtain the reliability of the crystal unit.

[0004] In view of such circumstances, an object of the present invention is to provide a piezoelectric vibrator capable of stabilizing a bonding film and maintaining high reliability.

[0005]

According to a first aspect of the present invention, there is provided a piezoelectric vibrating reed having a frame-like portion integrally connected to a base end thereof and surrounding the piezoelectric vibrating reed. And a pair of lids that are bonded to both sides of the piezoelectric vibrating plate via bonding films and hermetically seal the piezoelectric vibrating reed without hindering the vibration of the piezoelectric vibrating reed. A piezoelectric film, wherein the bonding film is a metal film used for anodic bonding, and an exposed portion exposed to the atmosphere is an inactive portion substantially inactivated by oxidation. In the vibrator.

A second aspect of the present invention is the piezoelectric vibrator according to the first aspect, wherein the inactive portion is formed by subjecting the exposed portion to an oxidizing plasma treatment.

A third aspect of the present invention is the piezoelectric vibrator according to the first aspect, wherein the inactive portion is formed by passivating the exposed portion.

According to a fourth aspect of the present invention, in the piezoelectric vibrator according to the second or third aspect, the exposed portion is inactivated after removing a natural oxide film in advance. is there.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the bonding film is made of a material selected from the group consisting of Cr, Al and alloys thereof. In the vibrator.

According to the present invention, the corrosion of the bonding film bonded to the lid is prevented, and the reliability of the piezoelectric vibrator can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is an exploded perspective view of a piezoelectric vibrator according to one embodiment of the present invention, and FIG. 2 is a sectional view thereof.

The piezoelectric vibrator of this embodiment is, for example, a crystal vibrator 10 having a tuning-fork type crystal vibrating piece 11 made of quartz (SiO ₂ ). As shown in FIG. The crystal vibration plate 12 includes a pair of lids 14 bonded to both surfaces of the crystal vibration plate 12 to hermetically seal the crystal vibration piece 11 in a viable state.

The quartz vibrating plate 12 of the present embodiment has a tuning-fork type quartz vibrating piece 11 and a frame 15 which is integrally connected to a base end of the quartz vibrating piece 11 and surrounds the quartz vibrating piece 11.

The pair of lids 14 are formed of, for example, soda lime glass or silicon, and each has a concave portion defining a space in a region corresponding to the crystal vibrating piece 11 so as not to hinder the vibration of the crystal vibrating piece 11. 13.

Further, as shown in FIG.
In order to vibrate the quartz vibrating reed 11, an excitation electrode film 16 is formed on both front and back surfaces and side surfaces thereof, and a region corresponding to the frame portion 15 is made of the same material as the excitation electrode film 16. Is provided with a bonding film 17 which is an actual bonding portion with the above. Then, the bonding film 17 and the lid 14 are
As will be described in detail later, the quartz vibrating plate 12 and the lid 14 are joined by so-called anodic joining.

The excitation electrode film 16 extends to the end of the quartz plate 12 and is connected to the bonding film 17. In the present embodiment, the electrode 16a which is one of the poles of the excitation electrode film 16 is used.
Is connected to the lead electrode 18a via the terminal connection bonding film 17a.
The electrode 16b serving as the other pole is extended to the terminal connection bonding film 17b through an electrode provided on the side surface of the crystal resonator element 11, and is connected to the lead electrode 18b. The material of the lead electrode 18 is not particularly limited, but is not easily oxidized because it is exposed to the atmosphere.
For example, it is preferable to use gold (Au) or the like.

Further, as will be described later in detail, in the present embodiment, the exposed portion 20 exposed to the atmosphere near the outer end of the bonding film 17 is forcibly oxidized to an oxide, so that it is substantially formed. The inertness prevents corrosion of the bonding film 17.

The bonding films 17 on both sides of the quartz plate 12
Are formed so as to surround the recess 13 on both sides, and the recess 13 is hermetically sealed after joining.

Hereinafter, a manufacturing process of such a crystal resonator will be described. FIG. 3 is a perspective view illustrating a manufacturing process of the piezoelectric vibrator according to the present embodiment.

First, as shown in FIG. 3A, a quartz crystal wafer serving as a quartz vibrating plate 12 is etched to form a quartz vibrating piece 11 which is an actual driving unit and a frame 15 surrounding the periphery thereof.
And are formed.

Next, as shown in FIG. 3B, a metal film 20 is formed on both sides of the quartz vibrating plate 12 over substantially the entire surface by sputtering or the like. The metal film 20 is a film that forms the excitation electrode film 16 for vibrating the crystal resonator element 11 and the bonding film 17 that is an actual bonding portion with the lid 14. The material is not particularly limited. , Aluminum (Al), chromium (Cr), or the like is preferably used. In the present embodiment, aluminum is used.

Next, as shown in FIG.
By patterning 0, a bonding film 17 is formed over the entire periphery of the portion corresponding to the excitation electrode film 16 and the frame 15 around the excitation electrode film 16.

Next, as shown in FIG. 4, the bonding film 1 is placed on both sides of the crystal unit 10 in an inert gas or in a vacuum.
The lids 14 are joined by anodic bonding via the respective members 7, and the quartz-crystal vibrating piece 11 is hermetically sealed in the recesses 13 of the pair of lids 14. At this time, each member is heated to a temperature lower than the softening point of the glass, for example, 100 ° C. to 150 ° C.,
It is preferable that a DC voltage of 3 to 5 kV is applied by the DC power supply 30 to the bonding film 17 and the lid 14 on each surface of the quartz plate 12 so that the lid 14 is a cathode.
For example, in this embodiment, each member was heated to about 120 ° C. and a DC voltage of about 3.5 kV was applied.

As described above, under the above conditions, the bonding film 1
The anodic bonding of the quartz vibrating plate 12 and the lid 14 through the bonding member 7 allows the bonding film 17 and the lid 14 to be satisfactorily bonded. That is, the quartz vibrating plate 12 and the lid 14 are satisfactorily bonded via the bonding film 17, and no cracks or the like occur.

Here, the coefficient of thermal expansion of quartz, which is the material of the quartz plate 12, is 13.7 ppm / ° C., and the coefficient of thermal expansion of soda-lime glass used as the lid 14 is 8.5.
ppm / ° C. That is, the difference between these coefficients of thermal expansion is relatively large at 5.2 ppm / ° C., and it is difficult to perform anodic bonding under conventionally known conditions. However, as in the present embodiment, the effect of the thermal expansion coefficient is suppressed to a very small value by performing the anodic bonding by setting the bonding temperature to a low temperature of about 100 to 150 ° C. and applying a relatively high DC voltage of about 3 to 5 kV. Thus, even members having a relatively large difference in coefficient of thermal expansion can be satisfactorily joined.

In practice, a quartz wafer on which a plurality of quartz vibrating pieces 11 and the like are formed, and a lid in which a plurality of concave portions 13 are formed corresponding to these quartz vibrating pieces 11 to form a plurality of lids 14. After joining with the body-forming substrate, it is cut at a predetermined position to form an individual crystal resonator.

Further, when the crystal resonator is formed by the above-described steps, thereafter, in the present embodiment, the bonding film 17 is formed.
Is forcibly oxidized.

This oxidation method is not particularly limited. For example, in this embodiment, the plasma oxidation was performed by using a plasma asher for photoresist using oxygen plasma while changing predetermined conditions in plasma. As a result, the exposed portion 20 was made a desired oxide. At this time, it is preferable to previously remove a portion that has already been oxidized by the exposed portion 20 coming into contact with the atmosphere. This allows
The exposed portion 20 can be made of a stronger oxide, and the corrosion of the bonding film 17 can be reliably prevented. That is, the bonding film 17 inside the exposed portion 20 does not corrode.

As described above, in the present embodiment, the bonding film 17
Is forcibly oxidized at the exposed portion 20 exposed to the atmosphere. Thus, the oxidized exposed portion 20 can prevent corrosion of other portions and maintain high reliability. Further, by oxidizing the exposed portion 20, there is no need to form, for example, a protective film for shielding the exposed portion 20 from the atmosphere, and the manufacturing process can be simplified.

In this embodiment, the bonding film 17 is formed of aluminum. However, the present invention is not limited to this. For example, the bonding film may be formed of chromium or chromium and silicon. Further, in the present embodiment, the oxidation treatment is performed in the plasma, but the invention is not limited thereto, and the oxidation treatment may be performed in ozone.

Further, as described above, in the present embodiment, the method of oxidizing the exposed portion 20 in a gas is used. However, the present invention is not limited to this. For example, the exposed portion 20 may be oxidized in a liquid. Is also good. For example, after forming the piezoelectric vibrator, it may be made substantially inactive by immersing it in a nitric acid solution or the like to passivate the exposed portion 20.
However, when silicon is used for the bonding film 17,
It is not suitable because silicon is etched by a nitric acid solution, and can be suitably used, for example, when the bonding film 17 is formed of chromium or the like.

According to such a method, the bonding film 17 can be stabilized, and a piezoelectric vibrator having high reliability can be formed.

[0034]

As described above, according to the present invention, the exposed portion of the bonding film for bonding the piezoelectric vibrating plate and the lid, which is exposed to the atmosphere, is made to be an oxide which is forcibly oxidized to be substantially inert. . Thereby, corrosion of the bonding film is prevented, and the piezoelectric vibrating plate and the lid can be securely bonded via the bonding film. That is, there is an effect that a piezoelectric vibrator with improved reliability can be formed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a crystal resonator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a crystal resonator according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a step of manufacturing the piezoelectric vibrator according to the present invention.

FIG. 4 is a schematic view illustrating a manufacturing process of the piezoelectric vibrator according to the present invention.

FIG. 5 is a sectional view showing another example of the piezoelectric vibrator according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Quartz crystal resonator 11 Quartz crystal vibrating piece 12 Quartz crystal vibrating plate 13 Concave part 14 Lid 15 Frame-like part 16 Excitation electrode film 17 Bonding film 20 Exposed part

Claims (5)

[Claims] A piezoelectric vibrating plate having a piezoelectric vibrating reed and a frame-shaped portion integrally connected to a base end portion thereof and surrounding the piezoelectric vibrating reed, and bonding films are formed on both sides of the piezoelectric vibrating plate. A piezoelectric vibrator having a pair of lids hermetically sealed without interfering with the vibration of the piezoelectric vibrating piece without interfering with the vibration of the piezoelectric vibrating piece, wherein the bonding film is a metal film used for anodic bonding, and A piezoelectric vibrator, wherein an exposed part exposed to the atmosphere is an inactive part substantially inactivated by oxidation. 2. The piezoelectric vibrator according to claim 1, wherein the inactive portion is formed by subjecting the exposed portion to an oxidizing plasma process. 3. The piezoelectric vibrator according to claim 1, wherein the inactive portion is formed by passivating the exposed portion. 4. The piezoelectric vibrator according to claim 2, wherein the exposed portion is inactivated after a natural oxide film has been removed in advance. 5. The piezoelectric vibrator according to claim 1, wherein said bonding film is made of a material selected from the group consisting of Cr, Al, and alloys thereof.