JP2010074840A - Piezoelectric vibrating piece, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibrating piece capable of adjusting a vibration frequency of the piezoelectric vibrating piece while measuring it, securing a great adjusting amount of a vibration frequency and reducing aging in vibration frequency, and to provide a method of manufacturing the same. <P>SOLUTION: A vibration frequency adjusting film 34 is provided on a vibrating electrode of a piezoelectric vibrating piece 30 having a vibrating part 31 for which a central portion is thinned, and an exciting electrode 32 formed in a central portion of the vibrating part. Thus, since a vibration frequency of the piezoelectric vibrating piece can be made lower than a prescribed value at all the time, when adjusting the vibration frequency of the piezoelectric vibrating piece, it is enough only to reduce the thickness of the vibration frequency adjusting film 34. Thus, it is possible to secure a great adjusting amount for the vibration frequency of the piezoelectric vibrating piece and to suppress aging in vibration frequency. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a piezoelectric vibrating piece and a manufacturing method thereof, and more particularly to a piezoelectric vibrating piece having a function of adjusting a vibration frequency and a manufacturing method thereof.

The piezoelectric vibrating piece is roughly composed of a vibrating portion, an excitation electrode, and an extraction electrode. In the piezoelectric vibrating piece having such a configuration, the vibration frequency is determined by the plate thickness of the vibrating portion. The plate thickness of the vibrating portion and the vibration frequency are in an inversely proportional relationship. For example, when the plate thickness of the vibrating portion is 100 μm, the vibration frequency is 1
7.5 MHz, and the vibration frequency when the plate thickness of the vibration part is 50 μm is 35 MHz.

However, as the plate thickness of the vibration part becomes thinner, mechanical polishing becomes more difficult and the strength against vibration becomes weaker and the vibration part is more likely to be damaged. For this reason, the high-frequency piezoelectric vibrating piece is
It is manufactured in a so-called inverted mesa shape in which only the central part of the vibration part is thinly processed and the outer peripheral part is processed thickly as a reinforcing frame. Although thinning of the central part of the vibration part may be performed by mechanical polishing, most of it is performed by wet etching.

8A and 8B are a perspective view showing an example of a general inverted mesa type piezoelectric vibrating piece and A-
It is A sectional view.

In this inverted mesa type piezoelectric vibrating piece 10, only the central portion of the rectangular plate-like vibrating portion 11 is thinly processed,
The outer periphery is processed thick. Excitation electrodes 12 are formed on the front and back surfaces of the central portion of the vibration portion 11, and extraction electrodes 13 for energizing each excitation electrode 12 are formed at one end of the outer peripheral portion.

As a method of manufacturing such a reverse mesa type piezoelectric vibrating piece 10, a plurality of etching patterns are formed on a substrate by photolithography, wet etching is performed up to a predetermined thickness, and a plurality of chips are divided by wet etching or the like to oscillate a vibrating portion. 11. A method is known in which the excitation electrode 12 and the extraction electrode 13 are formed by sputtering or the like to obtain the final inverted mesa type piezoelectric vibrating piece 10.

As a method of adjusting the vibration frequency of the conventional inverted mesa type piezoelectric vibrating piece 10 described above to a predetermined value, a method of reducing the thickness of the vibrating portion 11 by wet etching or the like, and a method of reducing the thickness of the excitation electrode 12 by polishing or the like. Alternatively, a method of increasing by re-sputtering or the like is employed.

However, in the method of reducing the thickness of the vibration part 11 by wet etching or the like, since the etching solution is used, the vibration frequency of the inverted mesa piezoelectric vibrating piece 10 cannot be adjusted to a predetermined value while being measured. For this reason, until the vibration frequency of the inverse mesa piezoelectric vibrating piece 10 reaches a predetermined value, the wet etching of the vibration part 11 and the measurement of the vibration frequency of the reverse mesa piezoelectric vibrating piece 10 must be alternately repeated. There was a drawback that it took a lot of adjustment man-hours.

Further, in the method of reducing the thickness of the excitation electrode 12 by polishing or the like, the thickness of the excitation electrode 12 is extremely thin, so that there is a limit in the adjustment amount of the vibration frequency of the inverted mesa type piezoelectric vibrating piece 10 and the adjustment is made to a predetermined value. There was a drawback that it may not be possible. On the other hand, in the method of increasing the thickness of the excitation electrode 12 by re-sputtering or the like, the thickness of the excitation electrode 12 may become extremely thick, and the vibration frequency is greatly increased in the subsequent use of the inverted mesa type piezoelectric vibrating piece 10. There was a risk of change.

An object of the present invention is to solve the above-mentioned problems, and while adjusting the vibration frequency of the piezoelectric vibrating piece, it is possible to adjust the vibration frequency, and a large amount of adjustment of the vibration frequency can be taken. It is to provide a resonator element and a manufacturing method thereof.

According to a first aspect of the present invention, there is provided a piezoelectric vibrating piece including a vibrating portion having a thin central portion and an excitation electrode formed at the central portion of the vibrating portion, and a vibration frequency adjusting film is provided on the excitation electrode. This is a piezoelectric vibrating piece.

According to the first aspect of the present invention, since the vibration frequency adjusting film is separately formed with an arbitrary thickness on the excitation electrode, the vibration frequency of the piezoelectric vibrating piece can always be lower than a predetermined value. For this reason, when adjusting the vibration frequency of the piezoelectric vibrating piece, it is only necessary to reduce the thickness of the vibration frequency adjusting film, so that it is possible to increase the amount of adjustment of the vibration frequency of the piezoelectric vibrating piece and suppress the change in the vibration frequency over time. can do.

According to a second aspect of the present invention, in the configuration of the first aspect, the vibration frequency adjusting film is a piezoelectric vibrating piece made of a material that can be dry-etched.

According to the second aspect of the invention, in addition to the action of the first aspect of the invention, the vibration frequency of the piezoelectric vibrating piece can be adjusted by gas etching of the vibration frequency adjusting film, so the vibration frequency of the piezoelectric vibrating piece is measured. Can be adjusted.

According to a third aspect of the present invention, in the configuration according to the first or second aspect, the vibrating portion is a piezoelectric vibrating piece made of quartz.

In the third aspect of the invention, in addition to the action of the first or second aspect of the invention, a quartz crystal that is easy to wet-etch is used. Therefore, the vibrating portion can be easily formed into an inverted mesa shape having a thin central portion. Can be formed.

According to a fourth aspect of the present invention, in the method for manufacturing a piezoelectric vibrating piece in which the central portion of the vibration portion is thinned and the excitation electrode is formed at the central portion of the vibration portion, a vibration frequency adjusting film is formed on the excitation electrode. And
Manufacturing a piezoelectric vibrating piece, wherein a voltage is applied to the excitation electrode to vibrate the vibrating portion to measure a vibration frequency, and the vibration frequency adjusting film is etched until the measured vibration frequency reaches a predetermined value. Is the method.

In the fourth aspect of the invention, the vibration frequency adjusting film can be separately formed on the excitation electrode with an arbitrary thickness so that the vibration frequency of the piezoelectric vibrating piece is always lower than a predetermined value. For this reason,
Since it is only necessary to reduce the thickness of the vibration frequency adjustment film while measuring the vibration frequency of the piezoelectric vibrating piece, it is possible to increase the amount of adjustment of the vibration frequency of the piezoelectric vibrating piece and to adjust the vibration frequency quickly and with high accuracy. Can be done. Furthermore, the change with time of the vibration frequency can be suppressed.

A fifth aspect of the present invention is the method of manufacturing a piezoelectric vibrating piece according to the fourth aspect, wherein the vibration frequency adjusting film is formed by sputtering a material that can be dry-etched.

In the invention of claim 5, in addition to the action of the invention of claim 4, a vibration frequency adjusting film capable of adjusting the vibration frequency of the piezoelectric vibrating piece by gas etching can be easily formed.

A sixth aspect of the invention is a method of manufacturing a piezoelectric vibrating piece according to the fourth or fifth aspect, wherein the vibrating portion is formed by etching a crystal.

In the sixth aspect of the invention, in addition to the action of the fourth or fifth aspect of the invention, an inverted mesa type vibration portion having a thin central portion can be easily formed by wet etching.

As described above, according to the present invention, the vibration frequency adjusting film is separately formed on the excitation electrode with an arbitrary thickness using a material that can be dry-etched. Can always be lower. For this reason, at the time of adjusting the vibration frequency, it is only necessary to reduce the thickness of the vibration frequency adjusting film by gas etching, so that the vibration frequency of the piezoelectric vibrating piece can be adjusted while being measured. In addition, a large adjustment amount of the vibration frequency of the piezoelectric vibrating piece can be taken. Furthermore, the change with time of the vibration frequency can be suppressed. Therefore, the piezoelectric vibrating piece with high accuracy, high reliability, and long life can be obtained.

The perspective view which shows the reverse mesa type piezoelectric vibrating piece which is embodiment of the piezoelectric vibrating piece of this invention, and its AA sectional view. The 1st process drawing which shows embodiment of the manufacturing method of the piezoelectric vibrating piece of this invention. The 2nd process drawing which shows embodiment of the manufacturing method of the piezoelectric vibrating piece of this invention. The 3rd process drawing which shows embodiment of the manufacturing method of the piezoelectric vibrating piece of this invention. FIG. 6 is a fourth process chart showing an embodiment of a method for manufacturing a piezoelectric vibrating piece according to the present invention. FIG. 10 is a fifth process chart showing an embodiment of a method for manufacturing a piezoelectric vibrating piece according to the present invention. The figure which shows the relationship between the etching time (sec) by the dry etching apparatus in the manufacturing method of the piezoelectric vibrating piece of this invention, and the measurement vibration frequency change (MHz) by a vibration frequency measuring device. The perspective view which shows an example of the conventional reverse mesa type piezoelectric vibrating piece, and its AA sectional view.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

1A and 1B are a perspective view and a cross-sectional view taken along line AA of an inverted mesa type piezoelectric vibrating piece according to an embodiment of the piezoelectric vibrating piece of the present invention.

In this inverted mesa type piezoelectric vibrating piece 30, only the central portion of the rectangular plate-like vibrating portion 31 is processed to be thin,
The outer periphery is processed thick. Excitation electrodes 32 are formed on the front and back surfaces of the central portion of the vibration portion 31, and extraction electrodes 33 for energizing each excitation electrode 32 are formed at one end of the outer peripheral portion. A vibration frequency adjusting film 34 for adjusting the vibration frequency of the inverted mesa type piezoelectric vibrating piece 30 is formed on a part of the excitation electrode 32, in this example, at a substantially central portion.

The vibration part 31 is made of, for example, quartz that can be easily wet-etched. Other examples include lithium niobate (LiNbO3) and lead zirconate titanate (PZT: Pb (ZrT).
i) It may be created by O3) or the like. As described above, since quartz that can be easily wet-etched is used, the vibrating portion 31 can be easily formed into an inverted mesa shape having a thin central portion.

The excitation electrode 32 and the extraction electrode 33 are formed by laminating, for example, chromium (Cr) and gold (Au) in this order. In addition, for example, the excitation electrode 32 and the extraction electrode 33 are formed by using only chromium (Cr) or only aluminum (Al). May be.

The vibration frequency adjusting film 34 is, for example, silicon oxide (SiO 2) capable of dry etching.
In addition, for example, silicon nitride (Si3N4), zinc oxide (ZnO)
), Diamond-like carbon (C) or the like, or a metal such as aluminum (Al) or titanium (Ti). Here, the vibration frequency adjusting film 34 is made of SiO, Si3 N4, Z
As an etching gas when forming a film with nO, C, Al, Ti, carbon tetrafluoride (
CF4), CF4, chlorine (Cl2), oxygen (O2), Cl2 and CF4 are used.

In this way, the vibration frequency adjusting film 34 is separately formed on a part of the excitation electrode 32 with an arbitrary thickness using a material that can be dry-etched, so that the vibration frequency of the inverted mesa piezoelectric vibrating piece 30 is set to a predetermined value. Can always be lower. For this reason, at the time of adjusting the vibration frequency of the inverted mesa type piezoelectric vibrating piece 30, it is only necessary to reduce the thickness of the vibration frequency adjusting film 34 by gas etching. Can
In addition, a large adjustment amount of the vibration frequency of the inverted mesa type piezoelectric vibrating piece 30 can be taken, and a change with time of the vibration frequency can be suppressed.

In FIG. 1, the vibration frequency adjustment film 34 is smaller than the excitation electrode 32, but the vibration frequency adjustment film 34 may be larger than the excitation electrode 32.

  2-6 is process drawing which shows embodiment of the manufacturing method of the piezoelectric vibrating piece of this invention.

First, an AT-cut substrate (35 degrees 15 minutes rotating Y plate) 21 made of quartz having a size of 30 mm × 30 mm × 0.1 mm is prepared and the surface is polished (FIG. 2A). Then, Cr is sputtered or vapor-deposited on both surfaces of the AT cut substrate 21 to a thickness of 0.05 μm to form a Cr film 22, and Au is further sputtered or vapor-deposited to a thickness of 0.1 μm. A film 23 is formed as a corrosion resistant film of hydrofluoric acid (FIG. 2B). Then, a photoresist is applied to the surface of the Au film 23 and dried to form a photoresist film 24 (FIG. 2C).

Next, a photomask 25 on which an etching pattern for forming the outer shape of the vibration part 31 is drawn is placed on the photoresist film 24, and the etching pattern of the photomask 25 is transferred to the photoresist film 24 by exposure with ultraviolet rays. (FIG. 2D). Then, the photosensitive portion of the photoresist film 24 is developed and removed with a developing solution to expose the Au film 23 (FIG. 2E).
.

Next, the exposed Au film 23 is etched with an etching solution for Au made of, for example, an aqueous solution of iodine (I2) and potassium iodide (KI) to expose the Cr film 22, and the exposed Cr film 22 is further used for Cr. To etch the AT-cut substrate 21 (see FIG.
FIG. 3 (A)). Then, the remaining photoresist film 24 is peeled off (FIG. 3B).
Subsequently, a photoresist is applied again and dried so as to cover all of the exposed AT cut substrate 21 and the remaining Cr film 22 and Au film 23 to form a photoresist film 26 (FIG. 3 (
C)).

Next, a photomask 27 on which an etching pattern for forming the shape of the vibrating portion 31 is drawn is placed on the photoresist film 26, and the etching pattern of the photomask 27 is transferred to the photoresist film 26 by exposure with ultraviolet rays. (FIG. 3D). Then, the photosensitive portion of the photoresist film 26 is developed and removed with a developing solution to expose the AT cut substrate 21 and the Au film 23 (FIG. 4A).

Next, the exposed AT-cut substrate 21 is brought to 50 ° C. with a crystal etching solution made of, for example, a 1: 1 mixture of hydrofluoric acid (HF) and ammonium fluoride (NH 4 F) (buffer hydrofluoric acid). Etching is performed for 1 hour to form a vibrating portion 31 having a size of 3 mm × 2 mm (FIG. 4B). On the other hand, the exposed Au film 23 is etched with the above-described Au etching solution to expose the Cr film 22, and the exposed Cr film 22 is further etched with the above-described Cr etching solution to expose the AT cut substrate 21. (FIG. 4C).

Next, the exposed AT cut substrate 21 is half-etched with the above-described crystal etching solution to form the central portion of the vibrating portion 31 to a thickness of 8 μm (FIG. 4D). Then, the remaining photoresist film 26, the Cr film 22, and the Au film 23 are peeled off. Thereby, the plurality of vibrating portions 31 are completed (FIG. 4E).

Next, a mask 28 on which electrode patterns for forming the excitation electrode 32 and the extraction electrode 33 are drawn is disposed on both surfaces of the vibration part 31 (FIG. 5A), and Cr is thickened on both surfaces of the vibration part 31. Sputtering is performed to a thickness of 20 nm to form a Cr film, and Au is further sputtered to a thickness of 50 nm to form an Au film to form the excitation electrode 32 and the extraction electrode 33 (FIG. 5B). . The vibration frequency at this time is, for example, 166.3 MHz.

Next, a mask 29 on which an adjustment film pattern for forming the vibration frequency adjustment film 34 is drawn is disposed on both surfaces of the vibration part 31 (FIG. 5C), and SiO 2 is formed on each excitation electrode 32 with a thickness. 3
Sputtering is performed until the thickness reaches 00 nm to form a SiO2 film to form a vibration frequency adjusting film 34 (FIG. 5D). The vibration frequency at this time is, for example, 158 MHz.

Next, the vibration part 31 on which the excitation electrode 32, the extraction electrode 33 and the vibration frequency adjustment film 34 are formed is set in the dry etching apparatus 40, and the extraction electrode 33 is connected to the vibration frequency measuring apparatus 5.
Connect to 0. The flow rate of CF4 in the dry etching apparatus 40 is 8 × 10 −5 m.
3 / min, the pressure reached the vibration frequency adjusting film 34 is 0.002 Pa, the pressure after gas introduction is 2 Pa, and the excitation electrode 32 is energized via the extraction electrode 33 by the vibration frequency measuring device 50. The vibration part 31 is vibrated and the vibration frequency is measured. The plasma generation power is set to 100 by the dry etching apparatus 40 until the measurement vibration frequency reaches a predetermined value.
The vibration frequency adjusting film 34 with W and frequency of 13.56 MHz is dry-etched for 100 seconds (FIG. 6A) to obtain the final inverted mesa type piezoelectric vibrating piece 30 (FIG. 6B).

The relationship between the etching time (sec) by the dry etching apparatus 40 and the measurement vibration frequency change (MHz) by the vibration frequency measuring apparatus 50 at this time is shown in FIG. 7 when the plasma generation power by the dry etching apparatus 40 is 100 W. However, when the plasma generation power is 200 W, it becomes steep as shown by the black square in FIG.
Therefore, in order to shorten the etching time (sec) and increase the accuracy of vibration frequency adjustment, the plasma generation power should be increased in the initial stage and the plasma generation power should be decreased in the final stage. Good. The dry etching of the vibration frequency adjusting film 34 may be performed only from one side.

10, 30 Inverted mesa type piezoelectric vibrating piece, 11, 31 vibrating part, 12, 32 excitation electrode, 13
, 33 Connection electrode, 34 Vibration frequency adjustment film, 21 AT cut substrate, 22 Cr film, 2
3 Au film, 24, 26 Photoresist film, 25, 27 Photomask, 28, 29
Mask, 40 Dry etching equipment, 50 Vibration frequency measuring equipment.

Claims (6)

In a piezoelectric vibrating piece including a vibrating portion whose central portion is thinned and an excitation electrode formed in the central portion of the vibrating portion,
A piezoelectric vibrating piece comprising a vibration frequency adjusting film on the excitation electrode. The piezoelectric vibrating piece according to claim 1, wherein the vibration frequency adjusting film is made of a material that can be dry-etched.   The piezoelectric vibrating piece according to claim 1, wherein the vibrating portion is made of quartz. In the manufacturing method of the piezoelectric vibrating piece in which the central portion of the vibrating portion is thinned and the excitation electrode is formed in the central portion of the vibrating portion.
A vibration frequency adjusting film is formed on the excitation electrode,
Applying a voltage to the excitation electrode to vibrate the vibrating part to measure the vibration frequency,
Etching the vibration frequency adjustment film until the measured vibration frequency reaches a predetermined value. The method of manufacturing a piezoelectric vibrating piece according to claim 4, wherein the vibration frequency adjusting film is formed by sputtering a dry-etchable material. The method for manufacturing a piezoelectric vibrating piece according to claim 4, wherein the vibrating portion is formed by wet etching of crystal.

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