JP2001251154A - Manufacture of piezoelectric vibrating reed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a piezoelectric vibrating reed by which the oscillation frequency of a piezoelectric vibrating reed is adjusted to a target frequency with high accuracy. SOLUTION: In the case of manufacturing a piezoelectric vibrating reed 30 in which the center of a vibrating part 31 is made of a thin plate, first electrodes 32 are formed at one part of the vibrating part, oscillation frequency is measured by applying voltage to the first electrodes to vibrate the vibrating part, part of the center of the vibrating part is removed on the basis of the measured oscillation frequency obtained by measurement so as to make the vibration of the vibrating part the target frequency, and a second electrode 33 is formed at the center of the vibrating part. In this way, it is possible to adjust the oscillation frequency of the vibrating part to a target frequency with high accuracy because the oscillation frequency is directly measured to modify the vibrating part in a manufacturing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a piezoelectric vibrating reed, and more particularly to a method for manufacturing a piezoelectric vibrating reed that can adjust a vibration frequency with high accuracy.

[0002]

2. Description of the Related Art A piezoelectric vibrating reed is generally constituted by a vibrating portion, an excitation electrode and an extraction electrode. The vibration frequency of the piezoelectric vibrating reed having such a configuration is determined by the thickness of the vibrating portion. The thickness of the vibrating part and the vibration frequency are in inverse proportion,
For example, when the thickness of the vibrating part is 100 μm, the vibration frequency is 17.5 MHz, and when the thickness of the vibrating part is 50 μm, the vibration frequency is 35 MHz.

However, as the thickness of the vibrating portion becomes thinner,
Mechanical polishing becomes difficult, the strength against vibration is weakened, and the vibrating part is easily damaged. For this reason, the high-frequency piezoelectric vibrating reed is manufactured in a so-called inverted mesa shape in which only the central portion of the vibrating portion is thinned and the outer peripheral portion is thickened as a reinforcing frame. The thinning of the central portion of the vibrating portion may be performed by mechanical polishing, but is mostly performed by wet etching.

FIGS. 10A and 10B are a perspective view showing an example of a general inverted-mesa type piezoelectric vibrating piece and a sectional view taken along line AA of FIG.

The inverted-mesa type piezoelectric vibrating reed 10 has a rectangular plate-shaped vibrating portion 11 which is thinly processed only at its central portion and whose outer peripheral portion is thickly processed. Excitation electrodes 12 are formed on the front and back surfaces at the center of the vibrating portion 11, and a lead electrode 13 for energizing each excitation electrode 12 is formed at one end of the outer peripheral portion.

As a method of manufacturing such an inverted mesa type piezoelectric vibrating reed 10, a plurality of etching patterns are formed on a substrate by photolithography, wet-etched to a predetermined thickness, and a plurality of chips are divided by wet etching or the like. To form the vibrating section 11. Then, 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.

[0007]

As a method for adjusting the vibration frequency of the above-mentioned conventional inverted-mesa type piezoelectric vibrating reed 10 to a target vibration frequency, the thickness of the vibration portion 11 is measured and converted into the vibration frequency. Thus, a method of wet-etching the thickness of the vibrating portion 11 until the target vibration frequency is obtained, and a method of measuring the vibration frequency by vibrating the vibrating portion 11 with a non-contact dummy electrode, thereby achieving the target vibration frequency. A method of wet-etching the thickness of the vibrating portion 11 to the extent possible and a method of reducing the thickness of the excitation electrode 12 by polishing or the like to obtain a target vibration frequency are adopted.

However, in the method of measuring the thickness of the vibrating section 11 and converting it into a vibration frequency, it is difficult to measure the thickness because the thickness of the vibrating section 11 is thin. There is a disadvantage that there is a risk of being damaged. In the method of measuring the vibration frequency by vibrating the vibrating part 11 by the non-contact dummy electrode, it is difficult to measure the vibration frequency in the case of a material having a large crystal impedance. There is a drawback that the portion 11 may be damaged. In the method in which the thickness of the excitation electrode 12 is reduced by polishing or the like, since the thickness of the excitation electrode 12 is extremely thin, the amount of adjustment of the oscillation frequency of the inverted mesa piezoelectric vibrating piece 10 is limited, and the target oscillation frequency is reduced. There was a drawback that adjustment might not be possible.

It is an object of the present invention to provide a method of manufacturing a piezoelectric vibrating reed in which the above-mentioned problems can be solved and the vibration frequency of the piezoelectric vibrating reed can be adjusted to a target vibration frequency with high accuracy.

[0010]

According to a first aspect of the present invention, there is provided a method of manufacturing a piezoelectric vibrating reed in which a central portion of a vibrating portion is thinned, wherein a first electrode is formed on a part of the vibrating portion, First
A voltage is applied to the electrodes to vibrate the vibrating section to measure a vibration frequency, and a central portion of the vibrating section is measured based on a measured vibration frequency obtained by the measurement so that the vibration of the vibrating section has a set vibration frequency. And forming a second electrode at the center of the vibrating portion.

According to the first aspect of the present invention, the current value of the vibration frequency of the vibrating portion is actually measured by the first electrode to determine a difference from the target vibration frequency, and the thickness of the vibrating portion at which the difference becomes zero is determined. Ask. Then, the vibrating portion is processed so as to have this thickness, and then a second electrode is formed to obtain a final piezoelectric vibrating piece. As described above, since the vibration frequency of the vibrating portion is directly measured in the manufacturing process to correct the vibrating portion, the vibration frequency can be adjusted to the target vibration frequency with high accuracy.

According to a second aspect of the present invention, there is provided a method for manufacturing a piezoelectric vibrating reed according to the first aspect, wherein the first electrode is formed from a central portion to an outer peripheral portion of the vibrating portion.

According to the second aspect of the invention, in addition to the operation of the first aspect, the first portion extends from the central portion to the outer peripheral portion of the vibrating portion.
Since the first electrode is formed, the first electrode can be used as a lead electrode, and an increase in the number of steps can be suppressed.

According to a third aspect of the present invention, there is provided a method of manufacturing a piezoelectric vibrating piece according to the first or second aspect, wherein a central portion of the vibrating portion is removed by dry etching.

According to the third aspect of the present invention, in addition to the operation of the first or second aspect of the present invention, since the central portion of the vibrating portion can be removed by gas etching, the operation can be simplified. Man-hours can be reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 6 are process diagrams showing an embodiment of a method for manufacturing a piezoelectric vibrating reed according to the present invention.

First, the size is 30 mm × 30 mm × 0.
An AT-cut substrate (a Y-plate rotating at 35 ° 15 minutes) 21 made of 1 mm quartz is prepared and its surface is polished (FIG. 1A). Then, Cr is sputtered or vapor-deposited on both sides 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 to form Au. The film 23 is formed into a corrosion-resistant film of hydrofluoric acid (FIG. 1)
(B)). Then, a photoresist is applied to the surface of the Au film 23 and dried to form a photoresist film 24 (FIG. 1C).

Next, the vibrating portion 3 is formed on the photoresist film 24.
1 (see FIG. 3), a photomask 25 on which an etching pattern for forming an outer shape is drawn is arranged, and is exposed to ultraviolet rays to transfer the etching pattern of the photomask 25 to the photoresist film 24 (FIG. 1D )). And
The exposed portion of the photoresist film 24 is developed and removed with a developing solution to expose the Au film 23 (FIG. 1E).

Next, the exposed Au film 23 is formed of an aqueous solution of, for example, iodine (I2) and potassium iodide (KI).
The Cr film 22 is exposed by etching with an etching solution for u, and the exposed Cr film 22 is further etched with an etching solution for Cr to expose the AT cut substrate 21 (FIG. 2A). Then, the remaining photoresist film 24 is peeled off (FIG. 2B). Then, exposed A
T-cut substrate 21 and remaining Cr film 22 and Au film 2
Then, a photoresist is applied again so as to cover all the layers 3 and dried to form a photoresist film 26 (FIG. 2C).

Next, the vibrating part 3 is formed on the photoresist film 26.
A photomask 27 on which an etching pattern for forming the shape 1 is drawn is arranged, and is exposed to ultraviolet rays to transfer the etching pattern of the photomask 27 to the photoresist film 26 (FIG. 2D). Then, the exposed 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. 3).
(A)).

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

Next, the exposed AT-cut substrate 21 is half-etched with the above-described etching solution for quartz to form a central portion of the vibrating portion 31 to a thickness of 8 μm (FIG. 3).
(D)). Then, the remaining photoresist film 26
Then, the Cr film 22 and the Au film 23 are peeled off. Thus, the plurality of vibrating sections 31 are completed (FIG. 3E).

Next, the first electrodes 3 are provided on both surfaces of the vibrating section 31.
The mask 28a on which the electrode pattern 32 for forming the second electrode 2 is drawn is arranged (FIG. 4A), and Cr is sputtered on both surfaces of the vibrating portion 31 until the thickness becomes 20 nm.
A film is formed, and Au is sputtered to a thickness of 50 nm to form an Au film, which is used as the first electrode 32 (FIG. 4B).

Next, the first electrode 32 is connected to the vibration frequency measuring device 40, and the first electrode 32 is energized to
Is vibrated and the vibration frequency is measured. The vibration frequency at this point is, for example, 166.3 MHz. And
The difference between the measured vibration frequency and the target vibration frequency is obtained, and the thickness of the vibrating portion 31 at which the difference becomes zero is obtained (FIG. 5A).

Next, the vibrating section 31 is set in a dry etching apparatus 50, and masks 29 for dry-etching the vibrating section 31 are arranged on both surfaces of the vibrating section 31. Then, CF4 is supplied into the dry etching apparatus 50 at a flow rate of 8
× 10 −5 m 3 / min, the pressure reaching the vibrating section 31 is 0.002 Pa, the pressure after introducing the gas is 2 Pa, the plasma generation power is 100 W, and the frequency is 1
The vibration part 31 is dry-etched at 3.56 MHz for 100 seconds (FIG. 5B).

At this time, the dry etching apparatus 50
Time (sec) and vibration frequency change (M
7), the plasma generation power by the dry etching apparatus 50 is 100 W, but is moderate as shown by the black circle in FIG.
When it is 0 W, it becomes steep as shown by a black square in FIG. Therefore, when the etching time (sec) is to be shortened and the vibration frequency adjustment is to be performed with high accuracy, the plasma generation power should be increased in the initial stage, and the plasma generation power should be decreased in the final stage. Good.

Next, the second electrodes 3 are provided on both surfaces of the vibrating section 31.
Mask 2 on which an electrode pattern for forming 3 is drawn
8b (FIG. 6 (A)), and Cr
Is sputtered to a thickness of 10 nm to form a Cr film, and Au is sputtered to a thickness of 20 nm to form an Au film to form a second electrode 33 (FIG. 6B). .

Through the above steps, a final inverted mesa type piezoelectric vibrating piece 30 as shown in FIG. 8 can be obtained. In this inverted-mesa type piezoelectric vibrating piece 30, only the central portion of the rectangular plate-shaped vibrating portion 31 is thinly processed, and the outer peripheral portion is thickly processed. A first electrode 32 is formed on the front and back surfaces of the vibrating portion 31 from the center to one end of the outer peripheral portion.
A second electrode 33 partially connected to the first electrode 62 is formed on the front and back surfaces of the center of the first electrode. First electrode 3
2 functions as a lead electrode for supplying electricity to the vibrating part 31, and the second electrode 33 functions as an exciting electrode for exciting the vibrating part 31.

The vibrating part 31 is made of, for example, quartz, but may be made of, for example, lithium niobate (LiNbO 3).
And lead zirconate titanate (PZT: Pb (ZrTi) O
3) or the like. For the first electrode 32 and the second electrode 33, for example, chromium (Cr) and gold (Au) are stacked in this order. The first electrode 32 is formed so as to be thicker than the second electrode 33.

The shape of the inverted-mesa type piezoelectric vibrating piece manufactured according to the present embodiment is not limited to the shape shown in FIG.
0, the first electrode 62 is formed on the front and back surfaces from the outer edge at the center of the vibrating portion 31 to one end of the outer periphery,
The first electrode 6 is provided on the front and back surfaces inside the central portion of the vibrating portion 31.
A second electrode 63 that is partially connected to the second electrode 63 is formed.

According to such a shape, the first electrode 62
And the vibration frequency when the vibrating section 61 is vibrated by applying a current to the vibration section 61 can be measured more accurately.

[0033]

As described above, according to the present invention, the first electrode measures the current vibration frequency of the vibrating portion and determines the difference from the target vibration frequency. Find the thickness of the part, process the vibrating part to this thickness,
Thereafter, a second electrode is formed to obtain a final piezoelectric vibrating reed. Therefore, the vibration frequency of the vibrating portion can be directly measured in the manufacturing process to correct the vibrating portion, so that the vibration frequency can be adjusted to the target vibration frequency with high accuracy.
Furthermore, since there is no direct contact with the vibrating part, it is possible to prevent the connection part from being damaged.

[Brief description of the drawings]

FIG. 1 is a first process chart showing an embodiment of a method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 2 is a second process chart showing an embodiment of the method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 3 is a third process chart showing an embodiment of the method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 4 is a fourth process diagram showing an embodiment of the method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 5 is a fifth process chart showing an embodiment of the method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 6 is a sixth process chart showing an embodiment of the method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 7 is a view showing a relationship between an etching time (sec) by a dry etching apparatus and a change in vibration frequency (MHz) in the method for manufacturing a piezoelectric vibrating reed according to the present invention.

FIG. 8 is a perspective view showing an inverted-mesa type piezoelectric vibrating reed manufactured by the method for manufacturing a piezoelectric vibrating reed of the present invention.

FIG. 9 is a perspective view showing another inverted-mesa type piezoelectric vibrating reed manufactured by the method for manufacturing a piezoelectric vibrating reed of the present invention.

FIG. 10 is a perspective view showing an example of a conventional inverted-mesa type piezoelectric vibrating reed, and a cross-sectional view taken along line AA thereof.

[Explanation of symbols]

 10, 30, 60 Inverted mesa type piezoelectric vibrating piece 11, 31, 61 Vibrating part 12 Exciting electrode 13 Connection electrode 32, 62 First electrode 33, 63 Second electrode 21 AT cut substrate 22 Cr film 23 Au film 24, Reference Signs 26 Photoresist film 25, 27 Photomask 28a, 28b, 29 Mask 40 Vibration frequency measuring device 50 Dry etching device

Claims (3)

[Claims] 1. A method of manufacturing a piezoelectric vibrating reed in which a central portion of a vibrating portion is thinned, wherein a first electrode is formed in a part of the vibrating portion, and a voltage is applied to the first electrode to cause the vibration. Vibrating the part to measure a vibration frequency; removing a central part of the vibrating part based on a measured vibration frequency obtained by measurement so that the vibration of the vibrating part becomes a set vibration frequency; Forming a second electrode at the center of the piezoelectric vibrating reed. 2. The method according to claim 1, wherein the first electrode is formed from a central portion to an outer peripheral portion of the vibrating portion. 3. The method of manufacturing a piezoelectric vibrating reed according to claim 1, wherein a central portion of the vibrating portion is removed by dry etching.