JP2004187097A - Manufacturing method of piezoelectric vibrator, piezoelectric vibrator, and resonator using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a compact and high frequency piezoelectric vibrator, a piezoelectric vibrator, and a resonator using this. <P>SOLUTION: In this manufacturing method of the piezoelectric vibrator 14, a vibrating part 26 is formed by etching a piezoelectric substrate 20. As the vibrating part 26 is piezoelectric, it can be vibrated by applying an alternating current between a pair of electrodes 22 placed with the vibrating part 26 between them. In this method for the piezoelectric vibrater 14, as a minute vibrating part 26 can be formed by etching which enables precise removal processing, a more compact and higher frequency piezoelectric vibrator 14 can be made compared to that made by the existing manufacturing method which forms the vibrating part 26 by grinding. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a piezoelectric vibrator, a piezoelectric vibrator, and a resonator using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a resonator using a crystal resonator has been known as one of resonators used for an impedance element. This crystal resonator has a configuration in which a pair of electrode films are attached to both surfaces (AT surfaces) of a supported crystal piece. In this quartz resonator, an alternating electric field is generated in the quartz piece by applying a predetermined AC voltage between the electrode films, and the quartz piece vibrates. In addition, techniques related to such a crystal resonator are disclosed in, for example, Patent Documents 1 and 2 below, but are disclosed in many documents other than these documents.
[0003]
[Patent Document 1]
JP-A-7-183759 [Patent Document 2]
JP 2001-7676 A
[Problems to be solved by the invention]
In general, it is known that the vibration frequency of a crystal blank having an AT cut surface greatly depends on its thickness (a thickness shear vibration mode). However, the crystal blank used in the above-described conventional resonator is known. Since is manufactured by polishing, there is a limit in miniaturization and thickness reduction. For this reason, the conventional resonator can be used only at a frequency of about several hundred MHz, and there is a problem that it is difficult to cope with a higher frequency. It is known that even in vibration modes other than the thickness shear vibration mode such as the contour shear vibration mode and the thickness longitudinal vibration mode, the vibration frequency becomes high by reducing the size of the vibration member such as quartz. I have.
[0005]
The present invention has been made in order to solve the above-described problems, and a method of manufacturing a piezoelectric vibrator in which a manufactured piezoelectric vibrator has been reduced in size and has a higher frequency, a piezoelectric vibrator and a piezoelectric vibrator using the same. An object is to provide a resonator.
[0006]
[Means for Solving the Problems]
The method of manufacturing a piezoelectric vibrator according to the present invention includes the steps of: forming a vibrating portion on the piezoelectric substrate by etching the piezoelectric substrate; forming a vibrating portion on the piezoelectric substrate; Arranging a pair of electrodes for generating an oscillating electric field on the piezoelectric substrate so as to sandwich the oscillating portion.
[0007]
In this method of manufacturing a piezoelectric vibrator, the vibrating portion is formed by etching a piezoelectric substrate. That is, since the vibrating portion has piezoelectricity, the vibrating portion can be vibrated by applying an AC voltage between a pair of electrodes arranged so as to sandwich the vibrating portion. As described above, in the method of manufacturing the piezoelectric vibrator, since a fine vibrating portion can be formed by an etching process capable of performing a precise removal process, a conventional manufacturing method of forming a vibrating portion by polishing is used. A high-frequency piezoelectric vibrator smaller than the manufactured piezoelectric vibrator can be manufactured.
[0008]
Further, it is preferable to dispose the pair of electrodes so as to be separated from the vibration part. In this case, the mass of the electrode does not affect the frequency of the vibrating part.
[0009]
Preferably, grooves are formed in the piezoelectric substrate region between the pair of electrodes and the vibrating portion. In this case, it is possible to extend the vibrating portion while suppressing the height of the piezoelectric vibrator.
[0010]
Further, the piezoelectric body of the piezoelectric body substrate is preferably made of quartz. Quartz is a piezoelectric material that has been widely used in the past, and can be easily obtained.
[0011]
In addition, it is preferable that, of the surface of the quartz crystal of the piezoelectric body, the surface facing the electrode is an AT cut surface. Since the vibration on the AT cut surface of the crystal has a small frequency change (a small frequency temperature coefficient) over a wide temperature range, this vibrator can be used for a wide range of applications.
[0012]
The piezoelectric vibrator according to the present invention includes a vibrating portion formed on the piezoelectric substrate by etching the piezoelectric substrate, and an electric field that is disposed on the piezoelectric substrate so as to sandwich the vibrating portion, and the vibrating portion vibrates. And a pair of electrodes for generating
[0013]
In this piezoelectric vibrator, the vibrating portion is formed by etching a piezoelectric substrate. That is, since the vibrating portion also has piezoelectricity, the vibrating portion can be vibrated by applying an AC voltage between a pair of electrodes arranged so as to sandwich the vibrating portion. As described above, in the piezoelectric vibrator, since a fine vibrating portion is formed by etching processing capable of precise removal processing, the piezoelectric vibrator is made smaller than a piezoelectric vibrator having a vibrating portion formed by polishing. And high frequency.
[0014]
The resonator according to the present invention is configured such that a vibrating portion formed on a piezoelectric substrate by etching a piezoelectric substrate and an electric field in which the vibrating portion vibrates are disposed on the piezoelectric substrate so as to sandwich the vibrating portion. And a housing for sealing the piezoelectric vibrator.
[0015]
In this resonator, the vibrating portion of the piezoelectric vibrator is formed by etching a piezoelectric substrate. That is, since the vibrating portion also has piezoelectricity, the vibrating portion can be vibrated by applying an AC voltage between a pair of electrodes arranged so as to sandwich the vibrating portion. In this way, the piezoelectric vibrator of this resonator has a fine vibrating portion formed by an etching process capable of precise removal processing, and is therefore smaller than a piezoelectric vibrator having a vibrating portion formed by polishing. The size can be reduced and the frequency can be increased. Therefore, the size and frequency of the resonator can be reduced by using the piezoelectric vibrator whose size and frequency have been reduced.
[0016]
Further, it is preferable to vacuum seal the piezoelectric vibrator. In this case, it is possible to prevent water droplets and dust from adhering to the surface of the piezoelectric vibrator.
[0017]
Further, it is preferable to seal the piezoelectric vibrator with an inert gas. In this case, it is possible to prevent water droplets and dust from adhering to the surface of the piezoelectric vibrator.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a method for manufacturing a piezoelectric vibrator, a piezoelectric vibrator, and a resonator using the same according to the present invention will be described in detail with reference to the accompanying drawings. Note that the same or equivalent elements are denoted by the same reference numerals, and a description thereof will be omitted if the description is duplicated.
[0019]
As shown in FIG. 1, the resonator 10 has a ceramic casing 12 having an upper surface opening, and a piezoelectric vibrator 14 is housed inside the casing 12. The piezoelectric vibrator 14 has a pair of electrodes (not shown), and is connected to a terminal 12 a provided inside the housing 12 via a lead 16. The terminal 12a is electrically connected to an AC external power supply (not shown), and the piezoelectric vibrator 14 is supplied with power from the external power supply.
[0020]
The upper opening of the housing 12 is closed by a metal lid 18. The lid 18 and the edge of the opening of the housing 12 are welded via a metal frame 19 to improve the sealing performance. Therefore, the inside of the housing 12 can be vacuum-sealed or inert gas-sealed using predetermined sealing equipment. By performing vacuum sealing (inert gas sealing) in this manner, it is possible to prevent water droplets, dust, and the like from adhering to the surface of the piezoelectric vibrator 14 in the housing 12.
[0021]
Next, the piezoelectric vibrator 14 will be described in detail with reference to FIGS. FIG. 2 is a perspective view showing the piezoelectric vibrator 14, and FIG. 3 is a cross-sectional view of the piezoelectric vibrator 14 of FIG.
[0022]
As shown in FIG. 2, the piezoelectric vibrator 14 includes a piezoelectric substrate 20 made of quartz and a pair of electrodes 22. The piezoelectric substrate 20 includes a substrate section 24 and a vibration section 26. The substrate part 24 has a rectangular parallelepiped outer shape, and a rectangular hole 25 is formed in the upper surface 24a in a direction along one side 24b of the upper surface 24a. Hereinafter, for convenience of description, the direction of one side 24b along which the hole 25 extends is defined as the X direction, the direction orthogonal to the hole 25 on the upper surface 24a is defined as the Y direction, and the direction orthogonal to the X direction and the Y direction is defined as the Z direction.
[0023]
The plate-shaped vibrating portion 26 is 11 μm (thickness: d) × 400 μm (height: a) × 600 μm (width: b), and is erected on the bottom surface of a hole 25 formed in the substrate portion 24. The position of the upper end 26a is higher than the upper surface 24a of the substrate unit 24. That is, an annular groove 25A (groove width: about 0.3 μm) is formed around the vibrating part 26. The both surfaces 26b of the vibrating portion 26 are so-called AT cut surfaces, and the normal direction is the Y direction. A flat electrode 22 (200 μm × 150 μm) is provided near the center of two sides of the edge corresponding to both surfaces of the vibrating portion 26 in the periphery of the groove 25 formed around the vibrating portion 26. I have. Thus, the vibrating part 26 is partially buried below the upper surface of the substrate part 24. With the substrate portion 24 and the vibrating portion 26 having such a structure, the piezoelectric vibrator 14 can be compared with a piezoelectric vibrator in which the vibrating portion is normally formed on a plane (see a two-dot chain line in FIG. 3). The height of the vibrating part 26 is increased at the same time as the height of the vibration part 26 is reduced.
[0024]
Note that the facing direction of the electrodes 22 is the Y direction, and each electrode 22 faces the surface (AT cut surface) of the vibrating part 26. Therefore, when an AC voltage is applied between the electrodes 22, an AC electric field that penetrates the vibrating portion 26 is generated. That is, the direction of the alternating electric field between the electrodes 22 is a direction (Y direction) orthogonal to both surfaces of the vibrating part 26. By adopting the AT cut surfaces on both surfaces of the vibrating part 26, the frequency change can be suppressed over a wide temperature range, so that the piezoelectric vibrator 14 can be used for various purposes.
[0025]
It has been known that a piezoelectric body such as a quartz crystal vibrates in an alternating electric field (alternating electric field). Also, since a vibration mode of a crystal piece having an AT cut surface is a thickness slip mode, Is known to vibrate in its thickness direction. Therefore, when an AC electric field is generated between the electrodes 22 using an external power supply, the vibrating portion 26 vibrates in the thickness direction (Y direction). The resonance of the vibrating portion 26 is caused by the generation of an alternating electric field in the vibrating portion 26 and the repetition of expansion and compression of the vibrating portion 26 due to a so-called reverse piezoelectric effect. Further, by making the AC frequency correspond to the natural frequency of the vibration unit 26, the vibration unit 26 can resonate.
[0026]
In the thickness sliding mode, it is known that the frequency increases as the thickness of the crystal blank decreases. Further, it is known that even in a vibration mode other than the thickness shear mode (such as a contour shear vibration mode and a thickness longitudinal vibration mode), the vibration frequency is increased with the downsizing of the vibration part.
[0027]
Next, a method for forming the vibration part 26 and the substrate part 24 of the piezoelectric vibrator 14 will be described with reference to FIG. FIG. 4 is a flowchart showing a procedure for forming the vibration section 26 and the substrate section 24.
[0028]
First, after the ZnO layer 30 and the Au layer 32 are laminated in the order of the ZnO layer 30 and the Au layer 32 in the region 20a to be the vibrating portion 26 of the piezoelectric substrate 20, the two layers are formed by photolithography and etching. The sections 30 and 32 are formed in the same shape as the cross section of the vibrating section 26 (FIG. 4A). Next, using the Au layer 32 as a mask, RIE plasma etching using CF ₄ or CF ₄ / O ₂ gas is performed to lower the substrate upper surface 24 a other than the region masked by the Au layer 32 (FIG. 4B). ). An Au electrode layer 34 is formed by photolithography and etching on the substrate upper surface 24a lowered by RIE etching (FIG. 4C). Next, using the Au electrode layer 34 as a mask, RIE plasma etching is again performed using CF ₄ / O ₂ gas to form a groove 25A around the vibrating part 26 (FIG. 4D). Then, the electrodes 22 are formed from the Au electrode layer 34 by photolithography and etching, and the ZnO layer 30 and the Au layer 32 on the vibrating portion 26 are removed by etching (FIG. 4E). As described above, by employing the etching process capable of performing the precision processing for the removal processing, the vibration part 26 with high accuracy is formed.
[0029]
As described above in detail, in the piezoelectric vibrator 14, since the fine vibrating portion 26 is formed by performing the etching process around the region 20a to be the vibrating portion 26 of the piezoelectric substrate 20, A vibrating portion smaller than the vibrating portion formed by conventional polishing can be manufactured. Therefore, in the piezoelectric vibrator 14 and the resonator 10, the size can be reduced due to the miniaturization of the vibration section 26, and the frequency can be increased due to the reduction in the thickness of the vibration section 26. . Further, unlike the conventional piezoelectric vibrator (crystal resonator), since no electrode is attached to the vibrating portion (crystal piece), the mass of the electrode does not adversely affect the high frequency. Therefore, it is not necessary to make the electrode 22 thinner and smaller than necessary, and it is possible to suppress a resonator loss that increases with an increase in electrode resistance. When a film-like electrode (electrode film) is formed on the surface of the vibrating part, the strain stress generated in the process of forming the electrode film has a bad influence on the vibrating part. Since it is non-contact with 22, it is irrelevant to such a problem.
[0030]
Next, a piezoelectric vibrator different from the above-described piezoelectric vibrator 14 will be described with reference to FIGS.
[0031]
The piezoelectric vibrator 14A shown in FIG. 5 is different from the piezoelectric vibrator described above only in that no groove 25A is formed around the vibrating part 26 and only in that the electrode 22 rises along the vibrating part 26. Different from 14. That is, the vibrating section 26 is provided upright on the flat top surface 24a of the substrate section, and the electrodes 22 are arranged so as to sandwich the vibrating section. Also in the piezoelectric vibrator 14A, since an AC electric field in the Y direction can be generated between the pair of electrodes 22, the vibrating section 26 vibrates in the Y direction. The vibrating section 26 is also manufactured by etching. That is, first, the ZnO layer 30 and the Au layer 32 are laminated in the order of the ZnO layer 30 and the Au layer 32 on the region 20a to be the vibration part 26 on the piezoelectric substrate 20, and then the two layers are formed by photolithography and etching. 30 and 32 are formed in the same shape as the cross-sectional shape of the vibrating part 26 (FIG. 6A). Next, using the Au layer 32 as a mask, RIE plasma etching using CF ₄ / O ₂ gas is performed to lower the upper surface 24a of the substrate other than the region 20a masked by the Au layer 32 (FIG. 6B). After the resist layer 36 and the Au electrode layer 38 having a predetermined pattern (remaining area pattern of the electrode rising portion) are formed on the upper surface 24a of the substrate lowered by the RIE etching by photolithography, a portion along the vibrating portion 26 is formed by lift-off etching. The electrode 22 is formed (FIG. 6C). Next, after a resist pattern 40 having a predetermined pattern (remaining area pattern of the underlying portion of the electrode) is laminated on the substrate by photolithography, an Au electrode layer 42 is laminated (FIG. 6D). Then, the electrode 22 is formed by lift-off etching, and the ZnO layer 30 and the Au layer 32 on the vibrating portion 26 are removed by etching (FIG. 6E).
[0032]
As described in detail above, in the piezoelectric vibrator 14A, similarly to the above-described piezoelectric vibrator 14, the fine vibrating portion 26 is formed by etching around the region 20a to be the vibrating portion 26 of the piezoelectric substrate 20. Is formed, a vibrating portion smaller than the vibrating portion formed by the conventional polishing process can be manufactured. Therefore, in the piezoelectric vibrator 14 </ b> A and the resonator 10 using the same, it is possible to reduce the size due to the miniaturization of the vibrating section 26 and to increase the frequency due to the thinning of the vibrating section 26. Can be planned.
[0033]
The piezoelectric vibrator 14B shown in FIG. 7 has a point that the height of the vibrating part 26 and the substrate part 24 are the same, a point that both ends 26c in the X direction of the vibrating part 26 are connected to the substrate part 24, Is different from the above-described piezoelectric vibrator 14 only in that it hangs down to the bottom surface of the groove 25A. That is, the piezoelectric vibrator 14B includes a rectangular parallelepiped piezoelectric substrate 20 having two parallel grooves 25A and a pair of electrodes 22, and the piezoelectric vibrator 14B has two grooves 25A. The portion sandwiched between the portions is a vibrating portion 26. Also in the piezoelectric vibrator 14B, an AC electric field in the Y direction can be generated between the pair of electrodes 22, and the AC electric field is applied to the vibrating portion 26. The vibrator 26 vibrates in the Y direction. In this piezoelectric vibrator 14B, as in the above-described piezoelectric vibrators 14 and 14A, the vibrating portion 26 is formed by a predetermined etching process. The electrode 22 is formed by a predetermined photolithography and etching process. Therefore, in the piezoelectric vibrator 14B and the resonator 10 using the same, the size and the frequency can be reduced as in the above-described piezoelectric vibrators 14 and 14A. Here, an example is shown in which both ends 26c of the vibrating portion 26 in the X direction are connected to the substrate 24, but only one end of the both ends 26c is connected to the substrate 24. It may be an aspect.
[0034]
The piezoelectric vibrator 14C shown in FIG. 8 differs from the piezoelectric substrate 14A shown in FIG. 5 only in that the upper surface 24a of the substrate portion is inclined and the area of the electrode 22 is large. Also in this piezoelectric vibrator 14C, when an AC voltage is applied between the electrodes 22, an AC electric field in the Y direction penetrating the vibrating part 26 is generated, and the vibrating part 26 vibrates in the Y direction. Further, in the piezoelectric vibrator 14C, the vibrating portion 26 is formed by a predetermined etching process, similarly to the above-described piezoelectric vibrators 14, 14A and 14B. Therefore, in the piezoelectric vibrator 14C and the resonator 10 using the same, the miniaturization and high frequency can be achieved similarly to the above-described piezoelectric vibrators 14, 14A and 14B.
[0035]
The present invention is not limited to the above embodiment, and various modifications are possible. For example, the removal processing of the piezoelectric substrate is not limited to RIE etching, but may be laser processing, ion beam processing, or the like. Further, the shape of the vibrating portion is not limited to a flat plate shape, and may be an XY cross-sectional shape as shown in FIG. That is, (a) a shape in which four corners are chamfered into a curved shape, (b) a shape protruding near the center of the surface in the electrode direction, (c) an elliptical shape, (e) a circular shape, or the like. . Furthermore, the lower part of the vibrating part may be tapered to improve the stability of the vibrating part. The positional relationship between the vibrating portion and the electrode can be appropriately changed within a range in which an AC electric field between the electrodes passes through the vibrating portion. For example, the height of the electrode can be shifted up and down. Further, the etching procedure and the material for producing the piezoelectric vibrator are not limited to those described above, and may be changed as appropriate for shortening the manufacturing time and improving the productivity.
[0036]
When the vibrating portion is made of quartz, both surfaces of the vibrating portion are not limited to the AT cut surface, and may be, for example, a CT cut surface or an X cut surface. That is, the vibration mode of the vibrating section is not limited to the thickness shear mode, and may be, for example, a contour slip mode or a thickness longitudinal vibration mode. Further, the piezoelectric body is not limited to natural or artificial quartz, and may be, for example, LiNbO ₃ crystal or a piezoelectric ceramic material (BaTiO ₃ or the like).
[0037]
【Example】
The inventors actually manufactured a piezoelectric vibrator and measured its resonance characteristics. Hereinafter, the measurement results are shown.
[0038]
(First embodiment)
A piezoelectric vibrator substantially similar to the piezoelectric vibrator 14 shown in FIG. 2 was fabricated by etching a piezoelectric substrate made of quartz and attaching a pair of electrodes. The etching conditions were a CF ₄ gas atmosphere, a pressure of 2 Pa, and an RF power of 300 W. The vibrating part of the piezoelectric vibrator thus manufactured had a thickness (d) of 11 μm, a height (a) of 600 μm, and a width (b) of 600 μm. The size of the rectangular electrode was 100 μm × 20 μm. The distance between these vibrating parts and the electrodes was 0.3 μm. The piezoelectric vibrator was sealed with a surface-mount type ceramic casing, a 3 mm × 3 mm × 1.5 mm resonator was manufactured, and the resonance frequency and Q value of the resonator were measured. As a result, the resonance frequency was 150 MHz, the Q value was 7,800, and good resonance characteristics were obtained.
[0039]
(Second embodiment)
Etch the piezoelectric substrate made of quartz and attach a pair of electrodes,
A piezoelectric vibrator substantially similar to the piezoelectric vibrator 14 shown in FIG. 2 was manufactured. The etching conditions were a CF ₄ gas atmosphere, a pressure of 2 Pa, and an RF power of 300 W. The vibrating part of the piezoelectric vibrator thus manufactured had a thickness (d) of 1 μm, a height (a) of 100 μm, and a width (b) of 100 μm. The size of the rectangular electrode was 50 μm × 10 μm. The distance between the vibrating part and the electrode was 0.1 μm. This piezoelectric vibrator was sealed with a surface-mount type ceramic casing, a 3 mm × 3 mm × 1.5 mm resonator was manufactured, and the resonance frequency and Q value of this resonator were measured. As a result, the resonance frequency was 1.6 GHz, the Q value was 850, and good resonance characteristics were obtained.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the piezoelectric vibrator which achieved miniaturization and high frequency of the produced piezoelectric vibrator, a piezoelectric vibrator, and a resonator using the same are provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a resonator according to an embodiment of the present invention.
FIG. 2 is a perspective view showing the piezoelectric vibrator of FIG. 1;
FIG. 3 is a sectional view taken along line III-III of the piezoelectric vibrator of FIG. 2;
FIG. 4 is a flowchart showing a procedure for manufacturing the piezoelectric vibrator of FIG. 2;
FIG. 5 is a perspective view showing a piezoelectric vibrator in a mode different from that of the piezoelectric vibrator of FIG. 2;
FIG. 6 is a flowchart showing a procedure for manufacturing the piezoelectric vibrator of FIG.
FIG. 7 is a perspective view showing a piezoelectric vibrator having a mode different from that of the piezoelectric vibrator of FIG. 2;
FIG. 8 is a perspective view showing a piezoelectric vibrator in a mode different from that of the piezoelectric vibrator of FIG. 2;
FIG. 9 is a diagram showing a deformation mode of a cross section of a vibrating portion of the piezoelectric vibrator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... resonator, 12 ... housing | casing, 14, 14A, 14B, 14C ... piezoelectric vibrator, 20 ... piezoelectric substrate, 20a ... area | region, 22 ... electrode, 24 ... substrate part, 25A ... groove part, 26 ... vibrating part , 26b ... surface.

Claims (9)

Forming a vibrating portion on the piezoelectric substrate by etching the piezoelectric substrate,
Arranging a pair of electrodes for generating an electric field in which the vibrating part vibrates on the piezoelectric substrate so as to sandwich the vibrating part. 2. The method according to claim 1, wherein the pair of electrodes are arranged apart from the vibrating part. 3. 3. The method according to claim 1, wherein a groove is formed in each of the piezoelectric substrate regions between the pair of electrodes and the vibrating section. 4. The method for manufacturing a piezoelectric vibrator according to claim 1, wherein the piezoelectric body of the piezoelectric substrate is quartz. The method for manufacturing a piezoelectric vibrator according to claim 4, wherein a surface of the crystal of the piezoelectric body that faces the electrode is an AT cut surface. A vibration portion formed on the piezoelectric substrate by etching the piezoelectric substrate,
A piezoelectric vibrator, comprising: a pair of electrodes that are arranged on the piezoelectric substrate so as to sandwich the vibrating part and generate an electric field in which the vibrating part vibrates. A vibrating portion formed on the piezoelectric substrate by etching the piezoelectric substrate, and a pair of electrodes arranged on the piezoelectric substrate so as to sandwich the vibrating portion and generating an electric field in which the vibrating portion vibrates; A piezoelectric vibrator comprising:
A resonator for sealing the piezoelectric vibrator. The resonator according to claim 7, wherein the piezoelectric vibrator is vacuum-sealed. The resonator according to claim 7, wherein the piezoelectric vibrator is sealed with an inert gas.

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