JP2017060123A - Piezoelectric vibration piece and piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compact piezoelectric vibration piece and piezoelectric vibrator having excellent vibration characteristics.SOLUTION: A piezoelectric vibration piece 10 includes a piezoelectric plate 11 formed of an AT cut crystal substrate, and excitation electrodes 51A, 51B formed, respectively, on the first surface 11A and second surface 11B of the piezoelectric plate 11 facing each other in the thickness direction. In at least the first surface 11A, a top face 21, and a slope 22 surrounding the top face 21 while inclining are formed. Inclination angle of the slope 22 for the top face 21 is set less than 90°, and at least in the first surface 11A, the excitation electrode 51A is formed across the top face 21 and slope 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric vibrating piece and a piezoelectric vibrator.

  Conventionally, a piezoelectric vibrating piece formed from an AT-cut quartz substrate includes a piezoelectric plate and excitation electrodes formed on the front and back surfaces of the piezoelectric plate. The piezoelectric vibrating reed vibrates in thickness by being applied with a voltage between the excitation electrodes.

By the way, if the piezoelectric vibrating piece described above is downsized, the vibration generated in the vibration region (portion where the excitation electrode is formed) is easily transmitted to the peripheral portion of the piezoelectric vibrating piece. When the vibration propagates to the peripheral portion of the piezoelectric vibrating piece, unnecessary vibration is induced at the peripheral portion.
Therefore, a so-called mesa-type piezoelectric vibrating piece in which a mesa portion is formed on at least one of the front and back surfaces of the piezoelectric plate is known (for example, see Patent Documents 1 and 2 below). In the mesa-type piezoelectric vibrating piece, the thickness of the central region of the piezoelectric plate serving as the vibration region can be made larger than the thickness of the peripheral portion of the piezoelectric plate, and vibration energy can be confined in the vibration region. Therefore, it is possible to reduce the crystal impedance (hereinafter referred to as CI value) of the piezoelectric vibrating piece.

JP 2011-66905 A JP2013-197826A

  However, in the configuration disclosed in Patent Document 1, since the excitation electrode is formed only on the top surface of the mesa portion, when the vibration generated in the vibration region propagates toward the outer periphery of the piezoelectric plate, Unnecessary vibration is induced at the boundary (ridge line portion) between the top surface and the side surface. Further, as disclosed in, for example, Patent Document 2, even if the excitation electrode is provided over the top surface (upper surface) and the side surface of the mesa portion, the boundary between the top surface (upper surface) and the side surface of the mesa portion is If it is steep, unwanted vibration is induced at the boundary. Therefore, there is still room for improvement in terms of suppressing unnecessary vibration and improving vibration characteristics.

  The aspect which concerns on this invention aims at providing a small piezoelectric vibrating piece and a piezoelectric vibrator provided with the outstanding vibration characteristic.

(1) A piezoelectric vibrating piece according to an aspect of the present invention is formed on each of a piezoelectric plate formed of an AT-cut quartz substrate and a first surface and a second surface that face each other in the thickness direction of the piezoelectric plate. An excitation electrode, and at least the first surface is formed with a top surface and an inclined surface surrounding the top surface and inclined with respect to the top surface, and the inclined surface is inclined with respect to the top surface. Is set to be less than 90 °, and at least on the first surface, the excitation electrode is formed across the top surface and the inclined surface.
According to the above aspect (1), since the excitation electrode is formed over the top surface and the slope, the area of the excitation electrode can be ensured as compared with the case where the excitation electrode is formed only on the top surface. As a result, the CI value can be reduced and the vibration characteristics can be improved.

(2) In the aspect of the above (1), the inclined surface may be set to have an inclination angle with respect to the top surface of less than 20 °.
In the case of (2) above, since the inclination angle between the top surface and the slope is smaller than the inclination angle between the top surface and the slope when the slope is a natural crystal surface, the top surface and the slope should be connected gradually. become. Thereby, it can suppress that an unnecessary vibration is induced in the boundary part of a top surface and a slope. As a result, the CI value can be reduced and the vibration characteristics can be improved.

(3) In the above aspect (1) or (2), the piezoelectric plate is formed in a rectangular shape with the Z′-axis direction of the AT-cut quartz crystal substrate as a longitudinal direction in a plan view seen from the thickness direction. May be.
In the case of (3), a low CI value can be maintained even when the piezoelectric plate is downsized.
That is, the AT-cut quartz crystal substrate is composed of an X axis and a Z ′ axis. Under such a configuration, when the AT-cut quartz substrate is undergoing thickness shear vibration, electric polarization occurs in the X axis and the Z ′ axis. Electric polarization is a charge bias, which is sinusoidal on the X axis and linear on the Z ′ axis. By setting the long side to the Z ′ axis where the electric polarization is linear, the side where the strongest charge is generated can be lengthened. The CI value becomes lower as the region where the strong charge is generated becomes wider. Therefore, it is possible to maintain a lower CI value by setting the Z ′ axis as a long side.

(4) In any one of the above aspects (1) to (3), both end portions of the piezoelectric plate that are separated in the Z′-axis direction of the AT-cut quartz substrate protrude in the surface direction of the piezoelectric plate. Each of the protruding portions may be formed.
In the case of the above (4), by using a protrusion as a mount region for mounting the piezoelectric vibrating piece on the package, the interval between the vibration region (the portion where the excitation electrode is formed) and the mount region is reduced. It can be secured. Thereby, it is possible to suppress vibration energy generated in the vibration region from propagating to the mounting member or the package through the mount region, and to suppress vibration leakage. In addition, since the adhesion area between the piezoelectric plate and the mounting member can be ensured, the bonding strength between the mounting member and the piezoelectric plate can be ensured.

(5) In any one of the above aspects (1) to (4), at least in the first surface, the outer peripheral edge of the excitation electrode is more than the outer peripheral edge of the inclined surface in a plan view as viewed from the thickness direction. May also be located inside.
In the case of (5) above, vibration energy is prevented from propagating to the outer periphery of the piezoelectric plate (the boundary between the side surface and the inclined surface of the piezoelectric plate), and unwanted vibration is suppressed from being induced at the outer periphery of the piezoelectric plate. it can.

(6) In any one of the above aspects (1) to (4), the piezoelectric plate further includes a side edge that surrounds the periphery of the slope and extends in a surface direction of the piezoelectric plate. The edge portion may be thinner than a portion including the top surface of the piezoelectric plate, and at least the outer peripheral edge of the excitation electrode may be disposed on the edge portion on the first surface.
In the case of (6) above, the area of the excitation electrode can be increased, so that the CI value can be reduced and good thickness shear vibration can be obtained.

(7) A piezoelectric vibrator according to an aspect of the present invention includes the piezoelectric vibrating piece according to any one of the above (1) to (6) and a package on which the piezoelectric vibrating piece is mounted. And
According to the above aspect (7), since the piezoelectric vibrating piece is provided, a small piezoelectric vibrator having excellent vibration characteristics can be obtained.

  According to the aspect of the present invention, it is possible to provide a small piezoelectric vibrating piece and a piezoelectric vibrator having excellent vibration characteristics.

FIG. 3 is a plan view of the piezoelectric vibrating piece according to the first embodiment. 1 is an exploded perspective view of a piezoelectric vibrator according to a first embodiment. FIG. 3 is a cross-sectional view corresponding to line III-III in FIG. 2. It is sectional drawing which shows the procedure of the manufacturing process of the piezoelectric vibrating piece which concerns on 1st Embodiment. It is a top view of the piezoelectric vibrating piece according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
First, the piezoelectric vibrating piece and the piezoelectric vibrator of the first embodiment will be described.
FIG. 1 is a plan view of a piezoelectric vibrating piece 10 according to the first embodiment. FIG. 2 is an exploded perspective view of the piezoelectric vibrator 1 according to the first embodiment. 3 is a cross-sectional view corresponding to the line III-III in FIG.
As shown in FIGS. 1 to 3, the piezoelectric vibrating piece 10 includes a piezoelectric plate 11, excitation electrodes 51 </ b> A and 51 </ b> B (first excitation electrode 51 </ b> A and second excitation electrode 51 </ b> B), mount electrodes 13 </ b> A and 13 </ b> B, and routing wiring. 16A, 16B.

The piezoelectric plate 11 is formed of an AT-cut quartz substrate, and vibrates in a thickness-slip mode by the voltage applied by the excitation electrodes 51A and 51B.
Here, the AT cut is a rotation around the X axis with respect to the Z axis among the three crystal axes of the electric axis (X axis), the mechanical axis (Y axis), and the optical axis (Z axis) which are crystal axes of the artificial quartz. This is a processing method of cutting in a direction (Z′-axis direction) inclined by 35 degrees 15 minutes. The piezoelectric vibrating piece 10 having the piezoelectric plate 11 cut out by the AT cut has an advantage that the frequency temperature characteristic is stable, the structure and shape are simple, the processing is easy, and the CI value is low.
In the following description, the XY′Z ′ coordinate system is used when describing the configuration of each figure. In this XY′Z ′ coordinate system, the Y ′ axis is an axis orthogonal to the X axis and the Z ′ axis. In the X-axis direction, the Y′-axis direction, and the Z′-axis direction, the arrow direction in the figure is defined as the + direction, and the direction opposite to the arrow is described as the − direction.

  The piezoelectric plate 11 is formed in a rectangular shape with the Z′-axis direction as the longitudinal direction in a plan view viewed from the Y′-axis direction. The piezoelectric plate 11 is formed with the thickness direction along the Y′-axis direction. The piezoelectric plate 11 has an outer periphery that connects the first surface 11A to the Y′-axis direction + side, the second surface 11B to the Y′-axis direction − side, and the first surface 11A and the second surface 11B to the outside of the XZ ′ plane. And an end face 11C.

As shown in FIGS. 1 to 3, the first surface 11 </ b> A of the piezoelectric plate 11 includes a first mesa portion (mesa portion) 20 formed in the center portion, and a marginal surface 24 surrounding the first mesa portion 20. And including. The second surface 11 </ b> B of the piezoelectric plate 11 includes a second mesa part (mesa part) 30 formed in the center part and a peripheral face 34 surrounding the second mesa part 30.
As appropriate, a portion of the piezoelectric plate 11 outside the mesa portions 20 and 30 in a plan view viewed from the Y′-axis direction (a portion of the piezoelectric plate 11 including the edge surface 24, the edge surface 34, and the outer peripheral end surface 11C). Is referred to as the edge 40.

The first mesa portion 20 bulges in the Y′-axis direction + side at the central portion of the first surface 11A. The first mesa unit 20 includes a first top surface (top surface) 21 and a first inclined surface 22 surrounding the first top surface 21.
The first top surface 21 is a flat surface extending in the XZ′-axis direction. The outer shapes of the first top surface 21 and the first inclined surface 22 are formed in a rectangular shape with the Z′-axis direction as the longitudinal direction in a plan view viewed from the Y′-axis direction.

The first slope 22 connects the first top surface 21 and the edge surface 24. Of the first slope 22, the inner peripheral edge is formed continuously with each side of the outer peripheral edge of the first top surface 21, and the outer peripheral edge is formed continuously with the inner peripheral edge of the edge surface 24. The first slope 22 includes a surface facing the Z′-axis direction + side, a surface facing the Z′-axis direction − side, a surface facing the X-axis direction − side, and a surface facing the X-axis direction + side. It is out. Each surface of the first inclined surface 22 extends from the outer peripheral edge of the first top surface 21 to the outside (+ Z′-axis direction, −Z′-axis direction, −X-axis direction, + X-axis direction), and the −Y′-axis direction. Extends towards.
The inclination angle of each surface of the first slope 22 with respect to the first top surface 21 is set to be less than 20 °. The width dimension of the first slope 22 (distance from the inner periphery to the outer periphery of the first slope 22 in a plan view as viewed from the Y′-axis direction) is the maximum width dimension with respect to the minimum width dimension on the entire circumference of the first slope 22. The ratio is set in the range of 1 to 2.

The second mesa portion 30 bulges in the Y′-axis direction − side at the central portion of the second surface 11B. The second mesa unit 30 includes a second top surface (top surface) 31 and a second slope 32 surrounding the second top surface 31.
The second top surface 31 is a flat surface extending in the XZ ′ axis direction. The outer shapes of the second top surface 31 and the second inclined surface 32 are formed in a rectangular shape with the Z′-axis direction as the longitudinal direction in a plan view viewed from the Y′-axis direction.

The second slope 32 connects the second top surface 31 and the edge surface 34. Of the second slope 32, the inner peripheral edge is formed continuously with each side of the outer peripheral edge of the second top surface 31, and the outer peripheral edge is formed continuously with the inner peripheral edge of the edge surface 34. The second inclined surface 32 includes a surface (not shown) facing the Z′-axis direction + side, a surface (not shown) facing the Z′-axis direction − side, a surface facing the X-axis direction − side, and an X-axis direction + A side-facing surface. Each surface of the second inclined surface 32 extends in the + Y′-axis direction from the outer peripheral edge of the second top surface 31 toward the outside (+ Z′-axis direction, −Z′-axis direction, −X-axis direction, + X-axis direction). It extends towards.
The inclination angle of each surface of the second inclined surface 32 with respect to the second top surface 31 is set to be less than 20 °. The width of the second inclined surface 32 (the distance from the inner peripheral edge to the outer peripheral edge of the second inclined surface 32 in a plan view as viewed from the Y′-axis direction) is the maximum width dimension with respect to the minimum width dimension on the entire circumference of the second inclined surface 32. The ratio is set in the range of 1 to 2.

The outer peripheral edge of the first top surface 21 and the outer peripheral edge of the second top surface 31 are formed so as to overlap in a plan view viewed from the Y′-axis direction. Further, the outer peripheral edge of the first inclined surface 22 and the outer peripheral edge of the second inclined surface 32 are formed so as to overlap in a plan view viewed from the Y′-axis direction.
In addition, the planar view external shape of the mesa parts 20 and 30 (the top surfaces 21 and 31 and the slopes 22 and 32) can be changed as appropriate.

The first excitation electrode 51A is formed in a rectangular shape having the Z′-axis direction as a longitudinal direction in a plan view as viewed from the Y′-axis direction. The central portion of the first excitation electrode 51A covers the first top surface 21 from the Y′-axis direction + side.
The first excitation electrode 51 </ b> A is formed within the entire surface of the first top surface 21 and a part of the first slope 22. Specifically, the outer periphery of the first excitation electrode 51 </ b> A reaches the midway portion of the first inclined surface 22 in the width direction across the boundary between the first top surface 21 and the first inclined surface 22. In other words, the outer peripheral edge of the first excitation electrode 51 </ b> A is located inside the outer peripheral edge of the first slope 22. The outer peripheral edge of the first excitation electrode 51 </ b> A only needs to be disposed on the first inclined surface 22 (the surface of the first inclined surface 22 that does not include the inner peripheral edge and the outer peripheral edge), and the width direction on the first inclined surface 22. The position of can be changed as appropriate.

The second excitation electrode 51B is formed in a rectangular shape with the Z′-axis direction as the longitudinal direction in a plan view viewed from the Y′-axis direction. The center portion of the second excitation electrode 51B covers the second top surface 31 from the Y′-axis direction − side.
The second excitation electrode 51 </ b> B is formed within the entire area of the second top surface 31 and a part of the second inclined surface 32. Specifically, the outer periphery of the second excitation electrode 51B reaches the midway portion of the second inclined surface 32 in the width direction across the boundary between the second top surface 31 and the second inclined surface 32. In other words, the outer peripheral edge of the second excitation electrode 51 </ b> B is located inside the outer peripheral edge of the second inclined surface 32. The outer peripheral edge of the second excitation electrode 51 </ b> B only needs to be disposed on the second inclined surface 32 (the surface of the second inclined surface 32 that does not include the inner peripheral edge and the outer peripheral edge), and the width direction on the first inclined surface 22. The position of can be changed as appropriate.

The first excitation electrode 51A and the second excitation electrode 51B are formed so as to overlap in a plan view viewed from the Y′-axis direction.
In addition, the planar view outline of the excitation electrodes 51A and 51B can be appropriately changed according to the planar view outline of the top surfaces 21 and 31.

  The pair of mount electrodes 13A and 13B are formed at one end of the piezoelectric plate 11 in the X-axis direction and at both ends spaced apart in the Z′-axis direction.

  The mount electrode 13A is formed across the first surface 11A, the second surface 11B, and the outer peripheral end surface 11C at the corners of the piezoelectric plate 11 located on the X axis direction + side and the Z ′ axis direction + side. The mount electrode 13A is connected to the excitation electrode 51A via the lead wiring 16A on the first surface 11A of the piezoelectric plate 11.

The mount electrode 13B is formed across the first surface 11A, the second surface 11B, and the outer peripheral end surface 11C at corners located on the X axis direction + side and the Z ′ axis direction − side of the piezoelectric plate 11. The mount electrode 13B is connected to the excitation electrode 51B via the lead wiring 16B (see FIG. 1) on the second surface 11B of the piezoelectric plate 11.
The mount electrode 13B may be formed on at least the surface on the second surface 11B side.

  Here, the excitation electrodes 51A and 51B, the mount electrodes 13A and 13B, and the routing wirings 16A and 16B are made of a single layer film of metal such as gold or a metal such as chromium as an underlayer and a metal such as gold as an upper layer. It is formed with the laminated film etc. which were made.

(Piezoelectric vibrator)
Next, the piezoelectric vibrator 1 including the piezoelectric vibrating piece 10 will be described.
As shown in FIG. 2, the piezoelectric vibrator 1 of the present embodiment is one in which a piezoelectric vibrating piece 10 is accommodated in a cavity C of a package 5. The package 5 is formed by overlapping the base substrate 2 and the lid substrate 3. Both the base substrate 2 and the lid substrate 3 are formed of a ceramic material or the like.

The base substrate 2 includes a bottom wall 2a formed in a rectangular shape in plan view, and a side wall 2b erected in the + Y′-axis direction from the peripheral edge of the bottom wall 2a.
The side wall part 2b is formed over the entire periphery in the peripheral part of the bottom wall part 2a.
A pair of internal electrodes 7 is formed on a surface (bottom wall surface) located on the + side in the Y′-axis direction of the bottom wall portion 2a. The pair of internal electrodes 7 are formed apart from each other in the Z′-axis direction. In addition, a pair of external electrodes (not shown) is formed on a surface (bottom wall rear surface) located on the Y′-axis direction − side of the bottom wall portion 2a. The internal electrode 7 and the external electrode are electrically connected by a through electrode (not shown) that penetrates the bottom wall portion 2a in the thickness direction. In addition, the connection form of the internal electrode 7 and the external electrode is not limited to this, for example, in the form of connecting the internal electrode 7 and the external electrode via wiring extending in the surface direction of the ceramic sheet. There may be.

The lid substrate 3 is formed in a rectangular plate shape in plan view. The peripheral edge of the lid substrate 3 is bonded to the end surface of the side wall 2b of the base substrate 2 from the + Y′-axis direction.
A cavity C is formed in a region surrounded by the bottom wall portion 2 a and the side wall portion 2 b of the base substrate 2 and the lid substrate 3.

As shown in FIG. 3, the piezoelectric vibrating piece 10 is accommodated in the cavity C.
The piezoelectric vibrating piece 10 is mounted on the bottom wall portion 2a of the base substrate 2 via a mounting member 9 such as a conductive paste. More specifically, the corresponding mount electrodes 13A and 13B of the piezoelectric vibrating piece 10 are mounted from the second surface 11B side to the pair of internal electrodes 7 formed on the bottom wall portion 2a of the base substrate 2. Thereby, the piezoelectric vibrating reed 10 is mechanically held by the package 5 and the mount electrodes 13A and 13B and the internal electrode 7 are electrically connected to each other.

(Production method)
Next, a method for manufacturing the piezoelectric vibrating piece 10 will be described with reference to FIG.
FIG. 4 is a cross-sectional view showing the procedure of the manufacturing process of the piezoelectric vibrating piece 10.
In the following description, a method for collectively forming a plurality of piezoelectric vibrating reeds 10 from an AT-cut quartz substrate (hereinafter simply referred to as a wafer S) will be described.
Further, in the following description, a process of forming the mesa portion (first mesa portion 20) only on one side of the wafer S (the surface on the Y′-axis direction + side) is shown, but both surfaces of the wafer S (Y′-axis direction + The mesa portions (the first mesa portion 20 and the second mesa portion 30) may be simultaneously formed on the side surface and the Y′-axis direction-side surface.

First, a wafer having a constant thickness obtained by AT-cutting a quartz Lambert ore is lapped and roughly processed, and then the work-affected layer is removed by etching. Thereafter, mirror polishing such as polishing is performed to prepare a wafer S having a predetermined thickness.
In the following description, a surface corresponding to the first surface 11A of the piezoelectric plate 11 described above is appropriately referred to as a surface of the wafer S.

Next, as shown in FIG. 4A, the surface of the wafer S is dry-etched (dry etching process).
As dry etching, for example, reactive ion etching (RIE), reverse sputtering, or the like can be selected.
By this step, the surface of the wafer S is flattened. At this time, the surface roughness of the wafer S is formed to an arithmetic average roughness Ra standardized in JIS B 0031, for example, less than 10 nm (Ra <10 nm), and a maximum height Ry, for example, less than 100 nm (Ry <100 nm). It is preferred that
The dry etching is performed at least within the range in which the slope (first slope 22) can be formed in the etching process (FIG. 4E, mesa portion forming process) for forming the slope on the wafer S described later. If it is, it will not be specifically limited.

Next, as shown in FIG. 4B, an etching protection film 80 and a photoresist film 81 are formed on the wafer S (film formation process).
The etching protective film 80 is a laminated film in which, for example, an etching protective film in which chromium (Cr) is formed to several tens of nm and an etching protective film in which gold (Au) is formed to several tens of nm are sequentially laminated.
In this step, first, an etching protective film 80 is sequentially formed on the surface of the wafer S by a sputtering method, a vapor deposition method, or the like.
Next, a resist material is applied on the etching protection film 80 by a spin coating method or the like to form a photoresist film 81.
As the resist material used in the present embodiment, a rubber negative resist mainly composed of cyclized rubber (for example, cyclized isoprene) is preferably used. The rubber negative resist is refined by dissolving cyclized rubber in an organic solvent, adding a bisazide photosensitizer, filtering, and removing impurities.

Next, as shown in FIG. 4C, a photomask 81a corresponding to the planar view outer shape of the mesa portion 20 is formed on the photoresist film 81 (photomask forming step).
Specifically, first, the photoresist film 81 formed on the wafer S is exposed using an exposure mask on which an outer shape pattern corresponding to the outer shape in plan view of the mesa unit 20 is formed. Thereafter, the photoresist film 81 is developed.
As a result, a photomask 81 a is formed on the photoresist film 81.

Next, as shown in FIG. 4D, a mesa portion mask 80a corresponding to the photomask 81a (corresponding to a plan view outline of the mesa portion 20) is formed on the etching protection film 80 (mesa portion mask forming step). ).
Specifically, the etching protection film 80 that is not masked is etched using the photoresist film 81 on which the photomask 81a is formed as a mask, and the etching protection film 80 is selectively removed. Thereafter, the photoresist film 81 is peeled off. Note that the photoresist film 81 may be left.
For the etching process in the mesa mask forming process, a wet etching method in which the wafer S on which the etching protective film 80 and the photoresist film 81 are formed is immersed in a chemical solution can be used. For example, when the etching protection film 80 is made of gold (Au), it can be etched using iodine as a chemical solution.

Next, as shown in FIG. 4E, the first mesa portion 20 corresponding to the mesa portion mask 80a is formed on the surface of the wafer S (mesa portion forming step).
Specifically, an etching process is performed on an unmasked portion of the surface of the wafer S (hereinafter simply referred to as an exposed surface) using the etching protective film 80 on which the mesa mask 80a is formed as a mask.
For the etching process in the mesa portion forming step, a wet etching method in which the wafer S on which the mesa portion mask 80a is formed is immersed in a chemical solution can be used. For example, etching can be performed using hydrofluoric acid as a chemical solution.

Here, normally, in the wet etching of quartz, a natural crystal plane having a specific angle appears due to etching anisotropy peculiar to quartz. Therefore, in the surface of the wafer S, the etching is hardly observed in the portion masked by the mesa mask 80a (hereinafter referred to as the mask surface).
However, in the present embodiment, the dry etching process is performed on the wafer S before the etching process is performed on the wafer S in the mesa portion forming step. Therefore, the wet etching in the mesa portion forming process proceeds to the outer peripheral portion of the mask surface of the wafer S, and the mask surface of the wafer S has a slope having a gentle inclination angle that does not depend on the angle of the natural crystal plane (described above). 1 mesa portion 20 corresponding to the first slope 22) is formed.

As described above, in the etching process in the mesa portion forming step, in addition to the exposed surface of the wafer S, the outer peripheral portion of the mask surface is also etched.
As a result, a recess 82 is formed on the surface of the wafer S, with the exposed surface of the wafer S being the bottom surface and the outer peripheral portion of the mask surface being the inner surface. At this time, the inner side surface of the recess 82 is formed on a slope that intersects the central portion of the mask surface (the unetched portion of the mask surface) at a gentle angle θ (0 ° <θ <20 °). .

Next, as shown in FIG. 4F, an etching process for removing the etching protective film 80 is performed.
Through the above steps, the wafer S in which the mesa portion (first mesa portion 20) is formed on the surface of the wafer S (the surface on the Y′-axis direction + side) is obtained.

  Thereafter, the wafer S on which the mesa portions (the first mesa portion 20 and the second mesa portion 30) are formed on both surfaces (the surface on the Y′-axis direction + side and the surface on the Y′-axis direction − side) of the wafer S, The piezoelectric vibrating piece 10 is obtained by etching the outer shape of the piezoelectric plate 11 and separating it from the wafer S.

  In the method for manufacturing the piezoelectric vibrating piece 10 described above, the outer shape of the piezoelectric plate 11 is formed by etching after the first mesa portion 20 (concave portion 82) is formed by etching, but the present invention is not limited to this. After the outer shape of the piezoelectric plate 11 is formed by etching, the first mesa portion 20 may be formed by etching.

As described above, the piezoelectric vibrating piece 10 of the present embodiment includes the piezoelectric plate 11 formed of the AT-cut quartz crystal substrate, and the first surface 11A and the second surface 11B of the piezoelectric plate 11 that face each other in the thickness direction. Excitation electrodes 51A and 51B formed respectively. In the present embodiment, the first surface 11A is formed with a first top surface 21 and a first slope 22 that surrounds the first top surface 21 and is inclined with respect to the first top surface 21, and the second surface 11B. The second top surface 31 and the second slope 32 surrounding the second top surface 31 and inclined with respect to the second top surface 31 are formed. The slopes 22 and 32 are respectively formed with respect to the top surfaces 21 and 31. The inclination angle is set to be less than 20 °, and in the first surface 11A, the first excitation electrode 51A is formed across the first top surface 21 and the first inclined surface 22, and in the second surface 11B, the second excitation electrode 51B. Is configured to extend over the second top surface 31 and the second slope 32.
According to this configuration, the area of the excitation electrodes 51A and 51B can be ensured as compared with the case where the excitation electrode is formed only on the top surface. Further, since the inclination angle between the first top surface 21 and the first inclined surface 22 is smaller than the inclination angle between the top surface and the inclined surface when the inclined surface is a natural crystal surface, the first top surface 21 and the first inclined surface. 22 will be connected gradually. Thereby, it can suppress that an unnecessary vibration is induced in the boundary part of the 1st top surface 21 and the 1st slope 22. As a result, the CI value can be reduced and the vibration characteristics can be improved.
The inclination angle is not limited to less than 20 °, and may be set to less than 90 °.

In the present embodiment, the piezoelectric plate 11 is formed in a rectangular shape with the Z′-axis direction of the AT-cut quartz crystal substrate as the longitudinal direction in a plan view viewed from the Y′-axis direction.
According to this configuration, a low CI value can be maintained even when the piezoelectric plate 11 is downsized.
That is, the AT-cut quartz crystal substrate is composed of an X axis and a Z ′ axis. Under such a configuration, when the AT-cut quartz substrate is undergoing thickness shear vibration, electric polarization occurs in the X axis and the Z ′ axis. Electric polarization is a charge bias, which is sinusoidal on the X axis and linear on the Z ′ axis. By setting the long side to the Z ′ axis where the electric polarization is linear, the side where the strongest charge is generated can be lengthened. The CI value becomes lower as the region where the strong charge is generated becomes wider. Therefore, it is possible to maintain a lower CI value by setting the Z ′ axis as a long side.

In the present embodiment, the outer peripheral edges of the excitation electrodes 51A and 51b in the first surface 11A and the second surface 11B are more than the outer peripheral edges of the corresponding inclined surfaces 22 and 32 in a plan view as viewed from the Y′-axis direction. It was set as the structure located inside.
According to this configuration, it is possible to suppress propagation of vibration energy to the outer peripheral edge of the piezoelectric plate 11 and to suppress unnecessary vibration from being induced at the outer peripheral edge of the piezoelectric plate 11.

  And since the piezoelectric vibrator 1 of this embodiment is provided with the piezoelectric vibration piece 10 mentioned above, the small piezoelectric vibrator 1 provided with the outstanding vibration characteristic can be obtained.

If the excitation electrodes 51A and 51B are formed over at least the top surfaces 21 and 31 and the inclined surfaces 22 and 32 in the mesa portions 20 and 30, for example, the excitation electrodes 51A and 51B are formed over the corresponding edge surfaces 24 and 34, for example. It does not matter. However, it is preferable that the outer peripheral edges of the excitation electrodes 51A and 51B are located inside the outer peripheral edges of the edge surfaces 24 and 34.
According to this configuration, since the area of the excitation electrode can be increased, the CI value can be reduced, and good thickness shear vibration can be obtained.
Here, since the edge portion 40 is thinner than the portion of the piezoelectric plate 11 where the mesa portions 20 and 30 are formed, the vibration energy generated in the edge portion 40 is the mesa portions 20 and 30. Less than the vibration energy generated. For this reason, a decrease in the CI value accompanying an increase in the area of the excitation electrode is dominant as compared with an increase in the CI value due to unnecessary vibration induced at the outer peripheral edge of the piezoelectric plate 11, and as a result, excellent vibration characteristics can be obtained. Can do.

[Second Embodiment]
Next, the piezoelectric vibrator and the piezoelectric vibrating piece according to the second embodiment will be described.
FIG. 5 is a plan view of the piezoelectric vibrating piece 110 according to the second embodiment.
The piezoelectric vibrating piece 110 shown in FIG. 5 is different from the piezoelectric vibrating piece 10 of the first embodiment in that protrusions 112A and 112B are formed on the piezoelectric plate 11.
In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 5, the piezoelectric plate 111 of the piezoelectric vibrating piece 110 of the present embodiment has a protruding portion (the first protruding portion 112 </ b> A and the first protruding portion 112 </ b> A) 2nd protrusion part 112B).

112 A of 1st protrusion parts are formed in the parallelogram by planar view. The first protrusion 112A extends in the XZ′-axis direction from the corner of the edge 40 on the + X-axis direction and the Z′-axis direction + side toward the + Z′-axis direction toward the + X′-axis direction. ing.
A first mount electrode 113A is formed on the first protrusion 112A. The first mount electrode 113A is formed over the entire surface (the first surface 111A, the second surface 111B, and the outer peripheral end surface 111C) of the first protrusion 112A. The first mount electrode 113A is arranged on the first surface 111A of the piezoelectric plate 111 (on the surface on the Y′-axis direction + side of the first protrusion 112A) via the lead wiring 116A. Are connected to the first excitation electrode 51A.

The second protrusion 112B is formed in a parallelogram in plan view. The second protrusion 112B extends in the XZ′-axis direction from the corner of the edge 40 on the + X-axis side and the Z′-axis direction−side toward the −Z′-axis direction toward the + X-axis direction. doing. That is, the protrusion 112B is separated from the first protrusion 112A in the Z′-axis direction of the quartz crystal axis.
A second mount electrode 113B is formed on the second protrusion 112B. The second mount electrode 113B is formed over the entire surface (the first surface 111A, the second surface 111B, and the outer peripheral end surface 111C) of the second protrusion 112B. The second mount electrode 113B is formed on the second surface 111B of the piezoelectric plate 111 (on the surface on the Y′-axis direction − side of the second protrusion 112B) via the routing wiring 116B. Are connected to the second excitation electrode 51B.
Note that the mount electrode 113B may be formed on at least the surface on the second surface 111B side (the Y′-axis direction-side of the second protrusion 112B).

  Here, the mount electrodes 113A and 113B and the routing wirings 116A and 116B are formed of a single layer film of metal such as gold or a laminated film having a metal such as chromium as a base layer and a metal such as gold as an upper layer. Has been.

  In the present embodiment, the thickness in the Y′-axis direction of the protruding portions 112A and 112B is equal to the separation distance between the top surfaces 21 and 31 of the mesa portions 20 and 30, but the thickness of the edge portion 40 May be equivalent.

As described above, in the present embodiment, the protruding portions 112A and 112B protruding in the surface direction of the piezoelectric plate 111 are respectively formed at both ends of the piezoelectric plate 111 that are separated in the Z′-axis direction. did.
According to this configuration, the projecting portions 112A and 112B are used as a mount region for mounting the piezoelectric vibrating piece 10 on the package 5, so that the vibration region (the portion where the excitation electrodes 51A and 51B are formed) and the mount are mounted. A space between the areas can be secured. Thereby, it is possible to suppress vibration energy generated in the vibration region from propagating to the mounting member 9 and the package 5 through the mount region, and to suppress vibration leakage. In addition, since the adhesion area between the piezoelectric plate 111 and the mounting member 9 can be ensured, the bonding strength between the mounting member 9 and the piezoelectric plate 111 can be ensured.

The protrusions 112A and 112B may be configured to contribute to at least one of electrical continuity and mechanical strength. That is, the protrusions 112 </ b> A and 112 </ b> B may be configured to be at least partially joined to the mounting member 9. In this case, for example, a part of the mounting member 9 may adhere to the edge portion 40. Further, the mount electrodes 113A and 113B may be formed on the edge 40.
Moreover, the planar view external shape of protrusion part 112A, 112B can be changed suitably.

The present invention is not limited to the above-described embodiment described with reference to the drawings, and various modifications can be considered within the technical scope thereof.
In the above-described embodiment, the configuration in which one-stage mesa portions are formed on the first surface and the second surface of the piezoelectric plate in the mesa type as the piezoelectric vibrating piece has been described, but is not limited thereto. For example, the mesa portion may be formed in multiple stages. Moreover, the structure by which the mesa part is formed in one of the 1st surface and the 2nd surface may be sufficient.
In addition, the piezoelectric vibrating piece is not limited to the mesa type, but may be a so-called bevel type (a configuration without a peripheral portion).

Further, in the above-described embodiment, a case is described in which the surface of the piezoelectric plate opposite to the surface mounted on the mounting member is the first surface and the surface mounted on the mounting member is the second surface. However, it is not limited to this. That is, the surface of the piezoelectric plate that is mounted on the mounting member may be the first surface, and the surface of the piezoelectric plate that is opposite to the surface mounted on the mounting member may be the second surface.
Further, in the above-described embodiment, the piezoelectric plate whose longitudinal direction is the Z′-axis direction in the crystal axis is described, but a piezoelectric plate whose longitudinal direction is the X-axis direction may be used.

  In addition, the constituent elements in the above-described embodiments can be appropriately replaced with known constituent elements without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric vibrator 10, 110 ... Piezoelectric vibration piece 11, 111 ... Piezoelectric plate 11A, 111A ... 1st surface 11B, 111B ... 2nd surface 13A, 113A ... 1st mount electrode (mount electrode)
13B, 113B ... second mount electrode (mount electrode)
20 ... 1st mesa part (mesa part)
21 ... 1st top surface (top surface)
22 ... 1st slope (slope)
30 ... Second mesa part (mesa part)
31 ... Second top surface (top surface)
32 ... Second slope (slope)
40 ... Edge 51A ... First excitation electrode (excitation electrode)
51B ... Second excitation electrode (excitation electrode)
112A ... 1st protrusion part (protrusion part)
112B ... 2nd protrusion part (protrusion part)

Claims (7)

A piezoelectric plate formed of an AT-cut quartz substrate;
An excitation electrode formed on each of the first surface and the second surface facing each other in the thickness direction of the piezoelectric plate;
At least on the first surface,
The top surface,
An inclined surface surrounding the top surface and inclined with respect to the top surface;
The slope is set with an inclination angle with respect to the top surface of less than 90 °,
At least in the first surface, the excitation electrode is formed across the top surface and the inclined surface. 2. The piezoelectric vibrating piece according to claim 1, wherein the inclined surface has an inclination angle with respect to the top surface of less than 20 °. 3. The piezoelectric plate according to claim 1, wherein the piezoelectric plate is formed in a rectangular shape whose longitudinal direction is the Z′-axis direction of the AT-cut quartz crystal substrate when viewed from the thickness direction. Piezoelectric vibrating piece. The protrusions protruding in the surface direction of the piezoelectric plate are respectively formed at both ends of the piezoelectric plate that are separated in the Z′-axis direction of the AT-cut quartz crystal substrate. 4. The piezoelectric vibrating piece according to any one of 3 above. 5. The outer peripheral edge of the excitation electrode is located on the inner side of the outer peripheral edge of the inclined surface in a plan view as viewed from the thickness direction, at least on the first surface. The piezoelectric vibrating piece according to any one of the preceding claims. The piezoelectric plate further includes an edge that surrounds the periphery of the slope and extends in a surface direction of the piezoelectric plate,
The edge portion is thinner than a portion including the top surface of the piezoelectric plate,
5. The piezoelectric vibrating piece according to claim 1, wherein an outer peripheral edge of the excitation electrode is disposed on the edge portion at least on the first surface. The piezoelectric vibrating piece according to any one of claims 1 to 6,
And a package on which the piezoelectric vibrating piece is mounted.

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