JP2017060125A - Piezoelectric vibration piece and piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compact piezoelectric vibration piece and piezoelectric vibrator excellent in 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. At least in the first surface 11A, a top face 21 where the excitation electrode 51A is formed, and a side face 22 surrounding the top face 21 and connected with the outer peripheral edge thereof are formed. The side face 22 includes a plurality of slopes 22a, 22b having inclination angles for the top face 21 different from each other and continuous in the thickness direction. Outer shape of the plurality of slopes 22a, 22b of the piezoelectric plate 11 in the surface direction becomes larger as separating from the top face 21.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, when the piezoelectric vibrating piece described above is reduced in size, 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 Document 1 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.

JP2013-197826A

  However, in the configuration disclosed in Patent Document 1, since the side surface of the mesa portion is formed in a stepped shape, the boundary portion of each step, the boundary portion between the top surface and the side surface of the mesa portion, and the mesa among the piezoelectric plates. The angle is largely switched at the boundary portion between the portion located outside the portion and the side surface of the mesa portion. In this case, when the vibration generated in the vibration region propagates toward the outer periphery of the piezoelectric plate, spurious vibration is induced at each boundary portion described above. As a result, there is a problem that the vibration characteristics of the piezoelectric vibrating piece deteriorate.

  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 on which the excitation electrode is formed, and a side surface connected to an outer periphery of the top surface and surrounding the top surface, The side surface includes a plurality of inclined surfaces having different inclination angles with respect to the top surface and continuing in the thickness direction, and an outer shape of the plurality of inclined surfaces in the surface direction of the piezoelectric plate increases as the distance from the top surface increases. It is characterized by.
According to the above aspect (1), since the outer shape of the side surface (slope) in the surface direction of the piezoelectric plate is larger as the distance from the top surface is larger, a stepped shape in which adjacent surfaces intersect perpendicularly in the thickness direction. Compared with the side surface, the angle formed by adjacent surfaces in the thickness direction can be made moderate. Therefore, it is possible to suppress unnecessary vibrations from being induced at the boundary portion between adjacent surfaces in the thickness direction.
In addition, the inclination angle at at least one of the boundary portion between the top surface and the side surface and the boundary portion between the side portion of the piezoelectric plate that is continuous with the outside of the side surface is equal to the side surface with respect to the top surface. Compared with the case where it is formed at such an inclination angle, it becomes gentle. Therefore, it is possible to suppress unnecessary vibrations from being induced in at least one boundary portion.
As a result, the CI value can be reduced and the vibration characteristics can be improved.

(2) In the aspect of (1), the piezoelectric plate may be formed in a rectangular shape having a longitudinal direction in the Z′-axis direction of the AT-cut quartz crystal substrate in a plan view as viewed from the thickness direction. Good.
In the case of (2), 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.

(3) In the above aspect (1) or (2), protrusions protruding in the surface direction of the piezoelectric plate are provided at both ends of the piezoelectric plate spaced apart in the Z′-axis direction of the AT-cut quartz crystal substrate. , Each may be formed.
In the case of (3) above, by using a protrusion as a mount region for mounting the piezoelectric vibrating piece on the package, the distance between the vibration region (the portion where the excitation electrode is formed) and the mount region can be 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.

(4) In any one of the above aspects (1) to (3), the side surface is on the top surface side with respect to a virtual straight line connecting the inner peripheral edge and the outer peripheral edge in a sectional view along the thickness direction. It may bulge.
In the case of the above (4), for example, when the side surface is continuous with the outer peripheral end surface of the piezoelectric plate, the boundary portion between the top surface and the side surface and the boundary portion between both the outer peripheral end surface and the side surface of the piezoelectric plate The inclination angle becomes gentler than when the side surface is formed with a uniform inclination angle with respect to the top surface. Therefore, it can suppress that an unnecessary vibration is induced in these boundary parts.

(5) In any one of the above aspects (1) to (3), the side surface has a top surface side with respect to a virtual straight line connecting an inner peripheral edge and an outer peripheral edge in a cross-sectional view along the thickness direction. May be recessed on the opposite side.
In the case of (5) above, for example, when a side edge portion surrounding the side surface is formed outside the side surface of the piezoelectric plate, the inclination angle at the boundary portion between the side surface and the side edge portion is Compared to the case where it is formed at a uniform inclination angle. Therefore, it can suppress that an unnecessary vibration is induced in this boundary part.

(6) In any one of the above aspects (1) to (5), the surface roughness of the slope may be less than 10 nm in arithmetic average roughness Ra and less than 100 nm in maximum height Ry.
In the case of (6), since the unevenness on the surface of the piezoelectric plate can be reduced, it is possible to suppress unnecessary vibrations from being induced in the uneven portion. As a result, the vibration characteristics can be further improved.

(7) In any one of the above aspects (1) to (6), the maximum length dimension of the piezoelectric plate in the plan view may be less than 2.5 mm.
In the case of (7), even if the piezoelectric vibrating piece is small, unnecessary vibrations can be prevented from being induced in the boundary portion.

(8) 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 (7), and a package on which the piezoelectric vibrating piece is mounted. And
According to the above aspect (8), since the piezoelectric vibrating piece described above 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.

It is a figure which shows the piezoelectric vibrating piece which concerns on 1st Embodiment, (a) is a top view, (b) is a fragmentary sectional view equivalent to the Ib-Ib line | wire of (a). 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 figure which shows the piezoelectric vibrating piece which concerns on 2nd Embodiment, (a) is a top view, (b) is a fragmentary sectional view equivalent to the Vb-Vb line | wire of (a). It is a fragmentary sectional view showing other composition of a piezoelectric vibrating piece.

  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 diagram illustrating a piezoelectric vibrating piece 10 according to the first embodiment. FIG. 1A is a plan view of the piezoelectric vibrating piece 10, and FIG. 1B is a partial cross-sectional view corresponding to the line Ib-Ib in FIG. 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.
In the present embodiment, the piezoelectric plate 11 has a maximum length dimension (dimension in the Z′-axis direction in the present embodiment) of less than 2.5 mm.

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 side surface 22 (side surface) surrounding the first top surface 21.
The first top surface 21 is a flat surface extending in the XZ′-axis direction. The outer shape of the first top surface 21 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 first side surface 22 connects the first top surface 21 and the edge surface 24. The outer shape of the first side surface 22 is formed in a rectangular frame shape surrounding the first top surface 21 in a plan view viewed from the Y′-axis direction. Of the first side surface 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 side surface 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 side surface 22 is in the −Y ′ axis direction from the outer peripheral edge of the first top surface 21 toward the outside (+ Z ′ axis direction, −Z ′ axis direction, −X axis direction, + X axis direction). Extends towards.

Here, the first side surface 22 is formed by connecting a plurality of slopes (first slope upper step 22a, first slope lower step 22b) having different inclination angles with respect to the first top surface 21 in the Y′-axis direction. In this case, the first side surface 22 bulges in the Y′-axis direction + side with respect to a virtual straight line L1 connecting the inner peripheral edge and the outer peripheral edge in a cross-sectional view along the Y′-axis direction.
The first slope upper step 22 a has an inner peripheral edge connected to each side of the outer peripheral edge of the first top surface 21. In the first slope upper stage 22a, the inclination angle with respect to the first top surface 21 is set to be less than 20 °.

  The first slope lower step 22b surrounds the first slope upper step 22a in plan view. The first slope lower step 22b has an inner periphery connected to an outer periphery of the first slope upper step 22a. On the other hand, the outer peripheral edge of the first slope lower step 22 b is connected to the inner peripheral edge of the edge surface 24. The first slope lower step 22b has an inclination angle with respect to the first top surface 21 larger than the inclination angle of the first slope upper step 22a. In this case, the first slope lower step 22b has an inclination angle of less than 20 ° with respect to the first slope upper step 22a.

  Thus, as the first inclined surfaces 22a and 22b are located closer to the Y′-axis direction − side, the outer shape in the XZ′-axis direction is larger. The first slope upper step 22a and the first slope lower step 22b have the same width dimension (distance from the inner peripheral edge to the outer peripheral edge in plan view as viewed from the Y′-axis direction). However, the width dimensions of the first slope upper step 22a and the first slope lower step 22b can be changed as appropriate.

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 side surface 32 (side surface) surrounding the second top surface 31.
The second top surface 31 is a flat surface extending in the XZ ′ axis direction. The outer shape of the second top surface 31 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 second side surface 32 connects the second top surface 31 and the edge surface 34. The outer shape of the second side surface 32 is formed in a rectangular frame shape surrounding the second top surface 31 in a plan view viewed from the Y′-axis direction. Of the second side surface 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 side surface 32 has 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 side 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.

Here, the second side surface 32 is formed of a plurality of slopes (second slope upper step 32a and second slope lower step 32b) having different inclination angles with respect to the second top surface 31 in the Y′-axis direction. In this case, the second side surface 32 bulges in the Y′-axis direction − side with respect to a virtual straight line L2 connecting the inner peripheral edge and the outer peripheral edge in a cross-sectional view along the Y′-axis direction.
The inner peripheral edge of the second slope upper stage 32 a is connected to each side of the outer peripheral edge of the second top surface 31. In the second slope upper stage 32a, the tilt angle with respect to the second top surface 31 is set to be less than 20 °.

  The second slope lower step 32b surrounds the second slope upper step 32a in plan view. The inner periphery of the second slope lower step 32b is connected to the outer periphery of the second slope upper step 32a. On the other hand, the outer peripheral edge of the second slope lower step 32 b is connected to the inner peripheral edge of the edge surface 34. The inclination angle of the second slope lower step 32b with respect to the second top surface 31 is larger than the inclination angle of the second slope upper step 32a. In this case, the inclination angle of the second slope lower step 32b with respect to the second slope upper step 32a is set to be less than 20 °.

  Thus, as the second inclined surfaces 32a and 32b are located on the Y′-axis direction + side, the outer shape in the XZ′-axis direction is larger. The second slope upper step 32a and the second slope lower step 32b have the same width dimension (distance from the inner peripheral edge to the outer peripheral edge in plan view as viewed from the Y′-axis direction). However, the width dimensions of the second slope upper stage 32a and the second slope lower stage 32b can be appropriately changed.

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. The outer peripheral edge of the first side surface 22 (first slope upper step 22a, first slope lower step 22b) and the outer peripheral edge of the second side surface 32 (second slope upper step 32a, second slope lower step 32b) are the Y ′ axis. They are formed so as to overlap each other in plan view as seen from the direction.
In addition, the planar view external shape of the mesa parts 20 and 30 (the top surfaces 21 and 31 and the side surfaces 22 and 32 (the inclined surfaces 22a, 22b, 32a, and 32b) 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 first excitation electrode 51 </ b> A is formed on the first top surface 21.

  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 second excitation electrode 51 </ b> B is formed on the second top surface 31.

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.

In addition, the excitation electrode 51A is formed across the first main surface 21 and the first side surface 22 (first slope upper step 22a or first slope lower step 22b) on the first surface 11A, and the excitation electrode 51B is formed on the second surface. 11B, the second main surface 31 and the second side surface 32 (the second slope upper step 32a or the second slope lower step 32b) may be formed.
According to this configuration, the area of the excitation electrode can be ensured as compared with the case where the excitation electrode is formed only on the main surface. As a result, the CI value can be reduced and the vibration characteristics can be improved.
In this case, the outer peripheral edge of the excitation electrode 51A may be disposed up to the edge surface 24, and the outer periphery of the excitation electrode 51B may be disposed up to the edge surface 34.

  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).
In the dry etching process, for example, dry etching is performed on a portion of the surface of the wafer S corresponding to the first slope upper step 22a and a portion corresponding to the second slope lower step 22b using a mask or the like (not shown). . At this time, the dry etching is performed by differentiating the etching strength for the portion corresponding to the first slope upper step 22a and the etching strength for the portion corresponding to the first slope lower step 22b.
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
Note that the range and strength of the dry etching are such that the side surface 22 (first slope upper step 22a) in the etching process (FIG. 4 (e), mesa portion forming process) for forming the side surface 22 (slope 22a, 22b) on the wafer S described later. , The first slope lower step 22b) is not particularly limited as long as the first slope lower step 22b) is provided at least within a range and strength. In addition, the number of times and time of etching may be different between the portion corresponding to the first slope upper step 22a and the portion corresponding to the second slope lower step 22b.

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 this embodiment, before performing the etching process on the wafer S in the mesa portion forming step, the wafer S is subjected to the dry etching process corresponding to the first side surface 22 (the first slope upper stage 22a and the first slope lower stage 22b). ing. For this reason, 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 side surface having the gentle inclination angle that does not depend on the angle of the natural crystal plane on the mask surface of the wafer S A first side surface 22 (corresponding to the first slope upper step 22a and the first slope lower step 22b) of the 1 mesa portion 20 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, a plurality of inclined surfaces 22a and 22b having different inclination angles are formed on the inner side surface of the recess 82 in accordance with the processing in the dry etching process described above. Specifically, the inner side surface of the recess 82 is on the first slope upper surface intersecting the central portion of the mask surface (the unetched portion of the mask surface) at a gentle angle θ (0 ° <θ <20 °). 22a and a first slope lower step 22b that intersects the first slope upper step 22a 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, 51B formed respectively, the first surface 11A is connected to the first top surface 21 on which the first excitation electrode 51A is formed, and the outer peripheral edge of the first top surface 21, A first side surface 22 that surrounds the first top surface 21, and a second top surface 31 on which the second excitation electrode 51B is formed on the second surface 11B, and an outer peripheral edge of the second top surface 31. A second side surface 32 that is connected and surrounds the second top surface 31, and the first side surface 22 has a first slope upper step 22 a and a first side that have different inclination angles with respect to the first top surface 21 and are continuous in the thickness direction. The second side surface 32 is inclined with respect to the second top surface 31. Including the second slope upper step 32a and the second slope lower step 32b that are different from each other in the thickness direction, the outer shapes of the slopes 22a, 22b, 32a, and 32b in the surface direction of the piezoelectric plate 11 are separated from the top surfaces 21 and 31. The configuration is larger.
According to this configuration, since the outer shape of the side surfaces 22 and 32 (inclined surfaces 22a, 22b, 32a, and 32b) in the surface direction of the piezoelectric plate 11 increases as the distance from the top surfaces 21 and 31 increases, in the thickness direction. The angle formed by adjacent surfaces in the thickness direction can be made gentler than a stepped side surface in which adjacent surfaces intersect perpendicularly. Therefore, it is possible to suppress unnecessary vibrations from being induced at the boundary portion between adjacent surfaces in the thickness direction.
Further, the boundary portion between the top surfaces 21 and 31 and the side surfaces 22 and 32 (slopes 22a and 32a), and the portion of the piezoelectric plate 11 that continues to the outside of the side surfaces 22 and 32 (slopes 22b and 32b) and the side surfaces 22 and 32 ( Of the boundary portions with the inclined surfaces 22b and 32b), the inclination angle at at least one of the boundary portions is gentler than that when the side surface is formed with a uniform inclination angle with respect to the top surface. Therefore, it is possible to suppress unnecessary vibrations from being induced in at least one of these boundary portions.
As a result, the CI value can be reduced and the vibration characteristics can be improved.

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 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 first side surface 22 has an inner peripheral edge (the inner peripheral edge of the first slope upper step 22a) and an outer peripheral edge (the outer peripheral edge of the first slope lower step 22b) in a cross-sectional view along the Y′-axis direction. The second side surface 32 bulges toward the first top surface 21 with respect to the imaginary straight line, and the second side surface 32 has an inner periphery (inner periphery of the second slope upper step 32a) and an outer periphery (second The configuration is such that it bulges toward the second top surface 31 with respect to a virtual straight line connecting the outer peripheral edge of the lower slope step 32b.
According to this configuration, for example, when the side surfaces 22 and 32 (inclined surfaces 22b and 32b) are connected to the outer peripheral end surface 11C of the piezoelectric plate 11, the boundary portion between the top surface 21 and the side surface 22 (inclined surface 22a), the top surface 31 and A boundary portion between the side surface 32 (the inclined surface 32a), a boundary portion between the outer peripheral end surface 11C of the piezoelectric plate 11 and the side surface 22 (the inclined surface 22b), and a boundary portion between the outer peripheral end surface 11C of the piezoelectric plate 11 and the side surface 32 (the inclined surface 32b). The inclination angle becomes gentler than when the side surface is formed with a uniform inclination angle with respect to the top surface. Therefore, it can suppress that an unnecessary vibration is induced in these boundary parts.

In the present embodiment, the surface roughness of the inclined surfaces 22a, 22b, 32a, 32b is smaller than 10 nm in terms of arithmetic average roughness Ra and smaller than 100 nm in terms of the maximum height Ry.
According to this configuration, since the unevenness on the surface of the piezoelectric plate can be reduced, it is possible to suppress unnecessary vibrations from being induced in the uneven portion. As a result, the vibration characteristics can be further improved.

  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.

In the present embodiment, the maximum length dimension of the piezoelectric plate 11 is less than 2.5 mm in a plan view seen from the Y′-axis direction.
According to this configuration, even if the piezoelectric vibrating piece 10 is small, it is possible to suppress unnecessary vibrations from being induced in the boundary portion.

[Second Embodiment]
Next, the piezoelectric vibrator and the piezoelectric vibrating piece according to the second embodiment will be described.
5A and 5B are diagrams illustrating the piezoelectric vibrating piece 110 according to the second embodiment, in which FIG. 5A is a plan view and FIG. 5B is a partial cross-sectional view corresponding to the line Vb-Vb in FIG.
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 and a mesa portion 20 ′ 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 according to the present embodiment has a protruding portion (first protruding portion 112 </ b> A and second protruding portion 112 </ b> B) in addition to the edge portion 40 similar to the first embodiment. And have. The piezoelectric plate 111 has mesa portions 20 ′ and 30 ′ instead of the mesa portions 20 and 30 of the first embodiment.
In addition, since mesa part 30 'is the structure similar to mesa part 20', description and illustration are abbreviate | omitted suitably.

The mesa portion 20 ′ is surrounded on the first surface 111 A of the piezoelectric plate 111 by slopes 22 a ′ and 22 b ′ connected at a connection angle different from the connection angle between the slopes 22 a and 22 b of the mesa portion 20 of the first embodiment. ing. The mesa portion 30 ′ (not shown) is connected to the second surface 111 B of the piezoelectric plate 111 with slopes 32 a ′ and 32 b ′ connected at a connection angle different from the connection angle between the slopes 32 a and 32 b of the mesa portion 30 of the first embodiment. (Not shown).
Hereinafter, for convenience, the mesa portions 20 and 30 may be referred to as convex-type mesa portions, and the mesa portions 20 ′ and 30 ′ may be referred to as mountain-shaped mesa portions.

The first side surface 22 ′ is recessed toward the Y′-axis direction − side with respect to a virtual straight line L <b> 1 connecting the inner peripheral edge and the outer peripheral edge in a cross-sectional view along the Y′-axis direction.
The inner periphery of the first slope upper step 22a ′ is connected to each side of the outer periphery of the first top surface 21 ′.

  The first slope lower step 22b ′ surrounds the first slope upper step 22a ′ in plan view. The inner periphery of the first slope lower step 22b ′ is connected to the outer periphery of the first slope upper step 22a ′. On the other hand, the outer peripheral edge of the first slope lower step 22 b ′ is connected to the inner peripheral edge of the edge surface 24. The first slope lower step 22b ′ has an inclination angle with respect to the first top surface 21 ′ smaller than the inclination angle of the first slope upper step 22a ′. In this case, the first slope lower step 22b ′ has an inclination angle of less than 20 ° with respect to the first slope upper step 22a ′.

Thus, as the first inclined surfaces 22a ′ and 22b ′ are located closer to the Y′-axis direction − side, the outer shape in the XZ′-axis direction is larger. The first slope upper step 22′a and the first slope lower step 22b ′ have the same width dimension (distance from the inner peripheral edge to the outer peripheral edge in plan view as viewed from the Y′-axis direction). However, the width dimension of the first slope upper step 22′a and the first slope lower step 22b ′ can be changed as appropriate.
The inclined surfaces 22a ′ and 22b ′ can be formed by appropriately adjusting the strength, range, number of times, and the like of the dry etching in the dry etching process as in the first embodiment.

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 that protrude in the surface direction of the piezoelectric plate 111 are formed at both ends of the piezoelectric plate 111 that are separated in the Z′-axis direction of the AT-cut quartz crystal substrate, respectively. It was set as the structure.
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.

Further, in the present embodiment, the first side surface 22 ′ has an inner peripheral edge (the inner peripheral edge of the first slope upper step 22a ′) and an outer peripheral edge (the outer peripheral edge of the first slope lower step 22b ′) in a cross-sectional view along the Y′-axis direction. ) With respect to the imaginary straight line connecting the first top surface 21 side and the side opposite to the first top surface 21 side.
According to this configuration, for example, when the edge portion 40 surrounding the first side surface 22 ′ is formed outside the first side surface 22 ′ of the piezoelectric plate 111, the first side surface 22 b ′ (first slope lower step 22 b ′) is formed. ) At the boundary between the edge 40 and the side edge portion 40 becomes gentler than when the side surface is formed with a uniform inclination angle with respect to the top surface. Therefore, it can suppress that an unnecessary vibration is induced in this boundary part.

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).
For example, the structure which remove | eliminated the edge part 40 from the piezoelectric plate 11 of 1st Embodiment like the piezoelectric plate 11 'shown in FIG. 6 may be sufficient.

  In the above-described embodiment, the configuration in which the same type of mesa portion (convex type or mountain shape) is formed on the first surface and the second surface of the piezoelectric plate has been described, but the present invention is not limited thereto. For example, a convex mesa portion may be formed on one of the first surface and the second surface of the piezoelectric plate, and a mountain-shaped mesa portion may be formed on the other surface.

  Moreover, although embodiment mentioned above demonstrated the structure in which the side surface of the mesa part was formed by two inclined surfaces, it is not restricted to this. For example, the side surface of the mesa portion may be formed by three or more slopes.

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.
In the embodiment described above, the piezoelectric plate having the longitudinal direction in the Z′-axis direction of the crystal axis has been described. However, a piezoelectric plate having the longitudinal direction in 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 side surface (side surface)
22a ... First slope upper stage (slope)
22b ... Lower stage of the first slope (slope)
30 ... Second mesa part (mesa part)
31 ... Second top surface (top surface)
32 ... 2nd side surface (side surface)
32a… Upper second slope (slope)
32b ... Lower stage of the 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 (8)

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,
A top surface on which the excitation electrode is formed;
A side surface connected to the outer peripheral edge of the top surface and surrounding the top surface;
The side surface includes a plurality of inclined surfaces that are different from each other in inclination angle with respect to the top surface and are continuous in the thickness direction,
The piezoelectric vibrating piece according to claim 1, wherein an outer shape of each of the plurality of inclined surfaces in the surface direction of the piezoelectric plate is larger as it is separated from the top surface. 2. The piezoelectric device 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 in a plan view as viewed from the thickness direction. Vibrating piece. The protrusion part which protrudes in the surface direction of the said piezoelectric plate is formed in the both ends spaced apart to the Z'-axis direction of the said AT cut quartz crystal board among the said piezoelectric plates, respectively. 2. The piezoelectric vibrating piece according to 2. The said side surface bulges to the said top surface side with respect to the virtual straight line which connects an inner periphery and an outer periphery in the cross sectional view which follows the said thickness direction, The any one of Claim 1 to 3 characterized by the above-mentioned. The piezoelectric vibrating piece according to 1. The said side surface is dented in the opposite side to the said top surface side with respect to the virtual straight line which connects an inner periphery and an outer periphery in the cross sectional view in the said thickness direction. 2. The piezoelectric vibrating piece according to claim 1. 6. The piezoelectric vibrating piece according to claim 1, wherein the surface roughness of the slope is smaller than 10 nm in arithmetic average roughness Ra and smaller than 100 nm in maximum height Ry. 7. The piezoelectric vibrating piece according to claim 1, wherein a maximum length of the piezoelectric plate is less than 2.5 mm in the plan view. The piezoelectric vibrating piece according to any one of claims 1 to 7,
And a package on which the piezoelectric vibrating piece is mounted.

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