JP2013143682A - Piezoelectric vibration element, piezoelectric vibration element manufacturing method, piezoelectric vibrator, electronic device, and electronic apparatus - Google Patents

Abstract

A piezoelectric vibration element having a fundamental wave, a high frequency, a small size, a small main vibration CI value, and a large spurious CI value ratio is obtained.
A piezoelectric vibration element includes a thin vibration region and a piezoelectric substrate having a thick portion integrated along three sides excluding one side of the vibration region, and a front surface and a back surface of the vibration region. Are provided with excitation electrodes 25a and 25b and lead electrodes 27a and 27b, respectively. The thick portion is continuously provided between the first thick portion 14 and the second thick portion 16 that are arranged to face each other with the vibration region 12 interposed therebetween, and the base end portions of the first and second thick portions. The third thick portion 18 is provided. The second thick portion 16 includes an inclined portion 16b continuously provided on one side of the vibration region 12, a thick second thick portion main body 16a provided continuously on the other side of the inclined portion 16b, and at least one stress. A relaxation slit 20 is provided.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric vibrator that excites a thickness shear vibration mode, and in particular, a piezoelectric vibration element having a so-called inverted mesa structure, a method for manufacturing the piezoelectric vibration element, a piezoelectric vibrator, an electronic device, and a piezoelectric vibrator according to the present invention. The present invention relates to an electronic device using the.

AT-cut quartz resonators have thickness shear vibration as the main vibration mode to be excited, and are suitable for miniaturization and higher frequency, and exhibit a cubic curve with excellent frequency temperature characteristics. Used in many ways.
Patent Document 1 discloses an AT-cut crystal resonator having a so-called inverted mesa structure in which a concave portion is formed on a part of a main surface to increase the frequency. A so-called Z ′ long substrate is used in which the length in the Z′-axis direction of the quartz substrate is longer than the length in the X-axis direction.
Patent Document 2 discloses an AT-cut quartz having an inverted mesa structure in which a thick support portion (thick portion) is connected to each of three sides of a rectangular thin-walled vibrating portion, and a thick portion is provided in a U-shape. An oscillator is disclosed. Further, the quartz crystal resonator piece is an in-plane rotated AT-cut quartz substrate formed by rotating the X-axis and the Z′-axis of the AT-cut quartz substrate in the range of −120 ° to + 60 ° around the Y′-axis, It is said to be a structure that secures a vibration region and is excellent in mass productivity (multiple picking).

In Patent Documents 3 and 4, there is an AT-cut crystal resonator having an inverted mesa structure in which a thick support portion is connected to each of three sides of a rectangular thin vibration portion and a thick portion is provided in a U-shape. The so-called X long substrate in which the length in the X-axis direction of the crystal substrate is longer than the length in the Z′-axis direction is used for the quartz crystal resonator element.
Patent Document 5 discloses an AT-cut quartz crystal resonator having an inverted mesa structure in which a thick support portion is connected to two adjacent sides of a rectangular thin vibration portion and a thick portion is provided in an L shape. It is disclosed. A Z ′ long substrate is used as the quartz substrate.
However, in Patent Document 5, in order to obtain an L-shaped thick portion, as described in FIGS. 1 (c) and 1 (d) of Patent Document 5, along the line segment α and the line segment β. The thick part is deleted, but the deletion is based on the premise that it will be deleted by machining such as dicing, so the chipping or cracking damage will occur on the cut surface, and the ultra thin part will be damaged. There is. In addition, problems such as generation of unnecessary vibration that causes spurious noise and an increase in CI value occur in the vibration region.
Patent Document 6 discloses an AT-cut crystal resonator having an inverted mesa structure in which a thick support portion is provided continuously only on one side of a thin vibration portion.

Patent Document 7 discloses an AT-cut vibrator having an inverted mesa structure in which a concave portion is formed so as to be opposed to each other on both main surfaces and front and back surfaces of a quartz substrate. An X long substrate is used as the quartz substrate, and a structure is proposed in which excitation electrodes are provided in a region where the flatness of the vibration region formed in the recessed portion is ensured.
By the way, it is known that the thickness-shear vibration mode excited in the vibration region of the AT-cut crystal resonator has an elliptical shape in which the vibration displacement distribution has a major axis in the X-axis direction due to the anisotropy of the elastic constant. Patent Document 8 discloses a piezoelectric vibrator that excites thickness-shear vibration having a pair of ring-shaped electrodes arranged symmetrically on the front and back surfaces of a piezoelectric substrate. The difference between the outer peripheral diameter and the inner peripheral diameter of the ring electrode is set so that the ring electrode excites only the symmetrical zero-order mode and hardly excites the other nonharmonic higher-order modes.

Patent Document 9 discloses a piezoelectric vibrator in which the shape of a piezoelectric substrate and excitation electrodes provided on the front and back surfaces of the piezoelectric substrate are both elliptical.
Patent Document 10 discloses that both ends of the quartz substrate in the longitudinal direction (X-axis direction) and both ends of the electrode in the X-axis direction are semi-elliptical, and the ratio of the major axis to the minor axis of the ellipse (long) A crystal resonator having an axis / short axis) of approximately 1.26 is disclosed.
Patent Document 11 discloses a crystal resonator in which an elliptical excitation electrode is formed on an elliptical crystal substrate. The ratio of the major axis to the minor axis is preferably 1.26: 1, but considering the variation in manufacturing dimensions, the range of 1.14 to 1.39: 1 is practical.

Patent Document 12 discloses a piezoelectric vibrator having a structure in which a notch or a slit is provided between a vibrating part and a support part in order to further improve the energy confinement effect of the thickness-slip piezoelectric vibrator.
By the way, when the piezoelectric vibrator is reduced in size, the residual stress caused by the adhesive causes deterioration of electrical characteristics and frequency aging failure. Patent Literature 13 discloses a crystal resonator in which a notch or a slit is provided between a vibrating portion and a support portion of a rectangular flat plate AT-cut crystal resonator. By using such a structure, it is possible to suppress the residual stress from spreading to the vibration region.
Patent Document 14 discloses a vibrator in which a notch or a slit is provided between a vibrating portion and a support portion of an inverted mesa piezoelectric vibrator in order to improve (relax) mount strain (stress). . Patent Document 15 discloses a piezoelectric vibrator in which conduction between electrodes on the front and back surfaces is ensured by providing a slit (through hole) in a support portion of an inverted mesa piezoelectric vibrator.

Patent Document 16 discloses a crystal resonator that suppresses an unnecessary mode of a higher-order contour system by providing a slit in a support portion of an AT-cut crystal resonator in a thickness shear vibration mode.
Further, in Patent Document 17, a spurious structure is provided by providing a slit in a connecting portion of a thin vibrating portion of an inverted mesa AT-cut crystal resonator and a thick holding portion, that is, a residue portion having an inclined surface. A vibrator that suppresses the above is disclosed.

JP 2004-165743 A JP 2009-164824 A JP 2006-203700 A JP 2002-198772 A JP 2002-033640 A JP 2001-144578 A JP 2003-264446 A JP-A-2-079508 JP 9-246903 A JP 2007-158486 A JP 2007-214941 A Japanese Utility Model Publication No. 61-187116 Japanese Patent Laid-Open No. 9-326667 JP 2009-158999 A JP 2004-260695 A JP 2009-188483 A JP 2003-087087 A

In recent years, there has been a strong demand for miniaturization, high frequency, and high performance of piezoelectric devices. However, the piezoelectric vibrator having the above-described structure has the CI value of the main vibration and the adjacent spurious CI value ratio (= CIs / CIm, where CIm is the CI value of the main vibration, and CIs is the CI value of the spurious. It has been found that there is a problem that one example cannot satisfy the requirement.
Therefore, the present invention has been made to solve at least a part of the above-described problems, and aims to increase the frequency (100 to 500 MHz band), reduce the CI value of the main vibration, and increase the electrical ratio such as the spurious CI value ratio. An object of the present invention is to provide a piezoelectric vibration element that satisfies the requirements, a method for manufacturing the piezoelectric vibration element, a piezoelectric vibrator, an electronic device, and an electronic apparatus using the piezoelectric vibrator of the present invention.

  The present invention can be realized as the following forms or application examples.

  [Application Example 1] A piezoelectric vibration element according to the present invention includes a vibration substrate, a piezoelectric substrate including a thick portion thicker than the vibration region integrated with the vibration region, and a front surface and a back surface of the vibration region. And a lead electrode extending from the excitation electrode on the thick portion, and the thick portion opens a part of the vibration region. As described above, the first thick portion and the second thick portion disposed with the vibration region interposed therebetween are connected to the base end portions of the first thick portion and the second thick portion. A third thick portion provided, and the second thick portion has a thickness as it is separated from one end edge connected to the vibration region toward the other end edge. An inclined portion that increases, and a thick-walled main body that is connected to the other end edge of the inclined portion, and the second thick-walled portion includes a slip portion. Wherein the is provided.

The high-frequency fundamental wave piezoelectric vibration element is miniaturized and the spread of stress due to adhesion and fixation can be suppressed. Therefore, it has excellent frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics, and is capable of suppressing main vibration. There is an effect that a piezoelectric vibration element having a small CI value and a ratio of the CI value of the adjacent spurious to the CI value of the main vibration, that is, a large CI value ratio can be obtained.
Application Example 2 In the piezoelectric vibration element according to Application Example 1, the vibration area is rectangular, and one of four sides of the vibration area is open.

  Since one side of the four sides of the vibration region is open, a thick portion in that direction is not formed. For this reason, it becomes possible to reduce the size of the piezoelectric vibration element.

  [Application Example 3] In the piezoelectric vibration element according to Application Example 1, wherein the slit is disposed in the thick-walled body along a boundary portion between the inclined portion and the thick-walled body. is there.

  Since it is possible to suppress the spread of stress generated when the piezoelectric vibration element is bonded and fixed, there is an effect that a piezoelectric vibration element having excellent frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics can be obtained.

  Application Example 4 In the piezoelectric vibration element according to Application Example 1, the slit is disposed in the inclined portion so as to be separated from one side of the vibration region.

  Since the slits can be easily formed and the spread of stress generated when the piezoelectric vibration element is bonded and fixed can be suppressed, a piezoelectric vibration element having excellent frequency temperature characteristics and CI temperature characteristics can be obtained. is there.

  Application Example 5 In addition, the slit includes a first slit disposed in the thick body, and a second slit disposed in the inclined portion so as to be separated from one side of the vibration region. The piezoelectric vibration element according to Application Example 1, wherein the piezoelectric vibration element is provided.

  Since it is possible to better suppress the spread of stress generated when the piezoelectric vibration element is bonded and fixed, a piezoelectric vibration element having excellent frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics can be obtained. There is an effect.

  Application Example 6 In the piezoelectric vibration element, one main surface of the vibration region and one surface of each of the first, second, and third thick portions are in the same plane. The piezoelectric vibration element according to any one of Application Examples 1 to 5, characterized by:

  When a vibration region is formed by etching a piezoelectric substrate from only one side, it is possible to form a vibration region that maintains the cutting angle of the original substrate, and a high-frequency fundamental piezoelectric device with excellent frequency-temperature characteristics. There is an effect that a vibration element is obtained.

  Application Example 7 In the piezoelectric vibration element, the piezoelectric substrate includes an X axis as an electric axis that is a crystal axis of crystal, a Y axis as a mechanical axis, and a Z axis as an optical axis. Centering on the X axis of the coordinate system, the Z axis is inclined by a predetermined angle in the −Y direction of the Y axis as a Z ′ axis, and the Y axis is in the + Z direction of the Z axis. A quartz substrate that is formed by a plane parallel to the X-axis and the Z′-axis, with the axis tilted only by the Y′-axis and having a thickness in a direction parallel to the Y′-axis, and a side parallel to the X-axis The piezoelectric vibration element according to any one of Application Examples 1 to 6, wherein the piezoelectric vibration element is a quartz substrate having a long side and a short side parallel to the Z ′ axis.

  There is an effect that a piezoelectric vibration element having excellent temperature characteristics can be obtained.

  Application Example 8 The piezoelectric vibration element according to Application Example 7, wherein the quartz crystal substrate is an AT cut quartz crystal substrate.

  By using a quartz AT-cut quartz substrate as a piezoelectric substrate, it is possible to utilize many years of experience and experience related to photolithography and etching, so that not only mass production of piezoelectric substrates is possible, but also high-accuracy etching, piezoelectric vibration elements The yield is significantly improved.

[Application Example 9]
A step of providing a concave portion including a vibration region on one of the front and back surfaces of the piezoelectric substrate; and a thick portion in which the piezoelectric substrate including a part of the concave portion is removed and a part of the concave portion is opened. And a step of forming an outer shape including a slit, and a step of forming an electrode in a predetermined region including the front and back surfaces of the vibration region.

  According to the method of manufacturing a piezoelectric vibration element described in this application example, the frequency temperature characteristic, the CI temperature characteristic, and the frequency aging characteristic are excellent, the CI value of the main vibration is small, and the spurious adjacent to the CI value of the main vibration is low. There is an effect that a piezoelectric vibration element having a large CI value ratio, that is, a large CI value ratio can be easily manufactured.

  Application Example 10 A piezoelectric vibrator of the present invention includes the piezoelectric vibration element according to any one of application examples 1 to 8, and a package that accommodates the piezoelectric vibration element.

  Piezoelectric vibration with excellent frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics, since the high-frequency fundamental piezoelectric vibrator is downsized and stress due to adhesion and fixation can be suppressed. There is an effect that a child is obtained. Furthermore, the CI value of the main vibration is reduced, and the ratio of the spurious CI value to the CI value of the main vibration, that is, a piezoelectric vibrator having a large CI value ratio is obtained, and a piezoelectric vibrator having a small capacitance ratio is obtained. effective.

  Application Example 11 An electronic device according to this application example is characterized in that the package includes the piezoelectric vibration element according to any one of Application Examples 1 to 8 and an electronic component.

  By configuring a piezoelectric device (for example, a voltage control type piezoelectric oscillator) as described above, a voltage control type piezoelectric oscillator having excellent frequency reproducibility, frequency temperature characteristics, and aging characteristics, a small size and a high frequency (for example, 490 MHz band) can be obtained. There is an effect that it is. In addition, since the piezoelectric device uses the piezoelectric resonator element 1 of the fundamental wave, there is an effect that a voltage controlled piezoelectric oscillator having a small capacitance ratio, a wide frequency variable width, and a good S / N ratio can be obtained.

  Application Example 12 In the electronic device according to Application Example 11, the electronic component is any one of a variable capacitance element, a thermistor, an inductor, and a capacitor.

  By configuring an electronic device as described above, it is possible to configure an electronic device such as a piezoelectric oscillator, a temperature compensated piezoelectric oscillator, and a voltage-controlled piezoelectric oscillator, and a piezoelectric with excellent frequency reproducibility and aging characteristics. It is possible to obtain an oscillator, a temperature compensated piezoelectric oscillator having excellent frequency temperature characteristics, and a voltage-controlled piezoelectric oscillator having a stable frequency, a wide variable range, and a good S / N ratio (signal to noise ratio). .

  Application Example 13 An electronic device according to this application example includes a package including the piezoelectric vibration element according to any one of application examples 1 to 8 and an oscillation circuit that excites the piezoelectric vibration element. It is characterized by.

  By configuring the piezoelectric device as described above, it is possible to obtain an electronic device such as a piezoelectric oscillator having excellent frequency reproducibility and aging characteristics.

  Application Example 12 An electronic device according to this application example includes the piezoelectric vibrator according to Application Example 9.

  By using the piezoelectric vibrator described in the above application example for an electronic device, there is an effect that an electronic device including a reference frequency source having a high frequency and excellent frequency stability and a good S / N ratio can be configured.

It is the schematic which showed the structure of the piezoelectric vibration element which concerns on 1st Embodiment, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing, ( d), (e), and (f) are QQ sectional views showing a modified example of a slit shape. The figure explaining the relationship between an AT cut quartz substrate and a crystal axis. (A), (b) and (c) is a top view which shows the structure of the modification of a piezoelectric vibration element. It is the schematic which showed the structure of the piezoelectric vibration element which concerns on 2nd Embodiment, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing. It is the schematic which showed the structure of the piezoelectric vibration element which concerns on 3rd Embodiment, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing, d) And (e) is a top view which shows the other structural example. Explanatory drawing which shows the manufacturing process of a piezoelectric substrate. Explanatory drawing which shows the manufacturing process of the excitation electrode and lead electrode of a piezoelectric vibration element. (A) is a top view of the recessed part formed in the piezoelectric wafer, (b)-(e) is sectional drawing of the X-axis direction of a recessed part. (A) is a top view of the recessed part formed in the piezoelectric wafer, (b)-(e) is sectional drawing of the Z'-axis direction of a recessed part. The structure of the piezoelectric vibrator which concerns on 4th Embodiment is shown, (a) is a longitudinal cross-sectional view, (b) is a top view from the P direction. The structure of the piezoelectric vibrator which concerns on 5th Embodiment is shown, (a) is a longitudinal cross-sectional view, (b) is a top view from the P direction. The characteristic of a piezoelectric vibrator is shown, (a) is a figure which shows a frequency temperature characteristic, (b) is a figure which shows CI temperature characteristic. The characteristics of a piezoelectric vibrator are shown, (a) And (b) is a figure which shows the distribution characteristic of a capacitance ratio, (c) And (d) is a figure which shows the distribution characteristic of an electrostatic capacitance. The characteristic of a piezoelectric vibrator is shown, (a) And (b) is a figure which shows the distribution characteristic of CI value ratio. The modification of a piezoelectric vibration element is shown, (a) and (b) is a perspective view, (c) is a longitudinal cross-sectional view. The characteristic explanatory view of the piezoelectric vibrator as a piezoelectric device. The structure of the piezoelectric device which concerns on 6th Embodiment is shown, (a) is a longitudinal cross-sectional view, (b) is a top view from the P direction. The structure of the piezoelectric device which concerns on 7th Embodiment is shown, (a) And (b) is a longitudinal cross-sectional view. The longitudinal cross-sectional view which shows the modification of a piezoelectric substrate. The application example of a piezoelectric substrate is shown, (a)-(c) is a structure explanatory drawing of a piezoelectric substrate. The application example of a piezoelectric substrate is shown, (a)-(c) is a structure explanatory drawing of a piezoelectric substrate. (A) And (b) is a principal part top view which shows the structural example of a mount part, and sectional drawing. FIG.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the piezoelectric vibration element according to the first embodiment of the present invention. 1A is a plan view of the piezoelectric vibration element 1, FIG. 1B is a cross-sectional view taken along the line PP, FIG. 1C is a cross-sectional view taken along the line Q-Q, and FIGS. And (f) are QQ cross-sectional views showing a modification of the slit shape.
The piezoelectric vibration element 1 includes a thin vibration region 12 and a piezoelectric substrate 10 having thick portions 14, 16, and 18 connected to the vibration region 12, and both main surfaces of the vibration region 12 on the front and back sides. Excitation electrodes 25a and 25b formed so as to face each other, and lead electrodes 27a and 27b formed extending from the excitation electrodes 25a and 25b toward the pad electrodes 29a and 29b provided in the thick portions, respectively It is equipped with.

The piezoelectric substrate 10 has a substantially rectangular and rectangular shape, and has a thin and flat vibration region 12 and a U-shaped thick portion (thickness) integrated along three sides excluding one side of the vibration region 12. Meat support portion) 13. The thick portion 13 includes a first thick portion 14 and a second thick portion 16 that are disposed to face each other with the vibration region 12 interposed therebetween, and the first thick portion 14 and the second thick portion 16. A U-shaped configuration including a third thick portion 18 that continuously connects between the base end portions.
That is, the thick portion 13 includes the first thick portion 14 and the first thick portion 14 that are disposed to face each other with the vibration region 12 therebetween so as to open one side (a part of the vibration region 12) of the four sides of the vibration region 12. 2 thick portions 16, and a third thick portion 18 connecting the base end portions of the first thick portion 14 and the second thick portion 16. Here, “open” includes the case where one side is exposed and the case where a part is not exposed but completely exposed.
In the present specification, the concave portion 11 side is the front surface, and the flat surface that is the surface opposite to the front surface is the back surface.
The first thick portion 14 is connected to one side 12 a of the thin flat plate-like vibration region 12, and the thickness increases from one end edge connected to the one side 12 a of the vibration region 12 toward the other end edge. A first inclined portion 14b that gradually increases and a thick square columnar first thick portion main body 14a that is connected to the other end edge of the first inclined portion 14b are provided. Similarly, the second thick portion 16 is connected to one side 12b of the thin flat plate-like vibration region 12, and is separated from one end edge connected to the one side 12b of the vibration region 12 toward the other end edge. And a thick quadrangular columnar second thick portion main body 16a provided continuously with the other end edge of the sloping portion 16b.
The thick-walled body refers to a region having a constant thickness parallel to the Y ′ axis.

The third thick portion 18 is connected to one side 12c of the vibration region 12 having a thin flat plate shape, and the thickness increases from one edge connected to the one side 12c of the vibration region 12 toward the other edge. A gradually increasing third inclined portion 18b and a thick quadrangular columnar third thick portion main body 18a connected to the other end edge of the third inclined portion 18b are provided. That is, the thin vibration region 12 is a recessed portion 11 that is surrounded on the three sides by the first, second, and third thick portions 14, 16, and 18, and the other one side is open.
Note that one main surface of the vibration region 12 and one surface of each of the first, second, and third thick portions 14, 16, and 18 are on the same plane, that is, the X of the coordinate axis shown in FIG. It is on the −Z ′ plane, and this surface (the lower surface side in FIG. 1B) is referred to as a flat surface, and the opposite surface (the upper surface side in FIG. 1B) is referred to as a concave surface.

Further, in the piezoelectric substrate 10, at least one stress relaxation slit 20 is formed through the second thick portion 16. In the embodiment shown in FIG. 1, the slit 20 is formed in the surface of the second thick portion main body 16 a along the connecting portion between the inclined portion 16 b and the second thick portion main body 16 a.
The slit 20 is not limited to a through-hole formed as shown in FIG. 1C, and may be a groove-shaped slit having a bottom. The groove-shaped slit will be described in detail. For example, as shown in FIG. 1D, the first slit 20a having the bottom formed from the surface side of the second thick portion 16 and the second thick wall are formed. The second slit 20b formed from the back surface side of the portion 16 and having the bottom portion may be formed by slits provided from both the front and back surfaces. Moreover, as shown in FIG.1 (e), it may be comprised from the 3rd slit 20c which is formed from the surface side of the 2nd thick part 16, and has a bottom part. Moreover, as shown in FIG.1 (d), the structure provided with the 4th slit 20d which is formed from the back surface side of the 2nd thick part 16, and has a bottom part may be sufficient.
The shape of the slit 20 described here can be applied to other embodiments, modifications, and application examples described below.

A piezoelectric material such as quartz belongs to the trigonal system and has crystal axes X, Y, and Z orthogonal to each other as shown in FIG. The X axis, the Y axis, and the Z axis are referred to as an electric axis, a mechanical axis, and an optical axis, respectively. In the quartz substrate, a flat plate cut out from the quartz is used as a piezoelectric vibration element along a plane obtained by rotating the XZ plane around the X axis by a predetermined angle θ. For example, in the case of the AT-cut quartz substrate 101, θ is approximately 35 ° 15 ′. Note that the Y-axis and the Z-axis are also rotated by θ around the X-axis to be the Y′-axis and the Z′-axis, respectively. Accordingly, the AT-cut quartz crystal substrate 101 has crystal axes X, Y ′, and Z ′ that are orthogonal to each other. The AT-cut quartz crystal substrate 101 has a thickness direction of the Y ′ axis, an XZ ′ plane (a plane including the X axis and the Z ′ axis) orthogonal to the Y ′ axis is a main surface, and a thickness shear vibration is a main vibration. Excited. The AT-cut quartz substrate 101 can be processed to obtain the piezoelectric substrate 10.
That is, as shown in FIG. 2, the piezoelectric substrate 10 is centered on the X axis of an orthogonal coordinate system composed of an X axis (electrical axis), a Y axis (mechanical axis), and a Z axis (optical axis), and the Z axis is the Y axis. The axis tilted in the −Y direction is the Z ′ axis, the Y axis is the Y ′ axis is the axis tilted in the + Z direction of the Z axis, and is composed of surfaces parallel to the X and Z ′ axes. It consists of an AT-cut quartz substrate with the thickness in the parallel direction.
The piezoelectric substrate according to the present invention is not limited to the AT cut with the angle θ of approximately 35 ° 15 ′, but can be widely applied to a piezoelectric substrate such as a BT cut that excites thickness shear vibration. Needless to say.

As shown in FIG. 1A, the piezoelectric substrate 10 has a direction parallel to the X axis (hereinafter referred to as “X axis”) with a direction parallel to the Y ′ axis (hereinafter referred to as “Y ′ axis direction”) as a thickness direction. It has a rectangular shape having a long side as a “direction” and a short side as a direction parallel to the Z ′ axis (hereinafter referred to as “Z ′ direction”).
In the embodiment shown in FIG. 1, the excitation electrodes 25 a and 25 b that drive the piezoelectric substrate 10 have a quadrangular shape, and are formed so as to face both the front and back surfaces (main surfaces of the front and back surfaces) of the substantially central portion of the vibration region 12. At this time, the size of the excitation electrode 25b on the flat surface side (hereinafter also referred to as “flat surface side” and the back surface side in FIG. 1B) is the concave surface side (the upper surface side in FIG. 1B). The excitation electrode 25a is set to a sufficiently large size. This is because the energy confinement coefficient due to the mass effect of the excitation electrode is not increased more than necessary. That is, by sufficiently increasing the excitation electrode 25b on the flat surface side, the plate back amount Δ (= (fs−fe) / fs, where fs is the cutoff frequency of the piezoelectric substrate, and fe is the excitation electrode on the entire surface of the piezoelectric substrate. The frequency when the is attached depends only on the mass effect of the excitation electrode 25a on the concave surface side.

The excitation electrodes 25a and 25b are formed by depositing, for example, nickel (Ni) on a base and superposing gold (Au) thereon using a vapor deposition apparatus or a sputtering apparatus. The thickness of the gold (Au) is within a range in which the ohmic cross does not increase, and only the main vibration is set as the confinement mode (S0), and the oblique symmetric inharmonic mode (A0, A1,...) And the symmetric inharmonic mode (S1, S3,. •)) should not be in confinement mode. However, for example, in the case of a piezoelectric vibration element in a 490 MHz band, it is inevitable that a low-order inharmonic mode is confined to some extent when a film is formed so as to avoid ohmic crossing of the electrode film thickness.
The excitation electrode 25a formed on the concave surface side is a lead electrode that extends from the excitation electrode 25a so as to pass through the third inclined portion 18b and the third thick portion main body 18a from above the vibration region 12. 27a is conductively connected to a pad electrode 29a formed on the upper surface of the second thick part main body 16a. The excitation electrode 25b formed on the flat surface side is connected to the pad electrode 29b formed on the back surface (lower surface) of the second thick portion main body 16a by the lead electrode 27b passing through the edge portion of the piezoelectric substrate 10. Conductive connection.

The embodiment shown in FIG. 1A is an example of a lead-out structure of the lead electrodes 27a and 27b, and the lead electrode 27a may pass through another thick part. However, it is desirable that the length of the lead electrodes 27a and 27b is the shortest, and it is desirable to suppress the increase in capacitance by considering that the lead electrodes 27a and 27b do not intersect with each other with the piezoelectric substrate 10 interposed therebetween.
In the embodiment of FIG. 1, an example is shown in which the pad electrodes 29 a and 29 b are formed on the front and back (upper and lower) surfaces of the piezoelectric substrate 10, respectively, but when the piezoelectric vibration element 1 is housed in a package, the piezoelectric vibration element 1. The pad electrode 29a and the package terminal electrode are mechanically fixed and electrically connected with a conductive adhesive, and the pad electrode 29b and the package terminal electrode are electrically connected using a bonding wire. . Thus, when the site | part which supports the piezoelectric vibration element 1 becomes one point, it is possible to make small the stress resulting from a conductive adhesive.
Furthermore, an oscillation circuit for driving the piezoelectric vibration element 1, for example, an IC chip is mounted inside the package, and the terminal pad electrode is electrically connected to the electrode pad electrically connected to the IC chip. A piezoelectric oscillator may be configured by the above. It is preferable to fix and connect with a conductive adhesive, and to connect the pad electrode 29b and the connection terminal of the IC chip mounted on the package with a bonding wire. Thus, when the site | part which supports the piezoelectric vibration element 1 becomes one point, it is possible to make small the stress resulting from a conductive adhesive.
In addition, the pad electrodes 29a and 29b may be juxtaposed on the back surface side of the piezoelectric substrate 10 with a space therebetween. When conducting connection between the pad electrodes 29a and 29b and the terminal electrode of the package housing the piezoelectric vibration element 1 using a conductive adhesive, the pad electrodes 29a and 29b are spaced apart from the back side of the piezoelectric substrate. A juxtaposed configuration is preferred.

The reason why the slit 20 is provided between the vibration region 12 and the pad electrodes 29a and 29b which are thick portions of the piezoelectric vibration element 1 is to prevent the spread of stress generated when the conductive adhesive is cured.
That is, when the piezoelectric vibration element 1 is supported on the package by the conductive adhesive, first, the conductive adhesive is applied to the pad electrode 29a (supported portion) of the second thick portion main body 16a, and this is applied to the package. Place it on the terminal electrode, etc. In order to cure the conductive adhesive, it is held at a high temperature for a predetermined time. In the high temperature state, both the second thick part main body 16a and the package expand and the adhesive temporarily softens, so that no stress is generated in the second thick part main body 16a. After the conductive adhesive is cured, when the second thick portion main body 16a and the package are cooled and the temperature returns to room temperature (25 ° C.), the conductive adhesive, the package, and the second thick portion Due to the difference from each linear expansion coefficient of the main body 16a, the stress generated from the cured electroconductive adhesive is transferred from the second thick portion main body 16a to the first and third thick portions 14, 18 and the vibration region 12. spread. In order to prevent the spread of the stress, a slit 20 for stress relaxation is provided.

In order to obtain the stress (strain) distribution generated in the piezoelectric substrate 10, a simulation is generally performed using a finite element method. As the stress in the vibration region 12 is reduced, a piezoelectric vibration element having excellent frequency temperature characteristics, frequency reproducibility, and frequency aging characteristics can be obtained.
Examples of the conductive adhesive include silicone-based, epoxy-based, polyimide-based, and bismaleimide-based. A polyimide-based conductive adhesive is used in consideration of frequency aging due to degassing of the piezoelectric vibration element 1. . Since the polyimide-based conductive adhesive is hard, it can reduce the magnitude of the stress generated by supporting one place rather than supporting two separate places. For example, in the high frequency band of 100 to 500 MHz, for example, the 490 MHz band The piezoelectric vibration element 1 for the voltage controlled piezoelectric oscillator (VCXO) of FIG. That is, the pad electrode 29b is mechanically fixed and electrically connected to the terminal electrode A of the package using conductive bonding, and the other pad electrode 29a is electrically connected to the terminal electrode B of the package using the bonding wire. Decided to connect to.
Further, the piezoelectric substrate 10 shown in FIG. 1 has a so-called X-long in which the length in the X-axis direction is longer than the length in the Z′-axis direction. This is because stress occurs when the piezoelectric substrate 10 is fixed and connected with a conductive adhesive or the like, but as is well known, the frequency when force is applied to both ends along the X-axis direction of the AT-cut quartz substrate. Comparing the change and the frequency change when the same force is applied to both ends along the Z′-axis direction, the frequency change is smaller when the force is applied to both ends in the Z′-axis direction. That is, it is preferable to provide the support points along the Z′-axis direction because the frequency change due to stress is reduced.

(Modified example of piezoelectric vibration element)
FIG. 3 is a modification of the piezoelectric vibration element 1 according to the embodiment shown in FIG. 1, and only a plan view is shown here. In the embodiment shown in FIG. 1, the thin vibration region 12 is literally rectangular (rectangular), but in the modification shown in FIG. 3A, the third thick portion of the thin vibration region 12 is used. 18 in that both corners corresponding to both ends of one side 12c corresponding to 18 are chamfered. Thus, the piezoelectric substrate 10 having a structure in which the corners of the vibration region 12 are chamfered as in the modification described in FIG. Is included in the concept of a substantially square.

In the modified examples of FIGS. 1 and 3A, the excitation electrodes 25a and 25b have a quadrilateral shape, that is, a square shape or a rectangular shape (the long side is in the X-axis direction). There is no. In the modification shown in FIG. 3B, the excitation electrode 25a on the concave surface side (front surface side) is circular, and the excitation electrode 25b on the flat surface side (back surface side) is a quadrangle sufficiently larger than the excitation electrode 25a. . The excitation electrode 25b on the flat surface side (back surface side) may also be a sufficiently large circle.
In the modification shown in FIG. 3C, the excitation electrode 25a on the concave surface side (front surface side) is an ellipse, and the excitation electrode 25b on the flat surface side (back surface side) is a square that is sufficiently larger than the excitation electrode 25a. is there. Due to the anisotropy of the elastic constant, the displacement distribution in the X-axis direction and the displacement amount in the Z′-axis direction are different, and the cut surface obtained by cutting the displacement distribution along a plane parallel to the XZ ′ plane is elliptical. Therefore, the piezoelectric vibration element 1 can be driven most efficiently when the elliptical excitation electrode 25a is used. That is, the capacitance ratio γ (= C0 / C1, where C0 is the capacitance and C1 is the series resonance capacitance) of the piezoelectric vibration element 1 can be minimized. The excitation electrode 25a may be oval.

(Second Embodiment)
FIG. 4 is a schematic diagram illustrating the configuration of the piezoelectric vibration element according to the second embodiment. 4A is a plan view of the piezoelectric vibration element, FIG. 4B is a cross-sectional view taken along the line PP, and FIG. 4C is a cross-sectional view taken along the line QQ.
The piezoelectric vibrating element 2 is different from the piezoelectric vibrating element 1 shown in FIG. 1 in the position where the stress relaxation slit 20 is provided. In this example, the slit 20 is formed in the inclined portion 16 b that is separated from the edge of the one side 12 b of the thin vibration region 12. Rather than forming the slit 20 in the inclined portion 16b so that one edge of the slit 20 is in contact with the one side 12b along the one side 12b of the vibration region 12, the slit 20 is separated from both end edges of the inclined portion 16b. Is provided. That is, in the inclined portion 16b, an extremely fine inclined portion 16bb connected to the edge of the one side 12b of the vibration region 12 is left. In other words, an extremely fine inclined portion 16bb is formed between the side 12a and the slit 20.

  The reason for leaving the ultra-fine inclined portion 16bb is as follows. That is, when the vibration region 12 is excited by applying a high frequency voltage to the excitation electrodes 25a and 25b arranged in the vibration region 12, in addition to the main vibration (S0), the inharmonic mode (A0, S1, A1, S2,.・ ・) Is excited. Desirably, only the main vibration (S0) mode is set as a confinement mode, and the other inharmonic modes are set as propagation modes (non-confinement mode). However, the vibration region 12 becomes thin, and its fundamental frequency is several hundred MHz. Then, in order to avoid ohmic cross of the electrode film, the excitation electrode needs to have a predetermined thickness or more. For this reason, when the thickness of the excitation electrode is not less than the predetermined thickness, a low-order inharmonic mode close to the main vibration is excited. The inventor of the present application has come to realize that in order to suppress the magnitude of the amplitude of the low-order inharmonic mode, it is only necessary to prevent the condition that the standing wave of the inharmonic mode is established. That is, the shape of both end edges in the Z′-axis direction of the vibration region 12 in FIG. 4 is asymmetric, and the shape of both end edges in the X-axis direction is also asymmetric by leaving the strip 16bb, and the lower-order inharmonic mode. We realized that the amplitude of the standing wave was suppressed.

(Third embodiment)
FIG. 5 is a schematic diagram illustrating the configuration of the piezoelectric vibration element according to the third embodiment. 5A is a plan view of the piezoelectric vibration element, FIG. 5B is a cross-sectional view taken along the line PP, FIG. 5C is a cross-sectional view taken along the line QQ, and FIG. FIG.
The piezoelectric vibrating element 3 is different from the piezoelectric vibrating element 1 shown in FIG. 1 in that a first slit 20a is provided in the surface of the second thick portion main body 16a and a second in the surface of the inclined portion 16b. The slit 20b is formed and two stress relaxation slits are provided. The purpose of forming individual slits (the first slit 20a and the second slit 20b) in the surface of the second thick portion main body 16a and in the surface of the inclined portion 16b has already been described as described above. Therefore, it is omitted here.
The first slit 20a and the second slit 20b are not juxtaposed in the X-axis direction as in the plan view shown in FIG. 5A, but are shown in FIG. 5D or FIG. 5E. In this way, they may be arranged in steps so as to be separated from each other in the Z′-axis direction. The provision of the two slits 20 a and 20 b can prevent the stress caused by the conductive adhesive from spreading to the vibration region 12.

6 and 7 are cross-sectional views of a process flow for explaining a manufacturing process relating to the formation of the recessed portion 11, the outer shape, and the slit 20 of the piezoelectric substrate 10. Here, a quartz wafer will be described as an example of the piezoelectric wafer. In step S1, a quartz wafer 10W having a predetermined thickness, eg, 80 μm, whose both surfaces are polished is sufficiently washed and dried, and then chromium (Cr) is ground on the front and back surfaces by sputtering or the like. A metal film (corrosion resistant film) M in which gold (Au) is laminated is formed.
In step S2, a photoresist film (hereinafter referred to as a “resist film”) R is applied on the entire surface of the front and back metal films M. In step S3, the resist film R at a position corresponding to the recessed portion 11 is exposed using a mask pattern and an exposure apparatus. When the exposed resist film R is developed and the exposed resist film is peeled off, the metal film M at a position corresponding to the recessed portion 11 is exposed. When the gold layer film M exposed from the resist film R is dissolved and removed using a solution such as aqua regia, the crystal plane at the position corresponding to the recessed portion 11 is exposed.

In step S4, the exposed quartz surface is etched to a desired thickness using a mixed liquid of hydrofluoric acid (hydrofluoric acid) and ammonium fluoride. In step S5, the resist film R is removed using a predetermined solution, and the exposed metal film M is removed using aqua regia or the like. At this stage, the quartz wafer 10W is in a state in which the recessed portions 11 are regularly arranged in a lattice pattern on one surface.
The above-described steps S1 to S5 correspond to the step of providing the recessed portion 11 including the vibration region 12.

In step S6, a metal film (Cr + Au) M is formed on both surfaces of the quartz wafer 10W obtained in step S5. In step S7, a resist film R is applied to both surfaces of the metal film (Cr + Au) M formed in step S6.
In step S8, the outer shape of the piezoelectric substrate 10 and the resist film R at a position corresponding to the slit 20 are exposed from both sides using a predetermined mask pattern and an exposure apparatus, developed and peeled off. Further, the exposed metal film M is removed by dissolving with a solution such as aqua regia.

In step S9, the exposed quartz surface is etched using a mixed liquid of hydrofluoric acid (hydrofluoric acid) and ammonium fluoride to form the outer shape of the piezoelectric substrate 10 and the slit 20. When the slit 20 is formed in a shape having a bottom (see FIG. 1D) from both the front and back sides of the quartz wafer 10W, the width of the resist film R at the position corresponding to the slit 20 is reduced. It can be formed by using a change in etching rate caused by the above. In step S10, the remaining resist film R is peeled off, and the exposed excess metal film M is dissolved and removed. At this stage, the quartz-crystal wafer 10W is in a state where the piezoelectric substrates 10 are connected by supporting strips and are arranged in a lattice pattern.
Steps S6 to S10 described above correspond to the step of forming the outer shape including the vibration region 12 having the thick portion where the recessed portion 11 is partially opened and the slit 20.
The feature of this embodiment is that, as shown in steps S8 and S9, a part of the vibration region 12 of the recessed portion 11 and the fourth thick portion 19 connected to the vibration region 12 are removed by etching. That is. Thereby, size reduction of a piezoelectric substrate is achieved. Details will be described later.

  After step S10 is completed, the thickness of the vibration region 12 of each piezoelectric substrate 10 regularly arranged in a lattice pattern on the quartz wafer 10W is optically measured, for example. When the measured thickness of each vibration region 12 is thicker than a predetermined thickness, the thickness is finely adjusted so as to fall within the predetermined thickness range.

After adjusting the thickness of the vibration region 12 of each piezoelectric substrate 10 formed on the quartz wafer 10W within a predetermined thickness range, the excitation electrodes 25a and 25b and the lead electrodes 27a and 27b are attached to each piezoelectric substrate 10. A forming procedure will be described with reference to FIG.
In step S11, nickel (Ni) is formed on the entire front and back surfaces of the quartz wafer 10W by sputtering or the like, and gold (Au) is stacked thereon to form a metal film M. Next, in step S12, a resist is applied on the metal film M to form a resist film R.
In step S13, the resist film R at a position corresponding to the excitation electrodes 25a and 25b and the lead electrodes 27a and 27b is exposed using the mask pattern Mk. In step S14, the exposed resist film R is developed to remove the unnecessary resist film R using a solution. Next, the metal film M exposed by peeling off the resist film R is dissolved and removed with a solution such as aqua regia.
In step S15, when the unnecessary resist film R remaining on the metal film M is peeled off, excitation electrodes 25a and 25b, lead electrodes 27a and 27b, and the like are formed on each piezoelectric substrate 10. By dividing the half-etched support strip connected to the quartz wafer 10W, the divided piezoelectric vibration element 1 is obtained.
Steps S11 to S15 described above correspond to the step of forming electrodes in a predetermined region including the front and back surfaces of the vibration region 12.

By the way, when the crystal is wet-etched, the etching proceeds along the Z-axis, but has an etching anisotropy peculiar to the crystal in which the etching rate varies depending on the direction of each crystal axis. Therefore, the etching surface that appears due to the anisotropy of the etching appears to differ depending on the direction of each crystal axis. Has been discussed. However, despite this background, there is no clearly organized data on the etching anisotropy of quartz, and the nanofabrication technical aspects are so strong that the etching conditions (types of etching solutions) Depending on the literature, there are many cases where there are differences in the crystal planes appearing, depending on the difference in the etching rate and etching temperature.
Therefore, the inventor of the present application repeatedly performed etching simulation and prototype experiment, and nano-level surface analysis and observation in manufacturing the piezoelectric vibration element according to the present invention using the photolithography technique and the wet etching technique. Such a piezoelectric vibrator has been found to have the following modes, and will be described in detail below.

8 and 9 are views for explaining the cross-sectional shape of the recessed portion 11 on the AT-cut quartz crystal wafer 10W formed by etching.
FIG. 8A is a plan view of the crystal wafer 10W in step S5 of FIG. At this stage, the concave portions 11 are regularly formed in a lattice shape on one surface of the quartz wafer 10W. FIG. 8B is a cross-sectional view in the X-axis direction, and each wall surface of the recessed portion 11 is not a vertical wall surface but an inclined surface. That is, the wall surface in the −X axis direction forms the inclined surface X1, and the wall surface in the + X axis direction forms the inclined surface X2. When a groove perpendicular to the X axis is formed, the wall surface X3 of the cross section of the groove has a wedge shape. FIGS. 8C to 8E are enlarged views of the wall surfaces X1 and X2 of the recessed portion 11 and the wall surface X3 of the groove portion. The wall surface in the −X-axis direction is etched with an inclination of approximately 62 degrees with respect to the plane of the crystal wafer 10W, as shown in FIG. As shown in FIG. 8D, the wall surface in the + X axis direction is perpendicular to the plane of the crystal wafer 10W (90 degrees) and the etching proceeds slightly, but thereafter, the etching proceeds with a gentle inclination. The bottom surface of the recess 11 along the X-axis direction is etched in parallel with the original plane of the crystal wafer. That is, the vibration region 12 has a flat plate shape whose front and back surfaces are parallel.
FIG. 8E is a cross-sectional view of a groove portion for breaking formed in the quartz wafer 10W. The cross section of the groove formed perpendicular to the X axis has a wedge shape. This is because the wall surface X3 of the groove portion is formed by the wall surface X1 in the −X axis direction and the wall surface X2 in the + X axis direction, so that it becomes a wedge shape.
When providing an electrode on the surface on which the recessed portion 11 is formed, it is necessary to pay attention to the vertical wall surface of the wall surface X2 formed in the + X axis direction. It is desirable to avoid the electrode film because it tends to tear.

FIG. 9 is a view for explaining the wall surface of the recess 11 formed in the piezoelectric substrate 10, particularly in the Z′-axis direction cross section. FIG. 9A is a plan view of the quartz wafer 10W. FIG. 9B is a cross-sectional view of the quartz wafer 10W in the Z′-axis direction. The wall surface in the −Z′-axis direction forms an inclined surface Z1, and the wall surface in the + Z′-axis direction forms an inclined surface Z2. When the groove portion orthogonal to the Z ′ axis is formed, the wall surface Z3 of the cross section of the groove portion has a wedge shape.
FIGS. 9C to 9E are enlarged views of the wall surfaces Z1 and Z2 of the recessed portion 11 and the wall surface Z3 of the groove portion. The wall surface in the −Z′-axis direction is etched with a relatively gentle inclination with respect to the plane of the crystal wafer 10 </ b> W, as shown in FIG. As shown in FIG. 9D, the wall surface Z2 in the + Z′-axis direction is etched with a steeply inclined surface Z2a with respect to the plane of the crystal wafer 10W, but thereafter, etching proceeds with a gently inclined surface Z2b. After that, the inclined surface Z2c becomes gentler. FIG. 9E is a cross-sectional view of a groove portion formed perpendicular to the Z′-axis direction, which is a wedge-shaped cross section Z3. This groove portion is a groove portion for breaking the crystal wafer 10W. Since the wall surface Z3 of the groove is formed of the wall surface Z1 in the -Z 'axis direction and the wall surface Z2 in the + Z' axis direction, the wall surface Z2a and the wall surface Z2b have a substantially wedge-shaped cross section. If the groove for folding is formed in the X-axis direction and the Z′-axis direction, the cross-sectional shape becomes a wedge shape, and the folding is easy.

One of the features of the present invention is that, as shown in FIG. 9 (d), a gentle inclined surface Z2c that is not parallel to the original plane on the right side of the dotted line indicated by Zc in the vibration region 12 is a fourth feature. This is because the piezoelectric substrate is miniaturized by removing it together with the thick portion 19 by etching.
Further, since the manufacturing method has been established on the premise that the gently inclined surface Z2c is deleted together with the fourth thick portion 19, the area of the flat ultrathin portion that becomes the vibration region 12 is determined as the prior art. Compared to the conventional structure having thick wall portions existing at both ends of the vibration region 12 along the X-axis as described above, it is ensured to be secured. Therefore, in the thickness-shear vibration mode excited in the vibration region 12, it is possible to design with sufficient consideration that the vibration displacement distribution becomes an ellipse having a major axis in the X-axis direction due to the anisotropy of the elastic constant. Therefore, the ratio of the major axis to the minor axis is preferably 1.26: 1. However, considering the variation in manufacturing dimensions, etc., it is sufficiently designed to be in the range of 1.14 to 1.39: 1. It has become possible.

Furthermore, as shown in FIG. 15, in the outer shape of the piezoelectric vibration element 1, an inclined surface appears on the end surface that intersects the X axis, and an inclined surface (1) appears on the (−) side end surface of the X axis, It is found that the inclined surface (2) appears on the single surface on the (+) side, and the shapes of the inclined surface (1) and the inclined surface (2) are different in the cross section parallel to the XY ′ plane. It was also found out. FIG. 15 shows a modification of the piezoelectric vibration element, in which (a) and (b) are perspective views, and (c) is a longitudinal sectional view.
Further, both the inclined surfaces (1) and (2) are perpendicular to the wall surface X2 formed in the + X-axis direction as shown in FIGS. 8B and 8E in the vicinity where they intersect with the main surface of the piezoelectric substrate 10. The walls are not visible. The reason for this is that, compared to the etching time required to form the recessed portion 11, the time for forming the inclined surface (1) and the inclined surface (2) starts etching the piezoelectric substrate (quartz substrate) 10 from the front and back, Since the etching is performed until the front and back sides penetrate, the vertical wall surface does not appear due to the overetching action because the etching time is sufficiently long.
It has been found that the inclined surfaces a1 and a2 constituting the inclined surface (1) are substantially symmetrical with respect to the X axis.
In the inclined surfaces b1, b2, b3, and b4 constituting the inclined surface (2), it has been found that b1 and b4 and b2 and b3 are substantially symmetrical with respect to the X axis.
Furthermore, it was found that the inclination angle α of the inclined surfaces a1 and a2 with respect to the X axis has a relationship of β <α as compared with the inclination angle β of the inclined surfaces b1 and a4 with respect to the X axis.

(Fourth embodiment)
10A and 10B show the configuration of the piezoelectric vibrator according to the fourth embodiment, where FIG. 10A is a cross-sectional view, and FIG. 10B is a plan view seen from the direction P shown in FIG.
The piezoelectric vibrator 5 includes, for example, the above-described piezoelectric vibration element 1 and a package that accommodates the piezoelectric vibration element 1. The package includes a package main body 40 formed in a rectangular box shape and a lid member 49 made of metal, ceramic, glass, or the like.
As shown in FIG. 10, the package body 40 is formed by laminating a first substrate 41, a second substrate 42, and a third substrate 43, and an aluminum oxide ceramic as an insulating material. -It is formed by forming a green sheet into a box and then sintering it. A plurality of mounting terminals 45 are formed on the outer bottom surface of the first substrate 41. The third substrate 43 is an annular body from which the central portion is removed, and a metal seal ring 44 such as Kovar is formed on the upper peripheral edge of the third substrate 43.

The third substrate 43 and the second substrate 42 form a recess that accommodates the piezoelectric vibration element 1. A plurality of element mounting pads 47 that are electrically connected to the mounting terminals 45 by conductors 46 are provided at predetermined positions on the upper surface of the second substrate 42.
The position of the element mounting pad 47 is arranged so as to correspond to the pad electrode 29a formed on the second thick portion main body 16a when the piezoelectric vibration element 1 is placed.

The piezoelectric vibrator 5 is configured by applying an appropriate amount of a conductive adhesive 30, for example, a polyimide-based adhesive with less degassing, to the element mounting pad 47 of the package body 40, and the pad electrode 29 a of the piezoelectric vibrating element 1 and the package thereon. The terminal electrode (pad 47) is placed with one point of support and is mechanically fixed under load and electrically connected. As a characteristic of the conductive adhesive 30, the magnitude of stress (strain) due to the conductive adhesive 30 increases in the order of a silicone-based adhesive, an epoxy-based adhesive, and a polyimide-based adhesive. Further, degassing increases in the order of polyimide adhesive, epoxy adhesive, and silicone adhesive.
The pad electrode 29b and the terminal electrode 48 of the package may be electrically connected using the bonding wire BW. Thus, when the site | part which supports the piezoelectric vibration element 1 becomes one point, it is possible to make small the stress resulting from a conductive adhesive.

In order to cure the conductive adhesive 30 of the piezoelectric vibration element 1 mounted on the package body 40, it is necessary to put it in a high temperature furnace at a predetermined temperature for a predetermined time. After the annealing treatment, the frequency is adjusted by adding mass to the excitation electrodes 25a and 25b or reducing the mass. The lid member 49 is sealed by seam welding on a seal ring 44 formed on the upper surface of the package body 40. Alternatively, there is also a method in which the lid member 49 is placed on the low melting point glass applied to the upper surface of the package body 40 and melted and adhered. The package cavity is evacuated or filled with an inert gas such as nitrogen N ₂ to complete the piezoelectric vibrator 5.
In the embodiment of the piezoelectric vibrator 5 described above, an example in which a laminated plate is used for the package body 40 has been described. However, a piezoelectric element is formed using a cap that uses a single-layer ceramic plate for the package body 40 and a lid body that is drawn. An oscillator may be configured.

(Fifth embodiment)
Next, a piezoelectric vibrator according to a fifth embodiment will be described with reference to FIG. 11 shows the configuration of the piezoelectric vibrator, FIG. 11A is a cross-sectional view, and FIG. 11B is a plan view seen from the direction P shown in FIG. 11A. Since the piezoelectric vibrator 5a has a configuration in which a part of the piezoelectric vibrator 5 is deformed, differences from the piezoelectric vibrator 5 will be described, and the same components as those of the piezoelectric vibrator 5 will be denoted by the same reference numerals. A description will be omitted.
Excitation electrodes 25a and 25b are formed on the front and back surfaces of the piezoelectric vibration element 1 used in the piezoelectric vibrator 5a. The excitation electrodes 25a and 25b are formed to face both the front and back surfaces of the substantially central portion of the vibration region 12. The excitation electrode 25a is electrically connected to the pad electrode 29a formed on the surface of the second thick portion main body 16a by the lead electrode 27a. The excitation electrode 25b is conductively connected to the pad electrode 29b formed on the back surface of the second thick portion main body 16a by the lead electrode 27b. Note that the pad electrode 29a and the pad electrode 29b are arranged (arranged) so as to be separated from each other in plan view.
Further, although not shown, the pad electrode 29b extends through the side surface of the second thick part main body 16a to the surface of the second thick part main body 16a. In the piezoelectric vibration element 1, the pad electrode 29 b and the pad electrode 29 a extending to the surface of the second thick part main body 16 a are mechanically fixed to the element mounting pad 47 of the package main body 40 by the conductive adhesive 30. And electrically connected.
In this configuration, the pad electrode 29a and the pad electrode 29b are separated from each other in a plan view of the piezoelectric vibration element 1 and are provided on the same surface (back surface), so that the piezoelectric vibration element 1 is fixed to the element mounting pad 47. It becomes possible to carry out only with the conductive adhesive 30.

  FIGS. 12A and 12B are diagrams showing an example of the electrical characteristics of the piezoelectric vibrators 5 and 5a according to the present invention. As an example, the resonance frequency is a fundamental wave mode and the resonance frequency is set to 123 MHz. This frequency band was developed with the intention of a crystal resonator for a voltage-controlled piezoelectric oscillator (VCXO). 12A shows frequency temperature characteristics of the piezoelectric vibrators 5 and 5a in the temperature range of −40 ° C. to 85 ° C. FIG. 12B shows the CI (crystal impedance) of the piezoelectric vibrators 5 and 5a in the same temperature range. It is a temperature characteristic. The frequency-temperature characteristic shown in FIG. 12A exhibits a smooth cubic curve and satisfies the required standard. In addition, the CI temperature characteristic of FIG. 12B also exhibits good characteristics without CI dip over the entire temperature range.

FIG. 13A shows the distribution of the capacitance ratio γ of the piezoelectric vibrators 5 and 5a according to the present invention. The average value of γ is 273, and the standard deviation σ is 18. FIG. 13B shows the distribution of the capacitance ratio γ of the conventional piezoelectric vibrator. The average value of γ is 296, and the standard deviation σ is 26.
FIG. 13C shows the distribution of the electrostatic capacitance C0 of the piezoelectric vibrators 5 and 5a of the present invention. The average value of C0 is 1.80 (pF), and the standard deviation σ is 0.01. It was. FIG. 13D shows the distribution of the capacitance C0 of the conventional piezoelectric vibrator. The average value of C0 is 1.88 and the standard deviation σ is 0.02.
FIG. 14A shows the spurious CI value ratio (= CIs / CIm, CIm is the CI value of the main vibration, and CIs is the largest spurious CI value close to the main vibration) of the piezoelectric vibrators 5 and 5a of the present invention. FIG. 14B shows a distribution of spurious CI value ratios of the conventional piezoelectric vibrator.
As apparent from FIGS. 13 and 14, the piezoelectric vibrators 5 and 5a according to the present invention are superior to the conventional piezoelectric vibrator in terms of the capacitance ratio γ, the capacitance C0, and the spurious CI value ratio. I found out. Moreover, the piezoelectric vibrators 5 and 5a according to the present invention are also downsized.

As shown in FIG. 1, since the high-frequency fundamental piezoelectric vibration element can be miniaturized and the spread of stress due to adhesion / fixation can be suppressed, frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, In addition, there is an effect that a piezoelectric vibration element having excellent frequency aging characteristics and a small CI value of the main vibration and a ratio of the CI value of the adjacent spurious to the CI value of the main vibration, that is, a large CI value ratio can be obtained.
In addition, by forming the vibration region by etching the piezoelectric substrate from only one surface, it becomes possible to form a vibration region that maintains the cutting angle of the original substrate, and a high-frequency fundamental wave with excellent frequency-temperature characteristics. There is an effect that a piezoelectric vibration element can be obtained. In addition, when the slit 20 is formed in the inclined portion 16b as shown in FIG. 4, there is an effect that the slit can be easily penetrated.

By using a quartz AT-cut quartz substrate as a piezoelectric substrate, the results and experience of photolithographic techniques and etching techniques for many years can be utilized, so that not only mass production of piezoelectric substrates is possible, but also high-precision etching is possible. There is an effect that the yield of the vibration element is greatly improved.
When the piezoelectric vibrator is configured as shown in FIG. 10 and FIG. 11, the high frequency fundamental wave piezoelectric vibrator can be miniaturized and stress due to adhesion / fixation can be suppressed. There is an effect that a piezoelectric vibrator excellent in frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics can be obtained. Furthermore, the CI value of the main vibration is reduced, a ratio of the CI value of the adjacent spurious to the CI value of the main vibration, that is, a piezoelectric vibration element having a large CI value ratio, and a piezoelectric vibrator having a small capacitance ratio γ can be obtained. There is an effect.

Next, the resonance frequency was further increased, and a 491 (MHz) band piezoelectric vibrator was prototyped and evaluated.
The table below shows the values obtained by fabricating three 491 (MHz) piezoelectric vibrator samples and measuring the equivalent circuit constant for each sample. It was confirmed that sufficiently good electrical characteristics such as a capacity ratio γ and a capacitance C0 were obtained.

  A VCXO was manufactured using a 491 (MHz) piezoelectric vibrator according to the present invention. FIG. 16 shows an evaluation result of frequency temperature characteristics of the VCXO. It exhibits a smooth cubic curve, meets the required standards, and has good characteristics without dip over the entire temperature range.

(Sixth embodiment)
FIG. 17 is a cross-sectional view showing a configuration of a piezoelectric oscillator which is a kind of electronic device according to the sixth embodiment, where (a) is a front cross-sectional view, and (b) is a plane viewed from the P direction of (a). FIG.
The piezoelectric oscillator 6 includes a package main body 40 and a lid member 49 constituted by three layers of base materials 41, 42, 43, the piezoelectric vibration element 1, and an IC component 51 on which an oscillation circuit for exciting the piezoelectric vibration element 1 is mounted. And an electronic component 52 such as a variable thermistor whose capacitance changes with voltage, a thermistor whose resistance changes with temperature, and an inductor.
A conductive adhesive (polyimide) 30 is applied to the element mounting pad 47 of the package body 40, and the piezoelectric vibration element 1 is placed thereon to conduct with a pad electrode (not shown). The other pad electrode is connected to the other terminal pad of the package main body 40 by a bonding wire BW, so as to conduct with one terminal of the IC component 51. The IC component 51 and the electronic component 52 are fixed and connected to predetermined positions on the package body 40. A mounting terminal 45 is formed on the back surface (mounting surface) of the package body 40. The mounting terminal 45 is electrically connected to each terminal provided inside the package body 40 by a connection wiring 45.
The package body 40 is filled with an inert gas such as vacuum or nitrogen, and the package body 40 is sealed with a lid member 49 to complete the piezoelectric oscillator 6.

(Seventh embodiment)
The configuration of a piezoelectric oscillator which is a kind of electronic device according to the seventh embodiment will be described with reference to FIG. FIG. 18 shows the configuration of the piezoelectric device according to the seventh embodiment, wherein (a) and (b) are longitudinal sectional views of the piezoelectric oscillator.
In the piezoelectric oscillator 6 according to the sixth embodiment shown in FIG. 17, the piezoelectric vibration element 1, the IC component 51, and the electronic component are arranged on the same piezoelectric substrate, but the seventh embodiment of FIG. The piezoelectric oscillator 7 uses an H-type package body 60, accommodates the piezoelectric vibration element 1 in the upper part, fills the inside of the cavity with vacuum or nitrogen N ₂ gas, and seals it with a lid member 49. In FIG. 18A, the lower housing portion includes an IC component 51 on which an oscillation circuit, an amplification circuit, and the like for exciting the piezoelectric vibration element 1 are mounted, a variable capacitance element, and an inductor, thermistor, capacitor, and the like as necessary. The electronic component 52 is electrically connected to and connected to the terminal 67 of the package body 60 through connection means such as a metal bump (Au bump) 68. Since the piezoelectric oscillator 7 according to the present invention separates the piezoelectric vibration element 1 from the IC component 51 and the electronic component 52, the piezoelectric oscillator 7 is excellent in frequency aging.
Further, as shown in FIG. 18B, the lower storage portion may have at least one electronic component Th. For example, a thermistor, a capacitor, a reactance element, or the like can be applied as the electronic component Th, and an electronic device using a piezoelectric vibration element as a frequency oscillation source can be constructed.

As shown in FIG. 17, FIG. 18 (a), FIG. 18 (b), by configuring a piezoelectric device (for example, a voltage-controlled piezoelectric oscillator), the frequency reproducibility, frequency temperature characteristics, and aging characteristics are excellent, and the size is small. In addition, there is an effect that a voltage controlled piezoelectric oscillator having a high frequency (for example, 490 MHz band) can be obtained. In addition, since the piezoelectric device uses the piezoelectric resonator element 1 of the fundamental wave, there is an effect that a voltage controlled piezoelectric oscillator having a small capacitance ratio, a wide frequency variable width, and a good S / N ratio can be obtained.
In addition, piezoelectric devices such as piezoelectric oscillators, temperature compensated piezoelectric oscillators, and voltage controlled piezoelectric oscillators can be configured as piezoelectric devices. Piezoelectric oscillators with excellent frequency reproducibility and aging characteristics, temperature compensation with excellent frequency temperature characteristics The piezoelectric oscillator has an effect that it is possible to obtain a voltage-controlled piezoelectric oscillator having a stable frequency, a wide variable range, and a good S / N ratio (signal to noise ratio).

FIG. 19 is a longitudinal sectional view showing a modified example of the piezoelectric substrate, and is a configuration example in which a step portion is formed in the thick portion of the piezoelectric substrate and an inclined surface is formed on the outer peripheral side surface of the thick portion.
The piezoelectric substrate 10a shown in FIG. 19 has a thin vibration region 12, a thick first thick portion main body 14a connected to the vibration region 12, and a first structure similar to the configuration described in the above embodiment. Two thick part main bodies 16a are provided. In the figure, the third thick part main body is omitted. Excitation electrodes 25a and 25b formed on both main surfaces of the vibration region 12 so as to face each other, and pad electrodes 29a and 29b provided on the thick portions 14 and 16 from the excitation electrodes 25a and 25b, respectively. And a lead electrode (not shown) formed so as to extend toward the surface. In addition, a stepped portion 16a ′ formed with a step from one main surface is formed on the upper surface side of the second thick portion main body 16a in the figure (the side where the excitation electrode 25b is provided). The pad electrode 29b described above is provided on the surface of the step portion 16a ′. The pad electrode 29b is electrically connected to a terminal electrode of a package (not shown) by a bonding wire BW. Moreover, the inclined surface 13b is formed in the outer peripheral side surface of the thick part 16a of the piezoelectric substrate 10a.

  By providing the step portion 16a 'as in this example, the height of the pad electrode 29b connecting the bonding wire BW becomes lower than one main surface. In the piezoelectric substrate 10a, the surface on which the pad electrode 29a is formed is fixed to the fixed surface of the package (not shown). Accordingly, it is possible to reduce the loop height of the bonding wire BW as viewed from the above-described fixed surface, and the effect of reducing the height of the piezoelectric device using the piezoelectric substrate 10a of this example is obtained.

[Application example 1 of piezoelectric substrate]
The piezoelectric substrate 10 in the application example of FIG. 20A is provided on the thin portion (concave portion 11) having the vibration region 12 and the periphery of the thin portion, and the first thick portion main body 14a that is thicker than the thin portion. The second thick portion main body 16a and the thick portion 13 composed of the third thick portion main body 18a are provided. Mount portions M are provided side by side in the second thick-walled portion main body 16a with buffer portions S in the direction of the edge. The buffer portion S has a slit 20 between the mount portion M and the second thick portion main body 16a, and the mount portion M includes the mount portion M, the buffer portion S, and the second thick portion main body 16a. Chamfered portions 21 are provided at both ends in the direction orthogonal to the direction in which they are arranged.

The piezoelectric substrate 10 of FIG. 20B is provided on the thin wall portion (recessed portion 11) having the vibration region 12 and the periphery of the thin wall portion, and the first thick wall main body 14a and the second thicker than the thin wall portion. The thick part main body 16a and the thick part 13 composed of the third thick part main body 18a are provided.
Mount parts M are connected to the second thick part main body 16a side by side through the buffer part S. The buffer portion S has a slit 20 between the mount portion M and the second thick portion main body 16a, and the mount portion M includes the mount portion M, the buffer portion S, and the second thick portion main body 16a. Notches 22 are provided at both ends in the direction orthogonal to the direction of alignment.
The longitudinal direction of the slit 20 is parallel to the orthogonal direction. Further, the longitudinal width of the slit 20 is wider than the width of the mount portion M in the orthogonal direction, and both end portions of the slit 20 in the longitudinal direction are outer peripheries of the buffer portion S in the orthogonal direction than both ends of the mount portion M. It is provided near.

The piezoelectric substrate 10 of FIG. 20C is provided on the thin wall portion (recessed portion 11) having the vibration region 12 and the periphery of the thin wall portion, and the first thick wall main body 14a and the second thicker than the thin wall portion. The thick part main body 16a and the thick part 13 composed of the third thick part main body 18a are provided.
The buffer portion S and the mount portion M are sequentially connected to the second thick portion main body 16a. The buffer part S has a slit 20 between the mount part M and the second thick part main body 16a. The mount part M is characterized by having notches 22 at both ends in a direction orthogonal to the direction in which the mount part M, the buffer part S, and the second thick part main body 16a are arranged.

FIG. 21 is characterized in that it takes the form of two-point support with respect to the structure of FIG.
20 and 21, the inclined portion is not illustrated on the inner wall of each thick portion main body 14 a, 16 a, 18 a of the thick portion 13, and the outer side wall surface of the thick portion 13 is not illustrated. Although the inclined surface 13b as shown in FIG. 19 is not illustrated, these inclined portions and the inclined surface 13b are formed in corresponding portions.
In addition, each code | symbol in FIG. 20, FIG. 21 respond | corresponds with the site | part which the same code | symbol of said each embodiment shows.

[Application example 2 of piezoelectric substrate]
Furthermore, the application examples of FIGS. 22A and 22B show the configuration of the mount portion, FIG. 22A is a plan view of the mount portion, and FIG. It is A sectional drawing.
As shown in FIG. 22, the mount portion M is configured to have an uneven shape in order to improve the adhesive strength. By making the mount portion M uneven as described above, the surface area of the mount portion M increases. The mounting strength can be improved.

(Electronics)
FIG. 23 is a schematic configuration diagram showing a configuration of an electronic apparatus according to the present invention. The electronic device 8 includes the piezoelectric vibrator 5 described above. An example of the electronic device 8 using the piezoelectric vibrator 5 is a transmission device. In these electronic devices 8, the piezoelectric vibrator 5 is used as a reference signal source, a voltage variable piezoelectric oscillator (VCXO), or the like, and can provide a small-sized electronic device having good characteristics.
As described above, the piezoelectric vibrator according to the present invention is preferably used as a reference frequency source having a high frequency and excellent frequency stability and a good S / N ratio. For this reason, by using the piezoelectric vibrator according to the present invention, there is an effect that it is possible to configure an electronic device for which high performance and high reliability are desired, which can be used for a communication base station, for example.

  1, 2, 3 ... piezoelectric vibration element, 5, 5a ... piezoelectric vibrator, 6, 7 ... piezoelectric device, 8 ... electronic device, 10 ... piezoelectric substrate, 10W ... crystal wafer, 11 ... recessed portion, 12 ... vibration region, 12a, 12b, 12c ... one side of the vibration region, 13 ... thick part, 14 ... first thick part, 14a ... first thick part body, 14b ... first inclined part, 16 ... second thickness Meat part, 16a ... second thick part main body, 16bb ... strip, 16b ... inclined part, 18 ... third thick part, 18a ... third thick part main body, 18b ... third inclined part, DESCRIPTION OF SYMBOLS 19 ... 4th thick part, 20 ... Slit, 20a ... 1st slit, 20b ... 2nd slit, 25a, 25b ... Excitation electrode, 27a, 27b ... Lead electrode, 29a, 29b ... Pad electrode, 30 ... Conductive adhesive, 40 ... package body, 41 ... first substrate, 42 ... second substrate, 4 DESCRIPTION OF SYMBOLS 3 ... 3rd board | substrate, 44 ... Seal ring, 45 ... Mounting terminal, 46 ... Conductor, 47 ... Element mounting pad, 49 ... Lid member, 51 ... IC component, 52 ... Electronic component, 60 ... Package main body, 61 ... Lid 65, mounting terminals, 66, conductors, 67, component terminals, 68, metal bumps (Au bumps).

Claims (14)

A piezoelectric substrate integrated with a vibration region and the vibration region, and including a thick portion thicker than a thickness of the vibration region;
Excitation electrodes respectively disposed on the front and back surfaces of the vibration region;
A lead electrode extending from the excitation electrode on the thick part, and
The thick part is
So as to open a part of the vibration region,
A first thick part and a second thick part arranged across the vibration region;
A third thick portion connecting the base portions of the first thick portion and the second thick portion, and a third thick portion,
The second thick part is
An inclined portion whose thickness increases as the distance from the one edge connected to the vibration region increases toward the other edge;
A thick body continuous with the other end edge of the inclined portion,
In the second thick part,
A piezoelectric vibration element comprising a slit. The vibration area is rectangular,
The piezoelectric vibration element according to claim 1, wherein one side of the four sides of the vibration region is open. The slit is
2. The piezoelectric vibration element according to claim 1, wherein the piezoelectric vibration element is disposed in the thick main body along a boundary portion between the inclined portion and the thick main body. The slit is
The piezoelectric vibration element according to claim 1, wherein the piezoelectric vibration element is disposed in the inclined portion so as to be separated from one side of the vibration region. The slit is
A first slit disposed in the thick-walled body;
The piezoelectric vibration element according to claim 1, further comprising: a second slit disposed in the inclined portion so as to be separated from one side of the vibration region. One main surface of the vibration region;
One surface of each of the first, second and third thick parts is:
The piezoelectric vibration element according to claim 1, wherein the piezoelectric vibration element is in the same plane. The piezoelectric substrate is
Centering on the X axis of the orthogonal coordinate system consisting of the X axis as the electrical axis that is the crystal axis of the crystal, the Y axis as the mechanical axis, and the Z axis as the optical axis,
An axis obtained by inclining the Z axis by a predetermined angle in the −Y direction of the Y axis is defined as a Z ′ axis.
An axis obtained by inclining the Y axis by the predetermined angle in the + Z direction of the Z axis is a Y ′ axis,
It is composed of a plane parallel to the X axis and the Z ′ axis,
A quartz substrate having a thickness in a direction parallel to the Y ′ axis,
The side parallel to the X axis is the long side,
The piezoelectric vibration element according to claim 1, wherein the piezoelectric vibration element is a quartz substrate having a side parallel to the Z ′ axis as a short side.   The piezoelectric vibration element according to claim 7, wherein the quartz substrate is an AT-cut quartz substrate. Providing a recess including a vibration region on one surface of the front and back surfaces of the piezoelectric substrate;
Removing the piezoelectric substrate including a part of the recessed part, forming a vibration region having a thick part where a part of the recessed part is opened, and an outer shape including a slit;
Forming an electrode in a predetermined region including the front and back surfaces of the vibration region. The piezoelectric vibration element according to any one of claims 1 to 8,
And a package for accommodating the piezoelectric vibration element. The piezoelectric vibration element according to any one of claims 1 to 8,
An electronic device comprising an electronic component and a package.   The electronic device according to claim 11, wherein the electronic component is one of a variable capacitance element, a thermistor, an inductor, and a capacitor. The piezoelectric vibration element according to any one of claims 1 to 8,
An electronic device comprising: an oscillation circuit for exciting the piezoelectric vibration element; and a package.   An electronic apparatus comprising the piezoelectric vibrator according to claim 9.

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