JP5796355B2 - Piezoelectric vibration element, piezoelectric vibrator, electronic device, and electronic apparatus - Google Patents

Description

  The present invention relates to a piezoelectric vibrator that excites a thickness shear vibration mode, and more particularly, to a piezoelectric vibration element, a piezoelectric vibrator, an electronic device having a so-called inverted mesa structure, and an electronic apparatus using the piezoelectric vibrator according to the present invention.

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 crystal resonator having an inverted mesa structure in which a thick support portion is connected to each of three sides of a rectangular thin-walled vibration portion and a thick portion is provided in a U-shape. ing. 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, the thick portion is deleted along the line segment α and the line segment β as described in FIGS. 1C and 1D of Patent Document 5. However, since the deletion is based on the premise that the deletion is performed by machining such as dicing, there is a problem that the cut surface is damaged by chipping or cracks, and the ultrathin portion is damaged. 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 the above-described problem, and has achieved high frequency (100 to 500 MHz band), reduced the CI value of the main vibration, and satisfied electrical requirements such as a spurious CI value ratio. It is an object of the present invention to provide a piezoelectric vibration element, a piezoelectric vibrator, an electronic device, and an electronic apparatus using the piezoelectric vibrator of the present invention.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Embodiment 1] A piezoelectric vibration element according to the present invention includes a rectangular vibration region, a piezoelectric substrate having a support 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 each of the pair of excitation electrodes and arranged in the vibration region and the support portion in plan view. The support portion includes a first support portion and a second support portion that are disposed across the vibration region so as to open one side of the four sides of the vibration region in plan view. A first support portion and a third support portion connecting the base end portions of the second support portion, and the second support portion is connected to one side of the vibration region. A second inclined portion whose thickness increases from one edge toward the other edge; A second support portion main body connected to the other end edge of the second inclined portion, and at least disposed in the second inclined portion apart from one side of the vibration region in plan view. A piezoelectric vibration element having a single slit.
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. In addition, 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, the piezoelectric vibration element having excellent frequency temperature characteristics and CI temperature characteristics can be obtained. There is.
[Mode 2] A piezoelectric vibration element according to the present invention includes a piezoelectric substrate having a rectangular vibration region and a support portion that is integrated with the vibration region and is thicker than the thickness of the vibration region, a surface of the vibration region, and Piezoelectric vibration comprising a pair of excitation electrodes disposed on each of the back surfaces and a lead electrode extending from each of the pair of excitation electrodes and disposed in the vibration region and the support portion in plan view 1st support part and 2nd support part which are elements, Comprising: The said support part is arrange | positioned on both sides of the said vibration area | region so that one side may be open | released in four sides of the said vibration area | region in planar view And a third support part connecting between the base ends of the first support part and the second support part, and the second support part is connected to one side of the vibration region. A second inclined portion whose thickness increases from one end edge to the other end edge; A second support portion body connected to the other end edge of the second inclined portion; and a first slit disposed in the second support portion body in a plan view; and a plan view. And a second slit disposed in the second inclined portion so as to be separated from one side of the vibration region.
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. In addition, it is possible to better suppress the spread of stress that occurs when the piezoelectric vibration element is bonded and fixed, so that the piezoelectric vibration element is excellent in frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics. There is an effect that it is.
[Mode 3] In the piezoelectric vibration element, one main surface of the vibration region and one surface of each of the first support portion, the second support portion, and the third support portion are The piezoelectric vibration element according to the first or second aspect, which is the same surface.
By etching the piezoelectric substrate from only one side to form a vibration region, 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.
[Mode 4] In addition, in the piezoelectric vibration element, the piezoelectric substrate has orthogonal coordinates including an X axis as an electric axis that is a crystal axis of quartz, a Y axis as a mechanical axis, and a Z axis as an optical axis. Centering on the X axis of the 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 only in the + Z direction of the Z axis by the predetermined angle. The inclined axis is the Y ′ axis, the plane is parallel to the X axis and the Z ′ axis, the direction parallel to the Y ′ axis is the thickness, the side parallel to the X axis is the long side, 4. The piezoelectric vibration element according to claim 1, wherein the piezoelectric vibration element is a quartz crystal substrate having a side parallel to the Z ′ axis as a short side.
There is an effect that a piezoelectric vibration element having excellent temperature characteristics can be obtained.
[Mode 5] The piezoelectric vibration element according to mode 4, wherein the quartz substrate is an AT-cut quartz 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.
[Mode 6] A piezoelectric vibrator according to the present invention includes the piezoelectric vibration element according to any one of forms 1 to 5 and a package that houses the piezoelectric vibration element. It is a child.
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. The effect is 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.
[Mode 7] An electronic device according to the present invention includes the piezoelectric vibration element according to any one of claims 1 to 5, an electronic component, and a package that accommodates the piezoelectric vibration element and the electronic component. An electronic device is provided.
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 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.
[Mode 8] The electronic device according to mode 7, wherein the electronic component is any one of a variable capacitance element, a thermistor, an inductor, and a capacitor.
By configuring the piezoelectric device as described above, it is possible to configure a piezoelectric device such as a piezoelectric oscillator, a temperature-compensated piezoelectric oscillator, and a voltage-controlled piezoelectric oscillator, and a piezoelectric having excellent frequency reproducibility and aging characteristics. An oscillator, a temperature compensated piezoelectric oscillator excellent in frequency temperature characteristics, and a voltage-controlled piezoelectric oscillator having a stable frequency, a wide variable range, and a good S / N ratio (signal noise ratio) can be obtained.
[Form 9]
An electronic device includes the piezoelectric vibration element according to any one of forms 1 to 5, an oscillation circuit that excites the piezoelectric vibration element, and a package that houses the piezoelectric vibration element and the oscillation circuit. An electronic device characterized by the above.
By configuring the piezoelectric device as described above, there is an effect that a piezoelectric oscillator having excellent frequency reproducibility and aging characteristics can be obtained.
[Mode 10] An electronic device according to the present invention is an electronic device including the piezoelectric vibrator according to mode 6.
By using the piezoelectric vibrator according to the present invention 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.
Application Example 1 A piezoelectric vibration element according to the present invention includes a rectangular vibration region, a piezoelectric substrate having a support portion thicker than the vibration region integrated with the vibration region, a surface of the vibration region, and Piezoelectric vibration elements each including an excitation electrode disposed on a back surface and a lead electrode provided on each of the excitation electrodes so as to extend on the support portion, wherein the support portion includes the vibration region. Between the first support portion and the second support portion, which are opposed to each other with the vibration region interposed therebetween so as to open one side of the four sides, and the base end portions of the first and second support portions A second support portion, and the thickness of the second support portion increases as the distance from one end edge connected to one side of the vibration region increases toward the other end edge. A second support portion main body provided continuously with the second inclined portion and the other end edge of the second inclined portion , Wherein the the second support portions, a piezoelectric vibrating element, characterized in that at least one slit 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, the slit is disposed in the second support portion main body along a boundary portion between the second inclined portion and the second support portion main body. It is a piezoelectric vibration element as described in application example 1 characterized by these.

  Since the spread of stress generated when the piezoelectric vibration element is bonded and fixed can be suppressed, 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 3] In the piezoelectric vibration element according to Application Example 1, the slit is disposed in the second inclined portion so as to be separated from one side of the vibration region. It is.

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

  Application Example 4 In the piezoelectric vibration element, the slit is disposed apart from one side of the vibration region in the second inclined portion and the first slit disposed in the second support body. The piezoelectric vibration element according to Application Example 1, wherein the piezoelectric vibration element includes a second slit.

  Since it is possible to better suppress the spread of stress that occurs when the piezoelectric vibration element is bonded and fixed, the piezoelectric vibration element can be obtained with excellent frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics. effective.

  Application Example 5 In the piezoelectric vibration element, one main surface of the vibration region and one surface of each of the first, second, and third support portions are the same surface. The piezoelectric vibration element according to any one of Application Examples 1 to 4.

  By etching the piezoelectric substrate from only one side to form a vibration region, 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 6 In the piezoelectric vibration element, the piezoelectric substrate includes an X axis as an electric axis that is a crystal axis of quartz, 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 5, wherein the piezoelectric vibration element is a quartz substrate having a long side and a side parallel to the Z ′ axis as a short side.

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

  Application Example 7 The piezoelectric vibration element according to Application Example 6, wherein the quartz substrate is an AT-cut quartz 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 8 A piezoelectric vibrator according to the present invention includes the piezoelectric vibration element according to any one of Application Examples 1 to 7, and a package that accommodates the piezoelectric vibration element. A thickness shear vibration piezoelectric vibrator characterized by a vibrator.

  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. The effect is 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 9 An electronic device according to the present invention is an electronic device characterized in that the package includes the piezoelectric vibration element according to any one of claims 1 to 7 and an electronic component. It is an electronic device.

  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 10 Further, the electronic device is an electronic device characterized in that the electronic component is any one of a variable capacitance element, a thermistor, an inductor, and a capacitor.

  By configuring the piezoelectric device as described above, it is possible to configure a piezoelectric device such as a piezoelectric oscillator, a temperature-compensated piezoelectric oscillator, and a voltage-controlled piezoelectric oscillator, and a piezoelectric having 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 11]
An electronic device is an electronic device comprising a package including the piezoelectric vibration element according to any one of Application Examples 1 to 7 and an oscillation circuit that excites the piezoelectric vibration element.

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

  Application Example 12 An electronic device according to the present invention is an electronic device including the piezoelectric vibrator described in Application Example 7, and is an electronic device.

  By using the piezoelectric vibrator of the present invention in an electronic device, there is an effect that an electronic device having 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 this invention, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing. The figure explaining the relationship between an AT cut quartz substrate and a crystal axis. The top view which shows the structure of the modification of a piezoelectric vibration element. The top view which shows the structure of the modification of a piezoelectric vibration element. The 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 of the example of 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 of the example of 3rd Embodiment, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing, d) is a plan view, and (e) is a plan view of another configuration example. Explanatory drawing which shows the manufacturing process of the piezoelectric substrate of this invention. Explanatory drawing which shows the manufacturing process of the excitation electrode and lead electrode of the piezoelectric vibration element of this invention. (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. (A) (b) is sectional drawing and the top view which show the structure of the piezoelectric vibrator of embodiment which concerns on this invention. (A) of a piezoelectric vibrator is a figure which shows a frequency temperature characteristic, (b) is a figure which shows CI temperature characteristic. (A), (b) is a figure which shows the distribution characteristic of a capacity | capacitance ratio. (A), (b) is a figure which shows the distribution characteristic of an electrostatic capacitance. (A), (b) is a figure which shows the distribution characteristic of CI value ratio. (A) And (b) is a perspective view of the piezoelectric vibrator which concerns on other embodiment of this invention, (c) is a longitudinal cross-sectional view. (A) And (b) is a longitudinal cross-sectional view of the piezoelectric device which concerns on this invention, and a top view. It is characteristic explanatory drawing of the piezoelectric device which concerns on embodiment of this invention. (A) And (b) is the longitudinal cross-sectional view and top view of the piezoelectric device of this invention. The longitudinal cross-sectional view of a piezoelectric device. The longitudinal cross-sectional view of a piezoelectric device. The longitudinal cross-sectional view of a piezoelectric device. (A) (b) And (c) is a structure explanatory view of a piezoelectric substrate concerning other embodiments of the present invention. (A) (b) And (c) is a structure explanatory view of a piezoelectric substrate concerning other embodiments of the present invention. (A) And (b) is a principal part top view which shows the structural example of a mount part, and sectional drawing. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a configuration of a piezoelectric vibration element 1 according to an 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. External perspective view, (f) is an OO cross-sectional view.
The piezoelectric vibration element 1 has a thin vibration region 12 and a piezoelectric substrate 10 having thick support portions 14, 16, 18 connected to the vibration region 12, and both main surfaces of the vibration region 12 are opposed to each other. Excitation electrodes 25a and 25b formed as described above, and lead electrodes 27a and 27b formed by extending from the excitation electrodes 25a and 25b toward the pad electrodes 29a and 29b provided in the thick portions, It has.

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

The third support portion 18 is connected to one side 12c of the thin flat plate-like vibration region 12, and gradually increases in thickness as it is separated from one end edge connected to the one side 12c of the vibration region 12 toward the other end edge. And a third support portion body 16a having a thick quadrangular prism shape connected to the other end edge of the third inclined portion 18b. 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 support portions 14, 16, and 18 and is open on the other side.
Note that one main surface of the vibration region 12 and one surface of each of the first, second, and third support portions 14, 16, and 18 are on the same plane, that is, the X-axis of the coordinate axis shown in FIG. It is on the Z ′ plane, and this surface (the lower surface side in FIG. 1B) is called a flat surface, and the opposite surface (the upper surface side in FIG. 1B) is called a concave surface.
Further, in the piezoelectric substrate 10, at least one stress relaxation slit is formed through the second support portion 16. In the embodiment shown in FIG. 1, the slit 20 is formed in the surface of the second support portion main body 16a along the connecting portion between the second inclined portion 16b and the second support portion main body 16a.

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 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 (the back surface side in FIG. 1B) is sufficiently larger than the size of the excitation electrode 25a on the concave surface side (the upper surface side in FIG. 1B). Set larger. 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 27a arranged so as to extend from the excitation electrode 25a so as to pass through the third inclined portion 18b and the third support body 18a from above the vibration region 12. Thus, the pad electrode 29a formed on the upper surface of the second support body 16a is conductively connected. The excitation electrode 25b formed on the flat surface side is electrically connected to the pad electrode 29b formed on the back surface (lower surface) of the second support body 16a by the lead electrode 27b passing through the edge portion of the piezoelectric substrate 10. It is connected.

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 support portion. 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 shown in FIG. 1, the pad electrodes 29 a and 29 b are formed on the front and back (upper and lower) surfaces of the piezoelectric substrate 10. However, when the piezoelectric vibrating element 1 is accommodated in the package, FIG. As shown in the figure below, the piezoelectric vibration element 1 is turned over, the pad electrode 29a and the terminal electrode A of the package are mechanically fixed and electrically connected with a conductive adhesive, and the pad electrode 29b and the terminal electrode B of the package are connected to each other. May be 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.
Further, as shown in the figure below, an oscillation circuit for driving the piezoelectric vibration element 1, for example, an IC chip, is mounted inside the package, and the electrode pads and the terminal electrodes A electrically connected to the IC chip. Alternatively, the piezoelectric oscillator may be configured by being electrically connected to B and B. 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.
Further, the pad electrodes 29a and 29b may be arranged on the back surface side of the piezoelectric substrate 10 with a space therebetween. As shown in the figure below, when conductive connection is used between the pad electrodes 29a and 29b and the terminal electrode of the package housing the piezoelectric vibration element 1, the pad electrodes 29a and 29b are connected to the back surface of the piezoelectric substrate. It is desirable to have a configuration in which they are juxtaposed on the side.

The reason why the slit 20 is provided between the vibration region 12 and the pad electrodes 29a and 29b that are the support 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 is supported on the package by the conductive adhesive, first, the conductive adhesive is applied to the supported portion (pad electrode) 29a of the second support portion main body 16a, and this is applied to the package or the like. Place it on the terminal electrode and hold it down a little. 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 support part main body 16a and the package expand, and the adhesive also softens temporarily. Therefore, no stress is generated in the second support part main body 16a. After the conductive adhesive is cured, when the second support body 16a and the package are cooled and the temperature returns to room temperature (25 ° C.), the conductive adhesive, the package, and the second support body 16a. Due to the difference from the respective linear expansion coefficients, the stress generated from the cured electroconductive adhesive spreads from the second support portion body 16a to the first and third support portions 14 and 18 and the vibration region 12. 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 silicon-based, epoxy-based, polyimide-based, and bismaleimide-based adhesives. 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. As is well known, the frequency when force is applied to both ends along the X-axis direction of the AT-cut quartz substrate is known. Comparing the circumferential change with the frequency circumferential 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.

  FIG. 3 is a modification of the piezoelectric vibration element 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 embodiment shown in FIG. 3, the third support portion 18 of the thin vibration region 12 The difference is that the corners corresponding to both ends of the corresponding side 12c are chamfered. As described above, the piezoelectric substrate 10 having a structure in which the corners of the vibration region 12 are chamfered as shown in FIG. It shall be included in the concept of a substantially square.

1 and 3, the excitation electrodes 25a and 25b have a quadrilateral shape, that is, a square shape or a rectangular shape (with the long side in the X-axis direction). However, the present invention is not limited to this. . In the embodiment shown in FIG. 4, 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 embodiment shown in FIG. 5, the excitation electrode 25a on the concave surface side (front surface side) is elliptical, and the excitation electrode 25b on the flat surface side (back surface side) is a quadrangle sufficiently larger than the excitation electrode 25a. The displacement distribution in the X-axis direction differs from the displacement in the Z′-axis direction due to the anisotropy of the elastic constant, and a 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.

FIG. 6 is a schematic diagram illustrating a configuration of the piezoelectric vibration element 2 according to the second embodiment. 6A is a plan view of the piezoelectric vibration element 2, FIG. 6B is a cross-sectional view taken along the line PP, and FIG. 6C 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 second inclined portion 16b that is separated from the edge of the one side 12b of the thin vibration region 12. Rather than forming the slit 20 in the second inclined portion 16b so that one edge of the slit 20 is in contact with the one side 12b along one side 12b of the vibration region 12, both end edges of the second inclined portion 16b are formed. The slit 20 is provided further apart. That is, in the second 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 disposed in the vibration region 12, the inharmonic mode (A0, S1, A1, S2,...) In addition to the main vibration (S0). Is excited. Desirably, only the main vibration (S0) mode is set as the confinement mode, and the other inharmonic mode is set as the propagation mode (non-confinement mode). However, the vibration region 12 becomes thin, and the fundamental frequency thereof 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. 6 is asymmetric, and the shape of both end edges in the X-axis direction is also asymmetric by leaving the strip 16bb, and the low-order inharmonic mode. We realized that the amplitude of the standing wave was suppressed.

FIG. 7 is a schematic diagram illustrating a configuration of the piezoelectric vibration element 3 according to the third embodiment. 7A is a plan view of the piezoelectric vibration element 3, FIG. 7B is a cross-sectional view taken along the line PP, FIG. 7C is a cross-sectional view taken along the line Q-Q, and FIG. It is a top view.
The piezoelectric vibration element 3 is different from the piezoelectric vibration element 1 shown in FIG. 1 in that a first slit 20a is provided in the surface of the second support portion main body 16a, and a second slit portion 16b is provided in the surface of the second inclined portion 16b. The second slit 20b is formed, and two slits for stress relaxation are provided. The purpose of forming the individual slits in the surface of the second support portion main body 16a and in the surface of the second inclined portion 16b has already been described as described above, and will be omitted here.
The first slit 20a and the second slit 20b are not juxtaposed in the X-axis direction as shown in the plan view of FIG. 7A, but in the Z′-axis direction as shown in FIG. 7D. You may arrange | position in steps so that it may leave | separate. 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.

FIG. 8 and FIG. 9 are flowcharts showing manufacturing steps 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 (referred to as a resist film) R is applied on the entire surface of the front and back metal films M, respectively. In step S3, the resist film R at a position corresponding to the recessed portion 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 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 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. 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. 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. A feature of the present invention is that, as shown in steps S8 and S9, a part of the vibration region 12 of the recessed portion 11 and the fourth support portion 19 connected to the vibration region 12 are removed by etching. 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. The 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.

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.

10 and 11 are diagrams for explaining the cross-sectional shape of the recessed portion 11 on the AT-cut quartz crystal wafer 10W formed by etching.
FIG. 10A is a plan view of the quartz 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. 10B 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. 10C to 10E 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. 10D, the wall surface in the + X axis direction is orthogonal (90 degrees) to the plane of the quartz wafer 10W and etching proceeds slightly, but thereafter, 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. 10E 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. 11 is a view for explaining the wall surface of the recessed portion 11 formed in the piezoelectric substrate 10, particularly a sectional view in the Z′-axis direction. FIG. 11A is a plan view of the quartz wafer 10W. FIG. 11B 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. 11C to 11E 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. 11D, 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. 11E is a cross-sectional view of a groove portion formed orthogonal to the Z′-axis direction, which is a wedge-shaped cross-section Z3. This groove is a groove for folding the quartz 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. 11 (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 11 is This is because the piezoelectric substrate is miniaturized by removing it together with the support portion 19 by etching.
Furthermore, since the manufacturing method has been established on the assumption that the gently inclined surface Z2c is deleted together with the fourth support portion 19, the area of the flat ultrathin portion that becomes the vibration region is listed as the prior art. Compared to the conventional structure with thick portions existing at both ends of the vibration region along the X axis, it has been ensured that the elastic constant is different in the thickness-shear vibration mode excited in the vibration region. Since 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 orientation, the ratio of the major axis to the minor axis is 1.26: 1. Although desirable, it has become possible to design sufficiently so as to be in the range of 1.14 to 1.39: 1 in consideration of variations in manufacturing dimensions and the like.
Further, as shown in FIG. 17, in the outer shape of the piezoelectric vibration element 1, an inclined surface appears on the end surface intersecting 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.
Further, in the vicinity of the inclined surfaces (1) and (2) intersecting with the main surface of the piezoelectric substrate, a wall surface perpendicular to the wall surface X2 formed in the + X axis direction as shown in FIGS. 10 (b) and 10 (e). Has not appeared. This is because, 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) from the front and back surfaces. Since the etching is performed until the film penetrates, the etching time is sufficiently long, so that the vertical wall surface does not appear due to the over-etching action.
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, the inclination angle α of the inclined surfaces a1 and a2 with respect to the X axis is larger than the inclination angle β of the inclined surfaces b1 and a4 with respect to the X axis.
β <α
It was found that there is a relationship.

12A and 12B are cross-sectional views showing the configuration of the piezoelectric vibrator 5 according to the embodiment of the present invention. 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. 13, 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 support body 14a 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 then the pad electrode 29a of the piezoelectric vibration element 1 and the package. The terminal electrode A (pad 47) is placed with one point of support, is loaded and fixed mechanically and is electrically connected. As a characteristic of the conductive adhesive 30, the magnitude of stress (strain) caused by the adhesive 30 increases in the order of a silicon-based adhesive, an epoxy-based adhesive, and a polyimide-based adhesive. In addition, degassing increases in the order of polyimide adhesive, epoxy adhesive, and silicon adhesive.
The pad electrode 29b and the terminal electrode B of the package may be 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.

In order to cure the conductive adhesive 30 of the piezoelectric vibrator 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 above-described embodiment of the piezoelectric vibrator 5, an example in which a laminated plate is used for the package body 40 has been described. However, a single-layer ceramic plate is used for the package body 40, and a cap that is drawn on the lid is used. A piezoelectric vibrator may be configured.

  FIGS. 13A and 13B are diagrams showing an example of electrical characteristics of the piezoelectric vibrator 5 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). 13A shows the frequency temperature characteristics of the piezoelectric vibrator 5 in the temperature range of −40 ° C. to 85 ° C., and FIG. 13B shows the CI (crystal impedance) temperature characteristics of the piezoelectric vibrator 5 in the same temperature range. . The frequency-temperature characteristic shown in FIG. 13A exhibits a smooth cubic curve and satisfies the required standard. Further, the CI temperature characteristic of FIG. 13B also exhibits good characteristics without CI dip over the entire temperature range.

FIG. 14A shows the distribution of the capacity ratio γ of the piezoelectric vibrator 5 of the present invention, and an average value of 273 and a standard deviation σ of 18 were obtained. FIG. 14B 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. 15A shows the distribution of the electrostatic capacitance C0 of the piezoelectric vibrator 5 of the present invention. The average value of C0 is 1.80 (pF), and the standard deviation σ is 0.01. FIG. 15B represents the distribution of the capacitance C0 of the conventional piezoelectric vibrator, and the average value of C0 is 1.88 and the standard deviation σ is 0.02.
FIG. 16A shows the distribution of the spurious CI value ratio (= CIs / CIm, CIm is the CI value of the main vibration, and CIs is the CI value of the largest spurious close to the main vibration) of the piezoelectric vibrator 5 of the present invention. FIG. 16B shows a distribution of spurious CI value ratios of the conventional piezoelectric vibrator.
As is apparent from FIGS. 14, 15 and 16, the capacitance ratio γ, the capacitance C0, and the spurious CI value ratio are both higher in the piezoelectric vibrator 5 according to the present invention than in the conventional piezoelectric vibrator. I found it excellent. Moreover, the piezoelectric vibrator 5 according to the present invention is 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. Moreover, as shown in FIG. 4, when the slit 20 is formed in the 2nd inclination part 14b, there exists an effect that a slit can penetrate easily.

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. 13, the high-frequency fundamental piezoelectric vibrator can be miniaturized and the stress caused by adhesion / fixation can be suppressed, so that frequency reproducibility, frequency temperature characteristics, There is an effect that a piezoelectric vibrator excellent in 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.

本発明に係る４９１（ＭＨｚ）の圧電振動子を用いてＶＣＸＯを製作した。図１８は、そのＶＣＸＯの周波数温度特性の評価結果である。滑らかな三次曲線を呈しており、要求された規格を満たしており、全温度範囲に亘ってディップ等もなく良好な特性が得られている。 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. 18 shows the evaluation results of the 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.

FIG. 20 is a cross-sectional view showing a configuration of a piezoelectric oscillator 6 which is a kind of electronic device according to an embodiment of the present invention. The piezoelectric oscillator 6 includes a package main body 40 and a lid member 49, a piezoelectric vibration element 1, an IC component 51 on which an oscillation circuit for exciting the piezoelectric vibration element 1 is mounted, a variable capacitance element whose capacitance changes according to voltage, and resistance from temperature. And a thermistor and an electronic component 52 such as 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 on the conductive adhesive (polyimide system) 30 so as to be electrically connected to the pad electrode 29a. The other pad electrode 29 b is connected to the other terminal pad of the package body 40 with a bonding wire, 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. 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.

In the piezoelectric oscillator 6 shown in the embodiment of FIG. 20, the piezoelectric vibration element 1, the IC component 51, and the electronic component are arranged on the same piezoelectric substrate. However, the piezoelectric oscillator 7 of the embodiment of FIG. The piezoelectric vibration element 1 is accommodated in the upper portion, the inside of the cavity is filled with vacuum or nitrogen N 2 gas, and sealed with the lid member 49. In FIG. 21, an IC component 51 on which an oscillation circuit and an amplifier circuit for exciting the piezoelectric vibration element 1 are mounted, a variable capacitance element, and an electronic component 52 such as an inductor, a thermistor, and a capacitor as necessary. Are connected and connected to the terminal 67 of the package main 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, in FIG. 22, the lower storage portion may include at least one electronic component. For example, a thermistor, a capacitor, a reactance element, or the like can be applied as the electronic component, and an electronic device using a piezoelectric vibration element as a frequency oscillation source can be constructed.

As shown in FIGS. 20, 21, and 22, by configuring a piezoelectric device (for example, a voltage-controlled piezoelectric oscillator), frequency reproducibility, frequency temperature characteristics, and aging characteristics are excellent, and it is small and has a high frequency (for example, a 490 MHz band). ) Is 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. 24 shows a configuration example in which an inclined surface is formed on the outer peripheral side surface of the thick support portion of the piezoelectric substrate.

[Modified Embodiment]
The piezoelectric substrate 10 in the embodiment of FIG. 24A is a piezoelectric substrate 10 provided with a thin part having a vibration region 12 and a thick part provided at the periphery of the thin part and thicker than the thin part. In the piezoelectric substrate, the mount portion M is connected to the thick support portion 13 side by side through the buffer portion S in the direction of the edge, and the buffer portion is a slit between the mount portion and the thick support portion. 20, and the mount portion has chamfered portions 21 at both ends in a direction orthogonal to the direction in which the mount portion, the buffer portion, and the thick support portion are arranged.
The piezoelectric substrate 10 in FIG. 24B is a piezoelectric substrate 10 including a thin portion having a vibration region 12 and a thick support portion 13 provided at the periphery of the thin portion and thicker than the thin portion. Mount portions M are connected to the meat support portion side by side through a buffer portion S. The buffer portion has a slit 20 between the mount portion and the thick wall support portion. Notches 22 at both ends in a direction orthogonal to the direction in which the portion and the thick support portion are arranged, the longitudinal direction of the slit is parallel to the orthogonal direction, and the width of the mount portion in the orthogonal direction is set to It is narrower than the width in the longitudinal direction, and both end portions in the longitudinal direction of the slit are closer to the outer periphery in the orthogonal direction of the buffer portion than both end portions of the mount portion.
The piezoelectric substrate of FIG. 24C is a piezoelectric substrate 10 that includes a thin portion having a vibration region 12 and a thick support portion 13 provided at the periphery of the thin portion. The buffer portion S and the mount portion M are connected in order, and the buffer portion has a slit 20 between the mount portion and the thick wall support portion, and the mount portion includes the mount portion, the buffer portion, and the thick wall support portion. It is characterized by having notches 22 at both ends in a direction perpendicular to the direction of alignment.

FIG. 25 is characterized in that it takes the form of two-point support with respect to the structure of FIG.
In FIGS. 24 and 25, inclined portions are not shown on the inner walls of the support portions 14, 16, and 18 of the thick support portion 13, and the outer side wall surface of the thick support portion 13 is not illustrated. Although the inclined surface as shown in FIG. 13 is not shown, these inclined portions and inclined surfaces are formed in corresponding portions.
In addition, each code | symbol in FIG. 24, FIG. 25 respond | corresponds with the site | part which the same code | symbol of said each embodiment shows.

[Modified Example 2]
Further, the embodiment of FIGS. 26A and 26B shows the configuration of the mount portion. In this mount portion M, an area is gained by making it uneven to improve the adhesive strength.
FIG. 27 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 6 described above. An example of the electronic device 8 using the piezoelectric vibrator 6 is a transmission device. In these electronic devices 8, the piezoelectric vibrator 6 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.
By using the piezoelectric vibrator of the present invention for an electronic device, there is an effect that an electronic device having a reference frequency source having a high frequency and excellent frequency stability and a good S / N ratio can be configured.

DESCRIPTION OF SYMBOLS 1, 2, 3 ... Piezoelectric vibration element, 6, 7 ... Piezoelectric device, 8 ... Electronic device, 10 ... Piezoelectric substrate, 10W ... Quartz wafer, 11 ... Recessed part, 12 ... Vibration area, 12a, 12b, 12c ... Vibration area One side, 13 ... thick support part, 14 ... first support part, 14a ... first support part body, 14b ... first inclined part, 16 ... second support part, 16a ... second support part Main body, 16bb ... strip, 16b ... second inclined part, 18 ... third support part, 18a ... third support part main body, 18b ... third inclined part, 19 ... fourth support 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 43 ... third substrate Plate 44 ... Seal ring 45 ... Mounting terminal 46 ... Conductor 47 ... Element mounting pad 49 ... Lid member 51 ... IC component 52 Electronic component 60 ... Package body 61 ... Lid member 65 ... Mounting terminal , 66 ... Conductor, 67 ... Component terminal, 68 ... Metal bump (Au bump)

Claims (10)

Rectangular vibration region, and a thick support part than the thickness of the vibration region integrated with the vibration area, a piezoelectric substrate having,
A pair of excitation electrodes disposed on the front and back surfaces of each of the vibration area s,
Extending from each of the pair of excitation electrodes, lead electrodes in plan view, are arranged in the vibrating region and the supporting part,
A piezoelectric vibration element comprising:
The support portion, in plan view, the I you open one side of the four sides of the vibration region urchin, a first support portion及 beauty second supporting portion that is placed across the front Symbol vibration region a third support portion which connects the proximal end portion of the first supporting portion and the second supporting portion,
With
The second support part is
A second inclined portion which thickness increases brought from said one end edge which is provided continuously to one side of the vibration region will suited to the other end edge,
A second support portion main body connected to the other end edge of the second inclined portion ;
In plan view, the piezoelectric vibrating element, comprising and at least one slit being spaced from one side of the vibration region to the second inclined portion.   A piezoelectric substrate having a rectangular vibration region, and a support portion that is thicker than the thickness of the vibration region integrated with the vibration region;
  A pair of excitation electrodes disposed on each of the front and back surfaces of the vibration region;
  A lead electrode extending from each of the pair of excitation electrodes and arranged in the vibration region and the support portion in plan view;
A piezoelectric vibration element comprising:
  The support portion includes a first support portion and a second support portion that are disposed across the vibration region so as to open one side of the four sides of the vibration region in plan view, and the first support portion. A third support portion connecting between the support portion and the base end portion of the second support portion;
With
  The second support part is
  A second inclined portion whose thickness increases from one edge connected to one side of the vibration region toward the other edge;
  A second support portion main body connected to the other end edge of the second inclined portion;
  A first slit disposed in the second support body in plan view;
  And a second slit disposed in the second inclined portion so as to be separated from one side of the vibration region in plan view. One main surface of the vibration region;
Said first support part, the second supporting portion, and a third respective one surface of the support part,
The piezoelectric vibrating element according to claim 1 or 2, wherein the at least one surface. 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,
Wherein Y 'and a thickness of a direction parallel to the axis, the parallel sides before Symbol X-axis and the long side, before Symbol Z', characterized in that a quartz substrate was short sides sides parallel to the axis The piezoelectric vibration element as described in any one of Claims 1 thru | or 3 . The piezoelectric vibration element according to claim 4 , wherein the quartz substrate is an AT-cut quartz substrate. The piezoelectric vibration element according to any one of claims 1 to 5 ,
A package housing the piezoelectric vibrating element,
A piezoelectric vibrator characterized by comprising: The piezoelectric vibration element according to any one of claims 1 to 5 ,
Electronic components,
An electronic device is characterized in that and a package that accommodates the piezoelectric vibrating element and the electronic component. The electronic device according to claim 7, wherein the electronic component is any 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 5 ,
An oscillation circuit for exciting the piezoelectric vibrating element,
An electronic device is characterized in that and a package that accommodates the piezoelectric vibrating element and the oscillating circuit. An electronic apparatus comprising the piezoelectric vibrator according to claim 6 .

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