Piezoelectric vibrator, piezoelectric vibrator, and oscillator

Abstract

The present invention provides a piezoelectric vibrating piece that can suppress the occurrence of a short circuit between excitation electrodes in the groin area between a pair of vibrating arms. [Solution] The piezoelectric vibrating piece 3 comprises a piezoelectric plate 30 having a pair of vibrating arms 31 and 32 extending from a base 35 in the same direction, and a first excitation electrode 41 and a second excitation electrode 42 provided on each of the pair of vibrating arms 31 and 32 to generate an electric field on each of the pair of vibrating arms 31 and 32. The front surface 35a of the base 35 is located between the pair of vibrating arms 31 and 32 and has a crotch 50 on which the first excitation electrode 41 and the second excitation electrode 42 are provided. The crotch 50 has a residue region 51 defined as the area where etching residue 55 is formed when viewed from the thickness direction of the piezoelectric plate 30, and a non-residue region 52 defined as the area where etching residue 55 is not formed when viewed from the thickness direction of the piezoelectric plate 30. The front surface 35a of the base 35 is inclined with respect to the thickness direction of the piezoelectric plate 30 in the non-residue region 52.

Description

Technical Field

[0001] The present invention relates to a piezoelectric vibrating piece, a piezoelectric vibrator, and an oscillator.

Background Art

[0002] For example, in electronic devices such as mobile phones and portable information terminal devices, a piezoelectric vibrator using quartz or the like is used as a device used for a timing source such as a time source or a control signal, a reference signal source, or the like. As this type of piezoelectric vibrator, a piezoelectric vibrating piece including a piezoelectric plate formed of a piezoelectric material such as quartz, and two systems of excitation electrodes disposed on the outer surface of the piezoelectric plate and applying a driving voltage for excitation to the piezoelectric plate, is known to be hermetically sealed in a package in which a cavity is formed.

[0003] Some piezoelectric vibrating pieces include a piezoelectric plate having a pair of vibrating arms arranged side by side and a base portion connecting the base ends of the pair of vibrating arms. In such a piezoelectric vibrating piece, two systems of excitation electrodes are disposed on the outer surface of the vibrating arms, and when a driving voltage is applied between the two systems of excitation electrodes, each vibrating arm vibrates at a predetermined resonance frequency in a direction approaching and separating from each other starting from the connecting portion with the base portion.

[0004] An example of a method for manufacturing a piezoelectric vibrating piece is as follows. A mask having a shape corresponding to the outer shape of the piezoelectric vibrating piece is formed on both surfaces of a wafer made of a piezoelectric material such as quartz, and the piezoelectric plate is obtained by subjecting the wafer to wet etching. A metal film is formed on the outer surface of the piezoelectric plate, and excitation electrodes and the like are formed by shaping the metal film by photolithography.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, one of the two excitation electrodes is positioned on the side of one vibrating arm, and the other is positioned on the side of the other vibrating arm. Therefore, when forming the excitation electrodes, it is necessary to reliably divide the metal film into two excitation electrodes at the groin between the pair of vibrating arms in order to suppress short circuits between the excitation electrodes. However, when a wafer made of piezoelectric material such as quartz is wet-etched, irregular shapes consisting of the natural crystal surface of the piezoelectric material may be formed as etching residue at the groin between the pair of vibrating arms. If etching residue is formed at the groin, when forming the metal film by photolithography, for example, the etching residue may cast a shadow, causing exposure failure, and it may not be possible to reliably divide it into two excitation electrodes.

[0007] Furthermore, in the case of a small piezoelectric vibrator, it is difficult to create a recess on the side of the base at the groin, as in the configuration described in Patent Document 1, in order to secure space for routing the electrode film on the main surface of the base.

[0008] Therefore, the present invention provides a piezoelectric vibrating piece that can suppress the occurrence of a short circuit between excitation electrodes in the groin area between a pair of vibrating arms, and a piezoelectric vibrator and oscillator equipped with the piezoelectric vibrating piece. [Means for solving the problem]

[0009] A piezoelectric vibrating piece according to a first aspect of the present invention comprises a piezoelectric plate having a base and a pair of vibrating arms extending from the base in the same direction, and a first excitation electrode and a second excitation electrode provided on each of the pair of vibrating arms to generate an electric field on each of the pair of vibrating arms, wherein the side surface of the base has a groin portion located between the pair of vibrating arms and on which the first excitation electrode and the second excitation electrode are provided, the groin portion has a residue region defined as the range in which etching residue is formed when viewed from the thickness direction of the piezoelectric plate and a non-residue region defined as the range in which the etching residue is not formed when viewed from the thickness direction, and the side surface of the base is inclined with respect to the thickness direction in the non-residue region.

[0010] According to the first embodiment, the non-residue region of the groin area is a region in which the light irradiated in the thickness direction of the piezoelectric plate during the exposure process is not obstructed by etching residue when forming the first and second excitation electrodes by photolithography of the metal film. Therefore, exposure defects caused by etching residue can be suppressed. Furthermore, if the side surface of the base is substantially parallel to the thickness direction of the piezoelectric plate, the resist film on the side surface of the base may not be exposed during the exposure process, regardless of the presence or absence of etching residue. According to the first embodiment, since the side surface of the base is inclined with respect to the thickness direction of the piezoelectric plate, the light irradiated in the thickness direction of the piezoelectric plate during the exposure process can be applied to the entire non-residue region. This makes it possible to reliably expose the resist film on the non-residue region during the exposure process, and a gap between the first and second excitation electrodes can be formed in the non-residue region, thereby reliably separating and insulating the first and second excitation electrodes. Therefore, it is possible to suppress the occurrence of a short circuit between the excitation electrodes in the groin area between the pair of vibrating arms.

[0011] A piezoelectric vibrator according to a second aspect of the present invention is a piezoelectric vibrator according to the first aspect described above, wherein the piezoelectric plate is formed from a quartz substrate, and the side surface of the base is parallel to the optical axis, which is the crystal axis of the quartz, in the non-residue region.

[0012] According to the second embodiment, since the quartz substrate has the characteristic of forming crystal planes parallel to the optical axis by isotropic etching, the non-residue region on the side of the base can be tilted with respect to the thickness direction without additional processing.

[0013] A piezoelectric vibrator according to a third aspect of the present invention is a piezoelectric vibrator according to the second aspect described above, wherein the piezoelectric plate is formed from a quartz substrate, and the thickness direction may be inclined in a range of 1° to 18° with respect to the optical axis, which is the crystal axis of the quartz.

[0014] According to the third embodiment, by setting the inclination angle of the piezoelectric plate in the thickness direction with respect to the optical axis to 1° or more, the non-residue region on the side of the base can be more easily exposed to light during the exposure process. Furthermore, it was found that setting the inclination angle to 18° or less results in an oscillation efficiency of 0.95 or more. If the oscillation efficiency falls below 0.95, the Q value decreases and the characteristics of the piezoelectric vibrator deteriorate. Therefore, by setting the inclination angle to 18° or less, the decrease in the efficiency of bending vibration can be suppressed.

[0015] In the piezoelectric vibrating piece according to the fourth aspect of the present invention, the thickness direction may be inclined in a range of 5° to 9° with respect to the optical axis of the crystal, as described above in the piezoelectric vibrating piece according to the third aspect.

[0016] According to the fourth embodiment, by setting the inclination angle of the piezoelectric plate in the thickness direction with respect to the optical axis to 5° or more and 9° or less, the peak temperature of the frequency-temperature characteristic curve of the piezoelectric vibrator can be set to 20° or more and 30° or less. Assuming a room temperature of 25°C as the actual operating temperature range, setting the peak temperature to 20° or more and 30° or less makes the frequency variation range of the piezoelectric vibrator acceptable. Therefore, a piezoelectric vibrator with excellent temperature characteristics can be obtained.

[0017] In the piezoelectric vibrating piece according to the fifth aspect of the present invention, the first excitation electrode and the second excitation electrode may not be arranged in the non-residue region, in the piezoelectric vibrating piece according to any of the first to fourth aspects described above.

[0018] According to the fifth embodiment, since sufficient space is provided between the first excitation electrode and the second excitation electrode, short circuits between the excitation electrodes can be suppressed more reliably.

[0019] A piezoelectric vibrating piece according to a sixth aspect of the present invention is a piezoelectric vibrating piece according to any of the first to fourth aspects described above, wherein the first excitation electrode and the second excitation electrode are arranged in the non-residue region and are separated from each other in the non-residue region.

[0020] According to the sixth aspect, since the range irradiated with light in the exposure process is limited within the non-residue region on the side surface of the base portion, it is possible to suppress the resist film on the side surface of the vibrating arm from being unintentionally exposed to light. Thereby, the excitation electrodes on the side surface of the vibrating arm can be surely formed into a desired shape, and an increase in the CI (Crystal Impedance) value of the piezoelectric vibrating piece can be suppressed.

[0021] The piezoelectric vibrating piece according to the seventh aspect of the present invention is the piezoelectric vibrating piece according to any one of the first aspect to the fourth aspect, wherein one of the first excitation electrode and the second excitation electrode is not arranged in the non-residue region, and the other of the first excitation electrode and the second excitation electrode may be arranged in the non-residue region.

[0022] According to the seventh aspect, since a sufficient space is provided between the first excitation electrode and the second excitation electrode as compared with the configuration in which the first excitation electrode and the second excitation electrode are arranged in the non-residue region, it is possible to more surely suppress the occurrence of a short circuit between the excitation electrodes. Further, as compared with the configuration in which the first excitation electrode and the second excitation electrode are not arranged in the non-residue region, the range irradiated with light in the exposure process becomes narrower on the side surface of the base portion, so that it is possible to suppress the resist film on the side surface of the vibrating arm from being unintentionally exposed to light. Thereby, the excitation electrodes on the side surface of the vibrating arm can be surely formed into a desired shape, and an increase in the CI (Crystal Impedance) value of the piezoelectric vibrating piece can be suppressed.

[0023] The piezoelectric vibrating piece according to the eighth aspect of the present invention is the piezoelectric vibrating piece according to any one of the first aspect to the seventh aspect, wherein in the direction in which the pair of vibrating arms are arranged, the dimension of the leg portion with respect to the dimension of the residue region may be 1.1 or more.

[0024] According to the eighth aspect, a large non-residue region can be secured in the direction in which the pair of vibrating arms are arranged. Therefore, when forming the metal film by photolithography, the first excitation electrode and the second excitation electrode can be more surely divided.

[0025] The piezoelectric vibrating piece according to the ninth aspect of the present invention is the piezoelectric vibrating piece according to any one of the first to eighth aspects, wherein the piezoelectric plate may further include a pair of support arms extending from the base portion to the outside of the pair of vibrating arms so as to sandwich the pair of vibrating arms therebetween.

[0026] The piezoelectric vibrator according to the tenth aspect of the present invention includes the piezoelectric vibrating piece according to any one of the first to ninth aspects and a package for hermetically sealing the piezoelectric vibrating piece.

[0027] According to the tenth aspect, a piezoelectric vibrator with good quality can be obtained.

[0028] The oscillator according to the eleventh aspect of the present invention includes the piezoelectric vibrator according to the tenth aspect, and the piezoelectric vibrator is electrically connected to an integrated circuit as an oscillator.

[0029] According to the eleventh aspect, an oscillator with good quality can be obtained.

Effect of the Invention

[0030] According to the present invention, it is possible to suppress the occurrence of a short circuit between excitation electrodes in the crotch portion between the pair of vibrating arms.

Brief Description of the Drawings

[0031] [Figure 1] It is a diagram showing an oscillator according to an embodiment. [Figure 2] It is an external perspective view of a piezoelectric vibrator according to an embodiment. [Figure 3] It is a plan view of a piezoelectric vibrator showing a state where a sealing plate is removed. [Figure 4] It is a cross-sectional view corresponding to the IV-IV line in FIG. 3. [Figure 5] It is a perspective view of a piezoelectric vibrating piece according to an embodiment. [Figure 6] It is a plan view of a piezoelectric vibrating piece according to an embodiment. [Figure 7] It is an enlarged view showing a VII portion in FIG. 6. [Figure 8] This is a cross-sectional view along the line VIII-VIII in Figure 7. [Figure 9] This graph shows the relationship between the cut angle of the piezoelectric plate and the oscillation efficiency of the piezoelectric vibrator. [Figure 10] This graph shows the relationship between the cut angle of a piezoelectric plate and its apex temperature. [Figure 11] This is an enlarged plan view of a piezoelectric vibrator according to a first modified embodiment, and corresponds to Figure 7. [Figure 12] This is an enlarged plan view of a piezoelectric vibrator according to a second modified embodiment, and corresponds to Figure 7. [Modes for carrying out the invention]

[0032] Embodiments of the present invention will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplication of these components may be omitted.

[0033] (Oscillator of the embodiment) Figure 1 shows an oscillator according to an embodiment of this design. As shown in Figure 1, the oscillator 100 comprises a substrate 101, an electronic component 102, an integrated circuit 103, and a piezoelectric resonator 1. The electronic component 102 is, for example, a capacitor and is mounted on the substrate 101. The integrated circuit 103 is for the oscillator and is mounted on the substrate 101. The integrated circuit 103 is electrically connected to the piezoelectric resonator 1 and the electronic component 102, respectively, via wiring not shown. The piezoelectric resonator 1 is mounted, for example, on the substrate 101 near the integrated circuit 103. The piezoelectric resonator 1 functions as an oscillator. The piezoelectric resonator 1 will be described later. At least a part of the oscillator 100 may be molded with a resin not shown, as appropriate.

[0034] When power is supplied to the piezoelectric vibrator 1, the piezoelectric vibrator 3 (see Figure 5) of the piezoelectric vibrator 1 vibrates. The vibration of the piezoelectric vibrator 3 is converted into an electrical signal due to the piezoelectric properties of the piezoelectric vibrator 3. This electrical signal is output from the piezoelectric vibrator 1 to the integrated circuit 103. The integrated circuit 103 generates a frequency signal by performing various processes on the electrical signal output from the piezoelectric vibrator 1.

[0035] The oscillator 100 can be applied to, for example, a single-function oscillator for a clock, a timing control device that controls the operating timing of various devices such as computers, or a device that provides time or a calendar. The integrated circuit 103 is configured according to the functions required of the oscillator 100 and may include a so-called RTC (real-time clock) module.

[0036] (Piezoelectric vibrator of the embodiment) Figure 2 is an external perspective view of a piezoelectric vibrator according to an embodiment. Figure 3 is a plan view of the piezoelectric vibrator with the sealing plate removed. Figure 4 is a cross-sectional view corresponding to the line IV-IV in Figure 3. As shown in Figures 2 to 4, the piezoelectric resonator 1 is a surface-mount type resonator of the so-called ceramic package type. The piezoelectric resonator 1 comprises a package 2 having an internally hermetically sealed cavity C, and a piezoelectric vibrating element 3 housed within the cavity C. The piezoelectric resonator 1 has a rectangular parallelepiped shape. In this embodiment, in a plan view, the longitudinal direction of the piezoelectric resonator 1 is called the longitudinal direction L, the short direction is called the width direction W, and the direction perpendicular to these longitudinal direction L and width direction W is called the thickness direction T.

[0037] Package 2 comprises a package body 5 and a sealing plate 6 that is joined to the package body 5 and forms a cavity C between itself and the package body 5. The package body 5 comprises a first base substrate 10 and a second base substrate 11 that are joined together in an overlapping state, and a seal ring 12 that is joined on the second base substrate 11.

[0038] The first base substrate 10 is a ceramic substrate that has a rectangular shape when viewed from the thickness direction T in a plan view. The upper surface of the first base substrate 10 forms the bottom of the cavity C. A pair of external electrodes 21A and 21B are formed on the lower surface of the first base substrate 10, spaced apart in the longitudinal direction L. The external electrodes 21A and 21B are composed of a single layer film of a single metal formed by, for example, vapor deposition or sputtering, or a multilayer film of different metals stacked on top of each other.

[0039] The second base substrate 11 is a ceramic substrate having the same shape as the first base substrate 10 in plan view, and is integrally bonded to the first base substrate 10 by sintering or the like while superimposed on it. The ceramic material used for each base substrate 10, 11 is, for example, alumina HTCC (High Temperature Co-Fired) It is possible to use materials such as ceramics or LTCC (Low Temperature Co-Fired Ceramic) made of glass ceramics.

[0040] As shown in Figures 3 and 4, the second base substrate 11 has a through-hole 11a that penetrates the second base substrate 11 in the thickness direction T. The through-hole 11a has a rounded rectangular shape in plan view. On the inner surface of the through-hole 11a, mounting portions 14A and 14B are separately formed on both sides in the width direction W, protruding inward in the width direction W. The mounting portions 14A and 14B are located in the central part of the second base substrate 11 in the longitudinal direction L.

[0041] A pair of electrode pads 20A and 20B, which are connection electrodes to the piezoelectric vibrator 3, are formed on the mounting sections 14A and 14B. The electrode pads 20A and 20B, like the external electrodes 21A and 21B described above, are composed of a single layer film of a single metal formed by, for example, vapor deposition or sputtering, or a laminated film of different metals. The electrode pads 20A and 20B and the external electrodes 21A and 21B are electrically connected to each other via through-wiring (not shown) that penetrates each base substrate 10 and 11 in the thickness direction T.

[0042] Each base substrate 10, 11 has a quarter-circular arc-shaped notch 15 formed at its four corners, extending over the entire thickness T of both base substrates 10, 11. Each base substrate 10, 11 is manufactured, for example, by joining two wafer-shaped ceramic substrates together, forming a matrix of through-holes penetrating both ceramic substrates, and then cutting both ceramic substrates in a grid pattern using each through-hole as a reference. In this process, the through-holes are divided into four sections, thereby forming the aforementioned notches 15.

[0043] The seal ring 12 is a conductive frame-shaped member that is slightly smaller than the outer dimensions of each base substrate 10, 11, and is joined to the upper surface of the second base substrate 11. Specifically, the seal ring 12 is joined to the second base substrate 11 by baking with a soldering material such as silver solder, or by welding to a metal bonding layer formed on the second base substrate 11. The seal ring 12, together with the inner surface of the second base substrate 11 (through portion 11a), constitutes the side wall of the cavity C. In the illustrated example, the inner surface of the seal ring 12 is positioned flush with the inner surface of the second base substrate 11.

[0044] Examples of materials for the seal ring 12 include nickel-based alloys, and specifically, it can be selected from Kovar, Elinvar, Invar, 42-alloy, etc. In particular, it is preferable to select a material for the seal ring 12 that has a coefficient of thermal expansion close to that of the ceramic base substrates 10 and 11. For example, the base substrates 10 and 11 have a coefficient of thermal expansion of 6.8 × 10⁻⁶. -6 When using alumina at / °C, the thermal expansion coefficient of the seal ring 12 is 5.2 × 10 -6 Kovar with a temperature of / ℃, and a thermal expansion coefficient of 4.5~6.5 × 10 -6 It is preferable to use a 42-alloy with a temperature of / ℃.

[0045] The sealing plate 6 is made of a conductive substrate and is bonded onto the sealing ring 12 to hermetically seal the inside of the package body 5. The space defined by the sealing ring 12, the sealing plate 6, and the respective base substrates 10 and 11 constitutes a hermetically sealed cavity C.

[0046] The piezoelectric vibrator 3 is housed within the cavity C of the hermetically sealed package 2. The piezoelectric vibrator 3 comprises a piezoelectric plate 30 formed from a piezoelectric material such as quartz, lithium tantalate, or lithium niobate. The piezoelectric plate 30 has a pair of vibrating arms 31, 32 and a pair of support arms 33, 34. The piezoelectric vibrator 3 is mounted in the package 2 within the cavity C by conductive adhesive, with the support arms 33, 34 being supported by the mounting sections 14A, 14B of the package 2. As a result, the piezoelectric vibrator 3 is supported within the cavity C with the vibrating arms 31, 32 floating above the base substrates 10, 11. Two sets of excitation electrodes 41, 42 (see Figure 5) are arranged on the outer surfaces of the vibrating arms 31, 32, which vibrate the pair of vibrating arms 31, 32 when a predetermined voltage is applied.

[0047] To operate the piezoelectric vibrator 1, a predetermined voltage is applied to the external electrodes 21A and 21B (see Figure 2). This creates a potential difference between the excitation electrodes 41 and 42, and generates an electric field between them. Each vibrating arm 31 and 32 vibrates at a predetermined resonant frequency, for example, in a direction that moves them closer together or further apart, due to the inverse piezoelectric effect caused by the electric field generated between the excitation electrodes 41 and 42. The vibration of each vibrating arm 31 and 32 is then used as a time source, a timing source for control signals, a reference signal source, etc.

[0048] (Piezoelectric vibrating piece of the embodiment) The piezoelectric vibrating piece 3 of the embodiment will be described in detail. Figure 5 is a perspective view of the piezoelectric vibrator according to the embodiment. Figure 6 is a plan view of the piezoelectric vibrator according to the embodiment. Note that in Figure 6, a portion of the electrode film 40 on each vibrating arm 31, 32 is shown in a cutaway view. As shown in Figures 5 and 6, the piezoelectric vibrator 3 comprises a piezoelectric plate 30 and an electrode film 40 disposed on the outer surface of the piezoelectric plate 30.

[0049] The piezoelectric plate 30 is formed by slicing a Lambert crystal ore at predetermined angles with respect to the X-axis (electrical axis), Y-axis (mechanical axis), and Z-axis (optical axis), which are mutually orthogonal to each other, to form a wafer, and then shaping this wafer by etching. In the following description, when describing the configuration of the piezoelectric vibrator 3, a coordinate system in which the X-axis, Y'-axis, and Z'-axis are mutually orthogonal will be used. The Z'-axis is the axis obtained by rotating the Z-axis around the X-axis. The Z'-axis is inclined in the range of 1° to 18° with respect to the Z-axis. Preferably, the Z'-axis is inclined in the range of 5° to 9° with respect to the Z-axis. The Y'-axis is the axis obtained by rotating the Y-axis at the same angle as the Z-axis in a plane containing the Z-axis and Y-axis with the X-axis as the axis of rotation. In the diagram, the direction of the arrows in the X-axis direction, Y'-axis direction, and Z'-axis direction will be described as + and the direction opposite to the arrows will be described as -. In the piezoelectric plate of this embodiment, the Z'-axis direction coincides with the thickness direction of the piezoelectric plate 30. In the following explanation, the term "width" refers to the size of a portion that extends in any direction when viewed from the Z' axis, in a plan view, in the direction perpendicular to the aforementioned arbitrary direction.

[0050] The piezoelectric plate 30 comprises a base portion 35, a pair of vibrating arms 31, 32 (first vibrating arm 31 and second vibrating arm 32) extending from the base portion 35 to the + side in the Y' axis direction, and a pair of support arms 33, 34 (first support arm 33 and second support arm 34) located on the + and - sides in the X axis direction relative to the base portion 35. The piezoelectric plate 30 is formed symmetrically on both sides and symmetrically with respect to an imaginary line extending in the Y' axis direction in a plan view, excluding etching residue described later. The piezoelectric plate 30 is formed by isotropic etching such as wet etching.

[0051] The base portion 35 is formed in a rectangular shape in plan view. The base portion 35 has a front surface 35a facing the + side in the Y' axis direction. The front surface 35a extends along the X axis direction in plan view. A pair of vibrating arms 31 and 32 are connected to the front surface 35a at intervals in the X direction. Hereinafter, the portion of the front surface 35a located between the pair of vibrating arms 31 and 32 will be referred to as the groin portion 50.

[0052] The first vibrating arm 31 and the second vibrating arm 32 are arranged parallel to each other in the X-axis direction. Each vibrating arm 31, 32 vibrates in a direction approaching and separating from each other, with its base end on the base 35 side as the fixed end and its tip as the free end. Each vibrating arm 31, 32 has an arm portion 36 extending from the base 35 and a weight portion 37 connected to the tip of the arm portion 36 and formed to be wider than the arm portion 36. The arm portion 36 extends from the front surface 35a of the base 35 to the + side in the Y' axis direction. The arm portion 36 extends with a constant width along its entire length in the Y' axis direction.

[0053] The weight portion 37 is located at the tips of the vibrating arms 31 and 32. The weight portion 37 extends from the tip of each arm portion 36 towards the + side in the Y' axis direction. The weight portion 37 as a whole is larger on both sides in the X axis direction than the arms 36.

[0054] Each vibrating arm 31, 32 has a pair of grooves 60 formed therein. The grooves 60 are recessed in the Z' direction on both main surfaces of the piezoelectric plate 30 that face the Z' direction. The grooves 60 extend in the Y' direction between the ends of the arms 36.

[0055] Here, the space between the pair of vibrating arms 31 and 32 is referred to as a slit. The piezoelectric plate 30 has an inner wall surface that defines the slit. The inner wall surface includes the groin portion 50 of the front side surface 35a of the base portion 35 and the side surfaces of each vibrating arm 31 and 32 that connect to the groin portion 50. Etching residue 55 formed on the inner wall surface when the piezoelectric plate 30 was molded is formed thereon. The etching residue 55 appears due to differences in etching rates for each crystal plane of the quartz substrate. The etching residue 55 is formed by an outer surface parallel to the crystal plane. The etching residue 55 has a pair of corner residues 56 that are formed to fill the corners of the slit on the base end side of each vibrating arm 31 and 32. The pair of corner residues 56 are spaced apart from each other in the X-axis direction in a plan view.

[0056] Figure 7 is an enlarged view of section VII in Figure 6. Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 7. Note that the electrode film 40 is not shown in Figure 8. As shown in Figures 7 and 8, the corner residue 56 has an edge 56a that extends in plan view between the crotch 50 of the front surface 35a of the base 35 and the sides of the vibrating arms 31 and 32. The edge 56a extends linearly over substantially its entire length in plan view. However, the edge 56a may have one or more inflection points in plan view. The edges 56a of a pair of corner residues 56 are spaced apart from each other in the X-axis direction in plan view. The +Y'-axis end of each corner residue 56 is located in the +Y'-axis direction more in the +Y'-axis direction than the -Y'-axis end of the groove 60 of the adjacent vibrating arms 31 and 32. The corner residue 56 is formed such that its thickness in the Z'-axis direction increases from the edge 56a toward the crotch 50 of the front surface 35a of the base 35 and toward the sides of the vibrating arms 31 and 32, respectively.

[0057] As shown in Figure 7, the crotch portion 50 of the front surface 35a of the base portion 35 has a residue region 51 defined as the area where etching residue 55 is formed in a plan view, and a non-residue region 52 defined as the area where etching residue 55 is not formed in a plan view. The residue region 51 is the area where a pair of corner residues 56 are formed in the X-axis direction. The non-residue region 52 is the area sandwiched between the pair of residue regions 51 in the X-axis direction. In the direction in which the pair of vibrating arms 31, 32 are aligned (X-axis direction), the dimension of the crotch portion 50 relative to the dimension of the residue region 51 is 1.1 or greater. The dimension of the residue region 51 is the sum of the dimensions of the pair of residue regions 51, which is the sum of the dimensions of the pair of corner residues 56. The direction in which the pair of vibrating arms 31, 32 are aligned is the direction perpendicular to the longitudinal direction of the piezoelectric plate 30 in a plan view.

[0058] As shown in Figures 7 and 8, the front surface 35a of the base 35 is inclined with respect to the Z' axis in the non-residue region 52. The front surface 35a of the base 35 is parallel to the Z axis (the optical axis of the crystal) in the non-residue region 52. That is, the front surface 35a of the base 35 is inclined with respect to the Z' axis at the same angle as the inclination angle of the Z' axis with respect to the Z axis in the non-residue region 52. The front surface 35a of the base 35 is oriented in the +Y' axis direction and the +Z' axis direction throughout the entire non-residue region 52.

[0059] As shown in Figure 6, each support arm 33, 34 has an L-shape in plan view and extends outward from the base 35, sandwiching the pair of vibrating arms 31, 32 between them. Specifically, each support arm 33, 34 protrudes outward in the X-axis direction from both end faces in the X-axis direction of the base 35, and then extends to the + side in the Y' axis direction. The first support arm 33 is positioned opposite the second vibrating arm 32 to the first vibrating arm 31. The second support arm 34 is positioned opposite the first vibrating arm 31 to the second vibrating arm 32.

[0060] The electrode film 40 is, for example, a multilayer film of chromium (Cr) and gold (Au), formed by first depositing a chromium film with good adhesion to quartz as a base, and then laminating a thin gold film on top of the chromium film. However, the film composition of the electrode film 40 is not limited to this; for example, a thin gold film may be further laminated on top of a multilayer film of chromium and nichrome (NiCr), or a single layer film of chromium, nickel, aluminum (Al), titanium (Ti), etc.

[0061] The electrode film 40 comprises excitation electrodes 41, 42, mounting electrodes 43, 44, and wiring 45, 46. As shown in Figures 5 and 6, two sets of excitation electrodes 41 and 42 are provided on the outer surfaces of the vibrating arms 31 and 32. Each excitation electrode 41 and 42 is patterned to be electrically insulated from each other. The excitation electrodes 41 and 42 consist of a first excitation electrode 41 and a second excitation electrode 42. The first excitation electrode 41 is formed on both sides of the arm portion 36 of the first vibrating arm 31 facing the X-axis direction, and inside the grooves of the pair of groove portions 60 of the second vibrating arm 32. Furthermore, the first excitation electrode 41 is formed extending from the side surface of the first vibrating arm 31 to the crotch portion 50 of the front surface 35a of the base portion 35. The first excitation electrode 41 covers the entire surface defining each groove portion 60 of the second vibrating arm 32. The second excitation electrode 42 is formed inside the grooves 60 of the pair of grooves 60 of the first vibrating arm 31 and on both sides of the arm portion 36 of the second vibrating arm 32 that face the X-axis direction. The second excitation electrode 42 covers the entire surface defining each groove 60 of the first vibrating arm 31. Furthermore, the second excitation electrode 42 is formed extending from the side surface of the second vibrating arm 32 to the crotch portion 50 of the front side surface 35a of the base portion 35. When a predetermined driving voltage is applied between the excitation electrodes 41 and 42, the excitation electrodes 41 and 42 generate an electric field in each vibrating arm 31 and 32, causing each vibrating arm 31 and 32 to vibrate in the X-axis direction. In each of the vibrating arms 31 and 32, the excitation electrodes 41 and 42 on both sides are electrically connected to each other at the tip of the vibrating arm 31 and 32 by a part of the electrode film 40.

[0062] The mounting electrodes 43 and 44 are provided as mounting parts when mounting the piezoelectric vibrator 3 onto the package 2. The mounting electrodes 43 and 44 are provided on the main surface (back surface) at the tip of the support arms 33 and 34. Specifically, the mounting electrodes 43 and 44 include a first mounting electrode 43 positioned on the first support arm 33 and a second mounting electrode 44 positioned on the second support arm 34. The first mounting electrode 43 is electrically connected to the first excitation electrode 41. The second mounting electrode 44 is electrically connected to the second excitation electrode 42. The mounting electrodes 43 and 44 are electrically connected to the electrode pads 20A and 20B of the package 2 via a conductive adhesive.

[0063] Wirings 45 and 46 connect the excitation electrodes 41 and 42 to the mounting electrodes 43 and 44. Wirings 45 and 46 comprise a first wiring 45 connected to the first excitation electrode 41 or the first mounting electrode 43, and a second wiring 46 connected to the second excitation electrode 42 or the second mounting electrode 44. The first wiring 45 and the second wiring 46 are spaced apart from each other on both main surfaces of the base 35. At least one location in the X-axis direction of the base 35, the wirings 45 and 46 are arranged on the main surface of the base 35 to cover 40% or more of its width in the Y' axis direction.

[0064] As shown in Figure 7, the electrode film 40 is not located in the non-residue region 52 of the crotch portion 50 of the front surface 35a of the base portion 35, and the first excitation electrode 41 and the second excitation electrode 42 are separated from each other in the non-residue region 52. More specifically, in the crotch portion 50, the entire edge of the first excitation electrode 41 on the side of the second excitation electrode 42, and the entire edge of the second excitation electrode 42 on the side of the first excitation electrode 41, are located in the residue region 51.

[0065] As described above, the front surface 35a of the base 35 of the piezoelectric plate 30 is located between a pair of vibrating arms 31 and 32 and has a groin portion 50 on which the first excitation electrode 41 and the second excitation electrode 42 are provided. The groin portion 50 has a residue region 51 defined as the area where etching residue 55 is formed in a plan view, and a non-residue region 52 defined as the area where etching residue 55 is not formed in a plan view. The front surface 35a of the base 35 is inclined with respect to the thickness direction of the piezoelectric plate 30 in the non-residue region 52. With this configuration, the non-residue region 52 of the groin portion 50 is an area where the light irradiated in the thickness direction of the piezoelectric plate 30 during the exposure process when forming the first excitation electrode 41 and the second excitation electrode 42 by photolithography is not obstructed by the etching residue 55. Therefore, exposure defects caused by etching residue 55 can be suppressed. Furthermore, if the side surface of the base is substantially parallel to the thickness direction of the piezoelectric plate, the resist film on the side surface of the base may not be exposed during the exposure process, regardless of the presence or absence of etching residue. According to this embodiment, since the front side surface 35a of the base 35 is inclined with respect to the thickness direction of the piezoelectric plate 30, the light irradiated in the thickness direction of the piezoelectric plate 30 during the exposure process can be applied to the entire non-residue region 52. This makes it possible to reliably expose the positive-type resist film on the non-residue region 52 during the exposure process, and a gap between the first excitation electrode 41 and the second excitation electrode 42 can be formed in the non-residue region 52, thereby reliably separating and insulating the first excitation electrode 41 and the second excitation electrode 42 from each other. Therefore, it is possible to suppress the occurrence of a short circuit between the excitation electrodes 41 and 42 in the crotch 50 between the pair of vibrating arms 31 and 32.

[0066] Furthermore, if the side surface of the base is inclined with respect to the thickness direction of the piezoelectric plate, during the exposure process, the light from the side not facing the base surface will not hit the base surface. Therefore, if the light facing the base surface is blocked by etching residue during the exposure process, creating a shadow on the base surface, the area of ​​the shadow will also not be hit by light from the side not facing the base surface, potentially resulting in poor exposure. Accordingly, as in this embodiment, it is effective to incline the front surface 35a of the base 35 with respect to the thickness direction of the piezoelectric plate 30, and to further provide a non-residue area 52 in the crotch portion 50 of the front surface 35a of the base 35.

[0067] The wirings 45 and 46 are arranged at least at one location in the X-axis direction of the base 35, covering 40% or more of the width in the Y' axis direction on the main surface of the base 35. With this configuration, the electrically insulated wirings 45 and 46 are in close proximity to each other on the main surface of the base 35, making them prone to short circuits. For this reason, it is difficult to recess the front surface 35a of the base 35 at the crotch portion 50, as described in the above-mentioned Patent Document 1, in order to avoid the wirings 45 and 46 being in close proximity to each other. This embodiment can suppress short circuits between the excitation electrodes 41 and 42 without recessing the front surface 35a of the base 35, and is therefore a suitable configuration for achieving the above-mentioned effects.

[0068] The piezoelectric plate 30 is formed from a quartz substrate. The front surface 35a of the base 35 is parallel to the optical axis, which is the crystal axis of the quartz, in the non-residue region 52. With this configuration, because the quartz substrate has the characteristic of forming crystal planes parallel to the optical axis by isotropic etching, the non-residue region 52 of the front surface 35a of the base 35 can be tilted with respect to the thickness direction of the piezoelectric plate 30 without additional processing.

[0069] The thickness direction of the piezoelectric plate 30 is inclined within a range of 1° to 18° with respect to the optical axis, which is the crystal axis of the quartz. With this configuration, by setting the inclination angle of the thickness direction of the piezoelectric plate 30 with respect to the optical axis to 1° or more, the non-residue region 52 of the front surface 35a of the base portion 35 can be more easily exposed to light during the exposure process.

[0070] Figure 9 is a graph showing the relationship between the cut angle of the piezoelectric plate and the oscillation efficiency of the piezoelectric vibrator. The cut angle is the angle of inclination of the piezoelectric plate in the thickness direction relative to the optical axis of the quartz crystal. As shown in Figure 9, it was found that the oscillation efficiency becomes 0.95 or higher when the tilt angle of the piezoelectric plate 30 in the thickness direction with respect to the optical axis is 18° or less. If the oscillation efficiency falls below 0.95, the Q value decreases and the characteristics of the piezoelectric vibrator deteriorate. Therefore, by setting the tilt angle to 18° or less, the decrease in efficiency of bending vibration can be suppressed.

[0071] Figure 10 is a graph showing the relationship between the cut angle of the piezoelectric plate and the apex temperature. The apex temperature is the temperature at the peak of the frequency-temperature characteristic curve of the piezoelectric vibrator. The thickness direction of the piezoelectric plate 30 is inclined within a range of 5° to 9° with respect to the optical axis of the quartz crystal. With this configuration, as shown in Figure 10, the peak temperature of the piezoelectric vibrator 3 can be set to 20° to 30°. Assuming a room temperature of 25°C as the reference temperature range for actual use, setting the peak temperature to 20° to 30° allows the frequency variation range of the piezoelectric vibrator 3 to be of an acceptable size. Therefore, a piezoelectric vibrator 3 with excellent temperature characteristics can be obtained.

[0072] The first excitation electrode 41 and the second excitation electrode 42 are not located in the non-residue region 52. With this configuration, sufficient space is provided between the first excitation electrode 41 and the second excitation electrode 42, so that short circuits between the excitation electrodes 41 and 42 can be suppressed more reliably.

[0073] In the direction in which the pair of vibrating arms 31 and 32 are aligned, the dimension of the crotch portion 50 relative to the dimension of the residue region 51 is 1.1 or greater. With this configuration, a large non-residue region 52 can be secured in the direction in which the pair of vibrating arms 31 and 32 are aligned. Therefore, the first excitation electrode 41 and the second excitation electrode 42 can be separated more reliably when forming a metal film by photolithography.

[0074] The piezoelectric vibrator 1 comprises a piezoelectric vibrator 3 and a package 2 that hermetically seals the piezoelectric vibrator 3. The oscillator 100 comprises the piezoelectric vibrator 1 electrically connected to an integrated circuit as an oscillator. Thus, a high-quality piezoelectric vibrator 1 and oscillator 100 can be obtained.

[0075] In the above embodiment, the first excitation electrode 41 and the second excitation electrode 42 are not located in the non-residue region 52, but the configuration is not limited to this. As shown in Figure 11, the first excitation electrode 41 and the second excitation electrode 42 may be located from the residue region 51 to the non-residue region 52 and separated from each other in the non-residue region 52. More specifically, in the crotch portion 50, the entire edge of the first excitation electrode 41 on the side of the second excitation electrode 42, and the entire edge of the second excitation electrode 42 on the side of the first excitation electrode 41, may each be located in the non-residue region 52. With this configuration, the area irradiated with light during the exposure process is limited to the non-residue region 52 on the front surface 35a of the base portion 35, so that the positive-type resist film on the sides of the vibrating arms 31 and 32 is not unintentionally exposed to light. This ensures that the excitation electrodes 41 and 42 on the sides of the vibrating arms 31 and 32 are reliably formed into the desired shape, and suppresses an increase in the CI (crystal impedance) value of the piezoelectric vibrator 3.

[0076] As shown in Figure 12, one of the first excitation electrode 41 and the second excitation electrode 42 (the second excitation electrode 42 in the illustrated example) may not be located in the non-residue region 52, and the other of the first excitation electrode 41 and the second excitation electrode 42 (the first excitation electrode 41 in the illustrated example) may be located in the non-residue region 52. With this configuration, compared to a configuration in which the first excitation electrode 41 and the second excitation electrode 42 are located in the non-residue region 52, sufficient space is provided between the first excitation electrode 41 and the second excitation electrode 42, so that short circuits between the excitation electrodes 41 and 42 can be suppressed more reliably. Furthermore, compared to a configuration in which the first excitation electrode 41 and the second excitation electrode 42 are not located in the non-residue region 52, the area irradiated with light during the exposure process is narrower on the front surface 35a of the base 35, so that the positive-type resist film on the sides of the vibrating arms 31 and 32 is suppressed from being unintentionally exposed to light. This ensures that the excitation electrodes 41 and 42 on the sides of the vibrating arms 31 and 32 are reliably formed into the desired shape, thereby suppressing an increase in the CI value of the piezoelectric vibrator.

[0077] It should be noted that the present invention is not limited to the embodiments described above with reference to the drawings, and various modifications are conceivable within its technical scope. For example, in the above embodiment, the piezoelectric vibrator 3 was a so-called side-arm type vibrator, in which each support arm 33, 34 was positioned outside each vibrating arm 31, 32. However, the configuration is not limited to this, and the piezoelectric vibrator may be a vibrator without support arms.

[0078] In the above embodiment, the excitation electrodes 41 and 42 are not arranged over the entire non-residue region 52 of the crotch portion 50 of the base portion 35, but the configuration is not limited to this. The excitation electrodes 41 and 42 only need to be divided within the non-residue region 52, and at least one of the first excitation electrode 41 and the second excitation electrode 42 may be arranged in a part of the non-residue region 52.

[0079] Furthermore, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, without departing from the spirit of the present invention. [Explanation of Symbols]

[0080] 1...Piezoelectric vibrator 2...Package 3...Piezoelectric vibrating piece 30...Piezoelectric plate 31...First vibrating arm (vibrating arm) 32...Second vibrating arm (vibrating arm) 33...First support arm (support arm) 34...Second support arm (support arm) 35...Base 35a...Front side (side) 41...First excitation electrode 42...Second excitation electrode 50...Band 51...Residue area 52...Non-residue area 55...Etching residue 100...Oscillator 103...Integrated circuit

Claims

1. A piezoelectric plate having a base and a pair of vibrating arms extending from the base in the same direction, A first excitation electrode and a second excitation electrode are provided on each of the pair of vibrating arms, and each of the pair of vibrating arms generates an electric field. Equipped with, The side surface of the base is located between the pair of vibrating arms and has a groin portion on which the first excitation electrode and the second excitation electrode are provided. The aforementioned crotch area is, A residue region defined as the area in which etching residue is formed when viewed from the thickness direction of the piezoelectric plate, A non-residue region defined as the range in which no etching residue is formed when viewed from the thickness direction, It has, The side surface of the base is inclined with respect to the thickness direction in the non-residue region. Piezoelectric vibrating element.

2. The piezoelectric plate is formed from a quartz substrate, The side surface of the base is parallel to the optical axis, which is the crystal axis of the quartz, in the non-residue region. The piezoelectric vibrating piece according to claim 1.

3. The piezoelectric plate is formed from a quartz substrate, The aforementioned thickness direction is inclined within a range of 1° to 18° with respect to the optical axis, which is the crystal axis of the quartz. The piezoelectric vibrating piece according to claim 2.

4. The aforementioned thickness direction is inclined within a range of 5° to 9° with respect to the optical axis of the quartz crystal. The piezoelectric vibrating piece according to claim 3.

5. The first excitation electrode and the second excitation electrode are not located in the non-residue region. A piezoelectric vibrating piece according to any one of claims 1 to 4.

6. The first excitation electrode and the second excitation electrode are arranged in the non-residue region and are separated from each other in the non-residue region. A piezoelectric vibrating piece according to any one of claims 1 to 4.

7. One of the first excitation electrode and the second excitation electrode is not located in the non-residue region. The other of the first excitation electrode and the second excitation electrode is located in the non-residue region. A piezoelectric vibrating piece according to any one of claims 1 to 4.

8. In the direction in which the pair of vibrating arms are aligned, the dimension of the groin portion relative to the dimension of the residue region is 1.1 or greater. A piezoelectric vibrating piece according to any one of claims 1 to 4.

9. The piezoelectric plate further comprises a pair of support arms that extend outward from the base so as to sandwich the pair of vibrating arms between them. A piezoelectric vibrating piece according to any one of claims 1 to 4.

10. A piezoelectric vibrating piece according to any one of claims 1 to 4, A package for hermetically sealing the piezoelectric vibrator, A piezoelectric vibrator equipped with the following features.

11. The piezoelectric vibrator described in claim 10 is provided, The piezoelectric vibrator is electrically connected to the integrated circuit as an oscillator. Oscillator.

Images