JP2017201772A - Piezoelectric piece, piezoelectric vibration element, piezoelectric vibration device, and method of manufacturing piezoelectric piece - Google Patents

Abstract

A piezoelectric piece capable of reducing crystal impedance is provided. A crystal piece has a base and a vibrating arm extending from the base. The vibrating arm 23 has a D1 axis on at least one of an upper surface and a lower surface that are parallel to the extending direction of the pair of vibrating arms 23 (D2 axis direction) and the arranging direction of the pair of vibrating arms 23 (D1 axis direction). By providing the two concave portions 51 (grooves 41) in the direction, it has a pair of outer walls 45 located on both sides of the two concave portions 51 and an inner wall 47 located between the two concave portions 51. ing. The middle wall 47 has a top portion located at a position lower than the top portions of the pair of outer walls 45 and is thinner than the pair of outer walls 45 at the same height. [Selection] Figure 5

Description

  The present invention relates to a piezoelectric piece, a piezoelectric vibrating element, a piezoelectric vibrating device, and a method for manufacturing a piezoelectric piece.

  As a piezoelectric vibration device (for example, a vibrator or an oscillator) used for generating an oscillation signal, for example, a tuning fork type is known (for example, Patent Document 1). In a tuning fork type piezoelectric vibration device, a piezoelectric piece (for example, a crystal piece) having a base and a pair of arms extending in parallel from the base, a voltage is applied to the pair of arms to form a pair of arms. An oscillation signal is generated using the vibration generated in the above.

  In Patent Document 1, a piezoelectric piece in which one groove extending along the arm portion is formed on the upper surface and the lower surface of the arm portion (a surface parallel to the extending direction of the pair of arm portions and the arrangement direction of the pair of arm portions). Is disclosed. Further, in Patent Document 1, as a method of forming this single groove by etching, first, two thin grooves are formed by etching, and then the protrusions between the two thin grooves are etched. A method of forming a single thick groove is proposed.

  Patent Document 1 also proposes a method in which the above-mentioned protrusions are left slightly without being completely removed. In Patent Document 1, by leaving the protrusions in one thick groove, the surface area in one thick groove can be increased, and consequently the area of the excitation electrode can be increased, and the crystal impedance (CI) Can be lowered. Moreover, in patent document 1, it is supposed that the rigidity of an arm part can be ensured by a protrusion part, deepening the deepest part of one thick groove | channel and reducing CI.

JP 2004-88706 A

  A reduction in CI is always required. Various methods for reducing the CI are preferably proposed from the viewpoint of improving the degree of freedom in design and / or the choice of manufacturing method. Therefore, it is desirable to provide a piezoelectric piece, a piezoelectric vibrating element, a piezoelectric vibrating device, and a method for manufacturing the piezoelectric piece that can reduce CI with a new configuration or procedure.

  The piezoelectric piece according to one aspect of the present invention includes an arm portion extending in a direction intersecting with the polarization direction, and the arm portion is long in parallel to the direction in which the arm portion extends and along the polarization direction. And a pair of outer walls located on both sides of the two or more recesses, and the two or more recesses. One or more middle walls positioned between the pair of outer walls, the tops of which are lower than the tops of each of the pair of outer walls and at the same height. Thinner than each.

  Preferably, the pair of outer walls have the same height at the top and the same thickness at the same height.

  Preferably, the arm portion has one or more transverse walls positioned between the two or more recesses of the plurality of sets by providing a plurality of sets of the two or more recesses in the extending direction. And the top of the transverse wall is higher than the top of the middle wall.

  The piezoelectric vibration element according to an aspect of the present invention is the above-described piezoelectric piece, the first electrode disposed across the two or more recesses on the predetermined surface, and the predetermined surface of the arm portion. And a second electrode disposed on each side of the width direction and disposed on each of a pair of side surfaces intersecting the predetermined surface.

  A piezoelectric vibration device according to an aspect of the present invention includes the above-described piezoelectric vibration element and a mounting substrate on which the piezoelectric vibration element is mounted.

  A method for manufacturing a piezoelectric piece according to an aspect of the present invention includes: a mask forming step of forming a mask on a main surface along a polarization direction of a piezoelectric wafer; and an etching step of etching the piezoelectric wafer through the mask. The mask has a long arm portion corresponding portion, and the arm portion corresponding portion is provided with two or more openings in the width direction of the arm portion corresponding portion. A pair of outer wall corresponding portions located on both sides of the two or more openings, and one or more middle wall corresponding portions positioned between the two or more openings, It is thinner than the pair of outer wall corresponding portions, and in the etching step, both the etching outside the arm corresponding portion and the etching in the two or more openings are started, and the main surface of the piezoelectric wafer is the The area that was in contact with the corresponding part of the middle wall is the front Etching is continued from one edge of the middle wall corresponding portion to be etched over the other edge.

  According to the above configuration or procedure, the crystal impedance can be reduced.

1 is an exploded perspective view showing a schematic configuration of a crystal resonator according to an embodiment of the present invention. 2A is a plan view showing the inside of the crystal unit of FIG. 1, FIG. 2B is a cross-sectional view taken along line IIb-IIb in FIG. 2A, and FIG. 2C is FIG. 2A. Sectional drawing in the IIc-IIc line | wire. The typical perspective view which shows an example of the wiring of the crystal oscillation element of FIG. 4A is a plan view showing a portion corresponding to the region IVa in FIG. 2A of the crystal piece in FIG. 1, and FIG. 4B is an enlarged view in the region IVb in FIG. 4A. 5A is a cross-sectional view taken along the line Va-Va in FIG. 4B, and FIG. 5B is a cross-sectional view taken along the line Vb-Vb in FIG. 4B. 6 (a) and 6 (b) are schematic cross-sectional views showing a method for manufacturing the crystal piece of FIG. Fig.7 (a)-FIG.7 (c) are typical sectional drawings which show the continuation of FIG.6 (b).

  Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensional ratios and the like on the drawings do not necessarily match the actual ones.

  When the details of the shape of the crystal piece are described, an error (such as a systematic error) indicating a certain tendency, which is caused by the anisotropy of the crystal with respect to etching, may be considered. On the other hand, errors that are not reproducible (such as accidental errors) are basically ignored.

  For the sake of convenience, an orthogonal coordinate system including a D1 axis, a D2 axis, and a D3 axis may be attached to the drawing. In addition, in the crystal resonator and the like described below, any direction may be the vertical direction or the horizontal direction, but for convenience, terms such as an upper surface or a lower surface may be used with the positive side in the D3 axial direction as an upper side. . In addition, simply referring to the plan view means viewing in the D3 axis direction.

  For configurations that are the same or similar to each other, different numbers (first and second) are assigned to names (vibrating arms) that are common to each other, such as “first vibrating arm 23A” and “second vibrating arm 23B”. , Different uppercase alphabets (A, B) may be used as symbols. In this case, the number and the uppercase alphabet may be omitted so that the two are not distinguished, such as simply “vibrating arm 23”.

<Schematic configuration of crystal unit>
FIG. 1 is an exploded perspective view showing a schematic configuration of a crystal resonator 1 (hereinafter, “crystal” may be omitted) according to an embodiment of the present invention. FIG. 2A is a plan view showing the inside of the vibrator 1. FIG. 2B is a cross-sectional view taken along the line IIb-IIb in FIG. FIG.2 (c) is sectional drawing in the IIc-IIc line | wire of Fig.2 (a).

  For example, as shown particularly in FIG. 1, the vibrator 1 mainly includes three members. That is, the vibrator 1 includes a crystal resonator element 3 that vibrates when a voltage is applied (hereinafter, “crystal” may be omitted), an element mounting member 5 and a lid member for packaging the resonator element 3. 7.

  When the vibration element 3 is accommodated in the box-shaped element mounting member 5 and the element mounting member 5 is covered with the lid member 7, the vibrator 1 has, for example, a generally thin rectangular parallelepiped shape as a whole. The inside of the element mounting member 5 is sealed with, for example, a lid member 7. Moreover, the inside is evacuated, for example, or an appropriate gas (for example, nitrogen) is enclosed.

  The dimensions of the vibrator 1 may be set as appropriate. For example, in a relatively small one, the width (D1 axis direction) is 0.40 mm to 3.20 mm, the length (D2 axis direction) is 0.65 mm to 5.00 mm, and the thickness (D3 axis direction) is It is 0.2 mm or more and 1.2 mm or less.

  The vibrator 1 is disposed, for example, with a lower surface (surface on the negative side in the D3 axis direction) facing a mounting surface such as a circuit board (not shown), and is surface-mounted on the mounting surface by a bump made of solder or the like. . The vibrator 1 is applied with a voltage by an oscillation circuit provided on the circuit board, and contributes to generation of an oscillation signal.

  Hereinafter, in general, a basic configuration related to generation of vibration and a mounting structure of the vibration element 3 on the element mounting member 5 will be described in order, and then details of the vibration element 3 (more specifically, a vibration arm 23 described later) will be described. The shape of is described.

<Basic configuration related to vibration generation>
(Schematic configuration of vibration element)
For example, the vibration element 3 mounts the crystal element 15, the first excitation electrode 17 </ b> V and the second excitation electrode 17 </ b> H (FIG. 1) for applying a voltage to the crystal element 15, and the vibration element 3 on the element mounting member 5. The first element terminal 19A and the second element terminal 19B (FIG. 2B) are provided.

  In addition to the above, the vibration element 3 has appropriate wiring (described later). Although not particularly illustrated, the vibration element 3 may have a metal film for frequency adjustment (for weight adjustment of a vibration arm 23 described later).

(Basic shape of crystal piece: base and vibrating arm)
The crystal piece 15 is formed with a generally constant thickness (D3 axis direction) as a whole, and has an appropriate planar shape. Specifically, the crystal piece 15 is of a so-called tuning fork type, and has a base portion 21 and a first vibrating arm 23A and a second vibrating arm 23B extending in parallel from the base portion 21 as a basic configuration. Yes. The pair of vibrating arms 23 is a portion that vibrates when a voltage is applied by the excitation electrode 17, and the base portion 21 is a portion that supports the vibrating arm 23.

  The base 21 may have an appropriate shape, and is, for example, an outline and a thin rectangular parallelepiped shape. The upper surface, the lower surface, or the side surface may be curved. It is preferable that the base portion 21 has a shape that is generally plane symmetric with respect to the D2-D3 plane passing through the center and substantially plane symmetric with respect to the D1-D2 plane passing through the center. Further, the relative sizes of the base 21 in the D1 axis direction, the D2 axis direction, and the D3 axis direction may be set as appropriate. In the illustrated example, the base 21 is plate-shaped with the D3 axis direction as the thickness direction, but the size in the D3 axis direction may be larger than the size in the D1 axis direction and / or the D2 axis direction.

  The pair of vibrating arms 23 linearly extend from the base portion 21 in parallel (for example, in parallel) with each other in plan view. The roots of the pair of vibrating arms 23 are located, for example, in the vicinity of both end portions in the D1 axis direction with respect to the base portion 21. The shape (including dimensions) of the pair of vibrating arms 23 is, for example, generally the same. Except for the shape (described later) due to the anisotropy of the crystal with respect to the etching, the pair of vibrating arms 23 may have a line-symmetric shape. The shape of the cross section (cross section perpendicular to the D2 axis) of the vibrating arm 23 is, for example, a substantially rectangular shape except for the shape of details described later, and the shape and area of the cross section are the length of the vibrating arm 23. It is generally constant in direction. However, the vibrating arm 23 may have a so-called hammer shape, for example, by increasing the cross-sectional area in the D1 axis direction at the tip of the vibrating arm 23.

  The length (D2 axis direction) and width (D1 axis direction) dimensions of the vibrating arm 23 are set according to the frequency required for the vibrating element 3, as is well known. The thickness (D3 axis direction) of the vibrating arm 23 may be appropriately set from the viewpoint of securing strength and suppressing spurious.

  For example, the crystal piece 15 rotates the Y-axis (mechanical axis) and the Z-axis (optical axis) around the X-axis (electrical axis) in the range of about −5 ° to 5 °, and these are rotated in the Y′-axis and the Z ′. The X axis is the direction in which the pair of vibrating arms 23 are arranged (D1 axis direction), the Y ′ axis is the extending direction of the vibrating arm 23 (D2 axis direction), and the Z ′ axis is the vibrating arm 23. It is cut out so as to be in the thickness direction (D3 axis direction).

(Excitation electrode configuration)
The excitation electrode 17 is composed of, for example, a conductive layer provided on the surface of the vibrating arm 23. Specifically, the first excitation electrode 17V is provided on the upper and lower surfaces (the positive surface in the D3 axis direction and the negative surface in the D3 axis direction) of each vibrating arm 23. Further, the second excitation electrode 17H is provided on each side surface (the positive side surface in the D1 axis direction and the negative side surface in the D1 axis direction) of each vibrating arm 23. That is, in each vibrating arm 23, a total of four excitation electrodes 17 are provided on a total of four surfaces including the upper and lower surfaces and the side surfaces on both sides.

  The planar shape of the excitation electrode 17 is, for example, a substantially rectangular shape whose longitudinal direction is the direction in which the vibrating arm 23 extends. The width of each excitation electrode 17 is, for example, approximately the width over the width of each surface (upper and lower surfaces or side surfaces) of the vibrating arm 23 provided with each excitation electrode 17. However, in order to prevent the first excitation electrode 17V and the second excitation electrode 17H from short-circuiting each other, the width of at least one of these excitation electrodes 17 (the first excitation electrode 17V in the present embodiment) is provided by the excitation electrode 17. The width of the surface is slightly smaller. The length of the excitation electrode 17 (D2 axis direction) is appropriately set to be as long as possible within a range shorter than the length of the vibrating arm 23, for example. The position of the excitation electrode 17 on the base 21 side coincides with the root of the vibrating arm 23, for example.

  In addition, the conductive layer which comprises the excitation electrode 17, or the other conductive layer (pad 11, the external terminal 13, the element terminal 19, etc.) mentioned later is a metal layer, for example. The conductive layer may be composed of one layer (one kind of material), or may be composed of a plurality of layers.

(Excitation electrode potential)
In each vibrating arm 23, for example, the two first excitation electrodes 17V have the same potential, the two second excitation electrodes 17H have the same potential, and the first excitation electrode 17V and the second excitation electrode 17H An AC voltage is applied during Thereby, each vibrating arm 23 vibrates in the D1 axis direction.

  In the pair of vibrating arms 23, for example, the first excitation electrode 17V of the first vibrating arm 23A and the second excitation electrode 17H of the second vibrating arm 23B have the same potential, and the first vibrating arm 23A has the same potential. The second excitation electrode 17H and the first excitation electrode 17V of the second vibrating arm 23B are set to the same potential. Thereby, the pair of vibrating arms 23 vibrate in line symmetry with each other in plan view.

(Wiring structure of vibration element)
The relationship between the potentials of the excitation electrodes 17 and the application of the voltage to the excitation electrodes 17 as described above are performed by, for example, connecting the excitation electrodes 17 with each other by a wiring made of a conductive layer provided on the surface of the crystal piece 15 and exciting the excitation electrodes 17. This is realized by connecting the electrode 17 to the element terminal 19. For example, it is as follows.

  FIG. 3 is a schematic perspective view showing an example of the wiring 33 of the vibration element 3. The illustrated example is merely an example, and various other wirings are possible.

  In the illustrated example, the two second excitation electrodes 17 </ b> H of each vibrating arm 23 are connected to each other by a tip-side wiring 33 a provided on the tip side of the vibrating arm 23. The two first excitation electrodes 17V of each resonating arm 23 are connected to each other by outer wirings 33b passing through the side surfaces of the base 21 on both sides in the D1 axis direction. The second excitation electrode 17H located on the inner side surface (between the pair of vibration arms 23) of each vibration arm 23 and the first excitation electrode 17V on the upper surface or the lower surface of the other vibration arm 23 are the vibration arms of the base 21. They are connected to each other by an inner wiring 33c passing through the 23 side (D2 axial direction positive side) surface. The inner wiring 33c or the outer wiring 33b is connected to the element terminal 19 by a terminal wiring 33d extending on the lower surface (the negative side in the D3 axis direction) of the base portion 21. An AC voltage is applied to the pair of element terminals 19 via the element mounting member 5.

<Configuration related to mounting of vibration element>
A configuration related to mounting of the vibration element 3 is, for example, as follows. However, various known configurations may be applied to the configuration related to the mounting of the vibration element 3, and the configuration described below is merely an example.

(Shape for mounting on crystal piece: support arm and protrusion)
As shown in FIGS. 1 to 3, the crystal piece 15 includes a support arm 25 and a protrusion 27 in addition to the base portion 21 and the vibrating arm 23 described above. The support arm 25 and the protruding portion 27 are portions that contribute to the mounting of the crystal piece 15 on the element mounting member 5, for example, by providing the element terminal 19.

  For example, the support arm 25 extends from the base portion 21 to the side (the negative side in the D1 axial direction) and then bends, and extends in parallel (for example, parallel) to the pair of vibrating arms 23. The shape and dimensions of the support arm 25 may be set as appropriate. Note that the base of the support arm 25 is preferably as far away from the base of the vibrating arm 23 as possible. In the example shown in the drawing, the support arm 25 vibrates among the side surfaces of the base portion 21 (surface facing the D1 axis direction). It extends from the end opposite to the arm 23 (on the negative side in the D2 axial direction).

  For example, the protruding portion 27 protrudes from the base portion 21 to the side opposite to the side from which the support arm 25 (the base portion) extends from the base portion 21. The shape, size, and the like of the protruding portion 27 may be set as appropriate. The protrusion 27 is preferably as far away from the root of the vibrating arm 23 as the base of the support arm 25. In the illustrated example, the protrusion 27 extends from the base 21 of the support arm 25. Of the side surface opposite to the side surface, it protrudes from the end opposite to the vibrating arm 23.

(Element terminal configuration)
As shown in FIGS. 2B to 3, the element terminal 19 is constituted by a conductive layer provided on the surface of the support arm 25 or the protruding portion 27, for example. Specifically, for example, the first element terminal 19A is provided on the lower surface (the surface on the negative side in the D3 axial direction) of the bent portion of the support arm 25. The second element terminal 19B is provided on the lower surface (the negative surface in the D3 axis direction) of the protrusion 27. The planar shape and area of the element terminal 19 may be set as appropriate.

(Package structure)
As shown in FIGS. 1 and 2, the element mounting member 5 includes, for example, a base 9 that is the main body of the element mounting member 5 and a pad 11 for mounting the vibration element 3 (FIGS. 2A to 2 ( c)) and an external terminal 13 for mounting the vibrator 1 on a circuit board (not shown) or the like.

  The base 9 is made of an insulating material and has a recess 5 a that houses the vibration element 3. The insulating material which comprises the base | substrate 9 is a ceramic or resin, for example. In addition, the base | substrate 9 may be comprised from the several member. The bottom surface of the recess 5a that is the mounting surface of the vibration element 3 is, for example, planar.

  The pad 11 is made of, for example, a conductive layer provided on the bottom surface of the recess 5a. For example, two (one pair) pads 11 are provided. For example, the two pads 11 have the same thickness and are located on the same plane (the bottom surface of the recess 5a). The planar shape and area of the pad 11 may be set as appropriate.

  The positions of the pair of pads 11 are appropriately set according to the configuration of the vibration element 3. In the present embodiment, the pair of pads 11 are positioned at two corners on one short side (D2 axial direction negative side) of the generally rectangular bottom surface of the recess 5a.

  The external terminal 13 is constituted by, for example, a conductive layer provided on the lower surface (surface on the D3 axis negative side) of the base 9. The number, position, planar shape, and area of the external terminals 13 may be set as appropriate. For example, the external terminals 13 are provided at the four corners of the lower surface of the base 9. In the present embodiment, it is sufficient that at least two (one pair) external terminals 13 are provided corresponding to the two pads 11.

  Although not particularly illustrated, the pair of pads 11 and two of the four external terminals 13 are connected to each other by a wiring conductor provided on the base 9. The wiring conductor is constituted by, for example, a layered conductor and / or a via conductor provided inside the base body 9.

  The lid member 7 is made of, for example, metal, and is joined to the upper surface of the element mounting member 5 by seam welding or the like.

(Mounting of vibration element to package)
As shown in FIG. 2A to FIG. 2C, the vibration element 3 is disposed to face the bottom surface of the recess 5 a of the element mounting member 5, for example, and a pair of element terminals 19 and a pair of pads 11. Are joined and fixed to the element mounting member 5 (that is, mounted). The bonding is performed by, for example, bonding bumps 29 interposed between the element terminals 19 and the pads 11. The bonding bump 29 is made of, for example, a conductive adhesive. The conductive adhesive is made of, for example, a resin mixed with a conductive filler.

  Further, the vibration element 3 is supported on the bottom surface of the concave portion 5 a on the tip side of the bent portion of the support arm 25. Specifically, for example, a support bump 31 is provided on the bottom surface of the recess 5 a, and the lower surface of the distal end portion of the support arm 25 is in contact with and supported by the support bump 31. The support bump 31 may be made of, for example, a conductive adhesive or an insulating resin, and may be made of the same material as the bonding bump 29. Further, the support bumps 31 may not only contact the support arm 25 but also join the support arm 25 and the bottom surface of the recess 5a.

  Unlike the example shown in the figure, a pair of element terminals 19 may be provided at the tip and the bent portion of the support arm 25, and the bonding bumps 29 and the pads 11 may be provided corresponding to the positions. In this case, the protrusion 27 may be supported by the support bump 31, or the corner of the base 21 may be indicated by the support bump 31 without providing the protrusion 27.

<Detailed shape of vibrating arm>
(Outline of grooves and walls)
FIG. 4A is a plan view showing a portion corresponding to the region IVa in FIG. FIG. 4B is an enlarged view of the region IVb in FIG. Fig.5 (a) is sectional drawing in the Va-Va line | wire of FIG.4 (b). FIG.5 (b) is sectional drawing in the Vb-Vb line | wire of FIG.4 (b). In these drawings, the first vibrating arm 23A is illustrated, but the shape of the second vibrating arm 23B is the same.

  Each vibrating arm 23 has two grooves 41 extending on the upper surface and the lower surface, respectively, in the extending direction of the vibrating arm 23 (D2 axis direction). Each groove 41 has, for example, a length equivalent to that of the first excitation electrode 17V in the D2 axis direction.

  In the following description, terms such as “high” or “low” are used, regardless of whether the vibrating arm 23 is an upper surface or a lower surface, with the bottom side of the groove 41 being a lower side and the opening side of the groove 41 being an upper side. There is.

  In addition, since the shape of the upper surface and the shape of the lower surface of the vibrating arm 23 are formed by the same method (etching) based on the same idea, in the following description, basically, Only one of the lower surfaces (which may be any) will be described.

  By forming the two grooves 41, each vibrating arm 23 includes a pair of outer walls 45 positioned on both sides of the two grooves 41 and an intermediate wall 47 positioned between the two grooves 41. have. The pair of outer wall 45 and middle wall 47 rises with respect to the intermediate layer 43 (FIGS. 5A and 5B) located at the center in the vertical direction (D3 axis direction) of the vibrating arm 23, and the vibrating arm 23. Extends in the direction (D2 axial direction).

  In addition, the vibrating arm 23 includes one or more (a plurality in the present embodiment) transverse walls 49 (FIGS. 4A, 4B, and 5B) that cross each groove 41 in each groove 41. Have. From another viewpoint, the groove 41 is constituted by a plurality of recesses 51 (reference numerals are FIGS. 4A and 4B) arranged in the longitudinal direction of the vibrating arm 23.

  By forming the groove 41, for example, the crystal impedance (CI) is lowered. Specifically, for example, it is as follows. The first excitation electrode 17 </ b> V is also provided on the inner surfaces of the two grooves 41. For example, the first excitation electrode 17 </ b> V is provided across part of the top surfaces of the pair of outer walls 45, the inner surface of the groove 41, and the middle wall 47. Accordingly, the first excitation electrode 17V faces the second excitation electrode 17H across the outer wall 45 in the D1 axis direction. As a result, for example, in the electric field vector formed by voltage application to the first excitation electrode 17V and the second excitation electrode 17H, the component along the D1 axis direction is larger than when the groove 41 is not formed, The vibrating arm 23 vibrates efficiently, and the CI decreases.

  Instead of forming one groove on the upper surface or the lower surface of each vibrating arm 23, by forming two grooves 41 or providing a transverse wall 49, for example, a manufacturing method of the crystal piece 15 is achieved. Facilitated. Specifically, when the crystal blank 15 is etched through the mask, the opening of the mask corresponding to the groove 41 can be reduced to prevent the groove 41 from penetrating into a slit. This will be described later.

  This embodiment is characterized in that the middle wall 47 is lower and thinner than the outer wall 45. The specific shape of each part in the vibrating arm 23 is, for example, as follows.

(External wall structure)
The shape (including dimensions) of the transverse cross section of each outer wall 45 (the cross section perpendicular to the D2 axis shown in FIG. 5A) is, for example, substantially constant along its longitudinal direction (D2 axial direction). However, this is not the case depending on the influence of the transverse wall 49 on the etching of the outer wall 45. In the following description of the outer wall 45, the influence of the transverse wall 49 is ignored unless otherwise specified.

  The height (position in the D3 axis direction) of the top portion (top surface) of the outer wall 45 is the same between the pair of outer walls 45. Below, the dimension which concerns on the middle wall 47 may be demonstrated on the basis of the position of the top part of this outer wall 45. FIG. In addition, the top surface of the outer wall 45 is basically a planar shape orthogonal to the D3 axis, and is not necessarily a crystal plane. When the width of the top surface of the outer wall 45 (D1 axial direction) is small and / or under-etching is large, the highest position of the outer wall 45 may be the top of the outer wall 45.

  The shape (including dimensions) of the cross section of the outer wall 45 is substantially the same between the pair of outer walls 45. The same here basically takes into account an error (such as a systematic error) indicating a certain tendency caused by anisotropy of crystal etching. In addition, the same shape here is not a shape that is plane-symmetric with respect to the D2-D3 plane passing through the center of the vibrating arm 23, but a shape that overlaps by parallel movement. That is, between the pair of outer walls 45, the negative side wall surfaces of the D1 axis have the same shape, and the positive side wall surfaces of the D1 axis have the same shape.

  Specifically, for example, in the pair of outer walls 45, the same crystal plane appears as the wall surfaces, and the thickness t1 at the same height (the same position in the D3 axial direction) (D1 axial direction, FIG. a)) are generally identical to each other.

  The crystal plane is a plane formed at an angle unique to quartz with respect to the X axis to the Z axis due to the geometric regularity of the crystal lattice. In the drawings used in the description of the present embodiment, the number and angle of crystal planes are not accurately illustrated for convenience of illustration. The number and angle of crystal planes are defined by the relative relationship between the X axis to Z axis and the D1 axis to D3 axis, the etching direction, and the like.

  As described above, when wet etching is performed through a mask orthogonal to the D3 axis direction with the X axis as the D1 axis, the Y ′ axis as the D2 axis, the Z ′ axis as the D3 axis, and the outer wall 45 as a whole, In general, the thickness t1 at the base is asymmetrical with respect to the thickness t1 at the top, spreading to one side in the D1 axis direction (in the illustrated example, the negative side in the D1 axis direction). In addition, the outer wall 45 generally has an outer wall upper part 45a (FIG. 5A) in which the change of the thickness t1 with respect to the position in the D3 axis direction is relatively small, and a change in the thickness t1 with respect to the position in the D3 axis direction. The outer wall lower portion 45b (FIG. 5B) is larger. Each of the outer wall upper part 45a and the outer wall lower part 45b has an asymmetrical shape in which the base side extends to the one side in the D1 axis direction with respect to the top side.

  However, in the cross section illustrated in FIG. 5A, the pair of outer walls 45 are different from each other on the root side in the shape of the wall surface on the D1 axial direction positive side. This is because, in the outer wall 45 on the negative side in the D1 axial direction, the transverse wall 49 affects the etching that forms the wall surface on the positive side in the D1 axial direction of the outer wall 45, while in the outer side 45 on the positive side in the D1 axial direction. This is because the transverse wall 49 does not affect the etching that forms the wall on the D1 axial direction positive side of the outer wall 45. Specifically, for example, a part of the crystal plane constituting the transverse wall 49 appears only at the outer wall 45 on the negative side in the D1 axis direction of the pair of outer walls 45. The crystal plane may be regarded as a crystal plane constituting the transverse wall 49 and not the outer wall 45. In this case, even in the cross section illustrated in FIG. 5A, it can be said that the pair of outer walls 45 have the same shape.

  The pair of outer walls 45 are different from each other in which of the positive and negative sides in the D1 axis direction are adjacent to the groove 41. As a result, the pair of outer walls 45 may not be the same as described above near the bottom of the groove 41 due to different contact modes with the etching solution. Further, an error with no reproducibility (such as a chance error) is relatively likely to occur near the bottom of the groove 41. Further, when the influence of the transverse wall 49 appears on the base side of the outer wall 45 as described above, it is not always easy to clearly distinguish the portion caused by the influence of the transverse wall 49 and the outer wall 45. Therefore, in determining whether the shapes of the pair of outer walls 45 (thickness t1 at the same height) are the same, the shape on the root side may be ignored. For example, it may be determined whether the shapes of the pair of outer walls 45 are the same as each other based on the shape of the outer wall lower portion 45b from the middle to the upper side. Alternatively, for example, when the depth from the top of the outer wall 45 to the deepest part of the groove 41 is Dp0, the pair of outer walls 45 is based on the shape in the range from the top of the outer wall 45 to about 3/4 of Dp0. It may be determined whether or not the shapes are the same.

  The problem of which range of the outer wall 45 is compared as described above may be considered as a problem of the definition of which position from the top to which the outer wall 45 is regarded as. That is, the outer wall 45 may be defined as the outer wall from the top of the outer wall 45 to the vicinity of the middle of the outer wall lower portion 45b, or from the top of the outer wall 45 to about 3/4 of Dp0. Depending on the shape (or residue) of the bottom of the groove 41, the bottom surface of the groove 41 may look like the skirt of the outer wall 45, and it may be difficult to specify the range of the outer wall 45. Such a definition is valid.

  Further, the same shape (thickness t1 at the same height) of the outer wall 45 here is an error that is not reproducible (such as a chance error) is ignored. The magnitude of the error varies depending on the dimensions of the outer wall 45 and the specific conditions of etching. As an example, when the thickness t1 at a position near the base of the outer wall 45 (for example, near the middle of the outer wall lower portion 45b) is 8 μm or more and 11 μm or less, the difference between the pair of outer walls 45 at the position is about 2 μm at maximum. May occur (such as when an error of +1 μm and −1 μm occurs with respect to the design value). Of course, this error can be reduced by performing etching with higher accuracy.

(Configuration of the inner wall)
The shape (including dimensions) of the transverse cross section of each middle wall 47 (the cross section perpendicular to the D2 axis shown in FIG. 5A) is, for example, substantially constant along its longitudinal direction (D2 axial direction). However, this is not the case depending on the influence of the transverse wall 49 on the etching of the middle wall 47. In the following description of the inner wall 47, the influence of the transverse wall 49 is ignored unless otherwise specified.

  The position of the top of the middle wall 47 is lower than the position of the top of the outer wall 45 (positioned on the bottom side of the groove 41 in the D3 axis direction). Unlike the top of the outer wall 45, the top of the middle wall 47 is not limited to a planar shape perpendicular to the D3 axis, and is composed of, for example, one or more crystal faces that appear by etching. The top of the middle wall 47 may be the highest position of the middle wall 47.

  Further, the inner wall 47 is thinner than the outer wall 45. Here, the thickness t1 of the outer wall 45 and the thickness t2 of the middle wall 47 (FIG. 5A) are not necessarily constant from the root to the top. Therefore, the inner wall 47 referred to here is thinner than the outer wall 45 when the thickness at the same height (same position in the D3 axis direction) is compared, generally from the root to the top of the inner wall 47. In other words, the thickness t2 of the middle wall 47 is thinner than the thickness t1 of the outer wall 45 over the most part.

  However, in the vicinity of the base of these walls, for example, as described for the shape of the pair of outer walls 45, a part of the bottom surface of the groove 41 looks like the inner wall 47 or the skirt of the outer wall 45, and the inner wall 47 or the boundary of the outer wall 45 is difficult to specify, or the influence of non-reproducible errors is large. In addition, the influence of the transverse wall 49 appears at the root of the middle wall 47 on the positive side in the D1 axial direction, while the outer wall 45 on the positive side in the D1 axial direction of the pair of outer walls 45 has a root on the positive side in the D1 axial direction. The influence of the transverse wall 49 does not appear.

  Therefore, the thickness in the vicinity of such a root may be ignored. For example, it may be determined whether the middle wall 47 is thinner than the outer wall 45 based on the thickness from the middle of the outer wall lower portion 45b to the upper side. Or, for example, when the depth from the top of the middle wall 47 to the deepest part of the groove 41 is Dp2, the middle wall is based on the thickness in the range from the top of the middle wall 47 to about 3/4 of Dp2. It may be determined whether 47 is thinner than the outer wall 45.

  The problem of comparing the range of the inner wall 47 and the outer wall 45 as described above is the definition of what position is regarded as the inner wall 47 (or outer wall 45) from the top, as in the comparison between the outer walls 45. You may think of it as a problem. For example, a range from the vicinity of the middle of the outer wall lower portion 45b to the upper side or from the top of the middle wall 47 to about 3/4 of Dp2 may be defined as the middle wall.

  As for the influence of the transverse wall 49, as in the comparison between the outer walls 45, the portion caused by the influence of the transverse wall 49 (for example, the crystal plane constituting the transverse wall 49) constitutes the middle wall 47 and the outer wall 45. You may think that it is not.

  The shape of the cross section of the middle wall 47 is, for example, a shape in which the wall surfaces on both sides in the D1 axis direction of the outer wall 45 are close to each other except near the top. That is, when the wall surface on the D1 axis direction positive side of the middle wall 47 is translated in the D1 axis direction, it substantially coincides with a part of the wall surface on the D1 axis direction positive side of the outer wall 45, and on the negative side in the D1 axis direction. The same is true for the walls. Further, from another viewpoint, the inner wall 47 has the same crystal plane as the wall surface of the outer wall 45 (however, the wall surface in the range of the height of the top of the inner wall 47) as the wall surface. Yes. And while having the wall surface of the same shape, the middle wall 47 is shorter than the outer wall 45 in the distance (thickness) between the wall surfaces at the same height.

  However, in the vicinity of the bottom of the groove 41, as described in the comparison of the thicknesses of the middle wall 47 and the outer wall 45, for example, the influence of the transverse wall 49 is likely to appear or there is an error that is not reproducible (accidental error). ) Is relatively easy to occur. Therefore, similarly to the comparison of the thickness, it is determined whether the wall shape is the same between the middle wall 47 and the outer wall 45 by excluding the influence of the transverse wall 49, or from the middle of the middle of the outer wall lower part 45b. It is determined whether the wall shape is the same between the middle wall 47 and the outer wall 45 based on the upper wall surface shape or the wall surface shape in the range from the top of the middle wall 47 to about 3/4 of Dp2. Or defining a portion of such a range as an inner wall and an outer wall and comparing them.

(Configuration of crossing wall)
As shown in FIGS. 4A and 4B, the transverse wall 49 extends from one of the outer wall 45 and the middle wall 47 to the other in a plan view, for example, and the tip thereof is on the other side. Not reached. Therefore, the plurality of recesses 51 arranged along the vibrating arm 23 (D2 axis) and constituting the groove 41 are connected to each other.

  By doing so, for example, in the first excitation electrode 17 </ b> V, it is easy to ensure conduction between portions disposed in the recess 51. However, the transverse wall 49 may extend from one of the outer wall 45 and the middle wall 47 to the other.

  Further, the transverse wall 49 is provided so as to be inclined with respect to a direction (D1 axis direction) perpendicular to the vibrating arm 23 in a plan view in consideration of, for example, anisotropy (residue direction) with respect to crystal etching. It has been. However, the transverse wall 49 may be orthogonal to the vibrating arm 23.

  Further, the front end of the cross wall 49 in a plan view (portion where the recesses 51 are connected) is the same side of the two grooves 41 with respect to the width direction of the groove 41 (D1 axial direction) (in the illustrated example, the D1 axial direction). On the positive side). That is, in the illustrated example, in the groove 41 on the negative side in the D1 axial direction of the two grooves 41, the transverse wall 49 extends from the outer wall 45 toward the middle wall 47, and the D1 axial direction of the two grooves 41 In the positive groove 41, the transverse wall 49 extends from the intermediate wall 47 toward the outer wall 45.

  By doing so, for example, as shown in FIG. 5B, the shape generated by the anisotropy of crystal etching on the inner wall of the groove 41 is substantially the same between the two grooves 41 even in the vicinity of the transverse wall 49. It can be. However, the transverse wall 49 may have tips opposite to each other in the D1 axis direction.

  The height (position in the D3 axis direction) of the top (highest position) of the transverse wall 49 is higher than the height of the top of the middle wall 47, for example. Further, the height of the top of the transverse wall 49 is equal to or lower than the height of the top of the outer wall 45, for example. In addition, when the height of the top part of the transverse wall 49 is equivalent to the height of the top part of the outer wall 45, the top surface is basically a planar shape perpendicular to the D3 axis. However, like the top surface of the outer wall 45, this is not the case when the area is small.

  The wall surface or the front end surface of the transverse wall 49 (the surface facing the wall surface of the intermediate wall 47) is basically constituted by a crystal plane, like the outer wall 45 and the wall surface of the intermediate wall 47. Note that, unlike the wall surfaces of the outer wall 45 and the intermediate wall 47, the front end surface of the transverse wall 49 is subjected to etching from the D2 axis direction, and therefore is not necessarily the same as the crystal plane that appears on the wall surfaces of the outer wall 45 and the intermediate wall 47. The crystal plane does not appear. That is, the shape of the front end surface of the transverse wall 49 is not necessarily the same as the shape of the wall surfaces of the outer wall 45 and the middle wall 47. In FIG. 5B, for convenience, the front end surface is shown as a vertical wall, ignoring the actual shape and dimensions of the front end surface of the transverse wall 49.

  The thickness t3 (FIG. 4B) of the transverse wall 49 not only varies depending on the height (position in the D3 axis direction), but also varies depending on the position in plan view (approximately the position in the D1 axis direction). Since a residue is generated at the corner formed by the outer wall 45 or the inner wall 47, it is difficult to simply compare with the outer wall 45 or the inner wall 47. If it is assumed that the diameter of the mask opening for etching is reflected in the wall thickness (ignoring systematic errors and accidental errors), the thickness t3 of the transverse wall 49 is, for example, the middle wall 47. The thickness t2 of the outer wall 45 is equal to or less than the thickness t1 of the outer wall 45.

(Groove structure)
As can be understood from the description of the various wall configurations, the shape (including dimensions) of the cross section of each groove 41 (the cross section perpendicular to the D2 axis shown in FIG. 5A) is the arrangement of the cross walls 49. Except for the position, for example, it is generally constant over the longitudinal direction (D2 axis direction). In the following description, the shape of the groove 41 may be described except for the position where the transverse wall 49 is disposed.

  5B illustrates the case where the depth Dp0 (FIG. 5A) of the deepest portion at the non-arranged position of the transverse wall 49 of the groove 41 is maintained even at the arrangement position of the transverse wall 49. doing. However, as described above, the transverse wall 49 may extend over the outer wall 45 and the intermediate wall 47 (the groove 41 may be interrupted). Further, when the transverse wall 49 extends from one of the middle wall 47 and the outer wall 45 and does not reach the other, and the groove 41 is formed at the position where the transverse wall 49 is disposed (the middle wall 47 at the position where the transverse wall 49 is disposed). Even when a lower portion is formed), the deepest depth at the non-arranged position of the transverse wall 49 may not be maintained at the arranged position of the transverse wall 49.

  As can be understood from the description of the shapes of the pair of outer walls 45 and the middle wall 47, each groove 41 (except on the middle wall 47) is basically constituted by a crystal plane. Further, the shapes (including dimensions) of the two grooves 41 are basically the same even when the anisotropy with respect to the etching of the crystal is taken into consideration. In determining whether or not the shapes of the two grooves 41 are the same, an error having no reproducibility may be ignored as in the case of the outer wall 45 and the inner wall 47. In addition, as with the outer wall 45 and the middle wall 47, the determination as to whether or not they are the same is in the range of about 3/4 of the depth Dp0 from the top of the outer wall 45, and about 3/4 of the depth Dp2 from the top of the middle wall 47. Or a range above the middle of the outer wall lower portion 45b. The determination of whether or not they are the same may be made by excluding the influence of the crossing wall 49. In the present embodiment, as shown in FIG. 5B, the shapes of the two grooves 41 are the same even if the influence of the transverse wall 49 is taken into consideration.

(Middle layer structure)
The intermediate layer 43 is, for example, an area between the upper surface groove 41 (deepest part) and the lower surface groove 41 (deepest part) of the vibrating arm 23 and may be defined in a flat plate shape. In addition, the intermediate layer 43 has, for example, a thickness (upper surface) of the intermediate layer 43 toward the one side of the D1 axis at the end on the one side in the D1 axis direction (in the illustrated example, the negative side in the D1 axis direction). The distance from the surface of the intermediate layer 43 provided with the outer wall 45 on the side to the surface of the intermediate layer 45 provided with the outer wall 45 on the lower surface side is reduced. However, the position of the groove 41 on the upper surface (near the deepest part) and the position of the groove 41 (near the deepest part) on the lower surface in the D1 axis direction are shifted from each other, so In other words, the intermediate layer 43 defined as described above may not be formed.

(Relationship between the shape of a pair of vibrating arms)
As described above, the schematic shape of the vibrating arms 23 not considering the anisotropy of the crystal etching may be the same between the pair of vibrating arms 23 or may be plane symmetric. On the other hand, as can be understood from the description of the shape of the wall surfaces of the outer wall 45 and the inner wall 47, the shape (the type (angle) and number of crystal planes constituting the wall surface) caused by the anisotropy of crystal etching is one pair. The vibrating arms 23 are not in a plane-symmetrical shape but coincide with each other when translated.

(Top and bottom shape)
In the vibrating arm 23, the shape of the upper surface and the shape of the lower surface are formed by the same technique (etching) based on the same idea, but the crystal planes appearing by etching because the directions with respect to the crystal orientation are different from each other. Or, the orientation of the crystal plane with respect to the D1 axis to the D3 axis does not necessarily match. However, when the X axis is the D1 axis, the Y ′ axis is the D2 axis, the Z ′ axis is the D3 axis, and wet etching is performed from both sides of the D3 axis, the shape on the upper surface side and the shape on the lower surface side are approximately , The surface is symmetrical with respect to a plane orthogonal to the D3 axis.

(Example of dimensions of each part)
The dimensions of each part of the vibrating arm 23 described above may be appropriately set from the viewpoint of obtaining a desired natural frequency or necessary strength and / or preventing the groove 41 from being a through hole by etching. Below, an example is shown. The example of the dimension shown below is a case where the crystal piece 15 is relatively small. Specifically, the thickness of the vibrating arm 23 (from the top of the outer wall 45 on the upper surface side to the top of the outer wall 45 on the lower surface side) Is a distance of 70 μm to 120 μm.

  The depth Dp0 of the deepest portion of the groove 41 is not less than 40 μm and not more than 60 μm. In addition, this dimension includes the thing in the aspect which mutually overlaps the position of both D3 axial direction, shifting the position of the groove | channel 41 of an upper surface and the groove | channel 41 of a lower surface in the D1 axis direction mutually. Moreover, the width | variety (D1 axial direction) of the groove | channel 41 is 12 micrometers or more and 18 micrometers or less, for example.

  The thickness t1 of the outer wall 45 is, for example, 7 μm or more and 11 μm or less near the middle of the outer wall lower part 45b, 2 μm or more and 5 μm or less near the middle of the outer wall upper part 45a, or 1 / th of the thickness near the middle of the outer wall lower part 45b. 4 or more and 1/2 or less.

  The thickness t2 of the middle wall 47 is, for example, 4 μm or more and 7 μm or less (where t2 <t1 at the same height) in the vicinity of the middle of the range corresponding to the outer wall lower portion 45b, or the thickness of the outer wall 45 at the same height. It is 1/4 or more and 3/4 or less of the length t1. The depth Dp1 (FIG. 5A) from the top of the outer wall 45 to the top of the middle wall 47 is, for example, 5 μm or more and 50 μm or less (where Dp1 <Dp0). Alternatively, the depth Dp1 to the top of the middle wall 47 is 1/11 or more and 10/11 or less of the depth Dp0 of the deepest part of the groove 41.

  In the transverse wall 49, the distance from the inner wall of the groove 41 provided with the transverse wall 49 to the tip of the transverse wall 49 is, for example, 3 μm or more and 5 μm or less.

  The one end in the D1 axis direction of the outer wall 45 located on the one side in the D1 axis direction from the end of the one side of the intermediate layer 43 in the D1 axis direction (the negative side in the D1 axis direction in the illustrated example) The distance to the end on the side is, for example, 9 μm or more and 13 μm or less. The width of the outer wall upper part 45a (the length of the outer wall upper part 45a in the D1-axis direction) is not less than 2 μm and not more than 7 μm.

<Method for manufacturing vibrator>
(Outline of manufacturing method)
The manufacturing method of the vibrator 1 may be the same as the known manufacturing method of the vibrator, except for the details of the method of forming the crystal piece 15. For example, generally speaking, in the vibrator 1, the vibration element 3, the element mounting member 5, and the lid member 7 are manufactured in parallel, the vibration element 3 is mounted on the element mounting member 5, and then the lid member 7 is mounted on the element. It is produced by bonding to the member 5.

  The vibration element 3 is manufactured as follows, for example. First, a wafer from which a large number of vibration elements 3 are taken is cut out from the crystal. Next, the upper and lower surfaces (surfaces orthogonal to the D3 axis) of the wafer are etched through an etching mask to thereby obtain a crystal piece having a base 21, a vibrating arm 23, a support arm 25, and a protrusion 27. 15 is formed. Thereafter, a conductive layer is formed on the crystal piece 15 by sputtering or the like through a patterning mask, whereby the excitation electrode 17, the element terminal 19 and the wiring 33 are formed. The conductive layer may be formed in a wafer state or after singulation.

  The element mounting member 5 is produced as follows, for example. First, a plurality of ceramic green sheets constituting the substrate 9 are punched and applied with a conductive paste to be a conductive layer (for example, the pad 11 and the external terminal 13) or a via conductor. Next, a plurality of ceramic green sheets are laminated and fired. Thereby, the element mounting member 5 in which the conductor is disposed on the generally box-shaped insulator is manufactured.

  When the vibration element 3 and the element mounting member 5 are manufactured as described above, the bonding bumps 29 made of a molten conductive resin are supplied to the pads 11 of the element mounting member 5 by, for example, a dispenser. The vibration element 3 is placed thereon. Then, the bonding bumps 29 are heated and cured, and the pads 11 and the element terminals 19 are bonded by the bonding bumps 29.

  For example, the support bump 31 is formed by supplying a conductive adhesive or an insulating resin with a dispenser or the like after firing the element mounting member 5 and before mounting the vibration element 3 on the element mounting member 5. . The supporting bumps 31 may be supplied simultaneously with the bonding bumps 29 and may be heat-cured.

  The lid member 7 is formed, for example, by punching a sheet metal. After the vibration element 3 is mounted on the element mounting member 5, the lid member 7 is joined to the element mounting member 5 by seam welding or the like.

(Crystal etching)
FIGS. 6A to 7C are schematic views for explaining etching of the crystal piece 15. These drawings show a cross section corresponding to one vibrating arm 23, similarly to the cross sectional view shown in FIG. However, for convenience, the crystal plane and the like are more schematically shown than in FIG.

  As shown in FIG. 6A, first, an etching mask 103 is formed on the front and back (upper and lower surfaces) of a wafer 101 made of crystal. The method for forming the mask 103 may be the same as a known method. For example, the mask 103 is formed by forming a metal film on the entire front and back surfaces of the wafer 101, forming a mask made of a resist thereon by photolithography, and etching the metal film through the mask, It consists of a metal film and a resist layer. However, the mask 103 may be composed of only a metal film by removing the resist. Further, the metal film may be composed of one layer or may be composed of multiple layers.

  As understood from the D1 axis to the D3 axis, the upper and lower surfaces of the wafer 101 are surfaces that become the upper and lower surfaces of the crystal piece 15. The mask 103 has openings at positions where through holes or recesses are formed on the upper and lower surfaces of the crystal piece 15, that is, at positions where the wafer 101 is to be etched.

  Therefore, the mask 103 has substantially the same shape as the upper and lower surfaces of the crystal piece 15 (excluding the groove 41). That is, the mask 103 includes a base corresponding portion 105 (indicated by a two-dot chain line in FIG. 4A) that overlaps the region to be the base 21, a vibrating arm corresponding portion 107 that overlaps the region to be the vibrating arm 23, It has a support arm corresponding part (not shown) that overlaps the area that should become the support arm 25 and a protrusion corresponding part (not shown) that overlaps the area that should become the protrusion 27.

  From another point of view, the mask 103 has an outer edge opening 109 (reference numeral FIG. 4A) that overlaps a region (a region to be etched) to be a void on the outer periphery of the crystal piece 15. The outer edge opening 109 includes, for example, a side opening 109 a that overlaps a region that is to be a space on the side of the vibrating arm 23.

  Further, the vibrating arm corresponding portion 107 has a groove opening 111 that overlaps a region to be the groove 41. From another point of view, the vibrating arm corresponding portion 107 includes an outer wall corresponding portion 113 that overlaps the region that should become the outer wall 45, an intermediate wall corresponding portion 115 that overlaps the region that should become the inner wall 47, and a region that should become the transverse wall 49. It has an overlapping transverse wall corresponding portion 117 (indicated by a two-dot chain line in FIG. 4B).

  As described above, the mask 103 is generally the same as the shape of the upper and lower surfaces of the crystal piece 15. For example, the above description regarding the schematic shape of the base portion 21, the vibrating arm 23, etc. in plan view is generally the base portion. This applies to the shape of the corresponding portion 105, the vibrating arm corresponding portion 107, etc., and will not be repeated here.

  Here, in the manufacturing method of the crystal blank 15, the width (D1 axis direction) of the inner wall corresponding portion 115 is relatively smaller than the width of the outer wall corresponding portion 113 and the width of the transverse wall corresponding portion 117. Is one of the features.

  As shown in FIG. 6B, after the mask 103 is formed, the wafer 101 is etched (for example, wet etching) through the mask 103. As the etching progresses, for example, the first crystal plane 121A and the second crystal plane 121B appear due to the anisotropy of the crystal etching. In addition, although it demonstrated with the simple shape for convenience, in reality, three or more crystal planes facing in an appropriate direction may appear.

  As shown in this figure, in the initial stage of etching, for example, in a cross-sectional view, the concave portion is formed in a trapezoidal shape with the crystal plane 121 as a leg. As a result, the upper and lower surface side portions of the void in the outer periphery of the crystal piece 15 and the opening side portion of the groove 41 are formed. That is, top side portions such as the outer wall 45, the middle wall 47, and the transverse wall 49 are formed using the crystal plane 121 as a wall surface. The etching rate differs depending on the axial direction of the crystal axis. When the etching rate of the outer edge opening 109 (side opening 109a) and the etching rate of the groove opening 111 are compared, the outer edge opening 109 (side opening) is compared. 109a) has a higher etching rate.

  As shown in FIG. 7A, when the etching further proceeds, the etching speed of the outer edge opening 109 (side opening 109a) is faster than the etching speed of the groove opening 111. When is formed, a recess is formed immediately below the groove opening 111. As a result, the base 21, the vibrating arm 23, the support arm 25, the outer edges of the protrusion 27, and the schematic shape of the groove 41 are formed.

  As shown in FIG. 7B, when the etching further proceeds, the etching also proceeds around the opening of the mask 103. For example, the crystal plane 121 that constitutes the wall surfaces of the outer wall 45 and the inner wall 47 moves inward from the edge with respect to the outer wall corresponding portion 113 and the inner wall corresponding portion 115. In addition, so-called under-etching may occur. And the area of the top surface of the part which becomes the outer wall 45 and the middle wall 47 gradually decreases. Such etching with a small top surface area may occur slightly in the process from FIG. 6A to FIG. 7A.

  Here, the inner wall corresponding portion 115 is narrower than the outer wall corresponding portion 113. Therefore, when etching is performed so that the area of the top surface is reduced, the top surface in contact with the mask 103 remains immediately below the outer wall corresponding portion 113, and the mask 103 immediately below the middle wall corresponding portion 115 remains. The contacted top surface disappears. That is, the position of the top portion of the portion that becomes the middle wall 47 is lower than the top portion of the portion that becomes the outer wall 45. Further, when a gap is formed between the portion that becomes the middle wall 47 and the middle wall corresponding portion 115 in this way, the etching solution enters the gap, and the etching that lowers the portion that becomes the middle wall 47 easily proceeds. Become.

  As shown in FIG. 7C, when the etching further proceeds, the vibrating arm 23 having the outer wall 45 and the middle wall 47 lower than the outer wall 45 is formed.

  It has been described that the top surface of the inner wall 47 that contacts the mask 103 disappears, while the top surface of the outer wall 45 that contacts the mask 103 remains. However, the width of the transverse wall corresponding portion 117 also corresponds to the inner wall. By being wider than the width of the portion 115, the top surface in contact with the mask 103 tends to remain.

  As the diameter of the groove opening 111 is smaller, the possibility that the groove 41 becomes a through hole can be reduced. From another viewpoint, the smaller the diameter of the groove opening 111, the longer the etching time. Therefore, instead of forming one thick groove on the upper surface or the lower surface of one vibrating arm 23, the width of the entire groove is one thick groove by forming two or more thin grooves 41. The etching time can be lengthened while maintaining the same width as the above (while maintaining the thickness t1 of the outer wall 45 thin). By keeping the thickness t1 of the outer wall 45 thin, for example, the CI can be kept low. By extending the etching time, for example, the side surface of the vibrating arm 23 and the like can be sufficiently etched to reduce the residue.

  As long as the width of the middle wall corresponding portion 115 is smaller than the width of the outer wall corresponding portion 113, the top surface in contact with the mask 103 of the outer wall 45 disappears in the etching process, while the top surface in contact with the mask 103 of the outer wall 45 disappears. There is a remaining time. Moreover, such a period becomes long, so that the difference of the width | variety of the outer wall corresponding | compatible part 113 and the width | variety of the inner wall corresponding | compatible part 115 is large. Therefore, the dimension and etching time of the mask 103 for forming the middle wall 47 lower than the outer wall 45 can be easily found through experiments or the like, and may be adjusted as appropriate.

  An example of the dimension of the mask 103 is shown. The width of the outer wall corresponding portion 113 is 7 μm or more and 9 μm or less. The width of the middle wall corresponding part 115 is 4 μm or more and 6 μm or less, or is ¼ or more and 3/4 or less of the width of the outer wall corresponding part 113. The width of the transverse wall corresponding portion 117 is 6 μm or more and 8 μm or less. The width of the groove opening 111 is 8 μm or more and 11 μm or less. In such dimensions, for example, when a chemical solution and equipment used for wet etching of a quartz wafer are used, the outer wall 45 and the inner wall lower than the outer wall 45 are etched by approximately 5 to 10 hours. 47 and a transverse wall 49 which is higher than the middle wall 47 and has a height equal to or lower than the outer wall 45 is formed.

  As described above, in the present embodiment, the crystal piece 15 has the vibrating arm 23 extending in the direction (D2 axis direction) intersecting the polarization direction (X axis direction, D1 axis direction). The vibrating arm 23 has a long predetermined surface (upper surface or lower surface) parallel to the D2 axis direction and along the X axis direction, and two or more in the width direction (D1 axis direction) of the predetermined surface (this embodiment). The two recesses 51 (grooves 41) are provided, so that a pair of outer walls 45 positioned on both sides of the two or more recesses 51 and one or more (books) positioned between the two or more recesses 51 are provided. 1 in the embodiment). The middle wall 47 has a top portion located at a position lower than the top portions of the pair of outer walls 45 and is thinner than the pair of outer walls 45 at the same height.

  Therefore, for example, CI can be reduced. In addition, it has been confirmed by experiments of the present inventors that the CI is lowered by the above-described configuration (by making the inner wall 47 lower and thinner than the outer wall 45). There are two reasons why CI decreases.

  First, when the middle wall 47 is low and thin, a portion that becomes a bone located on the center side of the vibrating arm 23 becomes small. As a result, the vibrating arm 23 is likely to vibrate. From another viewpoint, the ratio of the stress or deformation generated in the outer wall 45 to the vibration of the vibrating arm 23 increases. On the other hand, in the outer wall 45, the first excitation electrode 17V and the second excitation electrode 17H are formed on both wall surfaces, and these excitation electrodes 17 face each other in the D1 axis direction. That is, the outer wall 45 has a large contribution ratio to the electric field that excites the vibrating arm 23 in the D1 axis direction, and a large contribution ratio to the extraction of charges generated by the vibration of the vibrating arm 23 in the D1 axis direction. For this reason, excitation and charge extraction can be performed efficiently, and the CI decreases.

  Second, when the middle wall 47 is low and thin, the opening side of the groove 41 is widened. As a result, the conductive material easily enters the groove 41 when the conductive material is disposed on the upper and lower surfaces of the vibrating arm 23 by sputtering or the like so as to form the first excitation electrode 17V. That is, the first excitation electrode 17 </ b> V is formed up to the deep position of the groove 41. As a result, the opposing area of the first excitation electrode 17V and the second excitation electrode 17H across the outer wall 45 also increases. Therefore, the electric field vector formed by these excitation electrodes 17 has a larger component parallel to the D1 axis, and the vibration of the vibrating arm 23 is increased. In addition, the amount of charge taken out from the outer wall 45 also increases. For this reason, CI decreases.

  Further, in the present embodiment, the pair of outer walls 45 have the same top portion at the same height and the same thickness at the same height.

  Accordingly, the rigidity, piezoelectric effect, and inverse piezoelectric effect of the pair of outer walls 45 in the D1 axis direction are likely to be equal. As a result, the possibility of unintended vibration bias or spurious is reduced, and the characteristics of the vibrator 1 are improved.

  In the present embodiment, the vibrating arm 23 includes a plurality of sets of two or more (two in the present embodiment) recesses 51 in the extending direction of the vibrating arm 23 (D2 axis direction). One or more transverse walls 49 are located between the two or more recesses 51. The top of the transverse wall 49 is higher than the top of the middle wall 47.

  Here, for example, when paying attention to the manufacturing process, if the top side of the portion that becomes the inner wall 47 is etched due to the narrow inner wall corresponding portion 115, the etching of the portion that becomes the groove 41 proceeds excessively, and the groove 41 becomes a through hole. There is a risk of becoming. However, since the crossing wall corresponding part 117 is thicker than the middle wall corresponding part 115 and the top side of the part that becomes the crossing wall 49 is more likely to remain than the top side of the part that becomes the middle wall 47, the groove 41 becomes a through hole. The risk of being lost is reduced. Since the transverse wall 49 is a wall that intersects with the extending direction of the vibrating arm 23, the influence on the bending rigidity of the vibrating arm 23 is extremely low compared to the middle wall 47 that extends in the extending direction of the vibrating arm 23. Therefore, there is little risk of increasing CI due to the provision of the transverse wall 49.

  In the present embodiment, the vibration element 3 includes two or more (two in the present embodiment) recesses 51 (grooves 41) on the crystal piece 15 as described above and the upper surface or the lower surface of the vibration arm 23. The first excitation electrode 17V and the pair of side surfaces of the vibrating arm 23 that are located on both sides in the width direction (D1-axis direction) with respect to the upper surface or the lower surface and intersect the upper surface or the lower surface, respectively. A second excitation electrode 17H. Therefore, the first excitation electrode 17V described above is arranged up to the bottom of the groove 41, and the effect of reducing the CI is exhibited.

  In the present embodiment, the piezoelectric device (the crystal device, the crystal resonator 1) has the mounting base (the element mounting member 5) on which the vibration element 3 as described above is mounted, so that the CI decreases. The effect to do.

  Further, in the present embodiment, the method for manufacturing the crystal piece 15 includes masking the main surface (upper surface and / or lower surface) along the polarization direction (X-axis direction, D1-axis direction) of the piezoelectric wafer (wafer 101 made of crystal). A mask forming process for forming 103 (FIG. 6A) and an etching process for etching the wafer 101 through the mask 103 (FIGS. 6B to 7C). The mask 103 has a long vibrating arm corresponding portion 107. The vibrating arm corresponding portion 107 is provided with two or more (two in this embodiment) openings (groove openings 111) in the width direction (D1-axis direction) of the vibrating arm corresponding portion 107, thereby providing two or more. A pair of outer wall corresponding portions 113 located on both sides of the groove opening 111 and one or more (one in this embodiment) middle wall corresponding portions 115 located between the two or more groove openings 111. doing. The middle wall corresponding portion 115 is thinner than the pair of outer wall corresponding portions 113. In the etching process, both the etching outside the vibrating arm corresponding portion 107 (immediately below the side opening 109a) and the etching at the two or more groove openings 111 are started (FIG. 6B), and the main surface of the wafer 101 is used. Etching is continued until the region in contact with the middle wall corresponding portion 115 is etched from one edge of the middle wall corresponding portion 115 to the other edge (FIG. 7C).

  Therefore, for example, the crystal piece 15 capable of lowering CI by the inner wall 47 being lower than the outer wall 45 and being thin can be formed by one etching due to the etching anisotropy in the crystal orientation of the crystal. . As a result, the manufacturing process is simplified, and cost reduction is expected. In addition, for example, the etching time through the groove opening 111 and the etching time through the outer edge opening 109 are the same, and therefore, the pair of outer walls 45 are arranged on the same side in the D1 axis direction. The etching time becomes the same. As a result, the pair of outer walls 45 are likely to have the same shape (including dimensions). And the preferable effect mentioned above by the shape being the same between a pair of outer walls 45 is show | played.

  In the above embodiment, the crystal piece 15 is an example of a piezoelectric piece, the crystal resonator element 3 is an example of a piezoelectric resonator element, the crystal resonator 1 is an example of a piezoelectric resonator device, and the D1 axis direction is polarized. It is an example of a direction, the vibrating arm 23 is an example of an arm part, the upper surface and the lower surface of the vibrating arm 23 are examples of predetermined surfaces of the arm part, and the first excitation electrode 17V is an example of a first electrode, The second excitation electrode 17H is an example of a second electrode, the element mounting member 5 is an example of a mounting substrate, the wafer 101 is an example of a piezoelectric wafer, and the vibrating arm corresponding part 107 is an example of an arm corresponding part. .

  The present invention is not limited to the above-described embodiment or modification, and may be implemented in various aspects.

  The piezoelectric piece, the piezoelectric vibrating element, and the piezoelectric vibrating device are not limited to the quartz piece, the quartz vibrating element, and the quartz vibrating device. For example, the piezoelectric piece may be made of single crystal or polycrystalline ceramic instead of quartz.

  Further, the piezoelectric piece, the piezoelectric vibration element, and the piezoelectric vibration device are not limited to those for generating an oscillation signal. For example, the piezoelectric vibration device may be a piezoelectric vibration type gyro sensor. Further, the piezoelectric device that generates the oscillation signal is not limited to the vibrator. For example, the piezoelectric device may be an oscillator including a portion that becomes a vibrator and an oscillation circuit. Moreover, the vibrator may include other electronic components such as a thermistor in addition to the vibration element.

  The arm portion to which the present invention is applied is not limited to the vibrating arm excited by the excitation electrode. For example, in the case where the piezoelectric vibrating device is a gyro sensor having a vibrating arm excited by an excitation electrode and a detection arm that vibrates along with the vibration of the vibrating arm and is used for taking out an electric charge (signal). The present invention may be applied to the detection arm. In another aspect, the first electrode and the second electrode provided on the arm portion are not limited to the excitation electrode, and may be a detection electrode provided on the detection arm in order to extract electric charges.

  The piezoelectric piece is not limited to a shape (for example, a tuning fork type) having a base portion and a pair of arm portions extending in parallel with each other from the base portion. For example, the piezoelectric piece may have only one arm part, or may have three or more arm parts extending in parallel with each other, or a plurality of arm parts extending in opposite directions to each other. You may have.

  Further, in the piezoelectric piece, the support arm, the protruding portion, and the like are not essential requirements. For example, the base may be directly fixed to the element mounting member or the like. The mounting structure of the piezoelectric vibration element and the structure of the package (element mounting member and lid member) of the piezoelectric device may be various known ones.

  As is clear from the fact that the piezoelectric body may be polycrystalline as described above, the polarization direction is not limited to the direction of the electric axis (X axis), for example, a direction appropriately polarized in the polycrystalline body. It may be.

  The arm part should just extend in the direction which cross | intersects with a polarization direction, and does not necessarily need to be orthogonal to a polarization direction. What is necessary is just to be able to vibrate so that an arm part may bend in the width direction by the voltage application to the width direction of an arm part. For example, in the embodiment, the D1 axis orthogonal to the arm portion may have a slight inclination (for example, less than 15 °) around the Y axis or the Z axis with respect to the X axis (electric axis). Further, for example, in a gyro sensor, a crystal piece having three arm portions provided corresponding to three electric axes extending in different directions at intervals of 120 ° around the optical axis is known. Like a crystal piece, the arm portion may intersect with any electrical axis (polarization direction).

  As will be understood from the above, the predetermined surface (upper surface or lower surface) on which the outer wall and the inner wall are formed only needs to be substantially along the polarization direction (electric axis) and does not necessarily have to be parallel. For example, in the embodiment, the D3 axis orthogonal to the predetermined plane may have a slight inclination (for example, less than 15 °) around the Y axis with respect to the X axis (electrical axis).

  Further, as is clear from the fact that the piezoelectric body may be polycrystalline, the relationship between the direction other than the polarization direction (for example, the mechanical axis and optical axis of the single crystal) and the direction of the arm portion may be appropriately set. . For example, in the embodiment, the case where the mechanical axis and the arm portion are generally along (inclination within 5 °) is exemplified, but both may intersect each other at an angle larger than that.

  In each vibrating arm, the grooves (inner wall and outer wall) may not be formed on both the upper surface and the lower surface, and may be provided only on one of these surfaces. Further, the number of grooves (recesses) on the upper surface or lower surface of one vibrating arm is not limited to two, and may be three or more. Etching the wafer may be performed from one side instead of from both sides.

  Piezoelectric pieces whose inner wall is lower than the outer wall and thin can make it possible to form both the outer edge and the groove of the piezoelectric piece by one etching, and thus make the pair of outer walls have the same shape. Is possible. However, the piezoelectric piece may be formed by etching twice as disclosed in Patent Document 1.

  DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator (piezoelectric device), 3 ... Quartz vibration element (piezoelectric vibration element), 15 ... Crystal piece (piezoelectric piece), 21 ... Base, 23 ... Vibrating arm, 41 ... Groove (concave part), 45 ... Outer wall, 47 ... Middle wall, 51 ... Recess.

Claims (6)

Having an arm portion extending in a direction crossing the polarization direction;
The arm portion has a long predetermined surface parallel to the direction in which the arm portion extends and along the polarization direction, and two or more concave portions are provided in the width direction of the predetermined surface. A pair of outer walls positioned on both sides of the two or more recesses, and one or more inner walls positioned between the two or more recesses,
The piezoelectric piece is located at a position where the top of the middle wall is lower than the top of each of the pair of outer walls and is thinner than each of the pair of outer walls at the same height. 2. The piezoelectric piece according to claim 1, wherein the pair of outer walls have the same height at the top and the same thickness at the same height. The arm portion has one or more transverse walls positioned between the two or more recesses of the plurality of sets by providing the two or more recesses in the extending direction.
The piezoelectric piece according to claim 1, wherein a top portion of the transverse wall is at a position higher than a top portion of the middle wall. The piezoelectric piece according to any one of claims 1 to 3,
A first electrode disposed over the two or more recesses on the predetermined surface;
A second electrode disposed on each of the pair of side surfaces that is located on both sides in the width direction of the arm portion and intersects the predetermined surface;
A piezoelectric vibration element having A piezoelectric vibration element according to claim 4,
A mounting substrate on which the piezoelectric vibration element is mounted;
A piezoelectric vibration device having: A mask forming step of forming a mask on the principal surface along the polarization direction of the piezoelectric wafer;
An etching step of etching the piezoelectric wafer through the mask;
Have
The mask has a long arm corresponding portion,
The arm portion corresponding portion is provided with two or more openings in the width direction of the arm portion corresponding portion, so that a pair of outer wall corresponding portions located on both sides of the two or more openings and the two or more openings. And one or more middle wall corresponding portions located between the openings,
The middle wall corresponding part is thinner than the pair of outer wall corresponding parts,
In the etching step, both the etching outside the arm corresponding portion and the etching in the two or more openings are started, and the region of the main surface of the piezoelectric wafer that is in contact with the middle wall corresponding portion is Etching is continued until etching is performed from one edge of the middle wall corresponding part to the other edge. Piezoelectric piece manufacturing method.

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