JP6060026B2 - Intermediate product of piezoelectric element and manufacturing method thereof - Google Patents

Description

  The present invention relates to an intermediate product of a piezoelectric element such as a tuning fork type bending vibrator or a thickness shear vibrator, and a method for manufacturing the same.

  The intermediate product of the piezoelectric element is composed of, for example, a plurality of piezoelectric elements and a frame processed by wet etching from a single quartz wafer, and is subject to commercial transactions independently in this state (see, for example, Patent Document 1). Hereinafter, an example of the intermediate product of the piezoelectric element will be described as related technology.

  FIG. 4 is a plan view showing an intermediate product of related technology. Hereinafter, description will be given based on this drawing.

  The X axis, Y ′ axis, and Z ′ axis in the figure are crystal axes of the crystal wafer. The intermediate product 50 of the related technology includes a plurality of piezoelectric elements 60 and a frame 70. The plurality of piezoelectric elements 60 are a tuning fork type having a base portion 61 and two vibrating arm portions 62 and 63 extending from the base portion 61 in the same direction. An electrode film (not shown) is formed on the piezoelectric element 60, and grooves are formed on the vibrating arm portions 62 and 63 as necessary.

  The frame 70 includes a crosspiece 71 that connects the plurality of piezoelectric elements 60 so as to be aligned in a row, and an outer frame 72 that surrounds the plurality of piezoelectric elements 60 and the crosspiece 71 and connects the crosspiece 71. And. That is, the crosspiece 71 extends in one direction (X-axis direction), and connects the base portions 61 of the piezoelectric elements 60 so that the plurality of piezoelectric elements 60 are arranged in a line along the one direction. The extending direction (Y′-axis direction) of the vibrating arm portions 62 and 63 is a direction perpendicular to the one direction. The outer frame portion 72 extends in a direction (Y′-axis direction) perpendicular to one direction (X-axis direction), and connects both ends of the crosspiece 71.

  Further, the connection portion 73 between the crosspiece 71 and the outer frame portion 72 has a shape cut into a wedge shape having a vertex 74. A connection portion 75 between each piezoelectric element 60 and the crosspiece 71 is a shape cut into an isosceles triangle shape having a vertex 76.

  A general manufacturing method of the intermediate product 50 is as follows. First, a mask made of chromium or the like is formed on the front and back of a single quartz wafer. Subsequently, wet etching is performed on the quartz wafer on which the mask is formed using hydrofluoric acid or the like. At this time, the portion of the quartz not covered with the mask is eroded from the front and back by the etching solution and finally penetrates. Finally, an electrode film is formed on the remaining quartz because it is covered with the mask, thereby completing the plurality of piezoelectric elements 60 and the frame 70.

  The intermediate product 50 is used in this state for electrical inspection and package mounting of the piezoelectric element 60. That is, each of the plurality of piezoelectric elements 60 is separated from the frame 70 through electrical inspection and mounted on the package.

JP 2003-198299 A (FIG. 7 etc.)

  FIG. 5 is an enlarged plan view of a part of FIG. Hereinafter, problems of related art will be described with reference to this drawing.

  In this state, the intermediate product 50 is used for electrode film formation, electrical inspection, package mounting, transfer, and the like. At this time, various stresses are generated in the intermediate product 50 due to the pressure of the etching solution and the cleaning solution during the manufacturing process, the impact during transportation, and the like. On the other hand, since the connection portion 73 between the crosspiece 71 and the outer frame portion 72 is a wedge-shaped shape having a vertex 74, stress tends to concentrate on the vertex 74. For this reason, the stress is concentrated on the connection portion 73 and the crack 51 may be generated there.

  One end of the crosspiece 71 where the crack 51 is generated is not fixed to the outer frame 72. As a result, the piezoelectric element 60 connected to the crosspiece 71 in which the crack 51 is generated becomes misaligned in the electrode forming process, the inspection process, the mounting process, and the like, and all of the one row must be discarded. It was.

  In addition, although the frequency of connection portions 75 between the piezoelectric elements 60 and the crosspieces 71 is less than that of the connection points 73 between the crosspieces 71 and the outer frame portion 72, the same problem occurs due to the shape thereof. It was. That is, since the connection portion 75 has a shape cut out in an isosceles triangle shape having the vertex 76, stress is likely to concentrate on the vertex 76. Therefore, cracks may occur in the crosspiece 71 starting from the vertex 76.

  Accordingly, an object of the present invention is to provide an intermediate product of a piezoelectric element that can improve the yield by suppressing the occurrence of cracks at a connection portion between the crosspiece and the outer frame.

The intermediate product of the piezoelectric element according to the present invention is
An intermediate product of a piezoelectric element composed of a plurality of piezoelectric elements and a frame,
The frame is
A crosspiece connecting the plurality of piezoelectric elements so as to be arranged in a row in a state of being separated from each other;
An outer frame portion that surrounds the plurality of piezoelectric elements and the crosspieces and connects the crosspieces;
A notch portion formed at a connecting portion between the crosspiece portion and the outer frame portion, and having a shape cut out by a curve that protrudes from the crosspiece portion side to the outer frame portion side;
It is provided with.

The manufacturing method according to the present invention includes:
A method for producing an intermediate product of a piezoelectric element according to the present invention, comprising:
Forming a mask having resistance to wet etching in the region to be the piezoelectric element, the crosspiece and the outer frame on the quartz wafer, and not forming the mask in the region to be the notch on the quartz wafer; ,
Forming the plurality of piezoelectric elements and the frame by performing the wet etching on the crystal wafer on which the mask is formed;
It is characterized by including.

  According to the present invention, the notch portion formed in the shape of a curve that is convex from the beam portion side to the outer frame portion side is formed at the connection portion between the beam portion and the outer frame portion. Since the stress generated at the notch can be dispersed by the notch, it is possible to suppress the occurrence of cracks at the connecting portion between the crosspiece and the outer frame, thereby improving the yield.

3 is a plan view showing an intermediate product according to Embodiment 1. FIG. FIGS. 2A and 2B are cross-sectional views illustrating a manufacturing process taken along line II-II in FIG. 1, in which FIG. 2 [1] is before wet etching, FIG. 2 [2] is during wet etching, and FIG. 6 is a plan view showing an intermediate product according to Embodiment 2. FIG. It is a top view which shows the intermediate product of related technology. It is the top view which expanded a part of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. In addition, since the shape drawn in drawing is drawn so that those skilled in the art can understand easily, it does not necessarily correspond with an actual dimension and ratio.

  FIG. 1 is a plan view showing an intermediate product according to the first embodiment. Hereinafter, description will be given based on this drawing.

  The X axis, Y ′ axis, and Z ′ axis in the figure are crystal axes of the crystal wafer. Quartz crystal is composed of a trigonal single crystal composed of silicon and oxygen. The growth axis (optical axis) is the Z axis, and the axis connecting the ridge line perpendicular to this is the X axis (electric axis), orthogonal to this. This axis is expressed as the Y axis (machine axis). The Y ′ axis and the Z ′ axis indicate that the Y axis and the Z axis are rotated by a certain angle around the X axis.

  The intermediate product 10 according to the first embodiment includes a plurality of piezoelectric elements 60 and a frame 20.

  Similar to the related art described above, the piezoelectric element 60 is a tuning fork type having a base portion 61 and two vibrating arm portions 62 and 63 extending from the base portion 61 in the same direction. An electrode film (not shown) is formed on the piezoelectric element 60, and grooves are formed on the vibrating arm portions 62 and 63 as necessary.

  The frame 20 includes a crosspiece 21 that connects the plurality of piezoelectric elements 60 so as to be aligned in a row, and an outer frame 22 that surrounds the plurality of piezoelectric elements 60 and the crosspiece 21 and connects the crosspiece 21. And a notch portion 23 formed at a connection portion 24 between the crosspiece portion 21 and the outer frame portion 22. The cutout portion 23 has a shape (arc shape in the first embodiment) cut out by a curve that protrudes from the crosspiece 21 side to the outer frame portion 22 side. Further, the connection portion 25 between each piezoelectric element 60 and the crosspiece 21 has a shape cut out by a curved line that protrudes from the side between the adjacent piezoelectric elements 60 toward the crosspiece 21 (arc shape in the first embodiment). . The curvature of the notch 23 is equal to the connection portion 25 and the curvature.

  The crosspiece 21 extends in one direction (X-axis direction), and connects the base portions 61 of the piezoelectric elements 60 so that the plurality of piezoelectric elements 60 are arranged in a line along the one direction. The extending direction (Y′-axis direction) of the vibrating arm portions 62 and 63 is a direction perpendicular to the one direction. The outer frame portion 22 extends in a direction (Y′-axis direction) perpendicular to one direction (X-axis direction), and connects both ends of the crosspiece portion 21.

  As long as the shape of the cut-out portion 23 is a shape cut out by a curve that protrudes from the crosspiece 21 side to the outer frame portion 22 side, in addition to the arc shape, an elliptical arc shape, a parabolic shape, a hyperbolic shape, and a quadratic curve shape Any shape is acceptable. The term “curve” here refers mathematically to a “smooth curve” that does not have a cusp (vertex), in other words, a curve that can be differentiated at any point on the curve, ie, “differentiable”. "Curve". The shape of the connection portion 25 is the same as the shape of the notch 23.

  Next, the operation and effect of the intermediate product 10 of the first embodiment will be described.

  (1) The notch portion 23 is formed at a connection portion 24 between the crosspiece portion 21 and the outer frame portion 22, and has a shape cut out by a curve that protrudes from the crosspiece portion 21 side to the outer frame portion 22 side. As a result, the notch 23 does not have a vertex at which stress is likely to concentrate, so that the stress generated at the connection portion 24 between the crosspiece 21 and the outer frame 22 is evenly distributed throughout the notch 23. Accordingly, since the occurrence of cracks due to stress can be suppressed at the connection portion 24 between the crosspiece portion 21 and the outer frame portion 22, the yield can be improved.

  (2) When the connection portion 25 between each piezoelectric element 60 and the crosspiece portion 21 has a shape cut out by a curve that protrudes from the side between the adjacent piezoelectric elements 60 to the crosspiece portion 21 side, the connection portion 25 occurs. Since the stress can be dispersed, the generation of cracks due to the stress can be suppressed at the connection portion 25, so that the yield can be improved.

  (3) Although the shape cut out by the curve can relieve stress significantly compared with the related art, the stress tends to concentrate on a portion of the curve having a large curvature (small radius of curvature). On the other hand, when the shape cut out by the curve is an arc shape, the curvature of any fine curve constituting the arc can be equalized, so that the portion where the stress is likely to be concentrated can be further reduced. Generation of cracks can be further suppressed.

  (4) The etching rates in the X-axis direction, the Y-axis direction, and the Z-axis direction are in the order of Z> X> Y. Therefore, in the piezoelectric element 60, a residue is generated in the crystal after wet etching. The residue is, for example, a protrusion that is generated on the left side in FIG. 1 of the base portion 61 and the vibrating arm portions 62 and 63 and is convex in the + X axis direction. In the first embodiment, by forming the notch portion 23, a space around the connection portion 24 between the crosspiece portion 21 and the outer frame portion 22 becomes wider than that in the related art. Therefore, according to the first embodiment, the etching solution easily flows at the connection portion 24 between the crosspiece 21 and the outer frame portion 22, so that the generation of residues can be suppressed.

  2 is a cross-sectional view showing the manufacturing process along the line II-II in FIG. 1. FIG. 2 [1] is before wet etching, FIG. 2 [2] is during wet etching, and FIG. 2 [3] is after wet etching. It is. Hereinafter, based on FIG.1 and FIG.2, the manufacturing method of this Embodiment 1 is demonstrated.

  The manufacturing method of Embodiment 1 includes the following steps. The mask 12 having resistance to wet etching is formed on the crystal wafer 11 in the region 60a to be the piezoelectric element 60, the region 22a to be the outer frame portion 22, and the region (not shown) to be the crosspiece portion 21, and the crystal wafer 11 is not formed in the region 23a to be the notch 23 on the top. A step of forming the plurality of piezoelectric elements 60 and the frame 20 by performing wet etching on the crystal wafer 11 on which the mask 12 is formed. In FIG. 2, a region 61 a that becomes the base 61 is shown as a region 60 a that becomes the piezoelectric element 60.

  FIG. 2 [1] shows a state before wet etching, that is, immediately after the mask 12 is formed on the crystal wafer 11. The mask 12 is manufactured by the following process, for example. First, a corrosion-resistant film made of, for example, two layers of chromium and gold is formed on both surfaces of the quartz wafer 11 by, for example, sputtering. Subsequently, unnecessary portions of the corrosion resistant film are removed by photolithography and etching. As a result, the mask 12 that protects the piezoelectric element 60 and the regions 60 a and 20 a to be the frame 20 is created. The thickness of the quartz wafer 11 is, for example, 100 μm.

  FIG. 2 [2] shows a state during wet etching. In this step, the crystal wafer 11 on which the mask 12 is formed is immersed in the etching solution 13. The etching solution 13 is a strong acid composed of, for example, hydrofluoric acid and an aqueous ammonium fluoride solution. At this time, the etching solution 13 is circulated at a flow rate of 5 L / min, for example. During the wet etching, the portion of the quartz wafer 11 not covered with the mask 12 is eroded from the front and back by the etching solution 13 and finally penetrates.

  FIG. 2 [3] shows a state after wet etching. Thereafter, an electrode film (not shown) is formed on the remaining quartz wafer 11 because it has been covered with the mask 12, thereby completing the intermediate product 10 including the plurality of piezoelectric elements 60 and the frame 20. Each of the plurality of piezoelectric elements 60 is separated from the frame 20 through electrical inspection and mounted on a package.

  According to the manufacturing method of the first embodiment, by obtaining the intermediate product 10 of the first embodiment, the same operations and effects as the intermediate product 10 of the first embodiment are obtained, and the piezoelectric element 60 and the frame are provided. Since the notch 23 can be formed at the same time as 20, a new process for forming the notch 23 is not required.

  FIG. 3 is a plan view showing the intermediate product according to the second embodiment. Hereinafter, description will be given based on this drawing.

  The intermediate product 30 of the second embodiment is different from the first embodiment in the size of the notch 33. In the first embodiment shown in FIG. 1, the curvature of the cutout portion 23 is equal to the curvature of the connection portion 25, whereas in the second embodiment, the curvature of the cutout portion 33 is larger than the curvature of the connection portion 25. It is getting smaller.

  In general, the smaller the curvature of the notch 33 (the greater the radius of curvature), the less the stress is concentrated on the notch 33. Therefore, according to the second embodiment, it is possible to further suppress the occurrence of cracks due to stress at the connection portion 24 between the crosspiece 21 and the outer frame portion 22, thereby further improving yield. Other configurations, operations, and effects of the second embodiment are the same as those of the first embodiment.

  Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention. For example, although the tuning fork-type bending vibrator is taken up in the above embodiment, the present invention can be applied to other piezoelectric elements such as a thickness shear vibrator. Further, the present invention includes a combination of some or all of the configurations of the above-described embodiments as appropriate.

10, 30 Intermediate product 11 Crystal wafer 12 Mask 13 Etching solution 20 Frame 20a Frame region 21 Crosspiece portion 22 Outer frame portion 22a Outer frame portion region 23,33 Notch portion 23a Notch portion region 24, 25 Connection points

50 Intermediate Product 51 Crack 60 Piezoelectric Element 60a Piezoelectric Element Area 61 Base 61a Base Area 62, 63 Vibrating Arm 70 Frame 71 Crosspiece 72 Outer Frame 73 Connection Location 74 Vertex 75 Connection Location 76 Vertex

Claims (4)

An intermediate product of a piezoelectric element composed of a plurality of piezoelectric elements and a frame,
The frame is
A crosspiece connecting the plurality of piezoelectric elements so as to be arranged in a row in a state of being separated from each other;
An outer frame portion that surrounds the plurality of piezoelectric elements and the crosspieces and connects the crosspieces;
A notch portion formed at a connection portion between the crosspiece portion and the outer frame portion, and having a shape cut out by a curve protruding from the crosspiece portion side to which the piezoelectric element is connected to the outer frame portion side;
An intermediate product of a piezoelectric element characterized by comprising: The connection part between each piezoelectric element and the crosspiece has a shape cut out by a curve that protrudes from the side between adjacent piezoelectric elements to the crosspiece side.
An intermediate product of the piezoelectric element according to claim 1. The shape is arcuate,
An intermediate product of the piezoelectric element according to claim 1 or 2. A method for producing an intermediate product of a piezoelectric element according to any one of claims 1 to 3,
Forming a mask having resistance to wet etching in the region to be the piezoelectric element, the crosspiece and the outer frame on the quartz wafer, and not forming the mask in the region to be the notch on the quartz wafer; ,
Forming the plurality of piezoelectric elements and the frame by performing the wet etching on the crystal wafer on which the mask is formed;
A method for producing an intermediate product of a piezoelectric element, comprising:

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