JP7522678B2 - Tuning fork crystal unit - Google Patents

Description

The present invention relates to a tuning fork type quartz crystal resonator with a three-arm structure.

A tuning fork type crystal resonator that is advantageous for miniaturization is a so-called three-arm tuning fork type crystal resonator. An example of a tuning fork type crystal resonator with a three-arm structure is disclosed in, for example, Patent Document 1. FIG. 6 is a diagram for explaining the outline of this tuning fork type crystal resonator 10. In particular, FIG. 6(A) is a plan view showing this tuning fork type crystal resonator 10 in the form of a developed wiring diagram, and FIG. 6(B) is a cross-sectional view of the tuning fork type crystal resonator 10 taken along line P-P in FIG. 6(A). X, Y', and Z shown in FIG. 6 are the X-axis, Y'-axis, and Z-axis, which are the crystal axes of quartz. The Y'-axis indicates that the axis is shifted from the original Y-axis by a predetermined cutting angle determined by the design of the tuning fork.

This tuning fork type quartz crystal vibrator 10 comprises a base 11, a first vibrating arm 13a, a second vibrating arm 13b, a support arm 15, a groove 13c (shown only in Figure 6 (B)), and a first excitation electrode 17a and a second excitation electrode 17b.
The first vibrating arm 13a and the second vibrating arm 13b extend parallel to each other from the base 11. The support arm 15 extends between the first vibrating arm 13a and the second vibrating arm 13b from the base 11 in a state parallel to these vibrating arms 13a and 13b. The grooves 13c are provided to a predetermined depth on both the front and back sides of each of the first vibrating arm 13a and the second vibrating arm 13b. The grooves 13c are for efficiently applying the electric field of the drive signal to the vibrating arms 13a and 13b.

The first excitation electrode 17a and the second excitation electrode 17b are routed in a predetermined relationship on a total of eight faces of each vibrating arm 13a, 13ba. Furthermore, a portion of the first excitation electrode 17a and the second excitation electrode 17b are routed to the support arm 15, and a portion of this routed portion serves as a first connection pad 17ax and a second connection pad 17bx for connecting to a package (not shown).

Further, a pair of notches 15c, 15d are provided on both sides of the support arm 15 along the width direction of the support arm 15 midway in the longitudinal direction of the support arm 15. The functions of the notches 15c, 15d are described in paragraphs 68, 70, 71, 74, etc. of Patent Document 1.
That is, when forming the excitation electrodes 17a, 17b and the connection pads 17ax, 17bx, a metal film is formed on the entire surface of a wafer on which the external shape of the tuning fork has been formed, a resist is applied to the wafer, and the resist is exposed through a predetermined photomask and developed to obtain a resist pattern. Then, the parts of the metal film that are not covered by the resist pattern are removed to form the excitation electrodes and connection pads. However, since the resist on the side of the support arm is difficult to expose, the metal film on the side of the support arm is not easily removed and tends to remain. If the metal film remains on the side of the support arm, the first connection pad 17ax and the second connection pad 17bx cannot be separated. However, if the notches 15c, 15d are provided, a slope is generated at the notch, so the resist is easily exposed, and the short circuit can be prevented.

JP 2014-200043 A

Although the notch described in Patent Document 1 is effective in preventing short-circuiting of the metal film on the side surface of the support arm, there is still room for improvement.
This application was made with attention to this point, and therefore an object of the present invention is to provide a new structure and a manufacturing method thereof that can more reliably separate electrodes in the supporting arms of a three-arm tuning-fork type quartz crystal resonator than in the past.

In order to achieve this object, a tuning-fork type crystal resonator of the present invention comprises a base, first and second vibrating arms extending parallel to each other from the base, a support arm extending from the base between the vibrating arms, a first excitation electrode and a second excitation electrode disposed on the first and second vibrating arms, a first connection pad provided on a tip side of the support arm and a second connection pad provided on the base side of the support arm in order to connect the first excitation electrode and the second excitation electrode to an outside, and at least a pair of notches provided on both sides along a width direction midway in a longitudinal direction of the support arm,
Of the pair of notches, at least the notch located on the -X side of the crystal axis of the quartz is a multi-stage notch having two or more steps in the thickness direction of the support arm.

In carrying out the invention of this tuning fork type quartz crystal resonator, it is preferable that the multiple-stage cutouts include a crystal plane structure in which the R plane of the quartz crystal and the r plane of the quartz crystal are connected along the Y' axis of the quartz crystal when viewed on the surface corresponding to the X plane of the quartz crystal.
In carrying out the invention of this tuning-fork type quartz crystal resonator, it is preferable that the multiple-stage notches include a crystal plane structure in which vertical walls are discontinuously scattered when the surface corresponding to the X-plane of the quartz crystal is viewed along the Z-axis direction of the quartz crystal.
Any of the above crystal plane structures has the effect of reducing the area of the vertical walls generated on the side surfaces of the tuning fork type quartz crystal resonator, so that the surface area that is difficult to expose can be reduced, thereby reducing the risk of short-circuiting between electrodes.

Further, a manufacturing method of a tuning-fork type quartz crystal resonator of the present invention includes a base, first and second vibrating arms extending from the base in parallel to each other, a support arm extending from the base between the vibrating arms, a first excitation electrode and a second excitation electrode disposed on the first and second vibrating arms, a first connection pad provided on a tip side of the support arm and a second connection pad provided on the base side of the support arm in order to connect the first excitation electrode and the second excitation electrode to an outside, and at least a pair of notches provided on both sides along a width direction midway in a longitudinal direction of the support arm, wherein at least a notch located on a −X side of a crystal axis of quartz crystal is a multi-step notch with two or more steps toward a thickness direction of the support arm,
a first etching process for forming an outer shape of the tuning-fork type quartz crystal resonator, which is composed of the base portion, the first and second vibrating arms, the support arms, and a first cutout of the multiple cutouts, on a quartz crystal wafer;
a second etching step of forming a second notch of the multiple notches in the quartz crystal wafer that has been subjected to the first etching step;
forming a metal film on the entire surface of the quartz crystal wafer after the second etching process;
a step of patterning the metal film to form the first excitation electrode, the second excitation electrode, the first connection pad, and the second connection pad;
The present invention is characterized by comprising:

When carrying out this method of manufacturing a tuning fork type quartz crystal resonator, it is preferable that the planar size of the second notch be larger than the first notch.

When carrying out this manufacturing method for a tuning fork type quartz crystal resonator, it is preferable that the tuning fork type quartz crystal resonator has a groove in each of the first vibrating arm and the second vibrating arm, and that the second etching process also serves as the etching process for forming the groove.

In the field of tuning fork type quartz crystal resonators, miniaturization and complication are remarkable. Therefore, photolithography technology and wet etching are used when manufacturing tuning fork type quartz crystal resonators. Therefore, the crystal anisotropy of quartz crystal against wet etching becomes prominent, and the part of the tuning fork that has been etched, especially the part that corresponds to the -X face of the quartz crystal, becomes a vertical wall, making it difficult for exposure light to hit it. In contrast, in the case of the tuning fork type quartz crystal resonator of this invention, at least the notch located on the -X side of the crystal axis of the quartz crystal of the pair of notches is a multi-stage notch, so that the vertical wall can be reduced and exposure at the notch can be promoted compared to the case where a simple notch is provided. Therefore, short-circuiting between the first connection pad and the second connection pad can be reduced compared to the conventional case.
Furthermore, according to the method of manufacturing a tuning-fork type crystal resonator of the present invention, since multiple notches can be easily manufactured, a tuning-fork type crystal resonator having multiple notches can be easily manufactured.

FIG. 1 is an explanatory diagram of a tuning-fork type crystal resonator 100 according to an embodiment. FIG. 2 is an explanatory diagram of the embodiment. FIG. 3 is an explanatory diagram of a comparative example. FIG. 1 is a diagram illustrating an example of an actual product. FIG. 2 is an explanatory diagram of an embodiment of the manufacturing method according to the present invention. FIG. 1 is an explanatory diagram of the prior art and problems.

Below, an embodiment of the tuning fork type crystal resonator and its manufacturing method of the present invention will be described with reference to the drawings. Note that each figure used in the description is merely a schematic illustration to the extent that these inventions can be understood. In addition, in each figure used in the description, components that are similar to those in the conventional drawings are given the same numbers, and their explanation may be omitted. Furthermore, the shapes, dimensions, materials, etc. described in the following description are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to only the following embodiments.

1. Structure of a Tuning-Fork-Type Crystal Resonator FIG. 1 is an explanatory diagram of a tuning-fork-type crystal resonator 100 according to an embodiment, in which FIG. 1A is a plan view thereof, and FIG. 1B is a cross-sectional view taken along line P-P of FIG.
The tuning fork type crystal resonator 100 of the embodiment includes a base 11, a first vibrating arm 13a and a second vibrating arm 13b, a support arm 15, a groove 13c (shown only in FIG. 1B), a first excitation electrode 17a and a second excitation electrode 17b, and a first connection pad 17ax and a second connection pad 17bx. These components are similar to those of the known tuning fork type crystal resonator described with reference to FIG. 6, so a description thereof will be omitted.

A characteristic feature of the tuning fork type quartz crystal resonator 100 of the embodiment is that, of the pair of notches 101, 15d provided in the support arm 15, the notch 101 that is located at the -X side of the X-axis of the quartz crystal is a multi-step notch 101 that is stepped in the thickness direction of the support arm 15, i.e., in the Z-axis direction of the quartz crystal.
The number of notches in the multi-stage notch 101 may be any number of two or more, but considering the object of the present invention and ease of manufacture, two or three stages are preferable. In the embodiment, the multi-stage notch 101 is configured in two stages, a first stage notch 101a and a second stage notch 101b. In this embodiment, the notch located on the +X side of the crystal is a normal notch 15d as in the conventional case, but the notch located on the +X side of the crystal may also be configured with a multi-stage notch 101.

In this embodiment, the multi-stage notches 101 and the notches 15d are provided in the support arm 15 so as to be aligned linearly in the X direction, but the multi-stage notches 101 and the notches 15d may be offset from each other in the Y' direction. Also, one or more pairs of notches may be provided.
In addition, in the example shown in FIG. 1, the planar shape of the multi-stage cutout is a right-facing triangular shape for the first stage and a U-shape with an open left side for the second stage, but the planar shape can be changed to any shape that can easily achieve the short circuit prevention effect.

2. Examples and Comparative Examples Next, the multi-stage notches 101 in the tuning-fork type crystal resonator of the present invention will be described in detail with reference to examples and comparative examples.
FIG. 2 is an explanatory diagram of an embodiment. Specifically, FIG. 2(A) is an SEM photograph taken from above, focusing on a pair of notches in the support arm 15 of a tuning fork type quartz crystal resonator prototyped according to the concept of the present invention. FIG. 2(B) is an SEM photograph taken from the side, focusing on the multi-stage notch 101, and supplementing the state and crystal plane of each face. FIG. 2(C) is an SEM photograph taken from above, focusing on the multi-stage notch 101, and supplementing the state and crystal plane of each face. FIG. 3 is an explanatory diagram of a comparative example. Specifically, it is an SEM photograph taken from above, focusing on the notches 15c and 15d in the support arm 15 of a conventional tuning fork type quartz crystal resonator that does not have multi-stage notches. FIG. 3(B) is an SEM photograph taken from the side, focusing on the notch 15c, and supplementing the state and crystal plane of each face. FIG. 3C is an SEM photograph taken from above focusing on the notch 15c, and supplements the state of each surface and the crystal planes.

2 and 3, it is clear that the position, shape and area of the vertical wall V are different between the embodiment and the comparative example, and further, the arrangement and shape of the r-plane of the quartz crystal and the R-plane of the quartz crystal are different.
As can be understood from the SEM photographs and supplementary notes on crystal planes in Figures 2(A) to 2(C), in the case of the multi-stage notch 101 of the tuning fork type quartz crystal resonator of the embodiment, the vertical walls V have a relatively narrow continuous area and are scattered. Moreover, as can be understood from Figure 2(C) in particular, it can be seen that the r-plane and R-plane of the quartz crystal have a crystal plane structure that is continuous in the Y'-axis direction of the quartz crystal.
That is, when the surface of the multi-stage notch 101 corresponding to the X-plane of the quartz crystal is viewed along the Z-axis direction of the quartz crystal, the multi-stage notch 101 includes a crystal plane structure in which the vertical walls V are discontinuously scattered. Therefore, the multi-stage notch 101 according to the present invention can reduce the area of the vertical walls that are difficult to expose, and can reduce the continuity.
In contrast, in the case of the comparative example, as can be seen from the SEM photographs and crystal plane supplements in Figures 3(A) to 3(C), and particularly from Figure 3(C), the vertical wall V exists over a wide area on the side of the support arm 15, from the front to the back of the support arm. Moreover, the r-plane and R-plane of the quartz crystal are separated by the vertical wall V, are located at positions apart from each other, and have a relatively small area.

If the vertical walls are continuous or have a large area on the side of the support arm, the metal film is likely to remain on the side of the support arm 15, increasing the risk of short-circuiting between the first connection pad 17ax and the second connection pad 17bx (see FIG. 1). Also, if the r-plane and R-plane of the quartz crystal are scattered or have a small area, the area of the slope on the side of the support arm is small and exposure is difficult, so the metal film is likely to remain on the side of the support arm 15, increasing the risk of short-circuiting between the first connection pad 17ax and the second connection pad 17bx (see FIG. 1).
When considering the mechanism of such a short circuit, it can be seen that the structure of the multiple-stage notches 101 such as that of the tuning-fork type quartz crystal resonator of the embodiment is preferable for reducing short circuit defects between the first connection pad 17ax and the second connection pad 17bx (see FIG. 1).

3. Example of Actual Product Next, as an example for deepening understanding of the present invention, an example of an actual product 20 using the tuning-fork type crystal resonator 100 of the present invention will be described. Figure 4 is a diagram for that purpose, in particular, Figure 4(A) is a plan view, Figure 4(B) is a cross-sectional view taken along line P-P in Figure 4(A), and Figure 4(C) is a rear view.
The actual product 20 is an example using a ceramic container 21 having a recess 21a for accommodating a tuning fork piece. The bottom surface of the recess 21a is provided with an adhesive pad 21b on the container side. The outer bottom surface of the container 21 is provided with an external mounting terminal 21c. The adhesive pad 21b and the external mounting terminal 21c are connected by via wiring (not shown).
The tuning-fork type crystal unit 100 is connected and fixed to the container 21 at the positions of the first adhesive pad 17ax and the second adhesive pad 17bx of the support arm 15 and the adhesive pad 21b on the container side by a conductive adhesive 23. A lid member 25 is bonded to the top surface of the container 21, sealing the tuning-fork type crystal unit 100 in the container 21.

4. Embodiment of the Manufacturing Method Next, an embodiment of the manufacturing method of the present invention will be described.
In the present invention of the manufacturing method of the tuning fork type crystal resonator, first, as shown in Fig. 5 (A), a first etching step is performed to form the outer shape 11a of the tuning fork type crystal resonator consisting of the base, the first and second vibrating arms, the support arms, and the first notches 101x and 15x of the multiple notches on the crystal wafer W1. Specifically, a metal film is formed on the entire surface of the wafer W1, and then a resist pattern is formed on the wafer to cover the outer shape 11a and the parts that will become the crosspieces, and then the metal film is selectively etched using the resist pattern as a mask. After that, the wafer is immersed in a hydrofluoric acid-based etchant to obtain a wafer in which tuning fork pieces corresponding to the outer shape 11a are arranged in a matrix.

Next, as shown in FIG. 5B, a second etching process is performed to form the second notch of the multi-stage notch on the quartz wafer after the first etching. Specifically, a resist pattern having a window 101y that exposes the area of the remaining metal film corresponding to the second notch is formed on the quartz wafer W2 after the first etching, and then the wafer is immersed in a hydrofluoric acid-based etchant. This process is preferably performed together with the process of forming the window 13ca for forming a groove in the vibrating arm, and is performed in this embodiment. After the second etching process, the main part of the tuning fork-type quartz element having the multi-stage notch 101 shown in FIG. 1, FIG. 2, etc. is completed. It is preferable that the pattern for forming the second notch is larger in plan view than the first notch at least in the X-axis direction of the quartz.
Next, a metal film for forming excitation electrodes is formed on the entire surface of the quartz crystal wafer that has undergone the second etching process, and then this metal film is patterned to form first and second excitation electrodes, as well as first and second connection pads.
According to the manufacturing method of the embodiment described above, it is possible to easily form the multi-stage notch 101. Moreover, it is preferable because it can be formed simultaneously in the process of forming the grooves of the vibrating arms.

100: tuning fork type crystal unit of the embodiment 11: base 13a: first vibrating arm 13b: second vibrating arm 13c: groove 15: support arm 17a: first excitation electrode 17b: second excitation electrode 17ax: first connection pad 17bx: second connection pad 101: 15c: pair of notches 101: multiple notches V: vertical wall r: r-face of crystal R: R-face of crystal

Claims (3)

a tuning-fork type crystal resonator including a base, first and second vibrating arms extending from the base in parallel to each other, a support arm extending from the base between the vibrating arms, a first excitation electrode and a second excitation electrode disposed on the first and second vibrating arms, a first connection pad provided on a tip side of the support arm and a second connection pad provided on the base side of the support arm in order to connect the first excitation electrode and the second excitation electrode to an outside, and at least one pair of notches provided on both sides along a width direction midway in a longitudinal direction of the support arm,
Of the pair of notches , the notch located on the −X side of the crystal axis of the quartz crystal is a two-step notch in the thickness direction of the support arm,
The two-step notch includes a crystal plane structure in which the R plane and the r plane of the quartz crystal are connected along the Y' axis of the quartz crystal when viewed from the surface corresponding to the X plane of the quartz crystal, and includes a crystal plane structure in which vertical walls are discontinuously scattered along the Z axis direction of the quartz crystal . a first excitation electrode and a second excitation electrode disposed on the first and second vibration arms; a first connection pad provided on a tip side of the support arm and a second connection pad provided on the base side of the support arm in order to connect the first excitation electrode and the second excitation electrode to an outside; and at least a pair of notches provided on both sides along a width direction midway in a longitudinal direction of the support arm , the notch located on the -X side of a crystal axis of quartz being a two-step stepped notch toward a thickness direction of the support arm,
a first etching process for forming an outer shape of the tuning-fork type quartz crystal resonator, which is composed of the base portion, the first and second vibrating arms, the support arms, and the first notch of the pair of notches, on a quartz crystal wafer;
a second etching step for forming a second notch of the two-stage notch in the quartz crystal wafer after the first etching step, the second notch being larger in plan view than the first notch;
forming a metal film on the entire surface of the quartz crystal wafer after the second etching process;
a step of patterning the metal film to form the first excitation electrode, the second excitation electrode, the first connection pad, and the second connection pad;
A method for manufacturing a tuning fork type crystal resonator comprising the steps of: 3. The method for manufacturing a tuning-fork type quartz crystal resonator according to claim 2, wherein the tuning-fork type quartz crystal resonator has grooves in each of the first vibrating arm and the second vibrating arm, and the second etching process also serves as an etching process for forming the grooves.
that's all

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