JP2007013383A - Manufacturing method of piezoelectric resonator piece, and piezoelectric resonator piece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal resonator piece with a perpendicular cross-sectional shape and an accurate planar shape for realizing a highly accurate frequency and to provide a manufacturing method with a high production efficiency for realizing the crystal resonator piece. <P>SOLUTION: The manufacturing method of the crystal resonator piece 10 includes: a dry etching processing step of boring grooves 13 on both front and rear sides of each vibration arm 12 and forming the crystal resonator chip 10 by leaving parts of the crystal resonator chip 10 in its cross-sectional directions of outer circumferential edges 14, 15; and a wet etching processing step of removing the parts of the crystal resonator chip 10 in the cross-sectional directions of the outer circumferential edges 14, 15. Further, the crystal resonator chip 10 is manufactured as above at a low cost, has a highly accurate resonance frequency and can attain downsizing and high frequency applications. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a piezoelectric vibrating piece and a piezoelectric vibrating piece manufactured by the manufacturing method.

  Conventionally, a mask film is formed on the entire surface of a quartz substrate as a piezoelectric material, exposed to light, and the mask film surface is silylated, followed by a dry etching process, and further an etching mask material is formed on the entire surface. Removing the etching mask material until the mask film is exposed, and then removing the mask film to form an etching mask made of the etching mask material, and then using the etching mask. There is known a manufacturing method of a crystal resonator having a step of processing the crystal substrate (see, for example, Patent Document 1).

  Further, the arm portion includes at least two vibration arm portions (vibrating arms) and at least one base portion that connects the arm portions. The arm portion is provided with a drive electrode and a detection electrode. A tuning fork type vibrator in which the difference between the left and right sides in contact with the upper and lower sides is equal and the opposite sides are parallel, and the arm part is processed by simultaneous dry etching of the upper surface and the lower surface. (For example, refer to Patent Document 2).

Japanese Patent Laid-Open No. 5-218775 (pages 2, 3 and 1) JP 2004-93318 A (3rd and 4th pages, FIGS. 1 and 2)

  Traditionally, crystal resonators were formed from a quartz substrate by chemical etching (wet etching) using photolithography technology. However, because the quartz substrate has anisotropy in crystal orientation, In addition to the fact that the cross-sectional shape of the crystal resonator after processing becomes a slope, there is a problem that an accurate shape cannot be obtained with respect to the resist mask shape.

  Therefore, as described in Patent Document 1 or Patent Document 2 described above, it has been proposed to use dry etching for forming a crystal resonator. According to Patent Document 1, dry etching is employed as a forming means when forming a crystal resonator from a flat crystal substrate, and a crystal resonator having a vertical cross-sectional shape is obtained.

  Further, in Patent Document 2, it is said that a crystal resonator having symmetrical vertical and horizontal lengths can be obtained by simultaneously applying ion plasma to both the upper and lower surfaces of the crystal by dry etching.

  However, in Patent Document 1 and Patent Document 2 described above, when a groove is provided in the vibrating arm of a crystal resonator in order to reduce the size and increase the frequency, a groove forming step is performed separately from the formation of the outer shape. In such a manufacturing method, a relative shape error between the outer shape and the groove is predicted to occur, and there is a problem that an accurate oscillation frequency and resonance frequency cannot be obtained.

  Furthermore, dry etching generally has a slower etching rate than chemical etching, and the outer shape forming process and the groove forming process are separate, which may lead to longer processes and lower production efficiency. It is done.

  An object of the present invention is to solve the above-described problems, and has a vertical cross-sectional shape and an accurate plane shape in the piezoelectric vibrating piece, and realizes a highly accurate frequency, and the piezoelectric vibrating piece. Is to provide a manufacturing method with high production efficiency.

The method for manufacturing a piezoelectric vibrating piece according to the present invention is a method for manufacturing a piezoelectric vibrating piece by separately forming a piezoelectric vibrating piece from a substrate made of a piezoelectric material, and each of the front and back surfaces of the main surface of the vibrating arm constituting the piezoelectric vibrating piece. And a step of forming the outer shape of the piezoelectric vibrating piece from both front and back surfaces, and at least the means for drilling the groove is a dry etching process. .
Here, examples of the piezoelectric material include quartz, and examples of the piezoelectric vibrating piece include a quartz vibrating piece.

  According to the present invention, the method for manufacturing a piezoelectric vibrating piece includes the above-described groove drilling step and outer shape forming step provided in the vibrating arm, and the groove is drilled by dry etching. This groove is provided to achieve further miniaturization and higher frequency of the piezoelectric vibrating piece. In the conventional wet etching process (chemical etching process), the crystal orientation anisotropy (etching rate anisotropy) ), The cross section inside the groove is formed obliquely, and the symmetry of the shape may be lost, and the influence on the vibration characteristics (frequency characteristics) cannot be ignored.

  In dry etching processing, since the anisotropy of crystal orientation of crystal can be ignored, the desired shape is formed accurately, and in particular, the cross section inside the groove is formed perpendicular to the main surface of the piezoelectric vibrating piece. A highly accurate oscillation frequency and resonance frequency can be obtained.

  Further, in the present invention, a dry etching processing step of forming the groove and forming an outer shape leaving a part of a cross section of the outer peripheral edge of the piezoelectric vibrating piece, and the piezoelectric vibrating piece after the processing step And a wet etching process for removing a part of the cross section of the outer peripheral edge of the outer shape to form an outer shape.

  As described above, the groove provided on the vibrating arm and the outer shape (with a part in the cross-sectional direction of the outer peripheral edge of the piezoelectric vibrating piece remaining) are formed by dry etching, so that the groove and the outer shape are relatively Since the target position and shape error are reduced, and the cross section (side surface) of the groove and the outer shape can be formed perpendicular to the main surface, high-accuracy frequency characteristics can be obtained.

  Furthermore, in order to remove the part of the cross-sectional direction of the outer periphery of the outer shape remaining by dry etching processing by wet etching processing, collectively performing the groove drilling processing and outer shape forming processing by dry etching processing, The amount of processing by wet etching can be reduced, the processing time can be shortened, and the manufacturing efficiency can be increased.

  In the manufacturing method, it is preferable that an etching depth of an outer peripheral edge portion of the piezoelectric vibrating piece is deeper than an etching depth of the groove by the dry etching process.

  Since the dry etching of the outer peripheral edge of the piezoelectric vibrating piece is performed from both the front and back sides, the remaining thickness of the outer peripheral edge is made thinner than the remaining thickness of the groove by using the etching depth as described above. become. Therefore, after the groove is formed, the amount of processing when the outer peripheral edge is separated from the substrate by wet etching is reduced, so that the processing time can be shortened.

Further, in the present invention, a wet etching process for forming an outer shape while leaving a part of a cross section of the outer peripheral edge of the piezoelectric vibrating piece, and after the wet etching process, the groove is formed, And a dry etching process step of forming an outer shape by removing a part of the cross section of the outer peripheral edge of the resonator element.
This wet etching processing step means, for example, that the outer peripheral edge of the piezoelectric vibrating piece is etched from both the front and back surfaces, and a rough shape of the piezoelectric vibrating piece is formed while leaving a part of the thickness of the outer peripheral edge.

  According to such a manufacturing method, the outer peripheral edge of the piezoelectric vibrating piece is processed by wet etching with a high etching rate, and the groove and the outer shape that require high accuracy are separated by dry etching. While improving efficiency, the perpendicularity with respect to the main surface of the piezoelectric vibrating piece of a groove | channel is acquired, and the piezoelectric vibrating piece provided with the favorable frequency characteristic is realizable.

  In the present invention, it is preferable that the outer peripheral edge of the piezoelectric vibrating piece is formed by the wet etching process so that the piezoelectric vibrating piece does not fall off the substrate.

  A plurality of piezoelectric vibrating pieces are collectively formed on the substrate and separated and completed, but the outer peripheral edge portion connects the substrate and each piezoelectric vibrating piece until the piezoelectric vibrating piece is formed into a predetermined shape. Therefore, a part of the thickness is left. Therefore, the outer peripheral edge may be thin enough that the piezoelectric vibrating piece does not fall off from the substrate during processing. By doing so, the groove perforation and the outer peripheral edge separation processing can be performed collectively. It can be done easily.

  The piezoelectric vibrating piece of the present invention is manufactured by the above-described manufacturing method, has a base portion and a vibrating arm extending from the base portion, and grooves are formed on both front and back surfaces of the main surface of the vibrating arm. It is characterized by that.

  According to the present invention, since it is manufactured by the above-described manufacturing method and has the groove as described above, it has a low-cost, high-accuracy resonance frequency, and can be downsized and increased in frequency. A piezoelectric vibrating piece can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 show a piezoelectric vibrating piece according to the first embodiment of the present invention and a method for manufacturing the piezoelectric vibrating piece, and FIG. 4 shows a method for manufacturing the piezoelectric vibrating piece according to the second embodiment.
(Embodiment 1)

FIG. 1 shows an example of a piezoelectric vibrating piece according to Embodiment 1, and FIGS. 2 and 3 show a method for manufacturing the piezoelectric vibrating piece. Here, a tuning fork type crystal vibrating piece will be described as an example of the piezoelectric vibrating piece.
FIG. 1 is a plan view showing a crystal vibrating piece 10 according to the present embodiment. Although the tuning fork type crystal vibrating piece is illustrated in FIG. 1 as the quartz vibrating piece, the shape is not limited as long as it has a groove in a part. In FIG. 1, the quartz crystal vibrating piece 10 of the present embodiment is a tuning fork type quartz crystal vibrating piece formed by extending a pair of vibrating arms 12 from the end face of a base 11.

  A groove 13 is formed in the central portion of the main surface of the pair of vibrating arms 12. The groove 13 is also formed at the same position, shape, and depth on the back side of the vibrating arm 12. The crystal resonator element 10 has a planar shape that is symmetrical with respect to the center line C in the drawing.

  Although not shown in the figure, the crystal vibrating piece 10 is formed with excitation electrodes and detection electrodes inside the front and back surfaces (including side surfaces) of the vibrating arm 12 and inside the groove 13, and these electrodes extend to the base 11. It is mounted in a package to constitute a crystal resonator and is connected to an external circuit.

Subsequently, a processing method of the crystal vibrating piece 10 in the present embodiment will be described with reference to the drawings. In the present embodiment, an example in which quartz is used as the piezoelectric material (therefore, the substrate in this embodiment is a quartz substrate) is described.
FIG. 2 is a plan view showing a part of the arrangement of the crystal vibrating pieces 10 on one crystal substrate 1. On the quartz substrate 1, the plurality of quartz vibrating pieces 10 are aligned and arranged in parallel to the X axis and the Y axis as shown in the figure.

Here, the adjacent quartz crystal vibrating pieces 10 are arranged with outer peripheral edge portions 15, respectively. Note that the space 14 (see FIG. 1) between the pair of vibrating arms 12 is also a part of the outer peripheral edge 15 in a state where the space 14 is disposed on the quartz substrate 1.
In the quartz substrate 1, the X axis is an electric axis, the Y axis is a mechanical axis, and the Z axis is an optical axis.

Next, the method for manufacturing the quartz crystal resonator element 10 according to the embodiment will be described in more detail.
FIG. 3A to FIG. 3E are partial cross-sectional views showing the processing steps of this embodiment. In addition, this sectional drawing has shown the AA cross section shown in FIG.

  FIG. 3A is a cross-sectional view illustrating a film forming process of the mask 30. Reference is also made to FIG. In FIG. 3A, first, a mask 30 is formed uniformly on both the front and back surfaces of the quartz substrate 1 polished so that both the front and back surfaces are uniform. In the following, the front side will be described because both front and back surfaces are collectively processed. The mask 30 is formed in the planar shape of the crystal vibrating piece 10, and an area other than the opening 31 corresponding to the groove 13 and the crystal vibrating piece 10 corresponding to the outer peripheral edge portions 14 and 15 is opened. Subsequently, dry etching is performed.

  FIG. 3B is a cross-sectional view showing a state after the dry etching process. In FIG. 3B, the opening 31 of the mask 30 is etched, and the groove 13 is formed. In the dry etching process, etching is performed using a reactive gas, for example, CHF3, in an RIE (reactive ion etching) apparatus using a generally employed oxide film dry etcher.

  At this time, the outer peripheral edge portions 14 and 15 have a remaining thickness at a part of the central portion in the cross-sectional direction so that the outer shape of the quartz crystal vibrating piece 10 is formed. In addition, the etching depth from the surface (or back surface) of the quartz substrate 1 of the outer peripheral edge portions 14 and 15 is formed deeper than the etching depth from the surface (or back surface) of the groove 13. Accordingly, the remaining thickness of the outer peripheral edge portions 14 and 15 is smaller than the remaining thickness of the bottom portion of the groove 13. This difference is caused by a difference in etching rate due to the microloading effect that is a characteristic of the dry etching process because the width of the groove 13 is smaller than the outer peripheral edge portions 14 and 15.

Since the side surfaces of the outer peripheral edge of the groove 13 and the quartz crystal resonator element 10 are formed by dry etching, there is no etching anisotropy resulting from the crystal orientation anisotropy of the crystal. It is formed vertically.
Next, a resist film 20 is formed in a range corresponding to the planar shape of the quartz crystal vibrating piece 10.

FIG. 3C shows a state in which the resist film 20 is formed. First, after the resist film 20 is formed on the entire surface of the quartz substrate 1, exposure is performed and the range corresponding to the planar shape of the quartz crystal vibrating piece 10 and the entire inside of the groove 13 are exposed as shown in FIG. Is formed in a state where is left. The outer peripheral edges 14 and 15 of the quartz crystal vibrating piece 10 are opened. In this state, wet etching is performed to remove the outer peripheral edges 14 and 15 of the quartz crystal vibrating piece 10.
The resist film 30 can be replaced with a metal mask or the like.

  FIG. 3D shows a state where the outer peripheral edge portions 14 and 15 of the crystal vibrating piece 10 are removed by the wet etching process. As described above, since only the outer peripheral edge portions 14 and 15 of the resist film 20 are opened, in this wet etching process, only the outer peripheral edge portion is removed, and the outer shape of the crystal vibrating piece 10 is formed. . At this time, since the remaining thickness of the outer peripheral edge of the crystal vibrating piece 10 is thinner than the remaining thickness of the groove 13, the wet etching processing time is short.

  FIG. 3E shows the crystal vibrating piece 10 after the resist film 20 is removed after the above-described wet etching process. In this way, the crystal vibrating piece 10 having the groove 13 as shown in FIG. 1 is formed.

  Therefore, according to the above-described first embodiment, most of the cross section of the groove 13 and the outer peripheral edge portion is formed with high accuracy and the cross sectional shape is perpendicular to the surface of the crystal vibrating piece 10 by dry etching. Therefore, a highly accurate oscillation frequency and resonance frequency can be obtained.

  Further, in this way, the groove 13 provided in the vibrating arm 12 and most of the cross-section of the outer peripheral edge of the quartz crystal vibrating piece 10 are collectively formed by dry etching, so the relative position between the groove 13 and the outer shape. The shape error is reduced, the symmetry of the pair of vibrating arms 12 is maintained, and the excitation electrode or the detection electrode formed after forming the outer shape is formed on the outer portion of the vibrating arm 12. The distance between the electrode and the electrode formed in the groove 13 can be formed with high accuracy, and good frequency characteristics can be obtained.

Further, the groove drilling process and the outer shape forming process are collectively performed by dry etching, and then a part of the cross-section (thickness) of the outer peripheral edge left in the dry etching process is removed by wet etching. Therefore, the amount of processing by wet etching can be reduced, the processing time can be shortened, and the manufacturing efficiency can be increased.
(Embodiment 2)

  Then, the manufacturing method of the crystal vibrating piece 10 which concerns on Embodiment 2 of this invention is demonstrated with reference to drawings. The second embodiment is different from the first embodiment described above in that the order of the dry etching process and the wet etching process and the processing parts at that time are different, and the shape of the crystal resonator element when completed is the same. For this reason (see FIG. 1), common portions will be described with the same reference numerals. The arrangement relationship of the quartz crystal vibrating pieces on the quartz substrate 1 is also shown in FIG.

FIG. 4A to FIG. 4F are cross-sectional views illustrating the manufacturing steps of the crystal vibrating piece 10 according to the present embodiment. The AA cross section represented by FIG. 1 is shown. First, masks 30 are formed on both the front and back surfaces of the quartz substrate 1.
FIG. 4A shows a state in which a mask 30 is formed on the quartz substrate 1. The mask 30 is formed into a shape corresponding to the outer shape of the crystal vibrating piece 10. Note that the mask 30 can be replaced with a resist film. Next, wet etching is performed from both the front and back sides.

FIG. 4B shows the crystal substrate 1 after the wet etching process. In FIG. 4B, the external shape of the crystal vibrating piece 10 is formed by this wet etching process. At this time, the outer peripheral edge portions 14 and 15 (see also FIGS. 1 and 2) of the quartz crystal vibrating piece 10 leave a part of the cross section (thickness). Here, the remaining etching thickness of the outer peripheral edge portions 14 and 15 remains such that the crystal vibrating piece 10 does not fall off from the crystal substrate 1 during the processing. This thickness is preferably several μm or less.
Then, once the mask 30 is removed, the mask 40 is formed over the entire surface.

FIG. 4C shows a process for forming the mask 40. A mask 40 is formed on the entire surface of the quartz crystal substrate 1 on which the external shape of the quartz crystal vibrating piece 10 is formed by the wet etching process described above.
Then, as shown in FIG. 4D, a resist film 25 in a range corresponding to the crystal vibrating piece 10 is formed on the surface of the mask 40.

  FIG. 4D shows a state where a resist film 25 is formed. In FIG. 4D, the resist film 25 is formed in a range corresponding to the crystal vibrating piece 10 on the upper surface of the mask 40, but an opening 26 is formed in a range corresponding to the groove 13. Then, the resist film 25 is used to peel the region where the mask 40 is to be etched, and the resist film 25 is removed.

  FIG. 4E shows a state where the mask 40 is formed in a predetermined shape. Here, the mask 40 is formed in a range excluding the groove 13 and the outer peripheral edge portions 14, 15, that is, in the outer shape range of the crystal vibrating piece 10 excluding the range of the groove 13. In such a state, the outer peripheral edge portions 14 and 15 are removed by a dry etching process, and the crystal vibrating piece 10 is separated into a single piece.

  FIG. 4F shows the crystal vibrating piece 10 formed by the dry etching process described above. The quartz crystal resonator element 10 is collectively separated from the groove 13 and the quartz substrate 1 in this dry etching process. Here, the thickness relationship between the groove 13 and the outer peripheral edge portions 14 and 15 will be described. The remaining etching thicknesses 14a and 15a (see FIG. 4 (e)) of the outer peripheral edge portions 14 and 15 are the etching depth of the groove 13. Since it is smaller than 13a and 13b, the outer peripheral edge is penetrated by etching until the depth of the groove 13 is ensured, and the crystal vibrating piece 10 is formed separately from the crystal substrate 1. Then, the mask 40 is removed, and the crystal vibrating piece 10 is completed.

  Therefore, according to the second embodiment described above, the outer peripheral edge portions 14 and 15 of the quartz crystal vibrating piece 10 are processed by wet etching with a high etching speed, and the groove and the outer shape that require high accuracy are separated by dry etching. Thus, the manufacturing efficiency is improved, and the side surfaces of the groove 13 and the outer peripheral edge portions 14 and 15 are perpendicular to the surface (main surface) of the crystal vibrating piece, and the excitation electrode is formed after the outer shape is formed. Alternatively, in the detection electrode, since the distance between the electrode formed on the outer shape of the vibrating arm 12 and the electrode formed in the groove 13 can be formed with high accuracy, the crystal vibrating piece having good frequency characteristics 10 can be realized.

  Further, a plurality of quartz crystal vibrating pieces 10 are collectively formed and separated on the quartz substrate 1 and completed. However, a part of the cross section (thickness) of the outer peripheral edge portion is until the quartz crystal vibrating piece 10 is formed in a predetermined shape. In the meantime, the quartz substrate 1 and each quartz crystal vibrating piece 10 are left to be connected. Therefore, the outer peripheral edge portions 14 and 15 need only be thin enough that the quartz crystal resonator element 10 does not fall off from the quartz crystal substrate 1 during the processing. , 15 can be easily performed in a lump.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
That is, although the present invention has been illustrated and described with particular reference to particular embodiments, it is not intended to depart from the technical spirit and scope of the invention. Those skilled in the art can make various modifications in materials, combinations, and other detailed configurations.

  Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded some or all restrictions, such as a combination, is included in this invention.

  For example, in Embodiments 1 and 2, quartz is exemplified as the piezoelectric substrate, but it can also be applied to piezoelectric substrates other than quartz, and is particularly effective for piezoelectric substrates having crystal orientation anisotropy. .

  In the first and second embodiments, the tuning fork type quartz vibrating piece is described as an example. However, the tuning fork type quartz vibrating piece is not limited to the tuning fork type, and can be applied to a piezoelectric vibrating piece generally referred to as an H type or a double T type. is there.

  Therefore, according to the first and second embodiments described above, a quartz crystal resonator element having a vertical cross-sectional shape and an accurate planar shape and realizing a highly accurate oscillation frequency and resonance frequency, and the crystal resonator element are realized. It is possible to provide a manufacturing method with high manufacturing efficiency.

FIG. 3 is a plan view showing the crystal resonator element according to the first embodiment of the invention. The top view which shows a part of arrangement | positioning of the crystal vibrating piece on the quartz substrate which concerns on Embodiment 1 of this invention. (A)-(e) is sectional drawing which shows the manufacturing method of the quartz crystal vibrating piece which concerns on Embodiment 1 of this invention. (A)-(f) is sectional drawing which shows the manufacturing method of the quartz crystal vibrating piece which concerns on Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Quartz substrate as a substrate, 10 ... Quartz vibrating piece as a piezoelectric vibrating piece, 12 ... Vibrating arm, 13 ... Groove, 14, 15 ... Outer peripheral edge part, 20, 25 ... Resist film, 30, 40 ... Mask

Claims (6)

A method of manufacturing a piezoelectric vibrating piece by separately forming a piezoelectric vibrating piece from a substrate made of a piezoelectric material,
Drilling grooves provided on both the front and back surfaces of the main surface of the vibrating arm constituting the piezoelectric vibrating piece;
Forming the outer shape of the piezoelectric vibrating piece from both front and back sides,
A method of manufacturing a piezoelectric vibrating piece, wherein at least the means for forming the groove is dry etching. In the manufacturing method of the piezoelectric vibrating piece according to claim 1,
A dry etching process for forming the outer shape by drilling the groove and leaving a part of the cross section of the outer peripheral edge of the piezoelectric vibrating piece;
After this processing step, a wet etching processing step of removing a part of the cross section of the outer peripheral edge of the piezoelectric vibrating piece to form an outer shape,
A method for manufacturing a piezoelectric vibrating piece, comprising: In the manufacturing method of the piezoelectric vibrating piece according to claim 2,
The method for manufacturing a piezoelectric vibrating piece, wherein the etching depth of the outer peripheral edge of the piezoelectric vibrating piece is formed deeper than the etching depth of the groove by the dry etching process. In the manufacturing method of the piezoelectric vibrating piece according to claim 1,
A wet etching process for forming an outer shape leaving a part of the cross section of the outer peripheral edge of the piezoelectric vibrating piece;
After this wet etching processing step, a dry etching processing step of forming the outer shape by drilling the groove and removing a part of the cross section of the outer periphery of the piezoelectric vibrating piece;
A method for manufacturing a piezoelectric vibrating piece, comprising: In the manufacturing method of the piezoelectric vibrating piece according to claim 4,
The method of manufacturing a piezoelectric vibrating piece, wherein the outer peripheral edge of the piezoelectric vibrating piece is formed by the wet etching process so as to prevent the piezoelectric vibrating piece from falling off the substrate. It is manufactured by the manufacturing method according to any one of claims 1 to 5,
A base and a vibrating arm extending from the base;
A piezoelectric vibrating piece in which grooves are formed on both front and back surfaces of the main surface of the vibrating arm.

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