JP6105448B2 - Method for manufacturing crystal resonator element - Google Patents

Description

  The present invention relates to a method for manufacturing a crystal resonator element used for, for example, a reference signal source, a clock signal source, or a speed sensor. Hereinafter, a tuning fork-type bending quartz crystal vibrating element (hereinafter abbreviated as “vibrating element”) will be described as an example of a quartz crystal vibrating element.

  FIG. 6 of Patent Document 1 discloses a vibration element in which a groove is formed on each of the front surface and the back surface of the vibration arm. This method of manufacturing a vibrating element (hereinafter referred to as “Prior Art 1”) is disclosed in Patent Document 1 on page 3, lower right column, line 10 to page 4, upper left column, line 3 as follows. . First, a mask for forming an outer shape is created on the front and back of a quartz wafer. Subsequently, the first etching is performed with hydrofluoric acid using this mask to form the outer shape halfway. Subsequently, a part of the mask is opened to form a groove forming / outside forming mask. Finally, a second etching is performed with hydrofluoric acid using this mask to completely form the outer shape and to form a groove having a certain depth.

  In the prior art 1, two wet etching processes are required for the outer shape formation and the groove formation as described above. The reason is that when both the outer shape and the groove portion are formed by one wet etching, the groove portion penetrates on both sides. Therefore, in the prior art 1, since the wet etching process is required twice, the manufacturing process becomes complicated, and the following problem also occurs.

  In order to create the first outer shape forming mask and the second groove forming / outer shape forming mask, two exposure steps are required. At this time, if a positional shift occurs between the first mask and the second mask due to the alignment accuracy at the time of exposure, a positional shift also occurs between the outer shape and the groove. As a result, the vibration balance between the two vibrating arm portions is lost, so that the vibration is greatly propagated to the base portion supporting the vibrating arm portion, resulting in an increase in frequency variation and a deterioration in crystal impedance.

  On the other hand, Patent Document 2 discloses a method for manufacturing a vibration element that can form both the outer shape and the groove by one wet etching (hereinafter referred to as “Prior Art 2”). In the prior art 2, an etching suppression pattern is formed in a portion to be a groove in a mask made of a corrosion-resistant film used when wet etching a quartz wafer. The etching suppression pattern formed in the portion that becomes the groove portion is a protrusion that protrudes from the portion that becomes the one groove surface toward the portion that becomes the other groove surface. According to the prior art 2, since a large number of protrusions in the groove act as an etching suppression pattern, the outer shape of the vibration element and the groove are simultaneously formed by one wet etching. Solvable.

JP 56-66517 A (Fig. 6 etc.) JP 2011-217039 A (FIG. 4 etc.)

  However, with the recent miniaturization of vibration elements, the following problems are occurring in the related art 2.

  FIG. 8 is a plan view showing an etching suppression pattern in the manufacturing method of the prior art 2. FIG. Hereinafter, description will be given based on this drawing.

  The photosensitive resist film 33 left on the corrosion-resistant film 32 in the exposure and development process in the prior art 2 has a planar shape shown in FIG. The etching suppression patterns formed in the portions 130 and 140 that become the groove portions are protrusions 90 that protrude from the portions 131 and 141 that become the first groove surfaces toward the portions 132 and 142 that become the second groove surfaces, respectively.

  With the downsizing of the vibration element, the width 81 of the portions 130 and 140 that become the groove portions becomes narrower. However, if the length 91 of the protrusion 90 is shortened, the action as an etching suppression pattern becomes insufficient, and the portions 130 and 140 that become the groove portions penetrate through the front and back. This is because a certain length 91 is required in order for the protrusion 90 to sufficiently act as an etching suppression pattern.

  In order to solve this problem, it is conceivable to obtain the necessary length 91 by bringing the distance 93 between the tip end of the protrusion 90 and the portions 132 and 142 to be the second groove surfaces as close as possible. However, realizing this requires a high-precision exposure machine, which is not realistic.

  It is also effective to increase the width 92 of the protrusion 90 in order to make the protrusion 90 sufficiently function as an etching suppression pattern. However, in that case, since a large etching residue that is a trace of the protrusion 90 is generated, it becomes difficult to obtain a parallel electric field in the groove portion, which leads to deterioration of characteristics of the vibration element.

  Accordingly, an object of the present invention is to provide a method of manufacturing a vibration element that can form both the outer shape and the groove by one wet etching and can easily cope with the downsizing of the vibration element.

The method for manufacturing a vibration element according to the present invention includes:
A base portion, two vibrating arm portions extending in the same direction from the base portion, a first groove surface and a second groove portion provided on the vibrating arm portions along the longitudinal direction of the vibrating arm portion and facing each other. A method of manufacturing a crystal resonator element comprising a groove portion having a groove surface,
A corrosion-resistant film forming process for forming a corrosion-resistant film on the front and back of the quartz wafer;
A photosensitive resist film forming step of forming a photosensitive resist film on the corrosion-resistant film;
The photosensitive resist film is left as the etching resisting pattern in the portion serving as the groove, and the unnecessary photosensitive resist film is left as the groove and the portion serving as the two vibrating arms. An exposure development process for removing
A patterning step of creating a mask made of the corrosion resistant film by removing the corrosion resistant film not covered with the photosensitive resist film;
A wet etching step of wet etching the crystal wafer using the mask made of the corrosion-resistant film;
Including
The etching suppression pattern protrudes along the longitudinal direction of the vibrating arm portion from the first protrusion protruding from the portion serving as the first groove surface toward the portion serving as the second groove surface. Having a second protrusion,
It is characterized by that.

  According to the present invention, the first protrusion and the second protrusion in the portion to be the groove portion act as an etching suppression pattern, so that the outer shape of the vibration element and the groove portion can be simultaneously formed by one wet etching, and the first protrusion By providing the second protrusion that protrudes from the tip of the protrusion along the longitudinal direction of the vibrating arm portion, the etching suppression pattern can be substantially lengthened, so that the tip of the first protrusion approaches the portion that becomes the second groove surface. Since it is not necessary and it is not necessary to increase the width of the first protrusion, it is possible to easily cope with downsizing of the vibration element.

FIG. 3 is a plan view showing a vibration element obtained by the manufacturing method of Embodiment 1. It is the II-II sectional view taken on the line in FIG. FIG. 5 is a process diagram illustrating the manufacturing method of the first embodiment. It is sectional drawing which shows the manufacturing method of Embodiment 1, and a process progresses in order of FIG. 4 [1] [2] [3]. It is sectional drawing which shows the manufacturing method of Embodiment 1, and a process progresses in order of FIG. 5 [4] [5]. 5 is a plan view showing an etching suppression pattern in the manufacturing method of Embodiment 1. FIG. 6 is a plan view showing an etching suppression pattern in the manufacturing method of Embodiment 2. FIG. It is a top view which shows the etching suppression pattern in the manufacturing method of the prior art 2. 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 the present specification and drawings, the same reference numerals are used for substantially the same components. The shapes depicted in the drawings are drawn so as to be easily understood by those skilled in the art, and thus do not necessarily match the actual dimensions and ratios.

  FIG. 1 is a plan view illustrating a vibration element obtained by the manufacturing method according to the first embodiment. 2 is a cross-sectional view taken along line II-II in FIG. Hereinafter, a description will be given based on FIG. 1 and FIG.

  As shown in FIG. 1, the vibrating element 10 includes a base portion 11, two vibrating arm portions 12 a and 12 b extending from the base portion 11 in the same direction, and the vibrating arm portion 12 a in the longitudinal direction of the vibrating arm portion 12 a ( Groove portions 13a and 14a provided along the ± Y′-axis direction) and groove portions 13b and 14b provided on the vibrating arm portion 12b along the longitudinal direction (± Y′-axis direction) of the vibrating arm portion 12b. I have.

  As shown in FIG. 2, the groove portion 13a has a first groove surface 131a and a second groove surface 132a facing each other, and the groove portion 14a has a first groove surface 141a and a second groove surface 142a facing each other. 13b has a first groove surface 131b and a second groove surface 132b facing each other, and the groove portion 14b has a first groove surface 141b and a second groove surface 142b facing each other. The groove portions 13a and 14a are provided on both surfaces of the vibrating arm portion 12a, and the groove portions 13b and 14b are provided on both surfaces of the vibrating arm portion 12b.

  Quartz crystals are trigonal. A crystal axis passing through the crystal apex is defined as a Z axis, three crystal axes connecting ridge lines in a plane perpendicular to the Z axis are defined as an X axis, and a coordinate axis orthogonal to the X axis and the Z axis is defined as a Y axis. Here, when the coordinate system consisting of these X, Y, and Z axes is rotated within a range of ± 5 degrees around the X axis, the rotated Y axis and Z axis are respectively represented as Y ′ axis and Z axis. 'As axis. In this case, in the first embodiment, the extending direction of the two vibrating arm portions 12a and 12b is the Y′-axis direction, and the direction in which the two vibrating arm portions 12a and 12b are arranged is the X-axis direction. .

  The vibration element 10 is provided with metal films such as excitation electrodes 21a and 21b. The excitation electrode 21a is provided on the outer side surface 121a and the inner side surface 122a of the vibrating arm portion 12a and the groove portions 13b and 14b of the vibrating arm portion 12b. The excitation electrode 21b is provided on the inner side surface 121b and the outer side surface 122b of the vibrating arm portion 12b and the groove portions 13a and 14a of the vibrating arm portion 12a. The base 11 is provided with electrode pads 22a and 22b, wiring patterns 23a and 23b, and frequency adjusting metal films 24a and 24b at the distal ends of the vibrating arms 12a and 12b, respectively.

  Describing in detail with reference to FIG. 2, the vibrating arm 12a is provided with excitation electrodes 21a on both sides so that the planes facing each other across the crystal have the same polarity, and excitation in the grooves 13a and 14a on the front and back surfaces. An electrode 21b is provided. Similarly, the vibrating arm portion 12b is provided with excitation electrodes 21b on both side surfaces so as to have the same polarity on opposite surfaces across the quartz, and excitation electrodes 21a are provided in the groove portions 13b and 14b on the front and back surfaces. . Accordingly, in the vibrating arm portion 12a, the excitation electrode 21a provided on both side surfaces and the excitation electrode 21b provided in the groove portions 13a and 14a have different polarities, and in the vibrating arm portion 12b, excitation electrodes provided on both side surfaces. 21b and the excitation electrodes 21a provided in the grooves 13b and 14b are different from each other. At this time, in the vibrating arm portion 12a, the excitation electrode 21a on the outer surface 121a and the excitation electrode 21b on the first groove surface 131a face each other, and the excitation electrode 21a on the inner surface 122a and the excitation electrode 21b on the second groove surface 142a Are opposed to each other, and a large electric field strength is obtained between the electrodes. The same applies to the vibrating arm 12b.

  Although not illustrated, the vibration element 10 is fixed to the electrode pad on the element mounting member side by the conductive adhesive via the electrode pads 22a and 22b of the base 11, and is electrically connected at the same time.

  In order to operate the vibration element 10, an alternating voltage is applied to the excitation electrodes 21a and 21b. When an electrical state after application is captured instantaneously, in the vibrating arm portion 12a, the excitation electrode 21b provided in the grooves 13a and 14a becomes a positive potential, and the excitation electrode 21a provided on the outer side surface 121a and the inner side surface 122a. Becomes a negative potential, and an electric field is generated from positive to negative. At this time, in the vibrating arm portion 12b, the excitation electrode 21a provided in the grooves 13b and 14b has a negative potential, and the excitation electrode 21b provided on the inner side surface 121b and the outer side surface 122b has a positive potential, and is generated in the vibrating arm portion 12a. The polarity is opposite to the polarity, and an electric field is generated from positive to negative. The electric field generated by the AC voltage causes a stretching phenomenon in the vibrating arm portions 12a and 12b, and a flexural vibration mode having a predetermined resonance frequency is obtained.

  In FIGS. 1 and 2, the etching residue is omitted for easy understanding, but an etching residue actually occurs.

  FIG. 3 is a process diagram illustrating the manufacturing method according to the first embodiment. 4 and 5 are cross-sectional views showing the manufacturing method of the first embodiment. FIG. 6 is a plan view showing an etching suppression pattern in the manufacturing method of the first embodiment. Hereinafter, the manufacturing method of Embodiment 1 is demonstrated based on FIG. 1 thru | or FIG.

  The manufacturing method according to the first embodiment is a method for manufacturing the vibration element 10 shown in FIGS. 1 and 2 and includes the following steps. 4 to 6 show only a portion corresponding to the vibrating arm portion 12a shown in FIGS.

Corrosion-resistant film forming step for forming the corrosion-resistant film 32 on the front and back of the quartz wafer 31 (step S1 in FIG. 3, FIG. 4 [1]).
A photosensitive resist film forming step for forming a photosensitive resist film 33 on the corrosion resistant film 32 (step S2 in FIG. 3, FIG. 4 [2]).
A portion of the photosensitive resist film 33 that becomes the base 11 and the vibrating arm portions 12a and 12b is left, and a portion of the photosensitive resist film 33 that serves as the groove portions 13a, 13b, 14a, and 14b is provided with the photosensitive resist film 33 as the etching suppression pattern 40 (FIG. 6). An exposure development process for removing the remaining photosensitive resist film 33 that is unnecessary (FIG. 3, step S3, FIG. 4 [3]).
Patterning step of creating a mask made of the corrosion resistant film 32 by removing the corrosion resistant film 32 not covered with the photosensitive resist film 33 (step S4 in FIG. 3, FIG. 5 [4]).
A wet etching process (step S5 in FIG. 3, FIG. 5 [5]) in which the crystal wafer 31 is wet etched using a mask made of the corrosion resistant film 32

  As shown in FIG. 6, the etching suppression pattern 40 includes a first protrusion 41 that protrudes from the portions 131 and 141 that become the first groove surfaces toward the portions 132 and 142 that become the second groove surfaces, and the first protrusion 41. And a second protrusion 42 protruding from the tip along the longitudinal direction (± Y′-axis direction) of the vibrating arm portion.

  Next, the above steps will be described in detail.

<Corrosion-resistant film formation process: FIG. 4 [1]>
In the corrosion resistant film forming step, the corrosion resistant film 32 is formed on the front and back of the crystal wafer 31. For example, the corrosion resistant film 32 made of chromium or two layers of chromium and gold is formed by sputtering.

<Photosensitive resist film formation process: FIG. 4 [2]>
In the photosensitive resist film forming step, a photosensitive resist film 33 is formed on the corrosion resistant film 32. For the photosensitive resist film 33, for example, a positive type is used.

<Exposure development process: FIG. 4 [3]>
In the exposure and development process, the photosensitive resist film 33 is exposed and developed on the corrosion resistant film 32. That is, a predetermined pattern is transferred to the photosensitive resist film 33 by using an exposure machine, and the photosensitive resist film 33 in a portion exposed to light is removed by development processing.

  The photosensitive resist film 33 left on the corrosion-resistant film 32 in the exposure and development process has a planar shape shown in FIG. FIG. 6 shows only the portions 130 and 140 that become the groove portions of the vibrating arm portion 12a. A plurality of the etching suppression patterns 40 are provided at regular intervals in the Y′-axis direction in the portions 130 and 140 to be the groove portions. The first protrusion 41 protrudes in the direction of 60 ° clockwise from the Y ′ axis, but is not limited thereto, and may protrude in the direction of 120 ° clockwise from the Y ′ axis, or the Y ′ axis. It may project in a 90 ° direction clockwise. The second protrusion 42 protrudes in the Y ′ axis direction, but may protrude in the −Y ′ axis direction.

<Patterning process: FIG. 5 [4]>
In the patterning step, the corrosion-resistant film 32 that is not covered with the photosensitive resist film 33 is removed to create a mask made of the corrosion-resistant film 32. For removing the corrosion-resistant film 32, a strong acid that etches only the corrosion-resistant film 32 and does not etch the crystal wafer 31 is used. The mask made of the corrosion resistant film 32 also has a planar shape shown in FIG.

<Wet etching process: FIG. 5 [5]>
In the wet etching process, the crystal wafer 31 is wet etched using a mask made of the corrosion resistant film 32. Hydrofluoric acid is used for this wet etching. In FIG. 5 [5], the photosensitive resist film 33 is removed, but the photosensitive resist film 33 is left or a new photosensitive resist film is formed again, and the electrode is lifted off in the next step. Etc. may be formed.

  Thereafter, as shown in FIGS. 1 and 2, a metal film to be the excitation electrodes 21a, 21b and the like is formed on the base 11 and the vibrating arms 12a, 12b. These metal films have a laminated structure in which, for example, a palladium layer or a gold layer is provided on a titanium layer, and are formed by sputtering or vapor deposition. The excitation electrodes 21a, 21b and the like are formed by patterning a metal film using the above-described lift-off or using photolithography and etching.

  As described above, the mask made of the corrosion-resistant film 32 formed in the patterning step (FIG. 5 [4]) also has the planar shape shown in FIG. Since the first protrusion 41 and the second protrusion 42 act as the etching suppression pattern 40 in the wet etching process (FIG. 5 [5]) by using the mask made of the planar corrosion-resistant film 32, the vibration element 10 And the grooves 13a and 14a are simultaneously formed by one wet etching. Although the groove portions 13a and 14a have been described above, the same applies to the other groove portions 13b and 14b.

  Next, the operation and effect of the vibration element 10 will be described.

  (1) The plurality of first protrusions 41 and the second protrusions 42 in the portions 130 and 140 to be the groove portions act as the etching suppression pattern 40, so that the outer shape of the vibration element 10 and the groove portions 13a, 14a, 13b, and 14b are reduced. They can be formed simultaneously by one wet etching.

  (2) Since the second protrusion 42 protruding from the tip of the first protrusion 41 along the longitudinal direction (± Y ′ axis) of the vibrating arms 12a and 12b is provided, the etching suppression pattern 40 can be made substantially longer. Since the tip of the first protrusion 41 does not need to be close to the portions 132 and 142 that form the second groove surface, and the width of the first protrusion 41 does not need to be increased, the vibration element 10 can be easily reduced in size. Yes. That is, since it is not necessary to bring the tip of the first protrusion 41 close to the portions 132 and 142 serving as the second groove surface, a highly accurate exposure machine is not necessary. Since it is not necessary to increase the width of the first protrusion 41, an etching residue that is a trace of the first protrusion 41 is hardly generated. Therefore, it becomes easy to obtain a parallel electric field between the outer side surfaces 121a and 122b and the inner side surfaces 121b and 122a and the first groove surfaces 131a and 131b and the second groove surfaces 142a and 142b, thereby suppressing the characteristic deterioration of the vibration element 10. Therefore, it is possible to easily cope with the downsizing of the vibration element 10 together with the fact that a high-precision exposure machine is unnecessary.

  (3) When the first protrusion 41 protrudes in the direction of 60 ± 5 degrees or 120 ± 5 degrees (preferably 60 degrees or 120 degrees) clockwise from the Y ′ axis around the Z ′ axis, the first protrusion 41 Since it consists of the X plane, etching residues are less likely to occur. This is because the X plane has a higher etching rate than the Y plane. Therefore, most of the crystal under the first protrusion 41 in this case disappears by under-etching in the wet etching step (FIG. 5 [5]).

  FIG. 7 is a plan view showing an etching suppression pattern in the manufacturing method of the second embodiment. Hereinafter, description will be given based on this drawing.

  In the manufacturing method of the second embodiment, the shape of the etching suppression pattern 50 is different from that of the first embodiment. The photosensitive resist film 33 left on the corrosion-resistant film 32 in the exposure and development process in the second embodiment has a planar shape shown in FIG. The etching suppression pattern 50 formed on the portions 130 and 140 that become the groove portions includes the first protrusion 41 that protrudes from the portions 131 and 141 that become the first groove surfaces toward the portions 132 and 142 that become the second groove surfaces, respectively. A second protrusion 52 protruding from the tip of one protrusion 41 along the longitudinal direction (± Y′-axis direction) of the vibrating arm portion. The second protrusion 52 includes a protrusion 521 protruding in the extending direction (Y′-axis direction) of the vibrating arm part and a protrusion 522 protruding in the opposite direction (−Y′-axis direction) of the extending direction of the vibrating arm part. Have. Other configurations, operations, and effects of the vibration element 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. Further, the present invention includes a combination of some or all of the configurations of the above-described embodiments as appropriate.

DESCRIPTION OF SYMBOLS 10 Vibration element 11 Base part 12a Vibrating arm part 121a Outer side surface 122a Inner side surface 13a Groove part 131a First groove surface 132a Second groove surface 14a Groove part 141a First groove surface 142a Second groove surface 12b Vibrating arm part 121b Inner side surface 122b Outer side surface 13b Groove 131b First groove surface 132b Second groove surface 14b Groove portion 141b First groove surface 142b Second groove surface 21a, 21b Excitation electrode 22a, 22b Electrode pad 23a, 23b Wiring pattern 24a, 24b Metal film for frequency adjustment

31 Crystal wafer 32 Corrosion-resistant film 33 Photosensitive resist film

130 Part to be a groove part 131 Part to be a first groove surface 132 Part to be a second groove surface 140 Part to be a groove part 141 Part to be a first groove surface 142 Part to be a second groove surface 40 Etching suppression pattern 41 First protrusion 42 Second protrusion 50 Etching suppression pattern 52 Second protrusion 521, 522 Projection

81 Width 90 of the portion to become the groove portion Protrusion (etching suppression pattern)
91 Projection length 92 Projection width 93 Distance

Claims (3)

A base portion, two vibrating arm portions extending in the same direction from the base portion, a first groove surface and a second groove portion provided on the vibrating arm portions along the longitudinal direction of the vibrating arm portion and facing each other. A method of manufacturing a crystal resonator element comprising a groove portion having a groove surface,
A corrosion-resistant film forming process for forming a corrosion-resistant film on the front and back of the quartz wafer;
A photosensitive resist film forming step of forming a photosensitive resist film on the corrosion-resistant film;
The photosensitive resist film is left as the etching resisting pattern in the portion serving as the groove, and the unnecessary photosensitive resist film is left as the groove and the portion serving as the two vibrating arms. An exposure development process for removing
A patterning step of creating a mask made of the corrosion resistant film by removing the corrosion resistant film not covered with the photosensitive resist film;
A wet etching step of wet etching the crystal wafer using the mask made of the corrosion-resistant film;
Including
The etching suppression pattern protrudes along the longitudinal direction of the vibrating arm portion from the first protrusion protruding from the portion serving as the first groove surface toward the portion serving as the second groove surface. Having a second protrusion,
A method for manufacturing a quartz crystal resonator element. The crystal axis passing through the crystal apex is the Z axis, the three crystal axes connecting the ridges in the plane perpendicular to the Z axis are the X axis, the X axis and the coordinate axis orthogonal to the Z axis are the Y axes, and these X The Y-axis and the Z-axis after rotation when a coordinate system consisting of an axis, a Y-axis, and a Z-axis is rotated within a range of ± 5 degrees around the X-axis, respectively, are a Y′-axis and a Z′-axis if you did this,
The extending direction of the two vibrating arm portions is the direction of the Y ′ axis, and the direction in which the two vibrating arm portions are arranged is the direction of the X axis,
The X-axis side when viewed from the center of the groove is the first groove surface, and the -X-axis side that is the opposite side of the X-axis when viewed from the center of the groove is the second groove surface,
The first protrusion protrudes in a direction of 60 ± 5 degrees or 120 ± 5 degrees clockwise from the Y ′ axis around the Z ′ axis.
A method for manufacturing a crystal resonator element according to claim 1. The second protrusion has a protrusion protruding in the extending direction of the vibrating arm part and a protrusion protruding in a direction opposite to the extending direction of the vibrating arm part.
A method for manufacturing a crystal resonator element according to claim 1 or 2.

Images