JP5377152B2 - Quartz crystal resonator and crystal resonator manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal vibrator for preventing unnecessary excitation of a vibration mode. <P>SOLUTION: This crystal vibrator includes: a crystal piece of a nearly-rectangular shape in a plan view formed into a flat form; drive electrodes arranged at the central parts of the upper and lower surfaces of the crystal piece and each formed of a conductive material; mounted electrodes arranged on the upper and lower surfaces of the crystal piece and electrically connected to the drive electrodes; and cross-sectionally V-shaped recessed parts arranged oppositely to each other between the drive electrodes and a longitudinal outer peripheral part of the crystal piece, and formed with surfaces stable against etching. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a crystal resonator and a method for manufacturing the crystal resonator.

  In clock pulse generation of digital equipment, wireless equipment, etc., a crystal resonator having a small temperature dependence of frequency is used.

  What is important in designing a crystal resonator is suppression of unnecessary vibration modes other than the desired vibration mode. For example, an AT-cut crystal resonator inputs an AC electrical signal having a frequency that substantially matches the natural vibration of a crystal piece to a drive electrode formed on the crystal piece, thereby generating a resonance phenomenon. Here, the vibration energy generated by the AC electrical signal input to the drive electrode leaks from the region where the drive electrode is formed toward the outer periphery of the crystal piece, and various unnecessary vibration modes such as the contour vibration of the crystal piece are generated. Excited. Therefore, the contour vibration is normally suppressed by performing bevel processing for chamfering the contour of the crystal piece by barrel polishing.

  However, when bevel processing is performed, there is a problem in that the external dimensions of the crystal piece vary, and it is difficult to obtain a crystal resonator having good vibration characteristics. In addition, barrel polishing for bevel processing reduces the polishing speed when the crystal unit is miniaturized, and the processing time for obtaining an appropriate chamfered shape becomes longer or the chamfered shape varies. Cause problems.

  Therefore, various methods have been proposed to solve these problems. For example, according to Patent Document 1, a crystal resonator having a structure that prevents vibration energy leaking from a drive electrode of the crystal resonator from propagating to a contour is provided.

  The crystal resonator configured as described above will be described with reference to FIGS. 13 and 14. 13 is a plan view of the crystal unit 101, and FIG. 14 is an enlarged view of a part of the cross section of the crystal unit 101 taken along line AA in FIG.

  The crystal unit 101 includes a crystal piece 102 having a substantially rectangular shape in plan view, a drive electrode 103 provided on the upper surface and the lower surface of the crystal piece 102 so as to face each other, and a mounting electrode 104 electrically connected to the drive electrode 103. And a concave portion 105 having a substantially V-shaped cross section formed between the short side of the crystal piece 102 and the drive electrode 103 and formed by digging the surface of the crystal piece 102 to a predetermined depth.

  Thereby, even if the vibration energy due to the AC electric signal input to the drive electrode 103 leaks in the direction of the short side of the crystal piece 102, the crystal resonator 101 blocks the propagation of the vibration energy by the recess 105. Therefore, vibration energy does not reach the short side of the crystal piece 102, and excitation of unnecessary vibration modes can be prevented.

  Further, the crystal unit 101 is formed with a recess 105 on the upper and lower surfaces of a crystal flat plate (not shown), and then divided into a large number of crystal pieces 102, and a drive electrode 103 and a mounting electrode 104 are formed on these crystal pieces 102. Manufactured.

  At that time, the recess 105 is formed by removing a predetermined position on the surface of the quartz plate using hydrofluoric acid or an aqueous ammonium fluoride solution. Quartz has a different etching rate depending on its crystal plane, and as etching progresses, a surface with a slow etching rate appears on the sidewall of the recess 105. When the slow surfaces meet each other, etching stops there, and the cross section of the recess 105 becomes substantially V-shaped as shown in FIG. Since the angle formed between the side wall of the recess 105 and the surface of the crystal flat plate is almost constant, the recess 105 can be set to a predetermined depth by appropriately setting the width of the opening of the recess 105.

  Thus, after forming the recessed part 105 on a crystal flat plate, a crystal flat plate is cut | disconnected using a wire saw etc., and it divides | segments into many crystal pieces 102. FIG. Thereafter, when the drive electrode 103 and the mounting electrode 104 are formed on the upper and lower surfaces of these crystal pieces 102, the crystal resonator 101 can be obtained.

JP2003-46366

  However, since the concave portion 105 is provided only between the short side of the crystal piece 102 and the drive electrode 103 in the above-described crystal resonator 101, the long side of the crystal piece 102 of vibration energy leaking from the drive electrode 103 is provided. Leakage in the direction cannot be prevented. Therefore, there is a problem that the leaked vibration energy reaches the long side of the crystal piece 102 and excites an unnecessary vibration mode.

  Further, in the method for manufacturing the crystal resonator 101 described above, it is necessary to divide the crystal piece 102 and form the recess 105 in separate steps. For this reason, it is difficult to accurately position the concave portion 105 with respect to the crystal piece 102, and there is a problem that the vibration characteristics of the crystal resonator 101 deteriorate. In addition, there is a problem that the number of man-hours increases and the cost increases.

  An object of the present invention has been made in view of the above circumstances, and is to provide a crystal resonator that prevents excitation of unnecessary vibration modes.

  In order to solve the above problems, the present invention provides the following means.

  A crystal resonator according to the present invention includes a substantially rectangular crystal piece in plan view formed in a flat plate shape, a drive electrode made of a conductive material disposed at the center of the upper surface and the lower surface of the crystal piece, A surface which is provided on the upper surface and the lower surface and is opposed to the mounting electrode electrically connected to the driving electrode in the previous period and between the driving electrode and the outer peripheral portion in the longitudinal direction of the crystal piece and is stable against etching. And a concave portion having a substantially V-shaped cross section formed in the above.

  Further, the crystal resonator according to the present invention is characterized in that the concave portion is disposed on an upper surface and a lower surface of the crystal piece.

  In the crystal resonator according to the present invention, since the concave portion is disposed so as to sandwich the drive electrode at a predetermined interval, propagation of vibration energy leaking from the drive electrode can be suppressed by the concave portion, which is unnecessary. The excitation of the vibration mode can be suppressed.

  The crystal resonator according to the present invention is characterized in that the concave portion is disposed substantially parallel to the longitudinal direction of the crystal piece, and the concave portion is disposed between the outer peripheral portion of the crystal piece and the drive electrode.

  In the crystal resonator according to the present invention, since the concave portion is disposed between the outer peripheral portion of the crystal piece and the drive electrode in substantially parallel to the longitudinal direction of the crystal piece, the crystal piece of vibration energy leaked from the drive electrode Propagation to the longitudinal contour of the film can be suppressed by the recess, and excitation of unnecessary vibration modes can be suppressed.

  Furthermore, the crystal resonator according to the present invention is characterized in that the concave portion is disposed substantially parallel to the short direction of the crystal piece, and the concave portion is disposed between the outer peripheral portion of the crystal piece and the drive electrode. .

  In the crystal resonator according to the present invention, since the concave portion is disposed between the outer peripheral portion of the crystal piece and the drive electrode substantially in parallel with the longitudinal direction and the short side direction of the crystal piece, vibration leaked from the drive electrode Propagation of energy to the contour of the crystal piece can be suppressed by the recess, and excitation of unnecessary vibration modes can be suppressed.

  The crystal resonator according to the present invention is characterized in that a plurality of recesses are arranged between the drive electrode and the outer peripheral part of the crystal piece, and the plurality of recesses are arranged in parallel to each other.

  In the crystal resonator according to the present invention, since a plurality of recesses are disposed between the outer peripheral portion of the crystal piece and the drive electrode, the propagation of the vibration energy leaking from the drive electrode to the contour of the crystal piece is provided. Can be sequentially suppressed, and excitation of unnecessary vibration modes can be suppressed.

  In addition, the crystal resonator according to the present invention is characterized in that the plurality of recesses are formed so as to be shallower as they are closer to the drive electrode and deeper as they are closer to the outer peripheral part of the crystal piece.

  The crystal resonator according to the present invention is formed such that a plurality of recesses are shallower as the drive electrode is closer and deeper as the crystal piece is closer to the outer peripheral portion. It can be further suppressed that the vibration energy reflected by the concave portion is returned to the region where the drive electrode is formed again to excite unnecessary vibration modes.

  In addition, the crystal resonator manufacturing method of the present invention includes a crystal piece separation opening that is an annular opening provided on the upper and lower surfaces of a crystal plate, and an opening disposed inside the inner periphery of the crystal piece separation opening. A protective film forming step of forming a protective film having a concave portion forming opening that is a portion, and a region exposed by immersing the quartz plate in an aqueous solution containing at least one of hydrofluoric acid or ammonium fluoride and exposing from the opening of the quartz plate A crystal piece and a concave portion forming step for removing the crystal piece and forming a concave portion, and an electrode forming step for forming a drive electrode made of a conductive thin film at the center of the upper and lower surfaces of the crystal piece with respect to the concave portion. It is characterized by that.

  In the method for manufacturing a crystal resonator according to the present invention, a protective film having a crystal piece separation opening and a recess forming opening is formed in the protective film forming step. In addition, in the crystal piece and concave portion forming step, a surface with a slow etching rate appears on the side wall of the concave portion, and when these surfaces meet each other, etching stops and a concave portion having a predetermined depth can be obtained. A crystal piece and a recess can be formed. Therefore, the position of the concave portion can be accurately arranged with respect to the crystal piece, and propagation of vibration energy leaking from the drive electrode can be efficiently suppressed by the concave portion.

  The method for manufacturing a crystal resonator according to the present invention is a method for manufacturing a crystal resonator, wherein the protective film forming step simultaneously forms a crystal piece separation opening and a recess formation opening at the same time.

  Since the crystal resonator manufacturing method according to the present invention simultaneously forms the crystal piece separation opening and the recess formation opening at the same time, the position of the recess with respect to the crystal piece is compared with the case of forming in a separate process. It can arrange | position with high precision and propagation | transmission of the vibration energy leaked from the drive electrode can be efficiently suppressed by a recessed part.

  Further, in the method for manufacturing a crystal resonator according to the present invention, the protective film forming step is arranged in such a manner that the first opening disposed substantially parallel to the longitudinal direction of the crystal piece and the short direction of the crystal piece. A protective film having a second opening is formed.

  In the method for manufacturing a crystal resonator according to the present invention, the first concave portion is disposed between the outer peripheral portion of the crystal piece and the drive electrode substantially in parallel with the longitudinal direction of the crystal piece, and substantially in the short direction of the crystal piece. Since the second concave portion is arranged in parallel, propagation of vibration energy leaking from the drive electrode to the contour of the crystal piece can be suppressed by the concave portion, and excitation of unnecessary vibration modes can be suppressed. .

  In addition, the method for manufacturing a crystal resonator according to the present invention is characterized in that a concave portion having a substantially V-shaped cross section is formed in the crystal piece and the concave portion forming step.

  In the method for manufacturing a crystal resonator according to the present invention, the surface having a slow etching rate appears as the side wall of the first recess and the second recess in the crystal piece and the recess forming step, and the etching stops when the side walls meet, If the opening widths of the first recess and the second recess are appropriately set, the first recess and the second recess having a desired depth can be formed in the same process.

  Further, the crystal resonator of the present invention is characterized in that the crystal piece and the recess form a side wall in parallel.

  In the crystal resonator according to the present invention, the crystal piece and the concave portion can be formed in the same process. Furthermore, since the crystal piece separation opening and the recess formation opening are arranged substantially in parallel, the side wall of the crystal piece and the recess can be formed in parallel. As a result, an accurate crystal resonator can be obtained, and the manufacturing process can be made more efficient.

  The crystal resonator and the method for manufacturing the crystal resonator according to the present invention can prevent excitation of unnecessary vibration modes and provide a crystal resonator having good vibration characteristics.

1 is a plan view showing a crystal resonator 1 according to a first embodiment. It is sectional drawing in the AA line of the crystal oscillator 1 of 1st embodiment shown in FIG. It is sectional drawing in the BB line of the crystal oscillator 1 of 1st embodiment shown in FIG. It is sectional drawing to which the 1st recessed part 5 of the crystal oscillator 1 of 1st embodiment shown in FIG. 2 was expanded. It is sectional drawing to which the 2nd recessed part 6 of the crystal oscillator 1 of 1st embodiment shown in FIG. 3 was expanded. It is sectional drawing which shows the manufacturing method of the crystal oscillator 1 of 1st embodiment shown in FIG. 1, Comprising: It is sectional drawing in the AA line of FIG. It is sectional drawing which shows the manufacturing method of the crystal oscillator of 1st embodiment shown in FIG. 1, Comprising: It is sectional drawing in the BB line of FIG. It is sectional drawing which shows the manufacturing method of the crystal oscillator 1 of 1st embodiment shown in FIG. 1, Comprising: It is sectional drawing in the AA line of FIG. It is a top view which shows the crystal oscillator 1 of 2nd embodiment. It is sectional drawing in the AA line of the crystal oscillator 1 of 2nd embodiment shown in FIG. It is sectional drawing in the BB line of the crystal oscillator 1 of 2nd embodiment shown in FIG. It is sectional drawing to which the 1st recessed part 5 of the crystal oscillator 1 of 2nd embodiment shown in FIG. 9 was expanded. It is sectional drawing to which the 2nd recessed part 6 of the crystal oscillator 1 of 2nd embodiment shown in FIG. 10 was expanded. FIG. 6 is a plan view showing a conventional crystal resonator 101. It is sectional drawing in the AA line of the conventional crystal oscillator 101 shown in FIG.

(First embodiment)
A first embodiment according to the present invention will be described below with reference to FIGS. 1 is a plan view showing a crystal resonator 1 according to the first embodiment, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. 4 is an enlarged cross-sectional view of the first opening 5 in FIG. 2, and FIG. 5 is an enlarged cross-sectional view of the second opening 5 in FIG.

  The crystal unit 1 is provided on a crystal piece 2 having a substantially rectangular shape in plan view formed in a flat plate shape, and an upper surface and a lower surface of the crystal piece 2, and is provided so as to face the crystal piece 2. The driving electrode 3 made of a conductive material, the mounting electrode 4 made of a conductive material connected to the driving electrode, and the upper surface and the lower surface of the crystal piece 2 are dug down until an etching stable surface is formed. The first recesses 5 arranged opposite to each other along the longitudinal direction of the crystal piece 2 with the drive electrode 3 interposed therebetween, and the upper surface and the lower surface of the crystal piece 2 are dug down until etching stable surfaces are formed. In addition, a second recess 6 connected to the first recess 5 is provided so as to face each other along the short direction of the crystal piece 2 with the drive electrode 3 interposed therebetween.

  As shown in FIG. 4, the first recess 5 is formed of a first side wall 7 that forms a specific angle θ <b> 1 with respect to the upper surface or the lower surface of the crystal piece 2 and a second side wall 8 that forms a specific angle θ <b> 2. Has been. The second recess 6 is formed of a third side wall 9 that forms a specific angle θ3 with respect to the upper surface or the lower surface of the crystal piece 2 and a fourth side wall 10 that forms a specific angle θ4. Here, assuming that the opening width of the first recess 5 is w1, the depth of the first recess 5 is d1, the opening width of the second recess 6 is w2, and the depth of the second recess 6 is d2. The following relationship is established between the two. A relational expression between the depth of the recess and the opening width is shown in Equation 1.

  Therefore, when the opening width w1 of the first recess 5 and the opening width w2 of the second recess 6 are appropriately set, the first recess 5 and the second recess 6 are set to predetermined depths d1 and d2, respectively. Can be formed.

  When the crystal piece 2 is made of AT cut crystal, the specific angle is such that the angle θ1 is an angle between 85 degrees and 95 degrees, and the angle θ2 is an angle between 50 degrees and 60 degrees. Further, the angle θ3 is an angle between 10 degrees and 30 degrees, and the angle θ4 is an angle between 10 degrees and 30 degrees.

  In the crystal resonator 1 configured as described above, when an AC electric signal is applied to the mounting electrode 4, the crystal piece 2 sandwiched between the drive electrodes 3 vibrates. When the resonance frequency of the crystal piece 2 and the frequency of the AC electric signal applied to the mounting electrode 4 coincide, a resonance phenomenon occurs, and the impedance between the drive electrodes 3 decreases. In this way, the crystal resonator 1 can be used as a resonator device.

  At this time, energy that vibrates the crystal piece 2 leaks from the region sandwiched between the drive electrodes 3 on the upper and lower surfaces of the crystal piece toward the outer periphery of the crystal piece 2. However, since the drive electrode 3 is sandwiched between the first concave portion 5 and the second concave portion 6, the vibration energy leaks over the first concave portion 5 and the second concave portion 6 to the outer peripheral portion of the crystal piece 2. Without being confined in the region sandwiched between the recesses on the upper and lower surfaces. It is confined in the region sandwiched by the recesses on the upper and lower surfaces and the drive electrodes 3 on the upper and lower surfaces. Due to the energy confinement phenomenon realized in this way, the crystal piece 2 can be vibrated efficiently, and an accurate crystal resonator can be obtained.

  Next, a manufacturing method of the crystal resonator 1 configured as described above will be described with reference to FIGS.

  6 shows a cross-sectional view taken along line AA in FIG. 1, and FIG. 7 shows a cross-sectional view taken along line BB in FIG. Further, although the crystal unit 1 can be manufactured individually, in the present embodiment, a method of forming a plurality of crystal units on the crystal plate 11 will be described.

  First, a protective film forming step is performed. FIG. 6A and FIG. 7A show the process. On the upper and lower surfaces of the quartz plate 11, a protective film 12 having a quartz piece separation opening 13 and a recess forming opening made up of a first opening 14 and a second opening 15 is formed.

  As the material of the protective film, for example, a material having corrosion resistance against hydrofluoric acid such as a photoresist, gold, or molybdenum is used.

  The protective film 12 surrounded by the crystal piece separation opening 13 has a plan view shape substantially coincident with the crystal piece 2. The first opening 14 has a plan view shape that substantially matches the first recess portion 5, and the second opening portion 15 has a plan view shape that substantially matches the second recess portion 6.

  An example of a detailed formation process of the protective film 12 will be described below.

  When the protective film 12 is made of a thin film such as gold or molybdenum, a thin film made of gold or molybdenum or the like that is the material of the protective film 12 is formed on the surface of the quartz plate 11 by sputtering or vapor deposition. Since gold or the like has weak adhesion to the quartz surface and is easily peeled off, a thin film that improves the adhesion such as chrome is formed on the surface of the quartz plate 11 in advance, and then a thin film that becomes the material of the protective film 12 is deposited. Also good.

  Next, an etching mask made of a photoresist (not shown) is formed on the formed thin film. A predetermined portion of the etching mask is removed by using a lithography technique, and a portion of the thin film that becomes the material of the protective film 12 exposed by the removal is etched using a predetermined etchant to obtain a protective film 12 having a predetermined shape. When the protective film 12 is made of gold, for example, an potassium iodide iodide aqueous solution or aqua regia can be selected as an etchant.

  Note that the protective film can be formed using only a photoresist, gold, or molybdenum. In the case where the protective film is formed using only gold or molybdenum, for example, a method of forming a thin film in an arbitrary region by performing film formation such as sputtering using a shadow mask can be used.

  In addition, when more precise patterning is required, electron beam exposure using an EPL (Electron projection lithography) mask such as a stencil mask can be used instead of photolithography.

  Next, a crystal piece and a recess forming step are performed. FIG. 6B and FIG. 7B show the process. When the crystal flat plate 11 on which the protective film 12 is formed is immersed in an aqueous solution containing hydrofluoric acid, ammonium fluoride, or the like, it is exposed at the bottom of the crystal piece separation opening 13, the first opening 14, and the second opening 15. The crystal plate 11 is etched.

  During the etching process, the first recess 5 is formed in the first opening 14 and the second recess 6 is formed in the second opening 15. As described above, the first recess 5 is formed of the first side wall 7 and the second side wall 8 that form specific angles with respect to the upper surface and the lower surface of the crystal plate 11, and the second recess 6 is the crystal plate. 11 is formed of a third side wall 9 and a fourth side wall 10 that form specific angles with respect to the upper surface and the lower surface.

  The reason why the first side wall 7, the second side wall 8, the third side wall 9 and the fourth side wall 10 are formed at specific angles with the upper surface or the lower surface of the crystal piece 2 will be described below.

  Quartz is etched by an aqueous solution containing hydrofluoric acid or ammonium fluoride, but the etching rate differs for each crystal plane. In particular, etching hardly proceeds on a stable surface. In the AT-cut quartz, the first side wall 7 to the fourth side wall 10 are stable surfaces against an aqueous solution containing hydrofluoric acid or ammonium fluoride. Etching proceeds while forming corners. Then, when the first side wall 7 and the second side wall 8, and the third side wall 9 and the fourth side wall 10 meet each other, only the surface that is stable to etching is exposed. Then, the first recess 5 and the second recess 6 having a cross section as shown in FIGS. 4 and 5 are formed. As described above, when the widths of the first opening 14 and the second opening 15 are appropriately set, the etching is stopped when the first recess 5 and the second recess 6 reach a predetermined depth. be able to.

  Thereafter, when the etching is continued, as shown in FIGS. 6C and 7C, the region exposed from the crystal piece separation opening 13 of the crystal plate 11 is completely removed, and the crystal piece 2 is removed. It is formed. The side wall of the crystal piece 2 has a shape reflecting the difference in the etching rate of the crystal plane as described above. For example, in FIG. 6C, a plane parallel to the second side wall 8 appears as the side wall of the crystal piece 2, and in FIG. 7C, a plane parallel to the third side wall 9 and the fourth side wall 10 is a crystal. The side wall of the piece 2 is formed. In addition, the shape of the side wall of the crystal piece 2 shown in the present embodiment is merely an example. For example, in the cross section taken along line AA in FIG. 1, when the protective film 12 is disposed on both sides of the quartz plate 11 as shown in FIG. 8, the side wall of the quartz piece 2 is formed from a plane parallel to the first side wall 7. Similarly, the cross section taken along the line BB in FIG. 1 is changed so that the side wall of the crystal piece 2 becomes parallel to one of the third side wall 9 and the fourth side wall 10 by changing the arrangement of the protective film 12. Can be formed.

  Next, a protective film removing step is performed. As shown in FIGS. 6D and 7D, the protective film 12 is removed. When the protective film 12 is made of a photoresist, for example, an organic solvent, an acidic aqueous solution such as nitric acid or sulfuric acid can be used. In the case where the protective film 12 is made of gold, for example, an iodine iodine iodide aqueous solution or aqua regia can be selected.

  Next, an electrode formation process is performed. FIG. 6E and FIG. 7E show the process. A conductive thin film having a predetermined shape is formed on the upper and lower surfaces of the crystal piece 2 to form the drive electrode 3 and the mounting electrode 4.

  As a method of forming the drive electrode 3 and the mounting electrode 4, for example, a method of obtaining a predetermined shape using lithography and etching after forming a conductive thin film on the entire surface of the crystal piece 2 can be used. In addition, after forming a protective film (not shown) that protects areas other than the regions where the drive electrode 3 and the mounting electrode 4 are formed in advance by lithography, a conductive thin film is formed, and the protective film is removed to obtain a predetermined shape. A method is also available. In addition, a method of obtaining a predetermined shape by forming a conductive thin film through a shadow mask having a predetermined shape can be selected.

  Various materials can be selected for the conductive thin film that forms the drive electrode 3 and the mounting electrode 4. However, for example, when gold is selected, it is difficult to react with oxygen in the atmosphere. The vibration characteristics can be stabilized. Also, since gold has a higher density than other materials, it becomes a weight for the crystal unit 1 and lowers its resonance frequency. Therefore, after the drive electrode 3 and the mounting electrode 4 are formed, the drive electrode 3 is evaporated by a predetermined amount by irradiation with an ion beam or a laser, and the frequency of the crystal unit 1 can be adjusted.

  When the protective film is formed of gold in the protective film forming step, the protective film can be used as it is as the drive electrode 3 and the mounting electrode 4 without removing the protective film. At this time, it is desirable to remove the protective film other than the portions of the drive electrode 3 and the mounting electrode 4.

  When a large number of crystal pieces are formed from a crystal flat plate, a part of the crystal piece separation opening may be covered with a protective film so as to connect adjacent crystal pieces in the protective film forming step. Thereby, a large number of crystal pieces are held on the crystal flat plate. And a drive electrode and a mounting electrode can be formed collectively on a quartz plate, and a crystal piece can be isolate | separated collectively after that. By the above, each process can be performed accurately and collectively, and a manufacturing process can be simplified.

  As described above, according to the present embodiment, the crystal piece 2 formed in a flat plate shape is provided on the upper surface and the lower surface of the crystal piece 2 and is provided so as to face each other with the crystal piece 2 interposed therebetween. A driving electrode 3 made of a conductive material, a mounting electrode 4 made of a conductive material connected to the driving electrode, and a predetermined depth is dug into the upper and lower surfaces of the crystal piece 2, and the driving electrode 3 is sandwiched between them. The first concave portion 5 arranged along the longitudinal direction of the crystal piece 2 and a predetermined depth are provided in the upper and lower surfaces of the crystal piece 2, and the short side of the crystal piece 2 with the drive electrode 3 interposed therebetween The crystal resonator 1 including the second concave portion 6 arranged along the direction and connected to the first concave portion 5 can be obtained.

  In the crystal resonator 1 configured as described above, since the drive electrode 3 is sandwiched between the first recess 5 and the second recess 6, the vibration energy input to the drive electrode 3 is the first recess. Without being leaked to the outer peripheral portion of the crystal piece 2 beyond the 5 and the second recess 6, it is confined around the region sandwiched between the drive electrodes 3. Due to the energy confinement phenomenon realized in this way, the crystal piece 2 can be vibrated efficiently, and an accurate crystal resonator can be obtained.

  In addition, according to the manufacturing method of the present embodiment, the first recess 5 and the second recess 6 are appropriately etched so that the etching stops at a predetermined depth. The 1st recessed part 5 and the 2nd recessed part 6 can be formed in the process same as the process to form. Therefore, the number of steps can be reduced, and the shape of the crystal piece 2 and the first concave portion 5 and the second concave portion 6 can be arranged and formed on the same photomask. On the other hand, the first concave portion 5 and the second concave portion 6 can be arranged with high positional accuracy, and an ideal energy confinement phenomenon can be realized. As a result, an efficient crystal resonator can be obtained.

In this embodiment, the example in which the first recess 5 and the second recess 6 are provided so as to surround the drive electrode 3 has been described. However, for example, only the first recess 5 or only the second recess 6 is provided. A crystal resonator may be used. In this case, the efficiency of the energy confinement phenomenon is slightly inferior to that of the present embodiment, but the energy is efficiently transferred to the region sandwiched between the drive electrodes 3 as compared with the case where the first recess 5 and the second recess 6 are not provided. Can be confined. Further, the crystal unit can be reduced in size.
(Second embodiment)
Next, a second embodiment according to the present invention will be described with reference to FIGS. In the second embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  9 is a plan view showing the crystal resonator 1 according to the second embodiment, FIG. 10 is a sectional view taken along the line AA in FIG. 9, and FIG. 11 is a sectional view taken along the line BB in FIG. 12 shows an enlarged cross-sectional view of the first opening 5 in FIG. 10, and FIG. 13 shows an enlarged cross-sectional view of the second opening 6 in FIG.

  As shown in FIG. 9, the crystal resonator 1 according to the present embodiment is provided with a plurality of first recesses 5 and a plurality of second recesses 6 on the upper surface and the lower surface of the crystal piece 2. A plurality of first recesses 5 and second recesses 6 are provided between the outer peripheral portion of the crystal piece 2 and the drive electrode 3. In this embodiment, three first recesses 5 and three second recesses 6 are provided. However, the number of the recesses is not limited to three, and it is sufficient that at least two or more recesses are provided.

  As shown in FIGS. 12 and 13, the first concave portion 5 and the second concave portion 6 are arranged so as to be shallower as they are closer to the drive electrode 3 and become deeper as they approach the outer peripheral portion of the crystal piece 2.

  In the crystal resonator 1 configured as described above, vibration energy input to the drive electrode 3 leaks toward the outer peripheral portion of the crystal piece 2. However, since the drive electrode 3 is sandwiched between the first concave portion 5 and the second concave portion 6, the vibration energy leaks over the first concave portion 5 and the second concave portion 6 to the outer peripheral portion of the crystal piece 2. Without being confined around the region sandwiched between the drive electrodes 3. Due to the energy confinement phenomenon realized in this way, the crystal piece 2 can be vibrated efficiently, and an accurate crystal resonator can be obtained. Further, since the vibration energy is sequentially cut off by the plurality of first recesses 5 and second recesses 6 provided, the efficiency is higher than in the case where the first recesses 5 and the second recesses 6 are one by one. Energy confinement. Further, the plurality of first recesses 5 and second recesses 6 are provided so as to gradually become deeper from the side closer to the drive electrode 3 toward the outer peripheral part of the crystal piece 2. Therefore, the vibration energy that is prevented from leaking out by the first recess 5 and the second recess 6 is reflected and returned to the region sandwiched between the drive electrodes 3 of the crystal piece 2 to excite unnecessary vibration modes. Can be prevented.

  As shown in FIGS. 12 and 13, the plurality of first recesses 5 and second recesses 6 that have a plurality of openings gradually increase in width from the side closer to the drive electrode 3 toward the outer periphery of the crystal piece 2. It is formed to become. The opening widths are w1, w2, and w3 and the depths are d1, d2, and d3 in order from the first recess 5 closer to the drive electrode 3. In addition, the opening widths are w4, w5, and w6 and the depths are d4, d5, and d6 in order from the second recess 6 closer to the drive electrode 3. As described in the first embodiment, the first concave portion is formed by removing the surface of the crystal piece 2 using an aqueous solution containing hydrofluoric acid or ammonium fluoride. A surface having a slow etching rate appears on the side wall of one recess 5, and the angles θ 2 formed by the side wall and the upper surface of the crystal piece 2 are all substantially equal. Similarly, for the second recess 6, a surface with a slow etching rate appears as a side wall, and the angles θ 3 and θ 4 formed by the side wall and the upper surface of the crystal piece 2 are substantially equal.

  When forming the first concave portion 5 and the second concave portion 6, when sidewalls having a low etching rate meet each other, the etching stops there. Therefore, there is a relationship between the opening width and the depth as follows. If the opening widths of the first recess 5 and the second recess 6 are set, the etching can be stopped at a predetermined depth. The relational expression between the opening width and depth of each recess is shown in Equation 2.

  In this embodiment, since it is set as w1 <= w2 <= w3, the recessed part of the depth of d1 <= d2 <= d3 can be formed. Similarly, since it is set as w4 <= w5 <= w6, the recessed part of the depth of d4 <= d5 <= d6 can be formed.

  In the crystal resonator 1 configured in this manner, the first concave portion 5 and the second concave portion 6 stop etching at a predetermined depth by appropriately setting the opening width thereof. A plurality of first recesses 5 and second recesses 6 having different depths can be formed in the same step as the step of forming 2. Therefore, the number of steps can be reduced, and the shape of the crystal piece 2 and the first concave portion 5 and the second concave portion 6 can be arranged and formed on the same photomask. On the other hand, the 1st recessed part 5 and the 2nd recessed part 6 can be arrange | positioned with sufficient positional accuracy. As a result, since an energy confinement phenomenon can be ideally realized, an efficient crystal resonator can be obtained.

DESCRIPTION OF SYMBOLS 1 Crystal oscillator 2 Crystal piece 3 Drive electrode 4 Mounting electrode 5 1st recessed part 6 2nd recessed part 11 Crystal flat plate 12 Protective film 13 Crystal piece isolation | separation opening part 14 1st opening part 15 2nd opening part 101 Conventional Crystal resonator 102 Crystal piece 103 Drive electrode 104 Mounting electrode 105 Recess

Claims (14)

A substantially rectangular crystal piece in plan view formed in a flat plate shape;
A drive electrode made of a conductive material disposed in the center of the upper and lower surfaces of the crystal piece;
A mounting electrode provided on the upper and lower surfaces of the crystal piece and electrically connected to the drive electrode;
The drive electrode and the crystal piece are disposed in opposition to each other in the longitudinal direction, and are formed with a stable surface against etching, and have a substantially V-shaped cross section having a side wall parallel to the side wall of the crystal piece . A recess,
A crystal resonator characterized by comprising:   2. The crystal resonator according to claim 1, wherein the concave portion is further disposed so as to be opposed to the drive electrode of the crystal piece and an outer peripheral portion in a short direction.   The quartz resonator according to claim 2, wherein the recess is further annularly arranged.   4. The crystal resonator according to claim 1, wherein a plurality of the concave portions are arranged between an outer peripheral portion of the crystal piece and the drive electrode. 5.   5. The crystal resonator according to claim 4, wherein the plurality of concave portions are formed so as to be shallower as being closer to the drive electrode and deeper as being closer to an outer peripheral portion of the crystal piece.   The crystal unit according to claim 1, wherein the concave portion is disposed on an upper surface and a lower surface of the crystal piece.   The crystal unit according to claim 6, wherein the concave portion is disposed in parallel to an outer peripheral portion of the crystal piece. In a method for manufacturing a crystal resonator, comprising: a crystal piece formed in a flat plate shape; and a drive electrode made of a conductive material disposed in the center of the upper surface and the lower surface of the crystal piece.
A protective film forming step of forming a protective film having a crystal piece separation opening and a recess formation opening on the upper and lower surfaces of the crystal plate;
The quartz crystal flat plate located in the quartz piece separation opening and the recess forming opening is removed, and the quartz piece, the drive electrode, and a longitudinally outer peripheral portion of the quartz piece are arranged to face each other, Forming a recess having a substantially V-shaped cross section having a side wall parallel to the side wall of the crystal piece formed on a surface stable to etching ;
An electrode forming step of forming the drive electrodes made of a conductive thin film in the central portion of the upper and lower surfaces of the crystal piece,
A method for manufacturing a crystal resonator, comprising:   9. The method for manufacturing a crystal resonator according to claim 8, wherein in the protective film forming step, the crystal piece separation opening and the recess formation opening are formed simultaneously.   The step of forming the crystal piece and the recess includes immersing the crystal plate in an aqueous solution containing at least one of hydrofluoric acid or ammonium fluoride to form the crystal piece and the recess in the opening of the crystal plate. The method for manufacturing a crystal resonator according to claim 9, wherein:   The method for manufacturing a crystal resonator according to claim 10, wherein the recess forming opening includes an opening disposed substantially parallel to a longitudinal direction of the crystal piece. The recess forming opening is a first opening disposed substantially parallel to the longitudinal direction of the crystal piece,
The method for manufacturing a crystal resonator according to claim 11, further comprising: a second opening disposed substantially parallel to a short direction of the crystal piece.   The method for manufacturing a crystal resonator according to claim 9, wherein the protective film forming step forms a protective film having a plurality of the concave portion forming openings.   The method for manufacturing a crystal resonator according to claim 13, wherein in the protective film forming step, the recess forming opening having a wider width is formed closer to the outer peripheral portion of the crystal piece.

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