JP5023734B2 - Method for manufacturing piezoelectric vibrating piece and piezoelectric vibrating element - Google Patents

Description

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

2. Description of the Related Art Conventionally, in a car navigation device, an inertial sensor such as a gyro sensor (angular velocity sensor) or an acceleration sensor for detecting acceleration or angular velocity applied to the vehicle in order to independently determine the moving direction and moving distance of the vehicle is mounted. ing. In recent years, some mobile terminal devices such as mobile computers are equipped with an acceleration sensor that detects acceleration at the time of dropping in order to protect a built-in hard disk or the like when it is accidentally dropped from a high place. is there. As a detection mechanism for detecting the angular velocity and acceleration of such a gyro sensor or acceleration sensor, a MEMS (Micro Electro Mechanical Systems) sensor manufactured by a semiconductor process is well known.
However, the MEMS sensor has a defect that the frequency-temperature characteristic is poor and a stable frequency cannot be obtained. Therefore, as a gyro sensor that does not have the above-described drawbacks, for example, a sensor using a tuning fork type pressure vibration element has been proposed.

FIG. 8 is a perspective view showing a schematic configuration of a conventional tuning fork type crystal vibrating element.
The tuning-fork type crystal vibrating element 100 shown in FIG. 8 is cut out from a single crystal of crystal so that the X axis (electric axis), the Y axis (mechanical axis), and the Z axis (optical axis) are in the directions shown in the figure. It is formed of a so-called quartz Z plate. The tuning fork type crystal resonator element 100 includes a base 101 and two vibrating arms 102 and 103 formed so as to protrude from the base 101 in the Y-axis direction. Drive electrodes 104 and 105 are formed on both main surfaces and side surfaces of the two vibrating arms 102 and 103. In the tuning-fork type crystal resonator element 100 configured as described above, an electric field is generated in each of the vibrating arms 102 and 103 by applying a driving voltage to the driving electrodes 104 and 105 of the vibrating arms 102 and 103 to thereby generate each vibrating arm. 102 and 103 are bent and vibrated. Note that there is Patent Document 1 as a prior document of a tuning fork type crystal resonator.
JP-A-2005-333683

By the way, when manufacturing a quartz crystal vibrating piece used for the tuning fork type quartz vibrating element as described above, it is desirable to cut a large number of vibrating pieces from, for example, one quartz substrate from the viewpoint of production efficiency. However, when the size (aperture) of the quartz substrate is increased, the strength of the quartz substrate is reduced, which makes it difficult to handle at the time of manufacture.
On the other hand, when the thickness of the quartz substrate is increased to increase the strength of the quartz substrate, it takes time to etch the quartz substrate into a tuning fork type, resulting in an increase in manufacturing cost.

In addition, when wet etching is performed on quartz, it has a so-called anisotropy in which the etching rate varies depending on the crystal direction. For this reason, when the quartz substrate is thickened, there is a problem that an ideal outer shape cannot be formed due to the influence of anisotropy.
The present invention has been made in view of the above-described problems, and provides a method for manufacturing a piezoelectric vibrating piece that is easy to handle during manufacturing. Also provided is a method of manufacturing a piezoelectric vibrating piece that can be realized at low cost. Also provided is a method of manufacturing a piezoelectric vibrating piece with little influence of anisotropy. Furthermore, a piezoelectric vibrating element using these piezoelectric vibrating pieces is provided.

In order to solve the above-described problems, the piezoelectric vibrating piece manufacturing method of the present invention includes a bonding step of bonding a piezoelectric substrate and a base substrate having an etching rate different from that of the piezoelectric substrate, and a piezoelectric substrate after the bonding step. A polishing step for polishing the base substrate, a base etching step for etching the base substrate after the bonding step, and a piezoelectric etching step for etching the piezoelectric substrate after the polishing step .
According to the present invention, even when the piezoelectric substrate is thinly polished, the piezoelectric substrate is supported by the bonded base substrate, so that the strength of the piezoelectric substrate can be maintained. Therefore, even when the diameter of the piezoelectric substrate is increased, the piezoelectric substrate can be easily handled during manufacturing.

Further, since the number of piezoelectric vibrating pieces that can be cut out from one piezoelectric substrate can be increased by increasing the diameter of the piezoelectric substrate, the manufacturing cost of the piezoelectric vibrating piece can be reduced.
In addition, since the piezoelectric substrate can be thinned, the processing time for processing the piezoelectric substrate into, for example, a tuning fork type outer shape by etching processing can be shortened, and the manufacturing cost can be reduced also in this respect.
Furthermore, since the influence of anisotropic etching is reduced by making the piezoelectric substrate thinner, the outer shape accuracy when the piezoelectric substrate is processed into a tuning fork type outer shape can be increased.

The method for manufacturing a piezoelectric vibrating piece according to the present invention is characterized in that after the base substrate is etched by the base etching step, the piezoelectric substrate is etched by the piezoelectric etching step.
In the method for manufacturing a piezoelectric vibrating piece according to the present invention, in the base etching process, in a plan view, at least the base substrate that overlaps the region where the vibrating arm of the piezoelectric substrate is formed is removed, and a part of the base substrate is removed. And a step of etching the piezoelectric substrate. The piezoelectric etching step includes a step of etching the piezoelectric substrate in a state where a part of the base substrate is bonded to the piezoelectric substrate.
According to the present invention, the base substrate can function as a reinforcing plate that reinforces the piezoelectric substrate.

The method for manufacturing a piezoelectric vibrating piece according to the present invention is characterized in that after the piezoelectric substrate is etched by the piezoelectric etching step, the base substrate is etched by the base etching step.
In the method for manufacturing a piezoelectric vibrating piece according to the present invention, the base etching step forms a concave opening in the base substrate.
According to the present invention, the base substrate can be used as a package of a piezoelectric substrate, for example.

The piezoelectric vibration element of the present invention is manufactured by the method of manufacturing a piezoelectric vibration piece of the present invention, and is configured by using a piezoelectric vibration piece having a thickness direction formed along an electric axis.
According to the present invention as described above, a strong electric field can be applied in the electric axis direction, and a piezoelectric vibration element having a small crystal impedance value can be realized.

The piezoelectric vibrating element of the present invention is formed on each side edge of the surface of the vibrating arm of the piezoelectric vibrating piece and the vibrating arm of the piezoelectric vibrating piece, respectively, so as to have different polarities. A first electrode, a piezoelectric thin film formed on the surface of the first electrode, and a second electrode formed on the surface of the piezoelectric thin film so as to be paired with the first electrode across the piezoelectric thin film, It is characterized by having.
According to the present invention as described above, the weight of the piezoelectric vibrating piece can be reduced, so that driving by the piezoelectric thin film formed on the vibrating arm is facilitated, and a piezoelectric vibrating element having a small crystal impedance value can be realized. Become.

Hereinafter, an embodiment of a method of manufacturing a piezoelectric vibrating piece according to the present invention will be described with reference to the drawings.
1 and 2 are diagrams showing an example of a manufacturing process of a piezoelectric vibrating piece according to an embodiment of the present invention.
In this case, first, in the bonding step S1 shown in FIG. 1A, for example, a wafer-like quartz substrate (piezoelectric substrate) 1 and a wafer-like silicon substrate (base substrate) 2 serving as a base are directly bonded. Paste together. In this embodiment, the silicon substrate 2 will be described as an example of the base substrate. However, the base substrate can be applied as long as the substrate has a different etching rate from that of the quartz substrate 1, for example, a glass substrate or a quartz crystal having a different cutting angle. A substrate or the like can be used. The direct bonding is, for example, directly bonding the quartz substrate 1 and the silicon substrate 2 without using an adhesive. For example, the quartz crystal is formed using a mixed solution of acid such as hydrogen peroxide or ammonia and pure water. Cleaning and surface treatment of the contact surface between the substrate 1 and the silicon substrate 2 are performed. The substrate surface that has been subjected to such a treatment exhibits a property (hydrophilicity) in which water is very well adapted and spreads on the substrate surface (hereinafter referred to as hydrophilic treatment). Thereafter, by superimposing and bonding the surfaces subjected to the hydrophilic treatment, the surfaces of the substrates can be automatically bonded by a force (attractive force between the surfaces) that attracts each other.

Next, in the polishing step S2 shown in FIG. 1 (b), the bonded quartz substrate 1 side surface is polished to thin the quartz substrate 1 of, for example, about 100 μm to about 20 μm.
Next, in a base etching step S3 shown in FIG. 1C, only a desired position of the silicon substrate 2 is wet-etched or dry-etched by masking the silicon substrate 2 or the like. At this time, since the crystal substrate 1 and the silicon substrate 2 have different etching rates, the crystal substrate 1 becomes an etch stop. For example, as shown in an enlarged view in FIG. The through hole 3 can be formed.

Thereafter, in the crystal etching step S4 shown in FIG. 2, the crystal substrate 1 is etched into a tuning fork type outer shape. Thereby, the tuning-fork type crystal vibrating piece 4 as shown in an enlarged manner in FIG. 2 can be manufactured. Note that the resonance frequency of the crystal resonator element using the tuning fork type crystal resonator element 4 is preferably set to be 32.768 × N (N is a positive integer) kHz.
If the tuning fork type crystal vibrating piece 4 is manufactured in this way, even when the quartz substrate 1 is thinly polished, the quartz substrate 1 is supported by the bonded silicon substrate 2, so that the strength of the quartz substrate 1 can be maintained. it can. Therefore, even when the diameter of the quartz substrate 1 is increased, the quartz substrate 1 can be easily handled during manufacturing.

In addition, since the number of tuning fork type crystal vibrating pieces 4 that can be cut out from one quartz substrate can be increased by increasing the diameter of the quartz substrate 1, the manufacturing cost of the tuning fork type crystal vibrating piece 4 can be reduced. .
In addition, since the quartz substrate 1 can be thinned, the processing time for processing the quartz substrate 1 into, for example, a tuning fork type outer shape by etching can be shortened, and the manufacturing cost can be reduced also in this respect.
Furthermore, since the thickness of the quartz substrate 1 is reduced, the influence of anisotropic etching is reduced, so that the outer shape accuracy when the quartz substrate 1 is processed into, for example, a tuning fork type outer shape can be increased.

Furthermore, conventionally, since the thickness of the quartz substrate 1 is as thick as about 100 μm, for example, wet etching with a high etching rate (high etching rate) was performed when the quartz substrate 1 was etched. In this embodiment, since the thickness of the quartz substrate 1 can be reduced to about 20 μm, even when dry etching with a low etching rate (low etching rate) is performed, the same production efficiency as before can be ensured. . It is also possible to form the quartz substrate 1 in a tuning fork shape by laser processing.
In the present embodiment, after the silicon substrate 2 is etched in the base etching step S3, the quartz substrate 1 is etched in the quartz etching step S4. In this way, the silicon substrate 2 can function as a reinforcing plate that reinforces the quartz crystal substrate 1.

  In the manufacturing process described above, the silicon substrate 2 is etched by the base etching process S3, and then the crystal substrate 1 is etched by the crystal etching process S4. However, the base etching process S3 and the crystal etching process S4 are performed. The order may be changed. In other words, after the quartz substrate 1 is etched by the quartz etching process, the silicon substrate 2 may be etched by the base etching process. In this case, the silicon substrate 2 is selectively etched from above the quartz substrate 1 formed in a tuning fork shape, so that the top view shown in FIG. 3A and the AA sectional view shown in FIG. Thus, the concave opening 5 can be formed in the silicon substrate 2. In this way, the silicon substrate 2 can be used as a package for the crystal substrate 1, for example.

In the present embodiment described so far, quartz has been described as an example of the substrate material of the tuning fork type piezoelectric vibrating piece. However, this is only an example, and, for example, PZT (lead zirconate titanate) piezoelectric Ceramic, langasite (La ₃ Ca ₅ SiO ₁₄ ), gallium phosphate (GaPo ₄ ), lithium tantalate (LiTaO ₃ ), BNT-BT-ST lead-free piezoelectric ceramic, or the like can be used.

  In JP-A-7-46072, a quartz plate is directly bonded to a thick substrate to enable polishing with a thick carrier, and the quartz plate is polished to 15 μm or less and has a fundamental frequency of 100 MHz or more. A method of manufacturing a crystal resonator that produces a child with a high yield is disclosed. Japanese Patent Application Laid-Open No. 7-86106 discloses a method of manufacturing a composite substrate material for obtaining a bonded wafer that does not warp even when substrates having different thermal expansion coefficients are directly bonded to each other. Japanese Patent Laid-Open No. 9-92895 discloses a piezoelectric element in which a groove is formed in at least one of two substrates to be directly bonded, thereby relaxing the thermal stress at the bonding interface and preventing problems such as peeling of the composite substrate, and its manufacture. A method is disclosed. However, these technologies are designed to reduce the thickness of the quartz plate by attaching a quartz substrate to a thick substrate in order to increase the frequency of the thickness-shear vibrator. This is different from the present invention aimed at reducing the cost of the vibrator.

Next, an example of the structure of a crystal resonator element using the tuning-fork type crystal resonator element manufactured as described above will be described.
4A and 4B are diagrams showing the configuration of the tuning-fork type crystal resonator element according to the present embodiment. FIG. 4A is a perspective view, and FIG. 4B is a cross-sectional view taken along line BB shown in FIG. In the tuning-fork type crystal vibrating element 10 shown in FIG. 4, the silicon substrate 2 serving as a base is not shown.
A tuning-fork type crystal vibrating piece 11 of the tuning-fork type crystal vibrating element 10 shown in FIG. 4 has a base portion 16 and two vibrating arms 12 and 13 formed so as to protrude from the base portion 16. As shown in FIG. 4B, different drive electrodes 14 and 15 are formed on both main surfaces of the two vibrating arms 12 and 13 so as to face each other. In this case, as shown in FIG. 4A, the thickness direction of the tuning-fork type crystal vibrating piece 11 is the X axis (electric axis), the protruding directions of the vibrating arms 12 and 13 are the Y axis (mechanical axis), and the vibrating arm. The tuning-fork type crystal vibrating piece 11 is formed so that the direction orthogonal to 12 and 13 is the Z-axis (optical axis). That is, the tuning fork type crystal resonator element 10 shown in FIG. 4 has a tuning fork type crystal resonator element 11 formed by using a so-called X plate called a “X plate” whose plate thickness direction is the X axis (electric axis). There is a feature.

Here, the structure of the tuning fork type crystal resonator element 10 of the present embodiment is compared with the structure of a conventional tuning fork type crystal resonator element. FIG. 6 is a view showing an XX cross section of the conventional tuning-fork type crystal vibrating element 100 as shown in FIG.
In the conventional tuning fork type crystal resonator element 100 shown in FIG. 6, drive electrodes 104 and 105 are formed on both main surfaces and side surfaces of two vibrating arms 102 and 103, respectively. In such a conventional tuning fork type quartz vibrating element 100, the outer shape of the tuning fork type quartz vibrating piece is formed by wet etching. Therefore, from the viewpoint of production efficiency, the Z-axis (optical axis), which normally has a high etching rate, is thick. A quartz substrate (so-called Z plate) cut out in the direction is used. However, when the Z plate is used, since the distance between the drive electrodes 104 and 105 is large as shown in FIG. 6, the efficiency of the electric field indicated by the arrow in FIG. 6 is poor. For this reason, there is a problem that the bending vibration of the vibrating arms 102 and 103 is weak and the crystal impedance (hereinafter referred to as CI value) becomes high.

  On the other hand, in the tuning fork type crystal resonator element 10 of the present embodiment shown in FIG. 4, since the thickness of the quartz substrate 1 can be made thinner than the conventional one, the X-axis (electricity) is preferable from the viewpoint of electric field efficiency although the etching rate is slow. The axis) is in the thickness direction. That is, a so-called X plate is used. Thereby, in the tuning fork type crystal resonator element 10 of the present embodiment, a strong electric field can be applied in the X-axis direction, and a low CI value can be achieved.

FIG. 7 is a view showing another cross-sectional structure of a conventional tuning fork type quartz vibrating element.
In the tuning fork type crystal vibrating element 110 shown in FIG. 7, grooves 114 and 114 and grooves 115 and 115 are formed on the main surfaces of the vibrating arms 112 and 113 from the front and back, respectively, and the grooves 114 and 115 are driven respectively. Electrodes 116 and 117 are formed. Drive electrodes 117 and 116 are also formed on both side surfaces of the vibrating arms 112 and 113, respectively. In the tuning-fork type crystal vibrating element 110 configured as described above, by applying a driving voltage to the driving electrodes 116 and 117 of the vibrating arms 112 and 113, an electric field is applied to the vibrating arms 102 and 103 as indicated by arrows, for example. Is generated so that the vibrating arms 112 and 113 are flexibly vibrated. Such a tuning fork type crystal resonator element 110 can apply a stronger electric field than the tuning fork type crystal resonator element 100 shown in FIG. However, in this case, since the grooves 114, 114, 115, 115 are formed in the respective vibrating arms 112, 113, the rigidity is lowered, and the electric field efficiency is further improved and the device is stable when trying to reduce the size. There was a problem that bending vibration could not be obtained.

  On the other hand, in the tuning fork type crystal resonator element 10 of the present embodiment shown in FIG. 4, since it is possible to apply a strong electric field in the X-axis direction, groove formation is unnecessary, so that rigidity does not decrease. The electric field efficiency can be increased. Further, the machining cost can be reduced by the amount that does not require the formation of the groove, and the cost can be reduced. Furthermore, it is possible to avoid occurrence of components other than flexural vibration due to the cross-sectional shape of the vibrating arm deviating from the ideal shape due to the groove formation.

FIG. 5 is a cross-sectional view showing another configuration of the tuning-fork type crystal resonator element according to the present embodiment. In this case, the schematic structure of the tuning fork type crystal vibrating element is the same as that shown in FIG.
In this case, a thin electrode 26 a is formed on the outer side edge of the surface of the vibrating arm 22 along the direction in which the vibrating arm 22 extends. A thin electrode 26b is formed inside the surface of the vibrating arm 22 along the direction in which the vibrating arm 22 extends. The electrodes 26 a and 26 b constitute a first electrode of the vibrating arm 22. On the other hand, a thin electrode 27a is formed on the outer side edge of the surface of the vibrating arm 23 along the direction in which the vibrating arm 13 extends. Further, a thin electrode 27b is formed inside the surface of the vibrating arm 23 along the direction in which the vibrating arm 23 extends. The electrodes 27a and 27b constitute a first electrode of the vibrating arm 23.
The electrode 26a and the electrode 27a are connected by a conductive portion (not shown). The electrode 26b and the electrode 27b are also connected by a conductive portion (not shown). The above electrodes can be obtained by processing an electrode film formed by, for example, forming an underlayer of chromium on a crystal by sputtering and forming a gold film thereon by a photolithographic technique or the like. .

  Next, the piezoelectric thin films 24 and 25 are formed on the first electrodes 26 and 27 of the vibrating arms 22 and 23. Preferably, a piezoelectric thin film is individually formed on each of the electrode 26a, the electrode 26b, the electrode 27a, and the electrode 27b. As this piezoelectric thin film, zinc oxide (ZnO) can be preferably used, but in addition, AIN, PZT, or the like can be used, and a quartz thin film may be used. The piezoelectric thin films 24 and 25 can be formed by sputtering or the like. Next, second electrodes 28 and 29 are formed on the first electrodes 26 and 27 with the piezoelectric thin films 24 and 25 interposed therebetween. Specifically, the electrode 28a is formed on the electrode 26a, the electrode 28b is formed on the electrode 26b, the electrode 29a is formed on the electrode 27a, and the electrode 29b is formed on the electrode 27b. The electrode 28a and the electrode 29a are connected to the electrodes 26b and 27b. The electrode 28b and the electrode 29b are connected to the electrode 26a and the electrode 27a.

In the piezoelectric vibration element 20 configured as described above, by applying a driving voltage to the electrodes sandwiching the piezoelectric thin films 24 and 25, the virtual arm line Cl is sandwiched between the vibrating arm 22 and the vibrating arm 23, respectively. When the quartz material on one side edge extends slightly along the Y direction, the material on the other side edge shrinks along the Y direction. By repeating this alternately, the vibrating arm 22 and the vibrating arm 23 on which the respective piezoelectric thin films are formed bend and vibrate so that their tips approach and separate from each other. A frequency can be generated.
Further, in the tuning fork type crystal resonator element having such a structure, if the tuning fork type crystal resonator element 4 manufactured by the manufacturing method of the present embodiment is used, the crystal resonator element 4 can be reduced in weight and reduced in weight. The piezoelectric thin film formed on the vibrating arms 22 and 23 can be easily driven, and a piezoelectric vibrating element having a small CI value can be realized.

  In the present embodiment, the case where the tuning fork type crystal vibrating element is configured using the tuning fork type crystal vibrating piece manufactured by the manufacturing method of the present embodiment has been described as an example, but this is only an example. Various bending vibration elements such as a gyro element and a contour vibrator can be configured using the tuning-fork type piezoelectric vibration piece manufactured by the manufacturing method of the embodiment.

It is the figure which showed the manufacturing process of the piezoelectric vibrating piece of this embodiment. It is the figure which showed the manufacturing process of the piezoelectric vibrating piece of this embodiment. It is the figure which showed the structure at the time of producing a piezoelectric vibrating piece by another manufacturing process. It is the figure which showed the structure of the tuning fork type crystal vibration element of this embodiment. It is the figure which showed the other structure of the tuning fork type crystal vibration element of this embodiment. It is sectional drawing which showed the structure of the conventional tuning fork type piezoelectric vibration element. It is sectional drawing which showed the other structure of the conventional tuning fork type piezoelectric vibration element. It is a perspective view which shows schematic structure of the conventional tuning fork type piezoelectric vibration element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Quartz substrate, 2 ... Silicon substrate, 3 ... Through-hole, 4 ... Tuning fork type crystal vibrating piece, 5 ... Opening part, 10 ... Tuning fork type crystal vibrating element, 11 ... Base part, 12, 13 ... Vibrating arm, 14 ... Drive Electrode, 20 ... piezoelectric vibration element, 24, 25 ... piezoelectric thin film, 26, 27, 228, 29 ... electrode

Claims (5)

A bonding step of bonding a piezoelectric substrate and a base substrate having a different etching rate from the piezoelectric substrate;
A polishing step of polishing the piezoelectric substrate after the bonding step;
A base etching step of etching the base substrate after the bonding step;
A piezoelectric etching step of etching the piezoelectric substrate after the polishing step;
Only including,
A method of manufacturing a piezoelectric vibrating piece , comprising: etching the base substrate by the base etching step; and etching the piezoelectric substrate by the piezoelectric etching step . The base etching step includes a step of removing the base substrate that overlaps at least a region where the vibrating arm of the piezoelectric substrate is formed in the base substrate in plan view, and etching while leaving a part of the base substrate. ,
The method for manufacturing a piezoelectric vibrating piece according to claim 1 , wherein the piezoelectric etching step includes a step of etching the piezoelectric substrate in a state where the part of the base substrate is bonded to the piezoelectric substrate. . The method for manufacturing a piezoelectric vibrating piece according to claim 1 , wherein the base etching step forms a concave opening in the base substrate. A piezoelectric vibration produced by the method for producing a piezoelectric vibrating piece according to any one of claims 1 to 3 , and comprising a piezoelectric vibrating piece having a thickness direction formed along an electric axis. element. A piezoelectric vibrating piece manufactured by the method of manufacturing a piezoelectric vibrating piece according to any one of claims 1 to 4 ,
A first electrode formed on each side edge of the surface of the vibrating arm of the piezoelectric vibrating piece and having a different polarity from each other;
A piezoelectric thin film formed on the surface of the first electrode, and a second electrode formed on the surface of the piezoelectric thin film so as to be paired with the first electrode across the piezoelectric thin film;
A piezoelectric vibration element comprising:

Images