JP2000323954A - Piezoelectric device, its manufacture and mobile communication equipment provided with piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide an energy confinement type piezoelectric device capable of reducing spurious output and of being easily handled. SOLUTION: An excitation electrode 3a is formed in a groove 2 formed on one main face of a piezoelectric substrate 1 and an excitation electrode 3b is formed in a position facing the excitation electrode 3a with the piezoelectric substrate in between. Thus, the thickness of the piezoelectric substrate 1 between the excitation electrodes 3a and 3b is made thin to obtain high frequency vibration. Thus, the strength of a device is secured by the thickness of a part except for the groove part 2. Vibration absorbing materials 4a and 4b are applied on both side surfaces of the piezoelectric substrate 1 in the width direction f the groove part 2 and vibration leaking in the width direction of the groove part 2 in vibrations vibrated by the excitation electrodes 3a and 3b is absorbed. Thus, unnecessary vibration is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a high-frequency vibrator used for generating a clock signal for a peripheral device of a personal computer or a multi-mode piezoelectric filter used for an intermediate frequency (hereinafter, referred to as IF) filter of a wireless communication device. The present invention relates to an energy trapping type thickness resonance piezoelectric device, a method of manufacturing the same, and a mobile communication device using the same.

[0002]

2. Description of the Related Art In recent years, with the increase in the speed of information processing terminals and the digitization of communication, piezoelectric devices such as small and high-frequency vibrators and small and wideband IF filters have been strongly demanded. Conventionally, as these piezoelectric devices, an energy trapping type piezoelectric vibrator or a piezoelectric filter has been used, but a smaller and wider band device is required.

[0003] Quartz filters have been most widely used as energy trap type piezoelectric filters. However, when quartz is used, it is difficult to form a filter having a wide band because the electro-mechanical coupling coefficient of the material is small.

For this reason, piezoelectric single crystals and piezoelectric ceramics having a large electro-mechanical coupling coefficient are used for piezoelectric devices. However, these generally exhibit brittle properties, and are difficult to etch or thin. Is also difficult to handle.

Accordingly, it has been difficult to form a high-frequency and high-accuracy piezoelectric vibrator or a wide-band piezoelectric filter. In addition, when the size becomes small, spurious characteristic to the element shape easily occurs, and it is difficult to obtain a vibrator having good characteristics.

An example of a conventional method for suppressing spurious in an energy trap type piezoelectric vibrator will be described with reference to FIG. In FIG. 15, 81 is a piezoelectric substrate, 82 is an excitation electrode, and 83 is a vibration absorbing material. As shown in FIG.
In the conventional piezoelectric vibrator, in order to suppress unnecessary vibration other than the thickness vibration confined under the excitation electrode 82, a method of weakening the unnecessary vibration by applying a vibration absorbing material 83 to a position that does not affect the thickness vibration is known. Had been taken.

However, the effect of the vibration absorbing material 83 is low if the application position is inappropriate, and a high-precision and extremely small amount of application is required to control the application amount and application position of the vibration absorbing material. Was difficult.

Further, as the element becomes smaller, the vibration absorbing material 83 is disposed immediately adjacent to the excitation electrode 82, and during application or curing, the vibration absorbing material 83 flows out to the excitation electrode 82, and up to the main vibration. There is a problem that also hinders. When the vibration is inhibited, the Q value and the CI value in the characteristics of the vibrator are reduced. In the case of a filter, insertion loss increases and out-of-band attenuation decreases.

[0009]

In an energy trap type piezoelectric device, the thickness of the element is inversely proportional to the resonance frequency of the element. Can it be thin?
Another problem is to obtain an element that is easy to handle even if it is thin. Furthermore, the biggest issue is how to control the spurious level by adjusting the shape and energy confinement of the element.

When the piezoelectric device is a vibrator, the spurious causes a jump in the oscillation frequency of the vibrator or an unstable excitation state. In addition, spurious components cause ripples in a pass band when the piezoelectric device is a filter.

The present invention has been made in consideration of the conventional problems as described above, and provides a piezoelectric device capable of suppressing unnecessary spurious components and corresponding to a higher frequency, and manufacturing such a piezoelectric device more easily. It is an object of the present invention to provide a manufacturing method for performing the method.

[0012]

In order to achieve the above object, a piezoelectric device according to the present invention is provided on a piezoelectric substrate, and on one principal surface of the piezoelectric substrate and another principal surface opposite to the one principal surface. A piezoelectric device comprising at least one set of excitation electrodes for exciting the thickness vibration of the piezoelectric substrate,
A groove extending from one side of the main surface to the other side opposite to the one side is formed on at least one main surface of the one main surface and the other main surface of the piezoelectric substrate, and at least one of the pair of excitation electrodes is formed. One excitation electrode is formed inside the groove.

According to this structure, since one of the excitation electrodes is formed inside the groove formed in the piezoelectric substrate, of the thickness vibration excited by the excitation electrode, the vibration that is not confined under the excitation electrode. Toward the portion where the thickness of the piezoelectric substrate is large, that is, in the width direction of the groove,
Propagate selectively. This makes it easy to control leakage vibrations other than the main vibrations, and can provide a piezoelectric device having excellent characteristics.

Further, in order to obtain a high-frequency piezoelectric device, it is necessary to reduce the thickness of the portion where the thickness vibration is excited. However, according to the above configuration, the portion where the thickness vibration is excited is made thin. Even if the groove is formed to a certain depth, the strength of the entire device is ensured by the thickness of the portions on both sides of the groove. As a result, spurious due to expansion and contraction or displacement of the device can be suppressed to be small, so that it is possible to provide a high-frequency piezoelectric device with high accuracy and easy handling.

It is preferable that the piezoelectric device has a structure in which a vibration absorbing material is provided on a side surface of the piezoelectric substrate parallel to the groove.

According to this configuration, the vibration that is not confined under the excitation electrode is selectively propagated toward the portion where the thickness of the piezoelectric substrate is large, that is, in the width direction of the groove, so that the vibration in the piezoelectric substrate is reduced. Reaching the side parallel to the groove,
It is absorbed by the vibration absorbing material provided on this side.
Thus, the spurious can be suppressed small, so that a highly accurate piezoelectric device can be provided.

In the above-mentioned piezoelectric device, it is preferable that the excitation electrode formed inside the groove is formed to have a width equal to the width of the groove.

Alternatively, in the above-described piezoelectric device, it is preferable that the excitation electrode formed inside the groove is formed to have a width smaller than the width of the groove. According to this configuration, since the groove width and the electrode width can be separately designed and the optimum range can be selected, there is an advantage that the degree of freedom in design is improved.

In the above piezoelectric device, the thickness of the portion of the piezoelectric substrate where the groove is formed is 5 μm to 300 μm.
It is preferably in the range of μm.

In the above-described piezoelectric device, it is preferable that the excitation electrode formed on one of the main surface and the other main surface of the piezoelectric substrate is formed over the entire surface of the main surface.

According to this structure, the excitation electrode formed on one main surface is formed over the entire main surface.
When forming the excitation electrode, patterning by photolithography or the like is not required. This simplifies the manufacturing process, so that a highly accurate piezoelectric device can be provided at low cost. Since the vibration is confined in a portion where the above-mentioned excitation electrode and the excitation electrode formed on the other main surface face each other, if the excitation electrode formed on the other main surface is formed into a desired shape by patterning or the like. Good.

In the above-described piezoelectric device, the groove is formed on the main surface of the piezoelectric substrate on which the excitation electrode is formed over the entire surface, and the bottom surface and the side surface of the groove are formed. Is preferably an obtuse angle.

According to this structure, the excitation electrode is formed over the entire surface of the one main surface, and the angle formed between the bottom surface and the side surface of the groove formed on the main surface is obtuse. When forming the electrode, continuity of the excitation electrode at the boundary between the side surface and the bottom surface of the groove is ensured, disconnection can be prevented, and the yield is improved. As a result, a highly accurate piezoelectric device can be provided at low cost.

In the above-described piezoelectric device, the piezoelectric substrate may be formed by laminating a plurality of piezoelectric bodies, and the plurality of piezoelectric bodies may be arranged such that their polarization axes are alternately oriented in opposite directions. preferable.

According to this configuration, even if the piezoelectric substrate has the same thickness, the resonance frequency is several times that of a single-plate piezoelectric substrate in which the polarization axes are aligned in a single direction. Can be improved. That is, since high-frequency vibration can be obtained without making the device thin, it is possible to provide a high-performance and high-accuracy piezoelectric device that is easy to handle.

In the above-described piezoelectric device, the piezoelectric substrate may be:
A first piezoelectric body and a second piezoelectric body are stacked so that their polarization axes are opposite to each other.
Thickness of a portion of the piezoelectric body where thickness vibration is excited,
It is preferable that the groove is formed so that a thickness of a portion of the second piezoelectric body where thickness vibration is excited is substantially equal.

According to this configuration, the resonance frequency can be reduced by about 2 even if the piezoelectric substrate has the same thickness, as compared with the case of using a single-plate piezoelectric substrate in which the polarization axes are aligned in a single direction.
Can be improved by a factor of two. That is, since high-frequency vibration can be obtained without making the device thin, it is possible to provide a high-performance and high-accuracy piezoelectric device that is easy to handle.

In the above-described piezoelectric device, a plurality of excitation electrodes are provided on at least one of the one principal surface and the one principal surface of the piezoelectric substrate, and the plurality of excitation electrodes are close to each other so that the thickness vibration mode is coupled. Preferably, they are arranged.

According to this configuration, by combining the thickness vibration modes of the plurality of excitation electrodes, it is possible to provide a broadband piezoelectric device that functions as a multimode piezoelectric filter.

According to another aspect of the present invention, there is provided a method of manufacturing a piezoelectric device, comprising: forming a plurality of grooves in at least one principal surface of a plate-shaped piezoelectric body in a substantially parallel manner.
And forming at least one set of excitation electrodes facing each other across the piezoelectric body such that at least one of the excitation electrodes of the set of excitation electrodes is located inside the groove.
And a third step of dividing the piezoelectric body by cutting the space between the plurality of grooves in the piezoelectric body substantially in parallel with the groove, and a step of cutting the piezoelectric body parallel to the groove in the divided piezoelectric body. The method includes a fourth step of applying a vibration absorbing material to both side surfaces and a fifth step of cutting the divided piezoelectric body substantially at right angles to the groove.

According to this manufacturing method, one of the excitation electrodes is formed inside the groove formed in the piezoelectric substrate. Thereby, in the piezoelectric device manufactured by the above manufacturing method,
Of the thickness vibrations excited by the excitation electrodes, the vibrations that are not confined under the excitation electrodes selectively propagate toward the portion where the thickness of the piezoelectric substrate is large, that is, in the width direction of the grooves, and propagate to the grooves. It is absorbed by the vibration absorbing material formed on both parallel side surfaces. Thus, the spurious can be suppressed small, so that a high-precision piezoelectric device can be provided.

In order to obtain a high-frequency piezoelectric device, it is necessary to reduce the thickness of a portion where thickness vibration is excited. Even if the groove is formed to a certain depth to make it thin, the strength of the entire device is secured by the thickness of the portions on both sides of the groove. As a result, spurious due to expansion and contraction or displacement of the device can be suppressed to be small, so that it is possible to provide a high-frequency piezoelectric device with high accuracy and easy handling.

Further, in a state where the piezoelectric body is divided substantially parallel to the groove, a vibration absorbing material is applied to both side surfaces parallel to the groove.
The vibration absorbing material can be applied to a plurality of piezoelectric devices at once. As a result, mass productivity is improved, and there is an advantage that a piezoelectric device can be provided at low cost.

Further, the above-described method for manufacturing a piezoelectric device comprises:
In the second step, it is preferable to use a metal mask having an opening width larger than the width of the groove when forming the excitation electrode on the main surface of the piezoelectric body where the groove is formed.

According to this manufacturing method, in patterning using a metal mask, it is not necessary to apply a uniform resist or adhere a glass mask as in photolithography. Becomes possible. Therefore, the vibrating portion of the piezoelectric body can be formed thinner, and a higher performance piezoelectric device can be provided.

Further, the above-described method for manufacturing a piezoelectric device comprises:
After laminating and joining a plurality of piezoelectric bodies so that the polarization axes are alternately oriented in opposite directions, forming the plate-shaped piezoelectric body by polishing one main surface of the joined piezoelectric bodies, Preferably, the groove is formed before the first step, and in the first step, the groove is formed on the other main surface of the bonded piezoelectric body opposite to the one main surface.

According to this manufacturing method, by using a plurality of piezoelectric bodies laminated so that the polarization axes are alternately directed in opposite directions, a single-plate configuration in which the polarization axes are aligned in a single direction is used. As compared with the case where the piezoelectric substrate is used, even if the piezoelectric substrate has the same thickness, it is possible to realize a piezoelectric device whose resonance frequency is improved several times. That is, since high-frequency vibration can be obtained without making the device thin, it is possible to provide a high-performance and high-accuracy piezoelectric device that is easy to handle.

Further, by polishing one main surface in a state in which a plurality of piezoelectric bodies are stacked, the one main surface is supported by the piezoelectric body stacked behind, so that breakage such as cracks does not occur during polishing. A thin layer of the piezoelectric body can be easily obtained. Also, when the grooves are formed on the other main surface after the polishing of one main surface is completed, since a plurality of piezoelectric bodies are stacked,
Breakage and other damage are less likely to occur. As a result, the yield is improved, and a high-performance and high-accuracy piezoelectric device can be provided at low cost.

Further, any one of the piezoelectric devices described above,
According to the mobile communication device including the piezoelectric device manufactured by any of the above-described methods for manufacturing a piezoelectric device, it is possible to obtain a mobile communication device having less spurious and stable characteristics.

[0040]

(Embodiment 1) An embodiment of the present invention will be described with reference to FIG.

The piezoelectric vibrator according to the present embodiment is shown in FIG.
As shown in (a) and (b), a piezoelectric substrate 1 is provided,
On the side surface of the piezoelectric substrate 1, vibration absorbing members 4a and 4b are provided. As shown in FIG. 1A, a groove 2 is formed on one surface of the piezoelectric substrate 1. An excitation electrode 3 a is provided on the inner surface of the groove 2. Further, as shown in FIG. 1 (b), the other surface of the piezoelectric substrate 1 is formed flat, and an excitation electrode 3b is provided.

It is preferable to use a piezoelectric substrate 1 having a coupling coefficient of about 10% or more.
In the piezoelectric vibrator of the present embodiment, as the piezoelectric substrate 1, Xc
ut lithium tantalate substrate is used.

Epoxy resin is used for the vibration absorbing members 4a and 4b. The external dimensions of the present piezoelectric vibrator are 5 mm square. The thickness of the portion of the piezoelectric substrate 1 where the groove 2 is not formed is 100 μm, and the depth of the groove 2 is 1 μm. Note that the width of the groove 2 is determined by the piezoelectric substrate 1.
Is preferably formed in a range of about 1 to 50 times the thickness of the portion where the groove 2 is formed.

The excitation electrodes 3a and 3b are connected to the piezoelectric substrate 1
By being provided at a position facing each other on both sides of the
Thickness vibration is excited between the excitation electrodes 3a and 3b. The excitation electrode 3a has a main portion 3 formed over the entire width of the groove 2.
and a _1, the main portion 3a ₁ having a width smaller than, and is constituted by a take-out wire portion 3a ₂ which is drawn to the longitudinal ends of the groove 2. The excitation electrode 3b is also formed in the same shape as the excitation electrode 3a.

As described above, since the piezoelectric substrate 1 has the groove 2 with a depth of 1 μm formed on one surface, the portion of the piezoelectric substrate 1 where the groove 2 is formed, that is, the thickness of the vibrating portion is 99 μm. . The resonance frequency is 20 MH
about z.

In the conventional piezoelectric vibrator, for example, as shown in FIG. 15, the entire piezoelectric substrate has a structure having the same thickness. Therefore, among the excited vibrations, the vibrations that are not confined under the electrodes are generated on the piezoelectric substrate. Is freely propagated in an arbitrary direction, and various reflections are repeated at the end of the element, and it is difficult to suppress this. In addition, conventional piezoelectric vibrators always have spurs due to expansion and contraction or displacement in the width or length direction of the element, and it is necessary to limit the design dimensions of the element so that these do not affect the main vibration. was there.

However, in the piezoelectric vibrator of this embodiment, the piezoelectric substrate 1 has a structure in which the groove 2 is formed, that is, thin at the vibrating part and thick at both ends of the vibrating part.
Of the vibrations excited by the vibrating portion, the vibrations that are not confined below the excitation electrodes 3 a and 3 b selectively propagate on the piezoelectric substrate 1 in the width direction of the groove 2.

The vibration propagated in the width direction of the groove 2 reaches both end faces of the piezoelectric substrate 1, and is effectively damped by the vibration absorbing materials 4a and 4b applied to the both end faces. As a result, a piezoelectric vibrator with small spurious is obtained. In addition, unnecessary vibration caused by expansion and contraction of the entire board, expansion and contraction in the width direction, and displacement can be suppressed.

Next, a method for manufacturing the piezoelectric vibrator according to the present embodiment will be described with reference to FIGS. 2 (a) to 2 (d) and FIGS. 3 (a) and 3 (b).

First, the base material 1M of the piezoelectric substrate 1 is
Finish with good parallelism with a thickness of m. With such a thickness, handling is easy, so that a plurality of piezoelectric substrates 1 can be manufactured simultaneously using a large-sized base material. Then, as shown in FIG. 2A, a groove is formed to a depth of 1 μm on the surface of the base material 1M of the piezoelectric substrate 1 by a mechanical processing method using the rotating grindstone 5 to form the groove 2. In addition, since the groove portion 2 to be formed is shallow, in addition to the mechanical processing method using the above-mentioned rotary grindstone 5, the processing efficiency is inferior to plasma processing, electric discharge processing, laser processing or chemical etching. It may be performed by processing.

Next, a resist 6 is applied to the entire surface of the base material 1M of the piezoelectric substrate 1, and the excitation electrodes 3a are formed at positions corresponding to the grooves 2.
By exposing a glass mask having the above-mentioned pattern and exposing the same, a resist pattern having an opening in a portion where the excitation electrode 3a is formed is obtained as shown in FIG.

Then, as shown in FIG. 3B, the material 3aM of the excitation electrode 3a is applied to the entire surface of the substrate 1M of the piezoelectric substrate 1 on which the resist pattern has been formed. Note that gold or the like can be used as the material 3aM of the excitation electrode 3a. Further, chromium may be formed as a base. Thereafter, the resist pattern is removed using an organic solvent. Thus, the excitation electrode 3a having a desired shape as shown in FIG. 1A is formed in the groove 2.

Note that, with respect to the other surface of the piezoelectric substrate 1,
Similarly to the above, a resist pattern is formed in which the pattern of the excitation electrode 3b is opened at a position corresponding to the upper and lower surfaces of the excitation electrode 3a, the electrode material is applied on the entire surface, and the resist pattern is removed using an organic solvent. As a result, the excitation electrode 3 having a desired shape as shown in FIG.
b is formed. A cross-sectional view of the piezoelectric vibrator at this stage is as shown in FIG.

Next, as shown in FIG. 2C, the base material 1M of the piezoelectric substrate 1 is cut into a long piece by cutting it in parallel with the length direction of the formed groove 2. And FIG.
As shown in (d), the epoxy resin is collectively applied to both sides in the width direction of the base material 1M of the piezoelectric substrate 1 cut into a long shape, and the epoxy resin is cured, whereby the vibration absorbing materials 4a and 4b are cured. To form Then, as shown in FIG. 5, the piezoelectric substrate 1 cut into a long length using a cutting machine 7.
By further cutting the base material 1M in a direction parallel to the width direction of the groove 2, the piezoelectric vibrators according to the present embodiment are individually cut and completed.

As described above, according to the manufacturing method of the present embodiment, it is possible to apply the vibration absorbing members 4a and 4b collectively in a state where several piezoelectric substrates 1 are elongated. The mass productivity is improved as compared with the case where a vibration absorbing material is applied to each of the piezoelectric substrates 1.

Further, since the piezoelectric vibrator of this embodiment includes the vibration absorbing members 4a and 4b, it becomes a high-precision piezoelectric vibrator which is less affected by unnecessary vibration. Further, unlike the conventional configuration shown in FIG. 15, since the application position of the vibration absorbing materials 4a and 4b is on the side surface of the piezoelectric substrate 1, the excitation electrodes 3a and 4b
3b, so that it is easy to suppress inflow and seepage after application. Thereby, there is an advantage that the mass productivity is improved and the characteristic variation is reduced.

In the above description, an example has been described in which, after an electrode material is formed over the entire upper layer of a resist pattern having openings of a desired shape, the excitation electrodes 3a and 3b are formed by a lift-off method of removing the resist. The method of forming the electrodes is not limited to this, and various methods can be used as long as the excitation electrode 3a is formed over the entire width of the groove 2.

For example, as shown in FIG. 4A, the material 3aM of the excitation electrode 3a is applied to the entire surface of the base 1M of the piezoelectric substrate 1, and as shown in FIG.
Patterned into the shape of a, as shown in FIG.
Using the resist 6 as a mask, the other material 3aM
Is removed by etching with a chemical, and finally the resist 6 is removed.
The same piezoelectric vibrator can be formed also by removing.

(Embodiment 2) Another embodiment of the present invention will be described with reference to FIGS. Note that the same components as those in the first embodiment include:
The same reference numerals as in the first embodiment are used, and the detailed description thereof will be omitted.

The piezoelectric vibrator according to this embodiment has the groove 2
Are formed on both surfaces of the piezoelectric substrate 1 and the excitation electrodes 3a
Not only that, but also the excitation electrode 3 b is formed inside the groove 2, which is different from the piezoelectric vibrator according to the first embodiment. As described above, the piezoelectric vibrator according to the present embodiment has a configuration in which spurious is less likely to occur than the piezoelectric vibrator according to the first embodiment because the shape of the piezoelectric substrate 1 is highly symmetric.

The manufacturing method of the piezoelectric vibrator according to the present embodiment is almost the same as the manufacturing process described in the first embodiment, but as shown in FIG. 2 is added. Hereinafter, the step of forming the excitation electrodes 3a and 3b in the grooves 2 formed on both surfaces of the piezoelectric substrate 1 can be realized by the lift-off method or the like as described in the first embodiment.

It is preferable to use a piezoelectric substrate 1 having a coupling coefficient of about 10% or more.
In the piezoelectric vibrator according to the present embodiment, a rotating Ycut lithium niobate substrate is used as the piezoelectric substrate 1. In addition, a silver paste is used as a material of the vibration absorbers 4a and 4b. The external dimensions of the piezoelectric substrate 1 are 3 mm square, the thickness of the portion of the piezoelectric substrate 1 where the groove 2 is not formed is 100 μm, and the depth of the groove 2 is 1 μm on each of the front and back surfaces of the piezoelectric substrate 1. I have. In the present embodiment, the width of the groove 2 is set to about 20 times the thickness of the portion of the piezoelectric substrate 1 where the groove 2 is formed, that is, 2 mm.
And

The excitation electrodes 3a and 3b are provided at positions where thickness vibrations are to be excited at positions opposing each other on both surfaces of the piezoelectric substrate 1. The grooves 2 are also provided at opposing positions on both surfaces of the piezoelectric substrate 1. The excitation electrode 3a has a main portion 3a ₁ formed over the entire width of the groove 2.
When, is constituted by the main portion 3a ₁ having a width smaller than a take-out line portion 3a ₂ which is drawn to the longitudinal ends of the groove 2. Also, the excitation electrode 3b is
It is formed in the same shape as a.

As described above, the piezoelectric substrate 1 has a depth of 1 on both sides.
The thickness of the vibrating portion is 98 μm and the resonance frequency is about 21 MHz by forming the μm groove 2.

According to the piezoelectric vibrator of this embodiment, the symmetry of the piezoelectric vibrator is good, and unnecessary vibration can be suppressed more effectively.

The thickness of the portion of the piezoelectric substrate 1 where the groove 2 is formed is preferably in the range of 5 μm to 300 μm, but there is no problem if it is smaller than 5 μm.

(Embodiment 3) Still another embodiment according to the present invention will be described with reference to FIGS. The same components as those in the above-described embodiments are denoted by the same reference numerals as those in the above-described embodiments, and detailed descriptions thereof will be omitted. The same applies to other embodiments described later.

In the piezoelectric vibrator according to this embodiment, as shown in FIG. 8, the grooves 2 formed in the piezoelectric substrate 1 are formed deeper than those in the above-described embodiments, and the excitation electrodes 3a and 3b are formed. Instead of having the excitation electrodes 13a and 13b formed to have a width smaller than the width of the groove 2,
This is different from the piezoelectric vibrator according to each embodiment described above.

The present piezoelectric vibrator has excitation electrodes 13a and 13b
Is formed smaller than the width of the groove 2,
Since the groove width and the electrode width can be separately designed and the optimum range can be selected, there is an advantage that the degree of freedom in design is improved.

The piezoelectric substrate 1 has a coupling coefficient of about 10%.
It is preferable to use a substrate larger than the above. In this embodiment, an Xcut lithium tantalate substrate is used as the piezoelectric substrate 1. The vibration absorbing members 4a and 4b are formed using polyimide. The external dimensions of this piezoelectric vibrator are 2
mm, the thickness of the portion of the piezoelectric substrate 1 where the groove 2 is not formed is 100 μm, and the depth of the groove 2 is 50 μm.
m. The width of the groove 2 is 10 mm.

The excitation electrodes 13a and 13b are provided at positions where thickness vibrations are to be excited, at positions opposing each other on both surfaces of the piezoelectric substrate 1. The excitation electrode 13a is
The main portion 13a ₁ formed in a width smaller than the width of the main portion 13a ₁ having a width smaller than, be constituted by a take-out wire portion 13a ₂ which is drawn to the longitudinal ends of the groove 2 I have. The width of the main portion 13a ₁ of the exciting electrode 13a is 0.12 mm. The excitation electrode 13b is also the excitation electrode 13
It is formed in the same shape as a. The excitation electrode 13a
The thickness of 13b is 0.2 μm;

The thus configured piezoelectric vibrator of the present embodiment exhibits a resonance frequency of about 40 MHz.

In a conventional piezoelectric vibrator, for example, as shown in FIG. 15, the piezoelectric substrate is formed to have a uniform thickness. Therefore, if the piezoelectric substrate is made thinner to increase the resonance frequency, it can be handled without being damaged. Was difficult. Therefore, the upper limit of the resonance frequency of the conventional piezoelectric vibrator is 20 M
Hz. In addition, since the element is reduced in size, it is difficult to apply a vibration absorbing material for suppressing unnecessary waves.

On the other hand, in the piezoelectric vibrator of this embodiment, the vibrating part is thin, but the part around the groove 2 is thick because the groove 2 is provided in the piezoelectric substrate 1.
Therefore, the thick portion can be held and handled, so that the entire piezoelectric vibrator can be easily handled. Also, in the piezoelectric substrate 1, by applying the vibration absorbing materials 4a and 4b to both side surfaces in the width direction of the groove 2, the vibration absorbing material is applied to the surface of the piezoelectric substrate like the conventional piezoelectric vibrator shown in FIG. Compared to the case of applying, stable application becomes possible and unnecessary vibration can be suppressed.

Here, the method of manufacturing the piezoelectric vibrator according to the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 9A, in the manufacturing process of the present piezoelectric vibrator, similarly to the first embodiment, the groove 1 is formed on the base 1M of the piezoelectric substrate 1 by grinding using a rotary grindstone. Form 2 However, in the formation of the groove 2, although the processing efficiency is inferior, a means other than the rotary grindstone may be used as in the first embodiment.

Next, the formation of the excitation electrode 13a in the groove 2 is performed by masking using a metal mask instead of the photolithography step in the first and second embodiments. That is, as shown in FIG. 9B, a metal mask 8 having an opening corresponding to the pattern of the excitation electrode 13a is arranged at a predetermined position, and chromium and gold are vacuum-deposited in this order to form the metal mask 8 The excitation electrodes 13a having a pattern corresponding to the openings are formed. The reason for performing the masking with the metal mask 8 is that it becomes difficult to apply a photolithography process that requires uniform application of a resist and close contact of a glass mask when the groove 2 is deepened.

As described above, according to the present embodiment, the vibrating portion is formed in the first embodiment by forming the groove 2 deep.
Alternatively, there is an advantage that it is possible to provide a thinner and higher frequency piezoelectric vibrator as compared with the piezoelectric vibrator according to the second aspect.

(Embodiment 4) Still another embodiment according to the present invention will be described with reference to FIGS.

The main difference between the piezoelectric vibrator according to the present embodiment and the piezoelectric vibrator according to the first embodiment is that, in the piezoelectric vibrator according to the present embodiment, the piezoelectric substrate 1 has an Xcut having a large coupling coefficient. 2 of lithium tantalate substrates 1a and 1b
This is a point composed of sheets. The substrate 1a
A groove portion 2 is formed.

The piezoelectric substrate 1 of the present piezoelectric vibrator has a configuration in which two substrates 1a and 1b are arranged such that their polarization axes are opposite to each other and are directly joined. A substrate having such a configuration is disclosed in JP-A-7-206600.

By using a substrate having such a configuration as the piezoelectric substrate 1, it is possible to excite the vibration of the second harmonic, and it is possible to double the resonance frequency. Note that the above 2
The vibration of the harmonic is not normally excited in a substrate having the same thickness constituted by a single piezoelectric body.

In the piezoelectric vibrator of this embodiment, epoxy resin is used for the vibration absorbing members 4a and 4b. The outer shape of the present piezoelectric vibrator is 1.5 mm square. The thickness of the portion of the substrate 1a where the groove 2 is not formed is 100 μm, and the thickness of the substrate 1b is 25 μm. The depth of the groove 2 formed in the substrate 1a is 75 μm. Accordingly, the thickness of the portion of the piezoelectric substrate 1 where the groove 2 is not formed is 125 μm, and the thickness of the portion where the groove 2 is formed, that is, the thickness of the vibrating portion is 50 μm. The width of the groove 2 is 0.12 mm.

The excitation electrodes 3a and 3b are provided at positions where thickness vibrations are to be excited at positions opposing each other on both surfaces of the piezoelectric substrate 1. Excitation electrodes 3a includes a main portion 3a ₁ which is formed over the groove 2 of the full width, has a narrower width than the main portion 3a _1, a take-out line portion 3a ₂ which is drawn to the longitudinal ends of the groove 2, It is constituted by a residue portion 3a _3. Residue portion 3a ₃ is one in which the electrode material in the groove 2 in the edge portion when forming the main portion 3a ₁ of the excitation electrode 3a over the entire width of the groove portion 2 is formed by depositing, as described below, It does not affect the characteristics of the piezoelectric vibrator. The excitation electrode 3b is formed in the same shape as the excitation electrode 3a in the groove 2.

In the present piezoelectric vibrator, the depth of the groove 2 is 7
Since the thickness is 5 μm, the thickness of the vibrating portion in the piezoelectric substrate 1 is 50 μm. As described above, the piezoelectric substrate 1 is composed of the two lithium tantalate substrates 1a and 1b joined so that the polarization axes are opposite to each other.
It shows twice the resonance frequency of a substrate of the same thickness in which the polarization axes are aligned in a single direction, and shows a resonance frequency of about 80 MHz.

Further, since the excitation electrode 3a is formed over the entire width of the groove 2, the vibration effectively propagates to the end face of the substrate, and the vibration absorption provided on both side surfaces of the piezoelectric substrate 1 in the width direction of the groove 2 is provided. It is suppressed by the members 4a and 4b.

Here, a method of manufacturing the piezoelectric vibrator according to the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 11 (a), base materials 1aM and 1bM of lithium tantalate substrates 1a and 1b are prepared, arranged so that their polarization axes point in opposite directions, and are directly joined. The thickness of each of the substrates 1aM and 1bM is 100 μm.

Next, as shown in FIG. 11B, the substrate 1bM of the lithium tantalate substrate 1b is polished to a desired thickness. The thickness at this time is set such that the joint surface between the two substrates 1a and 1b is located at a position exactly 厚 of the thickness of the vibrating portion after the groove 2 is formed in a step described later. That is, in the present embodiment, the final thickness of the vibrating portion is 5
Since the thickness is 0 μm, polishing is performed until the thickness of the substrate 1bM becomes 25 μm. Although it is difficult to obtain such a 25 μm-thick plate alone, as in the present embodiment, two substrates 1
By polishing the base material 1bM in a state where the base material 1bM is adhered to the aM · 1bM, the base material 1bM is not cracked even when polished to a thickness of 25 μm.

Next, as shown in FIG. 11C, the excitation electrode 3a is masked by a metal mask 8 having an opening corresponding to the pattern of the excitation electrode 3a, and chromium and gold are vacuum-deposited in this order. To form As described in the third embodiment, when the groove 2 is deep, it is difficult to form an electrode having a width exactly equal to the width of the groove 2 by a photolithography process, but as shown in FIG. A metal mask 8 having an opening width larger than the width of the groove 2.
If an electrode is formed using the method shown in FIG.
It can form a main portion 3a ₁ of the excitation electrode 3a over the groove 2 of the full width.

Note that, at this time, the metal mask 8 having an opening width larger than the width of the groove 2 is used, so that FIG.
As also shown in 0, while the grooves 2 of the residue portions 3a ₃ the edge portion of the opening is formed, the residue portions 3a _3, the area is also small, the main portion 3a by inner and outer step of the groove 2 _Since it is separated from ₁ , no extra capacitance is formed, and the characteristics of the present piezoelectric vibrator are not affected.

As described above, according to the present embodiment, it is possible to provide a piezoelectric vibrator capable of more effectively suppressing unnecessary vibration even when the width of the groove 2 is large. Also, by providing a piezoelectric substrate with two substrates directly bonded so that their polarization axes point in opposite directions, a piezoelectric vibrator having a higher resonance frequency than a single-plate piezoelectric vibrator is provided. Can be.

(Fifth Embodiment) Still another embodiment according to the present invention will be described with reference to FIGS.

FIG. 1 shows a piezoelectric filter according to this embodiment.
2 (a) and (b), the groove 2
Is provided. As shown in FIG. 12A, an excitation electrode 23a is provided so as to cover the entire surface of the piezoelectric substrate 1 on which the groove 2 is provided. As shown in FIG. 12B, two excitation electrodes 2 are provided on the surface of the piezoelectric substrate 1 on which the groove 2 is not provided.
3b is provided.

Each of the two excitation electrodes 23b is
The main portion 23b ₁ formed in substantially the same width as the groove 2 in the portion where the thickness becomes smaller (vibrating portion) by the groove 2 is formed in the piezoelectric substrate 1, it is formed to a smaller width than the main portion 23b ₁ , and a lead wire portion 23b ₂ Metropolitan drawn to the end of the piezoelectric substrate 1. The two excitation electrodes 23b, each of the main portion 23b ₁ is disposed to face.

As described above, the present piezoelectric filter is provided with the two excitation electrodes 23b arranged close to each other.
The thickness vibration mode is coupled between the two excitation electrodes 23b,
It functions as a so-called multi-mode piezoelectric filter. Also in such a piezoelectric filter, as in the piezoelectric vibrators according to the above-described embodiments, suppression of spurious leads to stabilization of characteristics.

As in the fourth embodiment, the Xcut lithium tantalate substrate 1a having a large coupling coefficient is used as in the fourth embodiment.
-It is a configuration where 1b is joined.

The outer shape of the present piezoelectric filter is 1.5 mm square, the thickness of the portion of the substrate 1a where the groove 2 is not formed is 100 μm, and the thickness of the substrate 1b is 20 μm.
m. The depth of the groove 2 is 80 μm. Therefore, in the piezoelectric substrate 1 as a whole, the thickness of the portion where the groove 2 is not formed is 120 μm, and the thickness of the portion where the groove 2 is formed, that is, the vibration portion is 40 μm. The width of the groove 2 is 0.06 mm. The center frequency of the present piezoelectric filter is about 100 MHz.

Hereinafter, a method of manufacturing the present piezoelectric filter will be described with reference to FIGS.

First, as shown in FIG. 13A, lithium tantalate substrates 1a and 1
The substrates 1aM and 1bM of b are prepared, arranged so that the polarization axes point in opposite directions, and directly joined, and the substrate 1bM is polished until the thickness becomes 20 μm.

Next, as shown in FIG.
By performing groove processing on the aM, a groove 2 having a depth of 80 μm is formed. Here, the groove portion 2 is formed by a mechanical processing method using the rotating grindstone 5, but the shape of the rotating grindstone 5 is tapered, and the shape is transferred to the groove. That is, the angle of the side surface with respect to the bottom surface of the groove 2 is an obtuse angle. This prevents disconnection of the excitation electrode 23a formed in the next step.

Next, as shown in FIG. 13 (c), the excitation electrode 2
3a is formed. Further, a photolithography process is performed on a surface of the piezoelectric substrate 1 opposite to the surface on which the groove 2 is formed, by a photolithography process.
The two excitation electrodes 23b are formed to have substantially the same width as the groove 2.

Finally, as shown in FIG. 13D, as described in the first embodiment, the base materials 1aM and 1bM are cut out in parallel to the longitudinal direction of the groove 2, and the cutout is shown in FIG. As described above, the vibration absorbing members 4a
After applying 4b, the piezoelectric filters are individually cut out by further cutting the base materials 1aM and 1bM in the width direction of the groove 2. Thereby, the piezoelectric filter according to the present embodiment is completed.

As described above, in the piezoelectric filter according to the present embodiment, since the excitation electrode 23a is formed so as to cover the entire surface of one surface of the piezoelectric substrate 1, patterning by photolithography or the like is unnecessary, and the manufacturing process is not performed. Is simplified. This makes it possible to provide the piezoelectric filter at low cost. The thickness vibration, since the excitation electrode 23a and an excitation electrode 23b is excited at a portion facing the main portion 23b ₁ of the excitation electrodes 23b, may be formed in the same width as the groove 2 of width.

Further, by using the piezoelectric filter according to the present embodiment in a wireless communication device (mobile communication device) such as a mobile phone, unnecessary spurious is suppressed, the degree of freedom in design is large, and the characteristics are excellent. Since the high-frequency section can be constituted by the piezoelectric filter, it is possible to realize a wireless communication device that has a high selectivity of the adjacent channel and is less susceptible to an interference wave. Also, this piezoelectric filter
There is also the advantage of having excellent channel selectivity.

Here, a configuration example of a wireless device (a mobile phone or the like) provided with the piezoelectric filter according to the present embodiment will be described. FIG.
4 is a block diagram illustrating a configuration of a receiving circuit of the wireless device. The piezoelectric filter of the present embodiment is suitably used as the primary IF filter 34 in such a receiving device of the wireless device.

The receiving circuit converts the radio signal (Rx) received by the antenna 31 into an Rx filter 32, a mixer 33,
The signal is converted into an AC signal via a primary IF filter 34, a mixer 35, a secondary IF filter 36, and an amplifier 37. The reference frequencies f ₁ and f ₂ are given to the mixers 33 and 35 from the reference frequency generation circuits 38 and 39, respectively.

However, the application of the present piezoelectric filter is not limited to the receiving circuit of the radio equipment shown in FIG.
It can be applied to various information devices and communication devices.

Similarly, by using the piezoelectric vibrators according to the first to fourth embodiments for information equipment and communication equipment, a piezoelectric vibrator which has stable characteristics with little spuriousness and which is small and can handle high frequencies. Therefore, it is possible to realize an information device or a communication device whose reference frequency and operation are stable.

The first to fifth embodiments do not limit the present invention, and various modifications are possible.
For example, the present invention is not limited to the piezoelectric vibrator and the multi-mode piezoelectric filter, but can be widely applied to all energy trap type piezoelectric devices, and the same effects can be obtained.

In each of the embodiments described above, lithium niobate and lithium tantalate are used as the piezoelectric material. However, the present invention is not limited to the piezoelectric material, and may be used to construct an energy trapping multi-mode piezoelectric filter. Similar effects can be obtained with various piezoelectric materials that can be used.

In each of the above-described embodiments, for example, FIG. 2 and the like show the procedure for manufacturing a plurality of piezoelectric devices by forming two rows of grooves in the base material of the piezoelectric substrate. The number of piezoelectric devices that can be collectively manufactured using the base material is arbitrary, and it is of course possible to manufacture a larger number of piezoelectric devices collectively using a larger substrate.

Further, the number of sets of the excitation electrodes is not limited to one or two, but may be a configuration in which a larger number of sets of the excitation electrodes are connected.

In the first to fourth embodiments, the case where the excitation electrodes have the same size on the front and back sides is mainly shown.
As shown in the above, one excitation electrode may be formed over the entire surface of the piezoelectric substrate, and the vibration may be confined in a portion overlapping with the other excitation electrode.

In the above description, an epoxy resin, a conductive paste, or the like is used as an example of the vibration absorbing material. However, the vibration absorbing material is not limited to this, and may be made of a completely different material such as another metal oxide material or an insulating material. It does not matter.

In each of the embodiments, the method of forming a groove mainly by grinding has been described. However, other methods such as electric discharge machining, wet etching, laser machining, CVM, and dry etching may be used. Good.

[0117]

As described above, according to the present invention, it is possible to provide a high-frequency piezoelectric device with small spuriousness, high accuracy and easy handling at low cost.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a configuration of an energy trapping type piezoelectric device according to a first embodiment of the present invention with one main surface facing upward, and FIG. 1B is a perspective view showing the configuration of the piezoelectric device. Perspective view with the other main surface facing the main surface facing up

FIGS. 2A to 2D are cross-sectional views illustrating the configuration of the piezoelectric device according to the first embodiment in the order of main manufacturing steps;

FIGS. 3A and 3B are cross-sectional views illustrating an example of a step of forming an excitation electrode on one main surface of a piezoelectric substrate as a part of a step of manufacturing the piezoelectric device according to the first embodiment;

FIGS. 4A to 4C are cross-sectional views illustrating another example of a step of forming an excitation electrode on one main surface of a piezoelectric substrate as a part of a step of manufacturing the piezoelectric device according to the first embodiment.

FIG. 5 is a schematic view showing a state in which the piezoelectric devices are individually cut out in the final step of the manufacturing process of the piezoelectric device according to the first embodiment.

FIG. 6 is a perspective view showing a configuration of a piezoelectric device according to a second embodiment of the present invention.

FIGS. 7A to 7D are cross-sectional views illustrating the configuration of a piezoelectric device according to a second embodiment in the order of main manufacturing steps;

FIG. 8 is a perspective view showing a configuration of a piezoelectric device according to a third embodiment of the present invention.

FIGS. 9A to 9D are cross-sectional views illustrating the configuration of a piezoelectric device according to a third embodiment in the order of main manufacturing steps;

FIG. 10 is a perspective view showing a configuration of a piezoelectric device according to a fourth embodiment of the present invention.

11A to 11E are cross-sectional views illustrating the configuration of a piezoelectric device according to a fourth embodiment in the order of main manufacturing steps.

FIG. 12A is a perspective view illustrating a configuration of a piezoelectric device according to a fifth embodiment of the present invention, with one principal surface facing upward;
(B) is a perspective view showing the configuration of the piezoelectric device with the other main surface facing the one main surface facing up.

13A to 13E are cross-sectional views illustrating the configuration of a piezoelectric device according to a fifth embodiment in the order of main manufacturing steps.

FIG. 14 is a block diagram illustrating an example of a configuration of a wireless device including a piezoelectric device according to a fifth embodiment of the present invention.

FIG. 15 is a perspective view showing an example of a configuration of a conventional energy trap type piezoelectric vibrator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 1M Base material of piezoelectric substrate 2 Groove 3a ・ 3b Exciting electrode 4a ・ 4b Vibration absorbing material 5 Rotating grindstone 6 Resist 7 Cutting machine 8 Metal mask 13a ・ 13b Exciting electrode 23a ・ 23b Exciting electrode 31 Antenna 32 Rx filter 33 ・35 mixer 34 primary IF filter 36 secondary IF filter 37 amplifier 38/39 reference frequency generation circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsu Takeda 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Yuki Sasaki 1006 Kadoma, Kazuma, Osaka Pref., Matsushita Electric Industrial Co., Ltd. CC09 CC13 DD01 FF01 HH02 HH05 MM08 MM11 MM14

Claims (15)

[Claims] 1. A piezoelectric substrate comprising: a piezoelectric substrate; and at least one set of excitation electrodes provided on one main surface of the piezoelectric substrate and another main surface opposite to the one main surface, for exciting thickness vibration of the piezoelectric substrate. In the piezoelectric device, a groove extending from one end of the main surface to the other end opposite to the one end is formed on at least one main surface of the one main surface and the other main surface of the piezoelectric substrate; A piezoelectric device, wherein at least one of the excitation electrodes is formed inside the groove. 2. The piezoelectric device according to claim 1, wherein a vibration absorbing material is provided on a side surface of the piezoelectric substrate parallel to the groove. 3. An excitation electrode formed inside the groove,
The piezoelectric device according to claim 1, wherein the width of the groove is equal to the width of the groove. 4. An excitation electrode formed inside the groove,
The piezoelectric device according to claim 1, wherein the width is smaller than the width of the groove. 5. The piezoelectric device according to claim 1, wherein a thickness of a portion of the piezoelectric substrate where the groove is formed is in a range of 5 μm to 300 μm. 6. The piezoelectric substrate according to claim 1, wherein the excitation electrode formed on one of the principal surface and the other principal surface of the piezoelectric substrate is formed over the entire surface of the principal surface. The piezoelectric device as described. 7. A main surface on which the excitation electrode is formed over the entire surface of one main surface and another main surface of the piezoelectric substrate,
The piezoelectric device according to claim 6, wherein the groove is formed, and an angle formed between a bottom surface and a side surface of the groove is an obtuse angle. 8. The piezoelectric substrate according to claim 1, wherein the piezoelectric substrate is formed by laminating a plurality of piezoelectric bodies, and the plurality of piezoelectric bodies are arranged such that polarization axes are alternately directed in opposite directions. Item 2. The piezoelectric device according to Item 1. 9. The piezoelectric substrate is formed by laminating a first piezoelectric body and a second piezoelectric body such that their polarization axes are opposite to each other, and the first piezoelectric body has a thickness vibration. 9. The piezoelectric device according to claim 8, wherein the groove is formed such that a thickness of a portion where the thickness vibration is excited is substantially equal to a thickness of a portion where the thickness vibration is excited in the second piezoelectric body. device. 10. A plurality of excitation electrodes are provided on at least one of the principal surface and the one principal surface of the piezoelectric substrate, and the plurality of excitation electrodes are arranged close enough to couple a thickness vibration mode. The piezoelectric device according to claim 1, wherein: 11. At least one main surface of a plate-shaped piezoelectric body,
A first step of forming a plurality of grooves substantially in parallel, and at least one set of excitation electrodes facing each other across the piezoelectric body, wherein at least one of the set of excitation electrodes is located inside the grooves. A third step of cutting the piezoelectric body by cutting substantially parallel to the groove between the plurality of grooves in the piezoelectric body, and a step of cutting the piezoelectric body. A fourth step of applying a vibration absorbing material to both side surfaces of the body parallel to the groove, and a fifth step of cutting the divided piezoelectric body at a substantially right angle to the groove.
And a method for manufacturing a piezoelectric device. 12. In the second step, a metal mask having an opening width larger than the width of the groove is used when forming the excitation electrode on the main surface of the piezoelectric body where the groove is formed. The method for manufacturing a piezoelectric device according to claim 11, wherein: 13. A plate-like piezoelectric body is formed by laminating a plurality of piezoelectric bodies so that their polarization axes are alternately oriented in opposite directions and joining them, and then polishing one main surface of the joined piezoelectric bodies. And a step of forming the groove on the other main surface of the bonded piezoelectric body opposite to the one main surface in the first step. The method of manufacturing a piezoelectric device according to claim 11. 14. A mobile communication device comprising the piezoelectric device according to claim 1. Description: 15. A mobile communication device comprising a piezoelectric device manufactured by the method for manufacturing a piezoelectric device according to claim 11. Description: