JP2002009583A - Piezoelectric device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end face reflection type piezoelectric device which can suppress chipping at the end face and the Q value is enhanced, and to provide a piezoelectric vibrator. SOLUTION: The piezoelectric device 1 consists of a base substrate 4 and a piezoelectric substrate 3 provided on the background substrate. The piezoelectric substrate has an exciting electrode 9 at least on one side and the depth of a chipping 6 at the end face 5 of the piezoelectric substrate with respect to the vibration produced through excitation by the exciting electrode is 1/10 of the wavelength λ of the vibration or below. The piezoelectric devices are manufactured by a process where the piezoelectric substrate and the background substrate are joined, and a process where individual piezoelectric devices are produced by cutting off the background substrate and also cutting off the piezoelectric substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric device and a method for manufacturing the same. In particular, the present invention relates to a piezoelectric device such as an end-face reflection type piezoelectric device or a piezoelectric vibrator in which the dimensional accuracy of the end surface affects characteristics, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a piezoelectric device using an elastic wave propagating through a piezoelectric substrate, there are an edge-reflection type surface acoustic wave piezoelectric device (hereinafter, referred to as an edge-reflection type piezoelectric device) utilizing reflection of an elastic wave on an end face of the substrate. Also, there is a strip-type piezoelectric vibrator (hereinafter, referred to as a piezoelectric vibrator) that cuts a substrate into a strip shape and makes the vibration of the thickness shear wave one-dimensional. These devices are widely used in filters for mobile communications, wideband voltage controlled oscillators (VCOs), and the like. In an end face reflection type piezoelectric device, it is known that the dimensional accuracy of the end face affects characteristics because an elastic wave propagates parallel to the surface of the substrate. On the other hand, in a piezoelectric vibrator, the vibration repeats reflection between the front and back surfaces in the thickness direction of the substrate,
It is known that when the piezoelectric vibrator has a specific width, unnecessary vibration approaches resonance, and adversely affects characteristics.

FIG. 7 shows a conventional end face reflection type piezoelectric device, and FIG. 8 shows a conventional piezoelectric vibrator. (A) of FIG.
In the end face reflection type piezoelectric device 1 shown in FIG. 1, the elastic wave excited by the excitation electrode 9 formed on the piezoelectric substrate 3 propagates to the end face 5 of the substrate and is reflected by the end face 5 to form a resonator.
Therefore, the resonance frequency and the loss amount are greatly affected by the accuracy of the end face. In particular, chipping 6, which is a chipped portion generated during manufacturing, adversely affects the characteristics. Further, in the conventional piezoelectric vibrator shown in FIG. 8, the thickness slip wave excited by the excitation electrodes 9a and 9b formed on both the front and back surfaces of the piezoelectric substrate 3 is reflected between the front and back surfaces of the substrate. Therefore, the dimensions of the end face do not seem to have a direct effect. However, unless the size of the piezoelectric vibrator 2 in the width direction is reduced, unnecessary vibrations are excited. On the other hand, when the width is reduced, the chipping 6 of the end face 5 adversely affects the vibration.

In these applications, piezoelectric single crystals or piezoelectric ceramics having a large electro-mechanical coupling coefficient are used. Among the piezoelectric single crystals, tantalum acid having a high Q value of vibration and excellent temperature characteristics is used. Lithium LiTaO ₃ single crystals are most often used. However, LiTaO ₃ single crystal,
Since it is a brittle material, its processing is difficult, and in cutting with a normal cutting device, chipping 6 at the cut end surface tends to increase. In the conventional LiTaO ₃ vibrator, when the width of the piezoelectric substrate 3 is cut to around 100 μm, significant chipping occurs on an end face or a crack occurs in the piezoelectric substrate 3 itself. there were. Further, even when the piezoelectric vibrator 2 can be manufactured, the surface roughness of the cut end face 5 affects the resonance characteristics, and the
The production of a vibrator of about z was the limit.

Further, there are spurious and Q values as values indicating the characteristics of the piezoelectric device. In piezoelectric devices,
When the relationship between the frequency of the vibration to be excited and its impedance is taken, a downward peak at which the impedance becomes a minimum near the resonance frequency is shown. There may be a small peak before and after the peak due to the resonance, which is called spurious. In order to obtain stable characteristics, it is desirable that there is almost no spurious. Further, fr / Δf (hereinafter referred to as a Q value) represented by the resonance frequency fr and the half width Δf of the peak at the resonance frequency is used as a value indicating the sharpness of the vibration system. The larger the Q value, the sharper the vibration system is.

[0006]

As described above, when a piezoelectric substrate is cut by a normal cutting method in manufacturing a piezoelectric device, a decrease in dimensional accuracy at a cut end face, an increase in spuriousness, a deterioration in Q, a decrease in manufacturing yield, etc. Was a problem.

That is, in the case of an end face reflection type piezoelectric device,
Generally, the resonance wavelength λ of the piezoelectric device is determined by the period of the excitation electrodes formed on the surface (the distance between adjacent electrodes is equivalent to １ ／ of the wavelength λ at which excitation is performed). Therefore, the end face is required to have a dimensional accuracy of half that (1/8 of the excited wavelength λ). On the other hand, in the case of a piezoelectric vibrator, the resonance wavelength λ is determined by the thickness of the piezoelectric substrate, but it is required to cut the width to several times the thickness. The accuracy becomes stricter as the frequency of the device increases. Therefore, in the conventional cutting method that generates chipping exceeding a few μm at a minimum,
It was difficult to obtain the required dimensional accuracy. Moreover, there is a problem in that cutting speed is reduced when chipping is to be minimized, and productivity is deteriorated.

Accordingly, an object of the present invention is to provide an end face reflection type piezoelectric device and a piezoelectric vibrator in which chipping of a cut end face is suppressed, spurious generation is suppressed, and a Q value is improved, and a method of manufacturing the same.

[0009]

The above object can be attained by the following present invention.

That is, a piezoelectric device according to the present invention is a piezoelectric device comprising a base substrate and a piezoelectric substrate provided on the base substrate, wherein the piezoelectric substrate has an excitation electrode on at least one surface. The depth of chipping at the end face of the piezoelectric substrate related to the vibration excited by the excitation electrode is 1/10 or less of the wavelength λ of the vibration.

Further, the piezoelectric device according to the present invention is the piezoelectric device, wherein the piezoelectric substrate is a piezoelectric single crystal.

Further, the piezoelectric device according to the present invention is the piezoelectric device, wherein the piezoelectric substrate is made of LiTaO.
It is characterized by being an X plate of _three single crystals.

Still further, the piezoelectric device according to the present invention is the above-mentioned piezoelectric device, wherein the undersubstrate is made of a material having an isotropic coefficient of thermal expansion and capable of laser cutting.

Further, the piezoelectric device according to the present invention is the piezoelectric device, wherein the base substrate is a single-crystal substrate having a cleavage property, and at least a pair of opposed end faces of the piezoelectric substrate and the single-crystal substrate. And a pair of cleavage planes facing each other are the same plane.

Further, the piezoelectric device according to the present invention is the piezoelectric device, wherein the base substrate and the piezoelectric substrate are directly bonded.

Still further, the piezoelectric device according to the present invention is the above-mentioned piezoelectric device, wherein the undersubstrate and the piezoelectric substrate are mutually bonded by at least one of an oxygen atom, a hydroxyl group and a water molecule. It is characterized by being combined.

Further, the piezoelectric device according to the present invention is the piezoelectric device, wherein the piezoelectric substrate is provided with an excitation electrode on one surface, and is an end face reflection type piezoelectric device.

Further, the piezoelectric device according to the present invention is the piezoelectric device, wherein the piezoelectric substrate is provided with excitation electrodes on each of two surfaces.

The method for manufacturing a piezoelectric device according to the present invention comprises:
Bonding a piezoelectric substrate and a base substrate, and cutting the base substrate, cutting the piezoelectric substrate together with cutting the base substrate, and forming individual piezoelectric devices. I do.

Further, the method for manufacturing a piezoelectric device according to the present invention is a method for manufacturing a piezoelectric device, comprising the steps of: joining the piezoelectric substrate and the base substrate; and cutting from the base substrate. The method further comprises a step of processing the piezoelectric substrate into a thin plate and a step of forming an excitation electrode on the piezoelectric substrate.

The method for manufacturing a piezoelectric device according to the present invention is the method for manufacturing a piezoelectric device, wherein the base substrate is made of a material having an isotropic coefficient of thermal expansion. The piezoelectric substrate is cut by a laser cutting method from the base substrate side.

Further, the method of manufacturing a piezoelectric device according to the present invention is the method of manufacturing a piezoelectric device, wherein a cleavage direction of the piezoelectric substrate is determined by using a cleavage single crystal substrate as the base substrate. The piezoelectric substrate and the base substrate are attached so that one of the cleavage directions of the base substrate coincides with each other, and the piezoelectric substrate is cut by cleaving a single crystal from the base substrate side.

Still further, the method of manufacturing a piezoelectric device according to the present invention is a method of manufacturing the piezoelectric device, wherein the step of bonding the piezoelectric substrate and the base substrate includes the step of bonding the piezoelectric substrate and the base substrate. It is characterized by being joined to each other by direct joining.

Further, the method for manufacturing a piezoelectric device according to the present invention is the method for manufacturing a piezoelectric device, wherein the step of directly bonding the piezoelectric substrate and the base substrate includes bonding the base substrate and the piezoelectric substrate. Washing the respective surfaces to be joined with a solution containing water and performing a hydrophilic treatment, and contacting the hydrophilically treated surfaces of the base substrate and the piezoelectric substrate with each other. I do.

Furthermore, a method of manufacturing an edge-reflection type piezoelectric device according to the present invention is the method of manufacturing a piezoelectric device, wherein the piezoelectric device is an edge-reflection type piezoelectric device.

Still further, the method of manufacturing a piezoelectric device according to the present invention is the method of manufacturing a piezoelectric device, wherein the step of bonding the piezoelectric substrate and the underlying substrate includes exciting at least one surface of the piezoelectric substrate. A step of providing an electrode, a step of providing a vibration space in which the excitation electrode can vibrate on a base substrate for cutting assistance, and a step of providing the excitation electrode so as to house the excitation electrode in the vibration space formed in the base substrate. Joining the formed one surface and the base substrate.

Further, a method of manufacturing a piezoelectric vibrator according to the present invention is the method of manufacturing a piezoelectric device, wherein the piezoelectric device is a piezoelectric vibrator.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) According to the first embodiment
X-cut LiTaO as an end face reflection type piezoelectric device
_Three(Includes those cut on surfaces inclined several degrees from the X plate.
The same applies hereinafter. ) Using the substrate as the piezoelectric substrate 3
An example in which glass is used for the auxiliary base substrate 4 will be described.
You. FIG. 1 shows an end face reflection type piezoelectric device according to the first embodiment.
Vice plan view (a) and its A-A 'line sectional view (b)
Is shown.

The end face reflection type piezoelectric device 1 shown in FIG.
An extremely thin piezoelectric substrate 3 and a base substrate 4 made of glass are joined by an adhesive, and an excitation electrode 9 is provided on the piezoelectric substrate 3. The adhesive layer between the piezoelectric substrate 3 and the underlying substrate 4 is very thin, and the distance between the piezoelectric substrate 3 and the underlying substrate 4 is substantially close to zero. The piezoelectric substrate 3 is a base substrate 4
, It is possible to work very thin. The thinned piezoelectric substrate 3 is placed on the undersubstrate 4 side.
When a crack is generated by a predetermined means, the piezoelectric substrate 3
And the cut size of the base substrate 4 and the cut size of the piezoelectric substrate 3 become substantially equal. Further, since the starting point of the cutting is not on the piezoelectric substrate 3 but proceeds from the base substrate 4 bonded to the piezoelectric substrate 3, chipping generated on the cut end surface 5 of the piezoelectric substrate 3 in the obtained end face reflection type piezoelectric device 1 is extremely low. Can be small and small. In this end face reflection type piezoelectric device 1, the cutting end face 5 preferably has a chipping depth of 1/1 of the wavelength λ of the vibration to be excited.
0 or less, more preferably 1/1 / wavelength λ of the vibration to be excited.
20 or less is desirable. The Q value is desirably 1000 or more.

Hereinafter, an example of a method of manufacturing the end face reflection type piezoelectric device 1 shown in the first embodiment will be described. Sectional views of each step are shown in FIGS.

First, as shown in FIG. 2A, a 200 μm-thick glass substrate having an isotropic coefficient of thermal expansion was used as a base substrate 4 for assisting cutting, and a piezoelectric substrate 3 was used.
A 50 μm-thick lithium tantalate LiTaO ₃ is prepared. At this time, even if the thickness of the piezoelectric substrate 3 is initially thick, it can be polished later to reduce the thickness to a desired thickness.

As the piezoelectric substrate 3, a piezoelectric single crystal substrate is preferable, and for example, lithium tantalate LiTaO ₃ , lithium niobate LiNbO ₃ , quartz, or the like can be used. Specific cut angles include, for example, lithium tantalate LiTaO _{3 of} an X plate or a 36 ° rotating Y plate, lithium niobate LiNbO _{3 of} a 41 ° rotating Y plate, ST
A cut quartz plate or the like can be used. When a piezoelectric single crystal substrate is used as the piezoelectric substrate 3, preferably, one of the cutting direction and the cleavage direction of the piezoelectric single crystal substrate is made to coincide.

The thickness of the piezoelectric substrate 3 is preferably 10 to 1
A range of 00 μm, more preferably a range of 10 to 50 μm is desirable. Note that, at the time of bonding with the base substrate 4, the thickness is preferably 500 μm or less, more preferably 300 μm or less. In this case, the thickness can be reduced by polishing or the like after bonding with the base substrate 4.

As the base substrate 4 for assisting cutting, glass, silicon, alumina, ceramics and the like can be used as those having an isotropic coefficient of thermal expansion. The coefficient of thermal expansion of the base substrate 4 does not need to be strictly isotropic, but it is sufficient if it is substantially isotropic. The thickness of the base substrate is preferably 300 to 500 μm.
Is desirable.

Next, as shown in FIG. 2B, the piezoelectric substrate 3 and the base substrate 4 for cutting assistance are joined by an adhesive. In this case, it is desirable that the thickness of the adhesive layer is made sufficiently thin to several μm or less by applying pressure or using an adhesive having a low viscosity. As the adhesive, organic, inorganic and the like, but not particularly limited, for example,
UV-curable acrylic resin or the like can be used. Further, the piezoelectric material 3 may be formed on the base substrate 4 by a vapor phase synthesis method such as an evaporation method, a sputtering method, and a CVD method.
Conversely, the base substrate material 4 may be formed on the piezoelectric substrate 3 by the above-described vapor phase synthesis method or the like.

Thereafter, as shown in FIG. 2C, an excitation electrode 9 is formed on the piezoelectric substrate 3. After that, the base substrate 4 for cutting assistance is cut with a cutting width of 0 by the laser cutting means 7.

Various methods can be considered as a method for cutting the substrate. As one method, in this embodiment, the laser cutting method is used. Here, the laser cutting method utilizes the thermoelastic force generated inside the object by laser irradiation,
This is a technique for cutting an object with a cutting width of substantially zero. Such a thermoelastic force is generated by the carbon dioxide CO concentrated on the surface of the object.
₍₂₎ Generated by the heat of the laser, it enables a depth of several μm to complete cutting. Since the cutting width is substantially 0, there is no waste of material such as evaporation of the object as in normal laser heating cutting, and the number of elements that can be obtained from one substrate is maximized. Can be. Devices using this technology are already commercially available,
It is readily available.

Here, since the laser cutting method is a cutting by a thermoelastic force induced in the substrate, it is preferable to perform the laser cutting for a substrate made of a material having good isotropic thermal expansion coefficient. For this reason, when the substrate has an anisotropic coefficient of thermal expansion or has a cleavage property, and the cutting is performed in a direction shifted from the cleavage plane, the cutting quality is deteriorated. More specifically, large chipping occurs on the cut end face,
Breaking in unexpected directions may occur. Piezoelectric substrates rarely have an isotropic coefficient of thermal expansion, and for example, lithium tantalate LiTaO ₃ single crystal has a specific cleavage plane, so that it is not possible to obtain a desired cutting accuracy by a laser cutting method. Generally difficult.

Therefore, for example, in this embodiment,
When glass having an isotropic coefficient of thermal expansion is used as the base substrate 4, it can be easily cut by a laser cutting method. The cutting depth at this time is desirably set to a depth that substantially cuts the glass substrate 4 but does not reach the piezoelectric substrate 3. Thereafter, if the glass portion is divided by applying a stress that divides the glass, the crack is formed on the piezoelectric substrate 3.
, And the cut end face 5 of the piezoelectric substrate 3 in which the base substrate 4 and the piezoelectric substrate 3 are parallel and continuous without any step is obtained. If the cut end face of the piezoelectric substrate 3 is a cleavage plane, a better end face can be obtained. Cut to the same outer shape.

(Second Embodiment) Next, a piezoelectric vibrator according to a second embodiment will be described. The piezoelectric vibrator according to the second embodiment uses an X-cut LiTaO ₃ substrate for the piezoelectric substrate 3 and a similar X-cut LiT
An aO ₃ substrate is used. 3A is a plan view of the piezoelectric vibrator 2, FIG. 3B is a cross-sectional view taken along the line BB ′ of FIG.
FIG. 3C is a sectional view taken along line CC ′ of FIG.

The piezoelectric vibrator according to the second embodiment has a pair of excitation electrodes 9a and 9b formed on the piezoelectric substrate 3. The excitation electrodes 9a and 9b are formed over the entire width of the piezoelectric vibrator. Further, the excitation electrode 9a is formed on the surface of the piezoelectric substrate 3, while the excitation electrode 9b is
It is formed on the opposite surface.

Each of the piezoelectric substrate 3 and the underlying substrate 4 is L
It is an X plate of iTaO ₃ single crystal. The front and back surfaces of the piezoelectric substrate 3 are both X-cut surfaces. Similarly, both the front surface and the back surface of the base substrate 4 are X-cut surfaces,
A groove is formed in the joint surface with the piezoelectric substrate 3 as a vibration space 11 for the excitation electrode 9b to vibrate. Further, the piezoelectric substrate 3 and the underlying substrate 4 are joined by direct joining with their crystal axes aligned. Since the piezoelectric substrate 3 and the underlying substrate 4 joined by direct joining are integrated by joining without using an adhesive, when a crack is generated by stress or the like from the underlying substrate side, the mutual substrates by the adhesive layer are formed. There is no shift in the crack surface between them, and smooth cutting with more continuous cracks is possible.

The side surface that is the cut end surface 5 is L
It is desirable that the plane be substantially parallel to the cleavage plane of the iTaO ₃ single crystal. In this case, it is preferable that the side surface of the base substrate 4 as the cut end surface 5 is also a plane substantially parallel to the cleavage plane of the LiTaO ₃ single crystal. Specifically, for example, as the side surface that is the cut end surface 5, the piezoelectric substrate 3 (LiTaO ₃ X
The angle of the plate from the Y axis is a surface of -57 ° ± 1 ° when the Z axis direction is expressed as positive. That is, the angle α formed between the side surface that is the cut end face 5 and the Y axis of the piezoelectric substrate 3 is −57 ° ± 1 ° in the same manner. The cleavage plane of the X-cut LiTaO ₃ single crystal is a plane substantially at −57 ° from the Y axis, but if the deviation from the cut end face 5 is within about ± 1 °, chipping during cutting is sufficiently reduced. (The same applies hereinafter).

In the piezoelectric vibrator 2 according to the second embodiment,
Since the cutting direction of the base substrate 4 and the cleavage direction of the crystal substantially match, the division of the piezoelectric substrate 3 can be performed more accurately, and chipping of the cut end face 5 can be suppressed, so that the surface roughness is minimized. Therefore, it is easy to increase the resonance frequency of the piezoelectric vibrator 2 and the production yield is improved. Further, it is possible to obtain a piezoelectric vibrator in which unnecessary vibration is hardly excited and large spurious is not generated.

In the piezoelectric vibrator 2 according to the second embodiment, the chipping depth of the cut end face 5 is preferably not more than 1/10 of the wavelength λ of the vibration to be excited, and more preferably less than 1/10 of the wavelength λ of the vibration to be excited. 1/20 or less is desirable. Also,
The Q value is preferably 1000 or more, and more preferably 2000 or more.

Hereinafter, an example of a method for manufacturing the piezoelectric vibrator 2 according to the second embodiment will be described. Sectional views of each step are shown in FIGS.

First, as shown in FIG. 4 (a), a 200 μm-thick
m of lithium tantalate LiTaO ₃ single crystal substrate 4
As the piezoelectric substrate 3, a 50 μm-thick lithium tantalate LiTaO ₃ single crystal substrate 3 is prepared. At this time, a groove for the vibration space 11 is formed in advance on the base substrate 4 for cutting assistance. Excitation electrodes 9b are formed in advance on the surface of the piezoelectric substrate 3 that is to be joined to the base substrate 4.

As the cutting-assisting base substrate 4, a single-crystal substrate having a cleavage property is, for example, lithium tantalate LiTaO ₃ , lithium niobate LiNbO ₃ ,
Si crystal or the like can be used.

Next, as shown in FIG.
And the base substrate 4 for cutting assistance are joined by direct joining. The method of bonding by direct bonding includes the steps of (i) cleaning the respective surfaces of the piezoelectric substrate 3 and the base substrate 4 to be bonded, and then washing the surfaces with a solution containing water to make the surfaces hydrophilic. (Ii) a step of making close contact using the van der Waals force that acts when the respective surfaces of the piezoelectric substrate 3 and the underlying substrate 4 that have been subjected to the hydrophilic treatment are brought into contact with each other.

In the direct bonding, after the above-mentioned adhesion step (ii), a step of performing a heat treatment may be performed if desired. It is desirable to perform the heat treatment because the heat treatment further strengthens the bonding.

In the direct bonding, the bonding between the two substrates is an interatomic bonding using at least one of an oxygen atom, a hydroxyl group, and a water molecule. Accordingly, the substrates are substantially directly bonded, and the cracks generated in the base substrate 4 for assisting cutting can be directly transmitted to the piezoelectric substrate side. The solution used for the hydrophilization treatment may be any solution containing water, and is preferably a mixture of ammonia, aqueous hydrogen peroxide and water in a ratio of 1:
Solutions containing a 1: 6 ratio are preferred.

In the case where a single crystal substrate having a cleavage property is used as the base substrate 4 for assisting cutting, the method of bonding the piezoelectric substrate 3 and the base substrate 4 by the direct bonding is the same as that of the direct bonding. Alternatively, a case using an adhesive can be used.

Thereafter, as shown in FIG. 4C, a break groove 8 is formed on the back surface of the cutting assistance base substrate 4 opposite to the bonding surface with the piezoelectric substrate 3. It is desirable that the break grooves 8 be formed so as to coincide with the cleavage directions of the base substrate 4 for cutting assistance and the piezoelectric substrate 3.

As a method for cutting the piezoelectric substrate, the piezoelectric substrate 3
In the case where is a single crystal substrate, there is a method of cutting using a cleavage unique to the single crystal. Since the cleavage plane obtained by cleavage inherent in the single crystal is very smooth and the chipping of the cut end face 5 is small, it is preferable to use cleavage as a cutting method. However, in order to cause cleavage, it is necessary to apply a stress. In this case, for example, when the break groove 8 is provided directly on the piezoelectric substrate 3, unintended cleavage is performed in a direction different from the desired cleavage direction. May occur. This occurs because a single crystal usually has multiple cleavage directions. Further, since the piezoelectric single crystal substrate is a brittle material, it is easily damaged at the time of cleavage. Therefore, when the piezoelectric substrate 3 is cut by direct cleavage, the cut end face 5 is rather cut.
Chipping may increase.

In the second embodiment, instead of directly cleaving the piezoelectric substrate 3, first, a break groove 8 is provided in the cutting assist base substrate 4, and a stress is applied to the break groove 8 to apply a stress to the base substrate. 4 and the piezoelectric substrate 3
Are also cleaved to divide each piezoelectric vibrator 2 into a desired width. At this time, the progress of the cleavage to the base substrate 4 is transmitted to the piezoelectric substrate 3 to serve as a trigger for cleavage of the piezoelectric substrate 3, and the cut end face 5 can be made smoother. As a result, a cut end face 5 with little chipping is obtained.

Since the vibration space 11 is provided between the base substrate 4 for assisting cutting and the piezoelectric substrate 3,
Cracks from the base substrate 4 for cutting assistance do not propagate directly. Therefore, the cutting is performed at a portion where the base substrate 4 and the piezoelectric substrate 3 are in close contact with each other.

(Third Embodiment) FIG. 5 is a plan view (a) of an end face reflection type piezoelectric device 1 according to a third embodiment, and FIG.
The sectional view taken along the line DD ′ is shown in FIG. The end-face reflection type piezoelectric device 1 according to the third embodiment uses a LiTaO ₃ single crystal substrate as the base substrate 4 as compared with the end-face reflection type piezoelectric device according to the first embodiment. The difference is that the piezoelectric substrate 3 is cleaved by cleavage from the break grooves 8 provided in the substrate 4 and divided into respective piezoelectric devices.

In the end face reflection type piezoelectric device 1 according to the third embodiment, since the cutting direction of the base substrate 4 and the cleavage direction of the crystal substantially match, the division of the piezoelectric substrate 3 can be performed more accurately and the cut end face 5 Chipping can be suppressed, and the surface roughness is minimized. Therefore, the end face reflection type piezoelectric device 1
The resonance frequency can be easily increased, and the manufacturing yield can be improved. Further, it is possible to obtain the end face reflection type piezoelectric device 1 in which unnecessary vibration is hardly excited and large spurious is not generated.

In the end face reflection type piezoelectric device 1 according to the third embodiment, the cutting depth of the cut end face 5 is preferably 1/10 or less of the wavelength λ of the exciting vibration, and more preferably the wavelength of the exciting vibration. 1/20 or less of λ is desirable. The Q value is preferably 1000 or more.

(Fourth Embodiment) FIG. 6 is a plan view (a) of a piezoelectric vibrator 2 according to a fourth embodiment and its EE ′.
A cross-sectional view taken along the line (b) and a cross-sectional view taken along the line FF ′ (c) are shown. Compared with the piezoelectric vibrator according to the second embodiment, the piezoelectric vibrator 2 according to the fourth embodiment uses glass that has an isotropic coefficient of thermal expansion as a base substrate 4 and can be laser cut off. The second embodiment is different from the first embodiment in that the base substrate 4 is cut by a laser cutting method, and the piezoelectric substrate 3 is cut and divided into respective piezoelectric devices.

In the piezoelectric vibrator 2 according to the fourth embodiment, since the piezoelectric substrate 3 is supported by the underlying substrate 4, it can be processed very thinly. When a crack is generated from the substrate 4 side by a predetermined means, the crack reaches the piezoelectric substrate 3 as it is, and the cut size of the base substrate 4 and the cut size of the piezoelectric substrate 3 become substantially equal. Further, since the starting point of the cutting is not on the piezoelectric substrate 3 and the cutting proceeds from the base substrate 4 bonded to the piezoelectric substrate 3, chipping generated on the cut end face 5 of the piezoelectric substrate 3 in the obtained piezoelectric vibrator 2 is extremely low. Can be small and small.

In the piezoelectric vibrator 2 according to the fourth embodiment, the chipping depth of the cut end face 5 is preferably not more than 1/10 of the wavelength λ of the vibration to be excited, and more preferably less than 1/10 of the wavelength λ of the vibration to be excited. 1/20 or less is desirable. Also,
The Q value is preferably 1000 or more, and more preferably 2000 or more.

Although the embodiments of the present invention have been described above by way of examples, the present invention is not limited to the above-described embodiments, but can be applied to other embodiments based on the technical idea of the present invention. it can.

For example, the present invention can be applied to a ladder / grating type filter in which a plurality of piezoelectric vibrators are connected in series and parallel or a filter in which a plurality of multi-mode vibrators are connected. The effect of is obtained.

[0066]

As described in detail above, the piezoelectric device according to the present invention is a piezoelectric device comprising a base substrate and a piezoelectric substrate provided on the base substrate, wherein the piezoelectric substrate has at least one of Has an excitation electrode on the surface thereof, and the depth of chipping at the cut end surface of the piezoelectric substrate related to the vibration excited by the excitation electrode is the wavelength λ of the vibration.
Since the spurious is suppressed, the Q value is preferably 1000 or more.

Further, according to the method of manufacturing a piezoelectric device according to the present invention, a step of bonding the piezoelectric substrate and the underlying substrate includes the steps of:
Cutting from the base substrate side and cutting the piezoelectric substrate together with cutting the base substrate to produce individual piezoelectric devices, so that the piezoelectric substrate is supported by the base substrate, When a crack is generated from the base substrate side by a predetermined means, the crack reaches the piezoelectric substrate as it is, and the cutting size of the base substrate and the cutting of the piezoelectric substrate are reduced. The sizes are approximately equal. In addition, since the starting point of the cutting is not on the piezoelectric substrate and the cutting proceeds from the underlying substrate bonded to the piezoelectric substrate, chipping generated on the cut end face of the piezoelectric substrate in the obtained piezoelectric device is very small and small. it can.

Further, according to the method of manufacturing a piezoelectric device according to the present invention, an undersubstrate made of a material having an isotropic coefficient of thermal expansion is used as an undersubstrate, and a laser cutting method is used from the undersubstrate side. If the cutting is performed and a stress is applied to divide the base substrate made of a material having an isotropic coefficient of thermal expansion such as glass and the substrate is divided, the crack reaches the piezoelectric substrate, and the cut end face with little chipping is formed. can get.

Further, according to the method of manufacturing a piezoelectric device of the present invention, a single crystal substrate having a cleavage property is used as a base substrate, and one of a cutting direction of the piezoelectric substrate and a cleavage direction of the base substrate is changed. By bonding the piezoelectric substrate and the base substrate so as to coincide with each other and performing cutting by cleavage of the single crystal from the base substrate side, the progress of cleavage to the base substrate is transmitted to the piezoelectric substrate. , And the smoothness of the cut end surface can be obtained. As a result, a cut end face with less chipping can be obtained.

According to the method of manufacturing a piezoelectric device according to the present invention, the piezoelectric substrate and the base substrate are bonded to each other by direct bonding, so that they are integrated without using an adhesive. There is no adhesive layer on the surface, and when a crack is generated by stress or the like from the base substrate side, there is no shift between the cracked surfaces between the substrates, and smooth cutting with more continuous cracks is possible.

[Brief description of the drawings]

FIG. 1A is a plan view of an end face reflection type acoustic wave device according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA ′.

FIG. 2 is a side sectional view showing a manufacturing process of the end face reflection type piezoelectric device according to the first embodiment of the present invention, in which (a) a step of preparing a piezoelectric substrate and a base substrate for cutting assistance;
(B) a step of bonding the piezoelectric substrate and the base substrate with an adhesive, and (c) a step of providing the excitation electrode 9 on the piezoelectric substrate.
(D) A step of cutting a piezoelectric substrate by generating a crack from a base substrate by a laser cutting method, and (e) a side cross-sectional view of the obtained end face reflection type piezoelectric device.

FIG. 3A is a plan view of a piezoelectric vibrator according to a second embodiment of the present invention, FIG. 3B is a cross-sectional view taken along line BB 'along the vibration propagation direction, and FIG. It is a sectional view (c) along line C '.

FIG. 4 is a side sectional view showing a manufacturing process of a piezoelectric vibrator according to a second embodiment of the present invention, in which (a) a step of preparing a piezoelectric substrate and a base substrate for cutting assistance, and (b) a piezoelectric substrate. A step of directly bonding the substrate and the underlying substrate, (c) a step of providing a break groove in the underlying substrate, and (d) a side sectional view of a piezoelectric vibrator obtained by cleavage from the break groove of the underlying substrate. is there.

5A is a plan view of an end face reflection type piezoelectric device according to a third embodiment of the present invention, and FIG. 5B is a sectional view taken along line DD ′ of FIG.

FIG. 6A is a plan view of a piezoelectric vibrator according to a fourth embodiment of the present invention, FIG. 6B is a cross-sectional view taken along the line EE ′ along the vibration propagation direction, and FIG. It is a sectional view (c) of an F 'line.

FIG. 7A is a plan view of a conventional end face reflection type piezoelectric device, and FIG. 7B is a sectional view taken along line GG ′ of FIG.

FIG. 8A is a plan view of a conventional piezoelectric vibrator, and FIG. 8B is a cross-sectional view taken along line HH ′ along a vibration propagation direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 End-reflection type piezoelectric device 2 Piezoelectric vibrator 3 Piezoelectric substrate 4 Base substrate 5 Cutting end surface 6 Chipping 7 Laser 8 Break groove 9, 9a, 9b Excitation electrode 11 Vibration space 12 Crack

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsunori Morikiki 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 5J097 AA14 BB11 HA07 HA08 KK09 5J108 AA01 AA07 BB01 CC04 KK01 MM11

Claims (18)

[Claims] 1. A piezoelectric device comprising a base substrate and a piezoelectric substrate provided on the base substrate, wherein the piezoelectric substrate has an excitation electrode on at least one surface, and is excited by the excitation electrode. A piezoelectric device, wherein a depth of chipping at an end face of the piezoelectric substrate relating to vibration is 1/10 or less of a wavelength λ of the vibration. 2. The piezoelectric device according to claim 1, wherein the piezoelectric substrate is a piezoelectric single crystal. 3. The piezoelectric vibrator according to claim 2, wherein the piezoelectric substrate is an X plate of LiTaO ₃ single crystal. 4. The piezoelectric device according to claim 1, wherein the base substrate is made of a material having an isotropic coefficient of thermal expansion and capable of being laser cut off. 5. The semiconductor device according to claim 5, wherein the base substrate is a single-crystal substrate having a cleavage property, and at least a pair of opposite end faces of the piezoelectric substrate and a pair of opposite cleavage faces of the single-crystal substrate are on the same plane. The piezoelectric device according to any one of claims 1 to 3, characterized in that: 6. The piezoelectric device according to claim 1, wherein the undersubstrate and the piezoelectric substrate are bonded by direct bonding. 7. The piezoelectric device according to claim 6, wherein the undersubstrate and the piezoelectric substrate are directly bonded to each other via at least one of an oxygen atom, a hydroxyl group, and a water molecule. 8. The end face reflection type piezoelectric device according to claim 1, wherein an excitation electrode is provided on one surface of the piezoelectric substrate. 9. The piezoelectric vibrator according to claim 1, wherein an excitation electrode is provided on each of the opposing surfaces of the piezoelectric substrate. 10. A step of joining a piezoelectric substrate and an undersubstrate, and a step of cutting from the undersubstrate side and cutting the undersubstrate and cutting the piezoelectric substrate to produce individual piezoelectric devices. A method for manufacturing a piezoelectric device. 11. A step of processing the piezoelectric substrate into a thin plate between the step of joining the piezoelectric substrate and the base substrate and the step of cutting from the base substrate side; The method for manufacturing a piezoelectric device according to claim 10, further comprising a step of forming an electrode. 12. The method according to claim 1, wherein the undersubstrate is made of a material having an isotropic thermal expansion coefficient, and the piezoelectric substrate is cut from the undersubstrate by a laser cutting method. A method for manufacturing a piezoelectric device according to claim 10. 13. The method according to claim 13, wherein a single crystal substrate having a cleavage property is used as the base substrate, and the piezoelectric substrate and the base substrate are bonded so that one of a cutting direction of the piezoelectric substrate and a cleavage direction of the base substrate coincides with each other. The method of manufacturing a piezoelectric device according to claim 10, wherein the piezoelectric substrate is cut by attaching a single crystal and cleaving the single crystal from the base substrate side. 14. The method according to claim 10, wherein the step of bonding the piezoelectric substrate and the base substrate includes bonding the piezoelectric substrate and the base substrate to each other by direct bonding.
14. The method for manufacturing a piezoelectric device according to any one of items 13 to 13. 15. The step of bonding the piezoelectric substrate and the base substrate to each other by the direct bonding, wherein the surfaces to be bonded of the base substrate and the piezoelectric substrate are washed with a solution containing water and hydrophilic. The method for manufacturing a piezoelectric device according to claim 14, comprising a step of performing a hydrophilizing treatment, and a step of bringing the surfaces of the base substrate and the piezoelectric substrate that have been subjected to the hydrophilizing treatment into close contact with each other. 16. The method according to claim 10, wherein the piezoelectric device is an edge-reflection type piezoelectric device. 17. A step of bonding the piezoelectric substrate and the underlying substrate, the step of providing an excitation electrode on at least one surface of the piezoelectric substrate, and the step of causing the excitation electrode to vibrate on a cutting assisting underlying substrate. Providing a space, and joining the one surface on which the excitation electrode is formed and the undersubstrate so as to house the excitation electrode in the vibration space formed in the undersubstrate. The method for manufacturing a piezoelectric device according to any one of claims 10 to 15. 18. The method according to claim 17, wherein the piezoelectric device is a piezoelectric vibrator.