JP2001036377A - Piezoelectric device and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy sealed piezoelectric device, which copes with high frequency, suppresses the occurrence of unwanted spurious signals, improves operability and can be efficiently produced, and production thereof. SOLUTION: At the terminal part of a strip-shaped thin plate part 1 composed of a piezoelectric substrate 3, a support part 2 thicker than this part 1 is formed. Exciting electrodes 4a and 4b are formed on both the sides of the thin plate part 1. By thinning the thin plate part 1, frequency increase is realized. By providing he support part 2, a vibration space is secured and operability is improved. Furthermore, by forming the exciting electrodes 4a and 4b over the full width of the thin plate part 1, the occurrence of spurious signal is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-mode piezoelectric filter or a ladder-type filter used for a high-frequency oscillator used for generating a clock signal of a personal computer peripheral device or 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 that can be used for a piezoelectric filter and the like, 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, there has been a strong demand for small and high-frequency vibrators and small and wideband IF filters. Conventionally, energy-trap type piezoelectric vibrators and piezoelectric filters have been used for these vibrators and filters, and smaller and wider-band ones have been demanded.
Quartz filters have been most widely used as energy trapping type piezoelectric filters, but when quartz is used, the electro-mechanical coupling coefficient of the material is small,
It is difficult to configure a filter having a wide band. Therefore, in these applications, piezoelectric single crystals and piezoelectric ceramics having a large electro-mechanical coupling coefficient are used, but these generally show brittle properties, and are difficult to etch and thin.
Even if it can be made thin, it becomes difficult to handle, and at high frequencies,
It was difficult to form a highly accurate vibrator and filter. In addition, when the size becomes small, spurious characteristic to the element shape easily occurs, and it is difficult to obtain a vibrator or a filter having good characteristics.

An example of a conventional piezoelectric vibrator will be described with reference to FIG. FIG. 11A is a perspective view illustrating a schematic configuration of a piezoelectric vibrator. In the figure, 11 is a piezoelectric substrate, 12
Numeral denotes an excitation electrode, and 13 denotes a conductive paste provided for establishing conduction between the excitation electrode 12 and a terminal taken out. Although not shown, the excitation electrode is similarly formed on the lower surface of the piezoelectric substrate 11. The excitation electrodes on the upper and lower surfaces are electrically connected to the conductive pastes 13 on the opposite sides, respectively. FIG. 11B is a side view of the device of FIG. 14 is a space for vibration, and 15 is a fixed plane. FIGS. 11A and 11B show the case where the element is held by the conductive paste 13 on both sides, but there is also a configuration in which the element is held on one side as shown in FIG. 11C. In FIG. 11C, two conductive pastes 13 are insulated and attached to one end, and the upper and lower excitation electrodes 1 of the piezoelectric substrate 11 are respectively provided.
2 is connected.

As shown in FIG. 11, in a conventional piezoelectric vibrator, when the frequency is increased and the element is reduced in size, a conductive paste 13 is disposed immediately adjacent to the excitation electrode 12 and becomes conductive during application or curing. There is a problem that the conductive paste 13 flows out onto the excitation electrode 12 and even main vibrations are disturbed. When the vibrator is held on one side as shown in FIG. 11C, the piezoelectric substrate 11 of the element is fixed to the fixed plane 1.
There is a problem that it is difficult to fix the element 5 in parallel with the element 5, and if the element 5 is fixed at an angle, the vibration of the element is hindered.
When the vibration is inhibited, the characteristics of the vibrator are Q and CI.
Appears as a decrease in value. In the case of a filter, it appears as an increase in insertion loss and a decrease in out-of-band attenuation. Also,
In the case of mounting as shown in FIG. 11C, it is difficult to connect the excitation electrodes on the front and back with a conductive paste without short-circuiting.

[0005]

In an energy confinement type piezoelectric device using thickness vibration, the thickness of the element is inversely proportional to the resonance frequency of the element. It is required to reduce the thickness and to obtain an element which is easy to handle even if it is thin. Further, it is important to ensure a space for vibration. Further, how to control the level of spurious is the biggest issue.

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

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described conventional problems, and provides a piezoelectric device capable of suppressing unnecessary spurious components and corresponding to a higher frequency, and manufacturing a piezoelectric device capable of easily manufacturing such a piezoelectric device. An object of the present invention is to provide a method, and further to provide a mobile communication device using such a piezoelectric device.

[0008]

In order to achieve the above object, the present invention has the following arrangement.

A piezoelectric device according to the present invention comprises a piezoelectric substrate, a strip-shaped thin plate portion used for thickness vibration, and a support portion provided at an end in the longitudinal direction of the thin plate portion and having a thickness greater than the thin plate portion. And one or more sets of excitation electrodes for performing the thickness vibration are formed on both surfaces of the thin plate portion. According to this configuration, since the supporting portion is attached to the end portion of the thin plate portion constituting the vibrating portion, even if the thin plate portion is made thin, the handleability does not decrease and a necessary vibration space is secured. In addition, when mounted on a circuit board, it can be stably fixed, and it is possible to prevent the conductive paste from flowing to the vibrating portion and hindering vibration. Further, since the distance between the extraction portions of both excitation electrodes can be increased, it is possible to prevent short-circuiting of both excitation electrodes during mounting. As described above, it is possible to provide a piezoelectric device that is compatible with high frequencies, suppresses unnecessary spurious emission, and has excellent handleability.

In the above structure, the thin plate portion may be formed by directly joining two piezoelectric substrates with their polarization axes reversed. As a result, a piezoelectric device having a resonance frequency twice as high as that obtained by using a single piezoelectric substrate having the same thickness can be obtained.

In the above structure, the support portion may be formed using the same piezoelectric substrate as the thin plate portion, or a substrate different from the thin plate portion may be directly joined to the thin plate portion. May be configured.

In the above structure, it is preferable that the excitation electrode is formed over the entire width of the thin plate portion. According to such a configuration, generation of unnecessary spurious can be further suppressed.

In the above configuration, the excitation electrode on at least one surface of the thin plate portion is divided into a plurality of portions.
You may comprise so that it may have a filter function. According to such a configuration, it is possible to provide an energy trapping type multi-mode piezoelectric filter that is compatible with high frequencies, suppresses unnecessary spurious emission, and has excellent handleability.

In the above structure, it is preferable that an inclined surface inclined in a substantially tapered shape is formed at a portion of the support portion connected to the thin plate portion. According to such a configuration, disconnection or the like can be prevented by extracting the excitation electrode through the inclined surface.

The above-described piezoelectric device can be used for a mobile communication device.

Further, in the method of manufacturing a piezoelectric device according to the first aspect of the present invention, a removing step is performed from at least one surface side of the piezoelectric substrate to form a thin plate portion and a thicker supporting portion. A step of providing one or more sets of excitation electrodes for causing the thin plate portion to vibrate in thickness, and cutting the piezoelectric substrate at a predetermined cut surface into individual pieces including the thin plate portion and the support portion. And a dividing step.

In the first manufacturing method described above, the thin plate portion can be formed by forming a groove in the piezoelectric substrate. Thereby, a thin plate part and a support part can be formed efficiently.

Further, according to a second aspect of the present invention, there is provided a method of manufacturing a piezoelectric device, comprising the steps of: directly joining a support substrate having a central portion opened to one surface of a piezoelectric substrate; And a step of cutting a joined body of the piezoelectric substrate and the support substrate at a predetermined cut surface and dividing the joined body into individual pieces including the piezoelectric substrate and the support substrate. Features.

Further, in the method of manufacturing a piezoelectric device according to the third configuration of the present invention, the step of forming a groove on one surface of the support substrate and the step of directly bonding the groove-formed surface of the support substrate to one surface of the piezoelectric substrate And the step of thinning the piezoelectric substrate with the support substrate side as a backing, and cutting a joined body of the piezoelectric substrate and the support substrate at a predetermined cut surface, and the piezoelectric substrate and the support substrate And a step of dividing into individual pieces including

According to the first to third manufacturing methods, the piezoelectric device of the present invention can be efficiently and easily manufactured.

In the above-described first to third manufacturing methods, a piezoelectric substrate obtained by directly joining two piezoelectric substrates with their polarization axes inverted to each other can be used as the piezoelectric substrate. According to such a configuration, a piezoelectric device having a resonance frequency twice as high as that obtained when a single piezoelectric substrate having the same thickness is used can be obtained.

The piezoelectric device obtained by the above manufacturing method can be used for a mobile communication device.

[0023]

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

FIG. 1 is a perspective view showing a structural example of the piezoelectric vibrator according to the first embodiment of the present invention. In the figure, 1 is a thin plate portion that performs thickness vibration, 2 is a support portion formed integrally with the thin plate portion, 3 is a piezoelectric substrate constituting the thin plate portion 1 and the support portion 2, and 4a is a surface of the thin plate portion 1. Excitation electrode provided, 4b
Is an excitation electrode provided on the back surface of the thin plate portion 1.

The piezoelectric substrate 3 uses an Xcut lithium tantalate substrate having a large coupling coefficient of sliding vibration, and the displacement direction of sliding vibration is taken in the left-right direction as shown by an arrow 10 in the drawing. The outer shape of the element is a thick tongue-shaped plate only in the support portion 2, and the overall planar shape is 2 mm × 0.3 mm.
The thickness of the supporting portion 2 is 300 μm, and the thickness of the thin plate portion 1 is 100 μm.

The excitation electrodes 4a and 4b are formed at predetermined positions of the thin plate portion 2 over the entire width of the element so as to face each other with the same size. In addition, the excitation electrodes 4a,
4b is drawn out to the end on the support portion 2 side of the element through the upper and lower surfaces of the support portion 2 by take-out lines each having a smaller width. In the present embodiment, the thickness of the thin plate portion 1 as the vibrating portion is 100 μm, and the resonance frequency is 20 μm.
MHz.

In the conventional piezoelectric vibrator, since the entire plate constituting the element has the same thickness, it is difficult to handle the thinned plate. In particular, in the case of a strip-shaped vibrator, there has been a problem that the width of the element becomes narrower in proportion to the thickness of the element, and the handling becomes more difficult.
However, according to the structure of the present invention, since the handling can be performed while holding the supporting portion 2 having a thick end portion, the workability is improved as compared with the case where the thin plate is handled alone. In addition, by setting the thickness of the thin plate portion 1 to a desired thickness, it is easy to increase the frequency of the element, and the production yield is improved. Further, since the excitation electrode is formed over the entire width of the element, spurious due to the width of the element and spurious due to reflection at the end face in the width direction can be minimized.

Hereinafter, a method for manufacturing the piezoelectric vibrator according to the present embodiment will be described with reference to FIGS.
FIG. 2 is a flowchart of a manufacturing process of the piezoelectric vibrator shown in the present embodiment, which is shown in a sectional view.

First, as shown in FIG.
The surface of the piezoelectric substrate 3 having a thickness of m is finished with good parallelism. With this thickness, the substrate can be easily handled, and can be handled in a large format.

Next, as shown in FIG. 2B, a groove having a depth of 200 μm is formed on the surface of the piezoelectric substrate 3 in order to form a groove (a groove in a direction perpendicular to the paper surface). This processing method can be performed by a mechanical processing method using a rotating grindstone 5 as shown in the figure. However, in order to obtain accuracy, the processing efficiency is low, but it is performed by plasma processing, electric discharge processing, laser processing, or chemical etching processing. You may. The portion whose thickness has been reduced by the groove processing becomes the thin plate portion 1 of the element, and the thick portions on both sides which have not been removed are the support portions 2 of the element.

Next, as shown in FIG. 2C, desired excitation electrode patterns 4a and 4b are formed on the front and back of the substrate. In order to form the excitation electrode patterns 4a and 4b, a metal mask having an electrode pattern-shaped opening can be used. At this time, in order to cover a step portion between the thin plate portion 1 and the support portion 2, it is preferable to use a sputtering method with high electrode wraparound, but it may be evaporation.

Finally, as shown in FIG. 2 (D), the sheet 1 is cut in a direction parallel to the direction of the formed groove (in a direction perpendicular to the plane of the paper) and in a direction perpendicular thereto, and the thin plate portion 1 and a support portion for its end are cut. 2 is completed, and the device as shown in FIG. 1 is completed.

According to the manufacturing method of the present embodiment, a large number of elements can be formed at a time, which facilitates mass production.
Moreover, the shape of the element finally obtained is a shape that can be handled without touching the thin plate portion 1, so that the thin plate portion 1 can be made thinner, and it is easy to increase the frequency. In addition, since there are a thick portion (support portion 2) and a thin portion (thin plate portion 1), the thick portion (support portion 2) can be stably fixed to a flat surface, and the vibration space of the thin plate portion 1 can be reliably secured. .

Further, since the electrode is taken out at the end face (support portion 2) of the element and has a level difference from the vibrating portion (thin plate portion 1), when the conductive paste is applied, the distance from the excitation electrode is reduced. It is easy to suppress the flow of the conductive paste into the vibrating portion and the occurrence of spots after application, thereby improving mass productivity and reducing characteristic variations.

(Embodiment 2) Another embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a perspective view showing a structural example of a piezoelectric vibrator according to a second embodiment of the present invention, and FIGS. 4A to 4D are views showing steps of manufacturing the piezoelectric vibrator shown in the present embodiment. It is a flowchart,
Shown in cross-section. 3 and 4, Embodiment 1
The same components as those described above are denoted by the same reference numerals.

The main differences between the present embodiment and the first embodiment are the following two points. First, two piezoelectric substrates 3,
3 'is that the polarization axes are inverted and the direct junctions are formed. Second, the thin plate portion 1 side of the support portion 2 has a tapered shape (tapered portion 2a). The point that the electrodes 4a and 4b are formed over the entire width of the element is the same as in the first embodiment, and the effect of suppressing spurious by this is the same.

As the piezoelectric substrate, two Xcut lithium tantalate substrates having a large coupling coefficient of sliding vibration are used, and these two substrates are directly joined with their polarization axes inverted. Japanese Patent Laid-Open No. 7-206 discloses a substrate having this configuration.
No. 600 is disclosed. By using a substrate having such a configuration, it is possible to excite a double-wave vibration that is not normally excited with a single substrate having the same thickness, and it is possible to double the resonance frequency. The external shape of the element is a rectangular shape of 1.5 mm × 0.15 mm square in the whole planar shape, the thickness of the piezoelectric substrate 3 ′ is 25 μm, and the thickness of the thin plate portion 1 of the piezoelectric substrate 3 is 25 μm (thin plate portion). The total thickness of 1 is 50
μm), and the thickness of the supporting portion 2 of the piezoelectric substrate 3 is 100 μm.
(The overall thickness of the support 2 is 125 μm).

Since the thin plate portion 1 (vibration plate) uses two piezoelectric substrates 3 and 3 'directly joined with the polarization axes inverted, the thickness of the thin plate portion 1 is 50 μm, which is half that of the first embodiment. However, the resonance frequency is four times that of the first embodiment, and the resonance frequency is about 80 MHz.

Further, since the excitation electrodes 4a and 4b are formed over the entire width of the element, spurious is suppressed.

Further, since the excitation electrode 4a formed on the surface of the thin plate portion 1 is drawn out to the support portion 2 through the tapered portion 2a, there is an advantage that disconnection hardly occurs as compared with the first embodiment.

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

As shown in FIG. 4A, two piezoelectric substrates 3 and 3 'are prepared, and their polarization axes are inverted and they are directly joined.

Next, as shown in FIG. 4B, one substrate 3 'is polished to a desired thickness (25 μm in this embodiment). At this time, when the thin plate portion 1 is formed, the thickness is set and processed so that the joint surface of the two substrates is located at exactly ち ょ う ど of the plate thickness. In the present embodiment, since the final thickness of the thin plate portion 1 is 50 μm, one of the substrates 3 ′ is thinned to 25 μm. Although it is difficult to obtain a plate having a thickness of 25 μm by itself, it is not broken because it is directly bonded to another thick substrate 3. After the thinning process, grooves (grooves in a direction perpendicular to the plane of the paper) are formed on the piezoelectric substrate 3 using the rotary grindstone 5. Unlike the first embodiment, the shape of the rotary grindstone 5 is set so that the outer peripheral surface forms a part of a conical surface so that the side surface of the groove can be formed into a tapered shape. Thus, a groove having a tapered side surface can be formed. At this time, the depth of the groove is reduced by 75 μm so that the entire thickness of the thin plate portion 1 becomes 50 μm for the reason described above.

Next, as shown in FIG. 4C, the excitation electrodes 4a, 4b are formed using a metal mask as in the first embodiment.
To form

Finally, as shown in FIG. 4 (D), the thin plate portion 1 and one end thereof were cut in a direction parallel to the formed groove (a direction perpendicular to the paper surface) and in a vertical direction. The device is divided into individual pieces having the support portion 2 and the device as shown in FIG. 3 is completed.

According to the manufacturing method of the present embodiment, a large number of elements can be formed at once, which facilitates mass production.
Moreover, the shape of the element finally obtained is a shape that can be handled without touching the thin plate portion 1, so that the thin plate portion 1 can be made thinner, and it is easy to increase the frequency. In addition, since there are a thick portion (support portion 2) and a thin portion (thin plate portion 1), the thick portion (support portion 2) is stably fixed to a flat surface, and the vibration space of the thin plate portion 1 can be reliably secured. .

Further, by using a substrate which is directly joined by inverting the polarization axes of the two piezoelectric substrates, the resonance frequency is 2 times higher than that of a vibrator using a single piezoelectric substrate of the same thickness for the vibrating portion. A twice as high piezoelectric vibrator can be formed.

Further, since the thin plate portion 1 side of the support portion 2 is inclined in a tapered shape, an element which is hardly broken can be obtained.

Further, since the electrode is taken out at the end face (support portion 2) of the element and has a level difference from the vibrating portion (thin plate portion 1), when the conductive paste is applied, the distance from the excitation electrode is reduced. It is easy to suppress the flow of the conductive paste into the vibrating portion and the occurrence of spots after application, thereby improving mass productivity and reducing characteristic variations.

In this embodiment, the electrodes 4a, 4b
Are taken out to the support portion 2 side, but the present invention is not limited to this. It is also possible to take out in the opposite direction. For example, if the electrode 4b on the substrate 3 'side is taken out to the support portion 2 side and the electrode 4a on the substrate 3 side is taken out on the side opposite to the support portion 2, the take-out on the substrate 3 side Since the wire does not need to pass through the step portion (taper portion) of the support portion 2, the risk of disconnection is further reduced. Also, since patterning of the electrodes on the flat surface can be performed by a normal photolithography process,
More accurate electrode formation becomes possible.

(Embodiment 3) Embodiment 3 of the present invention will be described with reference to FIGS.

FIGS. 5A to 5D are cross-sectional views showing the steps of manufacturing the piezoelectric vibrator of the present embodiment.
(D) is a top view thereof. FIGS. 5A to 5D correspond to FIGS. 6A to 6D, respectively. 5 and 6, the same components as those in the first and second embodiments are denoted by the same reference numerals.

Reference numeral 3 denotes a piezoelectric substrate used for thickness vibration, 6 denotes a supporting substrate different from the piezoelectric substrate 3, and 8 denotes an opening provided in the supporting substrate 6 in another processing step. The main difference between the present embodiment and the first and second embodiments is that the supporting substrate 6 forming the supporting portion 2 of the element is different from the piezoelectric substrate 3 forming the vibrating portion (thin plate portion 1). It is composed of

On the thin plate portion 1 side of the support portion 2, a tapered inclined surface 2a is formed as in the second embodiment. The vibrating portion (thin plate portion 1) is formed of a single-plate piezoelectric substrate 3 as in the first embodiment.

As the piezoelectric substrate 3, an Xcut lithium tantalate substrate is used. The support substrate 6 may be the same piezoelectric material as the piezoelectric substrate 3 or a different material.

The outer shape of the element is 2 mm ×
The thickness of the support portion 2 (the total thickness of the layer of the piezoelectric substrate 3 and the layer of the substrate 6) is 300 μm, and the thickness of the thin plate portion 1 is 100 μm. The resonance frequency is approximately 20 MHz as in the first embodiment.

The excitation electrodes 4a and 4b are formed at portions where thickness vibrations are excited by the excitation electrodes 4a and 4b, so that vibration is excited only at a portion where the excitation electrodes 4a and 4b overlap. Further, since the excitation electrode is formed over the entire width of the element, spurious is suppressed.

Further, the extraction portion of the excitation electrode 4b is not formed in the tapered portion 2a, and has a shape in which disconnection hardly occurs.

As shown in FIG. 5A and FIG.
The piezoelectric substrate 3 having a thickness of 00 μm is finished with good parallelism. The excitation electrode 4b is formed on one surface. Separately, a supporting substrate 6 having a thickness of 200 μm, an outer shape substantially the same as that of the piezoelectric substrate 3, and having a rectangular opening 8 in the center is prepared. At these thicknesses, these substrates 3 and 6 can be easily handled independently, and can be handled in a large format.

Next, as shown in FIGS. 5B and 6B, the piezoelectric substrate 3 and the support substrate 6 are directly bonded. The direct joining method is described in Japanese Patent Application Laid-Open No. 7-2066 described in the second embodiment.
It is the same as the method disclosed in Japanese Patent Publication No. 00. The support substrate 6 is joined to the surface of the piezoelectric substrate 1 on which the excitation electrodes 4b are formed, but the excitation electrodes 4b are not formed in the joining region.

Next, as shown in FIGS. 5C and 6C, the piezoelectric substrate 3 is thinned to a predetermined thickness with the support substrate 6 as a backing.

Finally, as shown in FIGS. 5D and 6D, a desired excitation electrode 4 a is formed on the surface of the piezoelectric substrate 3. Thereafter, the piezoelectric substrate 3 is cut along the cut surfaces 7a and 7b shown in FIG. 6D, and divided into pieces each having a shape in which a support substrate 6 is joined to one end of a thinned piezoelectric substrate 3, thereby completing a piezoelectric vibrator. .

In this embodiment, the excitation electrodes 4a, 4b
Can be formed on a perfect plane, so that there is an advantage that accurate electrodes can be formed using a photolithography process. Of course, an electrode can be formed using a metal mask.

According to the manufacturing method of the present embodiment, a large number of elements can be formed at once, which facilitates mass production.
Moreover, the shape of the element finally obtained is a shape that can be handled without touching the thin plate portion 1, so that the thin plate portion 1 can be made thinner, and it is easy to increase the frequency. In addition, since there are a thick portion (support portion 2) and a thin portion (thin plate portion 1), the thick portion (support portion 2) is stably fixed to a flat surface, and the vibration space of the thin plate portion 1 can be reliably secured. .

Further, since the electrode forming surfaces are all flat, patterning of the excitation electrode can be performed by a normal photolithography process, so that more accurate electrode formation can be performed.

(Embodiment 4) Embodiment 4 of the present invention will be described with reference to FIGS.

FIGS. 7A to 7D are cross-sectional views showing the steps of manufacturing the piezoelectric vibrator according to the present embodiment.
(D) is a top view thereof. FIGS. 7A to 7D correspond to FIGS. 8A to 8D, respectively. 7 and 8, the same components as those in the first to third embodiments are denoted by the same reference numerals.

The main difference between the present embodiment and the first to third embodiments lies in the method of forming the vibration space shape.

The electrode structure is almost the same as in the third embodiment. The vibrating portion (thin plate portion 1) is formed of a single-plate piezoelectric substrate 3 as in the first embodiment.

As the piezoelectric substrate 3, an Xcut lithium tantalate substrate is used.

As shown in FIGS. 7A and 8A, the piezoelectric substrate 3 is finished with good parallelism. The excitation electrode 4b is formed on one surface. Separately from this, a supporting substrate 6 having the same outer shape as the piezoelectric substrate 3 and having the grooves 9 formed in the same manner as in the first embodiment is prepared. Groove 9
Is to secure a vibration space for the vibrating part (thin plate part 1) of the element finally obtained.

Next, as shown in FIGS. 7B and 8B, the surface of the piezoelectric substrate 3 on which the excitation electrodes 4b are formed and the supporting substrate 6
Is directly bonded to the surface on which the groove 9 is formed. The method of direct joining is the same as in the third embodiment. As in the third embodiment, the excitation electrode 4b is not formed in the bonding region.

Next, as shown in FIGS. 7C and 8C, the piezoelectric substrate 3 is thinned to a predetermined thickness with the support substrate 6 as a backing.

Finally, as shown in FIGS. 7D and 8D, a desired excitation electrode 4 a is formed on the surface of the piezoelectric substrate 3. Thereafter, the piezoelectric substrate 3 is cut along the cut surfaces 7a and 7b shown in FIG. 8 (D), and is divided into pieces each having a shape in which the support substrate 6 constituting the support portion 2 is joined to one end of the thinned piezoelectric substrate 3, The piezoelectric vibrator is completed.

In this embodiment, the excitation electrodes 4a, 4b
Can be formed on a perfect plane, so that there is an advantage that accurate electrodes can be formed using a photolithography process. Of course, an electrode can be formed using a metal mask.

The piezoelectric element of the present embodiment has a U-shape as a whole because the supporting substrate 6 constituting the supporting portion 2 has an L-shaped cross-sectional shape. The stability is good even if it is placed.

According to the manufacturing method of the present embodiment, a large number of elements can be formed at once, which facilitates mass production.
Moreover, the shape of the element finally obtained is a shape that can be handled without touching the thin plate portion 1, so that the thin plate portion 1 can be made thinner, and it is easy to increase the frequency. In addition, since there are a thick portion (support portion 2) and a thin portion (thin plate portion 1), the thick portion (support portion 2) is stably fixed to a flat surface, and the vibration space of the thin plate portion 1 can be reliably secured. . In particular, when the device is placed horizontally, the effect is more remarkable.

Further, since the electrode forming surfaces are all flat, patterning of the excitation electrode can be performed by a normal photolithography process, so that more accurate electrode formation can be performed.

(Embodiment 5) Although the elements that can be formed by the embodiments described above are all oscillators, they can all be applied to a multimode filter.
An example in which the element shown in FIG. 1 is applied to a multi-mode filter will be described with reference to FIG.

FIG. 9 is a perspective view of the multimode filter of the present embodiment.

As shown in FIG. 9, the excitation electrode 4a on the surface of the thin plate portion 1 is divided into two to form a multi-mode filter. Further, the entire surface electrode 4b is formed on the back surface, and is drawn out to the end on the support portion 2 side.

The thickness vibration mode is coupled between the electrodes thus divided, and a multi-mode filter can be formed. Although the principle of the piezoelectric filter will not be described in detail here, the divided electrodes are arranged close to each other to form a filter, and similarly to the vibrator, suppression of spurious leads to stabilization of characteristics.

The manufacturing method is the same as that described in the first embodiment except that the electrodes are formed in a divided manner, and the details are omitted.

Similarly, the elements shown in the second to fourth embodiments can be applied to a multimode filter.

As shown in the present embodiment, the effect of the present invention is not limited to the piezoelectric vibrator, but can be similarly obtained with a multimode filter.

It is needless to say that a ladder-type filter in which a plurality of transducers are connected is also possible.

(Embodiment 6) Next, a method of mounting the above-described elements on a substrate will be described.

FIG. 10A shows an embodiment in which the element 10 a of the first and second embodiments is mounted on a substrate 20. FIG. 10B shows an element 10b according to the fourth embodiment.
Is mounted on a substrate 20. In the figure, 20
a is an opening formed in the substrate 20, 23a and 23b are conductive pastes connected to the excitation electrodes 4a and 4b, respectively.
Reference numeral 25 denotes an enclosure (package) for storing the element.

As can be seen from the figure, since the device of the present invention has a support portion thicker than the thin plate portion, the device is placed horizontally (the longitudinal direction of the thin plate portion 1 is parallel to the substrate 20 and the surface of the thin plate portion 1 is 20), the element can be stably fixed, and a vibration space can be easily secured.

The distance between the extraction portions of the electrodes is determined by the direction in which the electrodes are extracted. As shown in FIG.
When both electrodes are drawn out to the support portion 2 side, the distance between the electrode extraction portions can be increased by this thickness. As shown in FIG. 10B, when it is not possible to pull out in the same direction, it is also possible to pull out one electrode 4 b in the direction opposite to the support 2.
As described above, the direction in which the electrodes are led out can be selected in either case. In either case, the distance between the electrode lead portions can be made sufficiently large, and thus a short circuit between the two electrodes can be prevented.

In the conventional device, as shown in FIG. 11, when the surface of the piezoelectric substrate 11 is set in parallel with the fixed plane 15, the excitation electrodes on the upper and lower surfaces of the piezoelectric substrate 11 can be taken out without a short circuit. It was difficult. However, in the device of the present invention, when the device is placed on the substrate as shown in FIG. 10, the extraction portions of the excitation electrodes 4a and 4b are exposed on both sides of the device. , 23b).

The piezoelectric device of the present invention described above is not limited to the piezoelectric vibrator and the multi-mode piezoelectric filter as shown in the first to sixth embodiments, but is applicable to all the energy trapping piezoelectric devices. Widely applicable,
Similar effects can be obtained.

In addition, by using the piezoelectric filter having the above configuration in a wireless communication device such as a mobile phone, unnecessary spurious can be suppressed, and a high-frequency section can be constituted by a filter having excellent characteristics. It is possible to realize a wireless communication device having a high degree of influence and being hardly affected by an interference wave. In addition, by using the piezoelectric vibrator having the above configuration in an information device or a communication device, a clock can be generated by a vibrator having less spurious and stable characteristics, so that an information device or a communication device having a stable reference frequency and operation can be realized. .

Further, according to the present invention, unnecessary spurious components can be easily suppressed, and a piezoelectric device which is smaller and can handle high frequencies can be realized. Further, in the filter, an energy trap type piezoelectric device having excellent channel selectivity can be realized. Further, the manufacturing method is much easier than before.

In the first to sixth embodiments, lithium tantalate is used as the piezoelectric material. However, the present invention is not limited to this piezoelectric material, and other piezoelectric materials capable of forming an energy trap type multi-mode piezoelectric filter can be used. Can be used, and the same effect as above can be obtained. Also, there is no limitation on the cut angles of these materials. Although the vibration mode has mainly been described with respect to the slip vibration, the present invention can also be applied to a thickness longitudinal vibration and the like.

Further, in the manufacturing method shown in the above-described embodiment, the case where a plurality of elements can be obtained at one time has been described, but it is also possible to form them collectively on a large-sized substrate.

Further, the number of sets of excitation electrodes is shown as one set, but a plurality of sets may be connected.

Although the thin plate portion of the present invention is formed mainly by grinding, the present invention is not limited to this. For example, a method such as electric discharge machining, wet etching, laser machining, CVM, or dry etching may be used.

[0100]

As is apparent from the above description,
According to the present invention, it is possible to obtain an element in which spurious is suppressed at a higher frequency than in the related art.

According to the manufacturing method of the present invention, such an element can be manufactured efficiently and easily.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an energy trapping piezoelectric device according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing the piezoelectric device of FIG. 1;

FIG. 3 is a perspective view showing a schematic configuration of an energy trapping piezoelectric device according to a second embodiment of the present invention.

FIG. 4 is a process chart showing a method for manufacturing the piezoelectric device of FIG. 3;

FIG. 5 is a process chart showing a manufacturing method of the energy trapping piezoelectric device according to the third embodiment of the present invention in a sectional view.

FIG. 6 is a process diagram showing a method for manufacturing the energy trapping piezoelectric device according to the third embodiment of the present invention by a top view.

FIG. 7 is a process chart showing a manufacturing method of the energy trapping piezoelectric device according to the fourth embodiment of the present invention in a sectional view.

FIG. 8 is a process diagram showing a method for manufacturing the energy trapping piezoelectric device according to the fourth embodiment of the present invention by a top view.

FIG. 9 is a perspective view showing a schematic configuration of a multimode filter according to a fifth embodiment of the present invention.

FIG. 10 is a perspective view showing an example of a method for mounting the energy trapping piezoelectric device of the present invention.

11A and 11B are diagrams showing a schematic configuration of a conventional energy trap type piezoelectric vibrator, wherein FIG. 11A is a perspective view, FIG. 11B is a side view, and FIG. 11C is a perspective view of another configuration example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thin plate part 2 Support 2a Taper part (inclined surface) 3, 3 'Piezoelectric substrate 4a, 4b Excitation electrode 5 Grinding stone 6 Support substrate 7a, 7b Cut surface 8 Opening 9 Groove 10a, 10b Piezoelectric device 11 Piezoelectric substrate 12 Excitation electrode 13 Conductive paste 14 Vibration space 15 Fixed plane 20 Substrate 20a Openings 23a, 23b Conductive paste 25 Enclosure (package)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiro Tomita 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 5J108 AA01 AA07 BB01 CC04 CC11 CC13 DD01 DD07 EE03 EE07 EE13 FF02 KK01 MM08 MM11

Claims (13)

[Claims] 1. A thin plate portion comprising a piezoelectric substrate, comprising a strip-shaped thin plate portion used for thickness vibration, and a support portion provided at an end in a longitudinal direction of the thin plate portion and having a thickness greater than the thin plate portion. A piezoelectric device, wherein one or more sets of excitation electrodes for causing the thickness vibration are formed on both surfaces of the piezoelectric device. 2. The piezoelectric device according to claim 1, wherein the thin plate portion is formed by directly joining two piezoelectric substrates with their polarization axes reversed. 3. The support portion is formed by directly bonding a substrate different from the thin plate portion to the thin plate portion.
6. The piezoelectric device according to claim 1. 4. The piezoelectric device according to claim 1, wherein the excitation electrode is formed over the entire width of the thin plate portion. 5. The piezoelectric device according to claim 1, wherein the excitation electrode on at least one surface of the thin plate portion is divided into a plurality of portions and has a filter function. 6. An inclined surface which is inclined in a substantially tapered shape at a portion of said support portion connected to said thin plate portion.
6. The piezoelectric device according to claim 1. 7. A mobile communication device using the piezoelectric device according to claim 1. Description: 8. A set of a step of performing a removing process from at least one surface side of the piezoelectric substrate to form a thin plate portion and a thicker supporting portion, and an excitation electrode for causing the thin plate portion to perform thickness vibration. Or a step of providing a plurality of sets, and a step of cutting the piezoelectric substrate along a predetermined cut surface to divide the piezoelectric substrate into pieces each having the thin plate portion and the support portion. Method. 9. The method according to claim 8, wherein the thin plate portion is formed by forming a groove in the piezoelectric substrate. 10. A step of directly bonding a support substrate having a central portion opened to one surface of a piezoelectric substrate, a step of thinning the piezoelectric substrate with the support substrate side as a backing, Cutting the joined body at a predetermined cut surface and dividing the joined body into individual pieces including the piezoelectric substrate and the support substrate. 11. A step of forming a groove on one surface of a support substrate, a step of directly bonding the groove-formed surface of the support substrate to one surface of a piezoelectric substrate, and a step of thinning the piezoelectric substrate with the support substrate side as a backing. And cutting the joined body of the piezoelectric substrate and the support substrate along a predetermined cut surface, and dividing the joined body into individual pieces including the piezoelectric substrate and the support substrate. Of manufacturing a piezoelectric device. 12. The method for manufacturing a piezoelectric device according to claim 8, wherein the piezoelectric substrate is obtained by directly joining two piezoelectric substrates with their polarization axes reversed. 13. A mobile communication device using a piezoelectric device manufactured by the method for manufacturing a piezoelectric device according to claim 8. Description: