JP2002299999A - Surface acoustic wave filter and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave(SAW) filter, with which band suppression characteristics are satisfactory, and a production method, with which such characteristics (especially band suppression characteristics) can be controlled. SOLUTION: In a SAW filter S1, a SAW element, with which an exciting electrode 2 of SAW is formed on one principal side of a piezoelectric substrate 1, is housed in a casing 8 having an opening while turning one principal side of the piezoelectric substrate 1 downward, and the upper surface of the opening of the casing 8 is air-tightly sealed by a lid body 11. On the other principal side of the piezoelectric substrate 1, a dielectric layer 13 and a conductor layer 3 are successively laminated at least and at least one part of the lid body is formed from a translucent member 11a capable of irradiating the conductor layer 3 with light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface acoustic wave filter, and more particularly to a surface acoustic wave filter having excellent band suppression characteristics in a high frequency band including a GHz band, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, surface acoustic wave filters have been used in various communication devices, which play a role in downsizing the devices and adjusting the pass band frequency. With the development of higher frequency and higher functionality of communication devices, there is an increasing demand for filters having variations in bandwidth and attenuation.

For example, a filter for a 900 MHz band mobile phone has an effective pass bandwidth of 25 MHz (fractional bandwidth of 2.8).
%), A 2 GHz band filter for mobile phones requires a low insertion loss band pass filter having an effective pass bandwidth of 75 MHz (fractional bandwidth of 4.1%). this is,
This is because a filter for a mobile phone is used for filtering a weak signal of an antenna, so that the signal / noise ratio must be large, that is, the loss must be low. On the other hand, it is essential that the filter function also satisfies the blocking performance required by the communication standard, but the above-mentioned band-suppression characteristics satisfying the low-loss performance and the blocking characteristics are in a trade-off relationship with each other. Yes, it is very difficult to balance them. In such a case, a method that gives priority to low loss in the filter structure and obtains the band suppression characteristic by using a filter peripheral circuit is an optimal method for realizing the request.

FIGS. 5 and 6 show examples of the structure of a conventional surface acoustic wave filter. FIG. 5 is a sectional view taken along line BB ′ in FIG. 6 shown in a plan perspective view.

As shown in FIGS. 5 and 6, in a surface acoustic wave filter J in which a surface acoustic wave element is accommodated in a casing 8, an excitation surface for exciting a surface acoustic wave is applied to the main surface of the piezoelectric substrate 1. An electrode 2 is formed. On the element-side extraction electrode 4 connected to the excitation electrode 2, a bump electrode 5 having a partially thickened electrode is mounted, and has both an electrical connection and a mechanical holding function on the bump electrode 5. The bump 6 is formed. On the excitation electrode 2, a protective film 12 is laminated for protecting the electrode against foreign matter.

The bumps 6 are electrically and mechanically bonded between the element-side lead-out electrodes 4 and the housing-side inner lead-out electrodes 7 by using a thermosonic bonding technique. The electrode 2 has an excitation space. A lid 11 is placed on the upper surface of the opening of the housing 8 to form an airtight structure.

In this conventional surface acoustic wave filter J, it is generated by the interaction between the internal extraction electrode 7 on the filter housing side and the external extraction electrode 9 on the housing side and the excitation electrode 2 of the surface acoustic wave formed on the piezoelectric substrate 1. Stray electric characteristics (capacitance) have been taken in by design as peripheral circuits using lumped and distributed constants. By adjusting the circuit structure and the circuit constant in design, the frequency at which the attenuation pole is generated has been adjusted, and the band suppression characteristics have been improved. However, only the stray electrical characteristics generated by the interaction of the excitation electrode 2 and the like described above lacks the capacitance that can be used to adjust the frequency of the attenuation pole, and the band suppression characteristics can be designed at the target frequency. It was difficult.

Further, even in the filter designed in this way, the excitation electrode 2 may be displaced due to the mounting displacement of the piezoelectric substrate 1 of the surface acoustic wave filter occurring during the manufacturing process or the manufacturing variation of the height of the bump 6. The floating electric characteristics generated by such an interaction fluctuate, deteriorating the band suppression characteristics. However, there has been no effective correction method to prevent this deterioration in the manufacturing process.

In view of such a situation, an object of the present invention is to provide a surface acoustic wave filter having good band suppression characteristics and a manufacturing method capable of adjusting the band suppression characteristics.

[0010]

In order to achieve the above object, a surface acoustic wave filter according to the present invention includes a surface acoustic wave element having a surface acoustic wave excitation electrode formed on one principal surface of a piezoelectric substrate. A surface acoustic wave filter in which a piezoelectric substrate is accommodated in a housing having an opening with one main surface side down, and an upper surface of the opening of the housing is hermetically sealed with a lid. At least a conductor layer is provided on the other main surface, and at least a part of the lid is formed of a translucent member capable of irradiating the conductor layer with light. Here, according to the configuration in which a dielectric layer and a conductor layer are sequentially laminated on the other main surface of the piezoelectric substrate, a filter including a peripheral circuit is provided by providing a dielectric layer for adding capacitance to the entire filter. When designing the characteristics, the degree of freedom in setting the frequency of the band suppression characteristics is increased, which is advantageous.

Further, in the method of manufacturing a surface acoustic wave filter according to the present invention, the surface acoustic wave element is housed in the housing,
Adjusting the filter characteristics by sealing the upper surface of the opening of the housing with a lid, and removing a predetermined region of the conductor layer by light energy transmitted through the translucent member of the lid. And a step.

Thus, the excitation electrode, the piezoelectric substrate,
By generating an appropriate capacitance between each of the (dielectric layer) and the conductor layer, the band suppression characteristics can be suitably adjusted. In addition, the adjustment at this time is extremely easy by sealing the upper surface of the opening of the housing with a lid and then removing the conductor layer by irradiating a laser beam transmitted through the translucent member of the lid. It is possible to realize it.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a surface acoustic wave filter according to the present invention will now be described in detail with reference to the drawings. The same members as already described are denoted by the same reference numerals, and description thereof will be omitted. FIGS. 1, 2 and 3 show the lid 11
FIG. 5 is a cross-sectional view taken along line AA ′ in FIG.

As shown in FIGS. 1 and 4, the piezoelectric substrate 1 is, for example, a lithium niobate single crystal having a Y-cut X-propagation of 38 to 44 degrees, or a Y-cut X 61-67 degrees.
Using a propagating lithium niobate single crystal, the piezoelectric substrate 1
An excitation electrode 2 for exciting surface acoustic waves is provided on one principal surface of
On the uppermost layer on the other main surface side of the piezoelectric substrate 1, a conductor layer 3 for adjusting band suppression characteristics is provided to constitute a surface acoustic wave element.
On the other main surface side of the piezoelectric substrate 1, at least a dielectric layer 13 which is a dielectric substrate for adding capacitance and a conductor layer 3 for adjusting band suppression characteristics are sequentially laminated. Then, such a surface acoustic wave element is housed in a housing 8 having an opening with one principal surface side of the piezoelectric substrate 1 facing down, and at least a part of the upper surface of the opening of the housing 8 is connected to the conductor layer 3. A surface acoustic wave filter S <b> 1 is hermetically sealed with a lid 11 formed of a light-transmittable translucent member.

Here, the main surfaces of the piezoelectric substrate 1 and the dielectric layer 13 are mirror-finished (arithmetic average roughness of about 6 nm or less), aligned, and then heated. Both are in close contact. In this joining, an adhesive layer 15 using an adhesive may be interposed as shown in the figure,
Since it is conceivable that the whole dielectric constant decreases, and particularly the capacitance between the excitation electrode 2 and the conductor layer 3 decreases, the former joining method is more preferably employed.

The excitation electrode 2 is formed on one main surface of the piezoelectric substrate 1 by A
l, Al alloy, or a multilayer film containing Al is formed by a thin film forming method such as sputtering or EB (Electron Beam) vapor deposition, and is manufactured using a process such as photolithography to form a surface acoustic wave device. .

This surface acoustic wave element is formed by combining a plurality of pairs of excitation electrodes on both ends of a surface acoustic wave propagation axis with a plurality of reflection electrodes mounted thereon in a ladder type. Ladder type circuit, lattice type circuit combining surface acoustic wave resonators in a lattice type, or resonator type circuit combining multiple pairs of excitation electrodes on the surface wave propagation axis. Yes, the operating frequency is in the 800 MHz to 5 GHz band.

Composite substrate 14 constituting surface acoustic wave device
Is obtained by cutting into a chip size using a wafer having a total thickness of the piezoelectric substrate 1 and the dielectric layer 13 as a dielectric substrate of 0.10 to 0.35 mm. In particular, the thickness of the piezoelectric substrate 1 is set to 0.10 to 0.25 mm,
Was set to 0.10 to 0.25 mm, and the both were combined. The reason for the total thickness is 0.1
If the thickness is less than 0 mm, the number of defective defects during the wafer process increases, and
For a thickness of 35 mm or more, the conductor layer 3 and the excitation electrode 2 described later
Also, since the capacitance between the element-side extraction electrodes 4 decreases, the frequency of the band suppression characteristic (attenuation pole) cannot be sufficiently controlled.

Further, in order to secure the bump adhesion strength at the time of flip chip mounting, the thickness of the bump electrode 5 is set to about 1 μm.
m or more.

Next, a conductor layer 3 is formed on the other main surface of the piezoelectric substrate 1 on which the excitation electrode 2 is not provided. It is desirable that the conductor layer 3 has a small film stress and a low resistance in order to avoid a factor of frequency fluctuation. Therefore, a conductive metal film is preferable, and specifically, Al, Al alloy, C
u, Ni, Au or the like is preferable. Further, the thickness is set to 50 nm to 600 nm. The reason for this is that when the thickness is 50 nm or less, the conductivity of the conductor layer is deteriorated, and a sufficient Q of the capacitance cannot be obtained, so that the band suppression level of the attenuation pole is deteriorated. In the case of a conductor layer having a thickness of 600 nm or more, deterioration of characteristics does not occur, but the possibility that a conductor sublimated by irradiation with laser light may contaminate the inside of the housing increases.

Then, a ball made of Au is thermally and ultrasonically pressed onto the bump electrode 5 to form a bump 6. Thereafter, the surface acoustic wave element is inserted into the case 8 so as to face the cavity side of the case 8 made of ceramics, and the bump 6 bonded to the bump electrode 5 on the element side and the cavity of the case 8 are formed. Thermo-ultrasonic bonding is performed so that the housing-side internal extraction electrode 7 arranged inside is electrically connected.

Thus, the conductor layer 3, the excitation electrode 2,
The band suppression characteristic (attenuation pole) generated in the attenuation characteristic of the surface acoustic wave filter is effectively used by the capacitance generated between the element-side extraction electrode 4 (or the housing-side internal extraction electrode 7 provided in the housing 8). However, desired attenuation characteristics can be realized.

Next, a sealing member 10 such as a silver contacting low is provided on the upper surface of the opening of the housing 8 by a lid 11 at least a part of which is formed of a translucent member capable of irradiating the conductor layer 3 with light. Or a sealing material 10 such as an epoxy resin adhesive, frit glass, or solder.
And hermetically sealed. It is desirable that the translucent member be made of a glass material containing Si as a main component and having as high a transmittance as possible.
Other optical crystal materials have no problem in terms of transmittance,
When forming a lid composite with a metal material made of Fe, Cu, Ni, or an alloy thereof, in a glass material containing Si as a main component, the linear expansion coefficient is approximated by adding impurities to improve reliability. This is desirable because it is possible to configure a highly reliable component.

The surface acoustic wave device mounted in the housing 8 hermetically sealed by the lid 11 is measured by using a network analyzer or the like, and is irradiated with laser light.
By reducing the area of the conductor layer 3 of the surface acoustic wave element,
The attenuation pole can be guided to any frequency.

As described above, according to the manufacturing method of the present invention, the housing 8
A step of housing the surface acoustic wave element therein and hermetically sealing the upper surface of the opening of the housing 8 with the lid 11, and forming the conductive layer 3 with light energy transmitted through the translucent member 11 a of the lid 11. Adjusting a filter characteristic by removing a predetermined area.

Here, a YAG laser or a carbon dioxide laser is used for laser light irradiation. Preferably YA
A G laser is used. The reason is that the output intensity is suitable for sublimating a metal having a melting point of 500 to 800 degrees or less.

As the above-described trimming method using a laser beam, a method of combining a short pulse shot and a laser scan in an area necessary for removing the conductor layer 3 and a method of expanding a laser beam area and shot in a large area However, a method of finely adjusting the area of the conductor layer 3 by the former method is preferable. The reason is that long-time laser irradiation adversely affects the surface acoustic wave piezoelectric substrate material having a large frequency temperature coefficient, making it difficult to accurately read the filter frequency. It is also effective to start the removal from the central portion of the conductor layer 3 where the capacitance changes greatly by scanning, and to remove the peripheral portion of the conductor layer 3 at the time of fine adjustment. In addition, since the frequency of the attenuation pole can be adjusted in the atmosphere by using laser light, it is suitable for adjusting the filter characteristics while performing measurement and evaluation in the final manufacturing process.

Thus, according to the manufacturing method including the configuration of the surface acoustic wave filter S1 and the method of adjusting the characteristics thereof, both the pass band characteristics and the band suppression characteristics of the surface acoustic wave filter are well designed, and the characteristics are determined in the final step. By performing the adjustment, a high quality surface acoustic wave filter can be provided with high yield.

Next, the surface acoustic wave filter S2 shown in FIGS. 2 and 4 will be described.

A surface acoustic wave element having the same operating frequency as the surface acoustic wave filter S1 shown in FIG. 1 and having the same operating frequency is manufactured. However, the surface acoustic wave filter S2 can be easily manufactured and has a surface acoustic wave S1. Only the conductor layer 3 for adjusting the band-suppressing characteristic is provided on the other main surface side (upper surface side) of the piezoelectric substrate 1 having a high dielectric constant such as a lithium tantalate single crystal so as to obtain a high capacitance equivalent to that of FIG. ing.

With this configuration, the band suppression characteristic (attenuation pole) generated in the attenuation characteristic of the surface acoustic wave filter is effectively used,
Desired attenuation characteristics can be realized. The reason is that a material having a high dielectric constant such as lithium tantalate single crystal is used for the piezoelectric substrate material, so that the conductor layer 3 is formed on the other main surface side of the piezoelectric substrate 1.
Even with a structure provided with only one, a necessary and sufficient capacitance can be generated.

The conductor layer 3 desirably has a small film stress and a low resistance in order to avoid a factor of frequency fluctuation. Therefore, a conductive metal film is preferable, and specifically, Al, an Al alloy, Cu, Ni, Au, or the like is preferable. Further, the thickness is set to 50 nm to 600 nm. The reason for this is that when the thickness is 50 nm or less, the conductivity of the conductor layer is deteriorated, and a sufficient Q of the capacitance cannot be obtained, so that the band suppression level of the attenuation pole is deteriorated. Also, 600n
In the case of a conductor layer having a length of m or more, the characteristics do not deteriorate, but the possibility that the conductor sublimated by the irradiation of the laser light will contaminate the inside of the housing increases.

Thus, also with this surface acoustic wave filter S2, the conductive layer 3, the excitation electrode 2, and the element-side extraction electrode 4 (or the housing-side internal extraction electrode 7 provided on the housing 8).
A desired attenuation characteristic can be realized by effectively utilizing a band suppression characteristic (attenuation pole) generated in the attenuation characteristic of the surface acoustic wave filter due to the capacitance generated during the period.

Further, since the capacitance can be easily obtained more than the surface acoustic wave filter S1, the effect of the dielectric loss is reduced, and the operation and effect of the high attenuation characteristic can be expected.

Further, similarly to the surface acoustic wave filter S1, a predetermined region is removed from the conductor layer 3 by irradiating a laser beam, so that the band suppression characteristics can be easily adjusted.

Next, the surface acoustic wave filter S3 shown in FIGS. 3 and 4 will be described.

A surface acoustic wave element having the same operating frequency as the surface acoustic wave filter S1 shown in FIG. 1 and having the same operating frequency is manufactured. In the surface acoustic wave filter S3, the cover 11 is made of a composite material. In addition, since the entire lid 11 is formed of a translucent member capable of irradiating the conductor layer 3 with light, there is an advantage that the lid 11 can be manufactured very easily. Note that other configurations and manufacturing methods are the same as those of the surface acoustic wave filter S1, and a description thereof will be omitted.

Thus, the surface acoustic wave filter S3 also provides the conductive layer 3, the excitation electrode 2, and the element-side extraction electrode 4 (or the housing-side internal extraction electrode 7 provided on the housing 8).
A desired attenuation characteristic can be realized by effectively utilizing a band suppression characteristic (attenuation pole) generated in the attenuation characteristic of the surface acoustic wave filter due to the capacitance generated during the period.

Further, since the capacitance can be easily obtained more than the surface acoustic wave filter S1, the effect of the dielectric loss is reduced, and the operation and effect of the high attenuation characteristic can be expected.

Further, similarly to the surface acoustic wave filter S1, a predetermined region is removed from the conductor layer 3 by irradiating a laser beam, so that the band suppression characteristics can be easily adjusted.

In the present embodiment, a single crystal of lithium niobate and a single crystal of lithium tantalate are described as an example of the piezoelectric substrate and the dielectric layer. However, for example, a single crystal of lithium tetraborate or a single crystal having a langasite type crystal structure is used. Crystals and the like can also be used, and can be appropriately modified and implemented without departing from the gist of the present invention.

[0042]

EXAMPLE 1 Next, a description will be given of a surface acoustic wave filter having a ladder-type circuit configuration specifically manufactured according to the basic structure of the surface acoustic wave filter shown in FIG.

Thickness of 64 degree rotation Y cut X propagation 0.15
The piezoelectric substrate 1 made of lithium niobate (mm) and the dielectric layer 13 made of a single crystal of lithium tantalate having a thickness of 0.20 mm and a thickness of 0.20 mm for 36-rotation Y-cut X propagation have mirror-finished principal surfaces, respectively. Surface bonding was performed on an optical platen with the flat surface as a reference. After the joining, heating was performed in a reducing atmosphere to increase the degree of adhesion of the joining surfaces.

The composite substrate 14 thus manufactured
The excitation electrode 2 was formed on a main surface made of a 4 degree Y-cut X-propagation lithium niobate single crystal. The manufactured filter is
This is a surface acoustic wave filter for reception having a relative bandwidth of about 4.0% in a 900 MHz band, and an excitation electrode width and an electrode space (a space between electrode fingers) are each set to about 1 μm.

The configuration of the filter is a 2.5-stage π-ladder type surface acoustic wave filter using five surface acoustic wave resonators provided with the surface acoustic wave excitation electrodes 2. The wave resonator has a large capacitance ratio between the series side and the parallel side in order to obtain a low loss and a high attenuation outside the band.

The configuration of the surface acoustic wave resonator is such that the number of excitation electrodes 2 is about 60 on the series side and about 100 on the parallel side. Assuming that the average wavelength of the surface acoustic wave resonator is λ, the intersection width is 15λ in series and 30λ in parallel. As a material of the electrode, an Al-Cu 1% by weight alloy film having a thickness of about 300 nm formed by a sputtering method was used. Here, the reason why the sputtering method is used is that the metal composition ratio of the aluminum alloy film used as the electrode material is not changed. In other methods such as the EB vapor deposition method, the metal composition ratio of the Al—Cu alloy film is proportional to the vapor pressure curve of Al or Cu during vapor deposition. Cause.

Thereafter, a protective film 12 made of SiO2 was formed to a thickness of 30 nm on the surface of the substrate on which the surface acoustic wave excitation electrode 2 was mounted by using the CVD method. Here, the reason why the CVD method is used is a result in consideration of the covering property of the SiO2 film on the side surface of the excitation electrode.

In order to form the Au bump 6 on the bump electrode 5, it is necessary to selectively remove the protective film 12 from the bump electrode 5 and form only the bump electrode 5 into a multilayer film. For this reason, a photoresist is re-applied on the wafer, and only the bump electrode portion is selectively exposed by using a photolithography method, and then the bump electrode is formed by using an RIE (reactive ion etching) apparatus. 5 was removed. The reactive gas used in the etching was selected mainly from CF4 and O2 gases. Since RIE has strong direction selectivity, it is possible to expose a bump electrode according to the photoresist dimensions obtained in the photolithography process. Further, an aluminum film was formed on the photoresist by about 1 μm using an EB evaporation method.
The electrode material was able to be laminated only on the bump electrode 5 by removing unnecessary aluminum electrodes other than the bump electrode using the lift-off method.

Using a bump bonder, an Au bump having a bump diameter of about 90 μm and a height of about 60 μm was formed on the bump electrode 5.

The wafer was divided using a dicing saw at a pitch of about 1 mm square using diamond abrasive # 600. This condition was selected under the condition that the chipping dimension generated during dicing is suppressed to about 20 μm.

The surface acoustic wave element is formed by making the cavity of the casing 8 and the excitation electrode 2 face each other, and joining the extraction electrode 7 in the casing and the Au bump 6 formed on the bump electrode 5 by thermosonic bonding. The wave excitation electrode 2 and the housing external electrode 9 were electrically joined.

The lid 11 was formed by processing a Kovar flat plate having a thickness of 100 μm by press working, applying a Ni plating process, and then fitting a light-transmitting window at the center. As the translucent material, Kovar glass having a thickness of 200 μm was bonded to Kovar using an airtight resin. The hermetic joining between the lid 11 and the package housing 8 was performed by seam welding.

For adjusting the frequency of the attenuation pole of the surface acoustic wave filter, a YAG laser was used. The laser used converged the spot system of the laser trimmer to a diameter of about 0.05 mm, and repeated shots with short pulses to adjust the degree of influence. The frequency of the attenuation pole was adjusted using a laser shot in parallel with the measurement by a network analyzer (Hewlett-Packard: model number HP8753ES).

For measuring the electrical characteristics of the surface acoustic wave element,
Using the above network analyzer, 9
Good electrical characteristics could be confirmed at 00 MHz. <Example 2> Next, a ladder type surface acoustic wave filter specifically manufactured according to the basic structure of the surface acoustic wave filter S2 shown in FIG. 2 will be described.

An excitation electrode 2 was formed on a piezoelectric substrate 1 made of lithium tantalate single crystal that was rotated by 36 degrees and cut by Y-cut X propagation. The produced filter was 900 MH as in FIG.
This is a surface acoustic wave filter for reception having a specific bandwidth of about 4.0% in the z band, and an excitation electrode width and an electrode space of about 1% each.
μm. The lithium tantalate single crystal substrate used had a diameter of 3 inches and a thickness of 0.25 mm.

The configuration of the filter is a 2.5-stage π-type ladder-type surface acoustic wave filter using five surface acoustic wave resonators provided with the excitation electrodes 2. The configuration of each surface acoustic wave resonator is as follows. In order to obtain low loss and high out-of-band attenuation, the capacitance ratio between the series side and the parallel side is set large.

The configuration of the surface acoustic wave resonator is such that the number of excitation electrodes 2 is about 60 on the series side and about 100 on the parallel side. Assuming that the average wavelength of the surface acoustic wave resonator is λ, the intersection width is 15λ in series and 30λ in parallel. As a material of the electrode, an Al-Cu 1% by weight alloy film having a thickness of about 400 nm formed by a sputtering method was used.

Thereafter, a protective film 12 of SiO2 was formed to a thickness of 30 nm on the substrate on the surface on which the excitation electrode 2 was mounted by using the CVD method.

In order to form the Au bumps 6 on the bump electrodes 5, it is necessary to selectively remove the protective film 12 from the bump electrodes and to make only the bump electrode portions into a multilayer film.
For this reason, a photoresist was re-applied on the wafer and only the bump electrode portions were selectively exposed using the photolithography method, and then the SiO2 layer on the bump electrode portions 4 was removed using an RIE apparatus. . The reactive gas used at the time of etching was selected mainly from CF4 and O2 gases. Since RIE has a strong direction selectivity, the bump electrodes can be exposed to the dimensions of the photoresist obtained in the photolithography process. Further, an aluminum film is laminated on the photoresist by about 1 μm by EB vapor deposition method, and unnecessary aluminum electrodes other than the bump electrode part are removed by lift-off method, so that the electrode can be laminated only on the bump electrode part. Was.

Using a bump bonder, an Au bump having a diameter of about 90 μm and a height of about 60 μm was formed on the bump electrode.

The wafer was divided using a dicing saw at a pitch of about 1 mm square using diamond abrasive grains # 600. This condition was selected under the condition that the chipping dimension generated during dicing is suppressed to about 20 μm.

The surface acoustic wave element is arranged such that the cavity of the housing 8 and the surface acoustic wave excitation electrode 2 face each other,
The surface acoustic wave excitation electrode 2 and the housing external electrode 9 were electrically joined by thermosonic bonding of the Au bump 6 formed on the bump electrode 5 and the Au bump 6.

The cover 11 was formed by pressing a Kovar flat plate having a thickness of 100 μm to form an outer shape by press working, and performing a Ni plating process, and then fitting a translucent window at the center. As the translucent material, Kovar glass having a thickness of 200 μm was bonded to Kovar using an airtight resin. The hermetic joining between the lid 11 and the package housing 8 was performed by seam welding.

For adjusting the frequency of the attenuation pole of the surface acoustic wave filter, a YAG laser was used. The laser used converged the spot system of the laser trimmer to a diameter of about 0.05 mm, and repeated shots with short pulses to adjust the degree of influence. The frequency adjustment of the attenuation pole was performed using a laser shot in parallel with the measurement by the network analyzer as in Example 1.

Also in this example, a network analyzer was used for measuring the electrical characteristics of the surface acoustic wave element, as in Example 1, and as a result, good electrical characteristics were confirmed at 900 MHz. Example 3 Next, a ladder-type surface acoustic wave filter specifically manufactured according to the basic structure of the surface acoustic wave filter S3 shown in FIG. 3 will be described.

Thickness of 64 degree rotation Y cut X propagation 0.15
The piezoelectric substrate 1 made of lithium niobate (mm) and the dielectric layer 13 made of a single crystal of lithium tantalate having a thickness of 0.20 mm and a thickness of 0.20 mm for 36-rotation Y-cut X propagation have mirror-finished principal surfaces, respectively. Surface bonding was performed on an optical platen with the flat surface as a reference. After the joining, heating was performed in a reducing atmosphere to increase the degree of adhesion of the joining surfaces.

The composite substrate 14 manufactured as described above
The excitation electrode 2 was formed on a main surface made of a 4 degree Y-cut X-propagation lithium niobate single crystal. The manufactured filter is
This is a surface acoustic wave filter for reception having a relative bandwidth of about 4.0% in a 900 MHz band, and an excitation electrode width and an electrode space (a space between electrode fingers) are each set to about 1 μm.

The configuration of the filter is a 2.5-stage π-ladder type surface acoustic wave filter using five surface acoustic wave resonators provided with the surface acoustic wave excitation electrodes 2. The wave resonator has a large capacitance ratio between the series side and the parallel side in order to obtain a low loss and a high attenuation outside the band.

The configuration of the surface acoustic wave resonator is such that the number of excitation electrodes 2 is about 60 on the series side and about 100 on the parallel side. Assuming that the average wavelength of the surface acoustic wave resonator is λ, the intersection width is 15λ in series and 30λ in parallel. As a material of the electrode, an Al-Cu 1% by weight alloy film having a thickness of about 400 nm formed by a sputtering method was used.

Thereafter, a protective film 12 of SiO2 was formed to a thickness of 30 nm on the surface of the substrate on which the excitation electrode 2 was mounted by using the CVD method.

In order to form the Au bump 6 on the bump electrode 5, it is necessary to selectively remove the protective film 12 from the bump electrode and to form only the bump electrode portion into a multilayer film.
For this reason, a photoresist was re-applied on the wafer and only the bump electrode portions were selectively exposed using the photolithography method, and then the SiO2 layer on the bump electrode portions 4 was removed using an RIE apparatus. . The reactive gas used at the time of etching was selected mainly from CF4 and O2 gases. Since RIE has a strong direction selectivity, the bump electrodes can be exposed to the dimensions of the photoresist obtained in the photolithography process. Further, an aluminum film is laminated on the photoresist by about 1 μm by EB vapor deposition method, and unnecessary aluminum electrodes other than the bump electrode part are removed by lift-off method, so that the electrode can be laminated only on the bump electrode part. Was.

Using a bump bonder, an Au bump having a diameter of about 90 μm and a height of about 60 μm was formed on the bump electrode.

The wafer was divided using a dicing saw at a pitch of about 1 mm square using diamond abrasive # 600. This condition was selected under the condition that the chipping dimension generated during dicing is suppressed to about 20 μm.

The surface acoustic wave element is arranged such that the cavity of the housing 8 and the surface acoustic wave exciting electrode 2 face each other,
The surface acoustic wave excitation electrode 2 and the housing external electrode 9 were electrically joined by thermosonic bonding of the Au bump 6 formed on the bump electrode 5 and the Au bump 6.

The lid 11 was formed by processing a glass single plate having a thickness of 200 μm so as to match the opening on the upper surface of the housing 8. The hermetic joining between the housing 8 and the lid 11 used a resin adhesive for hermetic joining.

For adjusting the frequency of the attenuation pole of the surface acoustic wave filter, a YAG laser was used. The laser used converged the spot system of the laser trimmer to a diameter of about 0.05 mm, and repeated shots with short pulses to adjust the degree of influence. The frequency adjustment of the attenuation pole was performed using a laser shot in parallel with the measurement by the network analyzer as in Example 1.

Also in this example, a network analyzer was used to measure the electrical characteristics of the surface acoustic wave device, as in Example 1, and as a result, good electrical characteristics were confirmed at 900 MHz.

[0078]

According to the surface acoustic wave filter and the method of manufacturing the same of the present invention, the excitation electrode, the piezoelectric substrate, the (dielectric layer)
An appropriate capacitance can be generated between each of the conductive layers and the conductive layer, and the band suppression characteristics can be adjusted appropriately.

Further, the adjustment at this time is performed by removing the conductor layer by irradiating a laser beam after the hermetic sealing, and can be realized very simply.

Further, by adjusting the electric characteristics, the attenuation pole can be reliably arranged at an arbitrary frequency to provide an excellent surface acoustic wave filter having good attenuation characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating one embodiment of a surface acoustic wave filter according to the present invention.

FIG. 2 is a sectional view schematically illustrating an embodiment of another surface acoustic wave filter according to the present invention.

FIG. 3 is a cross-sectional view schematically illustrating an embodiment of another surface acoustic wave filter according to the present invention.

FIG. 4 is a partially transparent plan view (top view) schematically illustrating an embodiment of the surface acoustic wave filter according to the present invention.

FIG. 5 is a cross-sectional view illustrating an example of a conventional surface acoustic wave filter.

FIG. 6 is a partially transparent plan view (top view) showing an example of a conventional surface acoustic wave filter.

[Explanation of symbols]

 1: Piezoelectric substrate 2: Excitation electrode 3: Conductive layer 4: Element side extraction electrode 5: Bump electrode 6: Bump 7: Housing side internal extraction electrode 8: Housing 9: Housing side external extraction electrode 10: Sealing material 11 : Lid 12: protective film 13: dielectric substrate (dielectric layer) 14: composite substrate 15: adhesive layer S1, S2, S3: surface acoustic wave filter

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kazuhiro Otsuka 3-5-2, Seika-cho, Soraku-gun, Kyoto F-term in the Central Research Laboratory of Kyocera Corporation 5J097 AA13 BB17 DD29 EE09 EE10 FF03 FF08 GG04 HA02 HA07 HA08 HA09 HB04 HB08 JJ09 KK10

Claims (2)

[Claims] A surface acoustic wave element having a surface acoustic wave excitation electrode formed on one main surface of a piezoelectric substrate is housed in a housing having an opening with one main surface of the piezoelectric substrate facing down, A surface acoustic wave filter in which an upper surface of an opening of the housing is hermetically sealed with a lid, wherein at least a portion of the lid is provided on at least a conductor layer on the other main surface of the piezoelectric substrate. Is formed of a translucent member capable of irradiating the conductor layer with light. 2. A step of accommodating the surface acoustic wave element in the housing and hermetically sealing an upper surface of an opening of the housing with a lid, and light transmitted through a light-transmissive member of the lid. Adjusting a filter characteristic by removing a predetermined area of the conductor layer with energy,
A method for manufacturing a surface acoustic wave filter according to claim 1.