JP7370542B2 - elastic wave device - Google Patents

Description

The present invention relates to acoustic wave devices.

Due to recent technological advances, mobile communication terminals such as smartphones have become significantly smaller and lighter.

As filters used in such mobile communication terminals, elastic wave devices that can be miniaturized are used.

Further, as mobile communication systems, the number of communication systems that perform simultaneous transmission and reception is rapidly increasing, and the demand for duplexers and the like is rapidly increasing.

Under these circumstances, a multimode resonator having an unbalanced-balanced conversion function is used as a filter on the receiving side of a duplexer.

Furthermore, with changes in mobile communication systems, the required specifications for duplexers are becoming more stringent.

That is, there is a demand for acoustic wave devices such as duplexers that are smaller than conventional ones and have excellent characteristics.

Patent Document 1 discloses an example of a technology related to an elastic wave device.

Japanese Patent Application Publication No. 2014-120841

However, the technique disclosed in Patent Document 1 cannot provide an acoustic wave device that is sufficiently small and has excellent characteristics.

An object of the present invention is to provide an acoustic wave device that is smaller in size and has excellent characteristics.

The elastic wave device according to the present invention includes:
a piezoelectric substrate;
a plurality of IDT electrodes formed on the piezoelectric substrate and having a plurality of electrode fingers and bus bars made of a first metal layer;
a plurality of bridge abutments formed on the piezoelectric substrate and made of an insulator;
A main girder formed on the plurality of abutments,
The main beam intersects at least one of the IDT electrodes three-dimensionally and is made of an insulator,
a wiring pattern made of the first metal layer and the second metal layer that electrically connects the plurality of IDT electrodes;
comprising a metal layer formed on the main girder,
The metal layer is electrically connected to at least a portion of the wiring pattern and has a ground potential,
The plurality of IDT electrodes constitute a transmission filter and a reception filter including a multimode resonator, and the main beam has an area in which the plurality of IDT electrodes forming the multimode resonator are formed. , is formed to cover the space,
The metal layer has the same thickness as the second metal layer,
At least a portion of the abutment is formed on the first metal layer,
The total thickness of the abutment formed on the first metal layer and the thickness of the main girder is smaller than the thickness of the second metal layer.

In one embodiment of the present invention, at least a portion of the abutment is formed on the bus bar.

comprising reflectors disposed at both ends of the IDT electrode,
In one embodiment of the present invention, at least a portion of the abutment is formed in a region adjacent to the reflector on a side opposite to the IDT electrode.

comprising the metal layer formed on the main girder,
The metal layer has a ground potential, is formed so as to cover, with a space therebetween, a region in which a plurality of IDT electrodes forming the multimode resonator are formed, and forms the transmission filter. One form of the present invention is that the IDT electrode is not formed over the region where the IDT electrode is formed .

In one form of the present invention, the main girder is formed so as to cover, with a space therebetween, a region in which two adjacent IDT electrodes among the plurality of IDT electrodes are formed.

The reception filter includes a plurality of multimode resonators,
The main girder is formed to cover all IDT electrodes forming the plurality of multimode resonators,
The metal layer having a ground potential is formed on the main girder so as to cover all the IDT electrodes forming the plurality of multimode resonators , and the metal layer forms the transmission filter. One form of the present invention is that the IDT electrode is not formed over the region where the IDT electrode is formed .

In one form of the present invention, the area where the transmitting filter is formed occupies the piezoelectric substrate at least twice the area where the receiving filter is formed.

In one embodiment of the present invention, the piezoelectric substrate is bonded to a support substrate made of sapphire, silicon, alumina, spinel, crystal, or glass.

A module including the acoustic wave device is one form of the present invention.

According to the present invention, it is possible to provide an acoustic wave device that is smaller in size and has excellent characteristics.

1 is a cross-sectional view of an acoustic wave device according to Embodiment 1. FIG. 5 is a diagram showing an example of the configuration of a device chip 5. FIG. 3 is a diagram showing details within a dotted line frame A in FIG. 2. FIG. 4 is a diagram schematically showing a cross section taken along the dotted line B in FIG. 3. FIG. FIG. 3 is a diagram showing design areas of Example 1 and Comparative Example. FIG. 3 is a diagram showing the pass characteristics of reception filters of Example 1 and Comparative Example. FIG. 3 is a diagram showing broadband pass characteristics of reception filters of Example 1 and Comparative Example. FIG. 3 is a diagram showing isolation characteristics of Example 1 and Comparative Example. FIG. 5 is a plan view showing an example in which the acoustic wave element 52 is a surface acoustic wave resonator. FIG. 3 is a cross-sectional view of a module 100 according to a second embodiment.

Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

(Example 1)
FIG. 1 is a cross-sectional view of an acoustic wave device 1 according to a first embodiment.

As shown in FIG. 1, the acoustic wave device 1 according to this embodiment includes a wiring board 3 and a device chip 5 mounted on the wiring board 3.

In this embodiment, a transmitting filter Tx and a receiving filter Rx are configured on the device chip 5. The acoustic wave device 1 according to this embodiment is a Band 12 duplexer.

Naturally, as an object of application of the present invention, the device chip 5 may be an acoustic wave device in which one bandpass filter is formed, or may be a quatroplexer. Furthermore, a duplexer can also be realized by preparing two device chips.

As the wiring board 3, for example, a multilayer board made of resin or a multilayer board of low temperature co-fired ceramics (LTCC) made of a plurality of dielectric layers is used. Further, the wiring board 3 includes a plurality of external connection terminals 31.

A bandpass filter configured to allow electrical signals in a desired frequency band to pass is formed on the device chip 5. More specifically, a reception filter Rx including a multimode resonator is formed on the device chip 5.

A ladder type filter is further formed on the device chip 5. In this embodiment, the ladder filter is a transmission filter Tx.

For the device chip 5, a substrate made of piezoelectric single crystal such as lithium tantalate, lithium niobate, or crystal, or piezoelectric ceramics can be used, for example.

Further, the device chip 5 may be a substrate in which a piezoelectric substrate and a support substrate are bonded. As the support substrate, for example, a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate can be used.

A plurality of electrode pads 9 are formed on the wiring board 3. For the electrode pad 9, for example, copper or an alloy containing copper can be used. Further, the electrode pad 9 can have a thickness of, for example, 10 μm to 20 μm.

A sealing portion 17 is formed to cover the device chip 5. The sealing portion 17 may be formed of an insulator such as synthetic resin, or may be made of metal, for example.

As the synthetic resin, for example, epoxy resin, polyimide, etc. can be used, but the synthetic resin is not limited to these. Preferably, the sealing portion 17 is formed using an epoxy resin and using a low temperature curing process.

The device chip 5 is mounted on the wiring board 3 via the bumps 15 by flip-chip bonding.

For example, a gold bump can be used as the bump 15. The height of the bump 15 is, for example, 20 μm to 50 μm.

Electrode pad 9 is electrically connected to device chip 5 via bump 15 .

FIG. 2 is a diagram showing an example of the configuration of the device chip 5. As shown in FIG.

As shown in FIG. 2, an acoustic wave element 52 and a wiring pattern 54 are formed on the device chip 5.

A plurality of elastic wave elements 52 are formed, and some of them include multimode resonators (not shown in FIG. 2). Acoustic wave element 52 may include an IDT electrode. Acoustic wave element 52 may include a reflector adjacent the IDT electrode.

The wiring pattern 54 has a portion including only the first metal layer and a portion including the first metal layer and the second metal layer.

A main beam 62 is formed to cover a multimode resonator (not shown in FIG. 2).

The main girder 62 is arranged on a plurality of abutments 60 (not shown in FIG. 2) so as to intersect with the multimode resonator via a predetermined space.

The main beam 62 can be formed using polyimide, for example. The main beam 62 may be an insulator formed with a film thickness of 1000 nm, for example.

The main girder 62 may be made of a metal layer. When the main girder 62 is formed of a metal layer, it is desirable to secure enough space so that electrical interference with the acoustic wave element 52 does not adversely affect the characteristics of the acoustic wave device.

When the main girder 62 is formed of a metal layer, it is desirable that the main girder 62 be at ground potential. This strengthens the ground, reduces insertion loss, improves attenuation characteristics over a wide band, and improves isolation characteristics over a wide band.

When the main beam 62 is made of an insulator, a metal layer may be formed on the main beam 62. It is desirable that the metal layer formed on the main girder 62 be at ground potential.

This strengthens the ground, reduces insertion loss, improves attenuation characteristics over a wide band, and improves isolation characteristics over a wide band.

The wiring pattern 54 includes a three-dimensional wiring section 58 in which the first metal layer and/or the second metal layer and the metal layer formed on the insulator are wired to three-dimensionally intersect with each other via an insulator. have For example, polyimide can be used as the insulator. The insulator is formed to have a thickness of 1000 nm, for example.

The acoustic wave element 52 and the wiring pattern 54 can be formed of a suitable metal or alloy such as silver, aluminum, copper, titanium, palladium, etc., for example. Moreover, these metal patterns may be formed of a laminated metal film formed by laminating a plurality of metal layers. The thickness of the acoustic wave element 52 and the wiring pattern 54 can be, for example, from 150 nm to 8000 nm.

The wiring pattern 54 includes wiring constituting an antenna pad ANT, a transmission signal input pad TxIn, a reception signal output pad RxOut, and a ground pad GND. Further, the wiring pattern 54 is electrically connected to the acoustic wave element 52.

As shown in FIG. 2, a bandpass filter can be configured by forming a plurality of elastic wave elements 52. The bandpass filter is designed to pass only electrical signals in a desired frequency band among the electrical signals input from the antenna pad ANT or the transmission signal input pad TxIn.

An electrical signal input from the antenna pad ANT or the input pad TxIn for the transmission signal passes through a bandpass filter, and an electrical signal in a desired frequency band is output to the antenna pad ANT or the output pad RxOut for the reception signal.

The electrical signal output to the antenna pad ANT or the received signal output pad RxOut is output from the external connection terminal 31 of the wiring board 3 via the bump 15 and the electrode pad 9.

FIG. 3 is a diagram showing details within the dotted line frame A in FIG.

As shown in FIG. 3, four acoustic wave elements 52 are formed on the device chip 5. Each of these four acoustic wave elements 52 is a multimode resonator in which three IDT electrodes are arranged in series.

As shown in FIG. 3, a plurality of abutments 60 are arranged on the device chip 5. The abutment 60 can be formed using polyimide, for example. The abutment 60 may be an insulator formed with a thickness of 1000 nm, for example.

When the abutment 60 is made of an insulator, the abutment 60 may be formed on the wiring pattern 54 or the bus bar.

The acoustic wave element 52 includes a reflector, and as shown in FIG. 3, a part of the abutment 60 is formed in a region adjacent to the reflector on the opposite side from the IDT electrode.

In addition, in FIG. 3, in order to clarify the arrangement example of the abutment 60, the main girder 62 and the metal layer arranged on the main girder 62 are omitted, but the acoustic wave device according to this embodiment 1, all the IDT electrodes of the four multimode resonators are covered by the main beam 62 and are arranged to intersect with each other.

Further, all the IDT electrodes of the four multimode resonators are covered with a metal layer which is placed on the main girder 62 and is at ground potential.

A metal layer may be provided on the entire surface of the main girder 62 to strengthen the ground.

A microstrip line may be provided on the main beam 62 to form an inductance element. A comb-shaped electrode may be provided on the main beam 62 to form a capacitive element. Moreover, you may combine these.

FIG. 4 is a diagram schematically showing a cross section taken along the dotted line B in FIG.

As shown in FIG. 4, an acoustic wave element 52 and a wiring pattern 54 (first metal layer 541) are formed on the device chip 5.

A bridge abutment 60 is formed on the first metal layer 541. The abutment 60 was made of polyimide with a thickness of 1000 nm.

A main girder 62 is formed on the abutment 60. The main beam 62 was made of polyimide with a thickness of 1000 nm.

A metal layer M is formed on the main beam 62. The metal layer M had a thickness of 4000 nm and had a ground potential.

Further, the metal layer M was formed simultaneously with the second metal layer 542 constituting the wiring pattern 54 on the first metal layer 541 of the wiring pattern 54 in a region other than the region where the main girder 62 is formed.

FIG. 5 is a diagram showing design areas of Example 1 and Comparative Example.

FIG. 5(a) shows a duplexer according to a comparative example. The duplexer according to the comparative example does not include the abutment, the main girder, and the metal layer at ground potential formed on the main girder. The duplexer according to the comparative example has a device chip size and basic design equivalent to the acoustic wave device according to Example 1, but the abutment, the main girder, and the metal layer at ground potential formed on the main girder are The design is optimized assuming a configuration that does not include

The area RxDA(a) surrounded by the dotted line in FIG. 5(a) shows the design area of the reception filter when the design is optimized as a duplexer in the comparative example. The area RxDA(a) was 487136.2 micro square meters.

FIG. 5(b) shows a duplexer according to the first embodiment. The area RxDA(b) surrounded by the dotted line in FIG. 5(b) shows the design area of the reception filter when the design is optimized as a duplexer in the first embodiment. The area RxDA(a) was 446246.2 micro square meters.

The duplexer of Example 1 was able to reduce the design area of the reception filter by about 8.4% compared to the comparative example.

As a result, in the duplexer of Example 1, the area where the transmission filter is formed accounts for more than twice the area of the entire area of the device chip 5 than the area where the reception filter is formed.

By increasing the design area of the transmission filter, it is possible to provide an acoustic wave device with improved power resistance and the like.

Moreover, thereby, it is also possible to reduce the size of the acoustic wave device while improving the characteristics compared to the conventional one.

FIG. 6 is a diagram showing the pass characteristics of the reception filters of Example 1 and Comparative Example.

As shown in FIG. 6, the waveform indicated by the solid line indicates the pass characteristic of the reception filter included in the elastic wave device of this embodiment.

Furthermore, the waveform indicated by the broken line indicates the pass characteristic of the reception filter included in the elastic wave device of the comparative example. The elastic wave device of the comparative example is the same as the elastic wave device shown as the comparative example in FIG.

As shown in FIG. 6, it can be seen that the present example is superior to the comparative example in the passband characteristics of the reception filter.

FIG. 7 is a diagram showing broadband pass characteristics of the reception filters of Example 1 and Comparative Example.

As shown in FIG. 7, the waveform indicated by the solid line indicates the broadband pass characteristic of the reception filter included in the elastic wave device of this embodiment.

Further, the waveform indicated by the broken line indicates the broadband pass characteristic of the reception filter included in the elastic wave device of the comparative example. The elastic wave device of the comparative example is the same as the elastic wave device shown as the comparative example in FIG.

As shown in FIG. 7, it can be seen that the present example is superior to the comparative example in the broadband pass characteristics in the attenuation band.

FIG. 8 is a diagram showing isolation characteristics of Example 1 and Comparative Example.

As shown in FIG. 8, the waveform shown by the solid line indicates the isolation characteristic of the acoustic wave device of this example.

Furthermore, the waveform indicated by the broken line indicates the isolation characteristic of the acoustic wave device of the comparative example. The elastic wave device of the comparative example is the same as the elastic wave device shown as the comparative example in FIG.

As shown in FIG. 8, it can be seen that the isolation characteristics of this example are superior to those of the comparative example.

That is, according to the present invention, it is possible to provide an acoustic wave device that is smaller and has excellent characteristics.

FIG. 9 is a plan view showing an example in which the acoustic wave element 52 is a surface acoustic wave resonator.

As shown in FIG. 9, an IDT (Interdigital Transducer) 52a that excites surface acoustic waves and a reflector 52b are formed on the device chip 5. The IDT 52a has a pair of comb-shaped electrodes 52c facing each other.

The comb-shaped electrode 52c has a plurality of electrode fingers 52d and a bus bar 52e that connects the plurality of electrode fingers 52d. The reflectors 52b are provided on both sides of the IDT 52a.

The IDT 52a and the reflector 52b are made of, for example, an alloy of aluminum and copper. The IDT 52a and the reflector 52b are thin films with a thickness of, for example, 150 nm to 400 nm.

The IDT 52a and the reflector 52b may contain or be formed of other metals, such as titanium, palladium, silver, or alloys thereof.

Further, the IDT 52a and the reflector 52b may be formed of a laminated metal film formed by laminating a plurality of metal layers.

The elastic wave element 52 can be appropriately employed in a multimode filter or a ladder filter so as to obtain desired characteristics as a bandpass filter.

(Example 2)
Next, Example 2, which is another embodiment of the present invention, will be described.

FIG. 10 is a sectional view of a module 100 according to Example 2 of the present invention.

As shown in FIG. 10, the acoustic wave device 1 is mounted on the main surface of the wiring board 130.

The acoustic wave device 1 can be, for example, a duplexer employing the configuration described in the first embodiment or the second embodiment.

The wiring board 130 has a plurality of external connection terminals 131. The plurality of external connection terminals 131 are configured to be mounted on the motherboard of a predetermined mobile communication terminal.

An inductor 111 is mounted on the main surface of the wiring board 130 for impedance matching. Inductor 111 may be an integrated passive device (IPD).

The module 100 is sealed with a sealing part 117 for sealing a plurality of electronic components including the acoustic wave device 1.

An integrated circuit component IC is mounted inside the wiring board 130. Although not shown, the integrated circuit component IC includes a switching circuit and a low noise amplifier.

The other configurations are the same as those described in Example 1 or Example 2, and will therefore be omitted.

According to the embodiments of the present invention described above, it is possible to provide a module that is smaller and includes an acoustic wave device with excellent characteristics.

Note that, as a matter of course, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the object of the present invention.

Additionally, while certain aspects of at least one embodiment have been described above, it is to be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art.

Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of the invention.

It should be understood that the method and apparatus embodiments described herein are not limited to application to the details of structure and arrangement of components described in the foregoing description or illustrated in the accompanying drawings.

The methods and apparatus may be implemented in other embodiments and of being practiced or carried out in various ways.

Specific implementations are provided herein for illustrative purposes only and are not intended to be limiting.

Additionally, the expressions and terminology used herein are for descriptive purposes and should not be considered limiting.

The use of "comprising," "comprising," "having," "including" and variations thereof herein means the inclusion of the items listed below and their equivalents and additional items.

References to "or" shall be construed to mean that any term listed using "or" refers to one, more than one, and all of the listed terms. can be done.

All references to front-back, left-right, apex-bottom, and horizontal and vertical are intended for convenience of description and are not intended to limit the elements of the invention to any one positional or spatial orientation. Accordingly, the above description and drawings are illustrative only.

1 Acoustic wave device 3 130 Wiring board 5 105 Device chip 9 Electrode pad 15 Bump 17 117 Sealing part 31 131 External connection terminal 52 Acoustic wave element 54 Wiring pattern 541 First metal layer 542 Second metal layer 100 Module 111 Inductor 112 2 inductor IC integrated circuit parts

Claims (9)

a piezoelectric substrate;
a plurality of IDT electrodes formed on the piezoelectric substrate and having a plurality of electrode fingers and bus bars made of a first metal layer;
a plurality of bridge abutments formed on the piezoelectric substrate and made of an insulator;
A main girder formed on the plurality of abutments,
The main beam intersects at least one of the IDT electrodes three-dimensionally and is made of an insulator,
a wiring pattern made of the first metal layer and the second metal layer that electrically connects the plurality of IDT electrodes;
comprising a metal layer formed on the main girder,
The metal layer is electrically connected to at least a portion of the wiring pattern and has a ground potential,
The plurality of IDT electrodes constitute a transmission filter and a reception filter including a multimode resonator, and the main beam has an area in which the plurality of IDT electrodes forming the multimode resonator are formed. , is formed to cover the space,
The metal layer has the same thickness as the second metal layer,
At least a portion of the abutment is formed on the first metal layer,
The total thickness of the abutment formed on the first metal layer and the main girder is smaller than the thickness of the second metal layer. The acoustic wave device according to claim 1 , wherein at least a portion of the abutment is formed on the bus bar. comprising reflectors disposed at both ends of the IDT electrode,
3. The acoustic wave device according to claim 1 , wherein at least a portion of the abutment is formed in a region adjacent to the reflector on a side opposite to the IDT electrode. comprising the metal layer formed on the main girder,
The metal layer has a ground potential, is formed so as to cover, with a space therebetween, a region in which a plurality of IDT electrodes forming the multimode resonator are formed, and forms the transmission filter. The acoustic wave device according to any one of claims 1 to 3, wherein the acoustic wave device is not formed on a region where an IDT electrode is formed. The elastic device according to any one of claims 1 to 4, wherein the main beam is formed so as to cover, with a space therebetween, a region in which two adjacent IDT electrodes are formed among the plurality of IDT electrodes. wave device. The reception filter includes a plurality of multimode resonators,
The main girder is formed to cover all IDT electrodes forming the plurality of multimode resonators,
The metal layer having a ground potential is formed on the main girder so as to cover all the IDT electrodes forming the plurality of multimode resonators, and the metal layer forms the transmission filter. The acoustic wave device according to any one of claims 1 to 5, which is not formed on a region where an IDT electrode is formed. According to any one of claims 1 to 6 , the area where the transmission filter is formed occupies the piezoelectric substrate at least twice the area where the reception filter occupies the piezoelectric substrate. elastic wave device. 8. The acoustic wave device according to claim 1, wherein the piezoelectric substrate is bonded to a support substrate made of sapphire, silicon, alumina, spinel, crystal, or glass. A module comprising the elastic wave device according to claim 1 .