JP7055503B1 - Elastic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elastic wave device using a multimode resonator having a passband characteristic which is closer to a rectangle, has low loss and is excellent in steepness, and a module including the elastic wave device. An elastic wave device including a piezoelectric substrate and a bandpass filter formed on the piezoelectric substrate and including a multiple mode type resonator, wherein the multiple mode type resonator is a first IDT electrode. The second IDT electrode, the third IDT electrode, the fourth IDT electrode and the fifth IDT electrode are provided, and the logarithm of the third IDT electrode is the first IDT electrode, the second IDT electrode, and the like. An elastic wave device that is greater than the sum of the pairs of the fourth IDT electrode and the fifth IDT electrode. [Selection diagram] Fig. 2

Description

The present invention relates to elastic wave devices.

Due to recent technological advances, smartphones and the like represented by mobile communication terminals have been remarkably reduced in size and weight. As a filter used in such a mobile communication terminal, an elastic wave device capable of miniaturization is used. Further, as a mobile communication system, the number of communication systems for 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 the duplexer. Furthermore, with the changes in mobile communication systems, the required specifications of duplexers are becoming more stringent. That is, there is a need for a multi-mode resonator that is closer to a rectangle than conventional ones, has low loss, and has excellent passband characteristics.

Patent Document 1 discloses an example of a technique relating to an elastic wave device.

JP-A-2020-141380

However, the technique disclosed in Patent Document 1 cannot provide an elastic wave device using a multimode resonator having sufficient passband characteristics. An object of the present invention is to provide an elastic wave device using a multi-mode resonator having a passband characteristic that is closer to a rectangle, has low loss, and is excellent in steepness.

The elastic wave device according to the present invention is
Piezoelectric board and
An elastic wave device formed on the piezoelectric substrate and provided with a bandpass filter including a multi-mode resonator.
The multimode resonator includes a first IDT electrode, a second IDT electrode, a third IDT electrode, a fourth IDT electrode, and a fifth IDT electrode.
The number of pairs of the third IDT electrode is greater than the sum of the pairs of the first IDT electrode, the second IDT electrode, the fourth IDT electrode, and the fifth IDT electrode.
The wiring pattern of the bandpass filter includes a first metal layer, a second metal layer formed on the first metal layer, and an insulator formed between the first metal layer and the second metal layer. The first metal layer is surrounded by the signal line of the third IDT electrode and has an isolated island pattern, and the island pattern is the second IDT via the second metal layer. An elastic wave device electrically connected to the electrode and the ground line of the fourth IDT electrode was used.

It is one embodiment of the present invention that the logarithm of the first IDT electrode and the logarithm of the fifth IDT electrode are equivalent.

It is one embodiment of the present invention that the logarithm of the second IDT electrode and the logarithm of the fourth IDT electrode are equivalent.

One embodiment of the present invention is that the piezoelectric substrate has a substrate made of sapphire, silicon, alumina, spinel, crystal or glass bonded to a main surface opposite to the surface on which the bandpass filter is formed. Will be done.

It is one aspect of the present invention that the bandpass filter is a reception filter and is a duplexer provided with a transmission filter.

One aspect of the present invention is that the pass band of the reception filter has a lower frequency than the pass band of the transmission filter.

It is one embodiment of the present invention that the transmission filter includes a plurality of resonators arranged in a ladder type.

It is one aspect of the present invention that the plurality of resonators arranged in the ladder type of the transmission filter are acoustic thin film resonators.

It is one aspect of the present invention that the transmission filter is formed on the piezoelectric substrate.

A module including the elastic wave device is one embodiment of the present invention.

According to the present invention, it is possible to provide an elastic wave device using a multi-mode resonator having a passband characteristic that is closer to a rectangle, has low loss, and is excellent in steepness.

FIG. 1 is a cross-sectional view of the elastic wave device 1 according to the first embodiment. FIG. 2 is a diagram showing a configuration example of the device chip 5 (Rx). FIG. 3 is a diagram showing the resonance characteristics of the multiple mode type resonators of the present embodiment and the comparative example. FIG. 4 is a diagram showing the pass characteristics of the bandpass filters of the present embodiment and the comparative example. FIG. 5 shows a region FIG. 5 surrounded by a broken line in FIG. It is a figure for demonstrating the structure of 5. FIG. 6 is a diagram showing a configuration example of the device chip 5 (Tx). FIG. 7 is a plan view showing an example in which the surface acoustic wave element 52 is an elastic surface wave resonator. FIG. 8 is a cross-sectional view showing an example in which the elastic wave element 52 is a piezoelectric thin film resonator. FIG. 9 is a diagram showing the band characteristics of the duplexer according to the first embodiment. FIG. 10 is a diagram showing a configuration example of the device chip 105 according to the second embodiment. FIG. 11 is a cross-sectional view of the module 100 according to the third embodiment of the present invention.

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

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

As shown in FIG. 1, the elastic wave device 1 according to this embodiment includes a wiring board 3 and two device chips 5 mounted on the wiring board 3. In this embodiment, an example of an elastic wave device which is a duplexer in which the device chip 5 (Rx) is used as a receiving filter and the device chip 5 (Tx) is used as a transmission filter is shown. As a result, an elastic wave device as a bandpass filter having one device chip 5 may be used, or a quattroplexer may be used. It is also possible to form a functional element that realizes a duplexer on one device chip.

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

A bandpass filter configured to pass an electric signal in a desired frequency band is formed on the device chip 5. A bandpass filter including a multiple mode resonator 7 is formed on the device chip 5 (Rx). In this embodiment, the device chip 5 (Rx) is a reception filter.

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

As the device chip 5, for example, a substrate made of a piezoelectric single crystal such as lithium tantalate, lithium niobate or quartz, or a piezoelectric ceramic can be used. Alternatively, as will be described later, in a bandpass filter using an acoustic thin film resonator, a semiconductor substrate such as silicon or an insulating substrate such as sapphire, alumina, spinel or glass can be used.

Further, as the device chip 5, a substrate to which a piezoelectric substrate and a support substrate are bonded may be used. 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 so as to cover the device chip 5. The sealing portion 17 may be formed of, for example, an insulator such as a synthetic resin, or a metal may be used. As the synthetic resin, for example, epoxy resin, polyimide and the like can be used, but the synthetic resin is not limited thereto. Preferably, an epoxy resin is used and a low temperature curing process is used to form the sealing portion 17.

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

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

The electrode pad 9 is electrically connected to the device chip 5 via the bump 15.

FIG. 2 is a diagram showing a configuration example of the device chip 5 (Rx).

As shown in FIG. 2, the elastic wave element 52 and the wiring pattern 54 are formed on the device chip 5 (Rx).

The elastic wave element 52 includes a multiple mode resonator 7. The multimode resonator 7 includes a first IDT electrode 71, a second IDT electrode 72, a third IDT electrode 73, a fourth IDT electrode 74, and a fifth IDT electrode 75.

In this embodiment, the logarithm of the first IDT electrode 71 is 18. The logarithm of the second IDT electrode 72 is 22. The logarithm of the third IDT electrode 73 is 96.5. The logarithm of the fourth IDT electrode 74 is 22. The logarithm of the fifth IDT electrode 75 is 18. That is, the number of pairs of the third IDT electrode 73 is larger than the total number of pairs of the first IDT electrode 71, the second IDT electrode 72, the fourth IDT electrode 74, and the fifth IDT electrode 75.

The logarithm of the first IDT electrode 71 and the logarithm of the fifth IDT electrode 75 are 18, which are equivalent. Further, the logarithm of the second IDT electrode 72 and the logarithm of the fourth IDT electrode 74 are 22, which are equivalent.

The wiring pattern 54 includes a first metal layer and a second metal layer (not shown in FIG. 2), and an insulator (not shown in FIG. 2) is provided between the first metal layer and the second metal layer. It is formed. As the insulator, for example, polyimide can be used. The insulator is formed, for example, with a film thickness of 1000 nm.

The wiring pattern 54 has a three-dimensional wiring portion 58 in which the first metal layer and the second metal layer are wired so as to sterically intersect with each other via an insulator.

The elastic wave element 52 and the wiring pattern 54 can be formed of, for example, an appropriate metal or alloy such as silver, aluminum, copper, titanium, or palladium. Further, these metal patterns may be formed by a laminated metal film formed by laminating a plurality of metal layers. The thickness of the elastic wave element 52 and the wiring pattern 54 can be, for example, 150 nm to 400 nm.

The wiring pattern 54 includes wiring constituting the input pad In, the output pad Out, and the ground pad GND. Further, the wiring pattern 54 is electrically connected to the elastic wave element 52.

As shown in FIG. 2, the third IDT electrode 73 is electrically connected by a plurality of three-dimensional wiring portions 58 via an output pad Out and an elastic wave element 52 directly electrically connected to the output pad Out. It is connected.

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 the electric signal of a desired frequency band among the electric signals input from the input pad In.

The electric signal input from the input pad In passes through the bandpass filter, and the electric signal in a desired frequency band is output to the output pad Out.

The electric signal output to the output pad Out 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 the resonance characteristics of the multiple mode type resonators of the present embodiment and the comparative example.

The waveform shown by the solid line shows the resonance characteristics of the multimode resonator 7 of the elastic wave device of this embodiment. Further, the waveform shown by the broken line shows the resonance characteristics of the multiple mode type resonator of the comparative example. In the multiple mode type resonator of the comparative example, the number of pairs of the first IDT electrode is 18, the number of the second IDT electrode is 22, the number of the third IDT electrode is 78.5, and the number of the fourth IDT electrode is 7. 22, the log of the fifth IDT electrode was set to 18. Other conditions were the same as those of the multiple mode resonator 7 of this embodiment.

As shown in FIG. 3, the characteristics of the pass band are the same in both the present embodiment and the comparative example, but the attenuation of the present embodiment is from the region where the frequency is higher than the vicinity of 820 MHz, which is outside the pass band. It can be seen that the characteristics are excellent.

FIG. 4 is a diagram showing the pass characteristics of the bandpass filters of the present embodiment and the comparative example.

The waveform shown by the solid line shows the passing characteristics of the bandpass filter of the elastic wave device of this embodiment. Further, the waveform shown by the broken line shows the passing characteristics of the comparative example. The bandpass filter of the comparative example is a bandpass filter using the multiple mode type resonator of the comparative example having the resonance characteristic shown in FIG. Other conditions were the same as those of the bandpass filter of this example.

As shown in FIG. 4, the characteristics of the pass band are the same in both the present embodiment and the comparative example, but the attenuation of the present embodiment is from a region where the frequency is higher than around 820 MHz, which is outside the pass band. It can be seen that the characteristics are excellent.

That is, according to the present invention, it is possible to provide an elastic wave device using a multi-mode resonator having a passband characteristic that is closer to a rectangle, has low loss, and is excellent in steepness.

FIG. 5 shows a region FIG. 5 surrounded by a broken line in FIG. It is a figure for demonstrating the structure of 5.

As shown in FIG. 5, the first metal layer 54M1 is formed on the device chip 5 (Rx). Further, an island pattern IP surrounded by and insulated from the signal line L73 of the third IDT electrode 73, which is the first metal layer 54M1, is formed.

A ground line GL of the second IDT electrode 72 and the fourth IDT electrode 74 is formed. Further, a second metal layer 54M2 that electrically connects the ground line GL and the island pattern IP is formed. Further, an insulator 56 is formed between the second metal layer 54M2 and the signal line L73.

As described above, the signal line L73, the insulator 56, and the second metal layer 54M2 constitute a three-dimensional wiring portion 58 to be three-dimensionally wired.

Since the third IDT electrode 73 of the present invention has a large width, there is a problem that the insulator 56 is peeled off. Therefore, the inventor has solved the problem that the insulator 56 is peeled off by dividing the three-dimensional wiring related to the wiring to the third IDT electrode 73 and performing wiring by a plurality of three-dimensional wirings.

Further, as shown in FIG. 5, two island pattern IPs may be formed to form three three-dimensional wiring portions 58, or one island pattern IP may be formed to form two three-dimensional wiring portions 58. You may. When forming one island pattern IP, it may be lengthened if necessary.

Here, depending on the thickness and area of the insulator 56, the three-dimensional wiring portion 58 has a parasitic capacitance between the signal line L73 and the second metal layer 54M2 which is the ground line GL, which affects the characteristics of the bandpass filter. It may end up. The thicker the insulator 56, the smaller the parasitic capacitance, but the easier it is for the insulator 56 to peel off. Further, the larger the area of the insulator 56, the more difficult it is to peel off, but the larger the parasitic capacitance.

Further, if the island pattern IP is made long, the parasitic capacitance can be reduced, but if it is made too long, the wiring pattern 54 of the signal line L73 becomes narrow and the resistance value increases.

According to the configuration of the present invention, it is possible to design in an optimized manner while preventing the insulation 56 from peeling off and the characteristics from being deteriorated due to parasitic capacitance. According to the configuration of the present invention, it is possible to provide an elastic wave device having a high degree of freedom in design and excellent characteristics.

FIG. 6 is a diagram showing a configuration example of the device chip 5 (Tx).

As shown in FIG. 6, the elastic wave element 52 and the wiring pattern 54 are formed on the device chip 5 (Tx).

The elastic wave element 52 and the wiring pattern 54 can be formed of, for example, an appropriate metal or alloy such as silver, aluminum, copper, titanium, or palladium. Further, these metal patterns may be formed by a laminated metal film formed by laminating a plurality of metal layers. The thickness of the elastic wave element 52 and the wiring pattern 54 can be, for example, 150 nm to 400 nm.

The wiring pattern 54 includes wiring constituting the input pad In, the output pad Out, and the ground pad GND. Further, the wiring pattern 54 is electrically connected to the elastic wave element 52.

As shown in FIG. 6, a bandpass filter can be configured by forming a plurality of elastic wave elements 52. A plurality of elastic wave elements 52 are formed and arranged in a ladder type as either a series resonator or a parallel resonator. The bandpass filter is designed to pass only the electric signal of a desired frequency band among the electric signals input from the input pad In.

The electric signal input from the input pad In passes through the bandpass filter, and the electric signal in a desired frequency band is output to the output pad Out.

The electric signal output to the output pad Out is output from the external connection terminal 31 of the wiring board 3 via the bump 15 and the electrode pad 9.

FIG. 7 is a plan view showing an example in which the surface acoustic wave element 52 is an elastic surface wave resonator.

As shown in FIG. 7, an IDT (Interdigital Transducer) 52a and a reflector 52b that excite surface acoustic waves 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 bus bar 52e that connects a plurality of electrode fingers 52d and a plurality of electrode fingers 52d. 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 having a thickness of, for example, 150 nm to 400 nm. The IDT 52a and the reflector 52b may contain other metals, such as any suitable metal such as titanium, palladium, silver or alloys thereof, or may be formed of these alloys. Further, the IDT 52a and the reflector 52b may be formed of a laminated metal film formed by laminating a plurality of metal layers.

FIG. 8 is a cross-sectional view showing an example in which the elastic wave element 52 is a piezoelectric thin film resonator.

As shown in FIG. 8, the piezoelectric film 62 is provided on the chip substrate 60. The lower electrode 64 and the upper electrode 66 are provided so as to sandwich the piezoelectric film 62. A gap 68 is formed between the lower electrode 64 and the chip substrate 60. The lower electrode 64 and the upper electrode 66 excite elastic waves in the thickness longitudinal vibration mode in the piezoelectric film 62.

As the chip substrate 60, for example, a semiconductor substrate such as silicon or an insulating substrate such as sapphire, alumina, spinel or glass can be used. For the piezoelectric film 62, for example, aluminum nitride can be used. For the lower electrode 64 and the upper electrode 66, for example, a metal such as ruthenium can be used.

The elastic wave element 52 can be appropriately adopted in a multiple mode type filter or a ladder type filter so that the characteristics as a desired bandpass filter can be obtained.

FIG. 9 is a diagram showing the band characteristics of the duplexer according to the first embodiment.

As shown in FIG. 9, in the duplexer according to the first embodiment, the pass band Rx of the reception filter has a lower frequency than the pass band Tx of the transmission filter. In a duplexer having such a frequency relationship, the receiving filter is required to steeply suppress the high frequency side of the pass band Rx of the receiving filter. In general, it is difficult for a multiple mode type filter to steeply suppress the high frequency side of the pass band, but according to the present invention, even with a duplexer having such a frequency relationship, the pass band and transmission of the receive filter Excellent pass characteristics can be obtained for both the pass band of the filter.

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

FIG. 10 is a diagram showing a configuration example of the device chip 105 according to the second embodiment.

As shown in FIG. 10, a reception filter RxBPF and a transmission filter TxBPF are formed on one device chip 105. This makes it possible to provide an elastic wave device as a duplexer with one device chip.

As shown in FIG. 10, the input terminal In (Rx) of the reception filter RxBPF and the output terminal Out (Tx) of the transmission filter TxBPF are common terminals. Further, it is desirable that the output terminal Out (Rx) of the reception filter RxBPF and the input terminal In (Tx) of the transmission filter TxBPF are arranged farthest from each other on the device chip 105. This is because the interference between the reception filter RxBPF and the transmission filter TxBPF can be reduced, and the characteristics of the duplexer are improved.

Further, in the design of the reception filter RxBPF and the transmission filter TxBPF on one device chip, the reception filter RxBPF is preferably a multi-mode type filter in order to save space and secure suppression outside the pass band, and the transmission filter TxBPF is used. It is desirable to use a ladder type filter to ensure power resistance.

As for other configurations, the same configurations as those in the first embodiment can be adopted, and thus the description thereof will be omitted.

(Example 3)
Next, Example 3 which is another embodiment of the present invention will be described.

FIG. 11 is a cross-sectional view of the module 100 according to the third embodiment of the present invention.

As shown in FIG. 11, the elastic wave device 1 is mounted on the main surface of the wiring board 130. The elastic wave device 1 can be, for example, a duplexer adopting the configuration described in the first or 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. The inductor 111 can be an Integrated Passive Device (IPD). The module 100 is sealed by a sealing portion 117 for sealing a plurality of electronic components including the elastic 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.

Other configurations are omitted because they overlap with the contents described in the first or second embodiment.

According to the embodiment of the present invention described above, an elastic wave device using a multimode resonator having a passband characteristic that is closer to a rectangular shape, has low loss, and is excellent in steepness, and a module including the elastic wave device are provided. Can be provided.

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.

Also, although some aspects of at least one embodiment have been described above, it should be appreciated that various modifications, modifications and improvements are readily recalled to those of skill in the art. Such modifications, 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 methods and embodiments of the apparatus described herein are not limited to application to the details of the structure and arrangement of the components described above or illustrated in the accompanying drawings. Methods and devices can be implemented in other embodiments and implemented or implemented in various embodiments. Specific implementation examples are given herein for illustrative purposes only and are not intended to be limited. Also, the expressions and terms used herein are for explanatory purposes only and should not be considered limiting. The use of "include", "provide", "have", "include" and variations thereof herein means inclusion of the items listed below and their equivalents and additional items. References to "or (or)" shall be construed so that any term described using "or (or)" refers to one, more than, and all of the terms in the description. Can be done. References to front-back, left-right, top-bottom top-bottom, and horizontal-vertical are intended for convenience of description, and the components of the present invention are not limited to any one of the positional or spatial orientations. Therefore, the above description and drawings are merely examples.

1 Elastic wave device 3 130 Wiring board 5 105 Device chip 7 Multiple mode type resonator 9 Electrode pad 15 Bump 17 117 Sealed part 31 131 External connection terminal 52 Elastic wave element 54 Wiring pattern 54M1 First metal layer 54M2 Second metal layer 56 Insulator IP Island Pattern GL Ground Line 60 Chip Substrate 62 Pietrical Film 64 Lower Electrode 66 Upper Electrode 68 Void 71 First IDT Electrode 72 Second IDT Electrode 73 Third IDT Electrode L73 Signal Line 74 Fourth IDT Electrode 75 Fifth IDT electrode 100 module 111 inductor 112 Second inductor IC integrated circuit component

Claims (10)

Piezoelectric board and
An elastic wave device formed on the piezoelectric substrate and provided with a bandpass filter including a multi-mode resonator.
The multimode resonator includes a first IDT electrode, a second IDT electrode, a third IDT electrode, a fourth IDT electrode, and a fifth IDT electrode.
The number of pairs of the third IDT electrode is greater than the sum of the pairs of the first IDT electrode, the second IDT electrode, the fourth IDT electrode, and the fifth IDT electrode.
The wiring pattern of the bandpass filter includes a first metal layer, a second metal layer formed on the first metal layer, and an insulator formed between the first metal layer and the second metal layer. The first metal layer is surrounded by the signal line of the third IDT electrode and has an isolated island pattern, and the island pattern is the second IDT via the second metal layer. An elastic wave device that is electrically connected to the electrode and the ground line of the fourth IDT electrode. The elastic wave device according to claim 1, wherein the logarithm of the first IDT electrode and the logarithm of the fifth IDT electrode are equivalent. The elastic wave device according to claim 1 or 2, wherein the logarithm of the second IDT electrode and the logarithm of the fourth IDT electrode are equivalent. Any one of claims 1 to 3 in which the piezoelectric substrate has a substrate made of sapphire, silicon, alumina, spinel, crystal or glass bonded to a main surface opposite to the surface on which the bandpass filter is formed. The elastic wave device described in the section . The elastic wave device according to any one of claims 1 to 4, wherein the bandpass filter is a reception filter and is a duplexer including a transmission filter. The elastic wave device according to claim 5, wherein the pass band of the reception filter has a lower frequency than the pass band of the transmission filter. The elastic wave device according to claim 5 or 6, wherein the transmission filter includes a plurality of resonators arranged in a ladder type. The elastic wave device according to claim 7, wherein the plurality of resonators arranged in the ladder type of the transmission filter are acoustic thin film resonators. The elastic wave device according to any one of claims 5 to 7 , wherein the transmission filter is formed on the piezoelectric substrate. A module comprising the elastic wave device according to any one of claims 1 to 9 .

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