CN114844484A - Elastic wave device and module including the same - Google Patents

Abstract

An elastic wave device comprising a transmission filter having a transmission bandpass and a reception filter having a reception bandpass, said transmission filter comprising a plurality of series resonators and a plurality of parallel resonators, at least one of said series resonators having an anti-resonance frequency which is the same as the highest frequency of said reception bandpass. Thereby, an elastic wave device which is smaller and has excellent isolation characteristics, and a module including the elastic wave device are provided.

Description

Elastic wave device and module including the same

Technical Field

The present invention relates to an elastic wave device and a module including the elastic wave device.

Background

In recent years, with the progress of technology, smart phones represented by mobile communication terminals and the like have been significantly reduced in size and weight. For the filter applied to the mobile communication terminal, an elastic wave device that can be miniaturized is used. Also, in a mobile communication system, a demand for a communication system capable of simultaneously receiving and transmitting, for example, a duplexer, has sharply increased.

In such a case, the requirements for the specifications of the acoustic wave device such as the duplexer have become more stringent. In other words, an acoustic wave device such as a duplexer which is smaller than conventional ones and has excellent isolation characteristics is required.

Patent document 1 (kokai 2014-120841) exemplifies an elastic wave device including a plurality of filters, which is provided with an additional circuit for improving isolation characteristics.

Disclosure of Invention

The invention provides an elastic wave device which is smaller and has excellent isolation characteristics.

An elastic wave device comprising a transmission filter having a transmission bandpass and a reception filter having a reception bandpass, said transmission filter comprising a plurality of series resonators and a plurality of parallel resonators, at least one of said series resonators having an anti-resonance frequency which is the same as the highest frequency of said reception bandpass.

In one aspect of the present invention, the series resonator having an anti-resonance frequency equal to the highest frequency of the reception bandpass is provided in the closest position to the input terminal of the transmission filter.

In one aspect of the present invention, the series resonator having the same anti-resonance frequency as the highest frequency of the reception bandpass has a capacitance value smaller than an average value of capacitance values of the other series resonators.

In one aspect of the present invention, the series resonator having the anti-resonance frequency equal to the highest frequency of the reception bandpass has a capacitance value larger than an average value of capacitance values of the parallel resonators.

In one aspect of the present invention, at least one of the transmission filter and the reception filter is a filter using a piezoelectric thin film resonator.

In one aspect of the present invention, at least one of the transmission filter and the reception filter is a filter using a surface acoustic wave resonator formed on a piezoelectric substrate.

In one aspect of the present invention, the transmission filter and the reception filter are filters using surface acoustic wave resonators, and are formed on the same piezoelectric substrate.

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

In one aspect of the present invention, a filter of a piezoelectric thin film resonator includes a chip substrate, a piezoelectric film provided on the chip substrate, a lower electrode, and an upper electrode, the piezoelectric film is sandwiched between the lower electrode and the upper electrode, a gap is formed between the lower electrode and the chip substrate, and the lower electrode and the upper electrode excite an elastic wave in a thickness longitudinal vibration mode in the piezoelectric film.

In one aspect of the present invention, a module including the elastic wave device is provided.

The invention has the beneficial effects that: according to the present invention, it is possible to provide an elastic wave device that is smaller and has excellent isolation characteristics.

Drawings

Other features and effects of the present invention will become apparent from the following detailed description of the embodiments with reference to the accompanying drawings, in which:

fig. 1 is a cross-sectional view of elastic wave device 1 according to a first embodiment.

Fig. 2 is a schematic diagram of the structure of the device chip 5 (Tx).

Fig. 3 is a schematic plan view of the elastic wave module 52 as a surface acoustic wave resonator.

Fig. 4 is a schematic cross-sectional view of elastic wave module 52 being a piezoelectric thin film resonator.

Fig. 5 is a schematic view of the isolation characteristics of the first embodiment and the comparative example.

Fig. 6 is a schematic diagram of the pass characteristics of the duplexers of the first embodiment and the comparative example.

Fig. 7 is a schematic structural diagram of the device chip 105 in the second embodiment.

Fig. 8 is a cross-sectional view of a module 100 in a third embodiment of the invention.

Detailed Description

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

(first embodiment)

Fig. 1 is a cross-sectional view of elastic wave device 1 according to a first embodiment.

As shown in fig. 1, acoustic wave device 1 according to the first embodiment includes a wiring board 3 and two device chips 5 mounted on wiring board 3.

Although the first embodiment exemplifies an elastic wave device that becomes a duplexer with the device chip 5(Rx) as a reception filter and the device chip 5(Tx) as a transmission filter, the present invention is also applicable to a single-chip duplexer having one of the device chips 5 or a duplexer.

For example, a multilayer substrate made of resin or a Low Temperature Co-fired ceramic (LTCC) multilayer substrate formed of a plurality of dielectric layers may be used as the wiring substrate 3. The wiring board 3 includes a plurality of external connection terminals 31.

The device chip 5 is formed with a band pass filter through which an electric signal of a desired frequency band passes. The device chip 5(Tx) has a plurality of series resonators and a plurality of parallel resonators formed thereon, which constitute a ladder filter. In the first embodiment, the band pass filter formed on the device chip 5(Tx) is a transmission filter having a transmission band pass.

The device chip 5(Rx) is formed with a band pass filter. In the first embodiment, the band pass filter formed on the device chip 5(Rx) is a reception filter having a reception band pass.

A plurality of electrode pads 9 are formed on the wiring substrate 3. The electrode pad 9 may use, for example, copper or an alloy containing copper. Further, the thickness of the electrode pad 9 is, for example, 10 μm to 20 μm.

The encapsulating portion 17 is formed so as to cover the device chip 5. The sealing portion 17 may be formed of an insulator such as a synthetic resin, or may be made of a metal. The synthetic resin may be, for example, an epoxy resin or polyimide, but is not limited thereto. Preferably, the sealing portion 17 may be formed by using an epoxy resin and through a low temperature hardening process.

The device chip 5 is mounted on the wiring substrate 3 by flip chip bonding (flip chip bonding) technique through bumps 15.

The bump 15 may be made of gold, for example. The height of the bump 15 is, for example, 20 to 50 μm.

The electrode pads 9 are electrically connected to the device chip 5 through the bumps 15.

Next, the structure on the device chip 5(Tx) is explained. Fig. 2 is a schematic diagram of the structure of the device chip 5 (Tx).

As shown in fig. 2, the device chip 5(Tx) is formed with a plurality of acoustic wave elements 52 and a plurality of wiring patterns 54.

The elastic wave device 52 includes a plurality of series resonators S1 to S5 and a plurality of parallel resonators P1 to P4.

The wiring pattern 54 has wirings constituting an input pad In, an output pad Out, and a ground pad GND. The wiring pattern 54 is electrically connected to the acoustic wave device 52.

The input pad In is electrically connected to the external connection terminal 31, which is an input terminal of the transmission filter, through the bump 15, the electrode pad 9, and the wiring board 3.

The output pad Out is electrically connected to the external connection terminal 31, which is an output terminal of the transmission filter, through the bump 15, the electrode pad 9, and the wiring substrate 3.

The ground pad GND is electrically connected to the external connection terminal 31 serving as a ground terminal of the transmission filter through the bump 15, the electrode pad 9, and the wiring board 3.

Among the series resonators of the first embodiment, the series resonator S1 provided at the position closest to the input terminal of the transmission filter has an anti-resonance frequency equal to the highest frequency of the reception bandpass of the reception filter (not shown in fig. 2).

The capacitance value of the series resonator S1 is designed to be smaller than the average value of the capacitance values of the other series resonators S2 to S5. The anti-resonance frequency and the resonance frequency of the series resonator S1 are separated from the frequency of the transmission bandpass, and since high power is not directly applied to the series resonator, the series resonator is less likely to be damaged even if its withstand power is low as compared with other series resonators. Therefore, even though the series resonator S1 is disposed at a position closest to the input terminal, a compact design can be achieved.

The series resonator provided at a position closest to the input terminal of the transmission filter is a resonator to which an electric signal amplified by a power amplifier is first input. Therefore, in the transmission filter, the series resonator provided at the position closest to the input terminal is generally designed to have a large size in order to secure sufficient power resistance without being destroyed.

According to the first embodiment, by providing the series resonator S1 having the anti-resonance frequency equal to the highest frequency of the reception band of the reception filter at the position closest to the input terminal of the transmission filter, it is possible to improve the power resistance and to reduce the size of the entire elastic wave device.

The capacitance value of the series resonator S1 is designed to be larger than the average value of the capacitance values of the parallel resonators P1 to P4. The series resonator S1 is not directly connected to the ground pad GND through the wiring pattern 54. Therefore, heat dissipation is less likely to occur than in the parallel resonators P1 to P4.

Further, when the temperature rises due to the application of power, the frequency of the resonator shifts to the low frequency side. In view of these influences, the capacitance value of the series resonator S1 is preferably designed to be larger than the average value of the capacitance values of the parallel resonators P1 to P4.

Fig. 3 is a schematic plan view of the elastic wave module 52 as a surface acoustic wave resonator.

As shown in fig. 3, the device chip 5 is provided with an idt (inter digital transducer)52a and a reflector 52b capable of exciting a surface acoustic wave. The IDT52a has a pair of comb electrodes 52 c. The comb electrode 52c has a plurality of electrode fingers 52d and a plurality of bus bars 52e connecting the electrode fingers 52 d. The reflectors 52b are disposed on both sides of the IDT52 a.

The IDT52a and the reflector 52b are formed of an alloy of aluminum and copper, for example. The IDT52a and the reflectors 52b are thin films having a thickness of 150nm to 400nm, for example.

The IDT52a and the reflectors 52b may be made of other metals, such as titanium, palladium, silver, and other suitable metals, or alloys containing the above metals, or may be made of alloys of these metals. The IDT52a and the reflector 52b may have a multilayer metal structure in which a plurality of metal layers are laminated.

The surface acoustic wave resonator may be formed of an appropriate metal or alloy such as silver, aluminum, copper, titanium, or palladium. Alternatively, the surface acoustic wave resonator may have a multilayer metal structure in which a plurality of metal layers are stacked. The thickness of the surface acoustic wave resonator is, for example, 150nm to 400 nm.

The device chip 5 may be a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz, or a substrate made of piezoelectric ceramics. Alternatively, as described later, in the band pass filter using the piezoelectric thin film resonator, a semiconductor substrate such as silicon or an insulating substrate such as sapphire, alumina, spinel, or glass can be used.

The device chip 5 may be a substrate in which a piezoelectric substrate is bonded to a support substrate. The support substrate may be, for example, sapphire, alumina, spinel, crystal, glass, or a silicon substrate.

Fig. 4 is a schematic cross-sectional view of elastic wave module 52 being a piezoelectric thin film resonator.

As shown in fig. 4, a chip substrate 60 as the device chip 5 is provided with a piezoelectric film 62. The piezoelectric film 62 is sandwiched by a lower electrode 64 and an upper electrode 66. 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 an elastic wave in a thickness longitudinal vibration mode in the piezoelectric film 62.

The chip substrate 60 is not a piezoelectric substrate, and the chip substrate 60 may be a semiconductor substrate such as silicon, or an insulating substrate such as sapphire, alumina, spinel, or glass. The piezoelectric film 62 may be made of aluminum nitride, for example. For example, a metal such as ruthenium may be used for the lower electrode 64 and the upper electrode 66.

Referring to fig. 2, the wiring pattern 54 may be formed of, for example, a suitable metal or alloy of silver, aluminum, copper, titanium, palladium, or the like. The wiring pattern 54 may have a multilayer metal structure in which a plurality of metal layers are stacked, for example. The thickness of the wiring pattern 54 is, for example, 150nm to 400 nm.

The reception filter and the transmission filter formed on the device chip 5(Rx) form an appropriate band-pass filter by forming a plurality of elastic wave elements 52.

The band pass filter is designed to pass only an electric signal of a desired frequency band through the output pad among electric signals input from the input pad. The band-pass filter can be designed as a ladder filter or as a multi-modal filter. The band pass filter may be configured using a surface acoustic wave resonator or a piezoelectric thin film resonator.

In an alternative embodiment, at least one of the transmission filter and the reception filter is a filter using a surface acoustic wave resonator formed on a piezoelectric substrate. In an alternative embodiment, the transmission filter and the reception filter are filters using surface acoustic wave resonators, and are formed on the same piezoelectric substrate.

In the reception filter, the device chip 5(Rx) is also formed with an input pad, an output pad, and a ground pad (not shown).

The input pad of the reception filter is electrically connected to the external connection terminal 31, which is an input terminal of the reception filter, through the bump 15, the electrode pad 9, and the wiring board 3.

The output pad of the reception filter is electrically connected to the external connection terminal 31 serving as an output terminal of the reception filter through the bump 15, the electrode pad 9, and the wiring board 3.

The ground pad of the reception filter is electrically connected to the external connection terminal 31 serving as a ground terminal of the reception filter through the bump 15, the electrode pad 9, and the wiring board 3.

The electric signal input from the input terminal of the reception filter passes through the reception filter, and the electric signal having a desired frequency band is output from the external connection terminal 31 as the output terminal of the reception filter.

Fig. 5 is a schematic view of the isolation characteristics of the first embodiment and the comparative example.

As shown in fig. 5, the elastic wave device in the first embodiment is a duplexer in which the transmission bandpass is 1920MHz to 1980MHz and the reception bandpass is 2110MHz to 2170 MHz.

The waveform of the solid line illustrates the isolation characteristic of the elastic wave device of the first embodiment. The waveform of the dotted line indicates the isolation characteristic of the comparative example. In the duplexer of the comparative example, the resonance frequency of the series resonator provided at the position closest to the input terminal of the transmission filter is designed to be close to the low frequency side of the transmission band. Other conditions are the same as those of the duplexer of the first embodiment.

As shown in fig. 5, it can be seen that the isolation characteristic on the high frequency side of the reception band pass of the first embodiment is greatly improved compared to the comparative example. The waveform TxS1 in fig. 5 shows the resonance characteristic of the series resonator S1 provided at the position closest to the input terminal of the transmission filter in the first embodiment. As shown in fig. 5, the series resonator S1 has an anti-resonance frequency that is the same as the highest frequency of the receive bandpass, 2170 MHz.

Fig. 6 is a schematic diagram of the pass characteristics of the duplexers of the first embodiment and the comparative example.

The waveform of the solid line indicates the pass characteristic of the duplexer of the elastic wave device of the first embodiment. The waveform of the broken line indicates the passing characteristics of the comparative example. The duplexer of the comparative example has isolation characteristics as shown in fig. 5. Other conditions are the same as those of the duplexer of the first embodiment.

As shown in fig. 6, the first embodiment has a characteristic of the pass band in a high frequency region of more than 2170MHz, and the isolation characteristic of the first embodiment is better than that of the comparative example.

In other words, according to the present invention, it is possible to provide an elastic wave device that is smaller and has excellent isolation characteristics.

(second embodiment)

Next, a second embodiment of the present invention as another embodiment will be described.

Fig. 7 is a schematic structural diagram of the device chip 105 in the second embodiment.

As shown in fig. 7, a reception filter RxBPF and a transmission filter TxBPF are formed on one device chip 105. Thus, an elastic wave device in which a duplexer is formed on one device chip can be provided.

As shown in fig. 7, the input terminal in (rx) of the reception filter RxBPF is the same terminal as the output terminal out (tx) of the transmission filter TxBPF. As shown in fig. 7, the output terminal out (rx) of the reception filter RxBPF and the input terminal in (tx) of the transmission filter TxBPF may be disposed at positions farthest from each other on the device chip 105. The interference between the RxBPF and the TxBPF of the receiving filter can be reduced, and the characteristic of the duplexer is improved.

Since the other configurations in the second embodiment are the same as those in the first embodiment, the description thereof will be omitted.

(third embodiment)

Next, a third embodiment of the present invention as another embodiment will be described.

Fig. 8 is a cross-sectional view of a module 100 in a third embodiment of the invention.

As shown in fig. 8, elastic wave device 1 is provided on a main surface of wiring board 130. For example, the duplexer described in the first or second embodiment may be used as elastic wave device 1. The wiring board 130 includes a plurality of external connection terminals 131. The external connection terminal 131 can be mounted to a main printed circuit board of a predetermined mobile communication terminal.

An inductor 111 is provided on the main surface of the wiring board 130 to achieve impedance matching. The inductor 111 may be an Integrated Passive Device (IPD). In the module 100, a plurality of electronic components including the acoustic wave device 1 are sealed by a sealing portion 117.

An integrated circuit component IC is provided inside the wiring board 130. The integrated circuit part IC comprises a switching circuit and a low noise amplifier, which are not shown in the figure.

Since the description of the other configurations overlaps with the first and second embodiments, the description thereof is omitted.

According to the embodiments of the present invention described above, it is possible to provide an elastic wave device using a multi-mode resonator that is more rectangular, has low loss, and has excellent passband characteristics, and a module including the elastic wave device.

It should be noted that, of course, the present invention is not limited to the above-mentioned embodiments, and includes all embodiments capable of achieving the objects of the present invention.

Furthermore, while at least one embodiment has been described above, it is to be understood that various changes, modifications, or 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 is to be understood that the aspects of the method or apparatus described herein are not limited in their application to the details of construction and the arrangements of the components set forth in the above description or illustrated in the drawings.

The methods and apparatus may be practiced in other embodiments or with other embodiments. The examples are given by way of illustration only and not by way of limitation.

Furthermore, the descriptions and words used herein are for the purpose of illustration only and are not intended to be limiting. The use of "including," "comprising," "having," "containing," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of the term "or any other term in the description using the term" or "may be interpreted to mean one, more than one, or all of the recited term. Any terms of front, rear, left, right, top, bottom, up, down, longitudinal and lateral are used for convenience of description, and do not limit the position and spatial arrangement of any constituent element of the present invention. Accordingly, the foregoing description and drawings are by way of example only.

Claims (10)

1. An elastic wave device characterized by: the elastic wave device includes a transmission filter having a transmission band pass, and a reception filter having a reception band pass, the transmission filter including a plurality of series resonators and a plurality of parallel resonators, at least one of the series resonators having an anti-resonance frequency that is the same as the highest frequency of the reception band pass.

2. The elastic wave device according to claim 1, wherein: among the series resonators, the series resonator having the same anti-resonance frequency as the highest frequency of the reception bandpass is provided at a position closest to the input terminal of the transmission filter.

3. The elastic wave device according to claim 1, wherein: the series resonator having the same anti-resonance frequency as the highest frequency of the reception bandpass has a capacitance value smaller than an average value of capacitance values of the other series resonators.

4. The elastic wave device according to claim 1, wherein: the series resonator having the same anti-resonance frequency as the highest frequency of the reception bandpass has a capacitance value larger than the average value of the capacitance values of the parallel resonators.

5. The elastic wave device according to claim 1, wherein: at least one of the transmission filter and the reception filter is a filter using a piezoelectric thin film resonator.

6. The elastic wave device according to claim 1, wherein: at least one of the transmission filter and the reception filter is a filter using a surface acoustic wave resonator formed on a piezoelectric substrate.

7. The elastic wave device according to claim 1, wherein: the transmission filter and the reception filter are filters using surface acoustic wave resonators, and are formed on the same piezoelectric substrate.

8. The elastic wave device according to claim 6 or 7, wherein: the piezoelectric substrate is bonded to a substrate made of sapphire, silicon, alumina, spinel, crystal, or glass.

9. The elastic wave device according to claim 5, wherein: the filter of the piezoelectric thin film resonator comprises a chip substrate, a piezoelectric film arranged on the chip substrate, a lower electrode and an upper electrode, wherein the piezoelectric film is sandwiched between the lower electrode and the upper electrode, a gap is formed between the lower electrode and the chip substrate, and the lower electrode and the upper electrode excite an elastic wave in a thickness longitudinal vibration mode in the piezoelectric film.

10. A module comprising the elastic wave device according to any one of claims 1 to 9.

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