Elastic wave device and module including the same

Abstract

An elastic wave device includes a transmitting filter having a transmitting bandpass and a receiving filter having a receiving bandpass, the transmitting filter including a plurality of series resonators and a plurality of parallel resonators, at least one of the series resonators having a same anti-resonance frequency as a highest frequency of the receiving bandpass. Thereby, an elastic wave device of a smaller size and excellent isolation characteristics, and a module including the elastic wave device are provided.

Description

Technical Field

[0001] The present invention relates to an elastic wave device and a module comprising the elastic wave device. Background Technology

[0002] In recent years, with technological advancements, smartphones and other mobile communication terminals have become significantly smaller and lighter. For filters used in these mobile communication terminals, miniaturized elastic wave devices are employed. Furthermore, the demand for communication systems capable of simultaneous reception and transmission, such as duplexers, has increased dramatically in mobile communication systems.

[0003] Based on the above, the requirements for the specifications of elastic wave devices such as duplexers have become more stringent. In other words, it is necessary to have elastic wave devices such as duplexers that are smaller than existing ones and have excellent isolation characteristics.

[0004] Patent document 1 (Japanese Patent Application Publication No. 2014-120841) illustrates an elastic wave device comprising multiple filters, wherein the elastic wave device is provided with additional circuitry to improve isolation characteristics. Summary of the Invention

[0005] The purpose of this invention is to provide a smaller elastic wave device with excellent isolation characteristics.

[0006] An elastic wave device includes a transmit filter having a transmit bandpass and a receive filter having a receive bandpass. The transmit filter includes 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 receive bandpass.

[0007] In one embodiment of the invention, the series resonator, having an anti-resonance frequency that is the same as the highest frequency of the receiving bandpass, is positioned closest to the input terminal of the transmitting filter.

[0008] In one embodiment of the invention, the series resonator having an anti-resonance frequency that is the same as the highest frequency of the receiving bandpass has a capacitance value that is smaller than the average capacitance value of the other series resonators.

[0009] In one embodiment of the invention, the series resonator having an anti-resonance frequency that is the same as the highest frequency of the receiving bandpass has a capacitance value that is larger than the average capacitance value of the parallel resonator.

[0010] In one embodiment of the invention, at least one of the transmitting filter and the receiving filter is a filter using a piezoelectric thin film resonator.

[0011] In one embodiment of the invention, at least one of the transmitting filter and the receiving filter is a filter using an elastic surface wave resonator formed on a piezoelectric substrate.

[0012] In one embodiment of the present invention, the transmitting filter and the receiving filter are filters using elastic surface wave resonators and are formed on the same piezoelectric substrate.

[0013] In one embodiment of the invention, the piezoelectric substrate is bonded to a substrate formed of sapphire, silicon, alumina, spinel, crystal, or glass.

[0014] In one embodiment of the present invention, the filter of the piezoelectric thin film resonator has a chip substrate, a piezoelectric film disposed on the chip substrate, a lower electrode, and an upper electrode. The piezoelectric film is sandwiched between the lower electrode and the upper electrode, and a gap is formed between the lower electrode and the chip substrate. The lower electrode and the upper electrode excite elastic waves in the piezoelectric film in a thickness longitudinal vibration mode.

[0015] One embodiment of the present invention includes a module comprising the elastic wave device.

[0016] The beneficial effects of the present invention are as follows: According to the present invention, a smaller elastic wave device with excellent isolation characteristics can be provided. Attached Figure Description

[0017] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein:

[0018] Figure 1 This is a cross-sectional view of the elastic wave device 1 of the first embodiment.

[0019] Figure 2 This is a schematic diagram of the structure of device chip 5 (Tx).

[0020] Figure 3 This is a schematic top view of the elastic wave component 52 as an elastic surface wave resonator.

[0021] Figure 4 This is a schematic cross-sectional view of the elastic wave component 52, which is a piezoelectric thin film resonator.

[0022] Figure 5 This is a schematic diagram illustrating the isolation characteristics of the first embodiment and the comparative example.

[0023] Figure 6 This is a schematic diagram of the throughput characteristics of the duplexer in the first embodiment and the comparative example.

[0024] Figure 7 This is a schematic diagram of the device chip 105 in the second embodiment.

[0025] Figure 8 This is a cross-sectional view of module 100 in the third embodiment of the present invention. Detailed Implementation

[0026] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0027] (First Embodiment)

[0028] Figure 1 This is a cross-sectional view of the elastic wave device 1 of the first embodiment.

[0029] like Figure 1 As shown, the elastic wave device 1 of the first embodiment includes a wiring substrate 3 and two device chips 5 mounted on the wiring substrate 3.

[0030] Although the first embodiment exemplifies an elastic wave device that uses device chip 5 (Rx) as a receiving filter and device chip 5 (Tx) as a transmitting filter to form a duplexer, the present invention is also applicable to a single-chip duplexer having one of the device chips 5, or a double duplexer.

[0031] The wiring substrate 3 may be, for example, a multilayer substrate composed of resin, or a low-temperature co-fired ceramic (LTCC) multilayer substrate formed of several dielectric layers. Furthermore, the wiring substrate 3 includes several external connection terminals 31.

[0032] The device chip 5 has a bandpass filter formed on it, allowing electrical signals in the desired frequency band to pass through. The device chip 5 (Tx) also has multiple series resonators and multiple parallel resonators forming a trapezoidal filter. In the first embodiment, the bandpass filter formed on the device chip 5 (Tx) is a transmit filter with a transmit bandpass.

[0033] A bandpass filter is formed on the device chip 5 (Rx). In the first embodiment, the bandpass filter formed on the device chip 5 (Rx) is a receiving filter with a receiving bandpass.

[0034] A plurality of electrode pads 9 are formed on the wiring substrate 3. The electrode pads 9 may be made of copper or a copper-containing alloy, for example. Furthermore, the thickness of the electrode pads 9 is, for example, between 10 μm and 20 μm.

[0035] The encapsulation portion 17 is formed to cover the device chip 5. The encapsulation portion 17 may be formed of an insulator such as a synthetic resin, or a metal may be used. The synthetic resin may be, for example, epoxy resin or polyimide, but is not limited to these. Preferably, the encapsulation portion 17 may be made of epoxy resin and formed by a low-temperature curing process.

[0036] The device chip 5 is mounted on the wiring substrate 3 via bumps 15 using flip chip bonding technology.

[0037] The bump 15 can be made of gold, for example. The height of the bump 15 is, for example, between 20 μm and 50 μm.

[0038] The electrode pad 9 is electrically connected to the device chip 5 via the bump 15.

[0039] Next, the structure on the device chip 5 (Tx) will be described. Figure 2 This is a schematic diagram of the structure of the device chip 5 (Tx).

[0040] like Figure 2 As shown, the device chip 5 (Tx) has multiple elastic wave components 52 and multiple wiring patterns 54.

[0041] The elastic wave assembly 52 includes multiple series resonators S1 to S5 and multiple parallel resonators P1 to P4.

[0042] The wiring pattern 54 has wiring that forms an input pad In, an output pad Out, and a ground pad GND. Furthermore, the wiring pattern 54 is electrically connected to the elastic wave assembly 52.

[0043] The input pad In is electrically connected to the external connection terminal 31, which serves as the input terminal of the transmitting filter, via the bump 15, the electrode pad 9, and the wiring board 3.

[0044] The output pad Out is electrically connected to the external connection terminal 31, which serves as the output terminal of the transmitting filter, via the bump 15, the electrode pad 9, and the wiring board 3.

[0045] The grounding pad GND is electrically connected to the external connection terminal 31, which serves as the grounding terminal of the transmitting filter, via the bump 15, the electrode pad 9, and the wiring board 3.

[0046] In the series resonator of the first embodiment, the series resonator S1, located closest to the input terminal of the transmitting filter, has a connection with the receiving filter ( Figure 2The highest frequency of the receiving bandpass (not shown in the image) is the same as the anti-resonance frequency.

[0047] Furthermore, the capacitance value of the series resonator S1 is designed to be smaller than the average capacitance value of the other series resonators S2 to S5. The anti-resonance frequency and resonant frequency of the series resonator S1 are separated from the transmission bandpass frequency. Since high power is not directly applied to the anti-resonance frequency and resonant frequency, it is less prone to damage than other series resonators, even with lower power tolerance. Therefore, although the series resonator S1 is located closest to the input terminal, a miniaturized design can be achieved.

[0048] The series resonator, located closest to the input terminal of the transmitting filter, is the first resonator to receive the amplified electrical signal from the power amplifier. Therefore, in general, the series resonator located closest to the input terminal in the transmitting filter is designed to be relatively large to ensure sufficient electrical resistance to prevent damage.

[0049] According to the first embodiment, by placing a series resonator S1, which has the same anti-resonance frequency as the highest frequency of the receiving bandpass of the receiving filter, at a position closest to the input terminal of the transmitting filter, the power resistance can be improved and the overall elastic wave device can be miniaturized.

[0050] Furthermore, the capacitance value of the series resonator S1 is designed to be larger than the average capacitance value of the parallel resonators P1 to P4. The series resonator S1 is not directly connected to the grounding pad GND via the wiring pattern 54. Therefore, it is less prone to heat dissipation compared to the parallel resonators P1 to P4.

[0051] Furthermore, once electricity is applied, causing the temperature to rise, the frequency of the resonator will shift towards the lower frequency side. Taking these effects into consideration, it is preferable to design the capacitance value of the series resonator S1 to be larger than the average capacitance value of the parallel resonators P1 to P4.

[0052] Figure 3 This is a schematic top view of the elastic wave component 52 as an elastic surface wave resonator.

[0053] like Figure 3 As shown, the device chip 5 is equipped with an IDT (Interdigital Transducer) 52a capable of exciting elastic surface waves and a reflector 52b. The IDT 52a has a pair of comb-shaped electrodes 52c. The comb-shaped electrodes 52c have several electrode fingers 52d and several busbars 52e connecting the electrode fingers 52d. The reflector 52b is disposed on both sides of the IDT 52a.

[0054] The IDT 52a and the reflector 52b are, for example, formed of an alloy of aluminum and copper. The IDT 52a and the reflector 52b are, for example, thin films with a thickness between 150 nm and 400 nm.

[0055] The IDT 52a and reflector 52b may also contain other metals, such as suitable metals like titanium, palladium, and silver, or alloys containing the aforementioned metals, or may be formed by alloys of these metals. Furthermore, the IDT 52a and reflector 52b may also be multilayer metal structures composed of multiple stacked metal layers.

[0056] The surface wave resonator can be formed, for example, of a suitable metal or alloy such as silver, aluminum, copper, titanium, or palladium. Alternatively, the surface wave resonator can also be a multilayer metal structure composed of multiple stacked metal layers. Furthermore, the thickness of the surface wave resonator is, for example, between 150 nm and 400 nm.

[0057] The device chip 5 can be, for example, a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz, or a substrate formed of piezoelectric ceramic. Alternatively, as described later, in the bandpass filter using a piezoelectric thin-film resonator, a semiconductor substrate such as silicon can be used, or an insulating substrate such as sapphire, alumina, spinel, or glass.

[0058] Furthermore, the device chip 5 can be a substrate in which a piezoelectric substrate is bonded to a support substrate. The support substrate can be, for example, a sapphire, alumina, spinel, crystal, glass, or silicon substrate.

[0059] Figure 4 This is a schematic cross-sectional view of the elastic wave component 52, which is a piezoelectric thin film resonator.

[0060] like Figure 4 As shown, a piezoelectric film 62 is provided on the chip substrate 60, which serves as the chip 5 of the device. The piezoelectric film 62 is sandwiched between 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 elastic waves in a thickness-longitudinal vibration mode within the piezoelectric film 62.

[0061] The chip substrate 60 is not a piezoelectric substrate. The chip substrate 60 can be, for example, a semiconductor substrate such as silicon, or an insulating substrate such as sapphire, alumina, spinel, or glass. The piezoelectric film 62 can be, for example, aluminum nitride. The lower electrode 64 and the upper electrode 66 can be, for example, metals such as ruthenium.

[0062] refer to Figure 2The wiring pattern 54 can be formed, for example, by a suitable metal or alloy such as silver, aluminum, copper, titanium, or palladium. Furthermore, the wiring pattern 54 can be, for example, a multilayer metal structure composed of multiple stacked metal layers. Moreover, the thickness of the wiring pattern 54 is, for example, between 150 nm and 400 nm.

[0063] The receiving filter and transmitting filter formed on the device chip 5(Rx) constitute a suitable bandpass filter by forming a plurality of the elastic wave components 52.

[0064] In the electrical signal input from the input pad, the bandpass filter is designed to allow only the desired frequency band of the electrical signal to pass through the output pad. The bandpass filter can be designed as a trapezoidal filter or a multimode filter. Furthermore, the bandpass filter can be constructed using a surface wave resonator or a piezoelectric thin-film resonator.

[0065] In an alternative embodiment, at least one of the transmitting filter and the receiving filter is a filter using an elastic surface wave resonator formed on a piezoelectric substrate. In another alternative embodiment, the transmitting filter and the receiving filter are filters using an elastic surface wave resonator and are formed on the same piezoelectric substrate.

[0066] In the receiving filter, the device chip 5 (Rx) also has input pads, output pads, and ground pads (not shown).

[0067] The input pad of the receiving filter is electrically connected to the external connection terminal 31, which serves as the input terminal of the receiving filter, via the bump 15, the electrode pad 9, and the wiring board 3.

[0068] The output pad of the receiving filter is electrically connected to the external connection terminal 31, which serves as the output terminal of the receiving filter, via the bump 15, the electrode pad 9, and the wiring board 3.

[0069] The grounding pad of the receiving filter is electrically connected to the external connection terminal 31, which serves as the grounding terminal of the receiving filter, via the bump 15, the electrode pad 9, and the wiring board 3.

[0070] The electrical signal input from the input terminal of the receiving filter will pass through the receiving filter, while the electrical signal with the desired frequency band will be output from the external connection terminal 31, which is the output terminal of the receiving filter.

[0071] Figure 5 This is a schematic diagram illustrating the isolation characteristics of the first embodiment and the comparative example.

[0072] like Figure 5 As shown, the elastic wave device in the first embodiment is a duplexer with a transmit passband between 1920MHz and 1980MHz and a receive passband between 2110MHz and 2170MHz.

[0073] The solid lines illustrate the isolation characteristics of the elastic wave device of the first embodiment. The dashed lines illustrate the isolation characteristics of the comparative example. In the duplexer of the comparative example, the resonant frequency of the series resonator located closest to the input terminal of the transmitting filter is designed to be close to the low-frequency side of the transmitting bandpass. Other conditions are the same as those of the duplexer of the first embodiment.

[0074] like Figure 5 As shown, compared to the comparative example, it can be seen that the isolation characteristics of the receiving bandpass high-frequency side of the first embodiment are significantly improved. Furthermore, Figure 5 The waveform TxS1 in the figure shows the resonant characteristics of the series resonator S1, which is located closest to the input terminal of the transmitting filter in the first embodiment. For example... Figure 5 As shown, the series resonator S1 has the same anti-resonance frequency as the highest frequency of the receiving bandpass, 2170MHz.

[0075] Figure 6 This is a schematic diagram of the throughput characteristics of the duplexer in the first embodiment and the comparative example.

[0076] The solid line waveform illustrates the passage characteristics of the duplexer of the elastic wave device of the first embodiment. The dashed line waveform illustrates the passage characteristics of the comparative example. The duplexer of the comparative example has the following characteristics: Figure 5 The isolation characteristics are shown. Other conditions are the same as those for the duplexer in the first embodiment.

[0077] like Figure 6 As shown, compared with the comparative example, the isolation characteristics of the first embodiment are better in the high frequency region greater than 2170MHz through the band domain characteristics.

[0078] In other words, according to the present invention, a smaller elastic wave device with excellent isolation characteristics can be provided.

[0079] (Second Embodiment)

[0080] Next, a second embodiment of the present invention as another embodiment will be described.

[0081] Figure 7 This is a schematic diagram of the structure of the device chip 105 in the second embodiment.

[0082] like Figure 7As shown, a receiving filter RxBPF and a transmitting filter TxBPF are formed on a device chip 105. This enables the provision of an elastic wave device that forms a duplexer on a single device chip.

[0083] like Figure 7 As shown, the input terminal In (Rx) of the receiving filter RxBPF and the output terminal Out (Tx) of the transmitting filter TxBPF are the same terminal. Furthermore, as... Figure 7 As shown, the output terminal Out(Rx) of the receiving filter RxBPF and the input terminal In(Tx) of the transmitting filter TxBPF can be positioned at the furthest points from each other on the device chip 105. This reduces interference between the receiving filter RxBPF and the transmitting filter TxBPF and improves the characteristics of the duplexer.

[0084] The other structures in the second embodiment are the same as those in the first embodiment, so their description is omitted.

[0085] (Third Embodiment)

[0086] Next, a third embodiment of the present invention as another embodiment will be described.

[0087] Figure 8 This is a cross-sectional view of module 100 in the third embodiment of the present invention.

[0088] like Figure 8 As shown, the elastic wave device 1 is provided on the main surface of the wiring board 130. The elastic wave device 1 can be, for example, a duplexer as described in the first embodiment or the second embodiment. The wiring board 130 includes a plurality of external connection terminals 131. The external connection terminals 131 can be mounted to the main printed circuit board of a predetermined mobile communication terminal.

[0089] 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). The module 100 seals multiple electronic components, including the elastic wave device 1, through a package 117.

[0090] The wiring board 130 contains an integrated circuit component (IC). The integrated circuit component (IC) includes a switching circuit and a low-noise amplifier, which are not shown in the figure.

[0091] Other structures are omitted from the description because they are the same as those in the first and second embodiments.

[0092] According to the above embodiments of the present invention, an elastic wave device using a more rectangular, low-loss, and highly efficient multimode resonator with excellent bandpass characteristics can be provided, as well as a module comprising the elastic wave device.

[0093] It should be noted that, of course, the present invention is not limited to the embodiments described above, but also includes all embodiments that can achieve the purpose of the present invention.

[0094] Furthermore, while at least one embodiment has been described above, it should be understood that those skilled in the art will readily conceive of various changes, modifications, or improvements.

[0095] The aforementioned changes, modifications, or improvements are also part of this disclosure and fall within the scope of this invention. It should be understood that embodiments of the methods or apparatus described herein are not limited to the architecture and arrangement of the constituent components described above or illustrated in the accompanying drawings.

[0096] The method and apparatus can be installed or implemented in other embodiments. The embodiments described are for illustrative purposes only and are not intended to be limiting.

[0097] Furthermore, the descriptions and terms used herein are for illustrative purposes only and are not intended to be limiting. The use of "comprising," "possessing," "having," "including," and variations thereof means to include the items listed below, their equivalents, and additional items. The term "or," or any term used in a description with "or," can be interpreted as meaning one, more than one, or all of the descriptive terms. The terms front, back, left, right, top, bottom, upper, lower, and vertical / horizontal are used for convenience of description and do not limit the position or spatial arrangement of any constituent component in this invention. Therefore, the above description and accompanying drawings are merely illustrative.

Claims

1. An elastic wave device, characterized in that: The elastic wave device includes a transmitting filter with a transmitting bandpass and a receiving filter with a receiving bandpass. The transmitting filter includes a plurality of series resonators and a plurality of parallel resonators. The series resonator, located closest to the input terminal of the transmitting filter, has an anti-resonance frequency that is the same as the highest frequency of the receiving bandpass, a capacitance value that is smaller than the average capacitance value of the other series resonators, and a capacitance value that is larger than the average capacitance value of the parallel resonators.

2. The elastic wave device according to claim 1, characterized in that: At least one of the transmitting filter and the receiving filter is a filter that uses a piezoelectric thin film resonator.

3. The elastic wave device according to claim 1, characterized in that: At least one of the transmitting filter and the receiving filter is a filter that uses an elastic surface wave resonator formed on a piezoelectric substrate.

4. The elastic wave device according to claim 1, characterized in that: The transmitting filter and the receiving filter are filters using elastic surface wave resonators and are formed on the same piezoelectric substrate.

5. The elastic wave device according to claim 3 or 4, characterized in that: The piezoelectric substrate is bonded to a substrate formed of sapphire, silicon, alumina, spinel, crystal, or glass.

6. The elastic wave device according to claim 2, characterized in that: The filter of the piezoelectric thin film resonator has a chip substrate, a piezoelectric film disposed on the chip substrate, a lower electrode, and an upper electrode. The piezoelectric film is sandwiched between the lower electrode and the upper electrode, and a gap is formed between the lower electrode and the chip substrate. The lower electrode and the upper electrode excite elastic waves in the piezoelectric film in a thickness longitudinal vibration mode.

7. A module comprising the elastic wave device according to any one of claims 1 to 6.

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