Elastic wave device and module

Abstract

The present disclosure relates to an elastic wave device and a module, the elastic wave device including a plurality of series resonators including a first series resonator having a first anti-resonant frequency and a second anti-resonant frequency, a plurality of parallel resonators including a second series resonator having a second anti-resonant frequency, and a bandpass filter allowing a predetermined frequency band signal to pass therethrough; the first anti-resonant frequency is located near the lowest frequency in the predetermined frequency band; the second anti-resonant frequency is located above the highest frequency in the predetermined frequency band. Through the elastic wave device and module, the problem that the steepness of the elastic wave device between the passing frequency band and the stop band is insufficient is solved, and the steepness of the elastic wave device between the passing frequency band and the stop band is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and particularly to an elastic wave device and a module. Background Art

[0002] With the progress of technology, devices such as smartphones represented by mobile communication terminals are becoming increasingly miniaturized and lightweight. As an elastic wave device for these mobile communication terminals, an elastic wave device with the possibility of miniaturization is adopted. In addition, as the number of communication systems that simultaneously transmit and receive signals in a mobile communication system has increased rapidly, the demand for duplexers has also been growing rapidly.

[0003] With the change of the mobile communication system, the required specifications for elastic wave devices have become more stringent. That is, it is required to have more excellent characteristics than before.

[0004] Between the passband and the stopband, a characteristic with a higher steepness is required.

[0005] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2014-160888) discloses a technique for improving the steepness of the pass characteristic on the high-frequency side of the passband. However, the elastic wave device described in Patent Document 1 has insufficient steepness between the passband and the stopband. Summary of the Invention

[0006] The present disclosure is proposed to overcome the above problems. Its purpose is to provide an elastic wave device with improved steepness between the passband and the stopband and a module including the same.

[0007] In a first aspect, an elastic wave device according to the present disclosure includes a plurality of series resonators and a plurality of parallel resonators, and includes a band-pass filter that allows signals in a predetermined frequency band to pass through. The plurality of series resonators includes a first series resonator having a first anti-resonant frequency and a second anti-resonant frequency. The first anti-resonant frequency is near the lowest frequency in the predetermined frequency band. The second anti-resonant frequency is above the highest frequency in the predetermined frequency band.

[0008] In some embodiments thereof, the first series resonator is the resonator among the plurality of series resonators to which an electrical signal is first applied.

[0009] In some embodiments thereof, the first anti-resonant frequency is within a range of 25 MHz downward from the lowest frequency of the predetermined frequency band.

[0010] In some embodiments thereof, the band-pass filter is a ladder filter; the first series resonator is one of the series resonators constituting the ladder filter after being serially divided.

[0011] In some of these embodiments, the first series resonator is the resonator among the plurality of series resonators to which an electrical signal is first applied.

[0012] In some of these embodiments, the first series resonator is a surface acoustic wave resonator having an IDT electrode, the IDT electrode including a central region having a first pitch, two non-central regions adjacent to the central region and having a second pitch, and two outer regions adjacent to the outside of the non-central regions and having a third pitch; wherein, the first pitch is less than the second pitch, and the second pitch is greater than the third pitch.

[0013] In some of these embodiments, the first series resonator has a pair of reflectors adjacent to the IDT electrode, and the pitch of the reflectors is less than the second pitch in the region closest to the IDT electrode and greater than the second pitch in the region farthest from the IDT electrode.

[0014] In some of these embodiments, the duty ratio of the central region of the IDT electrode is greater than the duty ratio of the non-central region of the IDT electrode.

[0015] In some of these embodiments, the predetermined frequency band of the band-pass filter is less than 100 MHz.

[0016] In some of these embodiments, the value obtained by dividing the difference between the highest frequency and the lowest frequency in the predetermined frequency band of the band-pass filter by the center frequency of the predetermined frequency band is 0.5% or more and 4.0% or less.

[0017] In a second aspect, the present disclosure provides a module including the surface acoustic wave device according to any one of the first aspects above.

[0018] According to the present disclosure, the attenuation characteristics of the surface acoustic wave device on the low-frequency side and the high-frequency side of the passband can be improved.

[0019] Details of one or more embodiments of the present disclosure are set forth in the following drawings and description to make other features, objects, and advantages of the present application more concise and understandable. Description of the Drawings

[0020] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The illustrative embodiments and descriptions thereof of the present application are used to explain the present application and do not constitute an improper limitation of the present application.

[0021] Figure 1 is a longitudinal sectional view of the surface acoustic wave device in Embodiment 1.

[0022] Figure 2This is an example diagram of the elastic wave element (resonator) of the elastic wave device in Embodiment 1.

[0023] Figure 3 This is an example diagram of the elastic wave device in Embodiment 1.

[0024] Figure 4 This is an anti-resonance characteristic diagram of the series resonator S1-1 of the receiving filter 30 of the elastic wave device 20 in Embodiment 1.

[0025] Figure 5 This is a pass characteristic diagram of the receiving filter 30 of the elastic wave device 20 in Embodiment 1.

[0026] Figure 6 This is a pitch modulation diagram when the series resonator S1-1 of the receiving filter 30 of the elastic wave device 20 in Embodiment 1 has an SAW resonator with IDT electrodes.

[0027] Figure 7 This is a longitudinal sectional view of the elastic wave device applied to the module in Embodiment 1.

[0028] In the figure: 20, elastic wave device; 23, wiring substrate; 24, external connection terminal; 25, device chip; 26, electrode pad; 27, bump; 28, sealing portion; 30, receiving filter; 52, elastic wave element; 52a, IDT electrode; 52b, reflector; 52c, comb-shaped electrode; 52d, electrode finger; 52e, bus bar; IN, input pad; OUT, output pad; GND, ground pad; 100, module; 130, wiring substrate; 131, external connection terminal; IC, integrated circuit component; 111, inductor; 117, package portion. Detailed Embodiment

[0029] To more clearly understand the purpose, technical solution, and advantages of the present application, the present application will be described and explained below with reference to the accompanying drawings and embodiments.

[0030] The embodiments will be described below with reference to the drawings. In each figure, the same or corresponding parts are labeled with the same reference numerals. For repeated descriptions, appropriate simplifications or omissions will be made.

[0031] Embodiment 1 Figure 1 This is a longitudinal sectional view of the elastic wave device in Embodiment 1.

[0032] As Figure 1 shown, the elastic wave device 20 includes a wiring substrate 23, an external connection terminal 24, a device chip 25, an electrode pad 26, a bump 27, and a sealing portion 28.

[0033] For example, the wiring substrate 23 is a multilayer substrate made of resin. For example, the wiring substrate 23 is a Low Temperature Co-fired Ceramics (LTCC) multilayer substrate composed of a plurality of dielectric layers.

[0034] A plurality of external connection terminals 24 are formed on the lower surface of the wiring substrate 23.

[0035] Electrode pads 26 are formed on the main surface of the wiring substrate 23. For example, the electrode pads 26 are made of copper or a copper-containing alloy. For example, the thickness of the electrode pads 26 is 10 μm to 20 μm.

[0036] Bumps 27 are formed on the upper surface of each electrode pad 26. For example, the bumps 27 are gold bumps. For example, the height of the bumps 27 is 10 μm to 50 μm.

[0037] A gap 29 is formed between the wiring substrate 23 and the device chip 25.

[0038] The device chip 25 is mounted on the wiring substrate 23 in a flip-chip bonding manner through the bumps 27. The device chip 25 is electrically connected to a plurality of electrode pads 26 through a plurality of bumps 27.

[0039] The device chip 25 is, for example, a surface acoustic wave device chip. The device chip 25 includes a piezoelectric substrate formed of a piezoelectric material. The piezoelectric substrate is a substrate formed of a piezoelectric single crystal material such as lithium tantalate, lithium niobate, or quartz.

[0040] The thickness of the piezoelectric substrate is, for example, 100 μm to 300 μm. In another example, the piezoelectric substrate is made of a piezoelectric ceramic.

[0041] In some other embodiments, the device chip 25 is formed by bonding a piezoelectric substrate and a support substrate. The support substrate is, for example, made of sapphire, silicon, alumina, spinel, quartz, or glass. In this case, the thickness of the piezoelectric substrate is, for example, 0.3 μm to 5 μm.

[0042] Surface acoustic wave elements 52 are formed on the piezoelectric substrate. For example, a plurality of surface acoustic wave elements 52 are formed on the main surface of the device chip 25 and constitute a transmit filter or a receive filter.

[0043] In some other embodiments, a duplexer including a transmit filter and a receive filter is formed on the main surface of the device chip 25.

[0044] The transmit filter is a ladder filter and is composed of a plurality of series resonators and a plurality of parallel resonators, and is used to transmit an electrical signal in a desired frequency band.

[0045] The receive filter is also a ladder filter and is used to receive and transmit an electrical signal in a desired frequency band.

[0046] The sealing portion 28 is formed to cover the device chip 25. The constituent material of the sealing portion 28 includes insulators such as synthetic resins or metals.

[0047] When the sealing portion 28 is made of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, or the like. Preferably, the encapsulation portion 28 is formed of an epoxy resin by a low-temperature curing process. A gap 29 is formed in the region of the wiring substrate 23 facing the device chip 25.

[0048] Next, with reference to Figure 2 An example of the surface acoustic wave element 52 formed on the device chip 25 will be described. Figure 2 is an example diagram of the surface acoustic wave element (resonator) of the surface acoustic wave device in the first embodiment.

[0049] As Figure 2 shown, an IDT (Interdigital Transducer) electrode 52a and a pair of reflectors 52b are formed on the main surface of the device chip 25. The IDT electrode 52a and the pair of reflectors 52b are arranged so as to be able to excite surface acoustic waves (mainly SH waves).

[0050] For example, the IDT electrode 52a and the pair of reflectors 52b are made of an alloy of aluminum and copper. For example, the IDT electrode 52a and the pair of reflectors 52b are made of a suitable metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver, or an alloy thereof.

[0051] For example, the IDT electrode 52a and the pair of reflectors 52b are formed by laminating multilayer metal films. For example, the thickness of the IDT electrode 52a and the pair of reflectors 52b is 150 nm to 450 nm.

[0052] The IDT electrode 52a includes a pair of comb-shaped electrodes 52c. The pair of comb-shaped electrodes 52c face each other. The comb-shaped electrode 52c includes a plurality of electrode fingers 52d and bus bars 52e.

[0053] The plurality of electrode fingers 52d are aligned in the long side direction. The bus bar 52e connects the plurality of electrode fingers 52d.

[0054] One of the pair of reflectors 52b is adjacent to one side of the IDT electrode 52a. The other reflector 52b is adjacent to the other side of the IDT electrode 52a.

[0055] Next, with reference to Figure 3 An example of the band-pass filter formed on the device chip 25 will be described. Figure 3 is an example diagram of the surface acoustic wave device in the first embodiment.

[0056] As Figure 3As shown, the bandpass filter formed on the device chip 25 is the receiving filter 30. The receiving filter 30 includes an input pad IN, an output pad OUT, and a ground pad GND.

[0057] In addition, the receiving filter 30 includes series resonators S1-1, S1-2, S2, S3-1, S3-2, and S4. In addition, the receiving filter 30 further includes parallel resonators P1-1, P1-2, P1-3, P2, P3-1, and P3-2. In addition, the receiving filter 30 is a ladder filter.

[0058] The series resonator S1-1 is configured in the circuit to be closest to the input pad IN and is the resonator to which the electrical signal is first applied. The series resonators S1-1 and S1-2 are formed by serially dividing the primary series resonator S1 of the ladder filter.

[0059] The series resonators S3-1 and S3-2 are also formed by serially dividing the series resonator S3.

[0060] The parallel resonators P1-1, P1-2, and P1-3 are formed by parallely dividing the primary parallel resonator P1 of the ladder filter. Similarly, the parallel resonators P3-1 and P3-2 are formed by parallely dividing the parallel resonator P3.

[0061] Figure 4 is the anti-resonance characteristic diagram of the series resonator S1-1 of the receiving filter 30 of the surface acoustic wave device 20 in the first embodiment. The anti-resonance characteristic of the series resonator S1-1 is represented by a solid line.

[0062] In addition, as a reference example, the anti-resonance characteristic of a conventional series resonator is represented by a dashed line. The first anti-resonance frequency Fa1 of the series resonator S1-1 is 2150 MHz. The second anti-resonance frequency Fa2 of the series resonator S1-1 is 2245 MHz.

[0063] In addition, as Figure 4 shown, in the reference example, there is only one anti-resonance characteristic corresponding to the second anti-resonance frequency Fa2, and there is no anti-resonance characteristic corresponding to the first anti-resonance frequency Fa1.

[0064] The series resonator S1-1 and the series resonator S1-2 together constitute the primary series resonator S1 of the ladder filter. In other words, the series resonator S1-1 is a part of the series resonator S1 after serial division, as Figure 3 shown, is the resonator to which the electrical signal input from the input terminal IN is first applied.

[0065] Figure 5 This is the pass characteristic diagram of the receiving filter 30 of the elastic wave device 20 in Embodiment 1. The solid line represents the pass characteristic of the receiving filter 30 in Embodiment 1. The dashed line represents the pass characteristic of the filter in the reference example.

[0066] Figure 5 The first anti-resonant frequency Fa1 of the series resonator S1-1 described in [reference] is 2150 MHz, and it is set near the low-frequency side frequency in the passband 2170 MHz to 2200 MHz of the receiving filter 30 (within the range of 25 MHz downward from the lowest frequency of the passband).

[0067] The passband of the receiving filter 30 in Embodiment 1 is the satellite communication receiving band, with a range of 2170 MHz to 2200 MHz. The width of the passband is 30 MHz. In addition, the relative bandwidth is 1.37%.

[0068] The relative bandwidth here refers to the value obtained by dividing the difference between the highest frequency and the lowest frequency in the band by the center frequency of the band.

[0069] The anti-resonant frequency of the series resonator S1-1 is 2250 MHz. It can be seen that this frequency is above the highest frequency of the passband of the receiving filter 30.

[0070] By setting the first anti-resonant frequency Fa1 of the series resonator S1-1 near the frequency on the low-frequency side of the pass characteristic of the receiving filter 30 (between the lowest frequency of the passband and -25 MHz), due to the low coupling coefficient of the series resonator S1-1, the steepness can be improved on the low-frequency side of the passband characteristic formed by the first anti-resonant frequency Fa1.

[0071] By setting the first anti-resonant frequency Fa1 of the series resonator S1-1 near the frequency on the low-frequency side of the pass characteristic of the receiving filter 30 (between the lowest frequency of the passband and -25 MHz), the temperature characteristic can be improved.

[0072] More specifically, usually the left shoulder (low-frequency side) of the passband is formed by the resonance characteristic of the parallel resonator, but the absolute value of the frequency temperature coefficient of the resonance characteristic is greater than that of the anti-resonance characteristic, and the temperature characteristic is poor.

[0073] By making the absolute value of the frequency temperature coefficient of the first anti-resonant frequency Fa1 of the series resonator S1-1 smaller than its resonant frequency, and this first anti-resonant frequency Fa1 helps to form the left shoulder (low-frequency side) of the passband, the temperature characteristic of the low-frequency side of the band-pass filter can be improved.

[0074] In addition, since the first anti-resonant frequency Fa1 helps to form the left shoulder (low-frequency side) of the passband, and the second anti-resonant frequency Fa2 helps to attenuate the high-frequency side of the passband, the width of the passband is formed within the frequency difference range between the first anti-resonant frequency Fa1 and the second anti-resonant frequency Fa2. Specifically, the bandwidth of the passband where the above-described series resonator S1-1 has a remarkable effect is within 100 MHz.

[0075] Figure 6 It is a pitch modulation diagram when the series resonator S1-1 of the receiving filter 30 of the surface acoustic wave device 20 in the first embodiment 1 is a SAW resonator having an IDT electrode.

[0076] The first pitch of the central region CR of the IDT electrode is 1.753 μm. In addition, the duty ratio is 55%. The second pitch of the two adjacent regions (non-central regions) NCR on both sides of the central region CR of the IDT electrode is 1.813 μm, and the duty ratio is 50%.

[0077] The third pitch of the two adjacent regions (the said) OR outside the non-central region NCR of the IDT electrode is not fixed. However, the third pitch of the outer region OR is smaller than the second pitch of the non-central region NCR.

[0078] In addition, the duty ratio of the outer region OR is 50%. It should be noted that the duty ratio refers to the ratio of the width of the electrode fingers in one cycle. In the reference example, the pitches of the central region and the non-central region are the same.

[0079] By making the pitches of the central region and the non-central region different, two anti-resonant frequencies, namely the second anti-resonant frequency Fa2 and the first anti-resonant frequency Fa1, can be generated. In addition, the resonant frequency is located between the second anti-resonant frequency Fa2 and the first anti-resonant frequency Fa1.

[0080] In addition, the pitch modulation 52bP of the reflector is smaller than the pitch of the non-central region NCR in the region closest to the IDT electrode, and larger than the pitch of the non-central region NCR in the region farthest from the IDT electrode.

[0081] By providing the series resonator S1-1, in addition to ensuring its function as a conventional series resonator, that is, the anti-resonant characteristic at the second anti-resonant frequency Fa2 is used to ensure the attenuation characteristic of the high-frequency side of the passband, the first anti-resonant frequency Fa1 can also be set near the frequency on the low-frequency side (between the lowest frequency of the passband and 25 MHz lower), thereby improving the steepness of the low-frequency side.

[0082] In summary, through the description of the first embodiment, a surface acoustic wave device that improves the steepness between the passband and the stopband can be provided.

[0083] Embodiment 2 Figure 7 It is a longitudinal sectional view of a module applying the elastic wave device of Embodiment 1. It should be noted that, for the same or corresponding parts as those in Embodiment 1, the same reference numerals will be used, and the description of this part can be omitted.

[0084] Figure 7 In it, the module 100 includes a wiring substrate 130, a plurality of external connection terminals 131, an integrated circuit component IC, an elastic wave device 20, an inductor 111, and a sealing portion 117.

[0085] The plurality of external connection terminals 131 are formed on the lower surface of the wiring substrate 130. The plurality of external connection terminals 131 are pre-mounted on the main board of the provided mobile communication terminal. For example, the integrated circuit component IC is mounted inside the wiring substrate 130. The integrated circuit component IC includes a switching circuit and a low noise amplifier.

[0086] The elastic wave device 20 is mounted on the main surface of the wiring substrate 130.

[0087] The inductor 111 is mounted on the main surface of the wiring substrate 130. The inductor 111 is used for impedance matching. For example, the inductor 111 is an Integrated Passive Device (IPD).

[0088] The sealing portion 117 encapsulates a plurality of electronic components including the elastic wave device 20.

[0089] Through the description of Embodiment 2, the module 100 is provided with the elastic wave device 20. Therefore, a module with an improved steepness between the passband and the stopband can be provided.

[0090] Although several aspects of at least one embodiment have been described, various changes, modifications, and improvements are readily conceivable by those skilled in the art. Such changes, modifications, and improvements are intended to form a part of the present disclosure and are within the scope of the present disclosure.

[0091] It should be understood that the embodiments of the methods and apparatuses described herein are not limited to the details of the structures and arrangements of the components described in the above description or illustrated in the drawings. The methods and apparatuses can be implemented in other embodiments and can be implemented or executed in various ways.

[0092] The specific embodiments are given only as examples and are not intended to be limiting.

[0093] The terms and expressions used in the present disclosure are for illustrative purposes only and should not be regarded as limiting. As used herein, "including", "having", "containing", and variations of these words mean the items listed hereinafter and their equivalents and additional items.

[0094] References to "or" should be understood to mean that terms using "or" may refer to one, more than one, and all of the terms.

[0095] References to orientations such as front and back, left and right, top and bottom, horizontal and vertical, inside and outside, etc. are for convenience of description only. These references do not limit any position or spatial orientation of the components of the present disclosure. Therefore, the above descriptions and illustrations are only examples.

[0096] The expressions and terms used in the present invention are for illustrative purposes only and should not be construed as limiting. The use of "comprising", "having", "including", "containing" and their variants herein means including the items listed below, their equivalents and additional items.

[0097] The term "embodiment" in this application means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of this application. The phrase appears in various positions in the specification and does not necessarily mean the same embodiment, nor does it mean being independent or alternative to other embodiments and mutually exclusive. Those of ordinary skill in the art can clearly or implicitly understand that the embodiments described in this application can be combined with other embodiments without conflict.

[0098] The above-described embodiments only represent several implementation manners of this application, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of patent protection. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several deformations, corrections and improvements can be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

Claims

1. An elastic wave device, characterized in that: A plurality of series resonators and a plurality of parallel resonators are provided, and a bandpass filter is provided that allows a signal of a predetermined frequency band to pass through. The plurality of series resonators include a first series resonator having a first anti-resonance frequency and a second anti-resonance frequency; The first anti-resonance frequency is located near the lowest frequency in the predetermined frequency band; The second anti-resonance frequency is located above the highest frequency in the predetermined frequency band.

2. The elastic wave device according to claim 1, characterized in that: The first anti-resonance frequency is within a range of 25 MHz below the lowest frequency of the predetermined frequency band.

3. The elastic wave device according to claim 1, characterized in that: The first series resonator is a resonator to which an electrical signal is applied first among the plurality of series resonators.

4. The elastic wave device according to claim 1, characterized in that: The bandpass filter is a ladder filter; and the first series resonator is one of the series resonators constituting the ladder filter that are divided in series.

5. The elastic wave device according to claim 1, characterized in that: The first series resonator is an elastic surface wave resonator having an IDT electrode, wherein the IDT electrode includes a central region having a first spacing, two non-central regions adjacent to the central region and having a second spacing, and two outer regions adjacent to the outer sides of the non-central region and having a third spacing; wherein the first spacing is smaller than the second spacing, and the second spacing is larger than the third spacing.

6. The elastic wave device according to claim 5, characterized in that: The first series resonator includes a pair of reflectors adjacent to the IDT electrode, and a pitch between the reflectors is smaller than the second pitch in a region closest to the IDT electrode and is larger than the second pitch in a region farthest from the IDT electrode.

7. The elastic wave device according to claim 5, characterized in that: The duty ratio of the central region of the IDT electrode is greater than the duty ratio of the non-central region of the IDT electrode.

8. The elastic wave device according to claim 1, characterized in that: The predetermined frequency band of the bandpass filter is less than 100 MHz.

9. The elastic wave device according to claim 1, characterized in that: A value obtained by dividing a difference between a highest frequency and a lowest frequency in the predetermined frequency band of the bandpass filter by a center frequency of the predetermined frequency band is greater than or equal to 0.5% and less than or equal to 4.0%. 10 . A module comprising the elastic wave device according to claim 1 .

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