Elastic wave device

Abstract

An elastic wave device (1) comprises: a support substrate (30) that has a principal surface (30a) and a principal surface (30b); a piezoelectric layer (32) that has a principal surface (32a) that is opposite the principal surface (30b) and a principal surface (32b) that is on the reverse side from the principal surface (32a); an elastic wave resonator (21) that is provided at the principal surface (32b); a support substrate (40) that has a principal surface (40a) that is opposite the principal surface (32b); an elastic wave resonator (11) that is provided at the principal surface (40a); a frame body (70) that is provided between the principal surface (32b) and the principal surface (40a) so as to surround the elastic wave resonator (11) and the elastic wave resonator (21); and a through electrode (81) that passes through the support substrate (30). The elastic wave resonator (21) includes an IDT electrode (60) that is provided at the principal surface (32b), and when the thickness of the piezoelectric layer (32) is d and the electrode finger pitch of the IDT electrode (60) is p, d / p is no more than 0.5. The elastic wave resonator (11) includes a planar electrode (66), a piezoelectric layer (67), and a planar electrode (68).

Description

Elastic Wave Device

[0001] The present invention relates to an acoustic wave device.

[0002] Patent Document 1 discloses a piezoelectric device including a first piezoelectric substrate, a second piezoelectric substrate, a SAW resonator disposed on the first piezoelectric substrate side of the space between the first and second piezoelectric substrates, a BAW resonator disposed on the second piezoelectric substrate side of the space, and an external electrode penetrating the second piezoelectric substrate, which is said to enable the realization of a small-sized acoustic wave device.

[0003] WO 2006 / 008940

[0004] However, in the piezoelectric device (acoustic wave device) disclosed in Patent Document 1, the first piezoelectric substrate and the second piezoelectric substrate expand at high temperatures. Because the acoustic wave propagation direction of the BAW resonator intersects with the expansion direction parallel to the substrate surface, the resonance characteristics of the BAW resonator are less susceptible to thermal stress. In contrast, when a laterally excited film bulk acoustic resonator (XBAR) including an interdigital transducer (IDT) electrode is disposed on the first piezoelectric substrate, the IDT electrode is formed parallel to the expansion direction, and the resonance characteristics of the XBAR are likely to deteriorate due to the thermal stress. In other words, the performance degradation of the XBAR disposed on the first piezoelectric substrate at high temperatures degrades the performance of the piezoelectric device (acoustic wave device).

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a small-sized acoustic wave device in which deterioration of characteristics due to heat is suppressed.

[0006] In order to achieve the above object, an elastic wave device according to one aspect of the present invention includes a first support substrate having first and second main surfaces opposing each other, a first piezoelectric layer having a third main surface facing the second main surface and a fourth main surface facing the third main surface, a first elastic wave resonator arranged on the fourth main surface, a second support substrate having a fifth main surface facing the fourth main surface across a space, a second elastic wave resonator arranged on the fifth main surface, and a second elastic wave resonator arranged between the fourth and fifth main surfaces, the first elastic wave resonator and the second elastic wave resonator being coplanar when the fourth and fifth main surfaces are viewed in plan. The acoustic wave resonator includes a frame body arranged to surround the pendulum, and a through electrode arranged to penetrate the first support substrate between the first and second main surfaces and connected to at least one of the first acoustic wave resonator and the second acoustic wave resonator, wherein the first acoustic wave resonator includes an IDT electrode arranged on the fourth main surface, and where d is the thickness of the first piezoelectric layer and p is the electrode finger pitch of the IDT electrode, d / p is 0.5 or less, and the second acoustic wave resonator includes a first planar electrode, a second piezoelectric layer, and a second planar electrode arranged in this order from the fifth main surface toward the fourth main surface.

[0007] According to the present invention, it is possible to provide a small-sized acoustic wave device in which deterioration of characteristics due to heat is suppressed.

[0008] FIG. 1 is a cross-sectional view of an elastic wave device according to an embodiment. FIG. 2A is a first plan view of an elastic wave device according to an embodiment. FIG. 2B is a second plan view of an elastic wave device according to an embodiment. FIG. 3A is a plan view and a cross-sectional view schematically showing a first example of a first elastic wave resonator according to an embodiment. FIG. 3B is a cross-sectional view schematically showing a second example of a first elastic wave resonator according to an embodiment. FIG. 3C is a cross-sectional view schematically showing a first example of a second elastic wave resonator according to an embodiment. FIG. 3D is a cross-sectional view schematically showing a second example of a second elastic wave resonator according to an embodiment. FIG. 4 is a cross-sectional view of an elastic wave device according to an embodiment mounted on a motherboard. FIG. 5 is a diagram illustrating an example of a circuit configuration of an elastic wave device according to an embodiment. FIG. 6 is a diagram illustrating impedance characteristics and pass characteristics of an elastic wave device according to an embodiment. FIG. 7 is a diagram illustrating impedance characteristics and pass characteristics of an elastic wave device according to a modification of an embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0010] It should be noted that the drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present invention, and are not necessarily strictly illustrated, and may differ from the actual shapes, positional relationships, and proportions. In the drawings, the same reference numerals are used to denote substantially the same components, and redundant explanations may be omitted or simplified.

[0011] Furthermore, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not only represent strict meanings, but also include substantially equivalent ranges, for example, including an error of a few percent.

[0012] In the circuit configuration of the present disclosure, "connected" includes not only direct connection by electrodes and / or wiring conductors, but also electrical connection via matching elements such as inductors and capacitors, and switch circuits. "Connected between A and B" means connected to both A and B between A and B.

[0013] In addition, in the present disclosure, the passband of an acoustic wave device or an acoustic wave filter is defined as the frequency band between two frequencies that are 3 dB higher than the minimum insertion loss value within the passband.

[0014] Furthermore, in the resonance characteristics of the elastic wave device of the present disclosure, the resonance frequency and anti-resonance frequency are derived, for example, by contacting an RF probe with two input / output electrodes of the elastic wave device when the elastic wave device is not connected to other circuit elements, and measuring the reflection characteristics (impedance characteristics) using a network analyzer or the like.

[0015] In this disclosure, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be present in any one of single crystal, polycrystalline, and amorphous states, or a mixture of these states.

[0016] In the layer configuration of the present invention, "Layer A (or component A) is disposed on the main surface C of Layer B" not only means that Layer A (or component A) is disposed in contact with the main surface C of Layer B, but also that Layer A (or component A) is disposed above main surface C without contacting main surface C (for example, Layer A (or component A) is stacked on another layer that is disposed in contact with main surface C).

[0017] (Embodiments) [1 Structure of Elastic Wave Device 1] Fig. 1 is a cross-sectional view of elastic wave device 1 according to an embodiment. Fig. 2A is a first plan view of elastic wave device 1 according to an embodiment. Fig. 2B is a second plan view of elastic wave device 1 according to an embodiment. Fig. 2A is a planar (transparent) view of main surface 32b of piezoelectric layer 32 from the positive side of the z axis. Fig. 2B is a planar (transparent) view of main surface 41a of dielectric film 41 from the positive side of the z axis. Fig. 1 is a cross-sectional view taken along line II in Figs. 2A and 2B.

[0018] As shown in Figures 1, 2A, and 2B, the elastic wave device 1 includes support substrates 30 and 40, a piezoelectric layer 32, a low acoustic velocity layer 31, a dielectric film 41, a frame body 70, support conductors 71 and 72, elastic wave resonators 11, 12, 13, 21, and 22, through electrodes 81 and 82, and external connection electrodes 83 and 84.

[0019] The support substrate 30 is an example of a first support substrate and has opposing main surfaces 30a (first main surface) and 30b (second main surface). The support substrate 30 is disposed on the main surface 32a of the piezoelectric layer 32 via a low acoustic velocity layer 31. The support substrate 30 can be made of, for example, a piezoelectric material such as aluminum nitride or quartz; a ceramic material such as alumina, sapphire, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, or sialon; a dielectric material such as aluminum oxide, silicon oxynitride, silicon oxide, DLC (diamond-like carbon), or diamond; a semiconductor material such as silicon or gallium arsenide; or a material containing any of the above materials as a main component. The spinel includes an aluminum compound containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl ２ O ４ , FeAl ２ O ４ , ZnAl ２ O ４ , MnAl ２ O ４ Examples include:

[0020] The support substrate 40 is an example of a first support substrate and has a principal surface 40a (fifth principal surface) and a principal surface 40b that face each other. The principal surface 40a faces the principal surface 32b of the piezoelectric layer 32 across a space 140. The support substrate 40 can be made of, for example, a piezoelectric material such as aluminum nitride or quartz; a ceramic material such as alumina, sapphire, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, or sialon; a dielectric material such as aluminum oxide, silicon oxynitride, silicon oxide, DLC (diamond-like carbon), or diamond; a semiconductor material such as silicon or gallium arsenide; or a material primarily composed of any of the above materials. The spinel includes an aluminum compound containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl ２ O ４ , FeAl ２ O ４ , ZnAl ２ O４ , MnAl ２ O ４ Examples include:

[0021] The piezoelectric layer 32 is an example of a first piezoelectric layer and has opposing principal surfaces 32a (third principal surface) and 32b (fourth principal surface). The principal surface 32b faces the principal surface 40a across a space 140, and the principal surfaces 32a and 32b face each other. In the elastic wave device 1 according to this embodiment, when the thickness (in the z-axis direction) of the piezoelectric layer 32 is d and the electrode finger pitch of the IDT electrode 60 included in the elastic wave resonator 21 is p, the normalized film thickness d / p of the piezoelectric layer 32 is 0.5 or less. The piezoelectric layer 32 includes, for example, any one of lithium tantalate, lithium niobate, quartz crystal, zinc oxide (ZnO), and aluminum nitride (AlN).

[0022] Furthermore, in a region where the main surface 32a overlaps with the IDT electrode 60 included in the acoustic wave resonator 21 and the IDT electrode 60 included in the acoustic wave resonator 22 when viewed in a plane, a gap 160 is provided between the main surface 32a and the support substrate 30.

[0023] Since the normalized thickness d / p of piezoelectric layer 32 is 0.5 or less and gap 160 is provided, acoustic wave resonators 21 and 22 constitute an XBAR type resonator (hereinafter referred to as XBAR).

[0024] The low acoustic velocity layer 31 is an example of a first intermediate layer, and is disposed between the piezoelectric layer 32 and the support substrate 30. The layer has a bulk wave acoustic velocity lower than that of the bulk wave propagating through the piezoelectric layer 32. The low acoustic velocity layer 31 can be made of a dielectric material such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound of silicon oxide with fluorine, carbon, or boron added, or a material containing any of the above materials as a main component. The low acoustic velocity layer 31 may be omitted.

[0025] The elastic wave device 1 may further include a high acoustic velocity layer (second intermediate layer) disposed between the support substrate 30 and the low acoustic velocity layer 31 and having a bulk wave acoustic velocity higher than that of the low acoustic velocity layer 31.

[0026] Each of the acoustic wave resonators 21 and 22 is an example of a first acoustic wave resonator, and is configured with a piezoelectric layer 32 and an IDT electrode 60 disposed on a main surface 32b.

[0027] 3A is a plan view and a cross-sectional view schematically illustrating a first example of elastic wave resonators 21 and 22 according to an embodiment. The drawings illustrate the basic structures of elastic wave resonators 21 and 22 that constitute elastic wave device 1. Note that elastic wave resonator 10A shown in FIG. 3A is intended to illustrate a typical structure of elastic wave resonators 21 and 22, and the number and length of electrode fingers that constitute the electrodes are not limited to this.

[0028] As shown in FIG. 3A , the acoustic wave resonator 10A includes a support substrate 30, a low acoustic velocity layer 31, a piezoelectric layer 32, and an IDT electrode 60. The IDT electrode 60 is disposed on the piezoelectric layer 32 and includes a pair of opposing comb electrodes 60a and 60b. The comb electrode 60a includes a plurality of parallel electrode fingers 61a and a busbar electrode 62a connecting one ends of the electrode fingers 61a. The comb electrode 60b includes a plurality of parallel electrode fingers 61b and a busbar electrode 62b connecting one ends of the electrode fingers 61b. The electrode fingers 61a and 61b are formed in a direction perpendicular to the acoustic wave propagation direction (X-axis direction). The busbar electrodes 62a and 62b are arranged opposite each other with the electrode fingers 61a and 61b interposed therebetween. The acoustic wave resonator 20A may have reflectors on both ends of the IDT electrode 60 in the acoustic wave propagation direction (X-axis direction).

[0029] As shown in FIG. 3A (b), the IDT electrode 60 has a laminated structure including, for example, an adhesion layer 540 and a main electrode layer 542. The adhesion layer 540 is a layer for improving adhesion between the piezoelectric substrate 50 and the main electrode layer 542 and is made of, for example, Ti. The main electrode layer 542 is made of, for example, Al containing 1% Cu. The protective layer 55 is formed to cover the comb-shaped electrodes 60a and 60b. The protective layer 55 is a layer for protecting the main electrode layer 542 from the external environment, adjusting the frequency-temperature characteristics, and improving moisture resistance. For example, it is a dielectric film primarily composed of silicon dioxide. Note that the materials constituting the adhesion layer 540, the main electrode layer 542, and the protective layer 55 are not limited to those described above. Furthermore, the IDT electrode 60 does not necessarily have to have the laminated structure described above. The IDT electrode 60 may be made of a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a laminate of multiple layers made of the above metals or alloys. The protective layer 55 may not be formed.

[0030] 3A(c), the support substrate 30, the low acoustic velocity layer 31, and the piezoelectric layer 32 are laminated in this order. When the piezoelectric layer 32 is viewed from above, a gap 160 is provided between the main surface 32a and the support substrate 30 in the region overlapping with the IDT electrode 60.

[0031] The piezoelectric layer 32 is, for example, a θ° Y-cut X-propagation LiTaO ３ Piezoelectric single crystal or piezoelectric ceramic (lithium tantalate single crystal or ceramic cut along a plane normal to an axis rotated θ° from the Y axis around the X axis, where elastic waves propagate in the X-axis direction) or θ° Y-cut X-propagation LiNbO ３ The piezoelectric layer 32 is made of a piezoelectric single crystal or piezoelectric ceramics. The material and cut angle θ of the piezoelectric single crystal used for the piezoelectric layer 32 are appropriately selected depending on the required specifications of each filter.

[0032] The support substrate 30 is a substrate that supports the low acoustic velocity layer 31 , the piezoelectric layer 32 and the IDT electrode 60 .

[0033] The above-described layered structure of support substrate 30, low acoustic velocity layer 31, and piezoelectric layer 32 can significantly increase the Q value at the resonant frequency and anti-resonant frequency compared to a conventional structure using a single piezoelectric substrate. In other words, acoustic wave resonator 10A with a high Q value can be configured, and therefore an acoustic wave filter with low insertion loss can be configured using acoustic wave resonator 10A.

[0034] Here, the electrode parameters of the IDT electrode 60 constituting the acoustic wave resonator 10A will be described.

[0035] The wavelength λ of the acoustic wave resonator 10A is determined by the repetition period of the electrode fingers 61a or 61b constituting the IDT electrode 60 shown in FIG. 3A (b). The electrode finger pitch p is half the wavelength λ and is defined as (L+S), where L is the line width of the electrode fingers 61a and 61b constituting the interdigital electrodes 60a and 60b, respectively, and S is the space width between adjacent electrode fingers 61a and 61b. The electrode finger duty D of the IDT electrode 60 is the line width occupancy rate of the electrode fingers 61a and 61b, which is the ratio of the line width to the sum of the line width L1 and the space width S1, and is defined as L1 / (L1+S1). If the spacing between adjacent electrode fingers in the IDT electrode 60 is not constant, the electrode finger pitch p of the IDT electrode 60 is determined by the average electrode finger pitch p of the IDT electrode 60. ＡＶＥ The average electrode finger pitch p of the IDT electrode 60 is defined as ＡＶＥ is defined as Di / (Ni-1), where Ni is the total number of electrode fingers 61a, 61b included in the IDT electrode 60, and Di is the center-to-center distance between the electrode finger located at one end and the electrode finger located at the other end of the IDT electrode 60 in the acoustic wave propagation direction. ＡＶＥ The average electrode finger duty D of the IDT electrode 60 is defined as ＡＶＥ The total number of electrode fingers 61a and 61b included in the IDT electrode 60 is Ni, and the total line width obtained by adding the line width L1 of (Ni-1) electrode fingers is L1. ＡＬＬThe total space width obtained by adding up the (Ni-1) space widths S1 included in the IDT electrode 60 is S1 ＡＬＬ In this case, L1 ＡＬＬ / (L1 ＡＬＬ +S1 ＡＬＬ ) is defined as

[0036] The electrode finger pitch p of the comb-shaped electrodes of the IDT electrode 60 can be measured by using a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), or a transmission electron microscope (TEM) to view the main surface of the substrate on which the comb-shaped electrodes of the IDT electrode 60 are formed in a plan view and / or a cross-section perpendicular to the extension direction of the electrode fingers, and measuring the line width L and space width S.

[0037] Elastic wave resonator 10A constitutes an XBAR due to piezoelectric layer 32 having a normalized thickness d / p of 0.5 or less and having a membrane structure with air gap 160. When piezoelectric layer 32 has a normalized thickness d / p of 0.5 or less, elastic wave resonator 10A can have a fractional bandwidth of 5% or more, resulting in a resonator with a high electromechanical coupling coefficient.

[0038] It is more desirable that the normalized thickness d / p of the piezoelectric layer 32 be 0.24 or less, which allows the relative bandwidth of the elastic wave resonator 10A to be 7% or more.

[0039] It is desirable that the electrode finger duty D of the IDT electrode 60 and the normalized film thickness d / p satisfy the relationship of Equation 1.

[0040] D≦1.75(d / p)+0.075 (Formula 1)

[0041] This effectively reduces the spurious response of the higher-order mode of the XBAR. Specifically, the fractional bandwidth of the XBAR (the value obtained by dividing the difference frequency between the antiresonance frequency and the resonant frequency by the average frequency of the antiresonance frequency and the resonant frequency) can be set to 17% or less, thereby preventing the spurious response of the higher-order mode from being included in the passband.

[0042] It is more desirable that the electrode finger duty D of the IDT electrode 60 and the normalized film thickness d / p satisfy the relationship of Equation 2.

[0043] D≦1.75(d / p)+0.05 (Formula 2)

[0044] This ensures that the fractional bandwidth of the XBAR is 17% or less, and prevents spurious signals of higher modes from being included in the passband.

[0045] Furthermore, it is desirable that the piezoelectric layer 32 is made of lithium niobate or lithium tantalate, and that the Euler angles (θ1, θ2, θ3) of the lithium niobate or lithium tantalate constituting the piezoelectric layer 32 are within the range of the following formula 3, formula 4, formula 5 or formula 6.

[0046] −10°≦θ1≦10°, and 0°≦θ2≦20° (Equation 3)

[0047] -10°≦θ1≦10°, and 20°≦θ2≦80°, and 0°≦θ3≦60° (1-(θ2-50) ２ / 900) １／２ ) (Formula 4)

[0048] -10°≦θ1≦10°, and 20°≦θ2≦80°, and [180°-60°(1-(θ2-50) ２ / 900) １／２ )]≦θ3≦180° (Formula 5)

[0049] -10°≦θ1≦10°, and [180°-30°(1-(θ3-90) ２ / 8100) １／２ )]≦θ2≦180° (Formula 6)

[0050] By defining the Euler angles of piezoelectric layer 32 made of lithium niobate or lithium tantalate as described above, the fractional bandwidth of elastic wave resonator 10A can be set to 5% or more.

[0051] 3B is a plan view and a cross-sectional view schematically illustrating a second example of elastic wave resonators 21 and 22 according to an embodiment. Note that elastic wave resonator 10B shown in FIG. 3B is intended to illustrate a typical structure of elastic wave resonators 21 and 22, and the number and length of electrode fingers constituting the electrodes are not limited to this example.

[0052] 3B , the elastic wave resonator 10B includes a support substrate 30, a piezoelectric layer 32, a low acoustic impedance layer 161, a high acoustic impedance layer 162, and an IDT electrode 60. The elastic wave resonator 10B of the second example differs from the elastic wave resonator 10A of the first example in that an energy trapping layer including the low acoustic impedance layer 161 and the high acoustic impedance layer 162 is disposed in place of the gap 160. The following description of the elastic wave resonator 10B of the second example will focus on the differences in configuration from the elastic wave resonator 10A of the first example. The structures of the IDT electrode 60 and the piezoelectric layer 32 are the same as those of the IDT electrode 60 and the piezoelectric layer 32 of the first example.

[0053] An energy trapping layer is disposed between the piezoelectric layer 32 and the support substrate 30, and has a configuration in which low acoustic impedance layers 161 with a relatively low acoustic impedance and high acoustic impedance layers 162 with a relatively high acoustic impedance are alternately stacked. The energy trapping layer may have a stacked structure of a low acoustic speed film and a high acoustic speed film. The low acoustic speed film is a film in which the acoustic velocity of bulk waves in the low acoustic speed film is slower than the acoustic velocity of bulk acoustic waves propagating through the piezoelectric layer 32. The high acoustic speed film is a film in which the acoustic velocity of bulk waves in the high acoustic speed film is faster than the acoustic velocity of acoustic waves propagating through the piezoelectric layer 32.

[0054] Since the normalized thickness d / p of the piezoelectric layer 32 is 0.5 or less and an energy trapping layer is provided, the elastic wave resonator 10B constitutes an XBAR.

[0055] Returning to FIGS. 1, 2A, and 2B, acoustic wave resonators 11 to 13 will be described.

[0056] Each of the acoustic wave resonators 11 to 13 is an example of a second acoustic wave resonator, and is disposed on the main surface 40a of the support substrate 40 via a dielectric film 41. Note that the dielectric film 41 does not necessarily have to be formed on the main surface 40a.

[0057] Fig. 3C is a cross-sectional view schematically illustrating a first example of elastic wave resonators 11 to 13 according to an embodiment. Fig. 3D is a cross-sectional view schematically illustrating a second example of elastic wave resonators 11 to 13 according to an embodiment. Figs. 3C and 3D illustrate the basic structures of elastic wave resonators 11 to 13 constituting elastic wave device 1. Note that elastic wave resonators 20A and 20B shown in Figs. 3C and 3D are intended to illustrate typical structures of elastic wave resonators 11 to 13, and the lengths and widths of the planar electrodes and piezoelectric layers are not limited thereto.

[0058] As shown in FIG. 3C , the acoustic wave resonator 20A includes planar electrodes 66 and 68 and a piezoelectric layer 67. The planar electrode 66 is an example of a first planar electrode, the planar electrode 68 is an example of a second planar electrode, and the piezoelectric layer 67 is an example of a second piezoelectric layer. The planar electrode 66, the piezoelectric layer 67, and the planar electrode 68 are arranged in this order on a support substrate 65 to form a laminate. The support substrate 65 corresponds to the support substrate 40 shown in FIG. 1 and is configured to be out of contact with the central region of the planar electrode 66. In FIG. 3C , a space 150 is formed in the support substrate 65 to achieve a non-contact configuration between the support substrate 65 and the central region of the planar electrode 66. Note that, as a configuration to achieve a non-contact configuration between the support substrate 65 and the central region of the planar electrode 66, a space 150 may be formed between the laminate and the main surface 40 a of the support substrate 40 without forming a space in the support substrate 40, as shown in FIG. 1 .

[0059] The piezoelectric layer 67 is made of, for example, a piezoelectric single crystal such as lithium niobate or lithium tantalate. Alternatively, the piezoelectric layer 67 may be made of, for example, aluminum nitride (AlN) or ScAlN. The layer structure, material, cut angle, and thickness of the piezoelectric layer 67 may be changed as appropriate depending on the required transmission characteristics of the elastic wave device 1.

[0060] In the above configuration, when a high-frequency signal is applied between the planar electrodes 66 and 68, a potential difference is generated between the two electrodes, which distorts the piezoelectric layer 67 and generates bulk acoustic waves in the stacking direction. By adjusting the film thickness of the piezoelectric layer 67 to correspond to the pass band of the elastic wave device 1, an elastic wave device 1 with desired pass characteristics can be achieved.

[0061] 3D , the acoustic wave resonator 20B includes planar electrodes 66 and 68, a piezoelectric layer 67, a low acoustic impedance layer 161, a high acoustic impedance layer 162, and a support substrate 65. The planar electrode 66 is an example of a first planar electrode, the planar electrode 68 is an example of a second planar electrode, and the piezoelectric layer 67 is an example of a second piezoelectric layer. The planar electrode 66, the piezoelectric layer 67, and the planar electrode 68 are arranged in this order on the support substrate 65 to form a laminate. The support substrate 65 corresponds to the support substrate 40 shown in FIG. 1 . An acoustic multilayer film having a structure in which low acoustic impedance layers 161 and high acoustic impedance layers 162 are alternately stacked is disposed between the laminate and the support substrate 65. With this structure, the acoustic wave resonator 20B constitutes a solidly mounted resonator (SMR) type bulk acoustic wave resonator, and confines bulk acoustic waves above the acoustic multilayer film by utilizing Bragg reflection by the acoustic multilayer film.

[0062] It is sufficient that elastic wave device 1 includes at least one of elastic wave resonators 11 to 13 and at least one of elastic wave resonators 21 and 22 among elastic wave resonators 11 to 13, 21, and 22.

[0063] Returning to FIGS. 1, 2A, and 2B, the frame 70, the support conductors 71 and 72, the through electrodes 81 and 82, and the external connection electrodes 83 and 84 will be described.

[0064] Frame body 70 is disposed between principal surface 32b and principal surface 40a, and when principal surfaces 32b and 40a are viewed in plan, is disposed so as to surround elastic wave resonators 11 to 13, 21, and 22. Furthermore, frame body 70 is disposed so as to overlap support substrates 30 and 40 in the above-mentioned plan view.

[0065] The frame 70 is configured, for example, as a laminate of a support layer, a first bonding layer, and a second bonding layer. The first bonding layer is in contact with the piezoelectric layer 32 and is configured to surround the elastic wave resonators 21 and 22 in the planar view. The second bonding layer is in contact with the dielectric film 41 and is configured to surround the elastic wave resonators 11 to 13 in the planar view. The support layer is disposed between the first bonding layer and the second bonding layer and is configured to surround the elastic wave resonators 11 to 13, 21, and 22 in the planar view.

[0066] The support layer includes a conductor portion mainly composed of, for example, aluminum (Al). The first bonding layer and the second bonding layer each include a conductor portion mainly composed of, for example, at least one of aluminum (Al), copper (Cu), gold (Au), platinum (Pt), titanium (Ti), tin (Sn), silver (Ag), and nickel (Ni). In other words, the frame 70 may include a conductor portion made of a metal.

[0067] The frame body 70 separates the internal space of the frame body 70, in which the acoustic wave resonators 11 to 13, 21, and 22 are formed, from the external space of the frame body 70. The frame body 70 can ensure high accuracy in airtightness of the internal space. Setting the frame body 70 to, for example, ground potential can also block external noise. The frame body 70 may have ventilation holes, in which case the airtightness of the internal space does not need to be ensured. The frame body 70 may be made of a resin material if it is not necessary to ensure the airtightness of the internal space. The frame body 70 may be made of only a support layer, without including the first and second bonding layers.

[0068] Furthermore, an insulating material such as a resin member or glass frit may be disposed on the outer periphery of the frame body 70 so as to be in contact with the outer periphery surface of the frame body 70. This can increase the moisture resistance of the frame body 70 and also reinforce the mechanical strength of the frame body 70.

[0069] Each of the support conductors 71 and 72 is an example of a first conductor, is connected to at least one of the acoustic wave resonators 11 to 13, 21, and 22, is disposed inside the frame 70 in the plan view, and is in contact with the principal surface 32b and the principal surface 40a (or 41a). Each of the support conductors 71 and 72 transmits signals passing through the acoustic wave resonators 11 to 13, 21, and 22. Each of the support conductors 71 and 72 is configured as a laminate of a main body portion, a third bonding layer, and a fourth bonding layer. The third bonding layer is bonded to the piezoelectric layer 32. The fourth bonding layer is in contact with the dielectric film 41. As shown in FIG. 2B , the support conductor 71 is connected to the acoustic wave resonator 11, and as shown in FIG. 2A , the support conductor 72 is connected to the acoustic wave resonator 21. The main body portion is disposed between the third bonding layer and the fourth bonding layer.

[0070] The main body portion has the same material composition as the support layer. The third bonding layer has the same material composition as the first bonding layer. The fourth bonding layer has the same material composition as the second bonding layer. Note that the main body portion and the support layer may be formed by the same film formation process, the first bonding layer and the third bonding layer may be formed by the same film formation process, and the second bonding layer and the fourth bonding layer may be formed by the same film formation process.

[0071] Furthermore, some of the acoustic wave resonators 11 to 13, 21 and 22 may be electrically connected to the first or second bonding layer of the frame 70 via the third or fourth bonding layer and set to ground potential.

[0072] Note that the support conductors 71 and 72 may be formed only by the main body portion without including the third and fourth bonding layers. The support conductors 71 and 72 do not necessarily have to be included in the elastic wave device 1.

[0073] Each of the through electrodes 81 and 82 is a via conductor that is disposed to penetrate the support substrate 30 between the main surfaces 30a and 30b and is connected to at least one of the acoustic wave resonators 11 to 13, 21, and 22. The through electrodes 81 and 82 are made of, for example, a metal member primarily composed of Cu (copper). Each of the through electrodes 81 and 82 has, for example, either (1) a configuration in which the above-mentioned metal member is filled in a via (through hole), or (2) a configuration in which the above-mentioned metal member is plated on the inner wall of the via (through hole) and an insulating material such as resin is filled in the center.

[0074] In addition, each of the through electrodes 81 and 82 does not have to be a single via conductor extending from the main surface 30a to the main surface 30b, but may have a configuration in which multiple via conductors are connected via a planar electrode formed within the support substrate 30.

[0075] External connection electrodes 83 and 84 are each disposed on main surface 30 a, with external connection electrode 83 joined to through electrode 81 and external connection electrode 84 joined to through electrode 82. Each of external connection electrodes 83 and 84 is joined, for example, via solder or bumps, to an electrode on a motherboard on which elastic wave device 1 is mounted. Note that external connection electrodes 83 and 84 do not necessarily have to be included in elastic wave device 1.

[0076] According to the above configuration, the elastic wave resonators 11 to 13 are arranged on the main surface 40a of the support substrate 40, and the elastic wave resonators 21 and 22 are arranged on the main surface 32b of the support substrate 30, which is arranged opposite the support substrate 40, thereby making it possible to miniaturize the elastic wave device 1.

[0077] 4 is a cross-sectional view of the elastic wave device 1 mounted on a motherboard 90. As shown in the figure, the elastic wave device 1 may be mounted on a motherboard 90, which is an external substrate. An electrode 93 arranged on the main surface of the motherboard 90 is joined to an external connection electrode 83 via solder 91 (or a bump). An electrode 94 arranged on the main surface of the motherboard 90 is joined to an external connection electrode 84 via solder 92 (or a bump).

[0078] Support substrates 30 and 40 expand at high temperatures. Because the direction of elastic wave propagation in elastic wave resonators 11-13, which have piezoelectric laminates, intersects with the expansion direction parallel to the substrate surface, the resonance characteristics of elastic wave resonators 11-13 are less susceptible to the effects of thermal stress. In contrast, IDT electrodes 60 constituting elastic wave resonators 21 and 22 are formed parallel to the expansion direction, and therefore the resonance characteristics of elastic wave resonators 21 and 22 are likely to deteriorate due to the thermal stress.

[0079] In contrast, in elastic wave device 1, since through electrodes 81 and 82 are formed in support substrate 30, heat flowing into support substrate 30 can be easily dissipated to motherboard 90 via through electrodes 81 and 82. This makes it possible to suppress a temperature rise in support substrate 30, thereby reducing the frequency temperature change of elastic wave resonators 21 and 22 and suppressing deterioration of the resonance characteristics of elastic wave resonators 21 and 22.

[0080] Therefore, it is possible to provide a compact acoustic wave device 1 in which deterioration of characteristics due to heat is suppressed.

[0081] In addition, in the acoustic wave device 1 , the linear expansion coefficient of the support substrate 30 is smaller than the linear expansion coefficient of the piezoelectric layer 32 .

[0082] Thermal stress has a large component in a direction parallel to the principal surface 32b, and in the elastic wave resonators 21 and 22 including the IDT electrode 60 arranged in a direction parallel to the principal surface 32b, the occurrence of thermal stress in this direction tends to change the structure of the IDT electrode 60, resulting in deterioration of the resonance characteristics. In contrast, because the linear expansion coefficient of the support substrate 30 is smaller than that of the piezoelectric layer 32, the thermal expansion and contraction of the piezoelectric layer 32 can be suppressed by the support substrate 30. This suppresses deterioration of the frequency-temperature characteristics of the elastic wave resonators 21 and 22, thereby suppressing deterioration of the characteristics of the elastic wave device 1.

[0083] Furthermore, the support substrate 30 may be disposed so as to overlap the frame body 70 in the plan view. This increases the effect of the support substrate 30 in suppressing thermal expansion and contraction of the piezoelectric layer 32.

[0084] The linear expansion coefficient of support substrate 30 is preferably 13 ppm / K or less. The linear expansion coefficient of the piezoelectric material used for piezoelectric layer 32 is often 15 ppm / K or more. This allows the linear expansion coefficient of support substrate 30 to be smaller than the linear expansion coefficient of piezoelectric layer 32, thereby enabling support substrate 30 to suppress thermal expansion and contraction of piezoelectric layer 32. This suppresses deterioration of the frequency-temperature characteristics of elastic wave resonators 21 and 22, thereby suppressing characteristic degradation of elastic wave device 1.

[0085] Furthermore, the linear expansion coefficients of the aluminum nitride, quartz, alumina, sapphire, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, sialon, aluminum oxide, silicon oxynitride, silicon oxide, DLC, diamond, silicon, and gallium arsenide listed above as examples of materials for the support substrate 30 are each 13 ppm / K or less.

[0086] Furthermore, it is more desirable that the linear expansion coefficient of the support substrate 30 is 5 ppm / K or less. In other words, the linear expansion coefficient of the support substrate 30 is smaller than the linear expansion coefficient of the piezoelectric layer 32. This not only prevents the inherent thermal expansion and contraction of the piezoelectric layer 32 from becoming larger, but also makes it possible for the support substrate 30 to actively reduce the inherent thermal expansion and contraction of the piezoelectric layer 32.

[0087] Furthermore, it is desirable to use, for example, silicon, aluminum nitride, silicon nitride, silicon carbide, cordierite, silicon oxide, sialon, diamond, or a material containing any of the above materials as a main component for the support substrate 30. Each of these materials has a linear expansion coefficient of 5 ppm / K or less.

[0088] Furthermore, it is preferable that the support substrate 30 be made of silicon. Silicon has an even smaller linear expansion coefficient (reference value: 3.4 ppm / K), high thermal conductivity, and high processability during manufacturing. This actively suppresses thermal expansion and contraction of the piezoelectric layer 32 and improves the heat dissipation of the acoustic wave device 1.

[0089] In the acoustic wave device 1 , the linear expansion coefficient of the support substrate 40 is preferably smaller than the linear expansion coefficient of the piezoelectric layer 67 .

[0090] According to this, since the linear expansion coefficient of the support substrate 40 is smaller than the linear expansion coefficient of the piezoelectric layer 67 , the thermal expansion and contraction of the piezoelectric layer 67 can be suppressed by the support substrate 40 .

[0091] Furthermore, the support substrate 40 may be disposed so as to overlap the frame body 70 in the plan view. This increases the effect of the support substrate 40 in suppressing thermal expansion and contraction of the piezoelectric layer 67.

[0092] The linear expansion coefficient of the support substrate 40 is preferably 13 ppm / K or less. The linear expansion coefficient of the piezoelectric material used for the piezoelectric layer 67 is often 15 ppm / K or more. In this case, the linear expansion coefficient of the support substrate 40 is smaller than the linear expansion coefficient of the piezoelectric layer 67, and therefore the thermal expansion and contraction of the piezoelectric layer 67 can be suppressed by the support substrate 40.

[0093] Furthermore, it is more desirable that the linear expansion coefficient of the support substrate 40 be 5 ppm / K or less. In other words, the linear expansion coefficient of the support substrate 40 is smaller than the linear expansion coefficient of the piezoelectric layer 67. This not only prevents the inherent thermal expansion and contraction of the piezoelectric layer 67 from becoming larger, but also makes it possible to actively reduce the inherent thermal expansion and contraction of the piezoelectric layer 67 by using the support substrate 40.

[0094] Furthermore, it is desirable to use, for example, silicon, aluminum nitride, silicon nitride, silicon carbide, cordierite, silicon oxide, sialon, diamond, or a material containing any of the above materials as a main component for the support substrate 40. Each of these materials has a linear expansion coefficient of 5 ppm / K or less.

[0095] Furthermore, it is preferable that support substrate 40 be made of silicon. Silicon has an even smaller linear expansion coefficient (reference value: 3.4 ppm / K), high thermal conductivity, and high processability during manufacturing. This actively suppresses thermal expansion and contraction of piezoelectric layer 67 and improves the heat dissipation of acoustic wave device 1.

[0096] Furthermore, support substrate 30 and support substrate 40 may be made of the same material. This makes the linear expansion coefficients of support substrates 30 and 40 equal, stabilizing the frequency temperature coefficients of elastic wave resonators 11 to 13, 21, and 22. Furthermore, because thermal stress is balanced between the upper and lower parts of elastic wave device 1, bond failure at frame 70 and support conductors 71 and 72 can be suppressed, improving reliability.

[0097] Furthermore, the thickness of the support substrate 30 may be different from the thickness of the support substrate 40. When the support substrate 30 is thicker than the support substrate 40, it is possible to prevent the support substrate 30 from breaking (or cracking) due to thermal stress in the elastic wave device 1 mounted on the mother substrate 90. On the other hand, when the support substrate 40 is thicker than the support substrate 30, when the support substrate 40 is picked up by contacting it with a suction collet or the like during manufacturing of the elastic wave device 1, it is possible to prevent the support substrate 40 from breaking (or cracking) due to the impact of such contact.

[0098] Furthermore, the support substrates 30 and 40 may be made of different materials. When the support substrates 30 and 40 are made of different materials, for example, if the strength of the support substrate 30 is greater than the strength of the support substrate 40, the support substrate 30 can be prevented from breaking (or cracking) due to thermal stress in the elastic wave device 1 mounted on the mother substrate 90. On the other hand, when the support substrates 30 and 40 are made of different materials, for example, if the strength of the support substrate 40 is greater than the strength of the support substrate 30, when the support substrate 40 is brought into contact with a suction collet or the like to be picked up during manufacturing of the elastic wave device 1, the support substrate 40 can be prevented from breaking (or cracking) due to the impact of such contact.

[0099] Furthermore, it is desirable that the total thickness of support substrates 30 and 40 be greater than the distance between principal surface 32b and principal surface 40a. In this case, the total thickness of support substrates 30 and 40 accounts for a high proportion of the height of elastic wave device 1, and therefore support substrates 30 and 40 can effectively suppress thermal stress, thereby further stabilizing the frequency temperature coefficients of elastic wave resonators 11-13, 21, and 22.

[0100] Furthermore, when the main surface 32b is viewed from above, it is desirable that the piezoelectric layer 32 and the through electrodes 81 and 82 are not in contact with each other.

[0101] According to this, when holes are drilled in the support substrate 30 to provide the through electrodes 81 and 82 during manufacturing, the piezoelectric layer 32, which is difficult to process, is not processed at the same time as the holes are drilled, thereby reducing damage to the piezoelectric layer 32 and improving the reliability of the elastic wave device 1.

[0102] [2 Pass Characteristics of Elastic Wave Device 1] Elastic wave device 1 according to this embodiment can be used as an elastic wave filter. FIG. 5 is a diagram showing an example of the circuit configuration of elastic wave device 1 according to this embodiment. As shown in the figure, elastic wave device 1 constitutes, for example, a ladder-type elastic wave filter 2 having elastic wave resonators 11 to 13, 21, and 22. Elastic wave filter 2 includes terminals 101 and 102 for inputting and outputting high-frequency signals, and elastic wave resonators 11 to 13, 21, and 22.

[0103] Each of the acoustic wave resonators 11, 12, and 13 is a series arm resonator arranged in a series arm path connecting a terminal 101 (first terminal) and a terminal 102 (second terminal).

[0104] Each of the acoustic wave resonators 21 and 22 is a parallel arm resonator arranged in a parallel arm path connecting the series arm path to the ground.

[0105] When the above-described elastic wave filter 2 is used as the elastic wave device 1, the layout of the elastic wave resonators 11 to 13, 21, and 22 may be, for example, as shown in FIGS. 2A and 2B . That is, the elastic wave resonators 21 and 22, which are parallel arm resonators, are arranged on the principal surface 32b, and the elastic wave resonators 11 to 13, which are series arm resonators, are arranged on the principal surface 41a. Terminal 101, which serves as an input / output terminal, is connected to the elastic wave resonator 11 on the principal surface 41a and is also connected to the support conductor 71. Terminal 102, which serves as an input / output terminal, is connected to the elastic wave resonator 13 on the principal surface 41a. Terminal 105, which serves as a ground terminal, is connected to the elastic wave resonator 21 on the principal surface 32b and is also connected to the support conductor 72. Terminal 106, which serves as a ground terminal, is connected to the elastic wave resonator 22 on the principal surface 32b. Terminal 103 is connected to the elastic wave resonator 21 on the principal surface 32b and is also connected to the elastic wave resonators 11 and 12 on the principal surface 41a. Terminal 103 on principal surface 32b and terminal 103 on principal surface 41a are connected by a support conductor. Terminal 104 is connected to elastic wave resonator 22 on principal surface 32b and to elastic wave resonators 12 and 13 on principal surface 41a. Terminal 104 on principal surface 32b and terminal 104 on principal surface 41a are connected by a support conductor.

[0106] 6 is a diagram showing the impedance characteristics and passband characteristics of elastic wave device 1 according to an embodiment. When elastic wave filter 2 having the above configuration is used as elastic wave device 1, the anti-resonance frequency fap of elastic wave resonators 21 and 22 is made to substantially coincide with the resonance frequency frs of elastic wave resonators 11 to 13. Furthermore, the resonance frequency frp of elastic wave resonators 21 and 22 is located on the lower frequency side of anti-resonance frequency fap, and the anti-resonance frequency fas of elastic wave resonators 11 to 13 is located on the higher frequency side of resonance frequency frs. As a result, elastic wave filter 2 becomes a bandpass filter in which the resonance frequency frp serves as an attenuation pole on the low frequency side and the anti-resonance frequency fas serves as an attenuation pole on the high frequency side, and the passband includes the anti-resonance frequency fap and the resonance frequency frs.

[0107] Elastic wave resonators 11-13 are piezoelectric thin-film resonators configured with a laminate of planar electrode 66, piezoelectric layer 67, and planar electrode 68. These resonators utilize bulk acoustic waves and have a relatively small resonance band ratio (resonance bandwidth: fas-frs) and steep impedance characteristics. On the other hand, elastic wave resonators 21 and 22 are elastic wave resonators (XBAR) including IDT electrode 60. By using piezoelectric layer 32 with a large electromechanical coupling coefficient, the resonance band ratio (resonance bandwidth: fap-frp) can be relatively increased. By utilizing this difference in the resonance band ratio characteristics, it is possible to reduce the steepness of the low-frequency end of the pass band (the transition region from the pass band to the attenuation band) and increase the steepness of the high-frequency end of the pass band (the transition region from the pass band to the attenuation band), as shown in FIG. 6 .

[0108] The ratio of the series arm and parallel arm arrangement of the XBAR and bulk acoustic wave resonators may be changed depending on the required steepness of the passband edge. For example, if the steepness of the low-frequency edge of the passband is desired to be slightly higher, one of acoustic wave resonators 21 and 22 may be connected as a series arm resonator. Furthermore, if the steepness of the high-frequency edge of the passband is desired to be slightly lower or slightly higher, at least one of acoustic wave resonators 11 to 13 may be connected as a parallel arm resonator.

[0109] Furthermore, for example, if it is desired to make the steepness of the low-frequency end of the pass band greater than the steepness of the high-frequency end of the pass band, elastic wave resonators 11 to 13 (bulk elastic wave resonators) may be connected as parallel arm resonators, and elastic wave resonators 21 and 22 (XBAR) may be connected as series arm resonators. FIG. 7 is a diagram illustrating the impedance characteristics and pass characteristics of an elastic wave device according to a modification of the embodiment. The elastic wave device according to this modification has a ladder-type elastic wave filter configuration in which elastic wave resonators 11 to 13 are connected as parallel arm resonators, and elastic wave resonators 21 and 22 are connected as series arm resonators. As a result, the pass characteristics of the elastic wave filter according to this modification are as shown in FIG. 7 , and it is possible to increase the steepness of the low-frequency end of the pass band and decrease the steepness of the high-frequency end of the pass band.

[0110] The ratio of the series arm and parallel arm arrangement of the XBAR and bulk acoustic wave resonators may be changed depending on the required steepness of the passband edge. For example, if the steepness of the low-frequency edge of the passband is to be slightly lowered, at least one of acoustic wave resonators 11 to 13 may be connected as a series arm resonator. Furthermore, if the steepness of the low-frequency edge of the passband is to be slightly lowered or the steepness of the high-frequency edge of the passband is to be slightly increased, either acoustic wave resonator 21 or 22 may be connected as a parallel arm resonator.

[0111] [3. Effects, etc.] As described above, elastic wave device 1 according to this embodiment includes support substrate 30 having principal surfaces 30a and 30b facing each other, piezoelectric layer 32 having principal surface 32a facing principal surface 30b and principal surface 32b facing principal surface 32a, elastic wave resonator 21 arranged on principal surface 32b, support substrate 40 having principal surface 40a facing principal surface 32b with space 140 interposed therebetween, elastic wave resonator 11 arranged on principal surface 40a, and elastic wave resonator 21 arranged between principal surfaces 32b and 40a when principal surfaces 32b and 40a are viewed in plan. and a through electrode 81 arranged to penetrate the support substrate 30 between the main surfaces 30a and 30b and connected to at least one of the elastic wave resonators 11 and 21. The elastic wave resonator 21 includes an IDT electrode 60 arranged on the main surface 32b, and when the thickness of the piezoelectric layer 32 is d and the electrode finger pitch of the IDT electrode 60 is p, d / p is 0.5 or less. The elastic wave resonator 11 includes a planar electrode 66, a piezoelectric layer 67, and a planar electrode 68 arranged in this order from the main surface 40a toward the main surface 32b.

[0112] This allows the elastic wave resonators 21 and 11 to be distributed across the opposing support substrates 30 and 40, thereby enabling the size of the elastic wave device 1 to be reduced. Furthermore, the IDT electrodes 60 constituting the elastic wave resonators 21 are formed parallel to the expansion direction parallel to the substrate surfaces. This means that the resonance characteristics of the elastic wave resonators 21 are likely to deteriorate due to thermal stress generated in the support substrate 30 at high temperatures. In contrast, in the elastic wave device 1, the through electrodes 81 are formed in the support substrate 30, which allows heat flowing into the support substrate 30 to be easily dissipated to an external substrate via the through electrodes 81. This suppresses temperature increases in the support substrate 30, thereby reducing the frequency temperature change of the elastic wave resonators 21 and suppressing deterioration of the resonance characteristics of the elastic wave resonators 21. This makes it possible to provide a compact elastic wave device 1 in which thermal degradation is suppressed.

[0113] For example, the elastic wave device 1 further includes a support conductor 71 that is connected to at least one of the elastic wave resonators 11 and 21, is positioned inside the frame body 70 when the main surfaces 32b and 40a are viewed in a plane, and is in contact with the main surfaces 32b and 40a.

[0114] This allows signals passing through acoustic wave resonator 11 arranged on main surface 40a to be transmitted to support substrate 30, and also increases the bonding strength between support substrates 30 and 40.

[0115] Furthermore, for example, in the acoustic wave device 1 , the linear expansion coefficient of the support substrate 30 is smaller than the linear expansion coefficient of the piezoelectric layer 32 .

[0116] This allows the support substrate 30 to suppress thermal expansion and contraction of the piezoelectric layer 32. This suppresses deterioration of the frequency-temperature characteristics of the acoustic wave resonator 21, thereby suppressing deterioration of the characteristics of the acoustic wave device 1.

[0117] Furthermore, for example, in the elastic wave device 1, the frame body 70 is disposed so as to overlap the support substrates 30 and 40 in the above-described plan view.

[0118] As a result, the support substrates 30 and 40 are positioned up to the area that overlaps with the frame body 70 in the above-mentioned planar view, so that the support substrate 30 has a greater effect of suppressing the thermal expansion and contraction of the piezoelectric layer 32, and the support substrate 40 has a greater effect of suppressing the thermal expansion and contraction of the piezoelectric layer 67.

[0119] Furthermore, for example, in the acoustic wave device 1 , a gap 160 is provided between the main surface 32 a and the support substrate 30 in the region overlapping with the IDT electrode 60 in the plan view.

[0120] According to this, acoustic wave resonator 21 functions as an XBAR having a membrane structure.

[0121] For example, the elastic wave device 1 further includes an acoustic impedance layer disposed between the main surface 32a and the support substrate 30, and configured such that low acoustic impedance layers 161 having a relatively low acoustic impedance and high acoustic impedance layers 162 having a relatively high acoustic impedance are alternately stacked.

[0122] According to this, the acoustic wave resonator 21 functions as an XBAR having an acoustic impedance layer.

[0123] Furthermore, for example, in the acoustic wave device 1 , the linear expansion coefficient of the support substrate 40 is smaller than the linear expansion coefficient of the piezoelectric layer 67 .

[0124] This allows the support substrate 40 to suppress thermal expansion and contraction of the piezoelectric layer 67. This suppresses deterioration of the frequency-temperature characteristics of the acoustic wave resonator 11, thereby suppressing deterioration of the characteristics of the acoustic wave device 1.

[0125] In addition, for example, in the acoustic wave device 1, at least one of the linear expansion coefficients of the support substrate 30 and the support substrate 40 is 13 ppm / K or less.

[0126] The linear expansion coefficient of the piezoelectric material used for the piezoelectric layers 32 and 67 is often 15 ppm / K or more. This allows the linear expansion coefficient of the support substrate 30 to be smaller than that of the piezoelectric layer 32 and / or the linear expansion coefficient of the support substrate 40 to be smaller than that of the piezoelectric layer 67, so that the thermal expansion and contraction of the piezoelectric layer 32 can be suppressed by the support substrate 30 and / or the thermal expansion and contraction of the piezoelectric layer 67 can be suppressed by the support substrate 30.

[0127] Furthermore, for example, in the elastic wave device 1, at least one of the support substrates 30 and 40 includes at least one of silicon, sapphire, spinel, quartz crystal, gallium arsenide, aluminum nitride, alumina, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, silicon oxide, sialon, silicon oxynitride, diamond, and diamond-like carbon.

[0128] According to this, since the linear expansion coefficient of the above material is 13 ppm / K or less, the thermal expansion and contraction of the piezoelectric layer 32 can be suppressed by the support substrate 30, and / or the thermal expansion and contraction of the piezoelectric layer 67 can be suppressed by the support substrate 40.

[0129] Furthermore, in the acoustic wave device 1, for example, at least one of the linear expansion coefficients of the support substrate 30 and the support substrate 40 is 5 ppm / K or less.

[0130] This makes it possible to actively suppress the thermal expansion and contraction of the piezoelectric layer 32 and / or the thermal expansion and contraction of the piezoelectric layer 67 .

[0131] Furthermore, in the acoustic wave device 1, at least one of the support substrates 30 and 40 includes at least one of silicon, aluminum nitride, silicon nitride, silicon carbide, cordierite, silicon oxide, sialon, and diamond.

[0132] According to this, since the linear expansion coefficient of the above material is 5 ppm / K or less, the thermal expansion and contraction of the piezoelectric layer 32 can be actively suppressed and / or the thermal expansion and contraction of the piezoelectric layer 67 can be actively suppressed.

[0133] Furthermore, for example, in the acoustic wave device 1, the support substrate 30 and the support substrate 40 are made of the same material.

[0134] This makes the linear expansion coefficients of support substrates 30 and 40 equal, stabilizing the frequency temperature coefficients of elastic wave resonators 11 and 21. Furthermore, since thermal stress is balanced between the upper and lower parts of elastic wave device 1, bond breakdown between frame body 70 and support conductor 71 can be suppressed, improving reliability.

[0135] Furthermore, for example, in the acoustic wave device 1, the thickness of the support substrate 30 and the thickness of the support substrate 40 are different.

[0136] When the support substrate 30 is thicker than the support substrate 40, it is possible to prevent the support substrate 30 from breaking (or cracking) due to thermal stress in the elastic wave device 1 mounted on the motherboard. On the other hand, when the support substrate 40 is thicker than the support substrate 30, it is possible to prevent the support substrate 40 from breaking (or cracking) due to the impact of contact when the support substrate 40 is brought into contact with a suction collet or the like for picking up during the manufacture of the elastic wave device 1.

[0137] Furthermore, for example, in the acoustic wave device 1, the support substrate 30 and the support substrate 40 are made of different materials.

[0138] For example, if the strength of the support substrate 30 is greater than the strength of the support substrate 40, the different materials for the support substrates 30 and 40 can prevent the support substrate 30 from breaking (or cracking) due to thermal stress in the elastic wave device 1 mounted on the mother substrate 90. On the other hand, for example, if the strength of the support substrate 40 is greater than the strength of the support substrate 30, the different materials for the support substrates 30 and 40 can prevent the support substrate 40 from breaking (or cracking) due to the impact of contact when the support substrate 40 is brought into contact with a suction collet or the like for picking up during manufacturing of the elastic wave device 1.

[0139] Furthermore, for example, in the acoustic wave device 1, the total thickness of the support substrates 30 and 40 is greater than the distance between the principal surface 32b and the principal surface 40a.

[0140] As a result, the total thickness of the support substrates 30 and 40 accounts for a high proportion of the height of the elastic wave device 1, so that the support substrates 30 and 40 can effectively suppress thermal stress, and the frequency temperature coefficients of the elastic wave resonators 11 and 21 can be further stabilized.

[0141] For example, the elastic wave device 1 further includes terminals 101 and 102, the elastic wave resonator 11 is a series arm resonator arranged in a series arm path connecting the terminals 101 and 102, and the elastic wave resonator 21 is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

[0142] This allows the steepness of the low frequency end of the pass band of the elastic wave device 1 to be reduced and the steepness of the high frequency end of the pass band to be increased.

[0143] For example, the elastic wave device 1 further includes terminals 101 and 102, a plurality of elastic wave resonators 21 and 22 arranged on the main surface 32b, and a plurality of elastic wave resonators 11 to 13 arranged on the main surface 40a, all of the elastic wave resonators 11 to 13 being series arm resonators arranged on a series arm path connecting the terminal 101 and the terminal 102, and at least one of the elastic wave resonators 21 and 22 being a parallel arm resonator arranged on a parallel arm path connecting the series arm path and ground.

[0144] In this way, since all of the elastic wave resonators having a laminate of the planar electrode 66, the piezoelectric layer 67, and the planar electrode 68 are series arm resonators, it is possible to further increase the steepness of the high frequency end of the pass band of the elastic wave device 1.

[0145] For example, the elastic wave device according to the modified example further includes terminals 101 and 102, where the elastic wave resonator 21 is a series arm resonator arranged in a series arm path connecting the terminal 101 and the terminal 102, and the elastic wave resonator 11 is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

[0146] This makes it possible to increase the steepness of the low frequency end of the pass band of the elastic wave device and decrease the steepness of the high frequency end of the pass band.

[0147] For example, an elastic wave device according to a modified example includes terminals 101 and 102, a plurality of elastic wave resonators 21 and 22 arranged on main surface 32b, and a plurality of elastic wave resonators 11 to 13 arranged on main surface 40a, where at least one of elastic wave resonators 21 and 22 is a series arm resonator arranged in a series arm path connecting terminal 101 and terminal 102, and all of elastic wave resonators 11 to 13 are parallel arm resonators arranged in parallel arm paths connecting the series arm path and ground.

[0148] In this way, all of the elastic wave resonators having a laminate of the planar electrode 66, the piezoelectric layer 67, and the planar electrode 68 are parallel arm resonators, so it is possible to further increase the steepness of the low frequency end of the pass band of the elastic wave device.

[0149] Furthermore, for example, in the acoustic wave device 1 , the thickness of the piezoelectric layer 32 is greater than the thickness of the piezoelectric layer 67 .

[0150] According to this, when drilling holes in the support substrate 30 to provide the through electrodes 81 during manufacturing, the piezoelectric layer 32, which is difficult to process, is removed from the position overlapping with the hole before processing, thereby reducing damage to electrodes and the like joined to the through electrodes 81 and improving the reliability of the elastic wave device 1.

[0151] The features of the acoustic wave devices described based on the above-described embodiment and modifications will be described below.

[0152] <1> A piezoelectric element comprising: a first support substrate having a first main surface and a second main surface opposing each other; a first piezoelectric layer having a third main surface facing the second main surface and a fourth main surface facing the third main surface; a first acoustic wave resonator arranged on the fourth main surface; a second support substrate having a fifth main surface facing the fourth main surface across a space; a second acoustic wave resonator arranged on the fifth main surface; a frame arranged between the fourth main surface and the fifth main surface so as to surround the first acoustic wave resonator and the second acoustic wave resonator when the fourth main surface and the fifth main surface are viewed in plan; and a through electrode arranged to penetrate the first support substrate between the first main surface and the second main surface and connected to at least one of the first acoustic wave resonator and the second acoustic wave resonator, an elastic wave device in which, when a thickness of the first piezoelectric layer is d and an electrode finger pitch of the IDT electrode is p, d / p is 0.5 or less, and the second elastic wave resonator includes a first planar electrode, a second piezoelectric layer, and a second planar electrode arranged in this order from the fifth principal surface toward the fourth principal surface.

[0153] <2> The elastic wave device according to <1>, further including a first conductor connected to at least one of the first elastic wave resonator and the second elastic wave resonator, disposed inside the frame when the fourth main surface and the fifth main surface are viewed in a plan view, and in contact with the fourth main surface and the fifth main surface.

[0154] <3> The acoustic wave device according to <1> or <2>, wherein the first support substrate has a linear expansion coefficient smaller than the linear expansion coefficient of the first piezoelectric layer.

[0155] <4> The acoustic wave device according to <3>, wherein the frame is arranged to overlap the first support substrate and the second support substrate in the plan view.

[0156] <5> The acoustic wave device according to any one of <1> to <4>, wherein a gap is provided between the third main surface and the first support substrate in a region overlapping with the IDT electrode in the plan view.

[0157] <6> The elastic wave device according to any one of <1> to <4>, further comprising an acoustic impedance layer disposed between the third principal surface and the first support substrate, the acoustic impedance layer having a configuration in which low acoustic impedance layers having a relatively low acoustic impedance and high acoustic impedance layers having a relatively high acoustic impedance are alternately stacked.

[0158] <7> The acoustic wave device according to any one of <1> to <6>, wherein the second support substrate has a linear expansion coefficient smaller than the linear expansion coefficient of the second piezoelectric layer.

[0159] <8> The acoustic wave device according to any one of <1> to <6>, wherein at least one of the first support substrate and the second support substrate has a linear expansion coefficient of 13 ppm / K or less.

[0160] <9> The acoustic wave device according to any one of <1> to <6>, wherein at least one of the first support substrate and the second support substrate includes at least one of silicon, sapphire, spinel, quartz crystal, gallium arsenide, aluminum nitride, alumina, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, silicon oxide, sialon, silicon oxynitride, and diamond.

[0161] <10> The acoustic wave device according to <9>, wherein at least one of the first support substrate and the second support substrate has a linear expansion coefficient of 5 ppm / K or less.

[0162] <11> The acoustic wave device according to any one of <1> to <6>, wherein at least one of the first support substrate and the second support substrate includes at least one of silicon, aluminum nitride, silicon nitride, silicon carbide, cordierite, silicon oxide, sialon, and diamond.

[0163] <12> The acoustic wave device according to any one of <1> to <6>, wherein the first support substrate and the second support substrate are made of the same material.

[0164] <13> The acoustic wave device according to any one of <1> to <6>, wherein the first support substrate and the second support substrate have different thicknesses.

[0165] <14> The acoustic wave device according to any one of <1> to <6>, wherein the first support substrate and the second support substrate are made of different materials.

[0166] <15> The acoustic wave device according to any one of <1> to <6>, wherein a total thickness of the first support substrate and the second support substrate is greater than a distance between the fourth main surface and the fifth main surface.

[0167] <16> The elastic wave device according to any one of <1> to <15>, further including a first terminal and a second terminal, wherein the second elastic wave resonator is a series arm resonator arranged in a series arm path connecting the first terminal and the second terminal, and the first elastic wave resonator is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

[0168] <17> The elastic wave device according to any one of <1> to <15> further includes a first terminal and a second terminal; a plurality of the first elastic wave resonators arranged on the fourth main surface; and a plurality of the second elastic wave resonators arranged on the fifth main surface, wherein all of the second elastic wave resonators are series arm resonators arranged in a series arm path connecting the first terminal and the second terminal; and at least one of the first elastic wave resonators is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

[0169] <18> The elastic wave device according to any one of <1> to <15>, further including a first terminal and a second terminal, wherein the first elastic wave resonator is a series arm resonator arranged in a series arm path connecting the first terminal and the second terminal, and the second elastic wave resonator is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

[0170] <19> The elastic wave device according to any one of <1> to <15> further includes a first terminal and a second terminal; a plurality of the first elastic wave resonators arranged on the fourth main surface; and a plurality of the second elastic wave resonators arranged on the fifth main surface, wherein at least one of the plurality of first elastic wave resonators is a series arm resonator arranged in a series arm path connecting the first terminal and the second terminal; and all of the plurality of second elastic wave resonators are parallel arm resonators arranged in a parallel arm path connecting the series arm path and ground.

[0171] <20> The acoustic wave device according to any one of <1> to <19>, wherein the first piezoelectric layer has a thickness greater than the thickness of the second piezoelectric layer.

[0172] The present invention can be widely used as a small acoustic wave filter in communication devices such as mobile phones.

[0173] REFERENCE SIGNS LIST 1 Acoustic wave device 2 Acoustic wave filter 10A, 10B, 11, 12, 13, 20A, 20B, 21, 22 Acoustic wave resonator 30, 40, 65 Support substrate 30a, 30b, 32a, 32b, 40a, 40b, 41a Main surface 31 Low acoustic velocity layer 32, 67 Piezoelectric layer 41 Dielectric film 50 Piezoelectric substrate 55 Protective layer 60 IDT electrode 60a, 60b Comb-shaped electrode 61a, 61b Electrode fingers 62a, 62b Bus bar electrode 66, 68 Planar electrode 70 Frame 71, 72 Support conductor 81, 82 Through electrode 83, 84 External connection electrode 90 Motherboard 91, 92 Solder 93, 94 Electrode 101, 102, 103, 104, 105, 106 Terminals 140, 150 Space 160 Gap 161 Low acoustic impedance layer 162 High acoustic impedance layer 540 Adhesion layer 542 Main electrode layer

Claims

1. A piezoelectric element comprising: a first support substrate having first and second main surfaces opposing each other; a first piezoelectric layer having a third main surface facing the second main surface and a fourth main surface facing the third main surface; a first acoustic wave resonator arranged on the fourth main surface; a second support substrate having a fifth main surface facing the fourth main surface across a space; a second acoustic wave resonator arranged on the fifth main surface; a frame arranged between the fourth and fifth main surfaces and surrounding the first and second acoustic wave resonators when the fourth and fifth main surfaces are viewed in plan; and a through electrode arranged to penetrate the first support substrate between the first and second main surfaces and connected to at least one of the first and second acoustic wave resonators, an elastic wave device, wherein d / p is 0.5 or less, where d is a thickness of the first piezoelectric layer and p is an electrode finger pitch of the IDT electrode; and the second elastic wave resonator includes a first planar electrode, a second piezoelectric layer, and a second planar electrode arranged in this order from the fifth principal surface toward the fourth principal surface.

2. The elastic wave device according to claim 1, further comprising a first conductor connected to at least one of the first elastic wave resonator and the second elastic wave resonator, disposed inside the frame when the fourth principal surface and the fifth principal surface are viewed in plan, and in contact with the fourth principal surface and the fifth principal surface.

3. The acoustic wave device according to claim 1 or 2, wherein the linear expansion coefficient of the first support substrate is smaller than the linear expansion coefficient of the first piezoelectric layer.

4. The acoustic wave device according to claim 3, wherein the frame body is arranged to overlap the first support substrate and the second support substrate in the plan view.

5. The acoustic wave device according to claim 1, wherein a gap is provided between the third main surface and the first support substrate in a region that overlaps with the IDT electrode in the plan view.

6. The elastic wave device according to any one of claims 1 to 4, further comprising an acoustic impedance layer disposed between the third principal surface and the first support substrate, the acoustic impedance layer having a configuration in which low acoustic impedance layers having a relatively low acoustic impedance and high acoustic impedance layers having a relatively high acoustic impedance are alternately stacked.

7. The acoustic wave device according to any one of claims 1 to 6, wherein the second support substrate has a linear expansion coefficient smaller than the linear expansion coefficient of the second piezoelectric layer.

8. The acoustic wave device according to any one of claims 1 to 6, wherein at least one of the first support substrate and the second support substrate has a linear expansion coefficient of 13 ppm / K or less.

9. The acoustic wave device according to any one of claims 1 to 6, wherein at least one of the first support substrate and the second support substrate contains at least one of silicon, sapphire, spinel, quartz crystal, gallium arsenide, aluminum nitride, alumina, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, silicon oxide, sialon, silicon oxynitride, and diamond.

10. The acoustic wave device according to claim 9, wherein at least one of the first support substrate and the second support substrate has a linear expansion coefficient of 5 ppm / K or less.

11. The acoustic wave device according to any one of claims 1 to 6, wherein at least one of the first support substrate and the second support substrate includes at least one of silicon, aluminum nitride, silicon nitride, silicon carbide, cordierite, silicon oxide, sialon, and diamond.

12. The acoustic wave device according to any one of claims 1 to 6, wherein the first support substrate and the second support substrate are made of the same material.

13. The acoustic wave device according to any one of claims 1 to 6, wherein the first support substrate and the second support substrate have different thicknesses.

14. The acoustic wave device according to any one of claims 1 to 6, wherein the first support substrate and the second support substrate are made of different materials.

15. The acoustic wave device according to any one of claims 1 to 6, wherein the total thickness of the first support substrate and the second support substrate is greater than the distance between the fourth main surface and the fifth main surface.

16. The elastic wave device according to any one of claims 1 to 15, further comprising a first terminal and a second terminal, wherein the second elastic wave resonator is a series arm resonator arranged in a series arm path connecting the first terminal and the second terminal, and the first elastic wave resonator is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

17. The elastic wave device according to any one of claims 1 to 15, further comprising: a first terminal and a second terminal; a plurality of the first elastic wave resonators arranged on the fourth principal surface; and a plurality of the second elastic wave resonators arranged on the fifth principal surface, wherein all of the plurality of second elastic wave resonators are series arm resonators arranged in a series arm path connecting the first terminal and the second terminal; and at least one of the plurality of first elastic wave resonators is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

18. The elastic wave device according to any one of claims 1 to 15, further comprising a first terminal and a second terminal, wherein the first elastic wave resonator is a series arm resonator arranged in a series arm path connecting the first terminal and the second terminal, and the second elastic wave resonator is a parallel arm resonator arranged in a parallel arm path connecting the series arm path and ground.

19. The elastic wave device according to any one of claims 1 to 15, further comprising: a first terminal and a second terminal; a plurality of the first elastic wave resonators arranged on the fourth principal surface; and a plurality of the second elastic wave resonators arranged on the fifth principal surface, wherein at least one of the plurality of first elastic wave resonators is a series arm resonator arranged in a series arm path connecting the first terminal and the second terminal; and all of the plurality of second elastic wave resonators are parallel arm resonators arranged in parallel arm paths connecting the series arm path and ground.

20. The elastic wave device according to any one of claims 1 to 19, wherein the thickness of the first piezoelectric layer is greater than the thickness of the second piezoelectric layer.

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