Elastic wave device

Abstract

An elastic wave device (1) is provided with: a substrate (10) having main surfaces (10a, 10b) facing each other; a substrate (20) having a main surface (20a) facing the main surface (10a); a functional electrode (34) disposed on the main surface (20a); a support part disposed between the main surfaces (10a) and (20a) and configured so as to provide a space between the main surfaces (10a) and (20a); and a via conductor (11) disposed on the substrate (10) from the main surface (10a) toward the main surface (10b), the support portion having: a metal film (31) disposed on the main surface (10a) and in contact with the via conductor (11); and a metal film (32) that is disposed on the opposite side of the via conductor (11) with the metal film (31) interposed therebetween and is in contact with the metal film (31), the area of the metal film (31) including the area of the metal film (32) in plan view of the main surface (10a), the area of the metal film (31) being larger than the area of the metal film (32), and the hardness of the metal film (32) being higher than the hardness of the metal film (31).

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Patent Document 1 discloses an electronic device comprising: a piezoelectric thin-film resonator, a first substrate (piezoelectric substrate) on which the piezoelectric thin-film resonator is disposed, a second substrate (cover substrate) disposed with the first substrate sandwiching the piezoelectric thin-film resonator, a thin film of a high resistivity material formed on the second substrate, and a via conductor disposed on the first substrate. Accordingly, while suppressing signal coupling of the piezoelectric thin-film resonator to the second substrate, the signal can be input and output from the first substrate side.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-137742 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] As a structure for signal input and output of a piezoelectric thin film resonator (elastic wave resonator), if a via conductor is formed by processing a substrate made of piezoelectric material, there is a concern about signal degradation of the elastic wave resonator.

[0008] In contrast, a configuration in which a via conductor is formed on the cover substrate to enable signal input and output of the elastic wave resonator can be cited. However, in this configuration, in order to suppress signal degradation of the elastic wave resonator, it is necessary to improve the bonding strength of the support portion that connects to the electrodes of the via conductor and the piezoelectric substrate while ensuring the space between the piezoelectric substrate and the cover substrate.

[0009] Therefore, the object of the present invention is to provide an elastic wave device with improved joint strength of the support portion.

[0010] Technical solutions for solving the problem

[0011] To achieve the above objectives, one aspect of the present invention relates to an elastic wave device comprising: a first substrate having a first main surface and a second main surface facing each other; a second substrate having a third main surface facing the first main surface; a functional electrode disposed on the third main surface; a support portion disposed between the first main surface and the third main surface, configured to provide a space between the first main surface and the third main surface; and a via conductor disposed on the first substrate from the first main surface toward the second main surface. The support portion comprises: a first metal film disposed on the first main surface and in contact with the via conductor; and a second metal film sandwiching the first metal film disposed on the side opposite to the via conductor and in contact with the first metal film. When viewed from the first main surface, the area of ​​the first metal film includes the area of ​​the second metal film, and the area of ​​the first metal film is larger than the area of ​​the second metal film, and the hardness of the second metal film is higher than the hardness of the first metal film.

[0012] Invention Effects

[0013] According to the present invention, an elastic wave device with improved joint strength of the support portion can be provided. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the elastic wave device according to the embodiment.

[0015] Figure 2A This is a first top view of the elastic wave device according to the embodiment.

[0016] Figure 2B This is a second top view of the elastic wave device according to the embodiment.

[0017] Figure 2C This is a third top view of the elastic wave device according to the embodiment.

[0018] Figure 3A These are schematic top views and cross-sectional views illustrating a first example of an elastic wave resonator constituting an elastic wave device according to an embodiment.

[0019] Figure 3B This is a cross-sectional view schematically illustrating a second example of an elastic wave resonator constituting an elastic wave device according to an embodiment.

[0020] Figure 3C This is a cross-sectional view schematically illustrating a third example of an elastic wave resonator constituting an elastic wave device according to an embodiment.

[0021] Figure 3D This is a cross-sectional view schematically illustrating the fourth example of an elastic wave resonator constituting an elastic wave device according to the embodiment.

[0022] Figure 4 This is an enlarged cross-sectional view of the via conductor and its surrounding area of ​​the elastic wave device involved in the embodiment.

[0023] Figure 5 This is a cross-sectional view showing an example of the laminated structure of the metal film constituting the elastic wave device according to the embodiment.

[0024] Figure 6 This is an enlarged cross-sectional view of the laminated interface of the metal film of the elastic wave device according to the embodiment.

[0025] Figure 7 This is a cross-sectional view of the elastic wave device according to a variation of embodiment 1.

[0026] Figure 8 This is a first top view of the elastic wave device according to a variation of the embodiment 1.

[0027] Figure 9 This is a cross-sectional view showing the support portion of the hardness measuring point.

[0028] Figure 10A This is a schematic cross-sectional view showing the interface between the via conductor and the first substrate of the elastic wave device according to the embodiment.

[0029] Figure 10B This is a SEM image showing the interface between the via conductor and the first substrate of the elastic wave device according to the embodiment.

[0030] Figure 11A This is a cross-sectional view of the elastic wave device involved in the modified embodiment 2.

[0031] Figure 11B This is a cross-sectional view of the elastic wave device involved in variation 3 of the embodiment.

[0032] Figure 11C This is a cross-sectional view of the elastic wave device involved in variation 4 of the implementation.

[0033] Figure 11D This is a cross-sectional view of the elastic wave device involved in variation 5 of the embodiment.

[0034] Figure 12 This is a cross-sectional view showing the laminated structure of the metal film of the elastic wave device according to Modified Example 6 of the embodiment.

[0035] Figure 13 This is a cross-sectional view showing the laminated structure of the metal film constituting the elastic wave device involved in the comparative example. Detailed Implementation

[0036] Hereinafter, embodiments of the present disclosure will be described in detail using the accompanying drawings. Furthermore, the embodiments described below are either general or specific examples. The numerical values, shapes, materials, constituent elements, arrangements of constituent elements, and connection methods shown in the following embodiments are examples and are not intended to limit the invention. Constituent elements in the following embodiments not described in the independent claims are described as arbitrary constituent elements. Moreover, the sizes or size ratios of the constituent elements shown in the drawings are not necessarily strict.

[0037] Furthermore, the figures are schematic diagrams that have been appropriately emphasized, omitted, or proportionally adjusted for the purpose of illustrating the invention, and are not necessarily strictly illustrative, sometimes differing from the actual shapes, positional relationships, and proportions. In the figures, substantially identical structures are labeled with the same reference numerals, and sometimes repeated descriptions are omitted or simplified.

[0038] In the circuit structure disclosed herein, the term "connection" includes not only direct connections using electrodes and / or wiring conductors, but also electrical connections via matching elements such as inductors and capacitors, and switching circuits. The term "connection between A and B" means a connection between A and B that is made between A and B.

[0039] In addition, terms such as "parallel" and "perpendicular" that indicate the relationship between elements, terms such as "rectangle" that indicate the shape of elements, and numerical ranges that do not only indicate strictness but also imply substantially equal ranges, such as including a few percent degree of error.

[0040] (Implementation Method)

[0041] [1. Construction of elastic wave device 1]

[0042] Figure 1 This is a cross-sectional view of the elastic wave device 1 according to the embodiment. Figure 2A This is a first top view of the elastic wave device 1 according to the embodiment. Figure 2B This is a second top view of the elastic wave device 1 according to the embodiment. Figure 2C This is a third top view of the elastic wave device 1 according to the embodiment. Figure 2A This is a top view (perspective) of the main surface 20a of the substrate 20 from the z-axis. Figure 2B This is a top view (perspective) of the main surface 10a of the substrate 10 from the z-axis positive side. Figure 2C This is a top view of the main surface 10b of the substrate 10 from the z-axis positive side. Figure 1 yes Figure 2A , Figure 2B as well as Figure 2C A cross-sectional view at line II.

[0043] like Figures 1-2C As shown, the elastic wave device 1 includes substrates 10 and 20, metal films 31, 32 and 33, functional electrode 34, via conductor 11, insulating films 13 and 23, planar electrode 12 and bump electrode 40.

[0044] The substrate 10 is an example of a first substrate, having opposing main surfaces 10a (first main surface) and 10b (second main surface). In this embodiment, the substrate 10 contains silicon.

[0045] Substrate 20 is an example of a second substrate, having opposing main surfaces 20a (third main surface) and 20b. Main surfaces 10a and 20a face each other. In this embodiment, substrate 20 is piezoelectric.

[0046] like Figure 1 As shown, the via conductor 11 is an electrode disposed on the substrate 10 from the main surface 10a toward the main surface 10b. In this embodiment, the via conductor 11 is a through electrode that fills a hole penetrating the substrate 10 between the main surface 10a and the main surface 10b. The via conductor 11 is, for example, made of a metal component with Cu (copper) as the main component.

[0047] Alternatively, the via conductor 11 may not be a single via conductor extending from the main surface 10a to the main surface 10b, but may have a structure in which multiple via conductors are connected via planar electrodes formed in the substrate 10.

[0048] Metal film 31 is an example of the first metal film, such as Figure 1 as well as Figure 2B As shown, a planar electrode is disposed on the main surface 10a and connected to the via conductor 11. The metal film 31 is, for example, a stack of multiple metal layers. Furthermore, for a specific example of the stacked structure of the metal film 31, using... Figure 5 Please provide an explanation.

[0049] Metal film 32 is an example of the second metal film, such as Figure 1 as well as Figure 2B As shown, a planar electrode is disposed on the side opposite to the via conductor 11, sandwiching a metal film 31 and in contact with the metal film 31. The metal film 32 is, for example, a stack of multiple metal layers. Furthermore, for a specific example of the stacked structure of the metal film 32, using... Figure 5 Please provide an explanation.

[0050] Metal film 33 is an example of the third metal film, such as Figure 1 as well as Figure 2A As shown, a planar electrode is disposed on the main surface 20a, connected to the functional electrode 34, and in contact with the metal film 32. The metal film 33 is, for example, a stack of multiple metal layers. Furthermore, for a specific example of the stacked structure of the metal film 33, using... Figure 5 Please provide an explanation.

[0051] Functional electrode 34 is disposed on main surface 20a and performs electromechanical conversion together with substrate 20. For an example of the structure of functional electrode 34 and metal film 33, using... Figures 3A-3C Please provide an explanation.

[0052] like Figure 1 As shown, metal films 31, 32 and 33 constitute a support portion, which are stacked sequentially between the main surface 10a and the main surface 20a, and are configured to provide space between the main surface 10a and the main surface 20a.

[0053] Insulating film 13 is disposed on main surface 10b, for example, a silicon oxide film. Insulating film 23 is disposed on main surface 20a, for example, a silicon oxide film. Alternatively, at least one of insulating film 13 and 23 may be omitted.

[0054] [2 Structure of substrate 20, functional electrode 34 and metal film 33]

[0055] Next, an example of the structure of the substrate 20, the functional electrode 34, and the metal film 33 will be described. Figure 3A These are schematic top and cross-sectional views illustrating a first example of the elastic wave resonator 60 constituting the elastic wave device 1 according to the embodiment. The basic structure of the elastic wave resonator 60 constituting the elastic wave device 1 is illustrated in these figures. Furthermore, Figure 3A The elastic wave resonator 60 shown is used to illustrate a typical structure of the elastic wave resonator constituting the elastic wave device 1. The number and length of the electrode fingers constituting the electrodes are not limited thereto.

[0056] The elastic wave resonator 60 is composed of a substrate 20 and comb-shaped electrodes 60a and 60b.

[0057] like Figure 3A As shown in (a), a pair of comb-shaped electrodes 60a and 60b are formed on the substrate 20, facing each other. The comb-shaped electrode 60a is composed of a plurality of parallel electrode fingers 61a (first electrode fingers) and a busbar electrode 62a (first busbar electrode) connecting one end of each of the plurality of electrode fingers 61a to each other. Furthermore, the comb-shaped electrode 60b is composed of a plurality of parallel electrode fingers 61b (second electrode fingers) and a busbar electrode 62b (second busbar electrode) connecting one end of each of the plurality of electrode fingers 61b to each other. The plurality of electrode fingers 61a and 61b are formed in a direction orthogonal to the direction of elastic wave propagation (X-axis direction). The busbar electrode 62a and busbar electrode 62b are arranged opposite each other, sandwiching the electrode fingers 61a and 61b. The comb-shaped electrodes 60a and 60b constitute an IDT (Interdigital Transducer) electrode 54.

[0058] Here, in the case where the elastic wave device 1 according to this embodiment uses IDT electrode 54 for electromechanical conversion, Figure 1 as well as Figure 2A The functional electrode 34 shown includes multiple electrode fingers 61a and multiple electrode fingers 61b. Furthermore, Figure 1 as well as Figure 2A The metal film 33 shown includes busbar electrodes 62a and 62b.

[0059] Alternatively, the elastic wave resonator 60 may also have reflectors at both ends of the IDT electrode 54 in the direction of elastic wave propagation (X-axis direction).

[0060] like Figure 3A As shown in (b), the IDT electrode 54 is, for example, a stacked structure of a close-fitting layer 540 and a main electrode layer 542.

[0061] The bonding layer 540 is used to improve the adhesion between the substrate 20 and the main electrode layer 542, and is made of materials such as Ti. The main electrode layer 542 is made of Al containing 1% Cu, for example. The protective layer 55 is formed to cover the comb electrodes 60a and 60b. The protective layer 55 is a layer intended to protect the main electrode layer 542 from the influence of the external environment, adjust the frequency and temperature characteristics, and improve moisture resistance, and is, for example, a dielectric film with silicon dioxide as the main component.

[0062] Furthermore, the materials constituting the bonding layer 540, the main electrode layer 542, and the protective layer 55 are not limited to the materials described above. Also, the IDT electrode 54 may not be of the aforementioned multilayer structure. For example, the IDT electrode 54 may be made of metals or alloys such as Ti, Al, Cu, Pt, Au, Ag, and Pd. Alternatively, it may be composed of multiple laminates made of the aforementioned metals or alloys. Furthermore, the protective layer 55 may not be formed.

[0063] Next, the laminated structure of substrate 20 will be described.

[0064] like Figure 3A As shown in (c), the substrate 20 has a support substrate 51, an intermediate layer 52 and a piezoelectric film 53, and has a structure in which the support substrate 51, the intermediate layer 52 and the piezoelectric film 53 are stacked in sequence.

[0065] The piezoelectric film 53 may include, for example, a θ° Y-cut LiTaO3 piezoelectric single crystal or piezoelectric ceramic (a lithium tantalate single crystal or ceramic whose surface acoustic wave propagates in the X-axis direction is a single crystal or ceramic whose normal is a plane rotated θ° from the Y-axis with the X-axis as the central axis). Furthermore, the material of the piezoelectric single crystal used as the piezoelectric film 53 and the cutting angle θ are appropriately selected according to the requirements and specifications of each filter.

[0066] The support substrate 51 is a substrate that supports the intermediate layer 52, the piezoelectric film 53, and the IDT electrode 54. Furthermore, the support substrate 51 can also be a substrate where the velocity of the bulk wave is higher than that of elastic waves such as surface waves and boundary waves propagating in the piezoelectric film 53, thus functioning to confine surface acoustic waves within the portion where the piezoelectric film 53 and the intermediate layer 52 are stacked, preventing leakage to the lower part of the support substrate 51. As materials for the support substrate 51, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, bauxite, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, forsterite, spinel, sialon, and other ceramics, alumina, silicon oxynitride, DLC (diamond-like carbon), diamond, and other dielectrics, or semiconductors such as silicon, or materials with the above materials as the main component, can be used. Furthermore, the aforementioned spinels contain aluminum compounds, which contain one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of the aforementioned spinels include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0067] Intermediate layer 52, for example, is a film in which the velocity of the bulk wave in intermediate layer 52 is lower than that of the bulk wave propagating in piezoelectric film 53, and is disposed between piezoelectric film 53 and support substrate 51. Through this structure and the property that the energy of the elastic wave is essentially concentrated in a medium with a low velocity of sound, leakage of surface acoustic wave energy to the outside of the IDT electrode is suppressed. As a material for intermediate layer 52, for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds containing fluorine, carbon, or boron in silicon oxide, or materials mainly composed of the aforementioned materials, can be used.

[0068] Furthermore, based on the above-described laminated structure of substrate 20, compared to the conventional structure that uses a single layer of piezoelectric substrate, the resonant frequency and the Q value at the anti-resonant frequency can be significantly improved. That is, a high-Q elastic wave resonator can be constructed, and therefore, using this elastic wave resonator, a filter with low insertion loss can be constructed.

[0069] Alternatively, the support substrate 51 may also have a structure in which the support substrate and a hypersonic film, whose sound velocity of the propagating bulk wave is higher than that of elastic waves such as surface waves and boundary waves propagating in the piezoelectric film 53, are stacked. In this case, the same material as the support substrate 51 can be used as the material of the hypersonic film. In addition, as the material of the support substrate, for example, ceramics such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and forsterite, diamond, glass, and other dielectrics, silicon, gallium nitride, and other semiconductors, or resins, or materials mainly composed of the above materials can be used.

[0070] The wavelength λ of the elastic wave harmonic oscillator 60 is composed of... Figure 3A The repetition period of the plurality of electrode fingers 61a or 61b of the IDT electrode 54 shown in (b) is defined. Furthermore, the electrode finger spacing p is half the wavelength λ, and is defined by (W+S) when the linewidth of the electrode fingers 61a and 61b constituting the comb electrodes 60a and 60b is set to W, and the space width between adjacent electrode fingers 61a and 61b is set to S. Furthermore, the electrode finger duty cycle D of the IDT electrode 54 is the linewidth occupancy rate of the electrode fingers 61a and 61b, and is the ratio of the linewidth W to the sum of the linewidth and the space width S, defined by W / (W+S). Additionally, in the IDT electrode 54, when the spacing between adjacent electrode fingers is not fixed, the electrode finger spacing p of the IDT electrode 54 is determined by the average electrode finger spacing p of the IDT electrode 54. AVE Definition. If the total number of electrode fingers 61a and 61b contained in the IDT electrode 54 is set as Ni, and the distance between the centers of the electrode fingers at one end of the IDT electrode 54 located in the direction of elastic wave propagation and the electrode fingers at the other end is set as Di, then the average electrode finger spacing p of the IDT electrode 54 is defined. AVE Defined as Di / (Ni-1). Furthermore, in the IDT electrode 54, when the electrode finger duty cycle D is not fixed, the electrode finger duty cycle D of the IDT electrode 54 is determined by the average electrode finger duty cycle D0 of the IDT electrode 54. AVE Definition. Let the total number of electrode fingers 61a and 61b included in the IDT electrode 54 be Ni, and the sum of the linewidths W of (Ni-1) electrode fingers be W. ALL Let the total space width S be the sum of the (Ni-1) space widths S contained in the IDT electrode 54. ALL In this case, the average electrode index duty cycle D of IDT electrode 54 AVE By W ALL / (W) ALL +S ALL )definition.

[0071] In addition, the distance p between the electrode fingers of the comb-shaped electrode of the IDT electrode 54 can be measured by viewing the main surface of the substrate on which the comb-shaped electrode of the IDT electrode 54 is formed from above, and / or by cross-sectioning a section perpendicular to the extension direction of the electrode fingers using a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), or a transmission electron microscope (TEM), thereby measuring the linewidth L and the spatial width S.

[0072] Furthermore, in this specification, the term "main component of the material" refers to a component that accounts for more than 50% by weight in the material. The aforementioned main component may exist in any of the following states: single crystal, polycrystalline, and amorphous, or a mixture thereof.

[0073] Figure 3B This is a schematic cross-sectional view illustrating a second example of the elastic wave resonator 60 constituting the elastic wave device 1 according to the embodiment. Figure 3A The elastic wave resonator 60 shown illustrates an example where the IDT electrode 54 is formed on a substrate 20 having a piezoelectric film 53. However, the substrate on which the IDT electrode 54 is formed can also be as follows: Figure 3B The piezoelectric single crystal substrate 57 shown contains a single piezoelectric layer.

[0074] The piezoelectric single crystal substrate 57 is, for example, made of a piezoelectric single crystal of LiNbO3. The elastic wave resonator involved in this example is composed of a LiNbO3 piezoelectric single crystal substrate 57, an IDT electrode 54, and a protective layer 58 formed on the piezoelectric single crystal substrate 57 and the IDT electrode 54.

[0075] The piezoelectric film 53 and the piezoelectric single crystal substrate 57 described above can also be appropriately modified in terms of their characteristics, etc., according to the requirements of the elastic wave device 1. Even if an elastic wave resonator using a LiTaO3 piezoelectric substrate or the like with a cut angle other than the aforementioned cut angle is used, the same effect as the elastic wave resonator 60 using the piezoelectric film 53 described above can be achieved.

[0076] Furthermore, the piezoelectric substrate forming the IDT electrode 54 may also have a structure in which a support substrate, an energy-sealing layer, and a piezoelectric film are sequentially stacked. The IDT electrode 54 is formed on the piezoelectric film. The piezoelectric film may be, for example, a LiTaO3 piezoelectric single crystal or a piezoelectric ceramic. The support substrate is a substrate that supports the piezoelectric film, the energy-sealing layer, and the IDT electrode 54.

[0077] The energy-sealing layer comprises one or more layers, wherein the velocity of bulk acoustic waves propagating in at least one layer is greater than the velocity of elastic waves propagating near the piezoelectric film. For example, the energy-sealing layer can also be a stacked structure of low-velocity and high-velocity layers. The low-velocity layer is a film in which the velocity of bulk waves is lower than the velocity of elastic waves propagating in the piezoelectric film. The high-velocity layer is a film in which the velocity of bulk waves is higher than the velocity of elastic waves propagating in the piezoelectric film. Alternatively, the support substrate can also be a high-velocity layer.

[0078] In addition, the energy sealing layer can also be an acoustic impedance layer with a structure that alternately stacks low acoustic impedance layers with relatively low acoustic impedance and high acoustic impedance layers with relatively high acoustic impedance.

[0079] also, Figure 3C This is a schematic cross-sectional view illustrating a third example of the elastic wave resonator 60 constituting the elastic wave device 1 according to the embodiment. Figure 3C In the figure, a bulk acoustic resonator is shown as the elastic wave resonator of the elastic wave device 1. As shown in the figure, the bulk acoustic resonator has, for example, a support substrate 65, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68, and is structured by sequentially stacking the support substrate 65, the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68.

[0080] The support substrate 65 is a substrate used to support the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68; for example, it is a silicon substrate. Furthermore, the support substrate 65 has a cavity in the area that contacts the lower electrode 66. This allows the piezoelectric layer 67 to vibrate freely.

[0081] The lower electrode 66 is an example of a first planar electrode and is formed on one surface of the support substrate 65. The upper electrode 68 is an example of a second planar electrode and is formed on one surface of the support substrate 65. The lower electrode 66 and the upper electrode 68 are, for example, made of Al containing 1% Cu.

[0082] The piezoelectric layer 67 is an example of a piezoelectric thin film, formed between the lower electrode 66 and the upper electrode 68. The piezoelectric layer 67 may contain at least one of ZnO (zinc oxide), AlN (aluminum nitride), PZT (lead zirconate titanate), KN (potassium niobate), LN (lithium niobate), LT (lithium tantalate), quartz, and LiBO (lithium borate) as the main component.

[0083] The bulk acoustic wave resonator with the above-described stacked structure induces bulk acoustic waves and generates resonance within the piezoelectric layer 67 by applying electrical energy between the lower electrode 66 and the upper electrode 68. The bulk acoustic waves generated by this resonator propagate between the lower electrode 66 and the upper electrode 68 in a direction perpendicular to the film surface of the piezoelectric layer 67. In other words, the bulk acoustic wave resonator is a resonator that utilizes bulk acoustic waves.

[0084] Here, in the case where the elastic wave device 1 according to this embodiment uses bulk acoustic waves for electromechanical conversion, Figure 1 as well as Figure 2A The functional electrode 34 shown includes a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68. Furthermore, Figure 1 as well as Figure 2A The substrate 20 shown may also be non-piezoelectric and include a support substrate 65.

[0085] Figure 3DThis is a cross-sectional view schematically illustrating a fourth example of the elastic wave resonator 60 constituting the elastic wave device 1 according to the embodiment. In the elastic wave device 1 of this example, the substrate 20 has a supporting substrate 51, an intermediate layer 52, a gap 160, and a piezoelectric film 53.

[0086] In this example, when viewed from above on the main surface 20a, the elastic wave device 1 has a gap 160 between the piezoelectric film 53 and the support substrate 51 in the region overlapping with the IDT electrode 54. Furthermore, when the thickness of the piezoelectric film 53 (in the z-axis direction) is set as d and the electrode finger spacing of the IDT electrode 54 is set as p, the normalized film thickness d / p of the piezoelectric film 53 is 0.5 or less.

[0087] By having a normalized film thickness d / p of piezoelectric film 53 of 0.5 or less and by providing a gap 160, the elastic wave resonator 60 is configured as a laterally excited bulk acoustic resonator (XBAR). By having a normalized film thickness d / p of piezoelectric film 53 of 0.5 or less, the fractional bandwidth of the elastic wave resonator 60 can be increased, enabling the configuration of a resonator with a high electromechanical coupling coefficient.

[0088] Furthermore, it is even more preferable to set the normalized film thickness d / p of the piezoelectric film 53 to 0.24 or less. This allows the fractional bandwidth of the elastic wave resonator 60 to be set to 7% or more.

[0089] In addition, the electrode finger duty cycle D and the normalized film thickness d / p of the IDT electrode 54 preferably satisfy the relationship of Equation 1.

[0090] D≤1.75(d / p)+0.075 (Equation 1)

[0091] Therefore, the spurious signals of higher-order modes in XBAR can be effectively reduced. Specifically, by setting the fractional bandwidth of XBAR (the value obtained by dividing the difference between the anti-resonant frequency and the resonant frequency by the average frequency of the anti-resonant frequency and the resonant frequency) to 17% or less, the spurious signals of higher-order modes can be suppressed and contained within the passband.

[0092] Furthermore, the electrode finger duty cycle D and the normalized film thickness d / p of the IDT electrode 54 more preferably satisfy the relationship of Equation 2.

[0093] D≤1.75(d / p)+0.05 (Equation 2)

[0094] Therefore, the fractional bandwidth of XBAR can be reliably set to below 17%, thus avoiding the inclusion of spurious higher-order modes in the passband.

[0095] Furthermore, the piezoelectric film 53 preferably comprises lithium niobate or lithium tantalate, and the Euler angles (θ1, θ2, θ3) of the lithium niobate or lithium tantalate constituting the piezoelectric film 53 are within the range of Equation 3, Equation 4, Equation 5 or Equation 6 below.

[0096] -10°≤θ1≤10°, and 0°≤θ2≤20° (Equation 3)

[0097] -10°≤θ1≤10°, and 20°≤θ2≤80°, and 0°≤θ3≤60° (1-(θ2-50)) 2 / 900) 1 / 2 (Equation 4)

[0098] -10°≤θ1≤10°, and 20°≤θ2≤80°, and [180°-60°(1-(θ2-50)] 2 / 900) 1 / 2 )]≤θ3≤180° (Equation 5)

[0099] -10°≤θ1≤10°, and [180°-30°(1-(θ3-90) 2 / 8100) 1 / 2 )]≤θ2≤180° (Equation 6)

[0100] By specifying the Euler angle of the piezoelectric film 53, which is made of lithium niobate or lithium tantalate, as described above, the fractional bandwidth of the elastic wave harmonic oscillator 60 can be set to 5% or more.

[0101] Alternatively, in the elastic wave device 1 of the fourth example, an energy-sealing layer comprising a low acoustic impedance layer and a high acoustic impedance layer can be used instead of the void 160. Specifically, an energy-sealing layer with a structure in which a low acoustic impedance layer with relatively low acoustic impedance and a high acoustic impedance layer with relatively high acoustic impedance are alternately stacked can be disposed between the piezoelectric film 53 and the support substrate 51. Alternatively, the energy-sealing layer can be a stacked structure of a low-velocity film and a high-velocity film. A low-velocity film is a film in which the velocity of the bulk wave in the low-velocity film is lower than the velocity of the bulk sound wave propagating in the piezoelectric film 53. A high-velocity film is a film in which the velocity of the bulk wave in the high-velocity film is higher than the velocity of the elastic wave propagating in the piezoelectric film 53. By having a normalized film thickness d / p of 0.5 or less for the piezoelectric film 53 and by providing an energy-sealing layer, the elastic wave resonator 60 is configured as an XBAR.

[0102] [3. Bonding structure of substrate 10, via conductor 11 and metal films 31-33]

[0103] Next, the bonding structure of the substrate 10, the via conductor 11, and the metal films 31 to 33 will be described. Figure 4This is an enlarged cross-sectional view of the through-hole conductor 11 and its surrounding area in the elastic wave device 1 according to the embodiment. This figure is... Figure 1 The image shows a microscope image of region IV. As shown in the figure, a via conductor 11 is formed inside the substrate 10. A planar electrode 12 is bonded to the upper (positive z-axis) opening of the via conductor 11, and a metal film 31 is bonded to the lower (negative z-axis) opening of the via conductor 11. Furthermore, a metal film 32, a metal film 33, and the substrate 20 are sequentially bonded to the negative z-axis side of the metal film 31.

[0104] Here, as Figure 2B As shown, in the top view of the main plane 10a, ( Figure 2B The area of ​​the metal film 31 in the upper right corner contains ( Figure 2B The area of ​​the via conductor 11 in the upper right corner, and ( Figure 2B The area of ​​the metal film 31 in the upper right corner is greater than ( Figure 2B The area of ​​the via conductor 11 in the upper right corner. Furthermore, in the top view of the main surface 10a, ( Figure 2B The area of ​​the metal film 32 in the upper right corner contains ( Figure 2B The area of ​​the via conductor 11 in the upper right corner, and ( Figure 2B The area of ​​the metal film 32 in the upper right corner is greater than ( Figure 2B The area of ​​the via conductor 11 in the upper right corner.

[0105] In other words, such as Figure 4 As shown, in the direction perpendicular to the main surface 10a (z-axis direction) and through the cut surface of the via conductor 11 ( Figures 2A to 2C In section II, the length L of the metal film 31 31 The length D of the via conductor 11 is greater than 11 (Diameter), and the length L of the metal film 32 32 The length D of the via conductor 11 is greater than 11 (diameter).

[0106] When viewed from the top of the main surface 10a, if the regions of metal films 31 and 32 are included within the region of via conductor 11, the compressive stress of metal films 31 and 32 will be entirely applied to via conductor 11, potentially causing deformation of via conductor 11 or peeling of via conductor 11 from substrate 10. In contrast, according to the structure of the elastic wave device 1 according to this embodiment, when viewed from the top of the main surface 10a, the region of via conductor 11 is included within the regions of metal films 31 and 32, the area of ​​metal film 31 is larger than the area of ​​via conductor 11, and the area of ​​metal film 32 is larger than the area of ​​via conductor 11. Therefore, since the substrate 10 adjacent to via conductor 11 in the x-axis direction is bonded to metal film 31, the substrate 10 bonded to metal film 31 absorbs the compressive stress of metal films 31 and 32, thereby suppressing deformation and peeling of via conductor 11. In other words, it promotes the fixation of via conductor 11. Furthermore, because the metal films 32 and 33 are bonded together, and the metal film 33 is bonded to the substrate 20, the compressive stress generated in the metal films 31 and 32 can be dispersed towards the substrate 20 side. Therefore, an elastic wave device 1 with improved bonding strength of the via conductor 11 can be provided.

[0107] Furthermore, in this specification, the term "region A includes region B" is defined as all regions of region B being configured within region A.

[0108] Next, the bonding state between the via conductor 11 and the substrate 10 will be described. Figure 10A This is a cross-sectional schematic diagram showing the interface between the via conductor 11 and the substrate 10 of the elastic wave device 1 according to the embodiment. Figure 10B This is a SEM image showing the interface between the via conductor 11 and the substrate 10 of the elastic wave device 1 according to the embodiment. Figure 10A It is a schematic enlargement Figure 4 A cross-sectional view of region X.

[0109] The problem arises from the process of forming cylindrical voids in the substrate 10 to fill the via conductors 11 in the Si-based substrate 10. In this process, a shell-like uneven structure, known as a scallop, is created on the inner wall of the cylindrical voids in the substrate 10. If the tip of the scallop becomes sharp, the resistance at the tip of the uneven structure increases, making it prone to overheating, and thus reducing the bonding strength of the via conductors 11.

[0110] In the elastic wave device 1 according to this embodiment, the PV (Peak to Valley) value of the arc-shaped cut residual uneven structure is preferably 100 μm or less. Furthermore, the PV value is defined as the height difference between the highest point of the convex portion and the lowest point of the valley portion of the uneven structure. In the elastic wave device 1 according to this embodiment, as... Figure 10A as well as Figure 10B As shown, the top of the protrusion of the arc-shaped cut residual uneven structure is flattened. Accordingly, the resistance at the top of the aforementioned uneven structure can be reduced, thereby suppressing heat generation. Furthermore, the generation of voids at the interface between the via conductor 11 and the substrate 10 can be suppressed, thus improving the bonding strength of the via conductor 11.

[0111] Next, the layered structure of metal films 31 to 33 will be described. Figure 5 This is a cross-sectional view showing an example of the laminated structure of the metal films 31-33 constituting the elastic wave device 1 according to the embodiment. The figure is schematically enlarged. Figure 4 A cross-sectional view of region V.

[0112] like Figure 5 As shown, the metal film 31 has an intermediate layer 316, an intermediate layer 315, a main electrode layer 314, an intermediate layer 313, an intermediate layer 312, and a bonding layer 311 from the main surface 10a side.

[0113] Intermediate layer 313 (first intermediate layer) and intermediate layer 316 are, for example, metal layers with Ti (titanium) as the main component, and function as diffusion prevention layers.

[0114] Intermediate layers 312 and 315 are, for example, metal layers with Pt (platinum) as the main component, and together with intermediate layers 313 and 316, they function as diffusion prevention layers.

[0115] The main electrode layer 314 is an example of the first main electrode layer, such as a metal layer mainly composed of Al (aluminum) and Cu (copper), which functions as the main medium for transmitting high-frequency signals in the metal film 31.

[0116] The bonding layer 311 is an example of the first bonding layer, such as a metal layer with Au (gold) as the main component, which has the function of being electrically and mechanically bonded to the metal film 32.

[0117] Alternatively, the metal film 31 described in this embodiment may not include the intermediate layers 312 and 315. Furthermore, the metal film 31 may consist solely of the main electrode layer 314.

[0118] In addition, such as Figure 5 As shown, the metal film 32 has a bonding layer 321, an intermediate layer 322, an intermediate layer 323, a main electrode layer 324, and an intermediate layer 325 from the main surface 10a side.

[0119] The bonding layer 321 is an example of the second bonding layer, such as a metal layer with Au (gold) as the main component, which has the function of being electrically and mechanically bonded to the metal film 31.

[0120] Intermediate layer 322 is, for example, a metal layer with Pt (platinum) as the main component, which together with intermediate layer 323 functions as a diffusion prevention layer.

[0121] Intermediate layer 323 (second intermediate layer) and intermediate layer 325 are, for example, metal layers with Ti (titanium) as the main component, and function as diffusion prevention layers.

[0122] The main electrode layer 324 is an example of the second main electrode layer, such as a metal layer mainly composed of Al (aluminum) and Cu (copper), which functions as the main medium for transmitting high-frequency signals in the metal film 32.

[0123] Alternatively, the intermediate layer 322 may be omitted from the metal film 32 described in this embodiment. Furthermore, the metal film 32 may consist solely of the main electrode layer 324.

[0124] In addition, such as Figure 5 As shown, the metal film 33 has an intermediate layer 331, a main electrode layer 332 and an intermediate layer 333 from the main surface 10a side.

[0125] Intermediate layers 331 and 333 are, for example, metal layers with Ti (titanium) as the main component, which function as diffusion prevention layers.

[0126] The main electrode layer 332 is, for example, a metal layer with Al (aluminum) and Cu (copper) as the main components, and functions as the main medium for transmitting high-frequency signals in the metal film 33.

[0127] Alternatively, the metal film 33 in this embodiment may not have intermediate layers 331 and 333, and the metal film 33 may consist only of the main electrode layer 332.

[0128] Figure 5 The main electrode layer 332 in the middle is, for example, equivalent to Figure 3A The main electrode layer 542 in the middle, Figure 5 The intermediate layer 333 in the middle is equivalent to, for example, the middle layer 333 in the middle layer 33 Figure 3A The dense layer 540 in the middle.

[0129] Furthermore, the size relationship of the area (and length) of the metal layers constituting each metal film is not limited to... Figure 5 The diagram shows the size relationship of the areas (and lengths) of each metal layer. For the size relationship of the areas (and lengths) of each metal layer, use... Figure 6 Please provide an explanation.

[0130] In addition, such as Figure 2B As shown, in the top view of the main plane 10a, ( Figure 2B The area of ​​the metal film 31 in the upper right corner contains ( Figure 2B The area of ​​the metal film 32 in the upper right corner, and ( Figure 2BThe area of ​​the metal film 31 in the upper right corner is greater than ( Figure 2B The area of ​​the metal film 32 in the upper right corner.

[0131] In other words, such as Figure 4 As shown, in the direction perpendicular to the main surface 10a (z-axis direction) and through the cut surface of the via conductor 11 ( Figures 2A to 2C In section II, the length L of the metal film 31 31 The length L greater than 32 of the metal film 32 .

[0132] Accordingly, the end shape of the metal film 31 will not be deformed due to the bonding of the metal film 32. Therefore, the bonding of the substrate 10 and the metal film 31 can promote the reduction of compressive stress applied to the via conductor 11.

[0133] In addition, the hardness of metal film 32 is higher than that of metal film 31.

[0134] When two metal films are joined, if the smaller metal film has low hardness, it will be flattened during the crimping process and protrude from the end of the joint interface. The joint will be locally heated due to the metal film protruding from the end, thus deteriorating the joint. In addition, the metal film protruding from the end becomes useless particles.

[0135] In contrast, according to the elastic wave device 1 of this embodiment, when viewed from above the main surface 10a, the hardness of the smaller metal film 32 is higher than that of the larger metal film 31. Therefore, when the metal films 31 and 32 are pressed together, it is possible to prevent the smaller metal film 32 from being flattened, and to perform a joint in which the larger metal film 31 wraps around the smaller metal film 32. Thus, it is possible to suppress localized heating and the generation of unwanted particles at the joint interface, and to provide an elastic wave device 1 with improved joint strength of the support portion.

[0136] In addition, such as Figure 2A as well as Figure 2B As shown, when viewed from above the main surface 20a, the area of ​​the metal film 33 includes the area of ​​the metal film 32, and the area of ​​the metal film 33 is larger than the area of ​​the metal film 32.

[0137] In other words, such as Figure 4 As shown, in the direction perpendicular to the main surface 20a (z-axis direction) and through the cut surface of the via conductor 11 ( Figures 2A to 2C In section II, the length L of the metal film 33 33 The length L greater than 32 of the metal film 32 .

[0138] Accordingly, the metal film 32 does not limit the configuration area of ​​the functional electrode 34 and the metal film 33 on the main surface 20a, and can prioritize the configuration layout of the functional electrode 34 and the metal film 33.

[0139] In addition, the metal film 33 is preferably harder than the metal film 31.

[0140] Accordingly, a bonding method in which metal films 32 and 33 are wrapped with metal film 31 can be realized. Therefore, localized heating and the generation of unwanted particles at the joint interface end can be suppressed, and an elastic wave device 1 with improved joint strength of the support can be provided.

[0141] Furthermore, it is preferable that the element with the highest weight ratio among the metal elements constituting bonding layer 321 is the same as the element with the highest weight ratio among the metal elements constituting bonding layer 311. In this embodiment, bonding layers 311 and 321 are, for example, metal layers with Au as the main component. The element with the highest weight ratio (Au) in bonding layer 321 is the same as the element with the highest weight ratio (Au) in bonding layer 311.

[0142] Accordingly, by Au diffusion bonding, the bonding strength between metal film 31 and metal film 32 can be improved, thereby improving the strength of the support portion.

[0143] Furthermore, the grain size of preferred bonding layer 311 is approximately the same as the grain size of bonding layer 321.

[0144] When the grain size of bonding layers 311 and 321 is different, the lower-hardness metal film will deform during press bonding due to the different hardness of metal films 31 and 32, resulting in insufficient bonding strength. Conversely, if the grain size is the same, the hardness of the metal layers at the bonding interface is the same, so the metal film will not deform during press bonding, and sufficient bonding strength can be obtained.

[0145] Furthermore, the grain size of the metal layers can be classified, for example, according to ASTM E112-13, an international standard. Each metal layer is assigned a grain size number based on the average grain size specified by the aforementioned international standard. Here, metal layers with the same grain size number are considered to have the same grain size.

[0146] Furthermore, the surface roughness Ra of the bonding interface of bonding layers 311 and 321 is preferably less than 10 nm.

[0147] Accordingly, voids at the bonding interface of bonding layers 311 and 321 can be eliminated, thereby further improving the bonding strength of bonding layers 311 and 321.

[0148] Next, the conditions for improving the bonding strength of the metal films constituting the support portion will be explained. Figure 6 This is an enlarged cross-sectional view of the interface between the metal films 31 and 32 of the elastic wave device 1 according to the embodiment. The figure shows... Figure 4 The magnified microscope image of region VI. Additionally, in Figure 6 In the stacked structure of each metal film shown, intermediate layers 313 and 312 are shown as a single layer (referred to as intermediate layer 313 (312)), and intermediate layers 323 and 322 are shown as a single layer (referred to as intermediate layer 323 (322)). Alternatively, intermediate layers 312 and 322 may be omitted.

[0149] First, as mentioned above, in a top view of the main surface 10a, the region of the metal film 31 includes the region of the metal film 32, and the area of ​​the metal film 31 is larger than the area of ​​the metal film 32. Furthermore, as... Figure 6 As shown, in a top view of the main surface 10a, the region of the intermediate layer 323 (322) includes the region of the bonding layer 321, and the area of ​​the intermediate layer 323 (322) is larger than the area of ​​the bonding layer 321. Furthermore, in a top view of the main surface 10a, the region of the main electrode layer 324 includes the region of the intermediate layer 323 (322), and the area of ​​the main electrode layer 324 is larger than the area of ​​the intermediate layer 323 (322). In other words, as... Figure 6 As shown, in the direction perpendicular to the main surface 10a, and through the cut surfaces of the metal films 31 to 33 ( Figures 2A to 2C In section II, the length L of the intermediate layer 323 (322) is... 323 The length L of the bonding layer 321 is greater than 321 The length L of the main electrode layer 324 324 The length L is greater than that of the intermediate layer 323 (322). 323 .

[0150] Furthermore, the coefficient of linear expansion of the bonding layer 321 is greater than that of the intermediate layer 323 (322), and the coefficient of linear expansion of the main electrode layer 324 is greater than that of the bonding layer 321.

[0151] Based on the aforementioned stacking relationship of the metal layers constituting metal films 31 and 32, if metal films 31 and 32 are heated during press bonding, the area of ​​the main electrode layer 324, which has a relatively large coefficient of linear expansion, is larger than that of the intermediate layer 323 (322) and the bonding layer 321. Therefore, at the ends of the main electrode layer 324 and the intermediate layer 323 (322), the main electrode layer 324 and the intermediate layer 323 (322) have a bimetallic structure, and the main electrode layer 324 and the intermediate layer 323 (322) easily expand towards the bonding layer 321 (positive z-axis direction) at their ends. Thus, by pushing both ends of the main electrode layer 324 towards the metal film 31 (positive z-axis direction), a good bond can be obtained at the bonding end of the metal film 32.

[0152] In addition, the method for measuring the hardness of metal films 31 to 33 is explained in advance.

[0153] The hardness of metal films 31 to 33 can be measured, for example, using nanoindentation. Nanoindentation (NI) is a method in which an ultra-small indenter is pressed into the object being tested, and the hardness is determined by calculating the load-displacement curve of the object. Figure 9 This is a cross-sectional view showing the support portion for the hardness testing points. As shown in the figure, a miniature indenter is pressed into the hardness testing points on the sides of the metal films 31-33. An example of hardness testing data is shown in Table 1. The device used was a Bruker TriboIndenter TI980 (Japan), the testing mode (load time-hold time-unload time) was standard (5 sec-2 sec-5 sec), the indenter load was 400 μN, and there were 5 testing points per metal film.

[0154] [Table 1]

[0155]

[0156] Table 1 shows the results of measuring the hardness of the metal films 31 to 33 of the elastic wave device 1 using the NI method. It shows that the hardness of the metal film 32 is higher than that of the metal film 31, and the hardness of the metal film 33 is higher than that of the metal film 31.

[0157] Furthermore, the structure of the support portion of the elastic wave device 1 according to this embodiment is not limited to... Figure 1 The structure shown can also have the following... Figures 11A to 11D The structure shown.

[0158] Figure 11AThis is a cross-sectional view of the elastic wave device according to Embodiment Modification 2. The figure shows a cross-sectional view of a portion of the substrate 10, a portion of the substrate 20, and support portions 71 and 72, which include the elastic wave device according to this modification. As shown in the figure, the elastic wave device according to this modification includes substrates 10 and 20, a via conductor 11, and support portions 71 and 72. The support portion 71 has a metal film 31 disposed on the main surface 10a and not in contact with the via conductor 11, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. The support portion 72 has a metal film 31 disposed on the main surface 10a and in contact with the via conductor 11, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. In this modified example, the metal film 31 of the support portion 71 and the metal film 31 of the support portion 72 are separated, the metal film 32 of the support portion 71 and the metal film 32 of the support portion 72 are separated, and the metal film 33 of the support portion 71 and the metal film 33 of the support portion 72 are integrated.

[0159] Therefore, since the metal film 33 is shared by the support portions 71 and 72, the manufacturing process of the elastic wave device can be simplified.

[0160] Figure 11B This is a cross-sectional view of the elastic wave device according to Embodiment Modification 3. The figure shows a cross-sectional view of a portion of the substrate 10, a portion of the substrate 20, and support portions 71 and 72, which include the elastic wave device according to this modification. As shown in the figure, the elastic wave device according to this modification includes substrates 10 and 20, a via conductor 11, and support portions 71 and 72. The support portion 71 has a metal film 31 disposed on the main surface 10a and not in contact with the via conductor 11, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. The support portion 72 has a metal film 31 disposed on the main surface 10a and in contact with the via conductor 11, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. In this modified example, the metal film 31 of the support portion 71 and the metal film 31 of the support portion 72 are separated, the metal film 32 of the support portion 71 and the metal film 32 of the support portion 72 are integrated, and the metal film 33 of the support portion 71 and the metal film 33 of the support portion 72 are integrated.

[0161] Therefore, since the metal film 32 is shared by the support portions 71 and 72, and the metal film 33 is shared by the support portions 71 and 72, the manufacturing process of the elastic wave device can be simplified.

[0162] Figure 11CThis is a cross-sectional view of the elastic wave device according to Embodiment Modification 4. The figure shows a cross-sectional view of a portion of the substrate 10, a portion of the substrate 20, and support portions 71 and 72, which include the elastic wave device according to this modification. As shown in the figure, the elastic wave device according to this modification includes substrates 10 and 20, a via conductor 11, and support portions 71 and 72. The support portion 71 has a metal film 31 disposed on the main surface 10a, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. The support portion 72 has a metal film 31 disposed on the main surface 10a and in contact with the via conductor 11, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. In this modified example, the metal film 31 of the support portion 71 and the metal film 31 of the support portion 72 are integrated, the metal film 32 of the support portion 71 and the metal film 32 of the support portion 72 are integrated, and the metal film 33 of the support portion 71 and the metal film 33 of the support portion 72 are integrated.

[0163] Therefore, since the metal film 31 is shared by the support parts 71 and 72, the metal film 32 is shared by the support parts 71 and 72, and the metal film 33 is shared by the support parts 71 and 72, the manufacturing process of the elastic wave device can be simplified.

[0164] Figure 11D This is a cross-sectional view of the elastic wave device according to Embodiment Modification 5. The figure shows a cross-sectional view of a portion of the substrate 10, a portion of the substrate 20, and support portions 71 and 72, which include the elastic wave device according to this modification. As shown in the figure, the elastic wave device according to this modification includes substrates 10 and 20, a via conductor 11, and support portions 71 and 72. The support portion 71 has a metal film 31 disposed on the main surface 10a, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. The support portion 72 has a metal film 31 disposed on the main surface 10a and in contact with the via conductor 11, a metal film 33 disposed on the main surface 20a, and a metal film 32 disposed between the metal films 31 and 33. In this modified example, the metal film 31 of the support portion 71 and the metal film 31 of the support portion 72 are integrated, the metal film 32 of the support portion 71 and the metal film 32 of the support portion 72 are separated, and the metal film 33 of the support portion 71 and the metal film 33 of the support portion 72 are separated.

[0165] Therefore, since the metal film 31 is shared by the support portions 71 and 72, the manufacturing process of the elastic wave device can be simplified.

[0166] [4. Construction of the elastic wave device 1A in the modified example]

[0167] Figure 7 This is a cross-sectional view of the elastic wave device 1A according to a variation of the embodiment 1. Figure 8 This is a first top view of the elastic wave device 1A according to a variation of the embodiment 1. Figure 8 This is a view of the main surface 20a of the substrate 20 from the z-axis positive side (see-through). Additionally, in the elastic wave device 1A, a view of the main surface 10a of the substrate 10 from the z-axis positive side (see-through) is shown. Figure 2B The second top view is the same as the view of the main surface 10b of the substrate 10 viewed from the z-axis positive side. Figure 2C The third top view is the same. Figure 7 yes Figure 8 A sectional view at line VII-VII.

[0168] like Figure 7 as well as Figure 8 As shown, the elastic wave device 1A includes substrates 10 and 20, metal films 31, 32 and 33, functional electrode 34, via conductor 11, insulating films 13 and 23, planar electrode 12, and bump electrode 40. Compared to the elastic wave device 1 of the embodiment, the elastic wave device 1A according to this modification differs in the arrangement of the via conductor 11, metal films 31, 32, and 33. Hereinafter, regarding the elastic wave device 1A according to this modification, descriptions of structures identical to those in the elastic wave device 1 of the embodiment will be omitted, and the description will focus on the different structures.

[0169] Metal film 31 is an example of the first metal film, such as Figure 7 As shown, a planar electrode is disposed on the main surface 10a and connected to the via conductor 11. The metal film 31 is, for example, a stack of multiple metal layers.

[0170] Metal film 32 is an example of the second metal film, such as Figure 7 As shown, this is a planar electrode connected to the metal film 31. The metal film 32 is, for example, a stack of multiple metal layers.

[0171] Metal film 33 is an example of the third metal film, such as Figure 7 as well as Figure 8 As shown, a planar electrode is disposed on the main surface 20a, connected to the functional electrode 34, and in contact with the metal film 32. The metal film 33 is, for example, a stack of multiple metal layers.

[0172] Functional electrode 34 is disposed on main surface 20a and performs electromechanical conversion together with substrate 20.

[0173] like Figure 7 As shown, metal films 31, 32 and 33 constitute a support portion, which are stacked sequentially between the main surface 10a and the main surface 20a, and are configured to provide space between the main surface 10a and the main surface 20a.

[0174] exist Figure 7In the middle, the right via conductor 11 of the two via conductors 11 does not overlap with the functional electrode 34 when viewed from the top of the main surfaces 10a and 20a.

[0175] [5. Laminated structure of metal film in elastic wave device according to variation 6]

[0176] Compared with the elastic wave device 1 of the embodiment, the elastic wave device in Modification Example 6 differs only in the layered structure of the metal film constituting the support portion. Therefore, hereafter, regarding the elastic wave device of this modification example, the description of the same structure as the elastic wave device 1 of the embodiment will be omitted, and the description of the layered structure of the support portion that is different from that of the elastic wave device 1 of the embodiment will be provided.

[0177] Figure 12 This is a cross-sectional view showing the laminated structure of the metal films 31A to 33A of the elastic wave device according to Modified Example 6 of the embodiment. This figure is schematically enlarged. Figure 4 A cross-sectional view of region V.

[0178] like Figure 12 As shown, the support portion has a metal film 31A disposed on the main surface 10a, a metal film 33A disposed on the main surface 20a, and a metal film 32A disposed between the metal films 31A and 33A.

[0179] The metal film 31A has an intermediate layer 316, an intermediate layer 315, a main electrode layer 314A, an intermediate layer 313A, an intermediate layer 312, and a bonding layer 311 from the main surface 10a side.

[0180] Intermediate layer 313A and intermediate layer 316 are, for example, metal layers with Ti (titanium) as the main component, and function as the first diffusion prevention layer.

[0181] Intermediate layers 312 and 315 are, for example, metal layers with Pt (platinum) as the main component, and together with intermediate layers 313A and 316, they function as diffusion prevention layers.

[0182] The main electrode layer 314A is an example of the first main electrode layer, such as a metal layer mainly composed of Al (aluminum) and Cu (copper), which functions as the main medium for transmitting high-frequency signals in the metal film 31A.

[0183] The bonding layer 311 is an example of the first bonding layer, such as a metal layer with Au (gold) as the main component, which has the function of electrically and mechanically bonding well with the metal film 32A.

[0184] Alternatively, in the metal film 31A involved in this modified example, the intermediate layers 312 and 315 may be omitted.

[0185] In addition, such as Figure 12 As shown, the metal film 32A has a bonding layer 321, an intermediate layer 322, an intermediate layer 323A, a main electrode layer 324A, and an intermediate layer 325 from the main surface 10a side.

[0186] The bonding layer 321 is an example of the second bonding layer, such as a metal layer with Au (gold) as the main component, which has the function of being electrically and mechanically bonded to the metal film 31A.

[0187] Intermediate layer 322 is, for example, a metal layer with Pt (platinum) as the main component, and together with intermediate layer 323A, it functions as a second diffusion prevention layer.

[0188] Intermediate layer 323A (second intermediate layer) and intermediate layer 325 are, for example, metal layers with Ti (titanium) as the main component, and function as diffusion prevention layers.

[0189] The main electrode layer 324A is an example of the second main electrode layer, such as a metal layer mainly composed of Al (aluminum) and Cu (copper), which functions as the main medium for transmitting high-frequency signals in the metal film 32A.

[0190] Alternatively, in the metal film 32A involved in this modified example, the intermediate layer 322 may be omitted.

[0191] In addition, such as Figure 12 As shown, the metal film 33 has an intermediate layer 331, a main electrode layer 332 and an intermediate layer 333 from the main surface 10a side.

[0192] Intermediate layers 331 and 333 are, for example, metal layers with Ti (titanium) as the main component, which function as diffusion prevention layers.

[0193] The main electrode layer 332 is, for example, a metal layer with Al (aluminum) and Cu (copper) as the main components, and functions as the main medium for transmitting high-frequency signals in the metal film 33.

[0194] Alternatively, in the metal film 33A involved in this modified example, the intermediate layers 331 and 333 may be omitted, and the metal film 33A may be composed only of the main electrode layer 332.

[0195] In the metal film 31A, the angle θ2 formed by the side surface of the intermediate layer 313A and the first plane parallel to the main surface 10a is smaller than the angle θ1 formed by the side surface of the main electrode layer 314A and the first plane.

[0196] Accordingly, the exposed area of ​​the side of the intermediate layer 313A is increased, thus preventing the metal components of the bonding layer 311 and the main electrode layer 314A from being connected and alloyed (migrated) through the side of the intermediate layer 313A.

[0197] Furthermore, it is preferable that a portion of the side surface of the main electrode layer 314A is covered by the intermediate layer 313A. This further suppresses the metal components of the bonding layer 311 from bonding with and alloying (migrating) the metal components of the main electrode layer 314A. Additionally, it is preferable that a portion of the side surface of the main electrode layer 314A is covered by the intermediate layer 313A, while another portion of the side surface of the main electrode layer 314A is exposed and not covered by the intermediate layer 313A. This suppresses the formation of cracks in the main electrode layer 314A due to bonding stress with the intermediate layer 313A, thus preventing damage.

[0198] Furthermore, the area of ​​the interface between the main electrode layer 314A and the intermediate layer 313A is larger than the area of ​​the interface between the bonding layer 321 and the intermediate layer 313A.

[0199] In the metal film 32A, the angle θ4 formed by the side surface of the intermediate layer 323A and the first plane is smaller than the angle θ3 formed by the side surface of the main electrode layer 324A and the first plane.

[0200] Accordingly, the exposed area of ​​the side of the intermediate layer 323A is increased, thus preventing the metal components of the bonding layer 321 and the main electrode layer 324A from being connected and alloyed (migrated) through the side of the intermediate layer 323A.

[0201] Furthermore, it is preferable that a portion of the side surface of the main electrode layer 324A is covered by the intermediate layer 323A. This further suppresses the metal components of the bonding layer 321 from bonding with and alloying (migrating) the metal components of the main electrode layer 324A. Additionally, it is preferable that a portion of the side surface of the main electrode layer 324A is covered by the intermediate layer 323A, while another portion of the side surface of the main electrode layer 324A is exposed and not covered by the intermediate layer 323A. This suppresses the formation of cracks in the main electrode layer 324A due to bonding stress with the intermediate layer 323A, thus preventing damage.

[0202] Furthermore, the area of ​​the interface between the main electrode layer 324A and the intermediate layer 323A is larger than the area of ​​the interface between the bonding layer 321 and the intermediate layer 323A.

[0203] Figure 13 This is a cross-sectional view showing the laminated structure of the metal films 531A, 532A, and 33A constituting the elastic wave device according to the comparative example. Compared with the elastic wave device according to Modified Example 6, the elastic wave device according to this comparative example is only different in that metal films 531A and 532A are provided instead of metal films 31A and 32A.

[0204] The metal film 531A has intermediate layers 316, 315, 314A, 3131, 3132, 312 and 311 bonding layer from the main surface 10a side.

[0205] Intermediate layers 3131, 3132 and 316 are, for example, metal layers with Ti (titanium) as the main component.

[0206] In addition, such as Figure 13 As shown, the metal film 532A has a bonding layer 321, an intermediate layer 322, an intermediate layer 3231 and 3232, a main electrode layer 324A and an intermediate layer 325 from the main surface 10a side.

[0207] Intermediate layers 3231, 3232 and 325 are, for example, metal layers with Ti (titanium) as the main component.

[0208] In the metal film 531A, in order to suppress the alloying (migration) of the metal components of the bonding layer 311 and the main electrode layer 314A, the intermediate layers 3131 and 3132 are formed in two stages as diffusion prevention films. By making the film area of ​​the intermediate layer 3132 smaller than that of the intermediate layer 3131, steps are formed on the sides of the intermediate layers 3131 and 3132 to suppress the alloying (migration) of the metal components of the bonding layer 311 and the main electrode layer 314A.

[0209] Similarly, in the metal film 532A, in order to suppress the alloying (migration) of the metal components of the bonding layer 321 and the main electrode layer 324A, the intermediate layers 3231 and 3232 are formed in two stages as diffusion prevention films. By making the film area of ​​the intermediate layer 3231 smaller than that of the intermediate layer 3232, steps are formed on the sides of the intermediate layers 3131 and 3132 to suppress the alloying (migration) of the metal components of the bonding layer 321 and the main electrode layer 324A. However, in the elastic wave device of the comparative example, different film formation processes are required to form the intermediate layers 3131 and 3132, and the manufacturing process becomes complicated.

[0210] In contrast, the elastic wave device involved in Modification 6 can simplify the manufacturing process because the intermediate layer 313A can be formed using a single film-forming process and the intermediate layer 323A can be formed using a single film-forming process.

[0211] In addition, in the elastic wave device involved in this modified example, it is not necessary for both metal films 31A and 32A to have the aforementioned angles θ2 and θ4 respectively; it is sufficient that at least one of the metal films 31A and 32A has the aforementioned angles θ2 and θ4.

[0212] [6. Effects, etc.]

[0213] As described above, the elastic wave device 1 according to this embodiment includes a substrate 10 having opposing main surfaces 10a and 10b, a substrate 20 having a main surface 20a facing the main surface 10a, a functional electrode 34 disposed on the main surface 20a, a support portion disposed between the main surfaces 10a and 20a and configured to provide space between the main surfaces 10a and 20a, and a via conductor 11 disposed on the substrate 10 from the main surface 10a toward the main surface 10b. The support portion has a metal film 31 disposed on the main surface 10a and in contact with the via conductor 11, and a metal film 32 sandwiching the metal film 31 disposed on the side opposite to the via conductor 11 and in contact with the metal film 31. When viewed from above the main surface 10a, the area of ​​the metal film 31 includes the area of ​​the metal film 32, and the area of ​​the metal film 31 is larger than the area of ​​the metal film 32. The hardness of the metal film 32 is higher than that of the metal film 31.

[0214] Accordingly, when the metal films 31 and 32 are pressed together, the flattening of the smaller metal film 32 can be prevented, and a bonding process in which the larger metal film 31 wraps around the smaller metal film 32 can be achieved. Therefore, localized heating and the generation of unwanted particles at the joint interface can be suppressed, and the elastic wave device 1 with improved joint strength of the support portion can be provided.

[0215] Furthermore, for example, in the elastic wave device 1, the support portion also has a metal film 33 disposed on the main surface 20a, connected to the functional electrode 34 and in contact with the metal film 32, and the hardness of the metal film 33 is higher than that of the metal film 31.

[0216] Accordingly, a bonding method in which metal films 32 and 33 are wrapped by metal film 31 can be achieved. Therefore, localized heating and the generation of unwanted particles at the joint interface end can be suppressed, and an elastic wave device 1 with improved joint strength of the support can be provided.

[0217] Furthermore, for example, in the elastic wave device 1, the metal film 31 has a main electrode layer 314, an intermediate layer 313 and a bonding layer 311 in sequence from the main surface 10a side, and the metal film 32 has a bonding layer 321, an intermediate layer 323 and a main electrode layer 324 in sequence from the main surface 10a side.

[0218] Accordingly, metal films 31 and 32 are each composed of multiple metal layers with different functions, thus enabling good bonding of metal films 31 and 32.

[0219] Furthermore, for example, in the elastic wave device involved in Modification 6, the angle θ2 formed by the side surface of the intermediate layer 313A and the first plane parallel to the main surface 10a is smaller than the angle θ1 formed by the side surface of the main electrode layer 314A and the first plane.

[0220] Accordingly, the exposed area of ​​the side of the intermediate layer 313A is increased, thus preventing the metal components of the bonding layer 311 and the main electrode layer 314A from being connected and alloyed (migrated) through the side of the intermediate layer 313A.

[0221] Furthermore, for example, in the elastic wave device involved in Modification 6, a portion of the side surface of the main electrode layer 314A is covered by the intermediate layer 313A.

[0222] Accordingly, it is possible to further suppress the metal components of the bonding layer 311 and the metal components of the main electrode layer 314A from becoming connected and alloyed (migrating).

[0223] Furthermore, for example, in the elastic wave device involved in Modification 6, the area of ​​the interface between the main electrode layer 314A and the intermediate layer 313A is larger than the area of ​​the interface between the bonding layer 311 and the intermediate layer 313A.

[0224] Furthermore, for example, in the elastic wave device involved in Modification 6, the intermediate layer 313A comprises titanium.

[0225] Furthermore, for example, in the elastic wave device involved in Modification 6, the angle θ4 formed by the side surface of the intermediate layer 323A and the first plane is smaller than the angle θ3 formed by the side surface of the main electrode layer 324A and the first plane.

[0226] Accordingly, the exposed area of ​​the side of the intermediate layer 323A is increased, thus preventing the metal components of the bonding layer 321 and the main electrode layer 324A from being connected and alloyed (migrated) through the side of the intermediate layer 323A.

[0227] Furthermore, for example, in the elastic wave device involved in Modification 6, a portion of the side surface of the main electrode layer 324A is covered by the intermediate layer 323A.

[0228] Accordingly, it is possible to further suppress the metal composition of the bonding layer 321 from becoming connected and alloyed (migrating) with the metal composition of the main electrode layer 324A.

[0229] Furthermore, for example, in the elastic wave device involved in Modification 6, the area of ​​the interface between the main electrode layer 324A and the intermediate layer 323A is larger than the area of ​​the interface between the bonding layer 321 and the intermediate layer 323A.

[0230] Furthermore, for example, in the elastic wave device involved in Modification 6, the intermediate layer 323A comprises titanium.

[0231] Furthermore, for example, in the elastic wave device 1, the element with the highest weight ratio among the metal elements constituting the bonding layer 321 is the same as the element with the highest weight ratio among the metal elements constituting the bonding layer 311.

[0232] Accordingly, the bonding strength between the metal film 32 and the metal film 33 can be improved, thereby increasing the strength of the support portion.

[0233] Furthermore, for example, in the elastic wave device 1, when viewed from the top of the main surface 10a, the region of the metal film 31 includes the region of the metal film 32, the region of the intermediate layer 323 includes the region of the bonding layer 321, and the area of ​​the intermediate layer 323 is larger than the area of ​​the bonding layer 321; the region of the main electrode layer 324 includes the region of the intermediate layer 323, and the area of ​​the main electrode layer 324 is larger than the area of ​​the intermediate layer 323; the coefficient of linear expansion of the bonding layer 321 is larger than the coefficient of linear expansion of the intermediate layer 323; and the coefficient of linear expansion of the main electrode layer 324 is larger than the coefficient of linear expansion of the bonding layer 321.

[0234] Accordingly, if the metal films 31 and 32 are heated during the pressing process, the main electrode layer 324, with its relatively large coefficient of linear expansion, has a larger area than the intermediate layer 323 and the bonding layer 321. Therefore, at the ends of the main electrode layer 324 and the intermediate layer 323, they have a bimetallic structure. Consequently, the main electrode layer 324 and the intermediate layer 323 readily expand towards the bonding layer 321 at their ends, and both ends of the main electrode layer 324 are pushed towards the metal film 31, thus achieving good bonding at the bonding ends of the metal film 32.

[0235] Furthermore, for example, in the elastic wave device 1, the substrate 20 is piezoelectric, and an IDT electrode 54 is disposed on the main surface 20a. The IDT electrode 54 has a plurality of electrode fingers 61a and a plurality of electrode fingers 61b arranged in parallel with each other, a bus bar electrode 62a configured to connect one end of the plurality of electrode fingers 61a to each other, and a bus bar electrode 62b configured to connect one end of the plurality of electrode fingers 61b to each other and sandwich the plurality of electrode fingers 61a and the plurality of electrode fingers 61b and be disposed opposite to the bus bar electrode 62a. The functional electrode 34 includes a plurality of electrode fingers 61a and a plurality of electrode fingers 61b.

[0236] Accordingly, it is possible to provide surface acoustic wave devices or XBAR devices with improved bonding strength of the support portion.

[0237] Furthermore, for example, in the elastic wave device 1, the substrate 20 has a piezoelectric film 53 including a main surface 20a and a support substrate 51. When the thickness of the piezoelectric film 53 is set to d and the electrode finger spacing of the IDT electrode 54 is set to p, d / p is 0.5 or less.

[0238] Accordingly, an XBAR device with improved bonding strength of the support portion can be provided.

[0239] Furthermore, for example, in the elastic wave device 1, the support portion also has a metal film 33 disposed on the main surface 20a, connected to the functional electrode 34 and in contact with the metal film 32. The metal film 33 includes busbar electrodes 62a and 62b, and the hardness of the metal film 33 is higher than that of the metal film 31.

[0240] Accordingly, a bonding method in which metal films 32 and 33 are wrapped with metal film 31 can be realized. Therefore, localized heating and the generation of unwanted particles at the joint interface end can be suppressed, and an elastic wave device 1 with improved joint strength of the support can be provided.

[0241] Furthermore, for example, in the elastic wave device 1, the functional electrode 34 has a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68 sequentially from the main surface 20a.

[0242] Accordingly, a bulk acoustic wave device with improved bonding strength of the support portion can be provided.

[0243] Furthermore, for example, in the elastic wave device 1, the substrate 10 contains silicon.

[0244] Accordingly, the processing precision of substrate 10 is improved.

[0245] Furthermore, for example, in the elastic wave device 1, when viewed from the top of the main surface 10a, the area of ​​the metal film 31 includes the area of ​​the via conductor 11, and the area of ​​the metal film 31 is larger than the area of ​​the via conductor 11; the area of ​​the metal film 32 includes the area of ​​the via conductor 11, and the area of ​​the metal film 32 is larger than the area of ​​the via conductor 11.

[0246] Accordingly, since the substrate 10 adjacent to the via conductor 11 in the x-axis direction is bonded to the metal film 31, the substrate 10 bonded to the metal film 31 can absorb the compressive stress of the metal films 31 and 32, thereby suppressing the deformation and peeling of the via conductor 11.

[0247] Furthermore, for example, in the elastic wave device 1, when viewed from the main surface 20a, the region of the metal film 33 includes the region of the metal film 32, and the area of ​​the metal film 33 is larger than the area of ​​the metal film 32.

[0248] Accordingly, the metal film 32 does not restrict the configuration area of ​​the functional electrode 34 and the metal film 33 on the main surface 20a, and can prioritize the configuration layout of the functional electrode 34 and the metal film 33.

[0249] (Other implementation methods)

[0250] The above description illustrates embodiments of the elastic wave device according to the present invention, but the present invention is not limited to the above embodiments. Various modifications that can be conceived by those skilled in the art, and various devices incorporating the elastic wave device of the present invention, are also included in the present invention.

[0251] The features of the elastic wave device described below based on the above embodiments are shown below.

[0252] <1> An elastic wave device, comprising:

[0253] The first substrate has a first main surface and a second main surface that are opposite to each other;

[0254] The second substrate has a third main surface facing the first main surface;

[0255] Functional electrodes are disposed on the third main surface;

[0256] A support portion is disposed between the first main surface and the third main surface, configured to provide space between the first main surface and the third main surface; and

[0257] A via conductor is disposed on the first substrate from the first main surface toward the second main surface.

[0258] The support portion has:

[0259] A first metal film, disposed on the first main surface, is in contact with the via conductor; and

[0260] The second metal film, sandwiching the first metal film, is disposed on the side opposite to the via conductor and is in contact with the first metal film.

[0261] From the top view of the first main plane,

[0262] The region of the first metal film includes the region of the second metal film, and the area of ​​the first metal film is larger than the area of ​​the second metal film.

[0263] The second metal film has a higher hardness than the first metal film.

[0264] <2> according to <1> The elastic wave device described herein, wherein,

[0265] The support portion further comprises: a third metal film disposed on the third main surface, connected to the functional electrode, and in contact with the second metal film.

[0266] The hardness of the third metal film is higher than that of the first metal film.

[0267] <3> according to <1> or <2> The elastic wave device described herein, wherein,

[0268] The first metal film, starting from the first main surface side, sequentially comprises a first main electrode layer, a first diffusion prevention layer, and a first bonding layer.

[0269] The second metal film, starting from the first main surface side, sequentially comprises a second bonding layer, a second diffusion prevention layer, and a second main electrode layer.

[0270] The first bonding layer and the second bonding layer are bonded together.

[0271] <4> according to <3> The elastic wave device described herein, wherein,

[0272] The angle between the side surface of the first diffusion prevention layer and the first plane parallel to the first main surface is smaller than the angle between the side surface of the first main electrode layer and the first plane.

[0273] <5> according to <4> The elastic wave device described herein, wherein,

[0274] A portion of the side surface of the first main electrode layer is covered by the first diffusion prevention layer.

[0275] <6> according to <4> or <5> The elastic wave device described herein, wherein,

[0276] The area of ​​the interface between the first main electrode layer and the first diffusion prevention layer is greater than the area of ​​the interface between the first bonding layer and the first diffusion prevention layer.

[0277] <7> according to <4> to <6> The elastic wave device described in any one of the following, wherein,

[0278] The first diffusion prevention layer contains titanium.

[0279] <8> according to <3> to <7> The elastic wave device described in any one of the following, wherein,

[0280] The angle between the side surface of the second diffusion prevention layer and the first plane parallel to the first main surface is smaller than the angle between the side surface of the second main electrode layer and the first plane.

[0281] <9> according to <8> The elastic wave device described herein, wherein,

[0282] A portion of the side surface of the second main electrode layer is covered by the second diffusion prevention layer.

[0283] <10> according to <8> or <9> The elastic wave device described herein, wherein,

[0284] The area of ​​the interface between the second main electrode layer and the second diffusion prevention layer is larger than the area of ​​the interface between the second bonding layer and the second diffusion prevention layer.

[0285] <11> according to <8> to <10> The elastic wave device described in any one of the following, wherein,

[0286] The second diffusion prevention layer contains titanium.

[0287] <12> according to <3> to <11> The elastic wave device described in any one of the following, wherein,

[0288] The element with the highest weight ratio among the metal elements constituting the second bonding layer is the same as the element with the highest weight ratio among the metal elements constituting the first bonding layer.

[0289] <13> according to <3> to <12> The elastic wave device described in any one of the following, wherein,

[0290] From the top view of the first main plane,

[0291] The region of the first metal film includes the region of the second metal film.

[0292] The region of the second diffusion prevention layer includes the region of the second bonding layer, and the area of ​​the second diffusion prevention layer is larger than the area of ​​the second bonding layer.

[0293] The region of the second main electrode layer includes the region of the second diffusion prevention layer, and the area of ​​the second main electrode layer is larger than the area of ​​the second diffusion prevention layer.

[0294] The coefficient of linear expansion of the second diffusion-preventing layer is greater than that of the second bonding layer.

[0295] The coefficient of linear expansion of the second main electrode layer is greater than that of the second diffusion prevention layer.

[0296] <14> according to <1> The elastic wave device described herein, wherein,

[0297] The second substrate is piezoelectric.

[0298] An IDT electrode is disposed on the third main surface.

[0299] The IDT electrode has:

[0300] Multiple first electrode fingers and multiple second electrode fingers arranged in parallel with each other;

[0301] The first busbar electrode is configured to connect one end of the plurality of first electrode fingers to each other; and

[0302] The second busbar electrode is configured to connect one end of the plurality of second electrode fingers to each other, sandwiching the plurality of first electrode fingers and the plurality of second electrode fingers, and is arranged opposite to the first busbar electrode.

[0303] The functional electrode includes the plurality of first electrode fingers and the plurality of second electrode fingers.

[0304] <15> according to <14> The elastic wave device described herein, wherein,

[0305] The second substrate has:

[0306] The piezoelectric film includes the third main surface; and

[0307] support base plate,

[0308] When the thickness of the piezoelectric film is set to d and the electrode finger spacing of the IDT electrode is set to p, d / p is 0.5 or less.

[0309] <16> according to <14> The elastic wave device described herein, wherein,

[0310] The support portion further comprises: a third metal film disposed on the third main surface, connected to the functional electrode, and in contact with the second metal film.

[0311] The third metal film includes the first busbar electrode and the second busbar electrode.

[0312] The hardness of the third metal film is higher than that of the first metal film.

[0313] <17> according to <1> to <13> The elastic wave device described in any one of the following, wherein,

[0314] The functional electrode, starting from the third main surface, has a first planar electrode, a piezoelectric thin film, and a second planar electrode in sequence.

[0315] <18> according to <1> to <17> The elastic wave device described in any one of the following, wherein,

[0316] The first substrate comprises silicon.

[0317] <19> according to <1> to <18> The elastic wave device described in any one of the following, wherein,

[0318] From the top view of the first main plane,

[0319] The region of the first metal film includes the region of the via conductor, and the area of ​​the first metal film is larger than the area of ​​the via conductor.

[0320] The region of the second metal film includes the region of the via conductor, and the area of ​​the second metal film is larger than the area of ​​the via conductor.

[0321] <20> according to <2> The elastic wave device described herein, wherein,

[0322] From the top view of the third main plane,

[0323] The region of the third metal film includes the region of the second metal film, and the area of ​​the third metal film is larger than the area of ​​the second metal film.

[0324] Industrial availability

[0325] This invention, as a small elastic wave device, can be widely used in communication devices such as portable telephones.

[0326] Explanation of reference numerals in the attached figures

[0327] 1.1A Elastic Wave Device

[0328] 10, 20 substrate

[0329] 10a, 10b, 20a, 20b Main face

[0330] 11. Via conductor

[0331] 12 Planar Electrodes

[0332] 13, 23 Insulating film

[0333] 31, 31A, 32, 32A, 33, 33A, 531A, 532A Metallic Films

[0334] 34 Functional Electrodes

[0335] 40 bump electrode

[0336] 51 Support base plate

[0337] 52 Intermediate Layer

[0338] 53 Piezoelectric film

[0339] 54 IDT Electrode

[0340] 55, 58 Protective layer

[0341] 57 Piezoelectric single crystal substrate

[0342] 60 Elastic wave harmonic oscillator

[0343] 60a, 60b comb electrodes

[0344] Electrode fingers 61a and 61b

[0345] 62a, 62b busbar electrodes

[0346] 65 Support base plate

[0347] 66 Lower electrode

[0348] 67 Piezoelectric layer

[0349] 68 Upper electrode

[0350] 71, 72 Support sections

[0351] 160 gap

[0352] 311, 321 bonding layer

[0353] 312, 313, 313A, 315, 316, 322, 323, 323A, 325, 331, 333, 3131, 3132, 3231, 3232 Intermediate Layer

[0354] 314, 314A, 324, 324A, 332, 542 Main electrode layers

[0355] 540 Close-fitting layer.

Claims

1. An elastic wave device, comprising: The first substrate has a first main surface and a second main surface that are opposite to each other; The second substrate has a third main surface facing the first main surface; Functional electrodes are disposed on the third main surface; A support portion is disposed between the first main surface and the third main surface, configured to provide space between the first main surface and the third main surface; and A via conductor is disposed on the first substrate from the first main surface toward the second main surface. The support portion has: A first metal film is disposed on the first main surface and is in contact with the via conductor; and The second metal film, sandwiching the first metal film, is disposed on the side opposite to the via conductor and is in contact with the first metal film. From the top view of the first main plane, The region of the first metal film includes the region of the second metal film, and the area of ​​the first metal film is larger than the area of ​​the second metal film. The second metal film has a higher hardness than the first metal film.

2. The elastic wave device according to claim 1, wherein, The support portion further comprises: a third metal film disposed on the third main surface, connected to the functional electrode, and in contact with the second metal film. The hardness of the third metal film is higher than that of the first metal film.

3. The elastic wave device according to claim 1 or 2, wherein, The first metal film, starting from the first main surface side, sequentially comprises a first main electrode layer, a first diffusion prevention layer, and a first bonding layer. The second metal film, starting from the first main surface side, sequentially comprises a second bonding layer, a second diffusion prevention layer, and a second main electrode layer. The first bonding layer and the second bonding layer are bonded together.

4. The elastic wave device according to claim 3, wherein, The angle between the side surface of the first diffusion prevention layer and the first plane parallel to the first main surface is smaller than the angle between the side surface of the first main electrode layer and the first plane.

5. The elastic wave device according to claim 4, wherein, A portion of the side surface of the first main electrode layer is covered by the first diffusion prevention layer.

6. The elastic wave device according to claim 4 or 5, wherein, The area of ​​the interface between the first main electrode layer and the first diffusion prevention layer is greater than the area of ​​the interface between the first bonding layer and the first diffusion prevention layer.

7. The elastic wave device according to any one of claims 4 to 6, wherein, The first diffusion prevention layer contains titanium.

8. The elastic wave device according to any one of claims 3 to 7, wherein, The angle between the side surface of the second diffusion prevention layer and the first plane parallel to the first main surface is smaller than the angle between the side surface of the second main electrode layer and the first plane.

9. The elastic wave device according to claim 8, wherein, A portion of the side surface of the second main electrode layer is covered by the second diffusion prevention layer.

10. The elastic wave device according to claim 8 or 9, wherein, The area of ​​the interface between the second main electrode layer and the second diffusion prevention layer is larger than the area of ​​the interface between the second bonding layer and the second diffusion prevention layer.

11. The elastic wave device according to any one of claims 8 to 10, wherein, The second diffusion prevention layer contains titanium.

12. The elastic wave device according to any one of claims 3 to 11, wherein, The element with the highest weight ratio among the metal elements constituting the second bonding layer is the same as the element with the highest weight ratio among the metal elements constituting the first bonding layer.

13. The elastic wave device according to any one of claims 3 to 12, wherein, From the top view of the first main plane, The region of the first metal film includes the region of the second metal film. The region of the second diffusion prevention layer includes the region of the second bonding layer, and the area of ​​the second diffusion prevention layer is larger than the area of ​​the second bonding layer. The region of the second main electrode layer includes the region of the second diffusion prevention layer, and the area of ​​the second main electrode layer is larger than the area of ​​the second diffusion prevention layer. The coefficient of linear expansion of the second bonding layer is greater than that of the second diffusion-preventing layer. The coefficient of linear expansion of the second main electrode layer is greater than that of the second bonding layer.

14. The elastic wave device according to claim 1, wherein, The second substrate is piezoelectric. An IDT electrode is disposed on the third main surface. The IDT electrode has: Multiple first electrode fingers and multiple second electrode fingers arranged in parallel with each other; The first busbar electrode is configured to connect one end of the plurality of first electrode fingers to each other; and The second busbar electrode is configured to connect one end of the plurality of second electrode fingers to each other, sandwiching the plurality of first electrode fingers and the plurality of second electrode fingers, and is arranged opposite to the first busbar electrode. The functional electrode includes the plurality of first electrode fingers and the plurality of second electrode fingers.

15. The elastic wave device according to claim 14, wherein, The second substrate has: The piezoelectric film includes the third main surface; and support base plate, When the thickness of the piezoelectric film is set to d and the electrode finger spacing of the IDT electrode is set to p, d / p is 0.5 or less.

16. The elastic wave device according to claim 14, wherein, The support portion further comprises: a third metal film disposed on the third main surface, connected to the functional electrode, and in contact with the second metal film. The third metal film includes the first busbar electrode and the second busbar electrode. The hardness of the third metal film is higher than that of the first metal film.

17. The elastic wave device according to any one of claims 1 to 13, wherein, The functional electrode, starting from the third main surface, has a first planar electrode, a piezoelectric thin film, and a second planar electrode in sequence.

18. The elastic wave device according to any one of claims 1 to 17, wherein, The first substrate comprises silicon.

19. The elastic wave device according to any one of claims 1 to 18, wherein, From the top view of the first main plane, The region of the first metal film includes the region of the via conductor, and the area of ​​the first metal film is larger than the area of ​​the via conductor. The region of the second metal film includes the region of the via conductor, and the area of ​​the second metal film is larger than the area of ​​the via conductor.

20. The elastic wave device according to claim 2, wherein, From the top view of the third main plane, The region of the third metal film includes the region of the second metal film, and the area of ​​the third metal film is larger than the area of ​​the second metal film.

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