Acoustic wave device

Abstract

This acoustic wave device includes: a piezoelectric layer which has a first main surface and a second main surface on the side opposite to the first main surface; an upper electrode which is provided on the first main surface of the piezoelectric layer; a lower electrode which is provided on the second main surface of the piezoelectric layer; a support member which is disposed facing the second main surface of the piezoelectric layer and which is provided with a cavity portion in a region where at least the upper electrode and the lower electrode overlap; a counter electrode which is provided inside the cavity portion and which is disposed facing the lower electrode; and a lead-out structure which is connected to the counter electrode and which is led out to the first main surface side of the piezoelectric layer.

Description

Elastic Wave Device

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

[0002] Patent document 1 describes a thin-film piezoelectric resonator that includes a lower substrate having a recess, a thin-film piezoelectric element provided above the opening of the recess, an upper substrate provided above the thin-film piezoelectric element, and a sealing portion for sealing the space between the lower substrate and the upper substrate.

[0003] Japanese Patent Application Laid-Open No. 2008-98831

[0004] In the thin film piezoelectric resonator disclosed in Patent Document 1, heat generated in the excitation region of the thin film piezoelectric element may be trapped within the recessed portion, and therefore, there is a demand for improved heat dissipation in acoustic wave devices (thin film piezoelectric resonators in Patent Document 1).

[0005] An object of the present invention is to provide an acoustic wave device that can improve heat dissipation properties.

[0006] An elastic wave device according to one embodiment includes a piezoelectric layer having a first main surface and a second main surface opposite the first main surface, an upper electrode provided on the first main surface of the piezoelectric layer, a lower electrode provided on the second main surface of the piezoelectric layer, a support member arranged opposite the second main surface of the piezoelectric layer and having a cavity portion in at least a region where the upper electrode and the lower electrode overlap, a counter electrode provided inside the cavity portion and arranged opposite the lower electrode, and an extraction structure connected to the counter electrode and extracted to the first main surface side of the piezoelectric layer.

[0007] According to an acoustic wave device of the present invention, heat dissipation can be improved.

[0008] FIG. 1 is a plan view illustrating an elastic wave device according to a first preferred embodiment. FIG. 2 is a plan view illustrating a portion of the elastic wave device according to the first preferred embodiment. FIG. 3 is a cross-sectional view taken along line III-III′ in FIG. 2. FIG. 4 is an explanatory diagram illustrating a method for manufacturing the elastic wave device according to the first preferred embodiment. FIG. 5 is a cross-sectional view illustrating an elastic wave device according to a second preferred embodiment. FIG. 6 is a cross-sectional view illustrating an elastic wave device according to a third preferred embodiment. FIG. 7 is a plan view illustrating an elastic wave device according to a fourth preferred embodiment. FIG. 8 is a cross-sectional view taken along line VIII-VIII′ in FIG. 7. FIG. 9 is a plan view illustrating an elastic wave device according to a fifth preferred embodiment. FIG. 10 is a plan view illustrating an elastic wave device according to a modification of the fifth preferred embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is illustrative, and partial substitution or combination of configurations between different embodiments is possible. In modified examples and the second and subsequent embodiments, descriptions of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0010] First Embodiment FIG. 1 is a plan view showing an elastic wave device according to a first embodiment. FIG. 2 is a plan view showing a portion of the elastic wave device according to the first embodiment. FIG. 3 is a cross-sectional view taken along III-III′ in FIG. 2. Note that FIG. 2 is a plan view showing elastic wave device 10 according to the first embodiment without a lid 70. The resonators constituting elastic wave device 10 according to the first embodiment are resonators that utilize bulk waves, i.e., BAW (Bulk Acoustic Wave) elements.

[0011] 1 to 3 , elastic wave device 10 includes support member 13, piezoelectric layer 20, upper electrode 31, lower electrode 32, counter electrode 33, and lead wiring 34. Elastic wave device 10 also includes lid 70, connection portion 40, sealing portion 60, connection terminal 72, and bump 73, which are provided above the resonator. As shown in FIG. 3 , the resonator is formed by stacking lower electrode 32, piezoelectric layer 20, and upper electrode 31 in this order on support member 13.

[0012] In the following description, the thickness direction of the piezoelectric layer 20 is referred to as the Z direction, the direction perpendicular to the Z direction is referred to as the X direction, and the direction perpendicular to the Z direction and the X direction is referred to as the Y direction. The X direction and the Y direction are each parallel to the surface (first main surface 20a) of the piezoelectric layer 20. In the following description, a plan view refers to the positional relationship when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric layer 20 (Z direction).

[0013] The support member 13 is provided opposite the second main surface 20b of the piezoelectric layer 20. The support member 13 includes a support substrate 11 and an insulating layer 12. The support substrate 11 is made of silicon (Si), quartz crystal, or the like. The insulating layer 12 is provided between the support substrate 11 and the piezoelectric layer 20. The insulating layer 12 is made of an insulating material such as silicon oxide. Note that the support member 13 may be configured without the insulating layer 12, with the piezoelectric layer 20 being provided on the support substrate 11.

[0014] A cavity 14 (hollow portion) is formed on the surface of the support member 13 (insulating layer 12) facing the second main surface 20b of the piezoelectric layer 20. The cavity 14 is provided so as to overlap, in plan view, with the excitation region of the resonator formed by overlapping the piezoelectric layer 20, the upper electrode 31, and the lower electrode 32. This allows bulk waves to be reflected by the cavity 14.

[0015] The piezoelectric layer 20 is in the form of a flat plate having a first main surface 20a and a second main surface 20b opposite to the first main surface 20a. The piezoelectric layer 20 is made of lithium niobate (LiNbO ３ ) or lithium tantalate (LiTaO ３ The thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 1 μm or less.

[0016] The upper electrode 31 is provided on the first main surface 20a of the piezoelectric layer 20. As shown in Fig. 2, the upper electrode 31 has a main electrode portion 31a and an extension portion 31b connected to the main electrode portion 31a. The main electrode portion 31a is provided in the excitation region of the resonator and is formed in a substantially circular shape. The extension portion 31b has a width equal to the diameter of the main electrode portion 31a, extends in the X direction, and is connected to the connection portion 40.

[0017] The lower electrode 32 is provided on the second main surface 20b of the piezoelectric layer 20, in a region where at least a portion of the lower electrode 32 overlaps with the upper electrode 31. As shown in FIG. 2 , the lower electrode 32 has a main electrode portion 32a and an extension portion 32b connected to the main electrode portion 32a. The main electrode portion 32a is provided in the excitation region of the resonator and is formed in a substantially circular shape. That is, the main electrode portion 32a is provided in a region that overlaps with the main electrode portion 31a of the upper electrode 31, with the piezoelectric layer 20 sandwiched therebetween. The extension portion 32b has a width equal to the diameter of the main electrode portion 32a, extends in the X direction on the side opposite the extension portion 31b of the upper electrode 31, and is connected to a connection portion 40 separate from the upper electrode 31. An adhesion layer made of Ti, NiCr, or the like may be provided between the lower electrode 32 and the insulating layer 12.

[0018] The upper electrode 31 and the lower electrode 32 are formed of a metal such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo), or an alloy containing at least one of these materials. The upper electrode 31 and the lower electrode 32 may be a laminated film.

[0019] The acoustic wave device 10 has a so-called membrane structure in which a cavity 14 (hollow portion) is provided on the second main surface 20b side of the piezoelectric layer 20. In the region overlapping with the cavity 14, the piezoelectric layer 20 is disposed between the main electrode portion 31a of the upper electrode 31 and the main electrode portion 32a of the lower electrode 32 in the Z direction. This allows bulk waves to propagate between the main electrode portion 31a of the upper electrode 31 and the main electrode portion 32a of the lower electrode 32. In the following description, the region where the upper electrode 31 and the lower electrode 32 overlap in a planar view may be described as the excitation region of the resonator.

[0020] In this embodiment, the area of ​​the cavity 14 is larger than the area of ​​the excitation region where the main electrode portion 31a of the upper electrode 31 and the main electrode portion 32a of the lower electrode 32 overlap in a plan view. In this embodiment, the width of the cavity 14 in the Y direction is larger than the widths of the main electrode portion 31a of the upper electrode 31 and the main electrode portion 32a of the lower electrode 32 in the Y direction. As shown in FIG. 2 , the inner wall of the cavity 14 in the Y direction (the lower side in FIG. 2 ) is located between the side surfaces of the main electrode portion 31a of the upper electrode 31 and the main electrode portion 32a of the lower electrode 32 and the side surface of the support member 13. In addition, the main electrode portion 31a of the upper electrode 31 and the main electrode portion 32a of the lower electrode 32 are provided so as to overlap the cavity 14, and the extension portions 31b, 32b are provided in regions that do not overlap the cavity 14.

[0021] Since the area of ​​the cavity 14 is larger than the area of ​​the excitation region, the heat generated in the excitation region spreads over a wider area inside the cavity 14 than when the cavity 14 is formed with an area equivalent to that of the excitation region. Therefore, in this embodiment, localized heat concentration in the support member 13 can be suppressed, and the heat distribution can be made uniform.

[0022] 3 , the counter electrode 33 is provided inside the cavity portion 14 and is disposed opposite the lower electrode 32. The counter electrode 33 is disposed apart from the lower electrode 32. The counter electrode 33 is provided on the bottom surface of the cavity portion 14. More preferably, the counter electrode 33 is provided so as to cover the entire area of ​​the bottom surface of the cavity portion 14.

[0023] The counter electrode 33 is made of a metal such as aluminum (Al), gold (Au), silver (Ag), copper (Cu), platinum (Pt), nickel (Ni), or titanium (Ti), or an alloy containing at least one of these materials. The counter electrode 33 is made of a material having a higher thermal conductivity than the insulating layer 12, and is provided as a heat transfer section that transfers heat generated in the excitation region to the outside (the first main surface 20a of the piezoelectric layer 20).

[0024] 2 and 3 , an opening 21 is provided in a region of the piezoelectric layer 20 that overlaps with the cavity portion 14 but does not overlap with the upper electrode 31 or the lower electrode 32. The opening 21 is also provided at a position that overlaps with the outer edge of the counter electrode 33 provided in the cavity portion 14.

[0025] The lead wiring 34 connects the connection portion 40 and the counter electrode 33 inside the cavity portion 14. More specifically, the lead wiring 34 is provided on the outer edge side of the first main surface 20a of the piezoelectric layer 20 and is also formed in an area overlapping with the opening 21. One end of the lead wiring 34 is connected to the counter electrode 33 inside the cavity portion 14 and is led out to the first main surface 20a of the piezoelectric layer 20 through the opening 21, and the other end is connected to the sealing portion 60. As a result, the lead wiring 34 is formed as a lead structure that is connected to the counter electrode 33 inside the cavity portion 14 and led out to the first main surface 20a of the piezoelectric layer 20. The lead wiring 34 is made of the same material as the counter electrode 33 and has good thermal conductivity.

[0026] With this configuration, the counter electrode 33 formed inside the cavity 14 is connected to the lead-out wiring 34. The counter electrode 33 and the lead-out wiring 34 form a heat transfer path that extends from the inside of the cavity 14 through the opening 21 to the first main surface 20 a side of the piezoelectric layer 20.

[0027] The opening 21 not only serves as an opening for drawing out the counter electrode 33, but also as an opening for etching when forming the cavity portion 14 of the insulating layer 12. That is, the cavity portion 14 is formed by forming a sacrificial layer 50 (see FIG. 4) in the region that will become the cavity portion 14, bonding the piezoelectric layer 20 to the support member 13, and then removing the sacrificial layer 50 through the opening 21 (etching window).

[0028] The lid portion 70 is disposed opposite the first main surface 20a of the piezoelectric layer 20. The connection portion 40 and the sealing portion 60 are provided between the lid portion 70 and the first main surface 20a of the piezoelectric layer 20. A plurality of connection terminals 72 and bumps 73 are provided on the upper surface of the lid portion 70 (the side opposite to the surface facing the first main surface 20a of the piezoelectric layer 20).

[0029] As shown in FIG. 1 , a plurality of connection terminals 72 and bumps 73 (not shown in FIG. 1 ) are provided on the lid portion 70. Of the plurality of connection terminals 72, for example, connection terminal 72c is a ground terminal connected to ground. Of the plurality of connection terminals 72, for example, connection terminals 72a and 72b are signal terminals connected to the resonator, one of which is connected to an input terminal and the other to an output terminal. The upper electrode 31 and the lower electrode 32 that constitute the resonator are electrically connected to the connection terminals 72a and 72b via the connection portion 40 and via vias 71 that penetrate the lid portion 70, respectively.

[0030] The sealing portion 60 seals the gap between the lid portion 70 and the support member 13. As shown in Figures 1 and 2, the sealing portion 60 extends along the outer edge of the support member 13 in a plan view and is formed in a frame shape. The upper electrode 31, lower electrode 32, cavity portion 14, counter electrode 33, and multiple connection portions 40 described above are provided within the area surrounded by the sealing portion 60. The sealing portion 60 and the connection portions 40 are formed of a metal material or an alloy material having good conductivity.

[0031] 3, the lower end of the connection portion 40 is connected to the upper electrode 31. The upper end of the connection portion 40 is connected to a connection terminal 72 and a bump 73 through a via 71 that penetrates the lid portion 70 in the thickness direction. Although not shown in FIG. 3, the lower electrode 32 is also drawn out to the first main surface 20a of the piezoelectric layer 20, and, like the upper electrode 31, is connected to the connection portion 40 and is connected to the connection terminal 72 and the bump 73 through the via 71. The lower end of the sealing portion 60 is connected to the lead-out wiring 34.

[0032] With the above-described configuration, the counter electrode 33 formed inside the cavity 14, the lead wiring 34, and the sealing portion 60 are connected, forming a heat transfer path from the cavity 14 to the lid portion 70. Heat generated in the excitation region is transferred from the counter electrode 33 formed inside the cavity 14 to the first main surface 20a of the piezoelectric layer 20, and is then efficiently dissipated by the sealing portion 60 and the lid portion 70, which are exposed to the outside.

[0033] As described above, the area of ​​the cavity portion 14 is larger than the area of ​​the excitation region (the area where the main electrode portion 31 a of the upper electrode 31 and the main electrode portion 32 a of the lower electrode 32 overlap). The area of ​​the counter electrode 33 can also be formed larger than the area of ​​the excitation region. This prevents localized heat concentration in the counter electrode 33, thereby achieving a more uniform heat distribution in the counter electrode 33. Therefore, heat generated in the excitation region is efficiently conducted to the sealing portion 60 and the lid portion 70 via the counter electrode 33 and the lead-out wiring 34. Therefore, the elastic wave device 10 of this preferred embodiment can improve heat dissipation.

[0034] Furthermore, the support substrate 11 is made of silicon (Si) and is semiconductive. Therefore, parasitic capacitance occurs between the support substrate 11 and the upper electrode 31, the lower electrode 32, and various wirings. As shown in FIG. 3 , in this embodiment, the counter electrode 33 is disposed between the support substrate 11 and the lower electrode 32. The sealing portion 60 is connected to at least one connection terminal 72c (ground terminal) through wiring (not shown) and the connection portion 40. Therefore, the counter electrode 33 is connected to a reference potential (e.g., ground potential) through the sealing portion 60. This enables the elastic wave device 10 to suppress parasitic capacitance formed between the support substrate 11 and the upper electrode 31 and lower electrode 32. The reference potential is not limited to ground potential and may be any other predetermined potential.

[0035] In this embodiment, the sealing portion 60 is provided along the outer edge of the support member 13 and is disposed in all directions around the periphery. This improves the degree of freedom in connecting the counter electrode 33 and the sealing portion 60. That is, even if the position of the resonator differs from the examples shown in FIGS. 2 and 3 , the lead wires 34 can be connected to the side of the sealing portion 60 closest to the resonator, thereby reducing the length of the lead wires 34. Furthermore, the counter electrode 33 and the sealing portion 60 may be connected by multiple lead wires 34. This ensures the ground strength of the counter electrode 33 and enhances the shielding effect. In other words, it is possible to suppress capacitive coupling between the support substrate 11 and the upper electrode 31 and lower electrode 32. Furthermore, by connecting multiple lead wires 34 to the counter electrode 33, the heat dissipation effect can be improved.

[0036] The planar shapes of the upper electrode 31, the lower electrode 32, and the counter electrode 33 shown in FIG. 2 are merely examples and can be modified as appropriate. Furthermore, the counter electrode 33 is not limited to a configuration that covers the entire bottom surface of the cavity portion 14, but may be provided on at least a portion of the bottom surface of the cavity portion 14. Although the example in which one resonator is formed on one support member 13 has been shown, multiple resonators may be formed on one support member 13. An example in which multiple resonators are formed will be described later in the fourth embodiment, with reference to FIGS. 9 and 10 . Furthermore, the arrangement and shape of the connection terminals 72 shown in FIG. 1 are merely examples and can be modified as appropriate. For example, when multiple resonators are provided, the number, arrangement, and connection configuration of the connection terminals 72 can also be appropriately modified.

[0037] 3, the piezoelectric layer 20 is provided to cover the entire surface of the support member 13, but this is not limiting. The piezoelectric layer 20 only needs to be provided in at least the portion where the resonator is configured, and for example, the piezoelectric layer 20 may not be provided on the outer edge side of the support member 13. That is, the side surface on the outer edge side of the piezoelectric layer 20 may be located more inward (closer to the cavity portion 14) than the side surface of the insulating layer 12. In other words, in the region where the connection portion 40 is provided, the support substrate 11, the insulating layer 12, the lead wiring 34, and the connection portion 40 may be laminated in this order.

[0038] Next, a method for manufacturing the elastic wave device 10 according to this preferred embodiment will be described. FIG. 4 is a diagram illustrating a method for manufacturing the elastic wave device according to the first preferred embodiment. As shown in FIG. 4, a LiNbO ３ , LiTaO ３ A piezoelectric layer 20, which is a single crystal substrate such as a silicon dioxide film, is prepared, and a lower electrode 32 is formed on the second main surface 20b of the piezoelectric layer 20 (step ST1). The lower electrode 32 is formed, for example, by a vapor deposition lift-off method. That is, in step ST1, a resist is patterned on the second main surface 20b of the piezoelectric layer 20 by photolithography. A metal film is vapor-deposited, and then the resist is removed, thereby forming the metal film as the lower electrode 32. In step ST1, the lower electrode 32 is patterned to have a main electrode portion 32a and an extension portion 32b (see FIG. 2).

[0039] Next, a sacrificial layer 50 is formed on the second main surface 20b of the piezoelectric layer 20 (step ST2). The sacrificial layer 50 is provided in a region of the support member 13 (insulating layer 12) where the cavity portion 14 is to be formed. The sacrificial layer 50 is provided so as to cover at least the main electrode portion 32a of the lower electrode 32. The sacrificial layer 50 is formed by sputtering using a material such as zinc oxide (ZnO).

[0040] Next, the counter electrode 33 is formed to cover the sacrificial layer 50 (step ST3). The counter electrode 33 is formed to cover the upper surface of the sacrificial layer 50 and to cover part of the side surface of the sacrificial layer 50. The counter electrode 33 is formed by, for example, a vapor deposition lift-off method.

[0041] An insulating layer 12 is formed on the second main surface 20b of the piezoelectric layer 20, covering the lower electrode 32, the sacrificial layer 50, and the counter electrode 33 (step ST4). The insulating layer 12 is formed by sputtering using a material such as silicon oxide. An adhesive layer made of Ti, NiCr, or the like may be provided between the lower electrode 32 and the insulating layer 12 or between the counter electrode 33 and the insulating layer 12. The surface of the insulating layer 12 (the surface opposite to the piezoelectric layer 20) may be planarized by CMP (chemical mechanical polishing) as needed.

[0042] Next, the support substrate 11 is prepared, and the support substrate 11 is bonded to the insulating layer 12 formed on the second main surface 20b of the piezoelectric layer 20. This bonds the support substrate 11 to the insulating layer 12 and the piezoelectric layer 20 (step ST5). In the step of bonding the support substrate 11 to the insulating layer 12, an intermediate layer made of the same material as the insulating layer 12, such as silicon oxide, may be formed on the surface of the support substrate 11 in advance. In this case, the intermediate layer is bonded to the insulating layer 12 by direct bonding, plasma activated bonding, atomic diffusion bonding, or the like.

[0043] An opening 21 is formed in the piezoelectric layer 20 at a position overlapping the sacrificial layer 50 (the region where the cavity 14 is to be formed), and the sacrificial layer 50 is removed through the opening 21 to form the cavity 14 in the insulating layer 12 (step ST6). More specifically, the opening 21 is formed at a position that overlaps the sacrificial layer 50 but does not overlap the regions where the lower electrode 32 and the upper electrode 31 are to be formed. The opening 21 is formed by removing a portion of the piezoelectric layer 20 by RIE (Reactive Ion Etching).

[0044] The sacrificial layer 50 is then removed by wet etching. An etchant that dissolves the sacrificial layer 50 is poured through the opening 21. As a result, a cavity 14 is formed in the insulating layer 12, and the membrane structure of the piezoelectric layer 20 is formed.

[0045] Next, the laminated body formed by stacking the piezoelectric layer 20, the insulating layer 12, and the support substrate 11 is turned upside down, and the upper electrode 31 and the lead-out wiring 34 are formed on the first main surface 20a of the piezoelectric layer 20 (step ST7). The upper electrode 31 and the lead-out wiring 34 may be formed simultaneously in the same process, or may be formed sequentially in different processes.

[0046] The upper electrode 31 is formed in a region of the first main surface 20a of the piezoelectric layer 20 that overlaps with the cavity portion 14. The lead-out wiring 34 is formed on the outer edge side of the first main surface 20a of the piezoelectric layer 20, spaced apart from the upper electrode 31. A portion of the lead-out wiring 34 is formed in a region that overlaps with the opening 21, and is connected to the counter electrode 33 inside the cavity portion 14. As a result, the counter electrode 33 and the lead-out wiring 34 form a heat transfer path that runs from the inside of the cavity portion 14 through the opening 21 to the first main surface 20a side of the piezoelectric layer 20.

[0047] 3 , the stack of the support substrate 11, the insulating layer 12, and the piezoelectric layer 20 is joined to the lid portion 70 via the connection portion 40 and the sealing portion 60. The connection portion 40 electrically connects the upper electrode 31 and the lower electrode 32 to the connection terminal 72 and the bump 73 through the via 71, respectively. The sealing portion 60 also seals the space between the stack of the support substrate 11, the insulating layer 12, and the piezoelectric layer 20 and the lid portion 70. The sealing portion 60 also connects the lead wiring 34 to the lid portion 70.

[0048] The acoustic wave device 10 is manufactured through the above steps. Note that the steps shown in FIG. 4 are merely schematic and can be modified as appropriate. For example, after the bonding step of the support substrate 11 in step ST5, the first main surface 20 a of the piezoelectric layer 20 may be thinned as needed. The first main surface 20 a of the piezoelectric layer 20 may be polished, for example, by mechanical polishing or CMP. As a result, the thickness of the piezoelectric layer 20 is reduced to, for example, approximately 1 μm or less. Alternatively, the method is not limited to polishing. For example, the piezoelectric layer 20 may be thinned by forming a damaged layer inside the piezoelectric layer 20 by ion implantation and then peeling off a layer on top of the damaged layer.

[0049] 4 , the counter electrode 33 is provided on the bottom and side surfaces of the cavity portion 14. More specifically, the bottom of the counter electrode 33 is provided so as to cover the entire area of ​​the bottom surface of the cavity portion 14. The side surfaces of the counter electrode 33 are provided so as to cover the side surfaces of the cavity portion 14 in areas that do not overlap with the lower electrode 32. The lead-out wiring 34 is connected to the side surfaces of the counter electrode 33 inside the cavity portion 14 so as to overlap with the side surfaces of the counter electrode 33.

[0050] Second Embodiment Fig. 5 is a cross-sectional view showing an elastic wave device according to a second embodiment. As shown in Fig. 5 , an elastic wave device 10A according to the second embodiment differs from the first embodiment in that the lower end of a sealing portion 60A disposed between a lid portion 70 and a support member 13 is embedded within the support member 13.

[0051] More specifically, the piezoelectric layer 20 is not provided on the outer edge side of the support member 13, and the side surface on the outer edge side of the piezoelectric layer 20 is located inside the side surface of the insulating layer 12. The sealing portion 60A is provided between the lid portion 70 and the support member 13 (insulating layer 12) on the outer edge side of the piezoelectric layer 20. The connecting portion 40 is provided between the piezoelectric layer 20 and the lid portion 70 inside the sealing portion 60A, and is connected to the upper electrode 31 (or the lower electrode 32).

[0052] The sealing portion 60A is configured by connecting a first sealing portion 61 and a second sealing portion 62 in the Z direction. The first sealing portion 61 is provided above the insulating layer 12 of the support member 13, between the lid portion 70 and the insulating layer 12. The second sealing portion 62 is a portion of the sealing portion 60A that is formed by being embedded in the insulating layer 12 of the support member 13. The first sealing portion 61 and the second sealing portion 62 may be formed from a single continuous member, or may be formed from separate members that are connected in the Z direction.

[0053] The cavity portion 14 is provided from the region (excitation region) where the upper electrode 31 and the lower electrode 32 overlap to the second sealing portion 62 of the sealing portion 60A located inside the support member 13 (insulating layer 12). In the example shown in FIG. 5, the second sealing portion 62 of the sealing portion 60A forms part of the side surface of the cavity portion 14.

[0054] The counter electrode 33 is provided on the bottom surface of the cavity 14, and extends from the region (excitation region) where the upper electrode 31 and the lower electrode 32 overlap to the second sealing portion 62 of the sealing portion 60A located inside the support member 13 (insulating layer 12). The outer edge of the counter electrode 33 is connected to the lower end side of the second sealing portion 62.

[0055] In this embodiment, the sealing portion 60A is formed as an extended structure in which the lower end side of the second sealing portion 62 is connected to the counter electrode 33, and the upper end side of the first sealing portion 61 is extended to the first main surface 20a of the piezoelectric layer 20 and connected to the lid portion 70. The upper end of the first sealing portion 61 is electrically connected to the connection terminal 72 and the bump 73 through the connection wiring 74 and the via 71. The sealing portion 60A is connected to the connection terminal 72c (see FIG. 1 ), which is a ground terminal, among the multiple connection terminals 72. The sealing portion 60A is formed of a metal material or alloy material having good conductivity. Note that the sealing portion 60A is not connected to the connection terminals 72a and 72b (the input terminal and output terminal through which a signal is transmitted (see FIG. 1 )) among the multiple connection terminals 72.

[0056] With this configuration, the counter electrode 33 formed inside the cavity 14, the sealing portion 60A (first sealing portion 61 and second sealing portion 62), the vias 71, the connection wiring 74, the connection terminals 72, and the bumps 73 are connected to form a heat transfer path. In this embodiment as well, heat generated in the excitation region is transferred from the counter electrode 33 formed inside the cavity 14 to the first main surface 20a of the piezoelectric layer 20 through the sealing portion 60A, and is then efficiently dissipated by the sealing portion 60A and the lid portion 70, which are exposed to the outside. In addition, a ground potential is supplied to the counter electrode 33 through the connection terminals 72 (connection terminals 72c), the connection wiring 74, and the sealing portion 60A.

[0057] As in the first embodiment, the sealing portion 60A is formed in a frame shape along the outer edge of the support member 13 in a plan view. The second sealing portion 62 of the sealing portion 60A (the portion embedded in the insulating layer 12) may be provided in a frame shape over the entire sealing portion 60A, or may be provided only in a portion along the outer periphery of the sealing portion 60A, i.e., only at the connection point with the counter electrode 33. The first sealing portion 61 and the second sealing portion 62 of the sealing portion 60A have the same width. However, this is not limited thereto, and the first sealing portion 61 and the second sealing portion 62 may be formed to have different widths.

[0058] 6 is a cross-sectional view of an elastic wave device according to a third embodiment. As shown in FIG. 6 , an elastic wave device 10B according to the third embodiment differs from the first embodiment in that it has a back electrode 36 provided on the surface of support member 13 opposite piezoelectric layer 20.

[0059] The back electrode 36 is provided so as to cover the entire lower surface of the support substrate 11 (the surface opposite to the piezoelectric layer 20). However, without being limited thereto, the back electrode 36 may be provided on a part of the lower surface of the support substrate 11, for example, in an area that overlaps with at least the counter electrode 33.

[0060] The counter electrode 33 provided inside the cavity portion 14 is connected to the back surface electrode 36 through a via 37 that penetrates the support substrate 11 and insulating layer 12 of the support member 13. The via 37 is provided between the bottom of the cavity portion 14 and the lower surface of the support substrate 11, penetrating the insulating layer 12 and the support substrate 11.

[0061] In this embodiment, the lead wiring 34 is connected to the connection portion 40. That is, one end of the lead wiring 34 is connected to the counter electrode 33 inside the cavity 14 and is led out to the first main surface 20a of the piezoelectric layer 20 through the opening 21. The other end of the lead wiring 34 is connected to the connection portion 40. The counter electrode 33 formed inside the cavity 14 is connected to the lead wiring 34, the connection portion 40, the via 71, the connection terminal 72, and the bump 73. This forms a heat transfer path from the cavity 14 to the first main surface 20a of the piezoelectric layer 20. Furthermore, in this embodiment, the counter electrode 33 is connected to the via 37 and the back surface electrode 36, providing a heat transfer path from the cavity 14 to the underside of the support substrate 11. This provides the elastic wave device 10B of this embodiment with excellent heat dissipation properties.

[0062] The counter electrode 33 is connected to a connection terminal 72c (see FIG. 1 ), which is a ground terminal among the multiple connection terminals 72. That is, the counter electrode 33 is connected to a reference potential (e.g., ground potential) through the connection portion 40, the via 71, the connection terminal 72, and the bump 73. The counter electrode 33 is also connected to the sealing portion 60 on the outer edge side of the support member 13. As a result, the sealing portion 60 is connected to the same reference potential (e.g., ground potential) as the counter electrode 33. The back electrode 36 is also electrically connected to the counter electrode 33 through the via 37 and is connected to the same reference potential (e.g., ground potential) as the counter electrode 33. As a result, the back electrode 36 also functions as a shield electrode and can shield noise from the underside of the support member 13.

[0063] The configuration of the back electrode 36 and the via 37 shown in this embodiment can also be combined with the first and second embodiments described above.

[0064] Fourth Preferred Embodiment Fig. 7 is a plan view showing an elastic wave device according to a fourth preferred embodiment. Fig. 8 is a cross-sectional view taken along line VIII-VIII' in Fig. 7. As shown in Figs. 7 and 8, an elastic wave device 10C according to the fourth preferred embodiment differs from the first preferred embodiment in that the extraction wiring 34 is connected to the connection portion 40.

[0065] 7 , one end of the lead-out wiring 34 is connected to the counter electrode 33 in the cavity portion 14. The lead-out wiring 34 extends in the X direction on the side opposite to the upper electrode 31, and the other end of the lead-out wiring 34 is connected to the connection portion 40.

[0066] One end of the extending portion 32b of the lower electrode 32 is connected to the main electrode portion 32a. The extending portion 32b of the lower electrode 32 is formed in a crank shape. The other end of the extending portion 32b is disposed adjacent to the lead wiring 34 in the Y direction, extends in the X direction, and is connected to the connection portion 40.

[0067] The lead wiring 34 is connected to the connection terminal 72c (see FIG. 1 ), which is a ground terminal among the plurality of connection terminals 72, through the connection portion 40. Furthermore, the upper electrode 31 and the lower electrode 32 are connected to the connection terminals 72a and 72b (input terminal and output terminal (see FIG. 1 ) through which a signal is transmitted) among the plurality of connection terminals 72, respectively, through the connection portion 40.

[0068] 8 , one end of the lead-out wiring 34 is connected to the counter electrode 33 inside the cavity 14 and is led out to the first main surface 20a of the piezoelectric layer 20 through the opening 21. The other end of the lead-out wiring 34 is connected to the connection portion 40. That is, the counter electrode 33 formed inside the cavity 14 is connected to the lead-out wiring 34, the connection portion 40, the via 71, the connection terminal 72, and the bump 73. This forms a heat transfer path from the cavity 14 to the first main surface 20a of the piezoelectric layer 20. The counter electrode 33 may also be connected to the sealing portion 60 on the outer edge side of the support member 13. This connects the sealing portion 60 to the same reference potential (e.g., ground potential) as the counter electrode 33.

[0069] 7 and 8 , in the elastic wave device 10C according to the fourth preferred embodiment, the lead wiring 34 has a degree of freedom in its arrangement. Therefore, even if the resonator (the main electrode portion 31 a of the upper electrode 31 and the main electrode portion 32 a of the lower electrode 32) is configured to be disposed in the center of the support member 13, the counter electrode 33 provided inside the cavity 14 is connected to one of the multiple connection portions 40 through the lead wiring 34. Alternatively, the counter electrode 33 is connected to the sealing portion 60 through the lead wiring 34 and the connection portion 40. This allows the elastic wave device 10C according to the fourth preferred embodiment to have good heat dissipation properties regardless of the position of the resonator within the support member 13. Furthermore, the elastic wave device 10C according to the fourth preferred embodiment can ensure a ground path regardless of the position of the resonator within the support member 13.

[0070] 9 is a plan view showing an elastic wave device according to a fifth embodiment. As shown in FIG. 9 , an elastic wave device 10D according to the fifth embodiment has a different configuration from the first embodiment described above in that it includes a resonator formed by stacking a piezoelectric layer 20, an upper electrode 31, and a lower electrode 32, and a plurality of other resonators 101 and 102 that are different from the resonator.

[0071] The resonators 101 and 102 are, for example, BAW elements, and are arranged on the outer edge side of the support member 13. The resonator including the main electrode portion 31 a of the upper electrode 31 and the main electrode portion 32 a of the lower electrode 32 is arranged in the center of the support member 13.

[0072] 9 , the plurality of connection parts 40 are arranged along the outer edge of the support member 13 and are also arranged in the center of the support member 13. In the resonator arranged in the center of the support member 13, the counter electrode 33 provided inside the cavity 14 is connected to the connection part 40 arranged in the center of the support member 13 through the lead wiring 34.

[0073] The elastic wave device 10D of this preferred embodiment has a degree of freedom in the arrangement of the lead wiring 34 and the connection portion 40, and therefore has good heat dissipation properties even when multiple resonators 101, 102 are arranged on the support member 13. The resonators arranged in the center of the support member 13 can ensure a ground path through the connection portion 40 also arranged in the center.

[0074] 10 is a plan view showing an elastic wave device according to a modification of the fifth embodiment. As shown in FIG. 10 , elastic wave device 10E according to the modification of the fifth embodiment differs from the fifth embodiment in that counter electrode 33 of a resonator located in the center of support member 13 is connected to connection portion 40 via another resonator 102.

[0075] The counter electrode 33 of the resonator located in the center of the support member 13 is connected to the electrode 15 of the other resonator 102 through the lead wire 34 and the opening 22. The electrode 15 of the resonator 102 is connected to the connection portion 40 through the opening 23 and the lead wire 35. The electrode 15 of the other resonator 102 may be an electrode provided in the cavity portion like the counter electrode 33, or any of the electrodes of the resonator 102 may be used.

[0076] In this way, even when the resonator is arranged in the center, the elastic wave device 10E according to the modification of the fifth embodiment can ensure a heat dissipation path and a ground path through the other resonators 101 and 102.

[0077] The configurations of the elastic wave devices 10D and 10E according to the fifth embodiment and the modifications thereof can be combined with the first to fourth embodiments described above.

[0078] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0079] The present disclosure may also have the following configurations.

[0080] (1) An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface, an upper electrode provided on the first main surface of the piezoelectric layer, a lower electrode provided on the second main surface of the piezoelectric layer, a support member disposed opposite the second main surface of the piezoelectric layer and having a cavity portion provided in at least a region where the upper electrode and the lower electrode overlap, a counter electrode provided inside the cavity portion and disposed opposite the lower electrode, and an extraction structure connected to the counter electrode and extracted to the first main surface side of the piezoelectric layer. (2) The elastic wave device described in (1), wherein, in a plan view, an area of ​​the cavity portion is larger than an area of ​​an excitation region where the upper electrode and the lower electrode are arranged to overlap. (3) The elastic wave device according to (1) or (2), wherein the piezoelectric layer has an opening provided in a region that does not overlap with the upper electrode and the lower electrode, a lid portion disposed opposite the first main surface of the piezoelectric layer, a sealing portion provided between the lid portion and the support member, and a lead-out wiring having one end connected to the counter electrode inside the cavity portion, led out to the first main surface side of the piezoelectric layer through the opening, and the other end connected to the sealing portion, the lead-out structure being the lead-out wiring. (4) The elastic wave device according to (1) or (2), including: a lid portion disposed opposite the first main surface of the piezoelectric layer; and a sealing portion disposed between the lid portion and the support member and having a lower end embedded in the support member, wherein the cavity portion is disposed from a region where the upper electrode and the lower electrode overlap to the sealing portion located inside the support member, wherein the lower end side of the sealing portion is connected to the counter electrode inside the cavity portion and the upper end side of the sealing portion is connected to the lid portion on the first main surface side of the piezoelectric layer, and the lead-out structure is the sealing portion. (5) The elastic wave device according to any one of (1) to (4), including a back electrode provided on a surface of the support member opposite to the piezoelectric layer, wherein the counter electrode is connected to the back electrode through a via that penetrates the support member.(6) The elastic wave device according to (1), wherein the piezoelectric layer has an opening provided in a region not overlapping with the upper electrode and the lower electrode, a lid portion disposed opposite the first main surface of the piezoelectric layer, a connection terminal provided on a surface of the lid portion opposite the piezoelectric layer, a connection portion provided between the lid portion and the support member and connected to the connection terminal through a via hole penetrating the lid portion, and a lead-out wiring having one end connected to the counter electrode inside the cavity portion, drawn out to the first main surface of the piezoelectric layer through the opening, and the other end connected to the connection portion, the lead-out structure being the lead-out wiring. (7) The elastic wave device according to any one of (1) to (6), wherein the counter electrode is connected to a reference potential. (8) The elastic wave device according to (5), wherein the counter electrode and the back electrode are connected to a reference potential. (9) The elastic wave device according to (6), further comprising a sealing portion that seals the gap between the lid portion and the support member, the sealing portion extending along an outer edge of the support member in a plan view, and the connection portion being located inside the sealing portion. (10) The elastic wave device according to any one of (1) to (9), further comprising a piezoelectric layer containing single crystal lithium niobate or lithium tantalate.

[0081] REFERENCE SIGNS LIST 10, 10A, 10B, 10C, 10D, 10E Acoustic wave device 11 Support substrate 12 Insulating layer 13 Support member 14 Cavity portion 20 Piezoelectric layer 20a First main surface 20b Second main surface 21 Opening 31 Upper electrode 32 Lower electrode 33 Counter electrode 34, 35 Lead wiring 36 Back surface electrode 40 Connection portion 50 Sacrificial layer 60, 60A Sealing portion 61 First sealing portion 62 Second sealing portion 70 Lid portion 72, 72a, 72b, 72c Connection terminal 73 Bump

Claims

1. An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface; an upper electrode provided on the first main surface of the piezoelectric layer; a lower electrode provided on the second main surface of the piezoelectric layer; a support member arranged opposite the second main surface of the piezoelectric layer and having a cavity portion in at least a region where the upper electrode and the lower electrode overlap; a counter electrode provided inside the cavity portion and arranged opposite the lower electrode; and an extraction structure connected to the counter electrode and extracted to the first main surface side of the piezoelectric layer.

2. The elastic wave device according to claim 1, wherein the area of ​​the cavity portion in a plan view is larger than the area of ​​an excitation region where the upper electrode and the lower electrode are arranged to overlap each other.

3. The elastic wave device of claim 1 or 2, wherein the piezoelectric layer has an opening provided in an area not overlapping with the upper electrode and the lower electrode, a lid portion arranged opposite the first main surface of the piezoelectric layer, a sealing portion provided between the lid portion and the support member, and an extension wiring having one end connected to the opposing electrode inside the cavity portion and extended through the opening to the first main surface side of the piezoelectric layer and the other end connected to the sealing portion, the extension structure being the extension wiring.

4. An elastic wave device as described in claim 1 or claim 2, comprising: a lid portion arranged opposite the first main surface of the piezoelectric layer; and a sealing portion arranged between the lid portion and the support member, with a lower end side embedded within the support member, wherein the cavity portion is provided from a region where the upper electrode and the lower electrode overlap to the sealing portion located within the support member, the lower end side of the sealing portion is connected to the opposing electrode within the cavity portion, and the upper end side of the sealing portion is connected to the lid portion on the first main surface side of the piezoelectric layer, and the extraction structure is the sealing portion.

5. An elastic wave device as claimed in any one of claims 1 to 4, further comprising a back electrode provided on the surface of the support member opposite the piezoelectric layer, and the opposing electrode is connected to the back electrode through a via that passes through the support member.

6. The elastic wave device of claim 1, wherein the piezoelectric layer has an opening provided in an area not overlapping with the upper electrode and the lower electrode, a lid portion arranged opposite the first main surface of the piezoelectric layer, a connection terminal provided on the surface of the lid portion opposite the piezoelectric layer, a connection portion provided between the lid portion and the support member and connected to the connection terminal through a via that penetrates the lid portion, and an outgoing wiring having one end connected to the opposing electrode inside the cavity portion and drawn out to the first main surface side of the piezoelectric layer through the opening and the other end connected to the connection portion, the outgoing structure being the outgoing wiring.

7. The elastic wave device according to claim 1, wherein the opposing electrode is connected to a reference potential.

8. The acoustic wave device according to claim 5, wherein the opposing electrode and the rear electrode are connected to a reference potential.

9. The elastic wave device according to claim 6, further comprising a sealing portion that seals between the lid portion and the support member, the sealing portion extending along an outer edge of the support member in a plan view, and the connection portion being located more inward than the sealing portion.

10. The acoustic wave device according to any one of claims 1 to 9, wherein the piezoelectric layer contains single crystal lithium niobate or lithium tantalate.

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