Elastic wave resonator and electronic device

Abstract

This elastic wave resonator includes: a piezoelectric layer having a first main surface and a second main surface on an opposite side from the first main surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer in between; a plurality of surface electrodes provided on the first main surface of the piezoelectric layer for electrically connecting the first electrode and the second electrode to an external substrate; a first acoustic reflecting portion formed of a laminate including a first low acoustic impedance layer and a first high acoustic impedance layer, the first low acoustic impedance layer being provided on the first main surface of the piezoelectric layer and on the plurality of surface electrodes, and the first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; and a support member provided on the first main surface side of the piezoelectric layer, on the side opposite from the piezoelectric layer of the first acoustic reflecting portion. In the first acoustic reflecting portion, the first low acoustic impedance layer is made of an insulating material, and the first high acoustic impedance layer is made of a conductive material.

Description

Acoustic wave resonator and electronic device

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

[0002] Patent Document 1 describes an acoustic wave resonator (referred to in Patent Document 1 as a bulk acoustic wave (BAW) device) that includes a piezoelectric layer, top and bottom electrodes, an acoustic reflector (referred to in Patent Document 1 as a Bragg mirror), and a surface electrode (referred to in Patent Document 1 as a connector) for connection to an external circuit.

[0003] Special table 2018-514156 publication

[0004] Such an elastic wave resonator is required to have good heat dissipation properties so that heat generated in the excitation portion can be efficiently released to the outside.

[0005] An object of the present invention is to provide an acoustic wave resonator and an electronic device having good heat dissipation properties.

[0006] an elastic wave resonator according to one aspect of the present invention, comprising: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer sandwiched therebetween; a plurality of surface electrodes provided on the first main surface side of the piezoelectric layer and electrically connecting the first electrode and the second electrode to an external substrate; a first acoustic reflecting portion formed of a laminate including a first low acoustic impedance layer and a first high acoustic impedance layer provided on the first main surface side of the piezoelectric layer and on the plurality of surface electrodes, the first low acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; and a support member provided on the first main surface side of the piezoelectric layer on the side opposite the piezoelectric layer of the first acoustic reflecting portion, wherein the first low acoustic impedance layer is made of an insulating material and the first high acoustic impedance layer is made of a conductive material.

[0007] An electronic device according to one embodiment includes the above-described acoustic wave resonator, a module substrate on which the acoustic wave resonator is mounted, and a sealing resin that covers the acoustic wave resonator and contacts at least each side surface of the piezoelectric layer and the first acoustic reflector.

[0008] The acoustic wave resonator and electronic device of the present invention have excellent heat dissipation properties.

[0009] FIG. 1 is a circuit diagram illustrating an acoustic wave filter according to a first preferred embodiment of the present invention. FIG. 2 is a plan view illustrating the acoustic wave filter according to the first preferred embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a configuration of an acoustic wave resonator included in the acoustic wave filter according to the first preferred embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a first modified example of the first preferred embodiment. FIG. 5 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to the first modified example of the first preferred embodiment, with actual dimensional ratios. FIG. 6 is a cross-sectional view illustrating a portion of an electronic device including an acoustic wave resonator according to the first modified example of the first preferred embodiment. FIG. 7 is an explanatory diagram illustrating a manufacturing method of an acoustic wave resonator according to the first modified example of the first preferred embodiment. FIG. 8 is an explanatory diagram illustrating a manufacturing method of an acoustic wave resonator according to the first modified example of the first preferred embodiment. FIG. 9 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a second preferred embodiment of the present invention. FIG. 10 is an explanatory diagram illustrating a manufacturing method of an acoustic wave resonator according to the second preferred embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a third preferred embodiment of the present invention. FIG. 12 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to the third preferred embodiment of the present invention, with actual dimensional ratios. Fig. 13 is an explanatory diagram for explaining a manufacturing method of an elastic wave resonator according to a third embodiment. Fig. 14 is a cross-sectional view showing a configuration of an elastic wave resonator according to a second modified example of the first embodiment. Fig. 15 is a cross-sectional view showing an electronic device according to a fourth embodiment.

[0010] 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.

[0011] 1 is a circuit diagram illustrating an acoustic wave filter according to a first embodiment. As shown in FIG. 1 , an acoustic wave filter 51 according to the first embodiment includes a plurality of series arm resonators 61 a, 61 b, 61 c, 61 d, and 61 e, a plurality of parallel arm resonators 62 a, 62 b, 62 c, and 62 d, an input terminal 60A, an output terminal 60B, and ground terminals 63 and 64. At least one of the series arm resonators 61 a, 61 b, 61 c, 61 d, and 61 e and the parallel arm resonators 62 a, 62 b, 62 c, and 62 d is a bulk acoustic wave (BAW) element that utilizes bulk waves in a thickness extensional vibration mode or a thickness shear vibration mode.

[0012] The plurality of series arm resonators 61a, 61b, 61c, 61d, and 61e are connected in series to a signal path between the input terminal 60A and the output terminal 60B. The plurality of parallel arm resonators 62a, 62b, 62c, and 62d are connected in parallel between the signal path between the input terminal 60A and the output terminal 60B and ground terminals 63 and 64. The acoustic wave filter 51 according to the first embodiment is a so-called ladder filter.

[0013] One terminal of each of the series-connected series arm resonators 61a, 61b, 61c, 61d, and 61e is electrically connected to the input terminal 60A, and the other terminal is electrically connected to the output terminal 60B. One terminal of the parallel arm resonator 62a is electrically connected to a signal path connecting the series arm resonators 61a and 61b, and the other terminal is electrically connected to a ground terminal 63. One terminal of the parallel arm resonator 62b is electrically connected to a signal path connecting the series arm resonators 61b and 61c, and the other terminal is electrically connected to the ground terminal 63. One terminal of the parallel arm resonator 62c is electrically connected to a signal path connecting the series arm resonator 61c and 61d, and the other terminal is electrically connected to a ground terminal 64. One terminal of the parallel arm resonator 62 d is electrically connected to the signal path connecting the series arm resonators 61 d and 61 e , and the other terminal is electrically connected to the ground terminal 64 .

[0014] The configurations and numbers of the series arm resonators 61 a, 61 b, 61 c, 61 d, and 61 e and the parallel arm resonators 62 a, 62 b, 62 c, and 62 d in the acoustic wave filter 51 can be changed as needed depending on the desired filter characteristics. For example, the acoustic wave filter 51 may include at least one series arm resonator and at least one parallel arm resonator. The acoustic wave filter 51 may also include impedance elements such as inductors and capacitors.

[0015] 2 is a plan view showing an acoustic wave filter according to the first preferred embodiment. As shown in Fig. 2, an acoustic wave filter 51 includes a plurality of series arm resonators 61a, 61b, 61c, 61d, and 61e, a plurality of parallel arm resonators 62a, 62b, 62c, and 62d, and a plurality of terminals (an input terminal 60A, an output terminal 60B, and ground terminals 63, 64, 65, 66, and 67) disposed on a support member 11. The connections of the series arm resonators 61a, 61b, 61c, 61d, and 61e, the parallel arm resonators 62a, 62b, 62c, and 62d, and the plurality of terminals are the same as those in Fig. 1, and therefore, repeated description will be omitted.

[0016] The input terminal 60A and the output terminal 60B are located at diagonally opposite corners of the support member 11. The ground terminals 63, 64, 65, and 66 are located on the periphery of the support member 11. The ground terminal 67 is located in a region overlapping with the excitation portion 28 (see FIG. 4) of the series arm resonator 61c. The location of the ground terminal 67 will be described later with reference to FIG. 4.

[0017] In the following description, when it is not necessary to distinguish between the multiple series arm resonators 61a, 61b, 61c, 61d, and 61e and the multiple parallel arm resonators 62a, 62b, 62c, and 62d, they will simply be referred to as elastic wave resonators 10.

[0018] Next, the detailed configuration of the elastic wave resonator 10 (e.g., the series arm resonator 61a) included in the elastic wave filter 51 will be described. Fig. 3 is a cross-sectional view showing the configuration of an elastic wave resonator included in the elastic wave filter according to the first preferred embodiment. Note that the configuration of the elastic wave resonator 10 shown in Fig. 3 is not limited to the series arm resonator 61a, and can also be applied to the configurations of other resonators included in the elastic wave filter 51.

[0019] 3 , the acoustic wave resonator 10 includes a support member 11, a piezoelectric layer 20, a first electrode 21, a second electrode 22, an interconnection 23, a via 24, a surface electrode 25, a first acoustic reflector 31, and a second acoustic reflector 32. The acoustic wave resonator 10 further includes a protective layer 41 and a highly viscoelastic layer 43. As shown in FIG. 3 , the first acoustic reflector 31, the first electrode 21 and the interconnection 23 a, the piezoelectric layer 20, the second electrode 22 and the interconnection 23 b, the second acoustic reflector 32, and the highly viscoelastic layer 43 are stacked in this order on the lower surface of the support member 11. The surface electrode 25 and the protective layer 41 are stacked on the upper surface of the support member 11.

[0020] 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).

[0021] In addition, in the Z direction, the direction from the piezoelectric layer 20 toward the support member 11 and the surface electrode 25 may be referred to as "up" or "upper," and the direction from the support member 11 and the surface electrode 25 toward the piezoelectric layer 20 may be referred to as "down" or "lower." However, the terms "up" and "down" are used merely to define the relative positional relationship of parts, and do not limit the spatial arrangement and position of the BAW resonator.

[0022] The support member 11 is provided opposite the first main surface 20a of the piezoelectric layer 20. The support member 11 is a flat plate-shaped member made of silicon (Si), quartz crystal, etc. The material of the support member 11 includes at least one of boron nitride (BN), aluminum nitride (AlN), and silicon carbide (SiC) in addition to silicon (Si).

[0023] These materials are preferred because they have high thermal conductivity while providing sufficient insulation so as not to degrade the filter characteristics. Furthermore, these materials are preferably single-crystal materials. Alternatively, sintered bodies containing these single-crystal particles may be used. Here, heat conduction through an object involves heat transport by electrons and heat transfer by lattice vibration. To ensure that the support member 11 has sufficient insulation to prevent degradation of the filter characteristics, it is necessary to enhance heat transfer by lattice vibration. The above-mentioned materials used for the support member 11 have constituent elements with similar atomic sizes, and being single-crystal allows for good thermal conductivity.

[0024] 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 piezoelectric layer 20 is a substrate made of a single crystal of aluminum nitride (AlN). The material of the piezoelectric layer 20 is not limited to this, and aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), etc. may also be used. The thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 1 μm or less. The piezoelectric layer 20 may have a structure in which a plurality of piezoelectric films having different polarization directions are stacked.

[0025] The first electrode 21 is provided on the top (first main surface 20a) of the piezoelectric layer 20. The second electrode 22 is provided on the bottom (second main surface 20b) of the piezoelectric layer 20. The first electrode 21 and the second electrode 22 face each other in the Z direction, sandwiching the piezoelectric layer 20 therebetween. In other words, the piezoelectric layer 20 is disposed between the first electrode 21 and the second electrode 22 in the Z direction. This allows bulk waves to propagate between the first electrode 21 and the second electrode 22. In the following description, the region where the first electrode 21 and the second electrode 22 overlap in a planar view may be described as the excitation portion 28 of the resonator.

[0026] 2, the portions corresponding to the excitation portion 28 of each resonator are shown hatched. As shown in Fig. 2, the first electrode 21 and the second electrode 22 constituting the excitation portion 28 are each rectangular. However, this is not limiting, and the first electrode 21 and the second electrode 22 may be other shapes such as circular or polygonal.

[0027] The first electrode 21 and the second electrode 22 are formed of a conductive material such as aluminum (Al), platinum (Pt), gold (Au), copper (Cu), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), ruthenium (Ru), tantalum (Ta), iridium (Ir), or an alloy containing at least one of these materials. The first electrode 21 and the second electrode 22 may also be a laminate film containing these materials.

[0028] The lead-out wiring 23a is provided on the first main surface 20a of the piezoelectric layer 20 in the same layer as the first electrode 21, and is connected to one side of the first electrode 21 in the X direction. The lead-out wiring 23b is provided on the second main surface 20b of the piezoelectric layer 20 in the same layer as the second electrode 22, and is connected to the other side of the second electrode 22 in the X direction. The lead-out wirings 23a and 23b are formed of the same material as the first electrode 21 and the second electrode 22, respectively. However, the lead-out wirings 23a and 23b may be made of a different material from the first electrode 21 and the second electrode 22.

[0029] The first acoustic reflector 31 is provided on the first main surface 20a side of the piezoelectric layer 20, covering the first electrode 21 and the lead-out wiring 23a. In other words, the first acoustic reflector 31 is provided between the piezoelectric layer 20 and the support member 11 in the Z direction. The support member 11 is provided on the opposite side of the first acoustic reflector 31 to the piezoelectric layer 20 in the Z direction.

[0030] The first acoustic reflecting portion 31 is made of a laminate of first low acoustic impedance layers 31 a, 31 c, and 31 e having a relatively low acoustic impedance, and first high acoustic impedance layers 31 b and 31 d having a higher acoustic impedance than the first low acoustic impedance layers 31 a, 31 c, and 31 e. The first low acoustic impedance layer 31 a, the first high acoustic impedance layer 31 b, the first low acoustic impedance layer 31 c, the first high acoustic impedance layer 31 d, and the first low acoustic impedance layer 31 e are laminated in this order on the first main surface 20 a of the piezoelectric layer 20.

[0031] The first low acoustic impedance layers 31a, 31c, and 31e are made of an insulating material. The first high acoustic impedance layers 31b and 31d are made of a conductive material. The first low acoustic impedance layers 31a, 31c, and 31e are made of, for example, silicon oxide (SiO ２) layers. The first high acoustic impedance layers 31b and 31d are made of a metal material such as tungsten (W), molybdenum (Mo), ruthenium (Ru), or platinum (Pt). However, without being limited thereto, the first high acoustic impedance layers 31b and 31d may be made of an alloy containing at least one of the above metal materials. Note that the conductive material here refers to a material having an electrical resistivity of 1.0×10 －６ An insulating material is a material with an electrical resistivity of less than 1.0 x 10 －６ This refers to materials with a resistance of Ω·m or more.

[0032] Note that there is no particular limitation on the number of stacked first low acoustic impedance layers 31a, 31c, 31e and first high acoustic impedance layers 31b, 31d in the first acoustic reflecting portion 31. The first acoustic reflecting portion 31 may have four or fewer layers, or six or more layers. It is sufficient that at least one of the first high acoustic impedance layers 31b, 31d is disposed farther from the piezoelectric layer 20 than the first low acoustic impedance layers 31a, 31c, 31e.

[0033] The second acoustic reflector 32 is provided to cover the second electrode 22 and the lead-out wiring 23b on the second main surface 20b side of the piezoelectric layer 20. In other words, the second acoustic reflector 32 is located on the opposite side of the piezoelectric layer 20 from the support member 11 and the plurality of surface electrodes 25 in the Z direction.

[0034] The second acoustic reflecting portion 32 is made of a laminate of second low acoustic impedance layers 32 a, 32 c having a relatively low acoustic impedance and second high acoustic impedance layers 32 b, 32 d having a higher acoustic impedance than the second low acoustic impedance layers 32 a, 32 c. The second low acoustic impedance layer 32 a, the second high acoustic impedance layer 32 b, the second low acoustic impedance layer 32 c, and the second high acoustic impedance layer 32 d are laminated in this order on the second main surface 20 b of the piezoelectric layer 20.

[0035] The second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d are all made of insulating materials. The second low acoustic impedance layers 32a, 32c are made of silicon oxide (SiO ２The second high acoustic impedance layers 32b and 32d are made of, for example, silicon nitride (SiN) or aluminum oxide (Al ２ O ３ ), tantalum oxide (Ta ２ O ５ ), hafnium oxide (HfO ２ ) or other dielectric layer.

[0036] Note that there is no particular limitation on the number of layers of the second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d in the second acoustic reflecting portion 32. The second acoustic reflecting portion 32 may have three or fewer layers, or five or more layers. It is sufficient that at least one of the second high acoustic impedance layers 32b, 32d is disposed farther from the piezoelectric layer 20 than the second low acoustic impedance layers 32a, 32c.

[0037] The plurality of surface electrodes 25 are provided on the first main surface 20a side of the piezoelectric layer 20. Specifically, the plurality of surface electrodes 25 are provided on the surface of the support member 11 opposite to the surface on which the first acoustic reflector 31 is provided. One surface electrode 25 is electrically connected to the lead-out wiring 23a through a via 24 that penetrates the support member 11 and the first acoustic reflector 31 in the Z direction. The other surface electrode 25 is electrically connected to the lead-out wiring 23b through a via 24 that penetrates the support member 11, the first acoustic reflector 31, and the piezoelectric layer 20 in the Z direction.

[0038] Each of the surface electrodes 25 is provided with an external terminal (e.g., an input terminal 60A, an output terminal 60B, etc.). The external terminals, such as the input terminal 60A and the output terminal 60B, are, for example, solder bumps or Au bumps. A protective layer 41 is provided to cover the surface electrodes 25 and the support member 11 and has openings in areas where the external terminals are provided. The protective layer 41 is formed of an insulating resin material and is also called a solder resist. With this configuration, the surface electrodes 25 electrically connect the first electrode 21 and the second electrode 22 constituting the excitation unit 28 to the module substrate 101 (see FIG. 15 ), which is an external substrate. Note that the acoustic wave resonator 10 does not necessarily have to have the external terminals and the protective layer 41.

[0039] When the distance from the external terminal to the excitation unit 28 is LMAX and the thickness of the support member 11 is Ds in a plan view, it is preferable that LMAX / Ds be between 1 and 6. This is because, although it is the excitation unit 28 that generates heat during operation of the elastic wave resonator, if the distance from the excitation unit 28 to the external terminal is too large, the heat generated in the excitation unit 28 is not discharged to the outside, which may deteriorate the power durability of the elastic wave resonator. Here, the distance LMAX from the external terminal to the excitation unit 28 refers to the longest distance from the point of contact between the external terminal and the surface electrode 25 that is closest to the excitation unit 28 (the external terminal-side base point) to the outer edge of the excitation unit 28. Note that LMAX and Ds can be measured by observing the elastic wave filter using an optical microscope, an infrared camera, an X-ray microscope, or the like.

[0040] A specific example will be described below. An elastic wave resonator model was created using lithium niobate (thermal conductivity: 6.4 W / (m·k)) and lithium tantalate (thermal conductivity: 3.6 W / (m·k)) as the piezoelectric layer 20, and a thermal simulation was performed with heat generation points set within the elastic wave resonator. A temperature drop curve, with the distance from the external terminal to the excitation unit 28 and the thickness of the support member 11 (thermal conductivity: 150 W / (m·k) and 370 W / (m·k)) as variables, showed that the heat dissipation effect significantly decreased when the support member thickness decreased so that LMAX / Ds exceeded 6. To ensure heat dissipation from the external terminal, it is preferable to increase the thickness of the support member 11 so that LMAX / Ds is 6 or less. Conversely, the heat dissipation effect plateaus even if the thickness of the support member 11 is increased as LMAX / Ds becomes less than 1. Therefore, from the perspective of reducing the height of the elastic wave filter, it is preferable to set LMAX / Ds to 1 or greater.

[0041] The high-viscoelastic layer 43 is provided on the side of the second acoustic reflecting portion 32 opposite to the piezoelectric layer 20, i.e., on the surface of the second acoustic reflecting portion 32 opposite to the surface on which the piezoelectric layer 20 is provided. The high-viscoelastic layer 43 has higher viscoelasticity than the second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d of the second acoustic reflecting portion 32. Furthermore, when the elastic wave resonator 10 is mounted on the module substrate 101 (see FIG. 6 ), a sealing resin 105 is provided to cover the elastic wave resonator 10. The high-viscoelastic layer 43 is made of a material having higher viscoelasticity than the sealing resin 105.

[0042] The highly viscoelastic layer 43 is made of a material having a relatively high viscoelasticity, such as a polyimide resin, polybenzoxazole, a urethane resin, a silicone resin, an acrylic resin, or a cycloolefin resin, while the sealing resin 105 is made of a material having a relatively low viscoelasticity, such as an epoxy resin (containing a filler).

[0043] Since the highly viscoelastic layer 43 is provided to cover the second acoustic reflector 32, it is possible to suppress fluctuations in the resonator characteristics due to the influence of the sealing resin 105 (see FIG. 6) provided as a protective material, etc.

[0044] With the above-described configuration, in the elastic wave resonator 10 of this embodiment, the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32 are provided on both sides of the piezoelectric layer 20, so that bulk waves in the thickness-extensional vibration mode or the thickness-shear vibration mode can be confined within the piezoelectric layer 20.

[0045] The first acoustic reflector 31, which is provided on the same side as the plurality of surface electrodes 25, contains an insulating material and a conductive material, and therefore has better thermal conductivity than when the first acoustic reflector 31 is made of an insulating material only. Furthermore, the support member 11 is provided between the first acoustic reflector 31 and the plurality of surface electrodes 25.

[0046] In the elastic wave resonator 10, in addition to a heat transfer path from the excitation portion 28 through the first electrode 21, the lead-out wiring 23 a, the via 24, and one of the surface electrodes 25, and a heat transfer path from the excitation portion 28 through the second electrode 22, the lead-out wiring 23 b, the via 24, and the other surface electrode 25, a heat transfer path is formed in which the heat is transferred in the Z direction from the excitation portion 28 to the support member 11 through a region of the first acoustic reflecting portion 31 containing a conductive material that overlaps with the first high acoustic impedance layers 31 b and 31 d.

[0047] As a result, the heat transferred to the support member 11 through the first acoustic reflector 31 spreads in the X and Y directions due to the heat spread effect of the support member 11, increasing the heat transfer area to the outside (for example, the module substrate 101 (see FIG. 6)), resulting in high heat dissipation capability. Furthermore, as shown in FIG. 5, the thickness of the support member 11 is thicker than other members such as the piezoelectric layer 20, the first acoustic reflector 31, and the second acoustic reflector 32, and therefore the heat spread effect is enhanced by providing the support member 11, which has good thermal conductivity, on the surface electrode 25 side.

[0048] Here, the support member 11 has a sufficient thickness to ensure the strength of the acoustic wave resonator, and the thermal conductivity of the material used therefor is greater than that of the insulating material used for the first low acoustic impedance layers 31a, 31c, and 31e. As described above, the support member 11 may be made of a material with high thermal conductivity to enhance heat dissipation and low electrical conductivity to avoid adversely affecting the acoustic wave resonator characteristics, such as high-resistivity silicon (Si), aluminum nitride (AlN), boron nitride (BN), or silicon carbide (SiC). The thermal conductivities of the various materials used for the support member 11 are, for example, as follows: The thermal conductivity of Si single crystal is approximately 150 W / (m×k); the thermal conductivity of AlN single crystal is approximately 270 W / (m×k); the thermal conductivity of BN single crystal is approximately 200 W / (m×k); and the thermal conductivity of SiC single crystal is approximately 370 W / (m×k).

[0049] Furthermore, the thermal conductivity of AlN ceramics is approximately 180 W / (m×k). The thermal conductivity of BN ceramics is approximately 180 W / (m×k). The thermal conductivity of SiC ceramics is approximately 170 W / (m×k). Note that the above thermal conductivities are not calculated as "theoretical values," but are measured using each material, and include variations in the manufacturing process and variations due to measurement conditions.

[0050] As described above, acoustic wave resonator 10 can improve the heat dissipation properties of heat generated in excitation portion 28. Furthermore, acoustic wave resonator 10 has good heat dissipation properties, which can improve the power durability.

[0051] In the first acoustic reflecting portion 31, the first high acoustic impedance layers 31b and 31d made of a conductive material have a higher acoustic impedance than an insulating material. That is, the ratio of the acoustic impedance of the first low acoustic impedance layers 31a, 31c, and 31e to the acoustic impedance of the first high acoustic impedance layers 31b and 31d is large. This improves the acoustic wave confinement and reflection effects in the first acoustic reflecting portion 31. This allows the acoustic wave resonator 10 to achieve good resonator characteristics.

[0052] Furthermore, in the first acoustic reflecting section 31, the first high acoustic impedance layers 31b and 31d are provided in a region overlapping with the excitation section 28, but are not provided in a region not overlapping with the excitation section 28. In other words, in the region overlapping with the excitation section 28, the first low acoustic impedance layer 31a, the first high acoustic impedance layer 31b, the first low acoustic impedance layer 31c, the first high acoustic impedance layer 31d, and the first low acoustic impedance layer 31e are laminated in this order. In the region not overlapping with the excitation section 28, the first low acoustic impedance layers 31a, 31c, and 31e are laminated in this order. This makes it possible to enhance the acoustic wave confinement and reflection effects in the region overlapping with the excitation section 28, while ensuring freedom in the arrangement of the vias 24 and the surface electrodes 25.

[0053] A first acoustic reflector 31 containing a conductive material is provided on the first main surface 20a side of the piezoelectric layer 20 (i.e., the surface electrode 25 side), and a second acoustic reflector 32 made of an insulating material is provided on the second main surface 20b side of the piezoelectric layer 20, so that heat generated in the excitation section 28 is efficiently conducted to the support member 11 side through the first acoustic reflector 31. Because the second acoustic reflector 32 is made of an insulating material, fluctuations in the resonator characteristics caused by external electromagnetic field influences (e.g., capacitive coupling or electromagnetic field coupling between the second acoustic reflector 32 and an external device) on the side of the piezoelectric layer 20 opposite the surface electrode 25 can be suppressed more effectively than when the second acoustic reflector 32 contains a conductive material.

[0054] In the second acoustic reflecting section 32, the second high acoustic impedance layers 32b, 32d are provided over the entire surface, including the region overlapping with the excitation section 28 and the region not overlapping with the excitation section 28. Therefore, the process of patterning the second high acoustic impedance layers 32b, 32d can be omitted when forming the second acoustic reflecting section 32. Furthermore, in the second acoustic reflecting section 32, the second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d are formed flat without any steps, which can suppress the occurrence of cracks.

[0055] Furthermore, in the elastic wave resonator 10 of this embodiment, the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32 are provided on either side of the piezoelectric layer 20, and therefore the strength of the piezoelectric layer 20 can be increased compared to a configuration in which a cavity portion 12 (see FIG. 11 ) is provided in the support member 11 instead of the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32.

[0056] Furthermore, lithium niobate or lithium tantalate is preferably used as the material for the piezoelectric layer 20. Lithium niobate or lithium tantalate has a higher dielectric constant than, for example, aluminum nitride (AlN). Therefore, by using lithium niobate or lithium tantalate for the piezoelectric layer 20, the elastic wave resonator 10 of this embodiment can be made smaller.

[0057] (First Modification of First Embodiment) Fig. 4 is a cross-sectional view showing the configuration of an elastic wave resonator according to a first modification of the first embodiment. Fig. 5 is a cross-sectional view showing the configuration of an elastic wave resonator according to a first modification of the first embodiment, with the actual dimensional ratios corresponding to the actual dimensions. Fig. 6 is a cross-sectional view showing a portion of an electronic device including an elastic wave resonator according to the first modification of the first embodiment. The elastic wave resonator 10A shown in Figs. 4 and 6 corresponds to, for example, the series arm resonator 61c in Fig. 2.

[0058] As shown in FIG. 4 , the elastic wave resonator 10A according to the first variant of the first embodiment differs from the first embodiment described above in that at least one of the multiple surface electrodes 25 is arranged in a region that overlaps with the excitation portion 28 in a planar view.

[0059] A ground terminal 67 made of a conductive material is provided on the surface electrode 25 at a position overlapping the excitation portion 28. As shown in Fig. 2, the surface electrode 25 at the position overlapping the excitation portion 28 is led out to a corner of the support member 11 through the connection wiring 26 and connected to the ground terminal 66. The ground terminals 66, 67 are, for example, solder bumps.

[0060] 2, the surface electrode 25 at the position overlapping with the excitation section 28 may be connected in any manner. Alternatively, the surface electrode 25 at the position overlapping with the excitation section 28 may be provided with only the ground terminal 67 and may not be connected to other wiring or terminals such as the connection wiring 26.

[0061] 6 , the elastic wave resonator 10A is mounted on a module substrate 101 via an input terminal 60A, an output terminal 60B, and a ground terminal 67. A sealing resin 105 is provided to cover the elastic wave resonator 10A. The sealing resin 105 is provided to fill the space between the module substrate 101 and the protective layer 41 of the elastic wave resonator 10A. The sealing resin 105 is also provided to cover the first acoustic reflector 31, the piezoelectric layer 20, the second acoustic reflector 32, the side surfaces of the support member 11, and the highly viscoelastic layer 43.

[0062] In the electronic device 100 including the acoustic wave resonator 10A of the first modification, the surface electrode 25 and the ground terminal 67 are provided in a region overlapping with the excitation unit 28, and the ground terminal 67 is in contact with the module substrate 101. This forms a heat transfer path extending in the Z direction from the excitation unit 28 through the region of the first acoustic reflecting unit 31 overlapping with the first high acoustic impedance layers 31b and 31d made of a conductive material, the support member 11, the surface electrode 25, and the ground terminal 67 to the module substrate 101. This allows the acoustic wave resonator 10A to improve the heat dissipation performance of heat generated in the excitation unit 28. Furthermore, the excellent heat dissipation performance of the acoustic wave resonator 10A allows for improved power durability.

[0063] (Method of Manufacturing Elastic Wave Resonator According to First Modification) Fig. 7 is a diagram illustrating a method of manufacturing an elastic wave resonator according to a first modification of the first embodiment. Fig. 8 is a diagram illustrating a method of manufacturing an elastic wave resonator according to the first modification of the first embodiment.

[0064] In the manufacturing method of the elastic wave resonator 10A, FIG. 7 shows the process up to the step of forming the first acoustic reflecting portion 31 on the first main surface 20 a of the piezoelectric layer 20 and bonding the support member, and FIG. 8 shows the process from the step of forming the second acoustic reflecting portion 32 on the second main surface 20 b of the piezoelectric layer 20 onwards.

[0065] 7, the piezoelectric layer 20 is bonded to a transfer substrate 200 (step ST1). The piezoelectric layer 20 is made of lithium niobate (LiNbO ３ The transfer substrate 200 is, for example, a silicon substrate. In step ST1, the piezoelectric layer 20 is thinned by processes such as grinding, lapping, and polishing. The piezoelectric layer 20 may also be formed using an ion slicing method.

[0066] The first electrode 21 and the lead wiring 23a are formed on the first main surface 20a of the piezoelectric layer 20 (step ST2).

[0067] Next, a first low acoustic impedance layer 31a constituting the first acoustic reflector 31 is formed on the first main surface 20a (the surface on the support member 11 side) of the piezoelectric layer 20 (step ST3). The first low acoustic impedance layer 31a is, for example, a silicon oxide film. A material with low density and low hardness is preferred for the low acoustic impedance layer.

[0068] In step ST3, the surface of the first low acoustic impedance layer 31a is planarized, thereby planarizing the convex portions of the first low acoustic impedance layer 31a formed corresponding to the first electrodes 21 and the lead wirings 23a.

[0069] Next, the first high acoustic impedance layer 31b constituting the first acoustic reflecting portion 31 is patterned (step ST4). The first high acoustic impedance layer 31b is, for example, a tungsten film, and the tungsten film is formed in the region overlapping with the excitation portion 28, while the tungsten film in the region not overlapping with the excitation portion 28 is removed.

[0070] Here, by reducing the variation in the pattern of the first high acoustic impedance layer 31b, variation in the resonator characteristics of the elastic wave resonator 10A can be suppressed. Therefore, it is preferable to pattern the first high acoustic impedance layer 31b using processing techniques, materials, and equipment that are effective for achieving high precision. Furthermore, a material with high density and Young's modulus is preferable for the high acoustic impedance layer, and is not limited to tungsten, but molybdenum, ruthenium, platinum, etc. can also be used.

[0071] Next, the first low acoustic impedance layer 31c, the first high acoustic impedance layer 31d, and the first low acoustic impedance layer 31e are formed in this order (step ST5). Specifically, a silicon oxide film is formed as the first low acoustic impedance layer 31c and planarized, a tungsten film is formed thereon as the first high acoustic impedance layer 31d and patterned, and then a first low acoustic impedance layer 31e is formed and planarized.

[0072] In the process of forming the first acoustic reflecting portion 31 shown in steps ST3 to ST5, the film properties and thicknesses of the first low acoustic impedance layers 31a, 31c, and 31e and the first high acoustic impedance layers 31b and 31d are optimized according to the desired resonance characteristics. Specifically, the total thickness of two adjacent layers (e.g., the total thickness of the first low acoustic impedance layer 31a and the first high acoustic impedance layer 31b) of the first acoustic reflecting portion 31, namely, the first low acoustic impedance layers 31a, 31c, and 31e and the first high acoustic impedance layers 31b and 31d, is preferably set to a thickness that is half the wavelength of the resonant wave at the sound speed within the first acoustic reflecting portion 31. However, the thickness is not limited to this, and may be a thickness that is different from the half wavelength, for example, to suppress unwanted waves.

[0073] The first acoustic reflecting portion 31 tends to have higher performance as a reflector when the impedance ratio of the high acoustic impedance layer / low acoustic impedance layer is large. For this reason, it is preferable to use the above-mentioned metal materials for the first high acoustic impedance layers 31b and 31d. Furthermore, by using a combination that increases the difference between the value of "density x Young's modulus" of the first high acoustic impedance layers 31b and 31d and the value of "density x Young's modulus" of the first low acoustic impedance layers 31a, 31c, and 31e, the performance as an acoustic reflector is improved, which is preferable.

[0074] Next, the first low acoustic impedance layer 31e located on the outermost layer of the first acoustic reflector 31 is planarized and smoothed, and then directly bonded to the support member 11 (step ST6). Direct bonding may be performed by hydrophilic bonding, surface activation bonding, atomic diffusion bonding, or the like. It is preferable to use, for example, a high-resistivity Si substrate as the support member 11. High-resistivity Si substrates are preferable in terms of their high processability and thermal conductivity, which facilitates reducing loss during singulation and ensuring power durability. In addition to Si, the support member 11 may be made of the aforementioned boron nitride, aluminum nitride, or silicon carbide.

[0075] Next, the transfer substrate 200 is removed (step ST7).

[0076] Next, as shown in FIG. 8, a second electrode 22 and an extraction wiring 23b are formed on the second main surface 20b of the piezoelectric layer 20 (the surface opposite the support member 11), and further, a second low acoustic impedance layer 32a, a second high acoustic impedance layer 32b, a second low acoustic impedance layer 32c, and a second high acoustic impedance layer 32d that constitute the second acoustic reflecting portion 32 are deposited in this order (step ST8).

[0077] Silicon oxide films are formed as the second low acoustic impedance layers 32 a and 32 c, and hafnium oxide films are formed as the second high acoustic impedance layers 32 b and 32 d. Furthermore, in the second acoustic reflecting portion 32, unlike the first acoustic reflecting portion 31 described above, it is not necessary to pattern the second high acoustic impedance layers 32 b and 312.

[0078] Next, a high-viscoelastic layer 43 having higher viscoelasticity than the material used for the second acoustic reflector 32 is formed (step ST9). The high-viscoelastic layer 43 is made of a material having higher viscoelasticity than the sealing resin 105 (see FIG. 6 ) that covers the acoustic wave resonator 10A. An example of the high-viscoelastic layer 43 is a polyimide film. Alternatively, the high-viscoelastic layer 43 may be made of an epoxy-based material other than polyimide, an olefin-based resin, benzocyclobutene, polybenzoxazole, silicone, or the like.

[0079] Next, the support member 11 is thinned (step ST10). This allows the acoustic wave resonator 10A to have a low profile. However, the support member 11 must be thick enough to prevent damage to the excitation portion 28, the first acoustic reflecting portion 31, and the second acoustic reflecting portion 32 and to prevent warping due to stress.

[0080] Next, photolithography and dry etching techniques are used to form through holes TH that penetrate the support member 11 and the first acoustic reflecting portion 31, and through holes TH that penetrate the support member 11, the first acoustic reflecting portion 31, and the piezoelectric layer 20 (step ST11). The through holes TH are formed at positions that overlap the lead-out wirings 23 a and 23 b, respectively, and the lead-out wirings 23 a and 23 b form the bottom surfaces of the through holes TH.

[0081] Next, the surface electrode 25, the connection wiring 26, and the via 24 are formed (step ST12). In step ST12, the surface electrode 25 is also provided in the region overlapping with the excitation portion 28.

[0082] Next, a protective layer 41 is formed to cover the surface electrodes 25 and the connection wiring 26, and openings are formed in the protective layer 41 in areas where terminals such as the input terminal 60A, the output terminal 60B, and the ground terminal 67 will be provided. Solder bumps are formed on the plurality of surface electrodes 25 as the input terminals 60A, the output terminals 60B, and the ground terminal 67 (step ST13). At this time, the ground terminal 67 is provided on the surface electrodes 25 in an area overlapping with the excitation section 28.

[0083] The external terminals are not limited to solder bumps, and may be formed by directly bonding an external substrate such as Ag or Cu paste, or Cu or Au wiring on the elastic wave resonator 10A to the external substrate such as the module substrate 101 (see FIG. 6 ). In this case, the Cu or Au wiring corresponds to the external terminals. Alternatively, the wiring metal on the elastic wave resonator 10A may be electrically connected to the external substrate such as the module substrate 101 (see FIG. 6 ) using a metal wire such as Au. In this case, the wiring corresponds to the external terminals.

[0084] Next, the elastic wave resonator 10A is manufactured by dividing the substrate into individual pieces. Through the above-described steps, the surface electrode 25 is formed on the support member 11 on the side opposite the piezoelectric layer 20, the first acoustic reflector 31 containing a metal material is formed between the piezoelectric layer 20 and the support member 11 (and the surface electrode 25), and the second acoustic reflector 32 made of an insulating material is formed on the piezoelectric layer 20 on the side opposite the support member 11 (and the surface electrode 25).

[0085] Although the method for manufacturing the elastic wave resonator 10A according to the first modified example has been described with reference to FIGS. 7 and 8, the elastic wave resonator 10 according to the first preferred embodiment can be manufactured by partially modifying steps ST12 and ST13.

[0086] 9 is a cross-sectional view showing the configuration of an elastic wave resonator according to a second embodiment. As shown in FIG. 9, an elastic wave resonator 10B according to the second embodiment differs from the first modification of the first embodiment in that a second acoustic reflecting portion 32A includes a conductive material.

[0087] A second low acoustic impedance layer 32Aa, a second high acoustic impedance layer 32Ab, a second low acoustic impedance layer 32Ac, a second high acoustic impedance layer 32Ad, and a second low acoustic impedance layer 32Ae, which constitute the second acoustic reflecting portion 32A, are stacked in this order on the second main surface 20b of the piezoelectric layer 20 (the surface opposite to the support member 11 and the surface electrode 25).

[0088] The second low acoustic impedance layers 32Aa, 32Ac, and 32Ae are made of an insulating material. The second high acoustic impedance layers 32Ab and 32Ad are made of a conductive material. The second low acoustic impedance layers 32Aa, 32Ac, and 32Ae are made of, for example, silicon oxide (SiO ２ The second high acoustic impedance layers 32Ab and 32Ad are made of a metal material such as tungsten (W), molybdenum (Mo), ruthenium (Ru), or platinum (Pt). However, the second high acoustic impedance layers 32Ab and 32Ad are not limited thereto, and may be made of an alloy containing at least one of the above metal materials.

[0089] The second low acoustic impedance layers 32Aa, 32Ac, and 32Ae are made of the same material as the first low acoustic impedance layers 31a, 31c, and 31e of the first acoustic reflecting portion 31. The second high acoustic impedance layers 32Ab and 32Ad are made of the same material as the first high acoustic impedance layers 31b and 31d of the first acoustic reflecting portion 31. However, this is not limitative, and the second acoustic reflecting portion 32A may be made of a different material from that of the first acoustic reflecting portion 31.

[0090] In the elastic wave resonator 10B of this embodiment, the second acoustic reflecting portion 32A contains a conductive material. Therefore, compared to the first embodiment, which is formed solely of an insulating material, the second high acoustic impedance layers 32Ab, 32Ad, which are made of a conductive material, have a higher acoustic impedance than the insulating material. That is, the ratio of the acoustic impedance of the second low acoustic impedance layers 32Aa, 32Ac, 32Ae to the acoustic impedance of the second high acoustic impedance layers 32Ab, 32Ad is large. This improves the acoustic wave confinement and reflection effects of the second acoustic reflecting portion 32A. Therefore, the elastic wave resonator 10B can achieve excellent resonator characteristics.

[0091] 10 is an explanatory diagram for describing a method for manufacturing an elastic wave resonator according to a second embodiment. Note that, in FIG. 10 , the description of the method for manufacturing the elastic wave resonator 10A according to the first modified example described above will be omitted.

[0092] 10 , a first acoustic reflecting portion 31 is formed on the first main surface 20 a of the piezoelectric layer 20, and the support member 11 is directly bonded to the first acoustic reflecting portion 31 (step ST21). Note that, before step ST21, steps similar to steps ST1 to ST6 shown in FIG. 7 are performed.

[0093] Next, a second electrode 22 and an extraction wiring 23b are formed on the second main surface 20b of the piezoelectric layer 20, and then the second low acoustic impedance layer 32Aa, the second high acoustic impedance layer 32Ab, the second low acoustic impedance layer 32Ac, the second high acoustic impedance layer 32Ad, and the second low acoustic impedance layer 32Ae that constitute the second acoustic reflection portion 32A are deposited (step ST22).

[0094] Silicon oxide films are formed as the second low acoustic impedance layers 32Aa, 32Ac, and 32Ae. Tungsten films are formed as the second high acoustic impedance layers 32Ab and 32Ad. The tungsten films are formed in the regions of the second high acoustic impedance layers 32Ab and 32Ad that overlap with the excitation section 28, and the tungsten films are removed in the regions that do not overlap with the excitation section 28. This forms the second acoustic reflecting section 32A that includes an insulating material and a conductive material.

[0095] In step ST22, a highly viscoelastic layer 43 is further formed on the surface of the second acoustic reflecting portion 32A opposite to the piezoelectric layer 20.

[0096] 8 , the supporting member 11 is thinned (step ST23), through holes TH are formed using photolithography and dry etching techniques (step ST24), surface electrodes 25, connection wiring 26, and vias 24 are formed (step ST25), and solder bumps are formed on the plurality of surface electrodes 25 as input terminals 60A, output terminals 60B, and ground terminals 67 (step ST26). In steps ST25 and ST26, the surface electrodes 25 and the ground terminals 67 are also provided in the region overlapping with the excitation section 28.

[0097] Next, the resultant structure is singulated to produce the elastic wave resonators 10B. Through the above-described process, a first acoustic reflector 31 containing an insulating material and a conductive material is formed on the side of the piezoelectric layer 20 facing the support member 11 and the surface electrode 25, and a second acoustic reflector 32A containing an insulating material and a conductive material is formed on the side of the piezoelectric layer 20 opposite the side facing the support member 11 and the surface electrode 25.

[0098] Third Embodiment Fig. 11 is a cross-sectional view showing the configuration of an elastic wave resonator according to a third embodiment. Fig. 12 is a cross-sectional view showing the configuration of an elastic wave resonator according to the third embodiment, corresponding to the actual dimensional ratio. As shown in Fig. 11 , an elastic wave resonator 10C according to the third embodiment differs from the first and second embodiments in that a cavity 12 is provided instead of the second acoustic reflecting portions 32 and 32A.

[0099] The elastic wave resonator 10C according to the third preferred embodiment has a cover member 13 disposed opposite the second main surface 20b of the piezoelectric layer 20. The cover member 13 is formed of, for example, a silicon substrate. A sealing portion 14 seals the gap between the cover member 13 and the piezoelectric layer 20. The sealing portion 14 is formed in a frame shape surrounding the excitation portion 28 in a plan view. This defines a cavity 12 between the second main surface 20b of the piezoelectric layer 20 and the cover member 13. The second electrode 22 and the lead wiring 23b are disposed within the cavity 12.

[0100] In the third embodiment, a cavity 12 is provided on the second main surface 20b of the piezoelectric layer 20. Therefore, compared to the first embodiment in which, for example, a second acoustic reflecting portion 32 (see FIG. 3) made of only an insulating material is provided, the energy trapping effect of the elastic wave resonator 10C is enhanced, and good resonator characteristics can be obtained.

[0101] Furthermore, the elastic wave resonator 10C according to the third embodiment has a first acoustic reflector 31 containing a conductive material on the first main surface 20a side of the piezoelectric layer 20 (i.e., the side facing the support member 11 and the surface electrode 25), and a cavity 12 on the second main surface 20b side of the piezoelectric layer 20 (i.e., the side opposite the support member 11 and the surface electrode 25). Therefore, heat generated in the excitation unit 28 is transferred to the support member 11 and the surface electrode 25 through the first acoustic reflector 31, but is less likely to be transferred to the cover member 13, which faces the excitation unit 28 across the cavity 12. Therefore, the heat generated in the excitation unit 28 reaches the external module substrate 101 through the first acoustic reflector 31, the support member 11, the surface electrode 25, and external terminals such as the ground terminal 67. 12 , the thickness of the support member 11 is greater than that of other members such as the piezoelectric layer 20 and the first acoustic reflector 31, and therefore the heat spread effect can be enhanced by providing the support member 11, which has good thermal conductivity, on the surface electrode 25 side. Therefore, the acoustic wave resonator 10C can improve the heat dissipation performance of the heat generated in the excitation portion 28.

[0102] 13 is an explanatory diagram for describing a method for manufacturing an elastic wave resonator according to a third embodiment. Note that in FIG. 13 , details common to the method for manufacturing elastic wave resonator 10A according to the first modified example described above will be omitted.

[0103] 13, a first acoustic reflecting portion 31 is formed on the first main surface 20a of the piezoelectric layer 20, and the support member 11 is directly bonded to the first acoustic reflecting portion 31 (step ST31). Note that, before step ST31, steps similar to steps ST1 to ST6 shown in FIG. 7 are performed.

[0104] Next, a second electrode 22 and an extraction wiring 23b are formed on the second main surface 20b of the piezoelectric layer 20, and then a metal layer that will become the sealing portion 14 is formed. The surface layer of the metal layer is preferably made of Au, which is resistant to surface oxidation when bonded to the cover member 13. A metal film having an Au surface layer is also patterned in the area of ​​the cover member 13 that will be bonded to the sealing portion 14. The second main surface 20b of the piezoelectric layer 20 and the cover member 13 are then bonded via the sealing portion 14 (step ST32). In step ST32, the cover member 13 is aligned so that the metal film formed on the cover member 13 contacts the sealing portion 14. Heat is then applied while a load is applied to perform metal thermal diffusion bonding, thereby sealing the cavity 12.

[0105] 8, photolithography and dry etching techniques are used to form through holes TH (step ST33), surface electrodes 25, connection wiring 26, and vias 24 are formed (step ST34), and solder bumps are formed on the plurality of surface electrodes 25 as input terminals 60A, output terminals 60B, and ground terminals 67 (step ST35). In steps ST34 and ST35, surface electrodes 25 and ground terminals 67 are also provided in areas overlapping with excitation portions 28.

[0106] Next, the elastic wave resonator 10C is manufactured by singulating the piezoelectric layer 20. Through the above-described process, a first acoustic reflector 31 containing an insulating material and a conductive material is formed on the side of the piezoelectric layer 20 facing the support member 11 and the surface electrode 25, and a cavity 12 is formed as a second acoustic reflector on the side of the piezoelectric layer 20 opposite the side facing the support member 11 and the surface electrode 25.

[0107] 14 is a cross-sectional view showing the configuration of an elastic wave resonator according to a second modification of the first embodiment. As shown in Fig. 14 , elastic wave resonator 10D according to the second modification of the first embodiment differs from the first modification in that multiple bumps (input terminal 60A, terminal 67A) are provided on the same surface electrode 25 that is arranged in a region overlapping with excitation portion 28.

[0108] In addition, the first high acoustic impedance layers 31b and 31d of the first acoustic reflecting portion 31 are metal films, and in a planar view, a surface electrode 25 and at least one bump (terminal 67A) are arranged at a position overlapping the first high acoustic impedance layers 31b and 31d, which are metal films.

[0109] With the above-described configuration, the elastic wave resonator 10D according to the second modification of the first embodiment can further improve the heat dissipation property of the heat generated in the excitation portion 28. Furthermore, since the elastic wave resonator 10D has good heat dissipation property, it can improve the power durability.

[0110] 15 is a cross-sectional view showing an electronic device according to a fourth embodiment. The electronic device 100 according to the fourth embodiment is a communication module used in, for example, a mobile terminal such as a mobile phone, a smartphone, or a tablet terminal, or a personal computer with a communication function. Alternatively, the electronic device 100 may be used for backhaul communication between base stations and between a base station and a core network.

[0111] As shown in FIG. 15, the electronic device 100 includes a module substrate 101, acoustic wave filters 51 and 52, a power amplifier 102, a high-frequency switch 103, surface-mounted components 104 (such as inductors and coils), and a sealing resin 105.

[0112] The module substrate 101 may be, for example, a printed circuit board made of resin or a ceramic substrate such as LTCC (Low Temperature Co-fired Ceramics) or HTCC (High Temperature Co-fired Ceramics).The module substrate 101 may be a single-layer substrate or a multi-layer substrate in which multiple dielectric layers are stacked.

[0113] The acoustic wave filters 51 and 52 include at least one of the acoustic wave resonators 10, 10A, 10B, and 10C according to the first to third embodiments described above. The acoustic wave filter 52 may have a configuration similar to or different from that of the acoustic wave filter 51. The acoustic wave filters 51 and 52 each including the acoustic wave resonator 10 include a first acoustic reflector 31 containing an insulating material and a conductive material and a support member 11 on the surface electrode 25 side (the module substrate 101 side). Therefore, heat generated in the excitation unit 28 is efficiently conducted to the module substrate 101 through the first acoustic reflector 31 and the support member 11. Therefore, the acoustic wave filters 51 and 52 can improve the heat dissipation performance of the heat generated in the excitation unit 28.

[0114] The sealing resin 105 is formed by transfer molding, compression molding, or the like, to cover the acoustic wave filters 51 and 52, the power amplifier 102, the high-frequency switch 103, and the surface-mounted components 104. As described above, the sealing resin 105 covers the side surfaces of the support member 11, the first acoustic reflecting portion 31, and the second acoustic reflecting portion 32 of the acoustic wave resonator 10. In other words, no other package or connecting member is present between the acoustic wave resonator 10 and the module substrate 101 or the sealing resin 105. This allows the electronic device 100 to be miniaturized.

[0115] It should be noted that the electronic device 100 shown in FIG. 15 is merely a schematic illustration, and the types, number, arrangement, etc. of the components mounted on the electronic device 100 can be changed as appropriate.

[0116] 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.

[0117] The present disclosure may also have the following configurations.

[0118] a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer sandwiched therebetween; a plurality of surface electrodes provided on the first main surface side of the piezoelectric layer and for electrically connecting the first electrode and the second electrode to an external substrate; a first acoustic reflecting section provided on the first main surface side of the piezoelectric layer and on the plurality of surface electrodes side, the first acoustic reflecting section being a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; and a support member provided on the first main surface side of the piezoelectric layer on the opposite side to the piezoelectric layer of the first acoustic reflecting section, wherein the first low acoustic impedance layer is made of an insulating material and the first high acoustic impedance layer is made of a conductive material. (2) The elastic wave resonator according to (1), further comprising: a second acoustic reflecting portion provided on the second principal surface side of the piezoelectric layer and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having a higher acoustic impedance than the second low acoustic impedance layer, wherein the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting portion are both made of an insulating material. (3) The elastic wave resonator according to (1), further comprising: a second acoustic reflecting portion provided on the second principal surface side of the piezoelectric layer and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having a higher acoustic impedance than the second low acoustic impedance layer, wherein the second low acoustic impedance layer of the second acoustic reflecting portion is made of an insulating material and the second high acoustic impedance layer is made of a conductive material. (4) The elastic wave resonator according to (2) or (3), further comprising: a high viscoelastic layer disposed on the opposite side of the second acoustic reflecting portion from the piezoelectric layer, wherein the high viscoelasticity is higher than the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting portion. (5) The elastic wave resonator according to (1), further comprising a cover member provided opposite the second main surface of the piezoelectric layer, wherein a cavity is provided between the second main surface of the piezoelectric layer and the cover member.(6) The elastic wave resonator according to any one of (1) to (5), wherein the support member is made of a material containing at least one of silicon, boron nitride, aluminum nitride, and silicon carbide. (7) The elastic wave resonator according to (6), wherein the support member contains a single crystal material or single crystal particles of any one of silicon, boron nitride, aluminum nitride, and silicon carbide. (8) The elastic wave resonator according to any one of (1) to (7), wherein the piezoelectric layer contains lithium niobate or lithium tantalate. (9) The elastic wave resonator according to any one of (1) to (8), wherein, when a region where the first electrode and the second electrode overlap with each other across the piezoelectric layer is defined as an excitation portion, the plurality of surface electrodes are provided on a surface of the support member opposite the first acoustic reflecting portion, and at least one of the plurality of surface electrodes is arranged in a region that overlaps with the excitation portion in a plan view. (10) The elastic wave resonator according to (9), wherein a plurality of bumps are provided on the same surface electrode that is arranged in a region overlapping with the excitation portion. (11) The elastic wave resonator according to (9), wherein the first high acoustic impedance layer is a metal film, and the surface electrode is arranged in a position that overlaps with the metal film in a planar view. (12) An electronic device comprising: the elastic wave resonator according to any one of (1) to (9), a module substrate on which the elastic wave resonator is mounted, and a sealing resin that is provided to cover the elastic wave resonator and in contact with at least each side surface of the piezoelectric layer and the first acoustic reflecting portion. (13) An electronic device comprising: the elastic wave resonator according to (5), a module substrate on which the elastic wave resonator is mounted, and a sealing resin that is provided to cover the elastic wave resonator and in contact with at least each side surface of the piezoelectric layer and the first acoustic reflecting portion.

[0119] REFERENCE SIGNS LIST 10, 10A, 10B, 10C Acoustic wave resonator 11 Support member 12 Cavity 13 Cover member 14 Sealing portion 20 Piezoelectric layer 20a First main surface 20b Second main surface 21 First electrode 22 Second electrode 25 Surface electrode 28 Excitation portion 31 First acoustic reflecting portion 31a, 31c, 31e First low acoustic impedance layer 31b, 31d First high acoustic impedance layer 32, 32A Second acoustic reflecting portion 32a, 32c, 32Aa, 32Ac, 32Ae Second low acoustic impedance layer 32b, 32d, 32Ab, 32Ad Second high acoustic impedance layer 43 High viscoelastic layer 51, 52 Acoustic wave filter 61a, 61b, 61c, 61d, 61e Series arm resonator 62a, 62b, 62c, 62d parallel arm resonators 100 electronic device 101 module substrate 105 sealing resin

Claims

1. An elastic wave resonator comprising: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer in between; a plurality of surface electrodes provided on the first main surface side of the piezoelectric layer and for electrically connecting the first electrode and the second electrode to an external substrate; a first acoustic reflecting section provided on the first main surface side of the piezoelectric layer and facing the plurality of surface electrodes, the first acoustic reflecting section being a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; and a support member provided on the first main surface side of the piezoelectric layer on the opposite side to the piezoelectric layer of the first acoustic reflecting section, wherein the first low acoustic impedance layer is made of an insulating material and the first high acoustic impedance layer is made of a conductive material.

2. An elastic wave resonator according to claim 1, further comprising a second acoustic reflecting portion provided on the second principal surface side of the piezoelectric layer and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having a higher acoustic impedance than the second low acoustic impedance layer, wherein the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting portion are both made of an insulating material.

3. An elastic wave resonator according to claim 1, further comprising a second acoustic reflecting portion provided on the second principal surface side of the piezoelectric layer and comprising a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having an acoustic impedance higher than that of the second low acoustic impedance layer, wherein the second low acoustic impedance layer of the second acoustic reflecting portion is made of an insulating material and the second high acoustic impedance layer is made of a conductive material.

4. An elastic wave resonator as described in claim 2 or claim 3, which has a high viscoelastic layer arranged on the opposite side of the piezoelectric layer of the second acoustic reflecting section and having higher viscoelasticity than the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting section.

5. The elastic wave resonator according to claim 1, further comprising a cover member provided opposite to the second main surface of the piezoelectric layer, and a cavity provided between the second main surface of the piezoelectric layer and the cover member.

6. An elastic wave resonator according to any one of claims 1 to 5, wherein the support member is made of a material containing at least one of silicon, boron nitride, aluminum nitride, and silicon carbide.

7. The elastic wave resonator according to claim 6, wherein the support member contains a single crystal material or single crystal particles of any of silicon, boron nitride, aluminum nitride, and silicon carbide.

8. The elastic wave resonator according to any one of claims 1 to 7, wherein the piezoelectric layer contains lithium niobate or lithium tantalate.

9. An elastic wave resonator according to any one of claims 1 to 8, wherein when an area where the first electrode and the second electrode overlap with the piezoelectric layer sandwiched therebetween is defined as an excitation section, the plurality of surface electrodes are provided on a surface of the support member opposite the first acoustic reflection section, and at least one of the plurality of surface electrodes is positioned in an area that overlaps with the excitation section in a plan view.

10. The elastic wave resonator according to claim 9, wherein a plurality of bumps are provided on the same surface electrode that is arranged in a region overlapping with the excitation portion.

11. The elastic wave resonator according to claim 9, wherein the first high acoustic impedance layer is a metal film, and the surface electrode is disposed at a position overlapping the metal film in a plan view.

12. An electronic device comprising: an elastic wave resonator according to any one of claims 1 to 9; a module substrate on which the elastic wave resonator is mounted; and a sealing resin provided to cover the elastic wave resonator and in contact with at least each side surface of the piezoelectric layer and the first acoustic reflecting portion.

13. An electronic device comprising: the elastic wave resonator according to claim 5; a module substrate on which the elastic wave resonator is mounted; and a sealing resin provided to cover the elastic wave resonator and in contact with at least each side surface of the piezoelectric layer and the first acoustic reflecting portion.

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