Elastic wave filter

Abstract

To provide an elastic wave filter with improved heat dissipation.SOLUTION: An elastic wave filter 1 includes: a substrate 10 having principal surfaces 10a and 10b facing each other; a substrate 70 having a principal surface 70a facing the principal surface 10a; functional electrodes 25 and 26 disposed on the principal surfaces 70a; and a frame body 30 disposed between the principal surfaces 10a and 70a and surrounding the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in a plan view. An outer surface of the frame body 30 is rougher than an inner surface of the frame body 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an acoustic wave filter. [Background technology]

[0002] Patent Document 1 discloses an electronic component including a support substrate and a lid, an acoustic wave element disposed on the support substrate, a frame disposed between the support substrate and the lid and surrounding the acoustic wave element, and a protective layer covering the outer periphery of the frame. According to this document, the protective layer is capable of suppressing a decrease in airtightness. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-189428 Summary of the Invention [Problem to be solved by the invention]

[0004] With the demand for higher output power in mobile communications, acoustic wave filters with improved airtightness and heat dissipation are in demand.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an acoustic wave filter with improved heat dissipation properties. [Means for solving the problem]

[0006] In order to achieve the above object, an acoustic wave filter according to one embodiment of the present invention comprises a first substrate having a first main surface and a second main surface facing each other, a second substrate having a third main surface facing the first main surface, a functional electrode arranged on the third main surface, and a frame body arranged between the first and third main surfaces and surrounding the functional electrode when the first and third main surfaces are viewed in a plane, wherein the outer surface of the frame body is rougher than the inner surface of the frame body. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an acoustic wave filter with improved heat dissipation properties. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of an acoustic wave filter according to an embodiment of the present invention; [Figure 2] FIG. 1 is a plan view of an acoustic wave filter according to an embodiment. [Figure 3A] 1A and 1B are a plan view and a cross-sectional view schematically illustrating a first example of an acoustic wave resonator included in an acoustic wave filter according to an embodiment. [Figure 3B] FIG. 4 is a cross-sectional view schematically illustrating a second example of an acoustic wave resonator included in an acoustic wave filter according to an embodiment. [Figure 3C] FIG. 10 is a cross-sectional view schematically illustrating a third example of an acoustic wave resonator included in an acoustic wave filter according to an embodiment. [Figure 4A] 10A and 10B are diagrams showing electron microscope images of the outer cross section and outer surface of a frame body according to an embodiment. [Figure 4B] 10A and 10B are diagrams showing electron microscope images of the inner cross section and inner surface of a frame body according to an embodiment. [Figure 5] 10A and 10B are diagrams illustrating a method for evaluating the surface area of ​​a frame body according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangements, and connection forms shown in the following embodiments are merely examples and are not intended to limit the present invention. Among the components in the following embodiments, components that are not recited in independent claims will be described as optional components. Furthermore, the sizes or size ratios of the components shown in the drawings are not necessarily strict.

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

[0011] In the circuit configuration of the present disclosure, "connected" includes not only direct connection by electrodes and / or wiring conductors, but also electrical connection via matching elements such as inductors and capacitors, and switch circuits. "Connected between A and B" means connected to both A and B between A and B.

[0012] Furthermore, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not only represent strict meanings, but also include substantially equivalent ranges, for example, including an error of a few percent.

[0013] (Embodiment) [1 Structure of acoustic wave filter 1] Fig. 1 is a cross-sectional view of an acoustic wave filter 1 according to an embodiment. Fig. 2 is a plan view of the acoustic wave filter 1 according to an embodiment. Fig. 2 is a plan view (transparent) of a main surface 70a of a substrate 70 from the positive side of the z axis. Fig. 1 is a cross-sectional view taken along line II in Fig. 2.

[0014] As shown in Figures 1 and 2, the acoustic wave filter 1 includes substrates 10 and 70, a frame 30, functional electrodes 25 and 26, a signal conductor 20, a via conductor 11, an insulating film 13, a planar electrode 12, and a bump electrode 40.

[0015] The substrate 10 is an example of a first substrate and has opposing principal surfaces 10a (first principal surface) and 10b (second principal surface). In this embodiment, the substrate 10 contains silicon. When the substrate 10 contains silicon, the thermal conductivity is increased compared to when the substrate 10 is made of a resin material. This improves the heat dissipation of the acoustic wave filter 1. Furthermore, the processing accuracy of the substrate 10 is improved.

[0016] The substrate 70 is an example of a second substrate, and has principal surfaces 70a (third principal surface) and 70b facing each other. The principal surfaces 10a and 70a face each other. In this embodiment, the substrate 70 has piezoelectricity.

[0017] The functional electrodes 25 and 26 are disposed on the main surface 70a, and in this embodiment, are part of an IDT (InterDigital Transducer) electrode that performs electromechanical transduction with the substrate 70. Examples of the structures of the functional electrodes 25 and 26 will be described with reference to FIGS. 3A to 3C.

[0018] The frame 30 is disposed between the principal surfaces 10a and 70a, and is configured to surround the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan. The frame 30 is a wall disposed along the outer periphery of the substrates 10 and 70, which have a rectangular shape in plan view. The frame 30 is configured as a laminate of a support layer 31 and bonding layers 32 and 33.

[0019] The bonding layer 32 is an example of a first bonding layer, is in contact with the substrate 10, and is configured to surround the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan. The bonding layer 33 is an example of a second bonding layer, and is in contact with the substrate 70, and is configured to surround the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan. The support layer 31 is disposed between the bonding layers 32 and 33, and is configured to surround the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan.

[0020] Support layer 31 includes a conductor portion mainly composed of, for example, aluminum (Al). Bonding layers 32 and 33 each include a conductor portion mainly composed of, for example, at least one of aluminum (Al), copper (Cu), gold (Au), platinum (Pt), and titanium (Ti). In other words, frame 30 includes a conductor portion made of metal.

[0021] The frame body 30 separates the internal space of the frame body 30, in which the functional electrodes 25 and 26 are formed, from the external space of the frame body 30. Furthermore, since the frame body 30 includes a conductor portion made of metal, it is possible to ensure the airtightness of the internal space with high precision. Furthermore, by setting the frame body 30 to, for example, a ground potential, it is possible to block external noise. The frame body 30 may have ventilation holes, in which case the airtightness of the internal space does not need to be ensured. Furthermore, the frame body 30 may be made of a resin material when it is not necessary to ensure the airtightness of the internal space.

[0022] The frame 30 may be formed of only the support layer 31 without including the bonding layers 32 and 33 .

[0023] Furthermore, a resin member may be disposed on the outer periphery of the frame body 30 so as to be in contact with the outer periphery surface of the frame body 30. This can improve the moisture resistance of the frame body 30 and also reinforce the mechanical strength of the frame body 30.

[0024] The signal conductor 20 is an example of a first conductor, and is connected to the functional electrode 25 or 26. When the principal surfaces 10a and 70a are viewed from above, the signal conductor 20 is disposed inside the frame 30 and is in contact with the principal surfaces 10a and 70a. The signal conductor 20 transmits signals passing through the functional electrode 25 or 26. The signal conductor 20 is composed of a laminate of a main body 21 and bonding layers 22 and 23.

[0025] The bonding layer 22 is bonded to the substrate 10. The bonding layer 23 is in contact with the substrate 70 and connected to the bus bar electrode 27 or 28. The main body portion 21 is disposed between the bonding layers 22 and 23.

[0026] Main body portion 21 has the same material composition as support layer 31. Bonding layer 22 has the same material composition as bonding layer 32. Bonding layer 23 has the same material composition as bonding layer 33. Note that main body portion 21 and support layer 31 may be formed by the same film formation process, bonding layers 22 and 32 may be formed by the same film formation process, and bonding layers 23 and 33 may be formed by the same film formation process.

[0027] Furthermore, the functional electrodes 25 and 26 may be formed using the same material and film-forming process as the main body 21 or the bonding layer 23 .

[0028] Furthermore, portions of the functional electrodes 25 and 26 may be electrically connected to the bonding layer 33 of the frame 30 via the bonding layer 23 and set to the ground potential.

[0029] The signal conductor 20 may be formed only from the main body portion 21 without including the bonding layers 22 and 23 .

[0030] The via conductor 11 is an electrode disposed on the substrate 10 from the principal surface 10a toward the principal surface 10b and connected to the signal conductor 20. In this embodiment, the via conductor 11 is a through electrode filled in a cavity that penetrates the substrate 10 between the principal surface 10a and the principal surface 10b. The via conductor 11 is made of, for example, a metal member whose main component is Cu (copper).

[0031] In addition, via conductor 11 does not have to be a single via conductor extending from main surface 10a to main surface 10b, but may have a configuration in which multiple via conductors are connected via a planar electrode formed within substrate 10.

[0032] The insulating film 13 is disposed on the main surface 10b and is, for example, a silicon oxide film. The insulating film 13 may be omitted. Alternatively, an insulating film may be disposed on the main surface 70a.

[0033] The planar electrode 12 is disposed on the principal surface 10b and is bonded to the via conductors 11. The bump electrode 40 is bonded to the planar electrode 12 and is made of, for example, solder or a metal material mainly composed of Au (gold). The bump electrode 40 is bonded to, for example, an electrode on a mounting substrate on which the acoustic wave filter 1 is mounted.

[0034] According to the above configuration, a compact acoustic wave filter 1 in which functional electrodes 25 and 26 are arranged in a space surrounded by substrates 10, 70 and frame 30 can be provided.

[0035] Note that the acoustic wave filter 1 according to this preferred embodiment does not necessarily have to include at least one of the via conductor 11, the insulating film 13, the planar electrode 12, and the bump electrode 40.

[0036] [2 Structure of Functional Electrodes 25 and 26] Next, exemplary structures of the functional electrodes 25 and 26 will be described. FIG. 3A is a plan view and a cross-sectional view schematically illustrating a first example of an acoustic wave resonator 60 constituting the acoustic wave filter 1 according to an embodiment. The drawings illustrate the basic structure of the acoustic wave resonator 60 constituting the acoustic wave filter 1. Note that the acoustic wave resonator 60 shown in FIG. 3A is intended to illustrate a typical structure of an acoustic wave resonator constituting the acoustic wave filter 1, and the number and length of electrode fingers constituting the electrodes are not limited thereto.

[0037] The acoustic wave resonator 60 is composed of a piezoelectric substrate 50 and comb-shaped electrodes 60a and 60b.

[0038] As shown in (a) of FIG. 3A, a pair of comb-shaped electrodes 60a and 60b facing each other is formed on the piezoelectric substrate 50. The comb-shaped electrode 60a is composed of a plurality of parallel electrode fingers 61a (first electrode fingers) and a busbar electrode 62a (first busbar electrode) connecting one ends of the plurality of electrode fingers 61a together. The comb-shaped electrode 60b is composed of a plurality of parallel electrode fingers 61b (second electrode fingers) and a busbar electrode 62b (second busbar electrode) connecting one ends of the plurality of electrode fingers 61b together. The plurality of electrode fingers 61a and 61b are formed in a direction perpendicular to the acoustic wave propagation direction (X-axis direction). The busbar electrode 62a and the busbar electrode 62b are arranged facing each other with the electrode fingers 61a and 61b interposed therebetween. The comb-shaped electrodes 60a and 60b form an IDT electrode 54.

[0039] When the acoustic wave filter 1 according to this embodiment performs electromechanical transduction using surface acoustic waves, the substrate 70 shown in FIGS. 1 and 2 corresponds to the piezoelectric substrate 50. Furthermore, each of the functional electrodes 25 and 26 shown in FIGS. 1 and 2 includes a plurality of electrode fingers 61 a and a plurality of electrode fingers 61 b. Furthermore, each of the busbar electrodes 27 and 28 shown in FIG. 2 is either one of the busbar electrodes 62 a or 62 b.

[0040] The acoustic wave resonator 60 may have reflectors on both ends of the IDT electrode 54 in the acoustic wave propagation direction (X-axis direction).

[0041] As shown in FIG. 3A(b), the IDT electrode 54 has a laminated structure of an adhesive layer 540 and a main electrode layer 542, for example.

[0042] The adhesion layer 540 is a layer for improving adhesion between the piezoelectric substrate 50 and the main electrode layer 542, and is made of, for example, Ti. The main electrode layer 542 is made of, for example, Al containing 1% Cu. The protective layer 55 is formed to cover the comb-shaped electrodes 60a and 60b. The protective layer 55 is a layer for protecting the main electrode layer 542 from the external environment, adjusting the frequency-temperature characteristics, and improving moisture resistance, and is, for example, a dielectric film mainly composed of silicon dioxide. The adhesion layer 540 may be formed of the same material and by the same film-forming process as the bonding layer 23 shown in FIG. 1, and the main electrode layer 542 may be formed of the same material and by the same film-forming process as the main body 21 shown in FIG. 1.

[0043] The materials constituting the adhesion layer 540, the main electrode layer 542, and the protective layer 55 are not limited to those described above. Furthermore, the IDT electrode 54 does not have to have the laminated structure described above. The IDT electrode 54 may be made of a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a laminate of multiple layers made of the above metals or alloys. Furthermore, the protective layer 55 does not necessarily have to be formed.

[0044] Next, the layered structure of the piezoelectric substrate 50 will be described.

[0045] As shown in (c) of Figure 3A, the piezoelectric substrate 50 includes a high acoustic speed support substrate 51, a low acoustic speed film 52, and a piezoelectric film 53, and has a structure in which the high acoustic speed support substrate 51, the low acoustic speed film 52, and the piezoelectric film 53 are stacked in this order.

[0046] The piezoelectric film 53 is made of, for example, a θ° Y-cut X-propagation LiTaO3 piezoelectric single crystal or piezoelectric ceramics (a lithium tantalate single crystal or ceramics cut along a plane whose normal is an axis rotated θ° from the Y axis around the X axis, and through which surface acoustic waves propagate in the X-axis direction). The material and cut angle θ of the piezoelectric single crystal used as the piezoelectric film 53 are appropriately selected depending on the required specifications of each filter.

[0047] The high acoustic velocity support substrate 51 is a substrate that supports the low acoustic velocity film 52, the piezoelectric film 53, and the IDT electrode 54. The high acoustic velocity support substrate 51 is also a substrate in which the acoustic velocity of bulk waves in the high acoustic velocity support substrate 51 is faster than that of acoustic waves such as surface waves and boundary waves that propagate through the piezoelectric film 53, and functions to confine the surface acoustic waves to the portion where the piezoelectric film 53 and the low acoustic velocity film 52 are laminated, preventing leakage below the high acoustic velocity support substrate 51. Examples of materials that can be used for the high acoustic velocity support substrate 51 include piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectrics such as aluminum oxide, silicon oxynitride, diamond-like carbon (DLC), and diamond; semiconductors such as silicon; and materials containing any of the above materials as a main component. The spinel includes an aluminum compound containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0048] The low acoustic velocity film 52 is a film in which the acoustic velocity of the bulk waves in the low acoustic velocity film 52 is slower than that of the bulk waves propagating through the piezoelectric film 53, and is disposed between the piezoelectric film 53 and the high acoustic velocity support substrate 51. This structure and the property of the acoustic waves that energy is concentrated in a medium with an essentially low acoustic velocity suppress leakage of surface acoustic wave energy outside the IDT electrode. The low acoustic velocity film 52 can be made of a dielectric material such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound of silicon oxide with fluorine, carbon, or boron added, or a material containing any of the above materials as its main component.

[0049] The above-described laminated structure of piezoelectric substrate 50 makes it possible to significantly increase the Q value at the resonant frequency and anti-resonant frequency compared to a conventional structure using a single-layer piezoelectric substrate. In other words, an acoustic wave resonator with a high Q value can be configured, and a filter with low insertion loss can be configured using the acoustic wave resonator.

[0050] The high acoustic velocity support substrate 51 may have a laminated structure of a support substrate and a high acoustic velocity film in which the acoustic velocity of the propagating bulk waves is faster than that of the surface waves and boundary waves, etc., that propagate through the piezoelectric film 53. In this case, the high acoustic velocity film may be made of the same material as the high acoustic velocity support substrate 51. The support substrate may be made of, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectric materials such as diamond and glass; semiconductors such as silicon and gallium nitride; resins; or materials containing any of the above materials as a main component.

[0051] In this specification, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be in a single crystal, polycrystalline, or amorphous state, or a mixture of these.

[0052] 3B is a cross-sectional view schematically illustrating a second example of an acoustic wave resonator 60 constituting the acoustic wave filter 1 according to the embodiment. In the acoustic wave resonator 60 illustrated in FIG. 3A, the IDT electrode 54 is formed on the piezoelectric substrate 50 having the piezoelectric film 53. However, the substrate on which the IDT electrode 54 is formed may be a piezoelectric single crystal substrate 57 consisting of a single piezoelectric layer, as illustrated in FIG. 1 and FIG. 2. In this case, the substrate 70 illustrated in FIGS. 1 and 2 corresponds to the piezoelectric single crystal substrate 57.

[0053] The piezoelectric single crystal substrate 57 is made of, for example, a piezoelectric single crystal of LiNbO3. The elastic wave resonator according to this example is made up of the LiNbO3 piezoelectric single crystal substrate 57, an IDT electrode 54, and a protective layer 58 formed on the piezoelectric single crystal substrate 57 and the IDT electrode 54.

[0054] The laminate structure, material, cut angle, and thickness of the piezoelectric film 53 and the piezoelectric single crystal substrate 57 may be changed as appropriate depending on the required pass characteristics of the acoustic wave filter 1. Even an acoustic wave resonator using a LiTaO piezoelectric substrate having a cut angle other than the above-described cut angle can achieve the same effects as the acoustic wave resonator 60 using the piezoelectric film 53.

[0055] The piezoelectric substrate on which the IDT electrode 54 is formed may have a structure in which a support substrate, an energy trapping layer, and a piezoelectric film are laminated in this order. The IDT electrode 54 is formed on the piezoelectric film. The piezoelectric film may be made of, for example, a LiTaO3 piezoelectric single crystal or a piezoelectric ceramic. The support substrate is a substrate that supports the piezoelectric film, the energy trapping layer, and the IDT electrode 54.

[0056] The energy trapping layer is composed of one or more layers, and the velocity of the bulk acoustic waves propagating through at least one of the layers is greater than the velocity of the acoustic waves propagating near the piezoelectric film. For example, the energy trapping layer may have a laminated structure of a low acoustic velocity layer and a high acoustic velocity layer. The low acoustic velocity layer is a film in which the acoustic velocity of the bulk waves in the low acoustic velocity layer is slower than the acoustic velocity of the acoustic waves propagating through the piezoelectric film. The high acoustic velocity layer is a film in which the acoustic velocity of the bulk waves in the high acoustic velocity layer is faster than the acoustic velocity of the acoustic waves propagating through the piezoelectric film. The support substrate may also be the high acoustic velocity layer.

[0057] The energy trapping layer may also be an acoustic impedance layer having a configuration in which low acoustic impedance layers with a relatively low acoustic impedance and high acoustic impedance layers with a relatively high acoustic impedance are alternately stacked.

[0058] 3C is a cross-sectional view schematically illustrating a third example of an acoustic wave resonator 60 included in the acoustic wave filter 1 according to the embodiment. In FIG. 3C, a bulk acoustic wave resonator is illustrated as the acoustic wave resonator of the acoustic wave filter 1. As illustrated in the drawing, the bulk acoustic wave resonator includes, for example, a support substrate 65, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68, and is configured such that the support substrate 65, the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68 are layered in this order.

[0059] The support substrate 65 is a substrate, such as a silicon substrate, for supporting the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68. The support substrate 65 has a cavity in the region that contacts the lower electrode 66. This allows the piezoelectric layer 67 to vibrate freely.

[0060] The lower electrode 66 is an example of a first planar electrode, and is formed on one surface of the support substrate 65. The upper electrode 68 is an example of a second planar electrode, and is formed on one surface of the support substrate 65. The lower electrode 66 and the upper electrode 68 are made of a material such as Al containing 1% Cu.

[0061] The piezoelectric layer 67 is an example of a piezoelectric thin film, and is formed between the lower electrode 66 and the upper electrode 68. The piezoelectric layer 67 is mainly composed of at least one of ZnO (zinc oxide), AlN (aluminum nitride), PZT (lead zirconate titanate), KN (potassium niobate), LN (lithium niobate), LT (lithium tantalate), quartz crystal, and LiBO (lithium borate).

[0062] A bulk acoustic wave resonator having the above-described layered structure generates resonance by inducing bulk acoustic waves in the piezoelectric layer 67 when electrical energy is applied between the lower electrode 66 and the upper electrode 68. The bulk acoustic waves generated by this bulk acoustic wave resonator propagate between the lower electrode 66 and the upper electrode 68 in a direction perpendicular to the film surface of the piezoelectric layer 67. In other words, a bulk acoustic wave resonator is a resonator that utilizes bulk acoustic waves.

[0063] 1 and 2 includes a support substrate 65. Each of the functional electrodes 25 and 26 includes, in order from the main surface 70a, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68.

[0064] [3. Surface Structure of Frame 30 and Signal Conductor 20] Next, the surface structures of the frame 30 and the signal conductor 20 will be described. Fig. 4A is a diagram showing an electron microscope image of the outer cross section and outer surface of the frame according to the embodiment. Fig. 4B is a diagram showing an electron microscope image of the inner cross section and inner surface of the frame according to the embodiment.

[0065] The frame 30 includes a conductor mainly composed of aluminum (Al) and isolates the internal space of the frame 30 from the external space. Therefore, by exposing the acoustic wave filter 1 to a high-temperature water vapor atmosphere in the manufacturing process of the acoustic wave filter 1, boehmite (AlO(OH):alumina monohydrate) can be produced on the external surface of the frame 30, which is the internal surface serving as the inner peripheral side wall and the external surface serving as the outer peripheral side wall of the frame 30. In other words, the external surface of the frame 30 contains boehmite. FIG. 4A shows that boehmite has been formed on the external surface of the frame 30. Boehmite has an orthorhombic needle-like crystal structure, and the length of the needle-like crystals in the short direction is approximately 10 nm. As a result, the external surface of the frame 30 has an uneven shape.

[0066] On the other hand, the inner surface of the frame 30 is not exposed to a high-temperature water vapor atmosphere during the manufacturing process of the acoustic wave filter 1. Therefore, as shown in FIG. 4B, boehmite is not formed on the inner surface, and the inner surface has a smaller unevenness difference than the outer surface.

[0067] Therefore, the outer surface of the frame body 30 is rougher than the inner surface of the frame body 30. This prevents heat generated in the functional electrodes 25 and 26 from being dissipated from the inner surface of the frame body 30 into the internal space of the frame body 30, and allows the heat to be efficiently dissipated from the outer surface of the frame body 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0068] The outer surface of the frame 30 may contain aluminum oxide or aluminum hydroxide instead of boehmite. The aluminum oxide and aluminum hydroxide formed on the outer surface of the frame 30 have an uneven structure, so that the outer surface of the frame 30 is rougher than the inner surface of the frame 30. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation.

[0069] Furthermore, the outer surface of the frame body 30 is rougher than the inner surface of the frame body 30; in other words, the surface area of ​​a given region on the outer surface of the frame body 30 is larger than the surface area of ​​the given region on the inner surface of the frame body 30.

[0070] This configuration provides a larger heat dissipation area on the outer surface of the frame body 30 than on the inner surface of the frame body 30, thereby preventing heat generated in the functional electrodes 25 and 26 from being dissipated from the inner surface of the frame body 30 into the internal space of the frame body 30, and allowing the heat to be efficiently dissipated from the outer surface of the frame body 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0071] FIG. 5 is a diagram illustrating a method for evaluating the surface area of ​​the frame 30 according to the embodiment. This figure shows schematic cross-sectional views of the outside and inside of the frame 30. The surface area of ​​a predetermined region on the outer surface of the frame 30 can be evaluated by the sum of the lengths of the ridges and valleys of the concave-convex shape of a line segment from the top to the bottom in the z-axis direction on the outer surface of the support layer 31 (concave-convex length L1). The surface area of ​​the predetermined region on the inner surface of the frame 30 can be evaluated by the sum of the lengths of the ridges and valleys of the concave-convex shape of a line segment from the top to the bottom in the z-axis direction on the inner surface of the support layer 31 (concave-convex length L2). In the acoustic wave filter 1 according to the present embodiment, the concave-convex length L1 is greater than the concave-convex length L2.

[0072] The predetermined region on the outer surface is defined as a region having a predetermined area when the outer surface of frame body 30 is viewed from above with the negative x-axis direction in Fig. 5 as the normal direction, and the predetermined region on the inner surface is defined as a region having the above-mentioned predetermined area when the inner surface of frame body 30 is viewed from above with the positive x-axis direction in Fig. 5 as the normal direction. The predetermined region may also be a region that includes the surface of support layer 31 but does not include the surfaces of bonding layers 32 and 33.

[0073] Furthermore, the outer surface of the frame body 30 is rougher than the inner surface of the frame body 30; in other words, the arithmetic mean roughness of a specified area on the outer surface of the frame body 30 is greater than the arithmetic mean roughness of the specified area on the inner surface of the frame body 30.

[0074] This configuration provides a larger heat dissipation area on the outer surface of the frame 30 than on the inner surface of the frame 30, allowing heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0075] The arithmetic mean roughness of the surface of the frame 30 can be measured using a laser microscope (for example, Olympus OLS5000). If the outer periphery of the frame 30 is in contact with a resin member, the resin member can be removed using fuming nitric acid or a heat gun, and then the arithmetic mean roughness can be measured using the laser microscope.

[0076] The arithmetic mean roughness of a predetermined region on the outer surface of the frame 30 is preferably 10 nm or more. This is because the length in the short direction of the needle-like crystals of boehmite formed on the outer peripheral surface of the frame 30 is about 10 nm. This promotes heat dissipation from the outer surface of the frame 30.

[0077] The acoustic wave filter according to the present invention only needs to satisfy at least one of the following conditions: (1) the surface area of ​​a predetermined region on the outer surface of the frame body 30 is larger than the surface area of ​​the predetermined region on the inner surface of the frame body 30, and (2) the arithmetic mean roughness of the outer surface of the frame body 30 is larger than the arithmetic mean roughness of the inner surface of the frame body 30. This makes it possible to provide an acoustic wave filter with improved heat dissipation.

[0078] In addition, in frame 30, the outer surface region that is rougher than the inner surface may be only the outer surface of support layer 31. Compared to bonding layers 32 and 33, support layer 31 always has a conductor portion mainly composed of Al (aluminum), so boehmite, aluminum oxide, or aluminum hydroxide is more likely to be produced on the outer surface, making it easier to form a roughened structure. In other words, it is sufficient that the outer surface of support layer 31 is rougher than the inner surface of support layer 31.

[0079] This allows heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the support layer 31 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0080] Furthermore, the outer surface of the frame 30 is rougher than the surface of the signal conductor 20. This prevents heat generated in the functional electrodes 25 and 26 from being dissipated from the surface of the signal conductor 20 into the internal space of the frame 30, while allowing the heat to be efficiently dissipated from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0081] In addition, the outer surface of the frame body 30 is rougher than the surface of the signal conductor 20; in other words, the surface area of ​​a given region on the outer surface of the frame body 30 is larger than the surface area of ​​the given region on the surface of the signal conductor 20.

[0082] This allows heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0083] Furthermore, the outer surface of the frame body 30 is rougher than the surface of the signal conductor 20; in other words, the arithmetic mean roughness of a specified area on the outer surface of the frame body 30 is greater than the arithmetic mean roughness of the specified area on the surface of the signal conductor 20.

[0084] This allows heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0085] [4 Effects etc.] As described above, the acoustic wave filter 1 according to this embodiment includes the substrate 10 having principal surfaces 10a and 10b facing each other, the substrate 70 having the principal surface 70a facing the principal surface 10a, the functional electrodes 25 and 26 arranged on the principal surface 70a, and the frame body 30 arranged between the principal surfaces 10a and 70a and surrounding the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan, and the outer surface of the frame body 30 is rougher than the inner surface of the frame body 30.

[0086] This configuration suppresses heat generated in the functional electrodes 25 and 26 from being dissipated into the internal space of the frame 30, while efficiently dissipating the heat from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0087] Furthermore, for example, in the acoustic wave filter 1, the frame 30 includes a conductor portion made of metal.

[0088] This makes it possible to improve the airtightness of the internal space of the frame body 30. Furthermore, by setting the frame body 30 to, for example, ground potential, it becomes possible to block external noise.

[0089] In addition, for example, in the acoustic wave filter 1, the conductor portion of the frame 30 is made of aluminum.

[0090] According to this, in the manufacturing process of the acoustic wave filter 1, by subjecting the acoustic wave filter 1 to a high-temperature water vapor atmosphere or other processing, aluminum oxide, aluminum hydroxide, and the like can be generated on the outer surface of the frame 30. As a result, a concave-convex structure can be formed on the outer surface of the frame 30.

[0091] In addition, for example, in the acoustic wave filter 1, the outer surface of the frame 30 includes aluminum oxide.

[0092] This allows the outer surface of the frame 30 to have an uneven structure.

[0093] In addition, for example, in the acoustic wave filter 1, the outer surface of the frame 30 contains boehmite.

[0094] This provides the outer surface of the frame 30 with an uneven structure derived from the needle-like crystal structure, making the outer surface rougher than the inner surface. This allows heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the frame 30 to the outside of the acoustic wave filter 1 while suppressing heat dissipation into the internal space of the frame 30. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0095] In addition, for example, in the acoustic wave filter 1, the outer surface of the frame 30 includes aluminum hydroxide.

[0096] This allows the outer surface of the frame 30 to have an uneven structure.

[0097] For example, in the acoustic wave filter 1, the frame body 30 includes a bonding layer 32 that contacts the substrate 10 and surrounds the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan, a bonding layer 33 that contacts the substrate 70 and surrounds the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan, and a support layer 31 that is disposed between the bonding layers 32 and 33 and surrounds the functional electrodes 25 and 26 when the principal surfaces 10a and 70a are viewed in plan, and the outer surface of the support layer 31 is rougher than the inner surface of the support layer 31.

[0098] This allows heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the support layer 31 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0099] Furthermore, for example, in the acoustic wave filter 1, the surface area of ​​a predetermined region on the outer surface of the frame 30 is larger than the surface area of ​​the predetermined region on the inner surface of the frame 30.

[0100] Furthermore, for example, in the acoustic wave filter 1, the arithmetic mean roughness of a predetermined region on the outer surface of the frame 30 is greater than the arithmetic mean roughness of the predetermined region on the inner surface of the frame 30.

[0101] As a result, the outer surface of the frame body 30 has a larger heat dissipation area than the inner surface of the frame body 30, and heat generated in the functional electrodes 25 and 26 can be efficiently dissipated from the outer surface of the frame body 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0102] For example, the acoustic wave filter 1 further includes a signal conductor 20 that is connected to the functional electrode 25 or 26, is positioned inside the frame body 30 when the main surfaces 10a and 70a are viewed in plan, and is in contact with the main surfaces 10a and 70a, and the outer surface of the frame body 30 is rougher than the surface of the signal conductor 20.

[0103] This configuration suppresses heat generated in the functional electrodes 25 and 26 from being dissipated from the surface of the signal conductor 20 into the internal space of the frame 30, while efficiently dissipating the heat from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0104] For example, in the acoustic wave filter 1, the surface area of ​​a predetermined region on the outer surface of the frame 30 is larger than the surface area of ​​the predetermined region on the surface of the signal conductor 20.

[0105] For example, in the acoustic wave filter 1, the arithmetic mean roughness of a predetermined region on the outer surface of the frame 30 is greater than the arithmetic mean roughness of the predetermined region on the surface of the signal conductor 20.

[0106] These features allow heat generated in the functional electrodes 25 and 26 to be efficiently dissipated from the outer surface of the frame 30 to the outside of the acoustic wave filter 1. This makes it possible to provide an acoustic wave filter 1 with improved heat dissipation properties.

[0107] For example, the acoustic wave filter 1 further includes a via conductor 11 that is disposed on the substrate 10 from the principal surface 10a to the principal surface 10b and is connected to the signal conductor 20.

[0108] This allows signals passing through the functional electrodes 25 and 26 to be transmitted through the via conductors 11 to the main surface 10b side.

[0109] Furthermore, for example, in the acoustic wave filter 1, the substrate 10 includes silicon.

[0110] This increases the thermal conductivity and improves the heat dissipation of the acoustic wave filter 1 compared to when the substrate 10 is made of a resin material.

[0111] Also, for example, in the acoustic wave filter 1, the substrate 70 has piezoelectricity, and an IDT electrode is arranged on the main surface 70a, and the IDT electrode has a plurality of electrode fingers 61a and 61b arranged parallel to each other, a busbar electrode 62a configured to connect one ends of the plurality of electrode fingers 61a, and a busbar electrode 62b configured to connect one ends of the electrode fingers 61b and arranged opposite the busbar electrode 62a across the plurality of electrode fingers 61a and the plurality of electrode fingers 61b, and the functional electrodes 25 and 26 include the plurality of electrode fingers 61a and the plurality of electrode fingers 61b.

[0112] This makes it possible to improve the heat dissipation performance of the acoustic wave filter 1 that performs electromechanical conversion using surface acoustic waves.

[0113] Furthermore, for example, in the acoustic wave filter 1, the functional electrodes 25 and 26 include a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68 in this order from the principal surface 70a.

[0114] This makes it possible to improve heat dissipation in the acoustic wave filter 1 that performs electromechanical transduction using bulk acoustic waves.

[0115] Furthermore, for example, in the acoustic wave filter 1, the substrate 70 includes silicon.

[0116] This allows the substrate 70 to be used as a support substrate for the bulk acoustic wave resonator.

[0117] (Other embodiments) Although the acoustic wave filter according to the present invention has been described above with reference to the preferred embodiments, the present invention is not limited to the preferred embodiments. The present invention also includes various modifications that can be made to the preferred embodiments by those skilled in the art without departing from the spirit and scope of the present invention, as well as various devices incorporating an acoustic wave filter according to the present invention.

[0118] The characteristics of the acoustic wave filter described based on the above embodiment will be described below.

[0119] <1> a first substrate having a first main surface and a second main surface facing each other; a second substrate having a third main surface facing the first main surface; a functional electrode disposed on the third principal surface; a frame body disposed between the first principal surface and the third principal surface, the frame body surrounding the functional electrodes when the first principal surface and the third principal surface are viewed in plan; The acoustic wave filter, wherein the outer surface of the frame is rougher than the inner surface of the frame.

[0120] <2> The frame includes a conductor portion made of metal. <1> The acoustic wave filter according to claim 1.

[0121] <3> The conductor portion is made of aluminum. <2> The acoustic wave filter according to claim 1.

[0122] <4> The outer surface of the frame comprises aluminum oxide. <3> The acoustic wave filter according to claim 1.

[0123] <5> The outer surface of the frame contains boehmite. <4> The acoustic wave filter according to claim 1.

[0124] <6> The outer surface of the frame contains aluminum hydroxide. <2> The acoustic wave filter according to claim 1.

[0125] <7> The frame body is a first bonding layer that is in contact with the first substrate and surrounds the functional electrode when the first principal surface and the third principal surface are viewed in plan; a second bonding layer that is in contact with the second substrate and surrounds the functional electrode when the first principal surface and the third principal surface are viewed in plan; a support layer disposed between the first bonding layer and the second bonding layer, and surrounding the functional electrode when the first principal surface and the third principal surface are viewed in plan; the outer surface of the support layer is rougher than the inner surface of the support layer; <1> ~ <6> 10. The acoustic wave filter according to claim 9, wherein

[0126] <8> a surface area of ​​a predetermined region on the outer surface of the frame body is larger than a surface area of ​​the predetermined region on the inner surface of the frame body; <1> ~ <7> 10. The acoustic wave filter according to claim 9, wherein

[0127] <9> the arithmetic mean roughness of a predetermined region on the outer surface of the frame is greater than the arithmetic mean roughness of the predetermined region on the inner surface of the frame; <1> ~ <7> 10. The acoustic wave filter according to claim 9, wherein

[0128] <10> moreover, a first conductor connected to the functional electrode, disposed inside the frame when the first principal surface and the third principal surface are viewed in plan, and in contact with the first principal surface and the third principal surface; the outer surface of the frame is rougher than the surface of the first conductor; <1> ~ <9> 10. The acoustic wave filter according to claim 9, wherein

[0129] <11> a surface area of ​​a predetermined region on the outer surface of the frame body is larger than a surface area of ​​the predetermined region on the surface of the first conductor; <10> The acoustic wave filter according to claim 1.

[0130] <12> the arithmetic mean roughness of a predetermined region on the outer surface of the frame is greater than the arithmetic mean roughness of the predetermined region on the surface of the first conductor; <10> The acoustic wave filter according to claim 1.

[0131] <13> moreover, a via conductor disposed on the first substrate from the first main surface toward the second main surface and connected to the first conductor; <10> ~ <12> 10. The acoustic wave filter according to claim 9, wherein

[0132] <14> the first substrate comprises silicon; <1> ~ <13> 10. The acoustic wave filter according to claim 9, wherein

[0133] <15> the second substrate has piezoelectric properties; an IDT electrode is disposed on the third principal surface; The IDT electrode is a plurality of first electrode fingers and a plurality of second electrode fingers arranged parallel to each other; a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers to each other; a second bus bar electrode configured to connect one ends of the second electrode fingers to each other and disposed opposite the first bus bar electrode with the first electrode fingers and the second electrode fingers interposed therebetween, the functional electrode includes the plurality of first electrode fingers and the plurality of second electrode fingers; <1> ~ <14> 10. The acoustic wave filter according to claim 9, wherein

[0134] <16> the functional electrode includes, in order from the third principal surface, a first planar electrode, a piezoelectric thin film, and a second planar electrode; <1> ~ <14> 10. The acoustic wave filter according to claim 9, wherein

[0135] <17> the second substrate comprises silicon; <16> The acoustic wave filter according to claim 1. [Industrial Applicability]

[0136] The present invention can be widely used as a small acoustic wave filter in communication devices such as mobile phones. [Explanation of symbols]

[0137] 1. Acoustic wave filters 10, 70 board 10a, 10b, 70a, 70b main surface 11 Via conductor 12 Planar electrode 13 Insulating film 20 Signal Conductor 21 Main body 22, 23, 32, 33 bonding layer 25, 26 Functional electrodes 27, 28 Busbar electrodes 30 Frame 31 Support layer 40 Bump electrode 50 Piezoelectric substrate 51 High-sonic support substrate 52 Low sound velocity membrane 53 Piezoelectric film 54 IDT electrode 55, 58 protective layer 57 Piezoelectric single crystal substrate 60 Elastic wave resonator 60a, 60b comb-shaped electrode 61a, 61b electrode fingers 62a, 62b Busbar electrodes 65 Support substrate 66 Lower electrode 67 Piezoelectric layer 68 Upper electrode 540 Adhesion layer 542 Main electrode layer

Claims

1. a first substrate having a first main surface and a second main surface facing each other; a second substrate having a third main surface facing the first main surface; a functional electrode disposed on the third principal surface; a frame body disposed between the first principal surface and the third principal surface, the frame body surrounding the functional electrodes when the first principal surface and the third principal surface are viewed in plan; the outer surface of the frame is rougher than the inner surface of the frame; Acoustic wave filters.

2. The frame includes a conductor portion made of metal. The acoustic wave filter according to claim 1 .

3. The conductor portion is made of aluminum. The acoustic wave filter according to claim 2 .

4. The outer surface of the frame comprises aluminum oxide. The acoustic wave filter according to claim 3 .

5. The outer surface of the frame contains boehmite. The acoustic wave filter according to claim 4 .

6. The outer surface of the frame contains aluminum hydroxide. The acoustic wave filter according to claim 2 .

7. The frame body is a first bonding layer in contact with the first substrate and surrounding the functional electrode when the first principal surface and the third principal surface are viewed in plan; a second bonding layer in contact with the second substrate and surrounding the functional electrode when the first principal surface and the third principal surface are viewed in plan; a support layer disposed between the first bonding layer and the second bonding layer, the support layer surrounding the functional electrode when the first principal surface and the third principal surface are viewed in plan; the outer surface of the support layer is rougher than the inner surface of the support layer; The acoustic wave filter according to any one of claims 1 to 6.

8. a surface area of ​​a predetermined region on the outer surface of the frame body is larger than a surface area of ​​the predetermined region on the inner surface of the frame body; The acoustic wave filter according to any one of claims 1 to 6.

9. the arithmetic mean roughness of a predetermined region on the outer surface of the frame is greater than the arithmetic mean roughness of the predetermined region on the inner surface of the frame; The acoustic wave filter according to any one of claims 1 to 6.

10. moreover, a first conductor connected to the functional electrode, disposed inside the frame when the first principal surface and the third principal surface are viewed in plan, and in contact with the first principal surface and the third principal surface; the outer surface of the frame is rougher than the surface of the first conductor; The acoustic wave filter according to any one of claims 1 to 6.

11. a surface area of ​​a predetermined region on the outer surface of the frame body is larger than a surface area of ​​the predetermined region on the surface of the first conductor; The acoustic wave filter according to claim 10 .

12. an arithmetic mean roughness of a predetermined region on the outer surface of the frame is greater than an arithmetic mean roughness of the predetermined region on the surface of the first conductor; The acoustic wave filter according to claim 10 .

13. moreover, a via conductor disposed on the first substrate from the first main surface toward the second main surface and connected to the first conductor; The acoustic wave filter according to claim 10 .

14. the first substrate comprises silicon; The acoustic wave filter according to any one of claims 1 to 6.

15. the second substrate has piezoelectric properties; an IDT electrode is disposed on the third main surface; The IDT electrode is a plurality of first electrode fingers and a plurality of second electrode fingers arranged parallel to each other; a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers to each other; a second bus bar electrode configured to connect one ends of the second electrode fingers to each other and disposed opposite the first bus bar electrode with the first electrode fingers and the second electrode fingers interposed therebetween, the functional electrode includes the plurality of first electrode fingers and the plurality of second electrode fingers; The acoustic wave filter according to any one of claims 1 to 6.

16. the functional electrode includes, in order from the third principal surface, a first planar electrode, a piezoelectric thin film, and a second planar electrode; The acoustic wave filter according to any one of claims 1 to 6.

17. the second substrate comprises silicon; The acoustic wave filter according to claim 16 .

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