WO2025192060A1 - Elastic wave filter - Google Patents

Abstract

An elastic wave filter (1) comprising: a substrate (10) having main surfaces (10a, 10b) opposite from each other; a substrate (70) having a main surface (70a) facing the main surface (10a); a functional electrode (26) disposed on the main surface (70a); a frame body (30) that is positioned between the main surface (10a) and the main surface (70a) and surrounds the functional electrode (26) when the main surfaces (10a, 70a) are seen in plan view; signal wiring (22) that is connected to the functional electrode (26) and is in contact with the main surfaces (10a, 70a); and an insulation member (42) that is positioned between the frame body (30) and the signal wiring (22) and is in contact with the frame body (30) and the signal wiring (22). At least a portion of the signal wiring (22) is positioned further toward the outer side than the inner-side surface of the frame body (30) contacting the internal space of the frame body (30) and is positioned further inward than the outer-side surface of the frame body (30) in plan view.

Description

Acoustic Wave Filter

The present invention relates to an acoustic wave filter.

Patent Document 1 (Figure 16) discloses an electronic device comprising a piezoelectric thin-film resonator, a first substrate (piezoelectric substrate) on which the piezoelectric thin-film resonator is arranged, a second substrate (lid substrate) arranged so as to sandwich the piezoelectric thin-film resonator between the first substrate and the second substrate, and side walls and pillars arranged to ensure space between the first and second substrates. It is claimed that this makes it possible to construct a low-loss acoustic wave resonator.

Japanese Patent Application Laid-Open No. 2018-137742

With the demand for higher output power in mobile communications, there is a demand for acoustic wave filters with improved heat dissipation.

Therefore, an object of the present invention is to provide an acoustic wave filter with improved heat dissipation properties.

In order to achieve the above object, an acoustic wave filter according to one aspect of the present invention comprises a first substrate having first and second principal surfaces opposing each other, a second substrate having a third principal surface facing the first principal surface, a functional electrode disposed on the third principal surface, a frame disposed between the first and third principal surfaces and surrounding the functional electrode when the first and third principal surfaces are viewed in plan, signal wiring connected to the functional electrode and in contact with the first and third principal surfaces, and an insulating member disposed between the frame and the signal wiring and in contact with the frame and the signal wiring, wherein at least a portion of the signal wiring is located outside the inner surface of the frame that is in contact with the internal space of the frame in the above plan view, and inside the outer surface of the frame.

The present invention makes it possible to provide an acoustic wave filter with improved heat dissipation.

FIG. 1 is a cross-sectional view of an acoustic wave filter according to an embodiment of the present invention. FIG. 2 is a plan view of an acoustic wave filter according to an embodiment of the present invention. FIG. 3A is 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. FIG. 3B 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. FIG. 3C 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. FIG. 3D is a cross-sectional view schematically illustrating a fourth example of an acoustic wave resonator included in an acoustic wave filter according to an embodiment. FIG. 4A is a first cross-sectional view of a frame, an insulating member, and signal wiring according to a modified example of the embodiment. FIG. 4B is a second cross-sectional view of the frame, the insulating member, and the signal wiring according to the modified example of the embodiment.

The following describes in detail embodiments of the present disclosure 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 configurations shown in the following embodiments are merely examples and are not intended to limit the present invention. Of the components in the following embodiments, components that are not recited in independent claims are described as optional components. Furthermore, the sizes or size ratios of the components shown in the drawings are not necessarily precise.

Note that each figure is a schematic diagram in which emphasis, omissions, or adjustments to proportions have been made as appropriate to illustrate the present invention, and is not necessarily an exact illustration, and may differ from the actual shape, positional relationship, and proportions. In each figure, the same reference numerals are used to designate substantially identical components, and redundant explanations may be omitted or simplified.

In the circuit configurations disclosed herein, "connected" refers not only to direct connection by electrodes and/or wiring conductors, but also to 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.

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 express their strict meanings, but also include substantially equivalent ranges, for example, including an error of a few percent.

(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.

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, signal wiring 21 and 22, insulating members 41 and 42, via conductors 11, an insulating film 13, a planar electrode 12, and a bump electrode 40.

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, substrate 10 contains silicon. When substrate 10 contains silicon, its thermal conductivity is higher than when substrate 10 is made of a resin material. This improves the heat dissipation of acoustic wave filter 1. It also improves the processing accuracy of substrate 10.

Substrate 70 is an example of a second substrate, and has opposing principal surfaces 70a (third principal surface) and 70b. Principal surface 10a faces principal surface 70a. In this embodiment, substrate 70 has piezoelectric properties. Note that substrates 10 and 70 do not have to have a rectangular shape as shown in Figure 2, and may have a polygonal or circular shape.

Functional electrodes 25 and 26 are disposed on the main surface 70a, and in this embodiment, are IDT electrodes that perform electromechanical transduction with the substrate 70. Examples of the structure of functional electrodes 25 and 26 are described in Figures 3A to 3D.

The frame body 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 body 30 is a wall body disposed on the outer periphery of the substrates 10 and 70, which have a rectangular shape in plan view.

The frame body 30 may be composed of multiple metal layers. The frame body 30 includes a conductive portion whose main component is, for example, at least one of Al (aluminum), Cu (copper), Au (gold), Pt (platinum), and Ti (titanium). In other words, the frame body 30 includes a conductor portion made of metal.

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 space outside the frame body 30. Furthermore, since the frame body 30 includes a conductor portion made of metal, it is possible to ensure airtightness of the internal space. The frame body 30 may be connected to ground, which makes it 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, if it is not necessary to ensure airtightness of the internal space, the frame body 30 does not need to surround the entire periphery of the functional electrodes 25 and 26. For example, side walls may be formed around only three of the four outer peripheries of the rectangular substrates 10 and 70. Furthermore, the outer and inner peripheries of the frame body 30 do not have to have a rectangular shape in the plan view, but may have a polygonal or circular shape.

In addition, portions of the functional electrodes 25 and 26 may be electrically connected to the frame body 30 via wiring formed on the main surface 70a and set to ground potential.

Furthermore, a resin member may be disposed on the outer periphery of the frame body 30 so as to contact the outer 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.

The signal wiring 21 is connected to the functional electrode 25 via a connection wiring 27 and is in contact with the principal surfaces 10a and 70a. The signal wiring 21 transmits high-frequency signals (including elastic wave signals) that propagate through the functional electrode 25. The signal wiring 22 is connected to the functional electrode 26 via a connection wiring 28 and is in contact with the principal surfaces 10a and 70a. The signal wiring 22 transmits high-frequency signals (including elastic wave signals) that propagate through the functional electrode 26. Each of the signal wirings 21 and 22 includes a conductive portion whose main component is, for example, at least one of Al (aluminum), Cu (copper), Au (gold), Pt (platinum), and Ti (titanium). In other words, each of the signal wirings 21 and 22 includes a conductor portion made of metal. Note that each of the signal wirings 21 and 22 may be composed of multiple metal layers. In this embodiment, each of the signal wirings 21 and 22 is a columnar conductor, but the shape of the signal wirings 21 and 22 is not limited to a columnar shape.

Insulating member 41 is disposed between frame body 30 and signal wiring 21 and is in contact with frame body 30 and signal wiring 21. Insulating member 42 is disposed between frame body 30 and signal wiring 22 and is in contact with frame body 30 and signal wiring 22. The insulating material constituting insulating members 41 and 42 includes, for example, at least one of polyimide, epoxy resin, phenolic resin, silicone resin, acrylic resin, and ABS resin.

Via conductor 11 is an electrode arranged on substrate 10 from principal surface 10a toward principal surface 10b, and connected to signal wiring 21 or 22. In this embodiment, via conductor 11 is a through electrode filled in a cavity that penetrates substrate 10 between principal surface 10a and principal surface 10b. Via conductor 11 is made of, for example, a metal member whose main component is Cu (copper).

Note that the via conductor 11 does not have to be a single via conductor extending from the main surface 10a to the main surface 10b, but may instead have a configuration in which multiple via conductors are connected via a planar electrode formed within the substrate 10.

The insulating film 13 is disposed on the main surface 10b and is, for example, a silicon oxide film. Note that the insulating film 13 may not be present. Alternatively, an insulating film may be disposed on the main surface 70a.

The planar electrode 12 is disposed on the principal surface 10b and is bonded to the via conductor 11. The bump electrode 40 is bonded to the planar electrode 12 and is made of, for example, solder or a metal material primarily 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.

The above configuration makes it possible to provide a compact acoustic wave filter 1 in which functional electrodes 25 and 26 are arranged in the space surrounded by the substrates 10, 70 and frame 30.

[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 to this example.

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

As shown in (a) of Figure 3A, a pair of opposing comb electrodes 60a and 60b are formed on the piezoelectric substrate 50. The comb 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 electrode fingers 61a. The comb 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 electrode fingers 61b. The electrode fingers 61a and 61b are formed in a direction perpendicular to the acoustic wave propagation direction (X-axis direction). The busbar electrodes 62a and 62b are arranged opposite each other with the electrode fingers 61a and 61b in between. The comb electrodes 60a and 60b form an IDT (InterDigital Transducer) electrode 54.

Here, when acoustic wave filter 1 according to this embodiment performs electromechanical transduction using IDT electrode 54, substrate 70 shown in FIGS. 1 and 2 corresponds to piezoelectric substrate 50. Furthermore, functional electrodes 25 and 26 shown in FIGS. 1 and 2 each include multiple electrode fingers 61a and multiple electrode fingers 61b. Furthermore, the busbar electrode shown in FIG. 2 is either busbar electrode 62a or 62b.

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

As shown in (b) of Figure 3A, the IDT electrode 54 has, for example, a laminated structure of an adhesion layer 540 and a main electrode layer 542.

The adhesion layer 540 is a layer that improves adhesion between the piezoelectric substrate 50 and the main electrode layer 542, and is made of a material such as Ti. The main electrode layer 542 is made of a material such as 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 that protects the main electrode layer 542 from the external environment, adjusts the frequency-temperature characteristics, and improves moisture resistance, and is, for example, a dielectric film whose main component is silicon dioxide.

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

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

As shown in (c) of Figure 3A, the piezoelectric substrate 50 includes a support substrate 51, an intermediate layer 52, and a piezoelectric film 53, and has a structure in which the support substrate 51, the intermediate layer 52, and the piezoelectric film 53 are stacked in this order.

The piezoelectric film 53 is made of, for example, a θ° Y-cut X-propagation _LiTaO3 piezoelectric single crystal or piezoelectric ceramic (a lithium tantalate single crystal or ceramic 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 for the piezoelectric film 53 are appropriately selected depending on the required specifications of each filter.

The support substrate 51 is a substrate that supports the intermediate layer 52, the piezoelectric film 53, and the IDT electrode 54. The support substrate 51 may further be a substrate in which the sound velocity of bulk waves within the support substrate 51 is faster than that of acoustic waves such as surface waves and boundary waves that propagate through the piezoelectric film 53. The support substrate 51 functions to confine the surface acoustic waves within the portion where the piezoelectric film 53 and the intermediate layer 52 are stacked, preventing the surface acoustic waves from leaking below the support substrate 51. Examples of materials that can be used for the 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, DLC (diamond-like carbon), 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 .}

The intermediate layer 52 is, for example, a film in which the sound velocity of the bulk waves in the intermediate layer 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 support substrate 51. This structure, combined with the property of the elastic wave that energy is concentrated in a medium with an essentially low sound velocity, prevents the leakage of surface acoustic wave energy outside the IDT electrode. The intermediate layer 52 can be made of a dielectric material such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material containing any of the above materials as its main component.

Furthermore, the above-described layered structure of the piezoelectric substrate 50 makes it possible to significantly increase the Q value at the resonant frequency and anti-resonant frequency compared to conventional structures that use a single layer of piezoelectric substrate. In other words, it is possible to construct an acoustic wave resonator with a high Q value, and therefore to use this acoustic wave resonator to construct a filter with low insertion loss.

The support substrate 51 may have a laminated structure of a first support substrate and a high acoustic velocity film that propagates bulk waves at a higher acoustic velocity than elastic waves such as surface waves and boundary waves that propagate through the piezoelectric film 53. In this case, the high acoustic velocity film may be made of the same material as the support substrate 51. The first 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; dielectrics such as diamond and glass; semiconductors such as silicon and gallium nitride; resins; or materials containing any of the above as a main component.

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 any of the following states: single crystal, polycrystalline, or amorphous, or a mixture of these.

The wavelength λ of the acoustic wave resonator 60 is determined by the repetition period of the electrode fingers 61 a or 61 b constituting the IDT electrode 54 shown in FIG. 3A (b). The electrode finger pitch p is half the wavelength λ and is defined as (W + S), where W is the line width of the electrode fingers 61 a and 61 b constituting the interdigital transducers 60 a and 60 b, respectively, and S is the space width between adjacent electrode fingers 61 a and 61 b. The electrode finger duty D of the IDT electrode 60 is the line width occupancy rate of the electrode fingers 61 a and 61 b, which is the ratio of the line width to the sum of the line width W and the space width S, and is defined as W/(W + S). If the spacing between adjacent electrode fingers in the IDT electrode 54 is not uniform, the electrode finger pitch p of the IDT electrode 54 is defined as the average electrode finger pitch p _AVE of the IDT electrode 54. The average electrode finger pitch p _AVE of the IDT electrode 54 is defined as Di/(Ni-1), where Ni is the total number of electrode fingers 61 a, 61 b included in the IDT electrode 54, and Di is the center-to-center distance between the electrode finger located at one end and the electrode finger located at the other end in the acoustic wave propagation direction of the IDT electrode 54. Furthermore, if the electrode finger duty D of the IDT electrode 54 is not constant, the electrode finger duty D of the IDT electrode 54 is defined as the average electrode finger duty D _AVE of the IDT electrode 54. The average electrode finger duty D _AVE of the IDT electrode 54 is defined as W ALL /(W ALL +S ALL ), where Ni is the total number of electrode fingers 61 a, 61 b included in the IDT electrode 54, W _ALL is the total line width obtained by adding the line widths W of the (Ni-1) electrode fingers, and S _ALL is the total space width obtained by adding the space _widths S of the ( _Ni - ₁ ) electrode fingers included in the IDT electrode 54.

The electrode finger pitch p of the comb-shaped electrodes of the IDT electrode 54 can be measured by using a scanning electron microscope (SEM), scanning transmission electron microscope (STEM), or transmission electron microscope (TEM) to view the main surface of the substrate on which the comb-shaped electrodes of the IDT electrode 54 are formed in a plan view and/or a cross-section perpendicular to the extension direction of the electrode fingers, and measuring the line width L and space width S.

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

The piezoelectric single crystal substrate 57 is made of, for example, a piezoelectric single crystal of LiNbO _3. The elastic wave resonator according to this example is made up of the piezoelectric single crystal substrate 57 of LiNbO ₃ , an IDT electrode 54, and a protective layer 58 formed on the piezoelectric single crystal substrate 57 and the IDT electrode 54.

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 _LiTaO3 piezoelectric substrate having a cut angle other than the above-mentioned cut angles can achieve the same effects as the acoustic wave resonator 60 using the piezoelectric film 53.

Alternatively, 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 stacked in this order. The IDT electrode 54 is formed on the piezoelectric film. The piezoelectric film may be made of, for example, _LiTaO3 piezoelectric single crystal or piezoelectric ceramics. The support substrate supports the piezoelectric film, the energy trapping layer, and the IDT electrode 54.

The energy trapping layer consists of one or more layers, and the speed of bulk acoustic waves propagating through at least one of the layers is greater than the speed of 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 bulk waves in the low acoustic velocity layer is slower than the acoustic velocity of acoustic waves propagating through the piezoelectric film. The high acoustic velocity layer is a film in which the acoustic velocity of bulk waves in the high acoustic velocity layer is faster than the acoustic velocity of acoustic waves propagating through the piezoelectric film. The support substrate may also be the high acoustic velocity layer.

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.

FIG. 3C is a cross-sectional view schematically illustrating a third example of an acoustic wave resonator 60 constituting the acoustic wave filter 1 according to the embodiment. FIG. 3C illustrates a bulk acoustic wave resonator as the acoustic wave resonator of the acoustic wave filter 1. As shown in the figure, the bulk acoustic wave resonator has, for example, a support substrate 65, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68, with the support substrate 65, lower electrode 66, piezoelectric layer 67, and upper electrode 68 stacked in this order.

The support substrate 65 is a substrate for supporting the lower electrode 66, piezoelectric layer 67, and upper electrode 68, and is, for example, a silicon substrate. The support substrate 65 has a cavity in the area that comes into contact with the lower electrode 66. This allows the piezoelectric layer 67 to vibrate freely.

The lower electrode 66 is an example of a first planar electrode and is formed on one side of the support substrate 65. The upper electrode 68 is an example of a second planar electrode and is formed on one side 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.

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 primarily composed of at least one of the following materials: ZnO (zinc oxide), AlN (aluminum nitride), PZT (lead zirconate titanate), KN (potassium niobate), LN (lithium niobate), LT (lithium tantalate), quartz, and LiBO (lithium borate).

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.

When the acoustic wave filter 1 according to this embodiment performs electromechanical transduction using bulk acoustic waves, the substrate 70 shown in FIGS. 1 and 2 includes a support substrate 65. Each of the functional electrodes 25 and 26 shown in FIGS. 1 and 2 includes, in order from the main surface 70a, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68.

FIG. 3D is a cross-sectional view schematically illustrating a fourth example of an acoustic wave resonator 60 constituting an acoustic wave filter 1 according to an embodiment. In this example, the piezoelectric substrate 50 includes a support substrate 51, an intermediate layer 52, a gap 160, and a piezoelectric film 53.

In the acoustic wave filter 1 of this example, when the main surface 70a is viewed in plan, a gap 160 is provided between the piezoelectric film 53 and the support substrate 51 in the region overlapping with the IDT electrode 54. Furthermore, if the thickness (in the z-axis direction) of the piezoelectric film 53 is d and the electrode finger pitch of the IDT electrode 54 is p, the normalized film thickness d/p of the piezoelectric film 53 is 0.5 or less.

By having the normalized thickness d/p of the piezoelectric film 53 be 0.5 or less and by providing the air gap 160, the elastic wave resonator 60 constitutes a laterally excited film bulk acoustic resonator (XBAR). By having the normalized thickness d/p of the piezoelectric film 53 be 0.5 or less, the relative bandwidth of the elastic wave resonator 60 can be increased, and a resonator with a high electromechanical coupling coefficient can be constructed.

It is more desirable to set the normalized thickness d/p of the piezoelectric film 53 to 0.24 or less. This allows the relative bandwidth of the acoustic wave resonator 60 to be 7% or more.

It is desirable that the electrode finger duty D and normalized film thickness d/p of the IDT electrode 54 satisfy the relationship in Equation 1.

D≦1.75(d/p)+0.075 (Formula 1)

This effectively reduces the spurious emissions of higher-order modes of the XBAR. Specifically, the fractional bandwidth of the XBAR (the value obtained by dividing the difference frequency between the anti-resonance frequency and the resonant frequency by the average frequency of the anti-resonance frequency and the resonant frequency) can be reduced to 17% or less, preventing the spurious emissions of higher-order modes from being included in the passband.

Furthermore, it is more desirable that the electrode finger duty D and normalized film thickness d/p of the IDT electrode 54 satisfy the relationship in Equation 2.

D≦1.75(d/p)+0.05 (Formula 2)

This ensures that the XBAR's fractional bandwidth is 17% or less, preventing higher-order mode spurious emissions from being included in the passband.

Furthermore, it is desirable that the piezoelectric film 53 is made of lithium niobate or lithium tantalate, and that the Euler angles (θ1, θ2, θ3) of the lithium niobate or lithium tantalate that constitutes the piezoelectric film 53 are within the range of the following formula 3, formula 4, formula 5, or formula 6.

-10°≦θ1≦10° and 0°≦θ2≦20° (Equation 3)

−10°≦θ1≦10°, and 20°≦θ2≦80°, and 0°≦θ3≦60° (1−(θ2−50) ² /900) ^1/2 ) (Equation 4)

−10°≦θ1≦10°, and 20°≦θ2≦80°, and [180°−60°(1−(θ2−50) ² /900) ^1/2 )]≦θ3≦180° (Equation 5)

−10°≦θ1≦10°, and [180°−30°(1−(θ3−90) ² /8100) ^1/2 )]≦θ2≦180° (Equation 6)

By defining the Euler angles of the piezoelectric film 53 made of lithium niobate or lithium tantalate as described above, the relative bandwidth of the acoustic wave resonator 60 can be made 5% or more.

In the fourth example of acoustic wave device 1, an energy trapping layer including a low acoustic impedance layer and a high acoustic impedance layer may be disposed instead of gap 160. Specifically, an energy trapping layer having a configuration in which low acoustic impedance layers with relatively low acoustic impedance and high acoustic impedance layers with relatively high acoustic impedance are alternately stacked may be disposed between piezoelectric film 53 and support substrate 51. The energy trapping layer may have a laminated structure of a low acoustic velocity film and a high acoustic velocity film. The low acoustic velocity film is a film in which the acoustic velocity of bulk waves in the low acoustic velocity film is slower than the acoustic velocity of bulk acoustic waves propagating through piezoelectric film 53. The high acoustic velocity film is a film in which the acoustic velocity of bulk waves in the high acoustic velocity film is faster than the acoustic velocity of acoustic waves propagating through piezoelectric film 53. When piezoelectric film 53 has a normalized thickness d/p of 0.5 or less and an energy trapping layer is provided, acoustic wave resonator 60 constitutes an XBAR.

[3. Arrangement of Frame 30 and Signal Wirings 21 and 22]
Next, the layout of the frame 30 and the signal wirings 21 and 22 will be described with reference to FIGS.

As shown in Figures 1 and 2, the signal wiring 21 is connected to the functional electrode 25 via connection wiring 27 formed on the main surface 70a. The signal wiring 21 is a columnar conductor extending from the main surface 70a toward the main surface 10a. The signal wiring 21 is insulated from the frame body 30 by an insulating member 41. The connection wiring 27 includes a bus bar electrode connected to the functional electrode 25 and a connection wiring that connects the bus bar electrode and the signal wiring 21.

Here, as shown in FIG. 2, when the main surfaces 10a and 70a are viewed in plan, the signal wiring 21 is located outside the inner surface that contacts the internal space of the frame body 30, and inside the outer surface of the frame body 30. Note that the inner surface that contacts the internal space of the frame body 30 is the inner wall surface of the frame body 30 that contacts the internal space separated by the frame body 30 and in which the functional electrodes 25 and 26 are arranged, and the outer surface of the frame body 30 is the outer wall surface of the frame body 30. In other words, the inner surface that contacts the internal space of the frame body 30 is the inner wall surface exposed to the internal space separated by the frame body 30.

As a result, compared to the conventional configuration in which the signal wiring 21 is positioned inside the inner surface of the frame body 30 and the entire surface of the signal wiring 21 is in contact with the air in the internal space, the signal wiring 21 in this embodiment is integrated with the frame body 30 via the insulating member 41. As a result, heat generated in the signal wiring 21 can be efficiently dissipated from the frame body 30 to the external space via the insulating member 41. This improves the heat dissipation and reliability of the acoustic wave filter 1.

Furthermore, as shown in FIG. 2, the insulating member 41 surrounds the signal wiring 21 in the plan view. As a result, the entire surface of the signal wiring 21 is in contact with the insulating member 41, so heat generated in the signal wiring 21 can be efficiently dissipated to the insulating member 41.

Furthermore, as shown in FIG. 2, the frame body 30 surrounds the insulating member 41 and the signal wiring 21 in the plan view. As a result, the entire surface of the signal wiring 21 is in contact with the insulating member 41, and further, the entire outer surface of the insulating member 41 is in contact with the frame body 30, so heat generated in the signal wiring 21 can be efficiently dissipated to the frame body 30.

As shown in Figures 1 and 2, the signal wiring 22 is connected to the functional electrode 26 via connection wiring 28 formed on the main surface 70a. The signal wiring 22 is a columnar conductor extending from the main surface 70a toward the main surface 10a. The signal wiring 22 is insulated from the frame body 30 by an insulating member 42. The connection wiring 28 includes a bus bar electrode connected to the functional electrode 26 and a connection wiring that connects the bus bar electrode and the signal wiring 22.

Here, as shown in FIG. 2, at least a portion of the signal wiring 22 is located outside the inner surface of the frame body 30 and inside the outer surface of the frame body 30 in the plan view.

As a result, compared to the conventional configuration in which the signal wiring 22 is positioned inside the inner surface of the frame body 30 and the entire surface of the signal wiring 22 is in contact with the air in the internal space, the signal wiring 22 in this embodiment is integrated with the frame body 30 via the insulating member 42. As a result, heat generated in the signal wiring 22 can be efficiently dissipated from the frame body 30 to the external space via the insulating member 42. This improves the heat dissipation and reliability of the acoustic wave filter 1.

Note that the acoustic wave filter 1 according to this embodiment is only required to include at least one of the signal lines 21 and 22, and may also include signal lines 23 and 24 in addition to the signal lines 21 and 22. The signal line 23 is connected to the functional electrode 25 and is a columnar conductor in contact with the principal surface 70a and the principal surface 10a. It is located inside the inner surface of the frame body 30, and the entire surface of the signal line 23 is in contact with the air in the internal space. The signal line 24 is connected to the functional electrode 26 and is a columnar conductor in contact with the principal surface 70a and the principal surface 10a. It is located inside the inner surface of the frame body 30, and the entire surface of the signal line 24 is in contact with the air in the internal space.

[4. Arrangement of insulating members according to modified examples]
Next, the configurations of the insulating members 41A and 42A according to the modified examples will be described.

FIG. 4A is a cross-sectional view of a frame body 30, an insulating member 41A, and a signal wiring 21 according to a modified embodiment. FIG. 4B is a cross-sectional view of a frame body 30, an insulating member 42A, and a signal wiring 22 according to a modified embodiment. The cross-sectional view of this modified embodiment shown in FIG. 4A corresponds to the cross-sectional view of range IVA of the embodiment shown in FIG. 1. Furthermore, the cross-sectional view of this modified embodiment shown in FIG. 4B corresponds to the cross-sectional view of range IVB of the embodiment shown in FIG. 1.

The acoustic wave filter according to this modification includes substrates 10 and 70, a frame 30, functional electrodes 25 and 26, signal wiring 21 and 22, insulating members 41A and 42A, via conductors 11, an insulating film 13, a planar electrode 12, and a bump electrode 40. The acoustic wave filter according to this modification differs from the acoustic wave filter 1 according to the embodiment only in the configuration of the insulating members 41A and 42A. Therefore, the following description of the acoustic wave filter according to this modification will focus on the configuration of the insulating members 41A and 42A that differs from the acoustic wave filter 1 according to the embodiment.

As shown in FIG. 4A, insulating member 41A is disposed between frame body 30 and signal wiring 21 and is in contact with frame body 30 and signal wiring 21. Also, as shown in FIG. 4B, insulating member 42A is disposed between frame body 30 and signal wiring 22 and is in contact with frame body 30 and signal wiring 22. Insulating member 41A includes an insulating material and filler 45. Also, insulating member 42A includes an insulating material and filler 45.

The insulating material constituting insulating members 41A and 42A includes, for example, at least one of polyimide, epoxy resin, phenolic resin, silicone resin, acrylic resin, and ABS resin.

The filler 45 forming the insulating members 41A and 42A includes, for example, at least one of boron nitride (BN), alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon carbide (SiC), graphite, Graphine (registered trademark), and diamond powder.

The thermal conductivity of the filler 45 contained in the insulating member 41A is higher than the thermal conductivity of the insulating material contained in the insulating member 41A. Furthermore, the thermal conductivity of the filler 45 contained in the insulating member 42A is higher than the thermal conductivity of the insulating material contained in the insulating member 42A.

As a result, the thermal conductivity of the insulating member 41A is improved, allowing heat generated in the signal wiring 21 to be dissipated highly efficiently from the frame body 30 to the external space via the insulating member 41A. Furthermore, the thermal conductivity of the insulating member 42A is improved, allowing heat generated in the signal wiring 22 to be dissipated highly efficiently from the frame body 30 to the external space via the insulating member 42A. This improves the heat dissipation and reliability of the acoustic wave filter.

[5. Effects, etc.]
As described above, the acoustic wave filter 1 according to this embodiment includes the substrate 10 having principal surfaces 10 a and 10 b facing each other, the substrate 70 having the principal surface 70 a facing the principal surface 10 a, the functional electrode 26 (or 25) disposed on the principal surface 70 a, the frame body 30 disposed between the principal surfaces 10 a and 70 a and surrounding the functional electrode 26 (or 25) when the principal surfaces 10 a and 70 a are viewed in plan, the signal wiring 22 (or 21) connected to the functional electrode 26 (or 25) and in contact with the principal surfaces 10 a and 70 a, and the insulating member 42 (or 41) disposed between the frame body 30 and the signal wiring 22 (or 21) and in contact with the frame body 30 and the signal wiring 22 (or 21), wherein at least a portion of the signal wiring 22 (or 21) is located outside the inner surface of the frame body 30 that is in contact with the internal space of the frame body 30 and is located inside the outer surface of the frame body 30 in the above plan view.

In this configuration, the signal wiring 22 (or 21) is positioned inside the inner surface of the frame body 30, and compared to a conventional configuration in which the entire surface of the signal wiring 22 (or 21) is in contact with the air in the internal space, the signal wiring 22 (or 21) is integrated with the frame body 30 via the insulating member 42 (or 41). This allows heat generated in the signal wiring 22 (or 21) to be efficiently dissipated from the frame body 30 to the external space via the insulating member 42 (or 41). This improves the heat dissipation and reliability of the acoustic wave filter 1.

Furthermore, for example, in the acoustic wave filter 1, the insulating member 41 surrounds the signal wiring 21 in the above-mentioned plan view.

As a result, the entire surface of the signal wiring 21 is in contact with the insulating member 41, so heat generated in the signal wiring 21 can be efficiently dissipated to the insulating member 41.

Furthermore, for example, in the acoustic wave filter 1, the frame body 30 surrounds the insulating member 41 and the signal wiring 21 in the above-mentioned plan view.

As a result, the entire surface of the signal wiring 21 is in contact with the insulating member 41, and further, the entire outer surface of the insulating member 41 is in contact with the frame body 30, so heat generated in the signal wiring 21 can be efficiently dissipated to the frame body 30.

Furthermore, for example, in the acoustic wave filter 1, the signal wiring 21 (or 22) transmits a high-frequency signal (including an acoustic wave signal) that propagates through the functional electrode 25 (or 26).

As a result, the signal wiring 21 (or 22) that transmits high-frequency signals can be insulated from the frame body 30 by the insulating member 41 (or 42), thereby reducing transmission loss of high-frequency signals.

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

This makes it possible to increase the airtightness of the internal space of the frame body 30.

Also, for example, in the acoustic wave filter 1, the frame body 30 is connected to ground.

This allows the frame 30 to block out external noise.

Furthermore, for example, in an acoustic wave filter according to a modified example, the insulating member 41A (or 42A) includes an insulating material and a filler, and the thermal conductivity of the filler is higher than the thermal conductivity of the insulating material.

This improves the thermal conductivity of the insulating member 41A (or 42A), allowing heat generated in the signal wiring 21 (or 22) to be dissipated efficiently from the frame body 30 to the external space via the insulating member 41A (or 42A).

Furthermore, for example, the acoustic wave filter 1 further includes a via conductor 11 arranged on the substrate 10 from the principal surface 10a to the principal surface 10b and connected to the signal wiring 21 (or 22).

This allows high-frequency signals passing through the functional electrode 25 (or 26) to be transmitted to the main surface 10b side via the via conductor 11.

Also, for example, in the acoustic wave filter 1, the substrate 10 contains silicon.

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. In addition, the processing precision of the substrate 10 is improved.

Furthermore, for example, in the acoustic wave filter 1, the substrate 70 has piezoelectric properties, an IDT electrode is arranged on the main surface 70a, 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 with the plurality of electrode fingers 61a and 61b between them, and the functional electrode 25 (or 26) includes a plurality of electrode fingers 61a and a plurality of electrode fingers 61b.

This makes it possible to improve heat dissipation in the acoustic wave filter 1, which uses surface acoustic waves to perform electromechanical conversion.

Furthermore, for example, in the acoustic wave filter 1, the functional electrode 25 (or 26) includes, in order from the main surface 70a, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68.

This makes it possible to improve heat dissipation in the acoustic wave filter 1, which uses bulk acoustic waves to perform electromechanical conversion.

Also, for example, in the acoustic wave filter 1, the substrate 70 includes silicon.

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

(Other embodiments)
Although the acoustic wave filter according to the present invention has been described above with reference to the embodiments and modifications thereof, the present invention is not limited to the above embodiments and modifications. The present invention also includes modifications that can be made 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.

The following describes the features of the acoustic wave filters described based on the above embodiments and modifications.

<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 disposed between the first principal surface and the third principal surface, the frame surrounding the functional electrodes when the first principal surface and the third principal surface are viewed in plan;
signal wiring connected to the functional electrodes and in contact with the first principal surface and the third principal surface;
an insulating member disposed between the frame body and the signal wiring and in contact with the frame body and the signal wiring;
an elastic wave filter in which at least a portion of the signal wiring is located outside an inner surface of the frame body that contacts the internal space of the frame body in the plan view, and is located inside an outer surface of the frame body.

<2>
The acoustic wave filter according to <1>, wherein the insulating member surrounds the signal wiring in the plan view.

<3>
The acoustic wave filter according to <2>, wherein the frame surrounds the insulating member and the signal wiring in the plan view.

＜4＞
The acoustic wave filter according to any one of <1> to <3>, wherein the signal wiring transmits a high-frequency signal that propagates through the functional electrode.

<5>
The acoustic wave filter according to any one of <1> to <4>, wherein the frame includes a conductor portion made of metal.

<6>
The acoustic wave filter according to <5>, wherein the frame is connected to a ground.

＜７＞
the insulating member includes an insulating material and a filler;
The acoustic wave filter according to any one of <1> to <6>, wherein the filler has a thermal conductivity higher than that of the insulating material.

＜8＞
moreover,
The acoustic wave filter according to any one of <1> to <7>, further comprising a via conductor disposed on the first substrate from the first main surface toward the second main surface and connected to the signal wiring.

＜９＞
The acoustic wave filter according to any one of <1> to <8>, wherein the first substrate includes silicon.

<10>
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 acoustic wave filter according to any one of <1> to <9>, wherein the functional electrode includes the plurality of first electrode fingers and the plurality of second electrode fingers.

<11>
The acoustic wave filter according to any one of <1> to <9>, wherein the functional electrode includes, in order from the third principal surface, a first planar electrode, a piezoelectric thin film, and a second planar electrode.

<12>
The acoustic wave filter according to <11>, wherein the second substrate includes silicon.

This invention can be widely used as a compact acoustic wave filter in communication devices such as mobile phones.

REFERENCE SIGNS LIST 1 Acoustic wave filter 10, 70 Substrate 10a, 10b, 70a, 70b Main surface 11 Via conductor 12 Planar electrode 13 Insulating film 21, 22, 23, 24 Signal wiring 25, 26 Functional electrode 27, 28 Connection wiring 30 Frame body 40 Bump electrode 41, 41A, 42, 42A Insulating member 45 Filler 50 Piezoelectric substrate 51 Support substrate 52 Intermediate layer 53 Piezoelectric film 54 IDT electrode 55, 58 Protective layer 57 Piezoelectric single crystal substrate 60 Acoustic wave resonator 60a, 60b Interdigital electrode 61a, 61b Electrode fingers 62a, 62b Busbar electrode 65 Support substrate 66 Lower electrode 67 Piezoelectric layer 68 Upper electrode 160 Gap 540 Adhesion layer 542 Main electrode layer

Claims (12)

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 disposed between the first principal surface and the third principal surface, the frame surrounding the functional electrodes when the first principal surface and the third principal surface are viewed in plan;
signal wiring connected to the functional electrodes and in contact with the first principal surface and the third principal surface;
an insulating member disposed between the frame body and the signal wiring and in contact with the frame body and the signal wiring;
At least a portion of the signal wiring is located outside an inner surface of the frame body that contacts the internal space of the frame body in the plan view, and is located inside an outer surface of the frame body.
Acoustic wave filters. the insulating member surrounds the signal wiring in the plan view;
The acoustic wave filter according to claim 1 . the frame surrounds the insulating member and the signal wiring in the plan view;
The acoustic wave filter according to claim 2 . the signal wiring transmits a high-frequency signal that propagates through the functional electrode;
The acoustic wave filter according to any one of claims 1 to 3. The frame includes a conductor portion made of metal.
The acoustic wave filter according to any one of claims 1 to 4. The frame is connected to ground.
The acoustic wave filter according to claim 5 . the insulating member includes an insulating material and a filler;
The thermal conductivity of the filler is higher than the thermal conductivity of the insulating material.
The acoustic wave filter according to any one of claims 1 to 6. moreover,
a via conductor disposed on the first substrate from the first main surface toward the second main surface and connected to the signal wiring;
The acoustic wave filter according to any one of claims 1 to 7. the first substrate comprises silicon;
The acoustic wave filter according to any one of claims 1 to 8. 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 9. 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 9. the second substrate comprises silicon;
The acoustic wave filter according to claim 11 .