Elastic wave element and communication device

Abstract

In this elastic wave element, an Interdigital Transducer (IDT) electrode has a first layer that is composed of a first conductive material. The first layer has a thickness greater than 100 angstroms. Besides, the first layer overlies a piezoelectric layer directly or with the intervention of a metal layer that is equal to or less than 100 angstroms. When the electrode finger pitch of the IDT electrode is defined as p (μm) and the value obtained by dividing the thickness of the first layer (μm) by 2 × p0.101 is defined as standardized thickness t1, this standardized thickness t1 and the sound velocity V1 of a bulk longitudinal wave (m / s) propagating through the first material satisfy the following expression: 2.14 × 10−6V1 – 1.16 × 10−2 < t1 < 1.17 × 10−5V1 – 1.63 × 10−2

Description

Acoustic wave element and communication device

[0001] The present disclosure relates to an acoustic wave device and a communication device including the acoustic wave device.

[0002] An acoustic wave element has been known that has a piezoelectric layer and an interdigital transducer (IDT) electrode overlapping the piezoelectric layer, and utilizes acoustic waves propagating through the piezoelectric layer (see, for example, Patent Document 1). Patent Document 1 proposes a thickness of the IDT electrode that can reduce spurious signals that occur on the low-frequency side of the resonant frequency.

[0003] JP 2018-88601 A

[0004] An acoustic wave element according to one aspect of the present disclosure includes a support substrate, a piezoelectric layer disposed on the support substrate, and an IDT electrode disposed on the piezoelectric layer. The IDT electrode includes a first layer made of a conductive first material. The first layer has a thickness greater than 100 Å and overlaps the piezoelectric layer directly or via a metal layer of 100 Å or less that contacts the first layer and the piezoelectric layer. The pitch of the electrode fingers of the IDT electrode is p (μm), and the thickness (μm) of the first layer is 2p ０．１０１ The value obtained by dividing by 2.14×10 is defined as the normalized thickness t1. In this case, the normalized thickness t1 and the sound velocity V1 (m / s) of the bulk longitudinal wave propagating through the first material are expressed by the following formula: 2.14×10 －６ V1-1.16 x 10 －２ <t1<1.17×10 －５ V1-1.63 x 10 －２ Meet the following.

[0005] An acoustic wave element according to one aspect of the present disclosure includes a support substrate, a piezoelectric layer disposed on the support substrate, and an IDT electrode disposed on the piezoelectric layer. The IDT electrode includes a first layer made of a conductive first material and an upper structure overlying the first layer and made of one or more materials different from the first material. The first layer has a thickness greater than 100 Å and overlies the piezoelectric layer directly or via a metal layer having a thickness of 100 Å or less that contacts the first layer and the piezoelectric layer. If the upper structure includes an insulating layer having a thickness of 150 Å or less that forms the upper surface of the IDT electrode, the portion between the upper surface of the first layer and the lower surface of the insulating layer is defined as a second layer. If the upper structure does not include the insulating layer, the portion between the upper surface of the first layer and the upper surface of the IDT electrode is defined as the second layer. In this case, the second layer has a thickness greater than 150 Å. The pitch of the electrode fingers of the IDT electrode is p (μm), and the thickness (μm) of the second layer is 2p ０．１０１ The value obtained by dividing by 4.77×10 is defined as the normalized thickness t2. At this time, the normalized thickness t2 and the sound velocity V1 (m / s) of the bulk longitudinal wave propagating through the first material are expressed by the following formula: －６ V1-1.18 x 10 －２ <t2<2.52×10 －６ V1 + 4.09 x 10 －２ Meet the following.

[0006] An acoustic wave element according to one aspect of the present disclosure includes a support substrate, a piezoelectric layer disposed on the support substrate, and an IDT electrode disposed on the piezoelectric layer. The IDT electrode includes a first layer made of a conductive first material and an upper structure overlying the first layer and made of one or more materials different from the first material. The first layer has a thickness greater than 100 Å and overlies the piezoelectric layer directly or via a metal layer of 100 Å or less that contacts the first layer and the piezoelectric layer. If the upper structure includes an insulating layer having a thickness of 150 Å or less that forms the upper surface of the IDT electrode, the portion between the upper surface of the first layer and the lower surface of the insulating layer is defined as the second layer. If the upper structure does not include the insulating layer, the portion between the upper surface of the first layer and the upper surface of the IDT electrode is defined as the second layer. In this case, the second layer has a thickness greater than 150 Å. The average density ρ (g / cm) of the second layer is 100 Å or less. ３ ) and the average sound velocity V2 (m / s) of bulk longitudinal waves propagating through the second layer satisfy the following formula: −135.64ρ+4155.6<V2<−2470.1ρ+16872.

[0007] A communication device according to one aspect of the present disclosure includes a filter having any of the above-described acoustic wave elements, an antenna connected to the filter, and an integrated circuit element connected to the filter.

[0008] 1 is a plan view showing the configuration of an acoustic wave element according to an embodiment; FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1; FIG. 3 is a diagram showing the configuration conditions of an electrode in terms of the relationship between the bulk longitudinal wave velocity of a first layer of the electrode and the thickness of the first layer; FIG. 4 is a diagram showing the configuration conditions of an electrode in terms of the relationship between the bulk longitudinal wave velocity of a first layer of the electrode and the thickness of the second layer of the electrode; FIG. 5 is a diagram showing the configuration conditions of an electrode in terms of the relationship between the bulk longitudinal wave velocity of a first layer of the electrode and the total thickness of the electrode; FIG. 6 is a cross-sectional view showing another example of a composite substrate of an acoustic wave element; FIG. 7 is a cross-sectional view showing yet another example of a composite substrate of an acoustic wave element; FIG. 8 is a diagram showing an example of a simulation result in which the material of the piezoelectric layer is different from that of FIG. 8; FIG. 9 is a diagram showing an example of a simulation result in which the configuration below the piezoelectric layer is different from that of FIG. 8; FIG. 10 is a diagram showing an example of a simulation result in which the pitch of the electrode fingers is different from that of FIG. 8; and FIG. 11 is a diagram showing an example of the characteristics of an acoustic wave element. 12B is a diagram showing an example of the characteristics of an acoustic wave element in which the material of the first layer and the material of the second layer are reversed in the acoustic wave element of FIG. 12A. FIG. 12C is a schematic diagram showing another example of a laminate structure for electrodes. FIG. 12D is a schematic diagram showing yet another example of a laminate structure for electrodes. FIG. 12E is a schematic diagram showing yet another example of a laminate structure for electrodes. FIG. 12F is a schematic diagram showing yet another example of a laminate structure for electrodes. FIG. 12G is a circuit diagram showing a schematic configuration of a duplexer including an acoustic wave element according to an embodiment. FIG. 12H is a block diagram showing a configuration of a communication device including an acoustic wave element according to an embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic. Therefore, for example, the dimensional ratios in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional ratios may not match between drawings. Certain shapes and / or dimensions may be exaggerated, and details may be omitted. However, the above does not deny that the actual shapes and / or dimensions may be as shown in the drawings, or that features of shapes and / or dimensions may be extracted from the drawings.

[0010] 1 is a schematic plan view showing an example of the configuration of an acoustic wave device 1 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG.

[0011] For convenience, these figures are labeled with a Cartesian coordinate system D1D2D3. As will be understood from the description below, the D3 direction is the normal direction to the upper surface of the composite substrate 3. The D1 direction is the propagation direction of an elastic wave propagating along the upper surface of the composite substrate 3. The D2 direction is a direction perpendicular to the D1 and D3 directions. Either direction of the elastic wave element 1 may be considered to be upward or downward. However, in the description of the embodiments, for convenience, the +D3 side may be considered to be upward, and terms such as upper surface or lower surface may be used.

[0012] Acoustic wave element 1 includes, for example, a composite substrate 3 having piezoelectricity on at least the upper surface thereof, and an IDT electrode 19 located on composite substrate 3. Composite substrate 3 includes, for example, a piezoelectric layer 11 that forms the upper surface of composite substrate 3. IDT electrode 19 includes, for example, a first conductor layer 35 (an example of a first layer) that overlaps piezoelectric layer 11, and a second conductor layer 37 (an example of a second layer) that overlaps first conductor layer 35, as shown in FIG.

[0013] An electrical signal input to the IDT electrode 19 is converted into an elastic wave that propagates through the piezoelectric layer 11. The elastic wave that propagates through the piezoelectric layer 11 is converted into an electrical signal that is output from the IDT electrode 19. Then, for example, resonance of the elastic wave is utilized to realize resonance and / or filtering of the electrical signal.

[0014] 3 to 6 are diagrams showing the configuration conditions of the first and second layers (e.g., the first conductor layer 35 and the second conductor layer 37). The first and second layers are configured so that the combinations of at least two of their normalized thicknesses (t1, t2, and t3), sound velocities (V1 and V2), and densities (ρ) fall within the ranges indicated by hatching in FIGS. 3 to 6. This improves the characteristics of the acoustic wave device 1. For example, spurious signals at frequencies higher than the anti-resonance frequency are reduced.

[0015] The above is an overview of the acoustic wave device 1 according to the embodiment. The following describes the embodiment in the following order: 1. Basic configuration of acoustic wave device 1 (FIGS. 1 and 2) 1.1. Composite substrate 3 1.2. Electrode layer (IDT electrode 19) 1.3. Other configurations 2. Configuration conditions for IDT electrodes 2.1. Definitions of sound velocity and normalized thickness 2.2. Ranges of parameter values ​​(FIGS. 3 to 6) 2.3. Process for deriving configuration conditions (FIGS. 7A to 12B) 2.3.1. Overview of the derivation process 2.3.2. Characteristics to be satisfied 2.3.3. Conditions for composite substrate 2.3.4. Sound velocity of first layer 3. Other examples of electrodes (FIG. 13) 4. Demultiplexer 101 (FIG. 14) 5. Communication device (FIG. 15) 6. Summary of the embodiment

[0016] 1 includes a so-called one-port acoustic wave resonator (resonator 15). Resonator 15 resonates when an electrical signal of a predetermined frequency is input to one of terminals 17A and 17B, which are conceptually and schematically shown, and can output the resonated signal from the other of terminals 17A and 17B. In the following description, for convenience, the acoustic wave element 1 and resonator 15 may not be distinguished from each other.

[0017] As described above, acoustic wave element 1 (resonator 15) includes composite substrate 3 and IDT electrode 19. Acoustic wave element 1 also includes a pair of reflectors 21 located on both sides of IDT electrode 19. From another perspective, acoustic wave element 1 also includes composite substrate 3 and electrode layer 5 overlapping composite substrate 3. Electrode layer 5 includes IDT electrode 19 and a pair of reflectors 21. From another perspective, electrode layer 5 also includes first conductor layer 35 and second conductor layer 37 described above.

[0018] The area of ​​the composite substrate 3 and the electrode layer 5 where the IDT electrode 19 and the pair of reflectors 21 are located constitutes a resonator 15. As described above, the resonator 15 includes not only the IDT electrode 19 and the pair of reflectors 21 but also at least a portion of the upper surface of the composite substrate 3. However, for convenience, in the description of the embodiments, it may be expressed as if only the IDT electrode 19 and the pair of reflectors 21 (the configuration excluding the composite substrate 3) constitute the resonator 15. The area of ​​the resonator 15 where the IDT electrode 19 is arranged (the configuration excluding the area where the reflectors 21 are located) also constitutes a resonator. This resonator may be referred to as a resonator 16.

[0019] The acoustic wave used by the acoustic wave device 1 may be of any suitable type. For example, the acoustic wave may be a surface acoustic wave (SAW), a bulk acoustic wave (BAW), a boundary acoustic wave, or a plate wave (however, these acoustic waves are not necessarily clearly distinguishable). In the description of the embodiments, unless otherwise specified, a mode in which a plate wave with a relatively high speed is used as the acoustic wave may be taken as an example. From another perspective, a mode in which a resonant frequency is relatively high (for example, 4 GHz or higher) may be taken as an example.

[0020] The plate wave may be, for example, a Lamb wave or an SH (Shear Horizontal) type plate wave. A Lamb wave is a wave whose main components are a displacement component in the propagation direction (D1 direction) and a displacement component in the thickness direction (D3 direction) of the piezoelectric body. The Lamb wave may be, for example, an A mode (asymmetric mode) or an S mode (symmetric mode). The order of the A mode or S mode is also arbitrary. For example, an A mode Lamb wave may be an A1 mode Lamb wave in which the number of nodes in the thickness direction is one.

[0021] The elastic wave (bulk wave) may also be of thickness shear mode (which may be considered a type of Lamb wave). In this mode, the piezoelectric layer 11 vibrates so that the upper and lower surfaces of the piezoelectric layer 11 move parallel to each other in a direction parallel to these surfaces. The order of this mode may also be arbitrary. For example, the order of the thickness shear mode may be first, in which the number of nodes in the thickness direction is one. In other words, the thickness shear mode may be such that approximately half of the upper surface and approximately half of the lower surface of the piezoelectric layer 11 are displaced in opposite directions along the plane. When the thickness shear mode is used, unlike the description of the embodiment, propagation of the elastic wave in the D1 direction is not necessarily required.

[0022] (1.1. Composite Substrate) The composite substrate 3 may have various configurations as long as it has a piezoelectric layer 11 that forms its upper surface. In the description of the embodiments, the terms "layer" and "film" are synonymous. The composite substrate 3 illustrated in FIG. 2 has a support substrate 7, an intermediate layer 9 (an example of an acoustic film) located on the support substrate 7, and a piezoelectric layer 11 located on the intermediate layer 9. Other examples of the configuration of the composite substrate 3 will be described later in "2.3. Process for Derivation of Configuration Conditions" with reference to FIGS. 7A and 7B.

[0023] The piezoelectric layer 11, together with the IDT electrode 19, contributes to the conversion of an electric signal into an elastic wave and the conversion of an elastic wave into an electric signal. The intended elastic wave propagates mainly through the piezoelectric layer 11. The support substrate 7, for example, contributes to the reinforcement of the composite substrate 3. The intermediate layer 9, for example, contributes to the bonding between the piezoelectric layer 11 and the support substrate 7 and / or the confinement of the elastic wave propagating through the piezoelectric layer 11.

[0024] The piezoelectric layer 11 is made of, for example, a single crystal having piezoelectricity. Examples of materials that make up such a single crystal include lithium tantalate (LiTaO ３ Hereinafter, this may be abbreviated as LT.), lithium niobate (LiNbO ３ Hereinafter, this may be abbreviated as LN.) and quartz (SiO ２ The cut angle of these single crystals is arbitrary. The piezoelectric layer 11 may be made of polycrystals.

[0025] The thickness of the piezoelectric layer 11 is arbitrary. For example, when λ is twice the pitch p of the electrode fingers 27 described below, the thickness of the piezoelectric layer 11 may be 0.05λ or more, or 0.1λ or more. With such a thickness, for example, elastic waves propagating through the piezoelectric layer 11 can be utilized. Furthermore, for example, the thickness of the piezoelectric layer 11 may be 1.0λ or less. In this case, for example, insertion loss can be reduced or elastic waves in a relatively fast mode can be utilized.

[0026] The material of the intermediate layer 9 may be any material depending on the purpose. For example, the intermediate layer 9 may be made of a material having a lower acoustic velocity than the piezoelectric layer 11. In other words, the intermediate layer 9 may be a low acoustic velocity film. This makes it easier for the intended elastic waves to be confined in the piezoelectric layer 11. The acoustic velocity here may be, for example, the bulk longitudinal wave acoustic velocity, similar to the acoustic velocity in the electrodes described below, or may be the acoustic velocity calculated by √(Young's modulus / density). Specific examples of materials for the low acoustic velocity film include silicon dioxide (SiO ２ ), tantalum oxide (Ta ２ O ３ ), silicon oxynitride (Si ２ N ２ O) and glass. ２ Compounds to which fluorine, carbon, boron or the like has been added may also be used.

[0027] The thickness of the intermediate layer 9 may be any thickness depending on the purpose. For example, the thickness of the intermediate layer 9 may be thinner (as in the illustrated example), equal to, or thicker than the thickness of the piezoelectric layer 11. Furthermore, for example, the thickness of the intermediate layer 9 may be 0.01λ or more, or 0.1λ or more, and may be 1λ or less, 0.5λ or less, or 0.2λ or less. The above lower and upper limits may be combined arbitrarily. When such a thickness is adopted, for example, in an embodiment in which the intermediate layer 9 is a low acoustic velocity film, the insertion loss is reduced. Of course, the thickness of the intermediate layer 9 may be outside the above range.

[0028] The material and dimensions of the support substrate 7 are arbitrary. The material of the support substrate 7 may have a lower thermal expansion coefficient than the piezoelectric layer 11, etc. In this case, for example, it is possible to reduce the likelihood that the frequency characteristics of the resonator 15 will change due to temperature changes. Examples of such materials include semiconductors such as silicon (Si), single crystals such as sapphire, and ceramics such as aluminum oxide sintered bodies. The support substrate 7 may also be configured by stacking multiple layers made of different materials. The thickness of the support substrate 7 is, for example, thicker than the piezoelectric layer 11.

[0029] (1.2. Electrode Layer (IDT Electrode)) The configuration (material, thickness, etc.) of the electrode layer 5 is common to, for example, the IDT electrode 19 and the reflector 21 (and the wiring connected to them). However, the configuration may differ depending on the location.

[0030] The first conductor layer 35 (an example of a first layer) is entirely made of the same material (sometimes referred to as the first material). The second conductor layer 37 may be made of one or more materials. An example of a mode in which the second conductor layer 37 is made of two or more materials is a mode in which the second conductor layer 37 is made by stacking two or more layers made of different materials. However, in the description of the embodiments, unless otherwise specified, it is assumed that the second conductor layer 37 is entirely made of the same material.

[0031] The material of the first conductor layer 35 and the second conductor layer 37 is, for example, a metal. The specific type of metal is arbitrary as long as it satisfies the configuration conditions described later with reference to FIGS. 3 to 6. For example, the metal may be aluminum (Al), copper (Cu), tungsten (W), iridium (Ir), tantalum (Ta), or an alloy containing two or more of these. Furthermore, the thickness of the first conductor layer 35 and the second conductor layer 37 is also arbitrary as long as it satisfies the configuration conditions described later.

[0032] The IDT electrode 19 includes a pair of comb-tooth electrodes 23. Note that in Fig. 1, one of the comb-tooth electrodes 23 is hatched for better visibility. Each comb-tooth electrode 23 includes, for example, a bus bar 25, a plurality of electrode fingers 27 extending in parallel from the bus bar 25, and a dummy electrode 29 protruding from the bus bar 25 between the plurality of electrode fingers 27. The pair of comb-tooth electrodes 23 is arranged so that the plurality of electrode fingers 27 interdigitate with (intersect with) each other.

[0033] The bus bars 25 have, for example, a shape that extends linearly in the propagation direction of the elastic waves (direction D1) with a substantially constant width. The pair of bus bars 25 face each other in a direction (direction D2) that intersects with the propagation direction of the elastic waves. Unlike the illustrated example, the width of the bus bars 25 may vary or they may be inclined with respect to the propagation direction of the elastic waves.

[0034] Each electrode finger 27 has, for example, a shape that extends linearly with a substantially constant width in a direction (direction D2) perpendicular to the propagation direction of the elastic wave. However, the width of the electrode finger 27 may vary depending on the position in the longitudinal direction (direction D2). Examples of such electrode fingers 27 include those that utilize a so-called piston mode. In each comb-tooth electrode 23, the multiple electrode fingers 27 are arranged in the propagation direction (direction D1) of the elastic wave. Furthermore, the multiple electrode fingers 27 of one comb-tooth electrode 23 and the multiple electrode fingers 27 of the other comb-tooth electrode 23 are basically arranged alternately.

[0035] The pitch p of the electrode fingers 27 (e.g., the center-to-center distance between two adjacent electrode fingers 27) is basically constant within the IDT electrode 19. However, a narrow pitch portion where the pitch p is narrower than most of the other portions or a wide pitch portion where the pitch p is wider than most of the other portions may be provided in a part of the IDT electrode 19. Furthermore, a thinned-out portion where the electrode fingers 27 are essentially thinned out may be provided in a part of the IDT electrode 19.

[0036] In the description of the embodiments, unless otherwise specified, the pitch p refers to the pitch of a portion (most of the plurality of electrode fingers 27) excluding peculiar portions such as the narrow-pitch portion, wide-pitch portion, or thinned-out portion. In addition, if the pitch varies in most of the electrode fingers 27 excluding the peculiar portions, the average value of the pitches of most of the electrode fingers 27 (for example, 80% of the total number selected to minimize the variance) may be used as the value of the pitch p.

[0037] As will be understood from the description below, the pitch p may be set according to the intended resonant frequency. For example, the pitch p may be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more, and may be 10 μm or less, 5 μm or less, or 2 μm or less. The above lower limit and upper limit may be combined arbitrarily.

[0038] The number of electrode fingers 27 may be set appropriately depending on the electrical characteristics required of the resonator 15. Since FIG. 1 is a schematic diagram, the number of electrode fingers 27 is shown as being smaller than that shown. In reality, more electrode fingers 27 may be arranged than shown. The same applies to the strip electrodes 33 of the reflector 21, which will be described later.

[0039] The lengths of the electrode fingers 27 are, for example, equal to each other. Unlike the illustrated example, the IDT electrode 19 may be apodized, in which the lengths of the electrode fingers 27 (or, from another perspective, the so-called cross width) vary depending on the position in the propagation direction (direction D1) of the acoustic wave. The length and width of the electrode fingers 27 may be set as appropriate depending on the required electrical characteristics, etc.

[0040] The dummy electrode 29 has a shape that protrudes in a direction perpendicular to the propagation direction of the elastic wave with, for example, a substantially constant width. The width is, for example, equal to the width of the electrode fingers 27. The multiple dummy electrodes 29 are arranged at the same pitch as the multiple electrode fingers 27, and the tip of the dummy electrode 29 of one comb-tooth electrode 23 faces the tip of the electrode finger 27 of the other comb-tooth electrode 23 across a gap. Note that the IDT electrode 19 may not include the dummy electrode 29.

[0041] The pair of reflectors 21 are located on both sides of the IDT electrode 19 in the propagation direction of the acoustic wave. Each reflector 21 may be, for example, electrically floating or may be applied with a reference potential. Each reflector 21 is formed, for example, in a lattice shape. That is, the reflector 21 includes a pair of bus bars 31 facing each other and a plurality of strip electrodes 33 extending between the pair of bus bars 31. The pitch of the plurality of strip electrodes 33 and the pitch between adjacent electrode fingers 27 and strip electrodes 33 are, for example, equal to the pitch of the plurality of electrode fingers 27.

[0042] When a voltage is applied to the pair of comb-tooth electrodes 23, the voltage is applied to the piezoelectric layer 11 by the multiple electrode fingers 27, causing the piezoelectric layer 11 to vibrate. That is, elastic waves are excited. Among the elastic waves of various wavelengths propagating in various directions, the elastic waves propagating in the arrangement direction of the multiple electrode fingers 27, with the pitch p of the multiple electrode fingers 27 being approximately half the wavelength (λ / 2), tend to have large amplitudes because the multiple waves excited by the multiple electrode fingers 27 overlap in phase. Furthermore, the elastic waves propagating through the piezoelectric layer 11 are converted into electrical signals by the multiple electrode fingers 27. At this time, similar to when elastic waves are excited, the intensity of the electrical signals converted from the elastic waves propagating in the arrangement direction of the multiple electrode fingers 27, with the pitch p of the multiple electrode fingers 27 being approximately half the wavelength (λ / 2), tends to be strong. Due to the above-described effects (and other effects not described here), the elastic wave element 1 functions as a resonator whose resonant frequency is, for example, the frequency of elastic waves with the pitch p being half the wavelength.

[0043] (1.3. Other Configurations) The acoustic wave device 1 may be packaged as appropriate. For example, the packaging may be such that the illustrated configuration is mounted on a substrate (not shown) with a gap between them so that the upper surface of the piezoelectric layer 11 faces the substrate, and then sealed with resin. Alternatively, the packaging may be a wafer-level package in which a box-shaped cover is provided on the piezoelectric layer 11.

[0044] 3 to 6 , the ranges of values ​​of the parameters (normalized thicknesses t1, t2, and t3, acoustic velocities V1 and V2, and density ρ) related to the first and second layers (e.g., first conductor layer 35 and second conductor layer 37) according to the embodiment will be described. Acoustic wave device 1 according to the embodiment may satisfy only one, two, three, or all of the four ranges shown in FIGS. 3 to 6 .

[0045] 13A to 13E, the second layer is not limited to the second conductor layer 37. However, in the description herein, for convenience, the terms first conductor layer 35 and second conductor layer 37 may be used instead of the terms first layer and second layer unless otherwise specified. Furthermore, the layer combining the first layer and second layer may be referred to as the third layer.

[0046] (2.1. Definitions of Sound Velocity and Normalized Thickness) Figures 3 to 6 show conditions related to the sound velocity V1 in the first layer or the sound velocity V2 in the second layer. The sound velocities V1 and V2 are assumed to be the sound velocities (m / s) of bulk longitudinal waves propagating through the first layer or the second layer. Whether an actual product satisfies the conditions shown in Figures 3 to 6 may be determined by measuring the sound velocity of the bulk longitudinal waves, or may be calculated using √(Young's modulus / density). Unless otherwise specified, the sound velocities V1 and V2 used in the process of deriving Figures 3 to 6 are calculated using √(Young's modulus / density).

[0047] 3 to 5 show the conditions for the normalized thickness t1 of the first layer, the normalized thickness t2 of the second layer, and the normalized thickness t3 (= t1 + t2) of the third layer (first and second layers). Here, the normalized thickness is the value obtained by dividing the thickness (μm) of each layer by α calculated by the following formula: α = 2p ０．１０１

[0048] As described above, in basic theory, wavelength λ is twice the pitch p of electrode fingers 27, i.e., λ = 2p. Also, in basic theory, the acoustic velocity V of piezoelectric layer 11, wavelength λ, and resonant frequency fr of resonator 15 (16) satisfy the relationship V = fr × λ. Generally, the thicknesses of the various layers of acoustic wave device 1 are normalized by dividing by 2p. This allows for a normalized thickness applicable to any resonant frequency fr to be obtained.

[0049] However, the above normalization is based on the fact that the relationship V = fr × λ is satisfied with respect to the sound velocity V of the piezoelectric layer 11. Therefore, for example, when setting configuration conditions regarding the relationship between the sound velocity V1 of the first conductor layer 35 and the thickness of the first conductor layer 35, 2p is not necessarily an appropriate value for normalizing the thickness of the first conductor layer 35. Therefore, the above α is used.

[0050] The above α is a value obtained by numerical analysis based on the results of simulation calculations. Specifically, simulation calculations were first performed under various conditions in which the values ​​of the pitch p and the sound velocity V1 of the first conductor layer 35 were varied. The resonance frequency fr of the resonator 15 (16) was obtained by this simulation calculation. Numerical analysis was then performed on the sound velocity V1 and pitch p used in the simulation calculations, and the value of the resonance frequency fr obtained by the simulation calculations, to obtain a function α(p) that fits V1 = fr × α(p). This function α(p) satisfies the above-mentioned α = 2p ０．１０１ is.

[0051] (2.2. Range of Parameter Values) FIG. 3 is a diagram showing the configuration conditions of the first layer in relation to the normalized thickness t1 of the first layer (for example, the first conductor layer 35) and the sound velocity V1 of the first layer.

[0052] In this figure, the horizontal axis represents the sound velocity V1 (m / s), and the vertical axis represents the normalized thickness t1. The hatched area represents the range of the sound velocity V1 and normalized thickness t1 of the acoustic wave device 1 according to the embodiment. Line L1 represents the lower limit of the normalized thickness t1 within the range. Line L2 represents the upper limit of the normalized thickness t1 within the range.

[0053] The normalized thickness t1 that falls within the hatched area can be expressed as an inequality using the equations representing the lines L1 and L2 as follows: 2.14×10 －６ V1-1.16 x 10 －２ <t1<1.17×10 －５ V1-1.63 x 10 －２

[0054] FIG. 4 is a diagram showing the configuration conditions of the electrode layer 5 in relation to the normalized thickness t2 of the second layer (for example, the second conductor layer 37) and the sound velocity V1 of the first layer.

[0055] In this figure, the horizontal axis represents the sound velocity V1 (m / s). The vertical axis represents the normalized thickness t2. The hatched area represents the range of the sound velocity V1 and normalized thickness t2 of the acoustic wave device 1 according to the embodiment. Line L3 represents the lower limit of the normalized thickness t2 within the range. Line L4 represents the upper limit of the normalized thickness t2 within the range.

[0056] The normalized thickness t2 that falls within the hatched area can be expressed as an inequality using the equations representing lines L3 and L4 as follows: 4.77×10 －６ V1-1.18 x 10 －２ <t2<2.52×10 －６ V1 + 4.09 x 10 －２

[0057] FIG. 5 is a diagram showing the configuration conditions of the electrode layer 5 in relation to the normalized thickness t3 (= t1 + t2) of the third layer, which is the sum of the first layer (e.g., the first conductor layer 35) and the second layer (e.g., the second conductor layer 37), and the sound velocity V1 of the first layer.

[0058] In this figure, the horizontal axis represents the sound velocity V1 (m / s). The vertical axis represents the normalized thickness t3. The hatched area represents the range of the sound velocity V1 and normalized thickness t3 of the acoustic wave device 1 according to the embodiment. Line L5 represents the lower limit of the normalized thickness t3 within the range. Line L6 represents the upper limit of the normalized thickness t3 within the range.

[0059] The normalized thickness t3 that falls within the hatched area can be expressed as an inequality using the equations representing lines L5 and L6 as follows: 6.91×10 －６V1-2.34 x 10 －２ <t3<1.42×10 －５ V1 + 2.45 x 10 －２

[0060] FIG. 6 shows the density ρ (g / cm 3 ) of the second layer (e.g., the second conductor layer 37 ). ３ 10 is a diagram showing the configuration conditions of the second layer in relation to the sound velocity V2 (m / s) in the second layer.

[0061] In this figure, the horizontal axis represents density ρ (g / cm ３ ) to avoid confusion with the densities of other layers. The density ρ of the second layer is sometimes referred to as density ρ2. The vertical axis represents the sound velocity V2 (m / s). The hatched area represents the range of density ρ and sound velocity V2 of the acoustic wave device 1 according to the embodiment. Line L7 represents the lower limit of the sound velocity V2 in the above range. Line L8 represents the upper limit of the sound velocity V2 in the above range.

[0062] The sound velocity V2 that falls within the hatched area can be expressed as an inequality using the equations for lines L7 and L8 as follows: -135.64ρ + 4155.6 < V2 < -2470.1ρ + 16872

[0063] The values ​​of various parameters of acoustic wave device 1 according to the embodiment may be set to values ​​that fall within a range that is narrower than the range (hatched area) shown in Figures 3 to 6. For example, the parameter values ​​may be set to fall within a range in which the width in the direction parallel to the vertical axis is 1 / 2 or 1 / 3 of the width in the direction parallel to the vertical axis of the range shown in Figures 3 to 6 and the center line coincides with the center line of the range shown in Figures 3 to 6.

[0064] (2.3. Process for Derivation of Configuration Conditions) (2.3.1. Overview of Derivation Process) The configuration conditions for the IDT electrode 19 shown in FIGS. 3 to 6 are derived by the following procedure.

[0065] Simulation calculations were performed to determine the characteristics of the resonator 15 for multiple cases in which the values ​​of the parameters (t1, t2, t3, V1, V2, and ρ) related to the configuration conditions were changed. For example, in the case of determining the configuration conditions in terms of the relationship between the sound speed V1 and the normalized thickness t1 as shown in Figure 3, simulation calculations were performed for multiple cases in which various values ​​were set for at least the sound speed V1 and the normalized thickness t1.

[0066] In practice, even when determining the structural conditions for the relationship between the sound speed V1 and the normalized thickness t1 shown in Fig. 3, various values ​​were set for other parameters and simulation calculations were performed for a huge number of cases. Specifically, simulation calculations were performed for a huge number of cases in which the sound speeds V1 and V2, the normalized thicknesses t1 and t2 (and t3), and the density ρ of the second layer as well as other parameters (for example, the pitch p) were set to different values, and a single database for obtaining Figs. 3 to 6 was created.

[0067] The ranges of the parameters shown in FIGS. 3 to 6 in the simulation calculations are as follows: V1: 3300 m / s to 13300 m / s V2: 3300 m / s to 13300 m / s t1: 0.0035 to 0.164 t2: 0.0070 to 0.087 t3: 0.0105 to 0.251 ρ2: 2.0 g / cm ３ ~5.0 g / cm ３

[0068] From the vast number of cases mentioned above, we extracted cases where the characteristics obtained by simulation calculations satisfied certain requirements, which will be described later.

[0069] The parameter values ​​of the extracted cases can be plotted on a graph having horizontal and vertical axes similar to those in FIGS. 3 to 6 . Then, from multiple cases with the same horizontal axis values, the case with the smallest vertical axis value and the case with the largest vertical axis value can be extracted. For example, in a graph similar to that in FIG. 3 , from multiple cases with the same value of the sound velocity V1, the case with the smallest normalized thickness t1 and the case with the largest normalized thickness t1 can be extracted. By performing this procedure for various values ​​on the horizontal axis, the lower and upper limits on the vertical axis at which the characteristics of the resonator 15 satisfy the specified requirements can be determined for various values ​​on the horizontal axis. In practice, it is not necessary to create a graph with the plots as described above; the procedure described above can be essentially performed.

[0070] Then, approximate lines were calculated for the lower limit values ​​of the vertical axis specified for various values ​​on the horizontal axis. These approximate lines correspond to lines L1, L3, L5, and L7, which indicate the lower limits of the ranges shown in Figures 3 to 6. Similarly, approximate lines were calculated for the upper limit values ​​of the vertical axis specified for various values ​​on the horizontal axis. These approximate lines correspond to lines L2, L4, L6, and L8, which indicate the upper limits of the ranges shown in Figures 3 to 6.

[0071] The above is an outline of the process for deriving the ranges shown in FIGS.

[0072] (2.3.2. Characteristics to be Satisfied) As described above, in the derivation of Figures 3 to 6, cases are extracted in which the characteristics obtained by simulation calculation satisfy certain requirements. These certain requirements are as follows.

[0073] 12A is a diagram showing an example of the characteristics of the resonator 15. In this diagram, the horizontal axis represents frequency (MHz). The vertical axis on the left represents the absolute value of impedance |Z| (Ω). The vertical axis on the right represents the phase θ (°) of impedance. Line LN1 represents |Z| of the resonator 15. Line LN2 represents θ of the resonator 15.

[0074] As shown by the line LN1, |Z| of the resonator 15 has a minimum value at the resonance frequency (approximately 4700 MHz in the illustrated example) and a maximum value at the antiresonance frequency (approximately 4900 MHz in the illustrated example). Also, as shown by the line LN2, θ of the resonator 15 approaches 90° in the range between the resonance frequency and the antiresonance frequency (referred to as the "first range" in this paragraph and the next paragraph) and approaches −90° outside the first range.

[0075] In general, the closer θ is to 90° within the first range, the better the characteristics of the resonator 15. Also, the closer θ is to −90° outside the first range, the better the characteristics of the resonator 15. When spurious signals occur outside the first range, θ moves away from −90° (θ becomes larger).

[0076] Considering the relationship between the spurious and θ, the above-mentioned predetermined requirement is that, when the anti-resonance frequency is fa, the θ of the resonator 15 is -60° or less in the range of fa to 1.5fa. In other words, the predetermined requirement is that the spurious is small on the frequency side higher than the anti-resonance frequency. In the procedure actually used to obtain Figures 3 to 6, the predetermined requirement is that, with fa = 5 GHz, the θ of the resonator 15 is -60° or less in the range of 5 GHz to 7.5 GHz. The value of 1.5 for 1.5fa and the value of -60° for θ are set based on experience.

[0077] The value of 5 GHz as fa is a design value determined by a relatively simple calculation formula based on the pitch p, the velocity of the elastic wave in the piezoelectric layer 11, the capacitance of the resonator 15, etc. Therefore, the anti-resonance frequency determined by simulation calculation that takes into account the influence of the parameters shown in Figures 3 to 6 may deviate from 5 GHz, as illustrated in Figure 12A.

[0078] 3 to 6 are derived based on simulation results for four different configurations of the composite substrate 3. Specifically, they are as follows:

[0079] In the structure illustrated in Fig. 2, the piezoelectric layer 11 was formed of LT in the first embodiment. The second embodiment was formed by replacing LT with LN in the first embodiment. The third embodiment was formed by providing a multilayer film 39 (see Fig. 7A) instead of the intermediate layer 9 (low acoustic velocity film) in the first embodiment. The fourth embodiment was formed by providing a cavity 7a (see Fig. 7B) instead of the intermediate layer 9 in the first embodiment.

[0080] Then, for each of the first to fourth aspects, simulation calculations were performed on a huge number of cases in which various parameter values ​​were varied, as described above. As a result, for each aspect, the lower and upper limits of the vertical axis for each horizontal axis value in FIGS. 3 to 6 were determined. Then, the average value of the four aspects was determined for the lower limit of the vertical axis for each horizontal axis value in FIGS. 3 to 6. Similarly, the average value of the four aspects was determined for the upper limit of the vertical axis for each horizontal axis value in FIGS. 3 to 6. Furthermore, the average values ​​of the lower and upper limits of the vertical axis for various values ​​on the horizontal axis were determined. Then, an approximate straight line was determined for the average values ​​of the lower limits of the vertical axis specified for various values ​​on the horizontal axis. This approximate straight line is the lines L1, L3, L5, and L7 indicating the lower limits of the hatched areas in FIGS. 3 to 6. Similarly, an approximate straight line was determined for the average values ​​of the upper limits of the vertical axis specified for various values ​​on the horizontal axis. These approximate straight lines are lines L2, L4, L6 and L8 which indicate the upper limits of the hatched areas in FIGS.

[0081] FIG. 7A is a cross-sectional view schematically illustrating the configuration of a composite substrate 3A having a multilayer film 39 according to a third embodiment. The multilayer film 39 is, for example, composed of alternating layers of first acoustic films 39a and second acoustic films 39b, each having a different acoustic velocity and / or acoustic impedance. The acoustic velocity here may be, for example, the bulk longitudinal wave acoustic velocity, similar to acoustic velocities V1 and V2, or may be calculated by √(Young's modulus / density). The materials of the first acoustic film 39a and the second acoustic film 39b, as well as their thicknesses and the number of layers, may be appropriately selected. For example, silicon dioxide (SiO2) can be used as the material for the first acoustic film 39a. Examples of materials for the second acoustic film 39b include tantalum pentoxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), and titanium oxide (TiO2). The layer in contact with the piezoelectric layer 11 (the first acoustic film 39 a in the illustrated example) may have a different sound velocity and / or acoustic impedance from the piezoelectric layer 11 .

[0082] 7B is a cross-sectional view schematically illustrating the configuration of a composite substrate 3B having a cavity 7a according to the fourth embodiment. In this figure, the cavity 7a is realized by forming a recess in the upper surface of the support substrate 7. For example, in a planar perspective view, the cavity 7a overlaps the entire resonator 15 (or 16). In the support substrate 7, the wall of the cavity 7a and the layer constituting the bottom surface of the cavity 7a may be made of the same material or different materials.

[0083] In the description of the embodiment, for convenience, the reference numeral 3 is used to represent various composite substrates such as the composite substrates 3, 3A, and 3B. However, unless otherwise specified or unless a particular contradiction occurs, in the description using the reference numeral 3, the configuration of the composite substrate 3 may be the configuration of other composite substrates.

[0084] The above-mentioned averaging is based on the fact that the trends in the ranges shown in Figures 3 to 6 (from another perspective, the lower and upper limit lines) were similar even when various conditions were changed. An example is shown below.

[0085] 8 to 11 respectively plot the upper and lower limits of the normalized thickness t1 at various values ​​of the sound velocity V1, and correspond to FIG. 3. FIG. 8 relates to the first embodiment described above. FIG. 9 relates to the second embodiment described above. FIG. 10 relates to the third embodiment described above. FIG. 11 shows three results for the first embodiment described above, with different values ​​of pitch p. As can be seen from a comparison of these figures, regardless of whether the structure of the composite substrate 3 or the pitch is changed, the range in which the phase θ on the high-frequency side of the anti-resonance frequency is −60° or less in the relationship between the sound velocity V1 and the normalized thickness t1 is roughly the same.

[0086] 3 to 6, the sound velocity V1 in the first layer (first conductor layer 35) is used as a parameter. An example of the basis for this is shown below.

[0087] As already mentioned, Fig. 12A is a diagram showing an example of the characteristics of the resonator 15. More specifically, the characteristics shown in Fig. 12A were obtained by simulation calculation. In this simulation calculation, the first conductor layer 35 is made of CuAl ２ The second conductor layer 37 is made of Al and has a thickness of 0.1 μm.

[0088] Fig. 12B is a diagram showing the characteristics of the resonator 15 obtained by simulation calculation, similar to Fig. 12A. The conditions for the simulation in Fig. 12B are the same as those for Fig. 12A, except that the materials of the first conductor layer 35 and the second conductor layer 37 are reversed from those in Fig. 12A. Just to be clear, in the simulation calculation in Fig. 12B, the first conductor layer 35 is Al with a thickness of 0.1 μm, and the second conductor layer 37 is CuAl with a thickness of 0.1 μm. ２ is.

[0089] 12A and 12B, the characteristics of the resonator 15 differ when the materials of the first conductor layer 35 and the second conductor layer 37 are reversed. For example, in Fig. 12B, a spurious response with θ exceeding -60° occurs between 5 GHz and 7.5 GHz, but in Fig. 12A, no such spurious response occurs.

[0090] This shows that it is not necessarily possible to reduce spurious emissions at high frequencies by defining the configuration conditions of the IDT electrode 19 based on, for example, the total thickness of the first conductor layer 35 and the second conductor layer 37 and / or the average sound velocity of the entire first conductor layer 35 and the second conductor layer 37. As proposed in this embodiment, by considering the first conductor layer 35 and the second conductor layer 37 individually, the likelihood of reducing spurious emissions increases.

[0091] (3. Other Examples of Electrodes) FIGS. 13A to 13E are diagrams showing other examples of the laminated structure of the electrode layer 5 (IDT electrode 19).

[0092] 13A , the acoustic wave device 1 may have an insulating protective film 41 that covers the upper surface of the piezoelectric layer 11 from above one or more metal layers (first conductor layer 35 and second conductor layer 37 in the illustrated example). In the illustrated example, the protective film 41 does not cover the side surfaces of the metal layers, but it may cover the side surfaces of the metal layers. The protective film 41 contributes to reducing corrosion of the metal layers, for example. Examples of materials for the protective film 41 include SiO ２ and Si ３ N ４ Examples include:

[0093] 13A , the thickness of the protective film 41 is relatively thin. For example, the thickness of the protective film 41 may be 150 Å or less. From another perspective, the thickness of the protective film 41 may be thinner than the thickness of each of the first layer (first conductor layer 35) and the second layer (second conductor layer 37). Conversely, the thickness of each of the first layer and the second layer may be thicker than 150 Å, for example. The thickness of the protective film 41 may be, for example, ⅓ or less or ⅕ or less of the thickness of the first layer or the second layer.

[0094] When such a relatively thin protective film 41 is provided, the thickness of the protective film 41 on the metal layers (the first conductor layer 35 and the second conductor layer 37) may be ignored in relation to the thickness of the IDT electrode 19. This is because the protective film 41 has little effect on spurious emissions. Therefore, for example, the normalized thickness t1 of the first layer may be obtained by normalizing the thickness t01 from the top surface of the piezoelectric layer 11 to the top surface of the first layer. The normalized thickness t2 of the second layer may be obtained by normalizing the thickness t02 from the top surface of the first layer to the top surface of the second layer (the bottom surface of the protective film 41).

[0095] 13B and 13C, a protective film 41 is provided, similar to the example of FIG. 13A. However, unlike the example of FIG. 13A, the protective film 41 is relatively thick. From another perspective, the material of the second layer overlapping the first layer (first conductor layer 35) is the same as the material of the protective film 41. For convenience, in this explanation, it will be considered that the protective film 41 overlaps the first layer.

[0096] Such a relatively thick protective film 41 may contribute to compensating for changes in the characteristics of the resonator 15 due to temperature changes, in addition to protecting the metal layer from corrosion. The thickness of the relatively thick protective film 41 is the opposite of the description of the thickness of the relatively thin protective film 41, and may be, for example, greater than 150 Å. Furthermore, the thickness may be, for example, greater than ⅓, greater than ½, or greater than 1 time the thickness of the first layer.

[0097] A relatively thick protective film 41 may affect spurious emissions. Therefore, the relatively thick protective film 41 may be considered as all (in the illustrated example) or part of the second layer overlapping the first layer. For example, in the illustrated example, the normalized thickness t2 of the second layer may be obtained by normalizing the thickness t02 (thickness t02 of the protective film 41) from the top surface of the first layer to the top surface of the IDT electrode 19 (top surface of the protective film 41).

[0098] In the example of FIG. 13D , an adhesive layer 43 is interposed between the piezoelectric layer 11 and the first conductor layer 35. The adhesive layer 43 contributes to, for example, improving the bonding strength between the piezoelectric layer 11 and the first conductor layer 35. The adhesive layer 43 is, for example, a conductor layer (metal layer). The adhesive layer 43 is relatively thin. For example, the thickness of the adhesive layer 43 may be 100 Å or less. From another perspective, the thickness of the adhesive layer 43 may be thinner than the thickness of the first conductor layer 35. Conversely, the thickness of the first conductor layer 35 may be thicker than 100 Å. The thickness of the adhesive layer 43 may be, for example, ⅓ or less of the thickness of the first conductor layer 35. The material of the adhesive layer 43 is arbitrary, and may be, for example, Ti.

[0099] When such a relatively thin adhesion layer 43 is provided, the thickness of the adhesion layer 43 may be ignored in relation to the thickness of the IDT electrode 19. From another perspective, the adhesion layer 43 is not an example of the first layer, but the first conductor layer 35 overlapping the adhesion layer 43 is an example of the first layer. This is because the influence of the adhesion layer 43 on spurious emissions is small. Therefore, for example, the normalized thickness t1 of the first layer may be a normalized thickness t01 from the upper surface of the adhesion layer 43 (the lower surface of the first conductor layer 35) to the upper surface of the first conductor layer 35.

[0100] 13D , two or more layers (two layers, a first constituent layer 37A and a second constituent layer 37B, in the illustrated example) made of different materials are provided on the first layer (first conductor layer 35). In this case, the two or more layers may be regarded as the second layer as a whole. As described above, the relatively thin protective film 41 is not included in the second layer. From another perspective, the normalized thickness t2 of the second layer may be the thickness t02 from the top surface of the first layer to the bottom surface of the protective film 41 (top surface of the second constituent layer 37B).

[0101] The material of the first component layer 37A and the second component layer 37B may be a conductor (e.g., a metal) or an insulator. Furthermore, as long as the materials of the two or more layers (the first component layer 37A and the second component layer 37B) included in the first layer (first conductor layer 35) and the second layer are different from each other, adjacent layers may include layers made of the same material. For example, in the illustrated example, the material of the first conductor layer 35 and the material of the second component layer 37B may be the same.

[0102] When the second layer is composed of two or more materials, the sound velocity V2 of the second layer may be an average sound velocity. The average sound velocity may be calculated, for example, by adding up the sound velocities of each layer multiplied by the ratio of the thickness of that layer to the thickness of the second layer. When the thickness of each layer is not constant, the volume ratio of each layer may be used instead of the thickness ratio of each layer. While the sound velocity V2 has been described, the same applies to the density ρ of the second layer. That is, the average density may be used as the density ρ of the second layer, and the thickness ratio or the volume ratio may be used in the calculation.

[0103] In the example of Figure 13E, the entire IDT electrode 19 is composed of the first conductor layer 35, except for the relatively thin protective film 41. In such a case, it may be considered that only the first layer is provided and the second layer is not provided. The normalized thickness t1 of the first layer may be obtained by normalizing the thickness t01 of the first layer. Furthermore, in the embodiment, the third layer has been described as a combination of the first layer and the second layer, but if the second layer is not provided, the first layer may be considered as the third layer. In other words, the normalized thickness t1 and the normalized thickness t3 may be the same.

[0104] From the various stacked structures of the IDT electrodes 19 (electrode layers 5) exemplified above, the first and second layers for which the normalized thicknesses t1 and t2 are determined can be explained as follows.

[0105] The IDT electrode 19 has at least a first layer (first conductor layer 35) made of a conductive first material. In other words, the IDT electrode 19 does not necessarily have a second layer (FIG. 13E). The first layer has a thickness greater than 100 Å. The first layer directly overlaps the piezoelectric layer 11 (FIGS. 2, 13A-13C, and 13E). Alternatively, the first layer overlaps the piezoelectric layer 11 via a metal layer (adhesion layer 43) having a thickness of 100 Å or less that contacts the piezoelectric layer 11 and the first layer (FIG. 13D).

[0106] The IDT electrode 19 may have an upper structure overlying the upper surface of the first layer (first conductor layer 35) and composed of one or more materials different from the first material (FIGS. 2, 13A-13E). If the upper structure has an insulating layer (thin protective film 41) of 150 Å or less that forms the upper surface of the IDT electrode 19 (FIGS. 13A, 13D, and 13E), the portion between the upper surface of the first layer and the lower surface of the insulating layer may be referred to as the second layer. Note that FIG. 13E does not define such a second layer, and therefore does not include a second layer. If the upper structure does not have the insulating layer (thin protective film 41) (FIGS. 2, 13B, and 13C), the portion between the upper surface of the first layer and the upper surface of the IDT electrode 19 may be referred to as the second layer. The second layer may have a thickness greater than 150 Å.

[0107] When the IDT electrode 19 has an insulating layer (thin protective film 41) of 150 Å or less that forms the upper surface of the IDT electrode 19 ( FIGS. 13A , 13D, and 13E ), the portion between the lower surface of the first layer (e.g., first conductor layer 35) and the lower surface of the thin protective film 41 may be the third layer. When the IDT electrode 19 does not have the thin protective film 41 ( FIGS. 2 , 13B, and 13C ), the portion between the lower surface of the first conductor layer 35 and the upper surface of the IDT electrode 19 may be the third layer. The third layer may be a combination of the first and second layers ( FIGS. 2 , 3A to 3D ), or may be the first layer alone ( FIG. 13E ).

[0108] The IDT electrode 19 may have various laminated structures other than those shown in the figure. In such cases, the first and second layers may be specified based on the above description of the first and second layers.

[0109] 14 is a circuit diagram schematically illustrating the configuration of a duplexer 101 as an example of the use of acoustic wave device 1. As can be seen from the reference numerals in the upper left corner of the figure, comb-tooth electrode 23 is schematically illustrated as a two-pronged fork, and reflector 21 is represented by a single line bent at both ends.

[0110] The duplexer 101 has, for example, a transmission filter 109 that filters a transmission signal from the transmission terminal 105 and outputs the filtered signal to the antenna terminal 103, and a reception filter 111 that filters a reception signal from the antenna terminal 103 and outputs the filtered signal to a pair of reception terminals 107. In other words, the duplexer 101 is configured as a duplexer.

[0111] The transmit filter 109 is configured, for example, as a ladder filter in which a plurality of resonators 15 are connected in a ladder configuration. That is, the transmit filter 109 has a plurality of resonators 15 (series resonators) (one resonator is sufficient) connected in series between the transmit terminal 105 and the antenna terminal 103, and a plurality of resonators 15 (parallel arms, parallel resonators) (one resonator is sufficient) connecting the series line (series arms) to a reference potential. The plurality of resonators 15 constituting the transmit filter 109 are provided, for example, on the same composite substrate 3.

[0112] The receiving filter 111 is configured to include, for example, a resonator 15 and a multimode filter (including a double-mode filter) 113. The multimode filter 113 has a plurality of IDT electrodes 19 (three in the illustrated example) (resonators 16 from another perspective; reference numerals are omitted here) arranged in the propagation direction of the elastic waves, and a pair of reflectors 21 arranged on both sides thereof. The resonators 15 and multimode filter 113 that configure the receiving filter 111 are provided on, for example, the same composite substrate 3.

[0113] The transmit filter 109 and the receive filter 111 may be provided on the same composite substrate 3, or on different composite substrates 3. FIG. 14 is merely an example of the configuration of the duplexer 101. For example, the receive filter 111 may be configured with a ladder filter, similar to the transmit filter 109. Furthermore, the series resonators and parallel resonators that make up one ladder filter may be provided on separate composite substrates 3. The duplexer 101 (multiplexer) is not limited to a duplexer. For example, the duplexer may be a diplexer or may include three or more filters (e.g., a triplexer or a quadplexer). Contrary to the above description, various filters or the duplexer 101 may be considered as the acoustic wave element 1.

[0114] 15 is a block diagram showing a main part of a communication device 151 as an example of use of the acoustic wave device 1 (duplexer 101). The communication device 151 has a module 171 and a housing 173 that houses the module 171. The module 171 performs wireless communication using radio waves and includes the duplexer 101.

[0115] In module 171, a transmission information signal TIS containing information to be transmitted is modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency Integrated Circuit) 153 (an example of an integrated circuit element) to generate a transmission signal TS. Unwanted components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 155, amplified by an amplifier 157, and input to a branching filter 101 (transmission terminal 105). The branching filter 101 (transmission filter 109) then removes unwanted components outside the transmission passband from the input transmission signal TS, and outputs the removed transmission signal TS from an antenna terminal 103 to an antenna 159. The antenna 159 converts the input electrical signal (transmission signal TS) into a radio signal (radio wave) and transmits it.

[0116] Furthermore, in module 171, a radio signal (radio wave) received by antenna 159 is converted by antenna 159 into an electrical signal (received signal RS) and input to duplexer 101 (antenna terminal 103). Duplexer 101 (receive filter 111) removes unnecessary components outside the receive passband from the input received signal RS and outputs the signal from receive terminal 107 to amplifier 161. The output received signal RS is amplified by amplifier 161, and unnecessary components outside the receive passband are removed by bandpass filter 163. The received signal RS is then frequency-downshifted and demodulated by RF-IC 153 to generate received information signal RIS.

[0117] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog audio signals or digitized audio signals. The passband of the radio signal may be set as appropriate, and in this embodiment, a relatively high-frequency passband (e.g., 3 GHz or higher or 5 GHz or higher) is also possible. The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. While the direct conversion method is exemplified in FIG. 15 , other appropriate circuit methods may be used, such as a double superheterodyne method. Furthermore, FIG. 15 schematically illustrates only the essential components; low-pass filters, isolators, etc. may be added at appropriate positions, and the positions of amplifiers, etc. may be changed.

[0118] Module 171 has, for example, components from RF-IC 153 to antenna 159 on the same circuit board. That is, acoustic wave element 1 (part or all of duplexer 101) is combined with other components to form a module. Note that acoustic wave element 1 may be included in communication device 151 without being modularized. Furthermore, the components exemplified as components of module 171 may be located outside the module or may not be housed in housing 173. For example, antenna 159 may be exposed to the outside of housing 173.

[0119] (6. Summary of the Embodiment) As described above, the acoustic wave device 1 according to this embodiment includes a support substrate 7, a piezoelectric layer 11 located on the support substrate 7, and an IDT electrode 19 located on the piezoelectric layer 11. The IDT electrode 19 includes a first layer (first conductor layer 35) made of a conductive first material. The first conductor layer 35 has a thickness greater than 100 Å. The first conductor layer 35 overlaps the piezoelectric layer 11 directly, or overlaps the piezoelectric layer 11 via a metal layer (adhesion layer 43) having a thickness of 100 Å or less that contacts the piezoelectric layer 11 and the first conductor layer 35. Let the pitch of the electrode fingers 27 of the IDT electrode 19 be p (μm), and let the thickness (μm) of the first conductor layer 35 be 2p ０．１０１ When the value obtained by dividing by 1 / 2 is defined as the normalized thickness t1, the normalized thickness t1 and the sound velocity V1 (m / s) of the bulk longitudinal wave propagating through the first material are expressed by the following formula: 2.14 × 10 －６ V1-1.16 x 10 －２ <t1<1.17×10 －５ V1-1.63 x 10 －２ That is, the normalized thickness t1 and the sound velocity V1 fall within the hatched region in FIG.

[0120] In this case, as is clear from the process of deriving the hatched region in Fig. 3, it is easy to reduce spurious signals at frequencies higher than the anti-resonance frequency. As explained with reference to Figs. 12A and 12B, since attention is focused on the sound speed and thickness of the first layer, rather than the sound speed and thickness of the entire IDT electrode 19, it is possible to reduce spurious signals that could not be reduced by focusing only on the sound speed and thickness of the entire IDT electrode 19. Furthermore, instead of normalizing with λ (= 2p), α (= 2p) calculated from the relationship between the resonant frequency and the sound speed of the IDT electrode 19 is used. ０．１０１ ), the effect of reducing spurious components is easily maintained when applied to acoustic wave devices 1 with different resonant frequencies.

[0121] Note that there are other parameters that affect spurious responses besides the normalized thickness t1 and sound velocity V1 used in FIG. 3 . Therefore, even if the normalized thickness t1 and sound velocity V1 fall within the hatched region in FIG. 3 , this does not necessarily guarantee the characteristics used as the basis in the process of deriving FIG. 3 (the phase θ of the spurious responses on the high-frequency side of the anti-resonance frequency being −60° or less). However, as long as the other parameters are within a realistic range, the tendency of the influence of the normalized thickness t1 and sound velocity V1 on the high-frequency side spurious responses is the same. Therefore, even if the other parameters are arbitrary values, the fact remains that it is easy to reduce spurious responses on the high-frequency side of the anti-resonance frequency when the normalized thickness t1 and sound velocity V1 fall within the hatched region in FIG. 3 . From another perspective, although the best effect may not be obtained, it is easier to obtain a better effect.

[0122] From another perspective, the acoustic wave device 1 according to this embodiment includes a support substrate 7, a piezoelectric layer 11 located on the support substrate 7, and an IDT electrode 19 located on the piezoelectric layer 11. The IDT electrode 19 includes a first layer (first conductor layer 35) made of a conductive first material, and an upper structure (e.g., second conductor layer 37) that overlaps the upper surface of the first conductor layer 35 and is made of one or more materials different from the first material. The first conductor layer 35 has a thickness greater than 100 Å. The first conductor layer 35 overlaps the piezoelectric layer 11 directly or via a metal layer (adhesion layer 43) having a thickness of 100 Å or less that is in contact with the piezoelectric layer 11 and the first conductor layer 35. When the upper structure has an insulating layer (thin protective film 41) with a thickness of 150 Å or less that forms the upper surface of the IDT electrode 19, the portion between the upper surface of the first conductor layer 35 and the lower surface of the thin protective film 41 is defined as the second layer, and when the upper structure does not have the thin protective film 41, the portion between the upper surface of the first conductor layer 35 and the upper surface of the IDT electrode 19 is defined as the second layer, and the second layer (e.g., second conductor layer 37) has a thickness greater than 150 Å. When the pitch of the electrode fingers 27 of the IDT electrode 19 is p (μm), and the thickness (μm) of the second layer is 2p ０．１０１When the value obtained by dividing by 1 / 2 is defined as the normalized thickness t2, the normalized thickness t2 and the sound velocity V1 (m / s) of the bulk longitudinal wave propagating through the first material are expressed by the following formula: 4.77 × 10 －６ V1-1.18 x 10 －２ <t2<2.52×10 －６ V1 + 4.09 x 10 －２ That is, the normalized thickness t2 and the sound velocity V1 fall within the hatched region in FIG.

[0123] In this case, as is clear from the process of deriving the hatched region in Fig. 4, it is easier to reduce spurious emissions at frequencies higher than the anti-resonance frequency. The above-mentioned explanation about the effect of the normalized thickness t1 and the sound velocity V1 falling within the hatched region in Fig. 3 may be applied to the effect of the normalized thickness t2 and the sound velocity V2 falling within the hatched region in Fig. 4 by replacing the term normalized thickness t1 with the term normalized thickness t2.

[0124] From another perspective, the acoustic wave device 1 according to this embodiment includes a support substrate 7, a piezoelectric layer 11 located on the support substrate 7, and an IDT electrode 19 located on the piezoelectric layer 11. The IDT electrode 19 includes a first layer (first conductor layer 35) made of a conductive first material, and an upper structure (e.g., second conductor layer 37) that overlaps the upper surface of the first conductor layer 35 and is made of one or more materials different from the first material. The first conductor layer 35 has a thickness greater than 100 Å. The first conductor layer 35 overlaps the piezoelectric layer 11 directly or via a metal layer (adhesion layer 43) having a thickness of 100 Å or less that is in contact with the piezoelectric layer 11 and the first conductor layer 35. When the upper structure has an insulating layer (thin protective film 41) with a thickness of 150 Å or less that forms the upper surface of the IDT electrode 19, the portion between the upper surface of the first conductor layer 35 and the lower surface of the thin protective film 41 is defined as the second layer, and when the upper structure does not have the thin protective film 41, the portion between the upper surface of the first conductor layer 35 and the upper surface of the IDT electrode 19 is defined as the second layer, and the second layer (e.g., second conductor layer 37) has a thickness greater than 150 Å. The average density ρ (g / cm ３) and the average sound velocity V2 (m / s) of the bulk longitudinal waves propagating through the second layer satisfy the following equation: −135.64ρ+4155.6<V2<−2470.1ρ+16872. That is, the density ρ and the sound velocity V2 fall within the hatched region in FIG.

[0125] In this case, as is clear from the process of deriving the hatched region in Fig. 6, it is easier to reduce spurious emissions at frequencies higher than the anti-resonance frequency. The above-mentioned explanation about the effect of the normalized thickness t1 and the sound velocity V1 falling within the hatched region in Fig. 3 may be applied to the effect of the density ρ and the sound velocity V2 falling within the hatched region in Fig. 6 by replacing the terms normalized thickness t1 and sound velocity V1 with the terms density ρ and sound velocity V2.

[0126] In this embodiment, when the IDT electrode 19 has an insulating layer (thin protective film 41) of 150 Å or less that forms the upper surface of the IDT electrode 19, the portion between the lower surface of the first layer (e.g., the first conductor layer 35) and the lower surface of the thin protective film 41 is defined as the third layer (e.g., a combination of the first and second layers). When the IDT electrode 19 does not have the thin protective film 41, the portion between the lower surface of the first conductor layer 35 and the upper surface of the IDT electrode 19 is defined as the third layer. The third layer may have a thickness greater than 150 Å. ０．１０１ When the value obtained by dividing by t3 is the normalized thickness, the following formula is obtained: 6.91 × 10 －６ V1-2.34 x 10 －２ <t3<1.42×10 －５ V1 + 2.45 x 10 －２ That is, the normalized thickness t3 and the sound velocity V1 may fall within the hatched region in FIG.

[0127] In this case, as is clear from the process of deriving the hatched region in Fig. 5, it is easier to reduce spurious emissions at frequencies higher than the anti-resonance frequency. The above-mentioned explanation about the effect of the normalized thickness t1 and the sound velocity V1 falling within the hatched region in Fig. 3 may be applied to the effect of the normalized thickness t3 and the sound velocity V1 falling within the hatched region in Fig. 5 by replacing the term normalized thickness t1 with the term normalized thickness t3.

[0128] The thickness of the piezoelectric layer 11 may be 2p or less.

[0129] In this case, for example, it becomes easier to utilize relatively fast plate waves. As a result, for example, it becomes easier to realize an elastic wave element 1 having a high resonant frequency. For example, an elastic wave element 1 with a pitch p of approximately 1 μm can achieve a resonant frequency of 3 GHz or more or 5 GHz or more. Furthermore, when deriving Figures 3 to 6, simulations were performed assuming such an ultra-high frequency elastic wave element 1, so the effects of various parameter values ​​falling within the ranges shown in Figures 3 to 6 are easily achieved.

[0130] The material of the piezoelectric layer 11 may be lithium tantalate or lithium niobate. Between the piezoelectric layer 11 and the support substrate 7, in a region overlapping with the IDT electrode 19 in a planar perspective view, one or more acoustic films (e.g., an intermediate layer 9 or a multilayer film 39 (a first acoustic film 39 a and a second acoustic film 39 b)) having a different acoustic velocity (and / or acoustic impedance) from that of the piezoelectric layer 11 may be interposed, or a cavity 7 a may be interposed.

[0131] In this case, for example, it becomes easier to confine the energy of the elastic wave in the piezoelectric layer 11, thereby reducing the insertion loss. Furthermore, when deriving Figures 3 to 6, the simulation was performed assuming that the elastic wave element 1 is provided with the intermediate layer 9 (low acoustic velocity film), the multilayer film 39, or the cavity 7a, so the effects of keeping the values ​​of various parameters within the ranges shown in Figures 3 to 6 are easily achieved.

[0132] The technology according to the present disclosure is not limited to the above-described embodiment and may be implemented in various modes.

[0133] For example, the composite substrate may have two layers between the support substrate and the piezoelectric layer: a high acoustic velocity film overlapping the support substrate and a low acoustic velocity film overlapping the high acoustic velocity film. The composite substrate may also have a single high acoustic velocity film between the support substrate and the piezoelectric layer. The composite substrate may have a configuration in which the piezoelectric layer and the support substrate are directly bonded in a region where the IDT electrode fits in a planar perspective. The composite substrate may have only a bonding layer between the piezoelectric layer and the support substrate, the bonding layer having a thickness that has almost no acoustic effect on the elastic waves propagating through the piezoelectric layer. Such a bonding layer may be considered as a layer different from the intermediate layer having a different acoustic velocity (and / or acoustic impedance) from that of the piezoelectric layer described above. The thickness of the bonding layer may be, for example, 0.005λ or less or 0.001λ or less.

[0134] 1... acoustic wave element, 7... supporting substrate, 11... piezoelectric layer, 19... IDT electrode, 27... electrode fingers (of the IDT electrode), 35... first conductor layer (first layer).

Claims

1. A support substrate; a piezoelectric layer located on the support substrate; an IDT electrode located on the piezoelectric layer, the IDT electrode has a first layer made of a first conductive material; The first layer is having a thickness greater than 100 Å; a first layer that is directly overlapped with the piezoelectric layer, or that is overlapped with a metal layer having a thickness of 100 Å or less that is in contact with the first layer and the piezoelectric layer; The pitch of the electrode fingers of the IDT electrode is p (μm), and the thickness (μm) of the first layer is 2p ０．１０１ When the value obtained by dividing by is the normalized thickness t1, The normalized thickness t1 and the sound velocity V1 (m / s) of the bulk longitudinal wave propagating through the first material are expressed by the following formula: 2.14×10 －６ V1-1.16×10 －２ <t1<1.17×10 －５ V1-1.63×10 －２ Fulfill Acoustic wave element.

2. the IDT electrode further comprises a top structure overlying the first layer and constructed of one or more materials different from the first material; when the upper structure has an insulating layer of 150 Å or less forming an upper surface of the IDT electrode, a portion between an upper surface of the first layer and a lower surface of the insulating layer is defined as a second layer, and when the upper structure does not have the insulating layer, a portion between an upper surface of the first layer and an upper surface of the IDT electrode is defined as a second layer, the second layer has a thickness greater than 150 Å; The thickness (μm) of the second layer is 2p ０．１０１ When the value obtained by dividing the thickness by t2 is the normalized thickness, the following formula is obtained: 4.000×10 －６ V1-1.18×10 －２ <t2<2.52×10 －６ 1V1+44.001×110 －２ Fulfill The acoustic wave element according to claim 1 .

3. A support substrate; a piezoelectric layer located on the support substrate; an IDT electrode located on the piezoelectric layer, The IDT electrode is a first layer made of a first conductive material; a top structure overlying the first layer and constructed of one or more materials different from the first material; The first layer is having a thickness greater than 100 Å; a first layer that is directly overlapped with the piezoelectric layer, or that is overlapped with a metal layer having a thickness of 100 Å or less that is in contact with the first layer and the piezoelectric layer; When the upper structure has an insulating layer having a thickness of 150 Å or less forming an upper surface of the IDT electrode, a portion between an upper surface of the first layer and a lower surface of the insulating layer is defined as a second layer, and when the upper structure does not have the insulating layer, a portion between an upper surface of the first layer and an upper surface of the IDT electrode is defined as a second layer, and the second layer has a thickness greater than 150 Å; The pitch of the electrode fingers of the IDT electrode is p (μm), and the thickness (μm) of the second layer is 2p ０．１０１ When the value obtained by dividing the thickness by the thickness t2 is defined as the normalized thickness t2, the normalized thickness t2 and the sound velocity V1 (m / s) of the bulk longitudinal wave propagating through the first material are expressed by the following formula: 4.000×10 －６ V1-1.18×10 －２ <t2<2.52×10 －６ 1V1+44.001×110 －２ Fulfill Acoustic wave element.

4. The average density ρ (g / cm ３ ) and the average sound velocity V2 (m / s) of the bulk longitudinal wave propagating through the second layer are expressed by the following formula: -135.64ρ+4155.6<V2<-2470.1ρ+16872 Fulfill The acoustic wave element according to claim 2 .

5. A support substrate; a piezoelectric layer located on the support substrate; an IDT electrode located on the piezoelectric layer, The IDT electrode is a first layer made of a first conductive material; a top structure overlying the first layer and constructed of one or more materials different from the first material; The first layer is having a thickness greater than 100 Å; a first layer that is directly overlapped with the piezoelectric layer, or that is overlapped with a metal layer having a thickness of 100 Å or less that is in contact with the first layer and the piezoelectric layer; When the upper structure has an insulating layer having a thickness of 150 Å or less forming an upper surface of the IDT electrode, a portion between an upper surface of the first layer and a lower surface of the insulating layer is defined as a second layer, and when the upper structure does not have the insulating layer, a portion between an upper surface of the first layer and an upper surface of the IDT electrode is defined as a second layer, and the second layer has a thickness greater than 150 Å; The average density ρ (g / cm ３ ) and the average sound velocity V2 (m / s) of the bulk longitudinal wave propagating through the second layer are expressed by the following formula: -135.64ρ+4155.6<V2<-2470.1ρ+16872 Fulfill Acoustic wave element.

6. when the IDT electrode has an insulating layer of 150 Å or less forming an upper surface of the IDT electrode, a portion between a lower surface of the first layer and a lower surface of the insulating layer is defined as a third layer, and when the IDT electrode does not have the insulating layer, a portion between a lower surface of the first layer and an upper surface of the IDT electrode is defined as a third layer, the third layer has a thickness greater than 150 Å; The thickness (μm) of the third layer is 2p ０．１０１ When the value obtained by dividing the thickness by t3 is the normalized thickness, the following formula is obtained: 6.91×10 －６ V1-2.34×10 －２ <t3<1.42×10 －５ V1+2.45×10 －２ Fulfill The acoustic wave element according to claim 1 .

7. When the pitch of the electrode fingers of the IDT electrode is p (μm), the thickness of the piezoelectric layer is 2p or less. The acoustic wave element according to claim 1 .

8. the material of the piezoelectric layer is lithium tantalate or lithium niobate, Between the piezoelectric layer and the support substrate, in a region overlapping with the IDT electrode in a planar perspective view, one or more acoustic membranes having a different sound velocity from that of the piezoelectric layer are interposed, or a cavity is interposed. The acoustic wave element according to claim 1 .

9. The Lamb wave of the A1 mode in the piezoelectric layer is utilized. The acoustic wave element according to claim 1 .

10. The thickness shear mode bulk wave in the piezoelectric layer is utilized. The acoustic wave element according to claim 1 .

11. A filter having the acoustic wave element according to any one of claims 1 to 10; an antenna connected to the filter; an integrated circuit device connected to the filter; A communication device having the above configuration.