Elastic wave device and method of manufacturing the same

Abstract

The present invention provides an elastic wave device capable of miniaturization. The elastic wave device (10) includes: a support member (13); a piezoelectric layer (14) having a first main surface (14a) and a second main surface (14b) located on the side of the support member (13); a first IDT electrode (11A) disposed on the first main surface (14a) having a plurality of first electrode fingers (26) and second electrode fingers (27); and a second IDT electrode (11B) disposed on a portion of the second main surface (14b) that does not overlap with the first IDT electrode (11A) in plan view, having a plurality of first electrode fingers (28) and second electrode fingers (29). The thickness of the piezoelectric layer (14) is set as d, and the center-to-center distance between adjacent electrode fingers is set as p. In this case, d / p is 0.5 or less in the first IDT electrode (11A) and the second IDT electrode (11B). It also includes: an insulating film (17) disposed on the second main surface (14b) in a portion that overlaps with the first IDT electrode (11A) when viewed from above; and a wiring electrode (18) that passes through the insulating film (17) in the portion that overlaps with the first IDT electrode (11A) when viewed from above, and is connected to the second IDT electrode (11B).

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Previously, elastic wave devices were widely used in filters for portable telephones, etc. In recent years, elastic wave devices utilizing thickness shear mode bulk waves, as described in Patent Document 1 below, have been proposed. In this elastic wave device, a pair of electrodes are disposed on a piezoelectric layer. The paired electrodes are positioned opposite each other on the piezoelectric layer and connected to different potentials. By applying an alternating voltage between the electrodes, a thickness shear mode bulk wave is excited.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: US Patent No. 10,491,192 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, in elastic wave resonators that utilize the thickness shear mode of bulk waves, the electrode spacing tends to increase, making miniaturization difficult.

[0008] The purpose of this invention is to provide a miniaturized elastic wave device.

[0009] Technical solutions for solving the problem

[0010] The elastic wave device of the present invention comprises: a support member having a support substrate; a piezoelectric layer disposed on the support member having a first main surface located on the support member side and a second main surface facing the first main surface; a first IDT electrode disposed on the first main surface having a plurality of electrode fingers; and a second IDT electrode disposed on a portion of the second main surface that does not overlap with the first IDT electrode in plan view, having a plurality of electrode fingers. The thickness of the piezoelectric layer is defined as d, and the center-to-center distance between adjacent electrode fingers is defined as p. In this case, d / p is 0.5 or less for both the first and second IDT electrodes. The elastic wave device further comprises: an insulating film disposed on a portion of the second main surface that overlaps with the first IDT electrode in plan view; and a wiring electrode passing through the insulating film in the portion overlapping with the first IDT electrode in plan view and connected to the second IDT electrode.

[0011] Invention Effects

[0012] The elastic wave device according to the present invention enables miniaturization. Attached Figure Description

[0013] Figure 1 This is a schematic front sectional view of the elastic wave device according to the first embodiment of the present invention.

[0014] Figure 2 This is a schematic top view of the elastic wave device according to the first embodiment of the present invention.

[0015] Figure 3 yes Figure 2 A schematic cross-sectional view along line II-II.

[0016] Figure 4 This is a schematic top view of the elastic wave device of the first reference example.

[0017] Figure 5 This is a schematic top view of the elastic wave device of the second reference example.

[0018] Figure 6 This is a diagram showing the first model used in a simulation involving the relationship between the parameters and resonant characteristics of the insulating film.

[0019] Figure 7 This is a diagram showing the second model used in a simulation involving the relationship between the parameters and resonant characteristics of the insulating film.

[0020] Figure 8 (a)~ Figure 8 Figure (e) shows the results in the first model where the thickness of the insulating film is set to 1 μm and 1 / Q = 0, where... Figure 8 (a) is a graph showing the impedance-frequency characteristics when the insulating film material is polyethylene and the Young's modulus is 0.91 GPa. Figure 8 (b) is a graph showing the impedance-frequency characteristics when the insulating film material is polystyrene and the Young's modulus is set to 1.39 GPa. Figure 8 (c) is a graph showing the impedance-frequency characteristics when the insulating film material is polycarbonate and the Young's modulus is set to 2.24 GPa. Figure 8 (d) is a graph showing the impedance-frequency characteristics when the insulating film material is polyethylene terephthalate and the Young's modulus is set to 3.44 GPa. Figure 8 (e) is a graph showing the impedance-frequency characteristics when the insulating film material is polyacetal and the Young's modulus is set to 3.58 GPa.

[0021] Figure 9 (a)~ Figure 9 (e) is a graph showing the results in the first model where the insulating film material is polyethylene and 1 / Q = 0, where... Figure 9(a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 9 (b) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 9 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 9 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 9 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0022] Figure 10 (a)~ Figure 10 (e) is a graph showing the results in the first model where the insulating film material is polyethylene and Q = 50, where... Figure 10 (a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 10 (b) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 10 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 10 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 10 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0023] Figure 11 (a)~ Figure 11 (e) is a graph showing the results in the second model where the insulating film material is polyethylene and 1 / Q = 0, where... Figure 11 (a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 11 (b) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 11 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 11 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 11 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0024] Figure 12 (a)~ Figure 12 Figure (e) shows the results in the second model where the insulating film material is polyethylene and Q = 50. Figure 12(a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 12 (b) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 12 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 12 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 12 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0025] Figure 13 (a)~ Figure 13 Figure (e) shows the results in the second model where the thickness of the insulating film is set to 2 μm and Q = 1000. Figure 13 (a) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 1 GPa. Figure 13 (b) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 5 GPa. Figure 13 (c) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 10 GPa. Figure 13 (d) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 15 GPa. Figure 13 (e) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 20 GPa.

[0026] Figure 14 (a)~ Figure 14 (e) is an example illustrating a method for manufacturing an elastic wave device according to the first embodiment of the present invention, up to the second IDT electrode formation step, which is equivalent to... Figure 2 A schematic cross-sectional view of a section along line II-II.

[0027] Figure 15 (a) and Figure 15 (b) illustrates an example of a method for manufacturing an elastic wave device according to the first embodiment of the present invention, up to the sacrificial layer removal step, which is equivalent to... Figure 2 A schematic cross-sectional view of a section along line II-II.

[0028] Figure 16 (a) and Figure 16 (b) illustrates an example of a method for manufacturing an elastic wave device according to the first embodiment of the present invention, up to the wiring electrode formation step, which is equivalent to... Figure 2 A schematic cross-sectional view of a portion of the section along line II.

[0029] Figure 17 This is a simplified top view of the elastic wave device according to the second embodiment of the present invention.

[0030] Figure 18 This is a circuit diagram of the elastic wave device according to the second embodiment of the present invention.

[0031] Figure 19 This is a schematic top view of the elastic wave device of the third reference example.

[0032] Figure 20 (a) is a simplified perspective view showing the appearance of a filter device utilizing a thickness shear mode for bulk waves. Figure 20 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0033] Figure 21 yes Figure 20 A sectional view of the portion along line AA in (a).

[0034] Figure 22 (a) is a schematic front sectional view illustrating the propagation of a Lamb wave in a piezoelectric film of an elastic wave device. Figure 22 (b) is a schematic front sectional view illustrating the thickness shear mode of a bulk wave propagating in a piezoelectric film within a filter device.

[0035] Figure 23 This is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0036] Figure 24 This is a diagram showing the resonant characteristics of a filter device utilizing a thickness shear mode for bulk waves.

[0037] Figure 25 This is a graph showing the relationship between d / p and the relative bandwidth of the resonator when the center-to-center distance between adjacent electrodes is set to p and the thickness of the piezoelectric layer is set to d.

[0038] Figure 26 This is a top view of an elastic wave device that utilizes the thickness shear mode of body waves.

[0039] Figure 27 This is a diagram showing the resonant characteristics of an elastic wave device with stray emissions, representing a reference example.

[0040] Figure 28 This is a graph showing the relationship between the relative bandwidth and the phase rotation of the spur impedance, which is normalized by 180 degrees as the size of the spur.

[0041] Figure 29This is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0042] Figure 30 This is a diagram showing the mapping of the relative bandwidth to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0. Detailed Implementation

[0043] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0044] In addition, it should be noted that the embodiments described in this specification are illustrative and that partial substitutions or combinations of structures can be made between different embodiments.

[0045] Figure 1 This is a schematic front sectional view of the elastic wave device according to the first embodiment of the present invention. Figure 2 This is a schematic top view of the elastic wave device according to the first embodiment. Additionally, Figure 1 yes Figure 2 A schematic cross-sectional view along line II. Figure 2 In the diagram, the electrodes located at the front of the paper are shown by shading. The same applies in the other schematic top views.

[0046] like Figure 1 As shown, the elastic wave device 10 includes a piezoelectric substrate 12, a first IDT electrode 11A, and a second IDT electrode 11B. The piezoelectric substrate 12 includes a support member 13 and a piezoelectric layer 14. In this embodiment, the support member 13 includes a support substrate 16 and an intermediate layer 15. The intermediate layer 15 is disposed on the support substrate 16. The piezoelectric layer 14 is disposed on the intermediate layer 15. However, the support member 13 may also include only the support substrate 16.

[0047] The support member 13 has a first cavity 13c and a second cavity 13d. More specifically, the intermediate layer 15 has a first recess and a second recess. A piezoelectric layer 14 is provided on the intermediate layer 15 to seal the first and second recesses. The first recess is surrounded by the intermediate layer 15 and the piezoelectric layer 14. Thus, the first cavity 13c is formed. Similarly, the second recess is surrounded by the intermediate layer 15 and the piezoelectric layer 14. Thus, the second cavity 13d is formed. Alternatively, the first cavity 13c and the second cavity 13d may be formed as a single cavity.

[0048] As the material for the intermediate layer 15, suitable dielectrics such as silicon oxide or tantalum pentoxide can be used. As the material for the support substrate 16, semiconductors such as silicon or suitable ceramics can be used. Furthermore, the support member 13 does not necessarily need to have the intermediate layer 15. In this case, it is sufficient that the support substrate 16 has a first recess and a second recess, etc.

[0049] The piezoelectric layer 14 has a first main surface 14a and a second main surface 14b. The first main surface 14a and the second main surface 14b are opposite to each other. The first main surface 14a is the main surface on the side of the support member 13. In this embodiment, the piezoelectric layer 14 is a lithium niobate layer. More specifically, the piezoelectric layer 14 is a LiNbO3 layer. However, the piezoelectric layer 14 may also be, for example, a lithium tantalate layer such as a LiTaO3 layer.

[0050] A first IDT electrode 11A is provided on the first main surface 14a of the piezoelectric layer 14. The first IDT electrode 11A is disposed within the first cavity 13c. On the other hand, a second IDT electrode 11b is provided on the second main surface 14b. The second IDT electrode 11b overlaps with the second cavity 13d when viewed from above. More specifically, the second IDT electrode 11b is disposed in the portion of the second main surface 14b that does not overlap with the first IDT electrode 11A when viewed from above. In this specification, "viewing from above" means from a perspective equivalent to... Figure 1 Observe from the top direction.

[0051] An elastic wave resonator 21A is formed by providing a first IDT electrode 11A on the first main surface 14a of the piezoelectric layer 14 in the piezoelectric substrate 12. Similarly, an elastic wave resonator 21B is formed by providing a second IDT electrode 11b on the second main surface 14b of the piezoelectric layer 14. Thus, the elastic wave device 10 of this embodiment includes two elastic wave resonators. The elastic wave device 10 may also be part of a filter device, for example. However, the elastic wave device of the present invention may be a filter device including three or more elastic wave resonators, or it may be a composite filter device such as a duplexer or multiplexer.

[0052] Each elastic wave resonator in the elastic wave device 10 is configured to generate a volume wave using a thickness shear mode, such as a first-order thickness shear mode. More specifically, the first IDT electrode 11A has a plurality of first electrode fingers 26 and a plurality of second electrode fingers 27. For example... Figure 2As shown, multiple first electrode fingers 26 and multiple second electrode fingers 27 are interleaved with each other. Similarly, the second IDT electrode 11b has multiple first electrode fingers 28 and multiple second electrode fingers 29. The first IDT electrode 11A and the second IDT electrode 11b may comprise a single-layer metal film or may comprise a stacked metal film. Hereinafter, the multiple first electrode fingers and the multiple second electrode fingers will sometimes be collectively referred to as electrode fingers.

[0053] In each of the first IDT electrode 11A and the second IDT electrode 11b, the thickness of the piezoelectric layer 14 is set as d, and the center-to-center distance between adjacent electrodes is set as p. In this case, d / p is 0.5 or less. Therefore, in each elastic wave resonator, a bulk wave with a thickness shear mode can be appropriately excited. Furthermore, details of the structure of the IDT electrodes in this invention will be described later.

[0054] Figure 3 yes Figure 2 A schematic cross-sectional view along line II-II.

[0055] A lead-out wiring 25 is provided on the first main surface 14a of the piezoelectric layer 14. The lead-out wiring 25 is connected to the first IDT electrode 11A. A plurality of through holes 14c are provided in the piezoelectric layer 14. One of the plurality of through holes 14c leads to the lead-out wiring 25. A connection electrode 23 is provided throughout the through hole 14c and the first main surface 14a. One end of the connection electrode 23 is connected to the lead-out wiring 25. Alternatively, the first IDT electrode 11A may also be connected to other components, for example, through wiring provided on the second main surface 14b. In this way, the first IDT electrode 11A does not necessarily have to be connected to the connection electrode 23 provided on the first main surface 14a.

[0056] Return to Figure 1 An insulating film 17 is provided on the second main surface 14b of the piezoelectric layer 14. The insulating film 17 is, for example, a resin film. The insulating film 17 overlaps with the first IDT electrode 11A when viewed from above. A wiring electrode 18 is provided on the second main surface 14b, passing through the insulating film 17. The wiring electrode 18 is connected to the second IDT electrode 11B.

[0057] The feature of this embodiment is that, when viewed from above, the wiring electrode 18 passes through the insulating film 17 in the portion overlapping with the first IDT electrode 11A and is connected to the second IDT electrode 11b. This enables miniaturization of the elastic wave device 10. This will be described below using a first reference example and a second reference example.

[0058] exist Figure 4In the first reference example shown, the insulating film 17 is not provided. Therefore, all of the wiring electrodes 18 are directly disposed on the second main surface 14b of the piezoelectric layer 14. Moreover, in top view, the wiring electrodes 18 overlap with the first IDT electrode 11A. In this case, the electrical characteristics of the elastic wave device are significantly degraded.

[0059] On the other hand, Figure 5 In the second reference example shown, the insulating film 17 is not provided, and the wiring electrode 108 does not overlap with the first IDT electrode 11A when viewed from above. Because the wiring electrode 108 bypasses the portion where the first IDT electrode 11A is provided, the elastic wave device becomes larger.

[0060] Compared to these reference examples, in Figure 2 In the embodiment shown, the wiring electrode 18 passes through the insulating film 17 in the portion overlapping with the first IDT electrode 11A and connects to the second IDT electrode 11b. Therefore, even without the wiring electrode 18 bypassing the portion where the first IDT electrode 11A is located, degradation of the electrical characteristics of the elastic wave device 10 can be suppressed. Thus, the area of ​​the wiring electrode 18 can be reduced without causing significant degradation of the electrical characteristics of the elastic wave device 10, enabling the elastic wave device 10 to be miniaturized.

[0061] Here, resins suitable for use in insulating film 17 were investigated. Examples of resins and their physical properties are shown in Table 1 below.

[0062] [Table 1]

[0063]

[0064] Simulations were performed to investigate the relationship between the parameters of the resin used for the insulating film 17 and the impedance-frequency characteristics of the elastic wave resonator 21A containing the first IDT electrode 11A. Furthermore, a first model and a second model were used as simulation models.

[0065] The first model is as follows, i.e., as Figure 6 As shown, an insulating film 17 is provided on the second main surface 14b of the piezoelectric layer 14, such that it overlaps with the first IDT electrode 11A when viewed from above, and no wiring electrode 18 is provided. Figure 7 As shown, the second model is the same as the first embodiment. Specifically, the second model is one in which an insulating film 17 is provided on the second main surface 14b of the piezoelectric layer 14, such that it overlaps with the first IDT electrode 11A when viewed from above, and a wiring electrode 18 is provided on the insulating film 17. This wiring electrode 18 overlaps with the first IDT electrode 11A when viewed from above.

[0066] In Model 1, simulations were performed for cases where the Young's modulus of the insulating film 17 was different, and for cases where the thickness was different. Furthermore, in these simulations, the Q value of the insulating film 17 was not considered, and the value of 1 / Q was set to 0. That is, the Q value was set to infinity. Furthermore, simulations were performed for cases where the Q value of the insulating film 17 was set to 50, and the thickness was different. The design parameters in Model 1 are as follows. Additionally, hereinafter, the term "electrode finger spacing" refers to the center-to-center distance between adjacent electrode fingers.

[0067] Piezoelectric layer: The material is LiNbO3, and the thickness is 0.4 μm.

[0068] Electrode reference: Material is Al, thickness is 0.5μm

[0069] Electrode finger spacing: 3.75μm

[0070] Duty cycle: 0.27

[0071] Figure 8 (a)~ Figure 8 (e) shows the results in the first model where the thickness of the insulating film is set to 1 μm and 1 / Q = 0. Figure 8 (a) is a graph showing the impedance-frequency characteristics when the insulating film is made of polyethylene and the Young's modulus is set to 0.91 GPa. Figure 8 (b) is a graph showing the impedance-frequency characteristics when the insulating film is made of polystyrene and the Young's modulus is set to 1.39 GPa. Figure 8 (c) is a graph showing the impedance-frequency characteristics when the insulating film material is polycarbonate and the Young's modulus is set to 2.24 GPa. Figure 8 (d) is a graph showing the impedance-frequency characteristics when the insulating film material is polyethylene terephthalate and the Young's modulus is set to 3.44 GPa. Figure 8 (e) is a graph showing the impedance-frequency characteristics when the insulating film material is polyacetal and the Young's modulus is set to 3.58 GPa.

[0072] In addition, Figure 8 (a)~ Figure 8 In (b), the results without the insulating film 17 are also shown. The results without the insulating film 17 are shown by dashed lines. The same dashed waveforms are also shown in the following figures showing the results of simulations based on the first model and the second model.

[0073] like Figure 8 (a)~ Figure 8 As shown in (e), it can be seen that the lower the Young's modulus of the insulating film 17, the less likely it is to generate unwanted waves in the impedance frequency characteristics.

[0074] Figure 9 (a)~ Figure 9 (e) shows the results in the first model where the material of the insulating film is polyethylene and 1 / Q = 0. Figure 9 (a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 9 (b) is a graph showing the impedance frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 9 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 9 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 9 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0075] like Figure 9 (a)~ Figure 9 As shown in (e), the resonance characteristics are stable when the thickness of the insulating film 17 is greater than 2 μm.

[0076] Figure 10 (a)~ Figure 10 (e) shows the results in the first model where the material of the insulating film is polyethylene and Q = 50. Figure 10 (a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 10 (b) is a graph showing the impedance frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 10 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 10 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 10 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0077] Figure 9 (a)~ Figure 9 The result shown in (e) is the result without considering the Q value. Figure 10 (a)~ Figure 10 The result shown in (e) is the result considering the Q value. When the Q value is considered, the generation of unwanted waves becomes less noticeable. Furthermore, as... Figure 10 (a)~ Figure 10 As shown in (e), it can be seen that when the thickness of the insulating film 17 is more than 1.5 μm and less than 3 μm, the impedance difference dZ at the resonant point and the anti-resonant point can be relatively large, up to 55 dB.

[0078] In the second model, simulations were performed with and without considering the Q-value of the insulating film 17, with varying thicknesses. When considering the Q-value, it was set to 50. Furthermore, simulations were performed with the Q-value of the insulating film 17 set to 1000 and with varying Young's moduli. The design parameters in the second model were the same as in the first model, except for the parameters of the wiring electrode 18. Additionally, the boundary conditions for the wiring electrode 18 were calculated using the signal potential.

[0079] Wiring electrode: Material is Al, thickness is 2μm

[0080] Figure 11 (a)~ Figure 11 (e) shows the results in the second model where the material of the insulating film is polyethylene and 1 / Q = 0. Figure 11 (a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 11 (b) is a graph showing the impedance frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 11 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 11 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 11 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0081] like Figure 11 (a)~ Figure 11 As shown in (e), the resonance characteristics are stable when the thickness of the insulating film 17 is 2 μm or more. However, depending on the thickness of the insulating film 17, the relative bandwidth can sometimes become narrower due to the influence of the parallel capacitance. Here, it is preferable that the relative permittivity of the insulating film 17 is less than 5. This reduces the influence of the parallel capacitance and prevents the relative bandwidth from becoming too narrow.

[0082] Figure 12 (a)~ Figure 12 (e) shows the results in the second model where the material of the insulating film is polyethylene and Q = 50. Figure 12 (a) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 0.5 μm. Figure 12 (b) is a graph showing the impedance frequency characteristics when the thickness of the insulating film is set to 1 μm. Figure 12 (c) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 1.5 μm. Figure 12 (d) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 2 μm. Figure 12 (e) is a graph showing the impedance-frequency characteristics when the thickness of the insulating film is set to 3 μm.

[0083] like Figure 12 (a)~ Figure 12 As shown in (e), it can be seen that even when considering the Q value, the resonance characteristics are stable only when the thickness of the insulating film 17 is 2 μm or more. Therefore, the thickness of the insulating film 17 is preferably 2 μm or more.

[0084] Figure 13 (a)~ Figure 13 (e) shows the results in the second model where the thickness of the insulating film is set to 2 μm and Q = 1000. Figure 13 (a) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 1 GPa. Figure 13 (b) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 5 GPa. Figure 13 (c) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 10 GPa. Figure 13 (d) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 15 GPa. Figure 13 (e) is a graph showing the impedance-frequency characteristics when the Young's modulus of the insulating film is set to 20 GPa.

[0085] like Figure 13 (a)~ Figure 13 As shown in (e), the resonance characteristics are stable when the Young's modulus is below 10 GPa. Furthermore, it is known that the smaller the Young's modulus, the greater the impedance difference dZ at the resonant and anti-resonant points. The Young's modulus is preferably below 10 GPa, and more preferably below 5 GPa. This stabilizes the resonance characteristics and increases the impedance difference dZ.

[0086] Hereinafter, an example of a method for manufacturing an elastic wave device according to the first embodiment will be described.

[0087] Figure 14 (a)~ Figure 14 (e) is an example illustrating the manufacturing method of the elastic wave device according to the first embodiment, up to the second IDT electrode formation step, which is equivalent to... Figure 2 A schematic cross-sectional view of a section along line II-II. Figure 15 (a) and Figure 15(b) illustrates an example of a method for manufacturing an elastic wave device according to the first embodiment, up to the sacrificial layer removal step, which is equivalent to... Figure 2 A schematic cross-sectional view of a section along line II-II. Figure 16 (a) and Figure 16 (b) illustrates an example of a method for manufacturing an elastic wave device according to the first embodiment, up to the wiring electrode formation step, which is equivalent to... Figure 2 A schematic cross-sectional view of a portion of the section along line II.

[0088] like Figure 14 As shown in (a), a piezoelectric substrate 24 is prepared. Furthermore, the piezoelectric substrate 24 is the piezoelectric layer in this invention. The piezoelectric substrate 24 has a first main surface 24a and a second main surface 24b. The first main surface 24a and the second main surface 24b are opposite to each other. A first IDT electrode 11A and a lead-out wiring 25 are formed on the first main surface 24a. At this time, the lead-out wiring 25 is configured to be connected to the first IDT electrode 11A. The first IDT electrode 11A and the lead-out wiring 25 can be formed, for example, by sputtering or vacuum evaporation.

[0089] Next, as Figure 14 As shown in (b), a first sacrificial layer 22A and a second sacrificial layer 22B are formed on the first main surface 24a of the piezoelectric substrate 24. The first sacrificial layer 22A is formed to cover at least a portion of the first IDT electrode 11A. Materials for the first sacrificial layer 22A and the second sacrificial layer 22B can be, for example, ZnO, SiO2, Cu, or resin.

[0090] Next, as Figure 14 As shown in (c), an intermediate layer 15 is formed on the first main surface 24a of the piezoelectric substrate 24, covering the first sacrificial layer 22A and the second sacrificial layer 22B. The intermediate layer 15 can be formed, for example, by sputtering or vacuum evaporation. Next, the intermediate layer 15 is planarized. During the planarization of the intermediate layer 15, for example, grinding or CMP (Chemical Mechanical Polishing) can be used.

[0091] Next, as Figure 14As shown in (d), the support substrate 16 is bonded to the main surface of the intermediate layer 15 opposite to the piezoelectric substrate 24. This results in a laminate comprising the piezoelectric substrate 24 as a piezoelectric layer and the support substrate 16. Alternatively, without forming the intermediate layer 15, a recess can be provided in the support substrate 16, and then the piezoelectric substrate 24 and the support substrate 16 can be bonded such that the first IDT electrode 11 is located within the recess. In this case, direct bonding, plasma-activated bonding, atomic diffusion bonding, etc., can be used.

[0092] Next, the thickness of the piezoelectric substrate 24 is adjusted. More specifically, the thickness of the piezoelectric substrate 24 is reduced by grinding or polishing the main surface side of the piezoelectric substrate 24 that is not bonded to the support substrate 16. Furthermore, at this time, the thickness d is adjusted such that, with the thickness of the piezoelectric layer set to d and the center-to-center distance between adjacent electrodes of the first IDT electrode 11A set to p, d / p becomes 0.5 or less. The thickness of the piezoelectric substrate 24 can be adjusted, for example, by using grinding, CMP, ion chipping, or etching. Thus, as... Figure 14 As shown in (e), piezoelectric layer 14 is obtained.

[0093] Next, a second IDT electrode 11b is formed on the second main surface 14b of the piezoelectric layer 14. More specifically, the second IDT electrode 11b is formed at a position on the second main surface 14b that does not overlap with the first IDT electrode 11A when viewed from above. The second IDT electrode 11b is formed such that at least a portion of the second IDT electrode 11b overlaps with the second sacrificial layer 22B when viewed from above. At this time, the second IDT electrode 11b is formed such that, with the thickness of the piezoelectric layer 14 set to d and the center-to-center distance between adjacent electrode fingers of the second IDT electrode 11b set to p, d / p becomes 0.5 or less. The second IDT electrode 11B can be formed, for example, by sputtering or vacuum evaporation.

[0094] Next, as Figure 15 As shown in (a), a plurality of through-holes 14c are provided in the piezoelectric layer 14. More specifically, through-holes 14c are provided to reach the lead-out wiring 25, to reach the first sacrificial layer 22A, and to reach the second sacrificial layer 22B. The through-holes 14c can be formed, for example, by a method such as RIE (Reactive Ion Etching). Next, the first sacrificial layer 22A and the second sacrificial layer 22B are removed using the through-holes 14c reaching the first sacrificial layer 22A and the second sacrificial layer 22B. More specifically, the first sacrificial layer 22A and the second sacrificial layer 22B are removed from each recess of the intermediate layer 15 by allowing etchant to flow in from the through-holes 14c. Thus, as Figure 15As shown in (b), a first cavity 13c and a second cavity 13d are formed.

[0095] Next, as Figure 16 As shown in (a), an insulating film 17 is formed on the second main surface 14b of the piezoelectric layer 14. At this time, the insulating film 17 is provided in the portion of the second main surface 14b that overlaps with the first IDT electrode 11A when viewed from above. Next, as... Figure 16 As shown in (b), a wiring electrode 18 is provided on the second main surface 14b of the piezoelectric layer 14. At this time, the wiring electrode 18 is configured to be connected to the second IDT electrode 11B, and is configured to pass through the insulating film 17 in the portion that overlaps with the first IDT electrode 11A when viewed from above.

[0096] Next, a through hole 14c is provided within the aforementioned lead-out wiring 25. Figure 3 The connecting electrode 23 shown is connected to the lead-out wiring 25. Through the above, the elastic wave device 10 is obtained.

[0097] Furthermore, as described above, the elastic wave device of the present invention can also be a filter device, for example. The filter device only needs to include an elastic wave resonator 21A having a first IDT electrode 11A and an elastic wave resonator 21B having a second IDT electrode 11b. Hereinafter, an example of an elastic wave device being a filter device is shown.

[0098] Figure 17 This is a simplified top view of the elastic wave device according to the second embodiment. Figure 18 This is a circuit diagram of the elastic wave device according to the second embodiment. Figure 17 In the diagram, each resonator is shown by adding two diagonals to a rectangle.

[0099] like Figure 17 as well as Figure 18 As shown, the elastic wave device 30 in this embodiment is a trapezoidal filter. The elastic wave device 30 has multiple series arm resonators and multiple parallel arm resonators. All the parallel arm resonators and all the series arm resonators in the elastic wave device 30 are configured as elastic wave resonators capable of utilizing body waves in thickness shear mode.

[0100] In this embodiment, all series arm resonators and all parallel arm resonators share a piezoelectric substrate 12. The IDT electrode of all parallel arm resonators is the first IDT electrode in this invention. For example... Figure 17As shown, the first IDT electrode of all the parallel arm resonators is disposed on the first main surface 14a of the piezoelectric layer 14. The multiple parallel arm resonators are specifically parallel arm resonators P31a, P31b, P31c, P31d, P32a, P32b, P32c, and P32d.

[0101] The IDT electrodes of all series arm resonators are the second IDT electrodes of this invention. The second IDT electrodes of all series arm resonators are disposed on the second main surface 14b of the piezoelectric layer 14. Specifically, the multiple series arm resonators are series arm resonators S31a, S31b, S32, S33a, and S33b. Furthermore, each parallel arm resonator is appropriately connected to each series arm resonator via lead-out wiring and connecting electrodes.

[0102] like Figure 17 As shown, in the portion of the second main surface 14b of the piezoelectric layer 14 that overlaps with each of the parallel arm resonators when viewed from above, a plurality of insulating films 17 are provided. When viewed from above, the wiring electrode 18 passes through the insulating film 17 in the portion that overlaps with the first IDT electrode 11A and is connected to the second IDT electrode 11b.

[0103] On the other hand, Figure 19 In the third reference example shown, all the parallel arm resonators are formed on the second main surface 14b of the piezoelectric layer 14. The elastic wave device in the third reference example does not have the insulating film 17. Furthermore, the circuit structure of the third reference example is the same as that of this embodiment. Figure 19 As shown, in the third reference example, the winding area of ​​wiring electrodes 108A, 108B, and 108C is increased. Therefore, a comparison between this embodiment and the third reference example clearly shows that in this embodiment, miniaturization of the elastic wave device 30 can be promoted.

[0104] Furthermore, such as Figure 17 As shown, the elastic wave device 30 includes a connecting electrode 23 that connects the first IDT electrodes to each other. The connecting electrode 23 passes through the insulating film 17 and connects the first IDT electrodes to each other. More specifically, in top view, the connecting electrode 23 passes through the portion overlapping with the first IDT electrodes. This allows for further miniaturization of the elastic wave device 30.

[0105] Furthermore, the circuit structure of the elastic wave device 30 is as follows. (For example...) Figure 18As shown, the elastic wave device 30 has an input terminal 32A and an output terminal 32B. Between the input terminal 32A and the series arm resonator S32, series arm resonators S31a and S31b are connected in parallel. Furthermore, series arm resonators S31a and S31b are segmented resonators, which are formed by paralleling and dividing a single series arm resonator. Between the series arm resonator S32 and the output terminal 32B, series arm resonators S33a and S33b are connected in parallel. Series arm resonators S33a and S33b are segmented resonators, which are formed by paralleling and dividing a single series arm resonator.

[0106] Between the connection point between series arm resonators S31a, S31b, and S32 and the ground potential, parallel arm resonators P31a, P31b, P31c, and P31d are connected in parallel. Parallel arm resonators P31a, P31b, P31c, and P31d are segmented resonators formed by paralleling a single parallel arm resonator. Between the connection point between series arm resonators S32, S33a, and S33b and the ground potential, parallel arm resonators P32a, P32b, P32c, and P32d are connected in parallel. Parallel arm resonators P32a, P32b, P32c, and P32d are split resonators that are formed by paralleling a single parallel arm resonator.

[0107] Furthermore, the circuit structure of the elastic wave device 30 is not limited to the circuit structure described above. The elastic wave device 30 may also omit the segmented resonator. The elastic wave device 30 may also include a resonator without a first IDT electrode and a second IDT electrode. The elastic wave device 30 only needs to include at least one elastic wave resonator with a first IDT electrode and at least one elastic wave resonator with a second IDT electrode.

[0108] The details of the elastic wave device utilizing the thickness shear mode for bulk waves are described below. The first IDT electrode and the second IDT electrode described above each have the structure of the IDT electrode described later. The insulating layer described below corresponds to the intermediate layer described above, and the support member corresponds to the support substrate described above.

[0109] Figure 20 (a) is a simplified three-dimensional diagram showing the appearance of an elastic wave device utilizing a thickness shear mode for volume waves. Figure 20 (b) is a top view showing the electrode structure on the piezoelectric layer. Figure 21 yes Figure 20 A sectional view of the portion along line AA in (a).

[0110] The elastic wave device 1 has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. The LiNbO3 and LiTaO3 are cut at a Z-angle, but can also be rotary cut at a Y-angle or X-angle. The thickness of the piezoelectric layer 2 is not particularly limited, but for effectively exciting the thickness shear mode, it is preferably 40 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less. The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first main surface 2a. Here, electrode 3 is an example of a "first electrode," and electrode 4 is an example of a "second electrode." Figure 20 (a) and Figure 20 In (b), multiple electrodes 3 are connected to the first busbar 5. Multiple electrodes 4 are connected to the second busbar 6. The multiple electrodes 3 and multiple electrodes 4 are interleaved and interlocked. Electrodes 3 and 4 have a rectangular shape and a length direction. Electrodes 3 and adjacent electrodes 4 are opposite each other in a direction orthogonal to this length direction. The length directions of electrodes 3 and 4, as well as the directions orthogonal to the length directions of electrodes 3 and 4, are all directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that electrodes 3 and adjacent electrodes 4 are opposite each other in a direction that intersects the thickness direction of the piezoelectric layer 2. Furthermore, the length directions of electrodes 3 and 4 can also be... Figure 20 (a) and Figure 20 The directions shown in (b) that are orthogonal to the length directions of electrodes 3 and 4 are reversed. That is, in Figure 20 (a) and Figure 20 In (b), electrodes 3 and 4 can also extend in the direction in which the first busbar 5 and the second busbar 6 extend. In this case, the first busbar 5 and the second busbar 6 are in... Figure 20 (a) and Figure 20In (b), the electrodes extend in the direction in which electrodes 3 and 4 extend. Furthermore, multiple pairs of adjacent configurations of electrodes 3 connected to one potential and electrodes 4 connected to another potential are provided in a direction orthogonal to the length direction of the electrodes 3 and 4. Here, "adjacent to electrodes 3 and 4" does not mean that electrodes 3 and 4 are arranged in direct contact, but rather that electrodes 3 and 4 are arranged with a gap between them. Furthermore, when electrodes 3 and 4 are adjacent, no electrodes connected to signal electrodes or ground electrodes, including other electrodes 3 and 4, are arranged between electrodes 3 and 4. The number of pairs does not need to be an integer; it can be 1.5 pairs, 2.5 pairs, etc. The center-to-center distance (i.e., spacing) between electrodes 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the width of electrodes 3 and 4 (i.e., the dimension in the opposing direction of electrodes 3 and 4) is preferably in the range of 50 nm or more and 1000 nm or less, more preferably in the range of 150 nm or more and 1000 nm or less. Furthermore, the so-called center-to-center distance between electrodes 3 and 4 is the distance connecting the center of the dimension (width dimension) of electrode 3 in the direction orthogonal to the length direction of electrode 3 and the center of the dimension (width dimension) of electrode 4 in the direction orthogonal to the length direction of electrode 4.

[0111] Furthermore, in the elastic wave device 1, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of electrodes 3 and 4 becomes the direction orthogonal to the polarization direction of piezoelectric layer 2. This is not limited to cases where a piezoelectric material with a different cut angle is used as piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal; it can also be approximately orthogonal (the angle between the direction orthogonal to the length direction of electrodes 3 and 4 and the polarization direction is, for example, within the range of 90° ± 10°).

[0112] On the second main surface 2b side of the piezoelectric layer 2, a support member 8 is stacked with an insulating layer 7 in between. The insulating layer 7 and the support member 8 have a frame-like shape, such as... Figure 21 As shown, it has through holes 7a and 8a. This forms a cavity 9. The cavity 9 is provided so as not to interfere with the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support member 8 is stacked on the second main surface 2b with the insulating layer 7 in a position that does not overlap with the portion where at least one pair of electrodes 3 and 4 are provided. Alternatively, the insulating layer 7 may not be provided. Therefore, the support member 8 can be stacked directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

[0113] The insulating layer 7 comprises silicon oxide. However, in addition to silicon oxide, suitable insulating materials such as silicon oxynitride and bauxite can also be used. The support member 8 comprises Si. The orientation of the facets on the piezoelectric layer 2 side of Si can be (100), (110), or (111). The Si constituting the support member 8 is preferably a high-resistivity material with a resistivity of 4kΩ or higher. However, suitable insulating materials or semiconductor materials can also be used to construct the support member 8.

[0114] For example, materials used as supporting components 8 can include piezoelectric materials such as alumina, lithium tantalate, lithium niobate, and quartz; bauxite, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and magnesium olivine; dielectric materials such as diamond and glass; and semiconductor materials such as gallium nitride.

[0115] The aforementioned electrodes 3 and 4, as well as the first busbar 5 and the second busbar 6, comprise suitable metals or alloys such as Al or AlCu alloys. In this embodiment, electrodes 3 and 4, as well as the first busbar 5 and the second busbar 6, have a structure in which an Al film is stacked on a Ti film. Alternatively, a close-fitting layer other than a Ti film may also be used.

[0116] During driving, an alternating current voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an alternating current voltage is applied between the first busbar 5 and the second busbar 6. This enables the resonant characteristics of a bulk wave utilizing the thickness shear mode excited in the piezoelectric layer 2. Furthermore, in the elastic wave device 1, the thickness of the piezoelectric layer 2 is set as d, and the center-to-center distance between any two adjacent electrodes 3 and 4 in the plurality of pairs of electrodes 3 and 4 is set as p. In this case, d / p is set to 0.5 or less. Therefore, the aforementioned thickness shear mode bulk wave can be effectively excited, and good resonant characteristics can be obtained. More preferably, d / p is 0.24 or less, in which case even better resonant characteristics can be obtained.

[0117] In the elastic wave device 1, the above-described structure ensures that even if miniaturization is desired by reducing the number of electrode pairs 3 and 4, a decrease in the Q value is not easily observed. This is because even reducing the number of electrode fingers in the reflectors on both sides results in minimal propagation loss. Furthermore, the reduction in the number of electrode fingers is achieved through the utilization of a volume wave in a thickness shear mode. (Refer to...) Figure 22 (a) and Figure 22 (b) explains the difference between the Ram wave used in the elastic wave device and the bulk wave of the thickness shear mode described above.

[0118] Figure 22(a) is a schematic front sectional view illustrating the propagation of a Lamb wave in the piezoelectric film of an elastic wave device as described in Japanese Patent Publication No. 2012-257019. Here, the wave propagates in the piezoelectric film 201 as indicated by the arrow. In the piezoelectric film 201, a first main surface 201a and a second main surface 201b face each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z-direction. The X-direction is the direction in which the electrode fingers of the IDT electrodes are arranged. Figure 22 As shown in (a), if it is a Lamb wave, the wave propagates in the X direction as shown. Because it is a plate wave, although the piezoelectric film 201 vibrates as a whole, the wave propagates in the X direction, thus a resonant characteristic is obtained by placing reflectors on both sides. Therefore, wave propagation loss occurs, and the Q value decreases in the case of miniaturization, that is, in the case of reducing the number of electrode fingers.

[0119] In contrast, such as Figure 22 As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction, so the wave propagates and resonates approximately in the direction connecting the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2 (i.e., the Z direction). That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained through the propagation of the wave in this Z-direction, propagation loss is not easily generated even if the number of electrode fingers of the reflector is reduced. Furthermore, even if the number of electrode pairs including electrodes 3 and 4 is reduced in order to promote miniaturization, the Q value is not easily decreased.

[0120] In addition, such as Figure 23 As shown, the amplitude direction of the bulk wave in the thickness shear mode becomes opposite in the first region 451 and the second region 452 contained in the excitation region C of the piezoelectric layer 2. Figure 23 The diagram schematically illustrates a bulk wave when a voltage higher than that applied to electrode 4 is applied between electrode 3 and electrode 4. The first region 451 is the region between the imaginary plane VP1 and the first main surface 2a in the excitation region C. This imaginary plane VP1 is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts. The second region 452 is the region between the imaginary plane VP1 and the second main surface 2b in the excitation region C.

[0121] As described above, the elastic wave device 1 is provided with at least one pair of electrodes, including electrodes 3 and 4. However, since the wave is not propagated in the X direction, the number of electrode pairs including electrodes 3 and 4 does not need to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0122] For example, electrode 3 is an electrode connected to the signal potential, and electrode 4 is an electrode connected to the ground potential. However, it is also possible that electrode 3 is connected to the ground potential, and electrode 4 is connected to the signal potential. In this embodiment, as described above, at least one pair of electrodes is either an electrode connected to the signal potential or an electrode connected to the ground potential, and no floating electrode is provided.

[0123] Figure 24 It is shown Figure 21 The diagram shows the resonant characteristics of the elastic wave device. Furthermore, the design parameters for the elastic wave device 1 with these resonant characteristics are as follows.

[0124] Piezoelectric layer 2: LiNbO3 with Euler angles of (0°, 0°, 90°) and a thickness of 400 nm.

[0125] When viewed in a direction orthogonal to the length direction of electrodes 3 and 4, the length of the overlapping region of electrodes 3 and 4 (i.e., the excitation region C) is 40 μm, the number of electrode pairs containing electrodes 3 and 4 is 21 pairs, the center distance between electrodes is 3 μm, the width of electrodes 3 and 4 is 500 nm, and d / p is 0.133.

[0126] Insulating layer 7: Silicon oxide film with a thickness of 1 μm.

[0127] Supporting component 8: Si.

[0128] In addition, the length of the so-called excitation region C is the dimension of the excitation region C along the length direction of electrodes 3 and 4.

[0129] In this embodiment, the distance between the electrodes of the electrode pairs including electrodes 3 and 4 is set to be equal in all pairs. That is, electrodes 3 and 4 are arranged at equal intervals.

[0130] according to Figure 24 It is clear that, despite the absence of a reflector, a good resonant characteristic with a relative bandwidth of 12.5% ​​was still achieved.

[0131] Furthermore, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between the electrodes of electrode 3 and electrode 4 is set to p, as described above, in this embodiment, d / p is 0.5 or less, more preferably 0.24 or less. (Refer to...) Figure 25 This needs to be explained.

[0132] With obtained Figure 24 Similarly, the elastic wave device with the resonant characteristics shown is obtained by changing d / p, thus obtaining multiple elastic wave devices. Figure 25 This is a graph showing the relationship between d / p and the relative bandwidth of the resonator as an elastic wave device.

[0133] according to Figure 25It is clear that if d / p > 0.5, even with adjustments to d / p, the relative bandwidth will be less than 5%. In contrast, when d / p ≤ 0.5, by varying d / p within this range, the relative bandwidth can be set to 5% or more, meaning a resonator with a high coupling coefficient can be constructed. Furthermore, when d / p is below 0.24, the relative bandwidth can be increased to 7% or more. In addition, by adjusting d / p within this range, a resonator with an even wider relative bandwidth can be obtained, achieving a resonator with a higher coupling coefficient. Therefore, it can be seen that by setting d / p to 0.5 or less, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear mode of bulk waves can be constructed.

[0134] Figure 26 This is a top view of an elastic wave device utilizing a thickness shear mode for bulk waves. In the elastic wave device 80, a pair of electrodes, having electrodes 3 and 4, are provided on the first main surface 2a of the piezoelectric layer 2. Furthermore, Figure 26 K in the figure represents the cross width. As mentioned earlier, in the elastic wave device of the present invention, the number of electrode pairs can also be one. Even in this case, as long as the above-mentioned d / p is 0.5 or less, the thickness shear mode of the bulk wave can be effectively excited.

[0135] In the elastic wave device 1, preferably, among the plurality of electrodes 3, 4, the metallization ratio MR of any adjacent electrodes 3, 4 relative to the excitation region C preferably satisfies MR ≤ 1.75(d / p) + 0.075, where the excitation region C is the region where the aforementioned adjacent electrodes 3, 4 overlap when viewed in opposite directions. In this case, stray emissions can be effectively reduced. (Refer to...) Figure 27 as well as Figure 28 This needs to be explained. Figure 27 This is a reference diagram illustrating an example of the resonant characteristics of the aforementioned elastic wave device 1. Strays, as indicated by arrow B, appear between the resonant frequency and the anti-resonant frequency. Furthermore, d / p is set to 0.08, and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). Additionally, the aforementioned metallization ratio is set to MR = 0.35.

[0136] Reference Figure 20 (b) Explains the metallization ratio MR. Figure 20In the electrode configuration of (b), considering only a pair of electrodes 3 and 4, it is assumed that only this pair of electrodes 3 and 4 are provided. In this case, the portion enclosed by the dashed line is called the excitation region C. The excitation region C is the region where electrodes 3 and 4 overlap when viewed from a direction orthogonal to the length direction of electrodes 3 and 4 (i.e., the opposing direction), the region where electrodes 3 and 4 overlap, the region where electrodes 4 overlap with electrodes 3, and the region between electrodes 3 and 4. Furthermore, the ratio of the area of ​​electrodes 3 and 4 within the excitation region C to the area of ​​the excitation region C is called the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0137] In addition, when multiple pairs of electrodes are provided, the ratio of the total area of ​​the metallized portion contained in the entire excitation region to the total area of ​​the excitation region can be used as MR.

[0138] Figure 28 This is a graph showing the relationship between the relative bandwidth and the phase rotation of the stray impedance, which is normalized by 180 degrees, when multiple elastic wave resonators are constructed according to this embodiment. Furthermore, the relative bandwidth has been adjusted by various changes to the thickness of the piezoelectric layer and the dimensions of the electrodes. Additionally, Figure 28 This is the result when using a piezoelectric layer of LiNbO3 with Z-cut, but the same tendency occurs even when using piezoelectric layers with other cut angles.

[0139] exist Figure 28 In the region enclosed by ellipse J, the stray energy increases to 1.0. According to... Figure 28 It is clear that if the relative bandwidth exceeds 0.17, that is, if it exceeds 17%, then even if the parameters constituting the relative bandwidth are changed, large spurious signals with a spurious level greater than 1 will appear in the passband. That is, like... Figure 27 As shown in the resonance characteristics, large stray rays appear within the band, as indicated by arrow B. Therefore, a relative bandwidth of 17% or less is preferred. In this case, stray rays can be reduced by adjusting the film thickness of the piezoelectric layer 2, the dimensions of electrodes 3 and 4, etc.

[0140] Figure 29 This is a graph showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth. Various elastic wave devices with different d / 2p and MR were constructed in the above-mentioned elastic wave devices, and the relative bandwidth was measured. Figure 29The portion indicated by the shading to the right of the dashed line D represents the area with a relative bandwidth of 17% or less. The boundary between this shaded area and the unshaded area can be represented by MR = 3.5(d / 2p) + 0.075, that is, MR = 1.75(d / p) + 0.075. Therefore, it is preferable that MR ≤ 1.75(d / p) + 0.075. In this case, it is easy to set the relative bandwidth to 17% or less. More preferably... Figure 29 The region to the right of the dashed line D1 in the diagram is MR = 3.5(d / 2p) + 0.05. That is, as long as MR ≤ 1.75(d / p) + 0.05, the relative bandwidth can be reliably kept below 17%.

[0141] Figure 30 This is a diagram showing the mapping of the relative bandwidth to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0. Figure 30 The area shown by the shading is the region where a relative bandwidth of at least 5% can be obtained. If the range of this region is approximated, it becomes the range represented by the following equations (1), (2) and (3).

[0142] (0°±10°, 0°~20°, any ψ)…Equation (1)

[0143] (0°±10°, 20°~80°, 0°~60°(1-(θ-50) 2 / 900) 1 / 2 () or (0°±10°, 20°~80°, [180°-60°(1-(θ-50))) 2 / 900) 1 / 2 [~180°)…Equation (2)

[0144] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ)…Equation (3)

[0145] Therefore, within the Euler angle range of equations (1), (2), or (3) above, it is preferable to sufficiently expand the relative bandwidth. The same applies when the piezoelectric layer 2 is a lithium tantalate layer.

[0146] In the elastic wave devices of the first and second embodiments, at least one of the first and second IDT electrodes preferably has a d / p ratio of 0.24 or less, as described above. This results in better resonance characteristics. Furthermore, in the elastic wave devices of the first and second embodiments, at least one of the first and second IDT electrodes preferably satisfies MR ≤ 1.75(d / p) + 0.075, as described above. In this case, spurious emissions can be suppressed more reliably.

[0147] In the elastic wave device of the first and second embodiments, the piezoelectric layer is preferably a lithium niobate layer or a lithium tantalate layer. Furthermore, the Euler angles of the lithium niobate or lithium tantalate constituting the piezoelectric layer are... Preferably, it falls within the range of equation (1), equation (2), or equation (3) above. In this case, the relative bandwidth can be sufficiently expanded.

[0148] Explanation of reference numerals in the attached figures

[0149] 1: Elastic wave device;

[0150] 2: Piezoelectric layer;

[0151] 2a: First main face;

[0152] 2b: Second main face;

[0153] 3, 4: Electrodes;

[0154] 5, 6: Busbar 1 and Busbar 2;

[0155] 7: Insulation layer;

[0156] 7a: Through hole;

[0157] 8: Supporting components;

[0158] 8a: Through hole;

[0159] 9: Hollow section;

[0160] 10: Elastic wave device;

[0161] 11A, 11B: First IDT electrode, Second IDT electrode;

[0162] 12: Piezoelectric substrate;

[0163] 13: Supporting components;

[0164] 13c, 13d: First cavity section, second cavity section;

[0165] 14: Piezoelectric layer;

[0166] 14a, 14b: 1st main surface, 2nd main surface;

[0167] 14c: Through hole;

[0168] 15: Intermediate layer;

[0169] 16: Support base plate;

[0170] 17: Insulating film;

[0171] 18: Wiring electrode;

[0172] 21A, 21B: Elastic wave resonators;

[0173] 22A, 22B: First sacrificial layer, second sacrificial layer;

[0174] 23: Connect the electrodes;

[0175] 24: Piezoelectric substrate;

[0176] 24a, 24b: First principal face, second principal face;

[0177] 25: Lead-out wiring;

[0178] 26, 27: First electrode finger, second electrode finger;

[0179] 28, 29: First electrode finger, second electrode finger;

[0180] 30: Elastic wave device;

[0181] 32A: Input terminal;

[0182] 32B: Output terminal;

[0183] 80: Elastic wave device;

[0184] 108, 108A~108C: Wiring electrodes;

[0185] 201: Piezoelectric film;

[0186] 201a, 201b: 1st main surface, 2nd main surface;

[0187] 451, 452: Region 1 and Region 2;

[0188] C: Incentive region;

[0189] P31a~P31d, P32a~P32d: Parallel arm resonators;

[0190] S31a, S31b, S32, S33a, S33b: Series arm resonators;

[0191] VP1: Imaginary plane.

Claims

1. An elastic wave device, comprising: Supporting components, including a supporting base plate; A piezoelectric layer is disposed on the support member, having a first main surface located on the side of the support member and a second main surface facing the first main surface; A first IDT electrode, disposed on the first main surface, has multiple electrode fingers; and The second IDT electrode, disposed on the portion of the second main surface that does not overlap with the first IDT electrode when viewed from above, has multiple electrode fingers. Let the thickness of the piezoelectric layer be d, and the center-to-center distance between adjacent electrodes be p. In this case, d / p is less than or equal to 0.5 in both the first IDT electrode and the second IDT electrode. The elastic wave device also includes: An insulating film is disposed on the second main surface, in a top view, in a portion that overlaps with the first IDT electrode; as well as The wiring electrode passes through the insulating film in the portion that overlaps with the first IDT electrode when viewed from above, and is connected to the second IDT electrode.

2. The elastic wave device according to claim 1, wherein, The support member has a cavity, and the first IDT electrode is disposed within the cavity. A through hole is provided in the piezoelectric layer to reach the cavity. The elastic wave device further includes: a connecting electrode that passes through the through hole and is connected to the first IDT electrode.

3. The elastic wave device according to claim 2, wherein, The support member has an intermediate layer disposed between the support substrate and the piezoelectric layer. At least a portion of the void portion is provided in the intermediate layer.

4. The elastic wave device according to claim 3, wherein, The cavity is the first cavity. At least a portion of the second void is provided in the portion of the intermediate layer that overlaps with the second IDT electrode when viewed from above.

5. The elastic wave device according to any one of claims 1 to 4, wherein, The Young's modulus of the insulating film is below 10 GPa.

6. The elastic wave device according to claim 1, wherein, The relative permittivity of the insulating film is less than 5.

7. The elastic wave device according to claim 1, wherein, The insulating film is a resin film.

8. The elastic wave device according to claim 1, wherein, The thickness of the insulating film is 2 μm or more.

9. The elastic wave device according to claim 1, wherein, In at least one of the first IDT electrode and the second IDT electrode, d / p is 0.24 or less.

10. The elastic wave device according to claim 1, wherein, In each of the first IDT electrode and the second IDT electrode, the area where adjacent electrode fingers overlap when viewed in opposite directions is the excitation region. In at least one of the first IDT electrode and the second IDT electrode, the metallization ratio of the plurality of electrode fingers relative to the excitation region is set as MR, where MR ≤ 1.75(d / p) + 0.075 is satisfied.

11. The elastic wave device according to claim 1, wherein, The piezoelectric layer is a lithium tantalate layer or a lithium niobate layer.

12. The elastic wave device according to claim 11, wherein, The Euler angles (φ, θ, ψ) of the lithium tantalate or lithium niobate constituting the piezoelectric layer are within the range of the following equations (1), (2), or (3). (0°±10°, 0°~20°, any ψ) … Equation (1) (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50)) 2 / 900) 1 / 2 ~180°) …Equation (2) (0° ± 10°, [180° - 30° (1 - (ψ - 90 2 / 8100) 1 / 2 ] ~ 180°, any ψ) …Formula (3).

13. A method for manufacturing an elastic wave device, comprising the method for manufacturing the elastic wave device according to any one of claims 1 to 12, wherein, have: The process of setting the first IDT electrode on the first main surface of the piezoelectric layer; The process of setting the second IDT electrode in the second main surface of the piezoelectric layer at a position that does not overlap with the first IDT electrode when viewed from above; The process of bonding the piezoelectric layer and the support substrate to form a laminate containing the piezoelectric layer and the support substrate; The process of setting the insulating film on the portion of the second main surface that overlaps with the first IDT electrode when viewed from above; as well as The wiring electrode is configured to connect to the second IDT electrode, and the process passes through the insulating film in the portion that overlaps with the first IDT electrode when viewed from above.

14. The method for manufacturing the elastic wave device according to claim 13, wherein, In the process of setting the first IDT electrode, lead-out wiring is provided on the first main surface of the piezoelectric layer to connect with the first IDT electrode. In the process of setting the laminate, a sacrificial layer is provided on the first main surface of the piezoelectric layer to cover the first IDT electrode, an intermediate layer is provided on the first main surface to cover the sacrificial layer, and the intermediate layer is bonded to the support substrate. The manufacturing method of the elastic wave device also includes: The process of setting multiple through holes in the piezoelectric layer to reach the sacrificial layer and the lead-out wiring respectively; The process of removing the sacrificial layer by means of the through hole reaching the sacrificial layer, thereby creating the cavity; as well as A connecting electrode is provided in the through hole leading to the lead wire, so as to connect to the lead wire.

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