Elastic wave device

Abstract

Provided is an elastic wave device having excellent heat dissipation. An elastic wave device (10) includes a support member including a support substrate (14); a piezoelectric layer (16) disposed on the support member; and an IDT electrode (11) disposed on a first main surface (16a) of the piezoelectric layer (16). An air gap portion (14c) is provided in the support member so as to open on the piezoelectric layer (16) side. The support member (14) has an inner side wall (14e) facing the air gap portion (14c). A high-thermal-conductivity film (17) is directly or indirectly laminated on at least a portion of a second main surface (16b) of the piezoelectric layer (16) and reaches the inner side wall (14e) of the support member (14).

Description

Technical Field

[0001] The present invention relates to an elastic wave device having a piezoelectric layer comprising lithium niobate or lithium tantalate. Background Technology

[0002] Previously, elastic wave devices having a piezoelectric layer comprising lithium niobate or lithium tantalate were known. For example, Patent Document 1 disclosed an elastic wave device in which a piezoelectric layer comprising lithium niobate or lithium tantalate was provided on a support substrate having a cavity. In this elastic wave device, an IDT electrode was provided on the upper surface of the piezoelectric layer above the cavity.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: U.S. Patent No. 10491192 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In conventional elastic wave devices as described in Patent Document 1, improved heat dissipation is required.

[0008] The purpose of this invention is to provide an elastic wave device with excellent heat dissipation.

[0009] Technical solutions for solving the problem

[0010] The present invention comprises: a support member including a support substrate; a piezoelectric layer disposed on the support member having a first main surface and a second main surface facing each other; and an IDT electrode disposed on the first main surface of the piezoelectric layer having a plurality of electrode fingers; an air gap portion with an opening on the piezoelectric layer side is provided on the support member, the air gap portion overlapping at least a portion of the IDT electrode in the thickness direction of the support member; the support member having an inner sidewall facing the air gap portion; and the elastic wave device further comprises: a high thermal conductivity film directly or indirectly laminated on at least a portion of the second main surface of the piezoelectric layer and reaching the inner sidewall of the support member, the high thermal conductivity film having a higher thermal conductivity than the piezoelectric layer.

[0011] Invention Effects

[0012] According to the present invention, an elastic wave device with excellent heat dissipation can be provided. Attached Figure Description

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

[0014] Figure 2This is a cross-sectional view of the elastic wave device according to the first embodiment of the present invention, along... Figure 1 A sectional view of the section along line II.

[0015] Figure 3 (a)~ Figure 3 (d) are front sectional views illustrating an example of a method for manufacturing an elastic wave device according to the first embodiment of the present invention.

[0016] Figure 4 (a)~ Figure 4 (c) is a front sectional view illustrating an example of a method for manufacturing an elastic wave device according to the first embodiment of the present invention.

[0017] Figure 5 (a) and Figure 5 (b) are front sectional views illustrating an example of a method for manufacturing an elastic wave device according to the first embodiment of the present invention.

[0018] Figure 6 (a)~ Figure 6 (d) are front sectional views illustrating another example of the manufacturing method of the elastic wave device according to the first embodiment of the present invention.

[0019] Figure 7 (a)~ Figure 7 (c) are front sectional views illustrating another example of the manufacturing method of the elastic wave device according to the first embodiment of the present invention.

[0020] Figure 8 This is a front sectional view of the elastic wave device according to the second embodiment of the present invention.

[0021] Figure 9 This is a front sectional view of the elastic wave device according to the third embodiment of the present invention.

[0022] Figure 10 This is a front sectional view of the elastic wave device according to the fourth embodiment of the present invention.

[0023] Figure 11 This is a front sectional view of the elastic wave device according to the fifth embodiment of the present invention.

[0024] Figure 12 This is a partially cut-out perspective view of the elastic wave device according to the sixth embodiment of the present invention.

[0025] Figure 13 (a) and Figure 13 (b) is a simplified perspective view showing the appearance of an elastic wave device utilizing a thickness shear mode and a top view showing the electrode structure on the piezoelectric layer.

[0026] Figure 14 It is along Figure 13 A sectional view of the portion of line AA in (a).

[0027] Figure 15 (a) is a schematic front sectional view illustrating the propagation of Lamb waves through a piezoelectric film in a conventional elastic wave device. Figure 15 (b) is a schematic front sectional view used to illustrate the vibration of an elastic wave device utilizing a thickness shear mode.

[0028] Figure 16 It is a diagram used to illustrate the amplitude direction of the body wave in the thickness shear mode.

[0029] Figure 17 This is a diagram illustrating the resonant characteristics of an elastic wave device utilizing a thickness shear mode.

[0030] Figure 18 This is a graph showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance between adjacent electrode fingers is set to p and the thickness of the piezoelectric layer is set to d.

[0031] Figure 19 This is a top view showing an elastic wave apparatus that utilizes a thickness shear mode for body waves.

[0032] Figure 20 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.

[0033] Figure 21 This is a graph showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth. Detailed Implementation

[0034] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0035] Figure 1 This is a top view of the elastic wave device according to the first embodiment of the present invention. Figure 2 This is a cross-sectional view of the elastic wave device according to the first embodiment of the present invention. Additionally, Figure 2 It is along Figure 1 A sectional view of the portion along line II.

[0036] like Figure 2 As shown, the elastic wave device 10 has a piezoelectric substrate 12 and an IDT electrode 11 disposed on the piezoelectric substrate 12. The piezoelectric substrate 12 has a support substrate 14, a dielectric layer 15, and a piezoelectric layer 16, which serve as support members. The piezoelectric layer 16 is disposed on the support substrate 14, with the dielectric layer 15 in between.

[0037] The support substrate 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. A recess 14c is provided on the first main surface 14a. Furthermore, the support substrate 14 has a support portion 14d. The support portion 14d is the portion that surrounds the recess 14c and supports the piezoelectric layer 16 via the dielectric layer 15.

[0038] A piezoelectric layer 16 is disposed on the dielectric layer 15, thereby sealing the recess 14c. In this embodiment, the recess 14c constitutes an air gap G. The air gap G is surrounded by the support substrate 14, the dielectric layer 15, and the piezoelectric layer 16.

[0039] The piezoelectric layer 16 has a first main surface 16a and a second main surface 16b. The first main surface 16a and the second main surface 16b are opposite to each other. The second main surface 16b is the main surface on the side of the supporting substrate 14.

[0040] The piezoelectric layer 16 contains lithium niobate such as LiNbO3 or lithium tantalate such as LiTaO3. Furthermore, in this specification, the term "a component contains a certain material" includes cases where the material contains trace amounts of impurities sufficient to prevent degradation of the electrical properties of the elastic wave device.

[0041] like Figure 1 As shown, an IDT electrode 11 is provided on the first main surface 16a of the piezoelectric layer 16. The IDT electrode 11 has a first busbar 22 and a second busbar 23, and a plurality of first electrode fingers 24 and a plurality of second electrode fingers 25. The first busbar 22 and the second busbar 23 are opposite to each other. The plurality of first electrode fingers 24 are periodically arranged. One end of each of the plurality of first electrode fingers 24 is connected to the first busbar 22. The plurality of second electrode fingers 25 are periodically arranged. One end of each of the plurality of second electrode fingers 25 is connected to the second busbar 23. The plurality of first electrode fingers 24 and the plurality of second electrode fingers 25 are interleaved and interlocked. Wiring electrodes 22a and 23a are provided on the first main surface 16a. The wiring electrodes 22a and 23a are electrically connected to the IDT electrode 11.

[0042] The direction in which adjacent first electrode fingers 24 and second electrode fingers 25 face each other is defined as the electrode finger facing direction. In this embodiment, the electrode finger facing direction is orthogonal to the direction in which the plurality of first electrode fingers 24 and the plurality of second electrode fingers 25 extend. Hereinafter, the first electrode fingers 24 and the second electrode fingers 25 will sometimes be referred to simply as electrode fingers.

[0043] In addition, the air gap G only needs to overlap with at least a portion of the IDT electrode 11 in the thickness direction of the support member.

[0044] In the elastic wave device 10, an elastic wave is excited by applying an alternating voltage to the IDT electrode 11. The elastic wave device 10 is configured, for example, to utilize a volume wave with a thickness shear mode. The optimal configuration for this elastic wave device utilizing a volume wave with a thickness shear mode will be described later. Figure 13 The following diagrams will be used for description.

[0045] like Figure 2 As shown, in the elastic wave device 10, the support substrate 14 has an inner sidewall 14e facing the air gap G. Furthermore, in the air gap G, the support substrate 14 has a bottom surface 14f opposite to the piezoelectric layer 16. In the air gap G, a high thermal conductivity film 17 is laminated on the second main surface 16b of the piezoelectric layer 16. The high thermal conductivity film 17 is directly laminated on the second main surface 16b. However, the high thermal conductivity film 17 can also be indirectly laminated on the second main surface 16b.

[0046] The thermal conductivity of the high thermal conductivity film 17 is higher than that of the piezoelectric layer 16. The high thermal conductivity film 17 is constructed using such a high thermal conductivity material. Examples of materials with high thermal conductivity include metals and insulators with thermal conductivity higher than that of piezoelectric single crystals.

[0047] The high thermal conductivity film 17 extends from the second main surface 16b of the piezoelectric layer 16 to the inner sidewall 14e of the support substrate 14. Furthermore, in this embodiment, the high thermal conductivity film 17 is configured to reach the bottom surface 14f of the recess 14c. That is, in this embodiment, the high thermal conductivity film 17 is configured to surround the air gap G.

[0048] In the past, in structures where a piezoelectric layer is positioned above an air gap, there was a problem that the heat generated by excitation was difficult to dissipate from the piezoelectric layer to the outside. More specifically, if an IDT electrode is driven, heat is generated in the region of the piezoelectric layer where the IDT electrode is positioned. However, if an air gap exists below the piezoelectric layer, the generated heat is not easily dissipated. That is, there is a problem of low heat dissipation.

[0049] In contrast, in the elastic wave device 10, because the aforementioned high thermal conductivity membrane 17 is provided, the heat generated by the excitation source can be rapidly released to the air gap G side through the high thermal conductivity membrane 17. Therefore, heat dissipation can be effectively improved.

[0050] Preferably, at least one of the support substrate 14 and the dielectric layer 15 has a higher thermal conductivity than the piezoelectric layer 16. This further improves heat dissipation.

[0051] Preferably, the thermal conductivity of the support substrate 14 is higher than that of the piezoelectric layer 16. This allows for more effective heat dissipation.

[0052] In addition, the support member is composed only of the support substrate 14, but it may also have a structure in which other dielectric layers and semiconductor layers are stacked on the support substrate 14.

[0053] Preferably, the high thermal conductivity film 17 is a dielectric film containing a dielectric material with high thermal conductivity as described above. Suitable dielectric materials include, for example, alumina, silicon nitride, zirconium oxide, titanium dioxide, or graphene. More preferably, alumina, silicon oxide, silicon nitride, or silicon oxynitride can be used as the dielectric material. This allows for more effective heat dissipation.

[0054] The thickness of the high thermal conductivity film 17 can be uniform, but it can also vary partially. For example... Figure 2 As shown, the thickness of the high thermal conductivity film 17 on the inner sidewall 14e and the bottom surface 14f may also be greater than the thickness of the high thermal conductivity film 17 on the second main surface 16b of the piezoelectric layer 16.

[0055] Reference Figure 3 (a) to (d) and Figure 4 (a)~ Figure 4 (c) and Figure 5 (a) and Figure 5 (b) will describe an example of a method for manufacturing the elastic wave device 10.

[0056] First, such as Figure 3 As shown in (a), a recess 14c is formed in the support substrate 14. The formation of this recess 14c can be achieved by applying a resist from the first main surface 14a side, patterning, etching the support substrate, and removing the resist.

[0057] Next, as Figure 3 As shown in (b), a sacrificial layer 18 is provided in the recess 14c. The formation of this sacrificial layer 18 can be achieved by forming a film of the sacrificial layer 18 and by planarization through grinding. The sacrificial layer 18 is composed of material that will be removed in the process described later.

[0058] Next, as Figure 3 As shown in (c), a dielectric layer 15 is stacked. After the dielectric layer 15 is stacked, a piezoelectric substrate 16A is bonded to the dielectric layer 15.

[0059] Next, the piezoelectric substrate 16A is ground. This forms... Figure 3 The piezoelectric layer 16 is shown in (d).

[0060] Next, as Figure 4 As shown in (a), IDT electrode 11 and wiring electrodes 22a and 23a are formed by stripping.

[0061] After the resist is applied, patterned, and the piezoelectric layer 16 and dielectric layer 15 of the opening H (described later) are removed by dry etching, the resist layer is removed. Thus, as... Figure 4 As shown in (b), an opening H is formed in the piezoelectric layer 16 and the dielectric layer 15. The opening H is provided to remove the sacrificial layer 18.

[0062] By applying and patterning a resist, the area outside the opening H is protected with the resist. Various etchants used to remove the sacrificial layer 18 and the dielectric layer are injected through the opening H to remove them. Then, the resist is removed. Thus, as... Figure 4 As shown in (c), the sacrificial layer 18 and the dielectric layer 15 are removed. Thus, the air gap G is provided.

[0063] Next, as Figure 5 As shown in (a), a high thermal conductivity film 17 is formed. This film formation can be performed by methods such as ALD (Atomic Layer Deposition) or CVD. ALD is preferred. As a result, a high thermal conductivity film 17 can be formed with high precision thickness.

[0064] Next, as Figure 5 As shown in (b), the ALD layer (high thermal conductivity film 17) on the IDT electrode 11, wiring electrodes 22a and 23a is removed by particle milling. As shown, the high thermal conductivity film 17 may also remain on the sidewall of the opening H.

[0065] In addition, Ar beam plasma beams can be used when performing particle milling.

[0066] Reference Figure 6 (a)~ Figure 6 (d) and Figure 7 (a)~ Figure 7 (c) Another example of the manufacturing method of the elastic wave device 10 of the first embodiment will be described.

[0067] First, such as Figure 6 As shown in (a), a sacrificial layer 18 is formed on the piezoelectric substrate 16A. The sacrificial layer 18 can be formed by applying a resist, patterning, etching the sacrificial layer 18, and removing the resist.

[0068] Next, as Figure 6 As shown in (b), a dielectric layer 15A containing a dielectric is formed as a bonding layer. The dielectric layer 15A is formed, for example, by planarizing it by grinding after the dielectric layer is formed into a film.

[0069] Next, as Figure 6 As shown in (c), a support substrate 14 is stacked on the dielectric layer 15A. That is, by using the dielectric layer 15A as a bonding layer, the piezoelectric substrate 16A and the support substrate 14 can be bonded together.

[0070] Next, as Figure 6 As shown in (d), the piezoelectric substrate 16A is thinned by grinding. As a result, the piezoelectric layer 16 is formed.

[0071] Next, as Figure 7 As shown in (a), an IDT electrode 11 and wiring electrodes 22a and 23a are formed. The IDT electrode 11 and wiring electrodes 22a and 23a can be formed, for example, by a stripping method.

[0072] Next, as Figure 7 As shown in (b), an opening H is provided. The opening H can be formed by applying a resist, patterning, dry etching of the piezoelectric layer 16 of the opening H, and removal of the resist.

[0073] Next, as Figure 7 As shown in (c), the sacrificial layer 18 is removed. The removal of the sacrificial layer 18 can be performed by applying a resist, patterning, removing the sacrificial layer by injecting an etchant into the opening H, and removing the resist.

[0074] Then, as long as... Figure 5 (a) and Figure 5 As shown in (b), a high thermal conductivity film 17 can be formed.

[0075] Furthermore, the manufacturing method of the elastic wave device in this invention is not limited to the examples described above.

[0076] Figure 8 This is a front cross-sectional view of the elastic wave device according to the second embodiment of the present invention. In the elastic wave device 31, the high thermal conductivity film 17 is configured to extend from the second main surface 16b of the piezoelectric layer 16 to the inner sidewall 14e of the support substrate 14, which serves as a support member. That is, the high thermal conductivity film 17 is configured not to reach the bottom surface 14f of the recess 14c of the support substrate 14. In this way, the high thermal conductivity film 17 only needs to have a portion that is directly or indirectly stacked on the second main surface 16b of the piezoelectric layer 16, and a portion that is provided on at least a portion of the inner sidewall 14e of the support substrate 14 connected to the second main surface 16b. As a result, heat dissipation can be effectively improved.

[0077] Figure 9This is a front cross-sectional view of the elastic wave device according to the third embodiment of the present invention. An additional film 33 is provided in the elastic wave device 32. Furthermore, a dielectric layer 15 is provided. Regarding other structures, the elastic wave device 32 is the same as the elastic wave device 31. The additional film 33 is stacked over the entire surface of the second main surface 16b of the piezoelectric layer 16. Moreover, the piezoelectric layer 16 is stacked over the support substrate 14, with the dielectric layer 15 and the additional film 33 in between.

[0078] The high thermal conductivity film 17 is not directly laminated on the second main surface 16b opposite to the IDT electrode 11. That is, the high thermal conductivity film 17 is laminated on the portion of the second main surface 16b facing the air gap G through the additional film 33.

[0079] Even with the additional film 33, heat dissipation can be improved by the high thermal conductivity film 17. That is, the thermal conductivity of the additional film 33 can also be lower than that of the support member. As the additional film 33, it is preferable to use a film containing a material with a higher thermal conductivity than that of the piezoelectric layer 16.

[0080] However, if the thickness of the additional film 33 is thin, its thermal conductivity can also be lower than that of the piezoelectric layer 16. Even in this case, heat dissipation can be improved because of the presence of the high thermal conductivity film 17 on the lower surface. In this way, the high thermal conductivity film 17 can also be indirectly laminated on the second main surface 16b of the piezoelectric layer 16.

[0081] Figure 10 This is a front cross-sectional view of the elastic wave device according to the fourth embodiment of the present invention. In the elastic wave device 40, a piezoelectric layer 16 is directly stacked on a support substrate 14. Furthermore, the support member only includes the support substrate 14. Moreover, the air gap G facing the second main surface of the piezoelectric layer 16 is formed by a through hole 14g provided in the support substrate 14. In this way, a through hole 14g extending from the first main surface 14a to the second main surface 14b may also be provided in the support substrate 14, and the air gap G may be provided therefrom.

[0082] In the elastic wave device 40, the high thermal conductivity film 17 is configured to extend from the second main surface 16b of the piezoelectric layer 16 to the inner sidewall 14e of the support substrate 14. This improves heat dissipation.

[0083] Figure 11 This is a front cross-sectional view of the elastic wave device according to the fifth embodiment of the present invention. In the elastic wave device 50, the inner sidewall 14e facing the air gap G in the support substrate 14 has a protrusion 14e1. The high thermal conductivity film 17 also reaches the bottom surface 14f, covering the protrusion and concave portion of the inner sidewall 14e. In this way, the protrusion 14e1 may be provided in at least a portion of the inner sidewall 14e of the support substrate 14. In this case, the surface area of ​​the high thermal conductivity film 17 is increased. Therefore, heat dissipation can be further improved.

[0084] Figure 12 This is a partially cut perspective view used to illustrate the elastic wave device according to the sixth embodiment of the present invention.

[0085] The elastic wave device 81 has a support substrate 82. A recess with an opening on the upper surface is provided on the support substrate 82. A piezoelectric layer 83 is stacked on the support substrate 82, thus forming an air gap 9. Above the air gap 9, an IDT electrode 84 is provided on the piezoelectric layer 83. Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction. Figure 12 In the diagram, the outer periphery of the air gap 9 is shown by a dashed line. Here, the IDT electrode 84 has a first busbar 84a, a second busbar 84b, and multiple electrodes 84c (serving as first electrode fingers) and multiple electrodes 84d (serving as second electrode fingers). The multiple electrodes 84c are connected to the first busbar 84a. The multiple electrodes 84d are connected to the second busbar 84b. The multiple electrodes 84c and 84d are interleaved and interlocked.

[0086] A high thermal conductivity film 87 is provided in the air gap 9, so that it reaches the inner wall of the recess from below the piezoelectric layer 83.

[0087] In the elastic wave device 81, an alternating electric field is applied to the IDT electrode 84 on the air gap 9, thereby exciting a Lamb wave, which is a plate wave. Furthermore, because reflectors 85 and 86 are provided on both sides, resonant characteristics can be obtained. Thus, the elastic wave device of the present invention can also utilize plate waves.

[0088] The following describes an elastic wave device that utilizes a volume wave with a thickness shear mode, which appropriately employs the elastic wave device of the present invention. The support member in the following examples corresponds to the support substrate in the present invention.

[0089] Figure 13 (a) is a simplified three-dimensional diagram showing the appearance of an elastic wave device utilizing a thickness shear mode for volume waves. Figure 13 (b) is a top view showing the electrode structure on the piezoelectric layer. Figure 14 It is along Figure 13 A sectional view of the portion of line AA in (a).

[0090] The elastic wave device 1 has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. The cutting angle of the LiNbO3 and LiTaO3 is Z-cut, but it can also be rotationally Y-cut or X-cut. 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. Electrode fingers 3 and 4 are provided on the first main surface 2a. Figure 13 (a) and Figure 13 In (b), multiple electrode fingers 3 are connected to the first busbar 5. Multiple electrode fingers 4 are connected to the second busbar 6. The multiple electrode fingers 3 and multiple electrode fingers 4 are interleaved. Electrode fingers 3 and electrode fingers 4 have a rectangular shape and a length direction. In a direction orthogonal to this length direction, electrode fingers 3 and adjacent electrode fingers 4 are opposite each other. The length directions of electrode fingers 3 and 4, as well as the directions orthogonal to the length directions of electrode fingers 3 and 4, are directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that electrode fingers 3 and adjacent electrode fingers 4 are opposite each other in a direction that intersects the thickness direction of the piezoelectric layer 2. Furthermore, the length directions of electrode fingers 3 and 4 can also be... Figure 13 (a) and Figure 13 The directions shown in (b) that are orthogonal to the length directions of electrodes 3 and 4 are reversed. That is, electrodes 3 and 4 can also be positioned... Figure 13 (a) and Figure 13 In (b), the first busbar 5 and the second busbar 6 extend in the direction of extension. In this case, the first busbar 5 and the second busbar 6 become in Figure 13 (a) and Figure 13In (b), electrode fingers 3 and 4 extend in the direction of extension. Furthermore, multiple pairs of structures are provided in a direction orthogonal to the length direction of electrode fingers 3 and 4, where electrode fingers 3 connected to one potential and electrode fingers 4 connected to another potential are adjacent. Here, "adjacent to electrode fingers 3 and 4" does not mean that electrode fingers 3 and 4 are configured in direct contact, but rather that electrode fingers 3 and 4 are arranged with a gap between them. Furthermore, when electrode fingers 3 and 4 are adjacent, no electrodes connected to signal electrodes or ground electrodes, including other electrode fingers 3 and 4, are arranged between electrode fingers 3 and 4. This number of pairs does not need to be an integer; it can be 1.5 pairs, 2.5 pairs, etc. Regarding the center-to-center distance between electrode fingers 3 and 4, i.e., the spacing, it is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the width of electrode fingers 3 and 4, i.e., the dimension in the opposing direction of electrode fingers 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 electrode fingers 3 and 4 is the distance connecting the center of the dimension (width dimension) of electrode finger 3 in a direction orthogonal to the length direction of electrode finger 3 and the center of the dimension (width dimension) of electrode finger 4 in a direction orthogonal to the length direction of electrode finger 4.

[0091] Furthermore, in the elastic wave device 1, because a Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrodes 3 and 4 becomes the direction orthogonal to the polarization direction of the piezoelectric layer 2. This is not limited to cases where a piezoelectric material with a different cut angle is used as the 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 the electrodes 3 and 4 and the polarization direction is, for example, within the range of 90° ± 10°).

[0092] A support member 8 is stacked on the second main surface 2b of the piezoelectric layer 2, separated by an insulating layer 7. The insulating layer 7 and the support member 8 have a frame-like shape, such as... Figure 14 As shown, it has openings 7a and 8a. Therefore, an air gap 9 is provided so as not to interfere with the vibration of the excitation region C of the piezoelectric layer 2. Thus, 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 electrode fingers 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.

[0093] 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 face of the piezoelectric layer 2 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.

[0094] 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 forsterite; various ceramics; dielectrics such as diamond and glass; and semiconductors such as gallium nitride.

[0095] The aforementioned electrode fingers 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, the electrode fingers 3 and 4, as well as the first busbar 5 and the second busbar 6, have a structure in which an Al film is laminated on a Ti film. Alternatively, a close-fitting layer other than a Ti film may also be used.

[0096] During operation, an alternating current voltage is applied between multiple electrode fingers 3 and multiple electrode fingers 4. More specifically, an alternating current voltage is applied between the first busbar 5 and the second busbar 6. This allows for 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, when the thickness of the piezoelectric layer 2 is set to d, and the center-to-center distance between any two adjacent electrode fingers 3 and 4 is set to p, d / p is set to 0.5 or less. Therefore, the aforementioned thickness shear mode bulk wave can be effectively excited, resulting in good resonant characteristics. More preferably, d / p is 0.24 or less, in which case even better resonant characteristics can be obtained.

[0097] In the elastic wave device 1, the above-described structure ensures that even if the number of electrode fingers 3 and 4 is reduced to achieve miniaturization, a decrease in the Q value is not easily observed. This is because even with a reduction in the number of electrode fingers in the reflectors on both sides, propagation loss is minimal. 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 15 (a) and Figure 15 (b) explains the difference between the Lamb wave used in the elastic wave device and the volume wave of the thickness shear mode described above.

[0098] Figure 15(a) is a schematic front sectional view illustrating the Lamb wave propagating in the piezoelectric film of the elastic wave device as described in Patent Document 1. 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 15 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, the piezoelectric film 201 vibrates as a whole, but because the wave propagates in the X direction, reflectors are placed on both sides to obtain resonant characteristics. Therefore, wave propagation loss occurs, and in the pursuit of miniaturization, that is, in reducing the number of electrode finger pairs, the Q value decreases.

[0099] In contrast, such as Figure 15 As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction. Therefore, the wave propagates and resonates essentially in the direction connecting the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2, i.e., in 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 finger pairs including electrode fingers 3 and 4 is reduced in order to promote miniaturization, the Q value is not easily decreased.

[0100] In addition, such as Figure 16 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 16 The diagram schematically illustrates a bulk wave when a voltage is applied between electrode finger 3 and electrode finger 4, with electrode finger 4 having a higher potential than electrode finger 3. The first region 451 is the region between the imaginary plane VP1 and the first principal surface 2a in the excitation region C, wherein the 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 principal surface 2b in the excitation region C.

[0101] As described above, the elastic wave device 1 is provided with at least one pair of electrodes, including electrode fingers 3 and electrode fingers 4. However, since the wave is not propagated in the X direction, the number of pairs of electrode fingers including electrode fingers 3 and 4 does not need to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0102] For example, electrode 3 is connected to the signal potential, and electrode 4 is 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 connected to the signal potential or connected to the ground potential, and no floating electrode is provided.

[0103] Figure 17 It is shown Figure 14 The diagram shows the resonance characteristics of the elastic wave device. Furthermore, the design parameters for the elastic wave device 1 with these resonance characteristics are as follows.

[0104] Piezoelectric layer 2: LiNbO3 with Euler angles of (0°, 0°, 90°) and a thickness of 400 nm.

[0105] When viewed in a direction orthogonal to the length direction of electrode fingers 3 and 4, the overlapping area of ​​electrode fingers 3 and 4, i.e., the excitation region C, has a length of 40 μm, contains 21 pairs of electrode fingers including electrode fingers 3 and 4, a center distance between electrode fingers of 3 μm, a width of 500 nm for electrode fingers 3 and 4, and a d / p ratio of 0.133.

[0106] Insulating layer 7: Silicon oxide film with a thickness of 1 μm.

[0107] Supporting component 8: Si.

[0108] In addition, the so-called length of the excitation region C refers to the dimension of the excitation region C along the length direction of electrodes 3 and 4.

[0109] In this embodiment, the distance between the electrode fingers in the electrode finger pairs including electrode fingers 3 and 4 is equal in all pairs. That is, electrode fingers 3 and 4 are arranged at equal intervals.

[0110] according to Figure 17 It is clear that, despite the absence of a reflector, a good resonant characteristic with a relative bandwidth of 12.5% ​​was achieved.

[0111] Furthermore, when the thickness of the piezoelectric layer 2 is set to d, and the center-to-center distance between the electrodes of electrode finger 3 and electrode finger 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 18 This needs to be explained.

[0112] With Get Figure 17 The elastic wave device with the resonant characteristics shown was also used to obtain multiple elastic wave devices, but with d / 2p varied. Figure 18 This is a graph showing the relationship between the relative bandwidths of the d / 2p and elastic wave devices as resonators.

[0113] according to Figure 18 It is clear that if d / 2p exceeds 0.25, i.e., if d / p > 0.5, then even if d / p is adjusted, the relative bandwidth will be less than 5%. In contrast, when d / 2p ≤ 0.25, i.e., d / p ≤ 0.5, if d / p is varied within this range, the relative bandwidth can be increased to 5% or more, i.e., a resonator with a high coupling coefficient can be constructed. Furthermore, when d / 2p is 0.12 or less, i.e., when d / p is 0.24 or less, the relative bandwidth can be increased to 7% or more. In addition, if d / p is adjusted within this range, a resonator with an even wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be achieved. Therefore, it can be seen that by keeping d / p below 0.5, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear mode of bulk waves can be constructed.

[0114] Figure 19 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, each with electrode fingers 3 and 4, are provided on the first main surface 2a of the piezoelectric layer 2. Furthermore, Figure 19 K in the figure represents the cross width. As mentioned earlier, the number of electrode fingers can also be a pair. Even in this case, if the aforementioned d / p is less than 0.5, it is still possible to effectively excite the bulk wave of the thickness shear mode.

[0115] Figure 20 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 20 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).

[0116] (0°±10°, 0°~20°, any ψ)…Equation (1)

[0117] (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)

[0118] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ)…Equation (3)

[0119] Therefore, within the Euler angle range of equations (1), (2), or (3) above, it is preferable to achieve a sufficiently wide relative bandwidth. The same applies when the piezoelectric layer 2 is a lithium tantalate layer.

[0120] Figure 21 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 21 The area to the right of the dashed line E, indicated by the shading, represents the region with a relative bandwidth of 17% or less. When the relative bandwidth is 17% or less, stray energy can be appropriately reduced by adjusting the film thickness of the piezoelectric layer 2, the dimensions of the electrode fingers 3 and 4, etc. The boundary between the shading region and the unshading region is represented by MR = 3.5(d / 2p) + 0.075. That is, MR = 1.75(d / p) + 0.075. Therefore, MR ≤ 1.75(d / p) + 0.075 is preferred. In this case, it is easier to achieve a relative bandwidth of 17% or less. More preferably... Figure 21 The region to the right of MR = 3.5(d / 2p) + 0.05 is shown by the dashed line E1. That is, if MR ≤ 1.75(d / p) + 0.05, the relative bandwidth can be reliably kept below 17%.

[0121] Explanation of reference numerals in the attached figures

[0122] 1: Elastic wave device;

[0123] 2: Piezoelectric layer;

[0124] 2a: First main face;

[0125] 2b: Second main face;

[0126] 3, 4: Electrode fingers;

[0127] 5, 6: Busbar 1 and Busbar 2;

[0128] 7: Insulation layer;

[0129] 7a: Opening;

[0130] 8: Supporting components;

[0131] 8a: Opening;

[0132] 9: Air gap;

[0133] 10: Elastic wave device;

[0134] 11: IDT electrode;

[0135] 12: Piezoelectric substrate;

[0136] 14: Support base plate;

[0137] 14a, 14b: 1st main surface, 2nd main surface;

[0138] 14c: concave part;

[0139] 14d: Support part;

[0140] 14e: Inner wall;

[0141] 14e1: convex part;

[0142] 14f: bottom surface;

[0143] 14g: Through hole;

[0144] 15, 15A: Dielectric layer;

[0145] 16: Piezoelectric layer;

[0146] 16A: Piezoelectric substrate;

[0147] 16a, 16b: 1st main surface, 2nd main surface;

[0148] 17: High thermal conductivity membrane;

[0149] 18: Sacrificial Layer;

[0150] 22, 23: Busbar 1 and Busbar 2;

[0151] 22a, 23a: Wiring electrodes;

[0152] 24, 25: First electrode finger, second electrode finger;

[0153] 31, 32: Elastic wave device;

[0154] 33: Additional membrane;

[0155] 40, 50, 80, 81: Elastic wave devices;

[0156] 82: Support base plate;

[0157] 83: Piezoelectric layer;

[0158] 84: IDT electrode;

[0159] 84a, 84b: Busbar 1 and Busbar 2;

[0160] 84c, 84d: Electrodes;

[0161] 85, 86: Reflectors;

[0162] 87: High thermal conductivity membrane;

[0163] 201: Piezoelectric film;

[0164] 201a, 201b: 1st main surface, 2nd main surface;

[0165] 451, 452: Region 1 and Region 2;

[0166] C: Incentive region;

[0167] D: Intersection area;

[0168] G: Air gap;

[0169] H: Opening;

[0170] VP1: Imaginary plane.

Claims

1. An elastic wave device, comprising: Supporting components, including a supporting base plate; A piezoelectric layer, disposed on the support member, has a first main surface and a second main surface that are opposite to each other; and An IDT electrode, disposed on the first main surface of the piezoelectric layer, has multiple electrode fingers. The support member has an air gap with an opening on the piezoelectric layer side, and the air gap overlaps with at least a portion of the IDT electrode in the thickness direction of the support member. The support member has an inner wall facing the air gap. The elastic wave device further comprises: a high thermal conductivity film indirectly laminated on at least a portion of the second main surface of the piezoelectric layer and reaching the inner sidewall of the support member, wherein the thermal conductivity of the high thermal conductivity film is higher than that of the piezoelectric layer. An additional film is provided on the second main surface of the piezoelectric layer, the additional film being disposed between the second main surface of the piezoelectric layer and the high thermal conductivity film, the additional film comprising a material with a lower thermal conductivity than the support member.

2. The elastic wave device according to claim 1, wherein, The support member has the support substrate and a dielectric layer disposed between the support substrate and the piezoelectric layer.

3. The elastic wave device according to claim 2, wherein, The thermal conductivity of at least one of the supporting substrate and the dielectric layer is higher than that of the piezoelectric layer.

4. The elastic wave device according to claim 1, wherein, The support member is composed solely of the support base plate.

5. The elastic wave device according to claim 4, wherein, The thermal conductivity of the support substrate is higher than that of the piezoelectric layer.

6. The elastic wave device according to any one of claims 1 to 5, wherein, The inner sidewall is provided with protrusions and recesses.

7. The elastic wave device according to any one of claims 1 to 5, wherein, In the air gap, the support member has a bottom surface opposite to the piezoelectric layer.

8. The elastic wave device according to claim 7, wherein, The high thermal conductivity membrane reaches the bottom surface of the support member located in the air gap.

9. The elastic wave device according to any one of claims 1 to 5, wherein, The air gap is a through hole that passes through the support member.

10. The elastic wave device according to any one of claims 1 to 5, wherein, The high thermal conductivity membrane is a dielectric membrane.

11. The elastic wave device according to any one of claims 1 to 5, wherein, The high thermal conductivity film is formed by ALD (atomic layer deposition) film formation method.

12. The elastic wave device according to claim 11, wherein, The high thermal conductivity film comprises one of aluminum oxide, silicon oxide, silicon nitride, and silicon oxynitride.

13. The elastic wave device according to any one of claims 1 to 5, wherein, The elastic wave device is configured to utilize plate waves.

14. The elastic wave device according to any one of claims 1 to 5, wherein, The elastic wave device is configured to utilize a body wave with a thickness shear mode.

15. The elastic wave device according to claim 14, wherein, Let the thickness of the piezoelectric layer be d, and let the center-to-center distance between adjacent electrodes be p. In this case, d / p is less than 0.

5.

16. The elastic wave device according to claim 15, wherein, d / p is below 0.

24.

17. The elastic wave device according to claim 15 or 16, wherein, The area where adjacent electrode fingers overlap when viewed in opposite directions is the excitation region. When the metallization ratio of the multiple electrode fingers relative to the excitation region is set as MR, MR ≤ 1.75 (d / p) + 0.075 is satisfied.

18. The elastic wave device according to any one of claims 1 to 5, wherein, The piezoelectric layer is a lithium tantalate layer or a lithium niobate layer.

19. The elastic wave device according to claim 18, wherein, The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate 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) … Equation (3).

20. An elastic wave device, comprising: Supporting components, including a supporting base plate; A piezoelectric layer, disposed on the support member, has a first main surface and a second main surface that are opposite to each other; and An IDT electrode, disposed on the first main surface of the piezoelectric layer, has multiple electrode fingers. The overlapping area of ​​adjacent electrode fingers when viewed in opposite directions is the excitation region. When the metallization ratio of the multiple electrode fingers relative to the excitation region is defined as MR, the thickness of the piezoelectric layer as d, and the center-to-center distance between adjacent electrode fingers as p, MR ≤ 1.75(d / p) + 0.

075. The support member has an air gap with an opening on the piezoelectric layer side, and the air gap overlaps with at least a portion of the IDT electrode in the thickness direction of the support member. The support member has an inner wall facing the air gap. The elastic wave device further comprises: a high thermal conductivity film, which is directly or indirectly laminated on at least a portion of the second main surface of the piezoelectric layer and extends to the inner sidewall of the support member, wherein the thermal conductivity of the high thermal conductivity film is higher than that of the piezoelectric layer.

21. The elastic wave device according to claim 20, wherein, The support member has the support substrate and a dielectric layer disposed between the support substrate and the piezoelectric layer.

22. The elastic wave device according to claim 21, wherein, The thermal conductivity of at least one of the supporting substrate and the dielectric layer is higher than that of the piezoelectric layer.

23. The elastic wave device according to claim 20, wherein, The support member is composed solely of the support base plate.

24. The elastic wave device according to claim 23, wherein, The thermal conductivity of the support substrate is higher than that of the piezoelectric layer.

25. The elastic wave device according to any one of claims 20 to 24, wherein, An additional film is provided on the second main surface of the piezoelectric layer, the additional film being disposed between the second main surface of the piezoelectric layer and the high thermal conductivity film, the additional film comprising a material with a lower thermal conductivity than the support member.

26. The elastic wave device according to any one of claims 20 to 24, wherein, The inner sidewall is provided with protrusions and recesses.

27. The elastic wave device according to any one of claims 20 to 24, wherein, In the air gap, the support member has a bottom surface opposite to the piezoelectric layer.

28. The elastic wave device according to claim 27, wherein, The high thermal conductivity membrane reaches the bottom surface of the support member located in the air gap.

29. The elastic wave device according to any one of claims 20 to 24, wherein, The air gap is a through hole that passes through the support member.

30. The elastic wave device according to any one of claims 20 to 24, wherein, The high thermal conductivity membrane is a dielectric membrane.

31. The elastic wave device according to any one of claims 20 to 24, wherein, The high thermal conductivity film is formed by ALD (atomic layer deposition) film formation method.

32. The elastic wave device according to claim 31, wherein, The high thermal conductivity film comprises one of aluminum oxide, silicon oxide, silicon nitride, and silicon oxynitride.

33. The elastic wave device according to any one of claims 20 to 24, wherein, The elastic wave device is configured to utilize a body wave with a thickness shear mode.

34. The elastic wave device according to claim 33, wherein, d / p is below 0.

5.

35. The elastic wave device according to claim 34, wherein, d / p is below 0.

24.

36. The elastic wave device according to any one of claims 20 to 24, wherein, The piezoelectric layer is a lithium tantalate layer or a lithium niobate layer.

37. The elastic wave device according to claim 36, wherein, The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate 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) … Equation (3).

38. A method for manufacturing an elastic wave device, comprising: A process for preparing a structure, the structure comprising: a support member including a support substrate; a piezoelectric layer disposed on the support member having opposing first and second main surfaces; and an IDT electrode disposed on the first main surface of the piezoelectric layer, having multiple electrode fingers; an air gap having an opening on the piezoelectric layer side disposed on the support member, the air gap overlapping at least a portion of the IDT electrode in the thickness direction of the support member; the support member having an inner sidewall facing the air gap; and an additional film disposed on the second main surface of the piezoelectric layer, the additional film comprising a material with a lower thermal conductivity than the support member; and The process of forming a high thermal conductivity film containing a material with a higher thermal conductivity than the piezoelectric layer in the air gap of the structure, such that the film extends from the second main surface of the piezoelectric layer to the inner wall of the support member.

39. A method for manufacturing an elastic wave device, comprising: A process for preparing a structure, the structure comprising: a support member including a support substrate; a piezoelectric layer disposed on the support member having a first main surface and a second main surface facing each other; and an IDT electrode disposed on the first main surface of the piezoelectric layer, having a plurality of electrode fingers, wherein the overlapping area of ​​adjacent electrode fingers when viewed in the opposing direction is an excitation region, wherein when the metallization ratio of the plurality of electrode fingers relative to the excitation region is MR, the thickness of the piezoelectric layer is d, and the center-to-center distance between adjacent electrode fingers is p, MR ≤ 1.75(d / p) + 0.075 is satisfied; an air gap having an opening on the piezoelectric layer side is provided on the support member, the air gap overlapping at least a portion of the IDT electrode in the thickness direction of the support member, and the support member having an inner sidewall facing the air gap; and The process of forming a high thermal conductivity film containing a material with a higher thermal conductivity than the piezoelectric layer in the air gap of the structure, such that the film extends from the second main surface of the piezoelectric layer to the inner wall of the support member.

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