Elastic wave device

Abstract

The present application suppresses heat accumulation. The present application includes: a support substrate; a piezoelectric layer provided in a first direction that is a thickness direction of the support substrate, containing lithium niobate or lithium tantalate, and having a main surface in the first direction; a hollow portion provided between the support substrate and the piezoelectric layer; an IDT electrode provided on the main surface of the piezoelectric layer and containing a first bus bar and a second bus bar that face each other, a plurality of first electrode fingers whose base ends are connected to the first bus bar, and a plurality of second electrode fingers whose base ends are connected to the second bus bar; a wiring electrode provided on the main surface of the piezoelectric layer and connected to the IDT electrode; and a high-thermal-conductivity film provided in the piezoelectric layer in the first direction, having a higher thermal conductivity than that of the piezoelectric layer, at least a part of the IDT electrode being provided in a region that overlaps the hollow portion in a plan view in the first direction, the high-thermal-conductivity film being provided in the region that overlaps the hollow portion in the plan view in the first direction, and at least one of the IDT electrode and the wiring electrode being connected to the high-thermal-conductivity film directly or via a metal.

Description

Technical Field

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

[0002] Patent document 1 describes an elastic wave device.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-257019 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the elastic wave device shown in Patent Document 1, heat is generated in the piezoelectric layer due to the excitation of the electrodes. When the piezoelectric layer is stacked on the support substrate with voids in between, the heat dissipation may be poor, resulting in heat accumulation.

[0008] This disclosure is intended to solve the above-mentioned problems and aims to suppress the accumulation of heat.

[0009] Technical solutions for solving the problem

[0010] One embodiment of the elastic wave device includes: a support substrate; a piezoelectric layer disposed in a first direction, which is the thickness direction of the support substrate, comprising lithium niobate or lithium tantalate, having a main surface in the first direction; a void disposed between the support substrate and the piezoelectric layer; an IDT electrode disposed on the main surface of the piezoelectric layer, and including a first busbar and a second busbar facing each other, a plurality of first electrode fingers with base ends connected to the first busbar, and a plurality of second electrode fingers with base ends connected to the second busbar; a wiring electrode disposed on the main surface of the piezoelectric layer and connected to the IDT electrode; and a high thermal conductivity film disposed in the piezoelectric layer in the first direction, having a thermal conductivity higher than that of the piezoelectric layer, wherein at least a portion of the IDT electrode is disposed in a region overlapping the void when viewed from above in the first direction, the high thermal conductivity film is disposed in a region overlapping the void when viewed from above in the first direction, and at least one of the IDT electrode and the wiring electrode is directly or via a metal connected to the high thermal conductivity film.

[0011] Invention Effects

[0012] According to this disclosure, it is possible to suppress the accumulation of heat. Attached Figure Description

[0013] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment.

[0014] Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0015] Figure 2 yes Figure 1A A sectional view of the portion along line II-II.

[0016] Figure 3A This is a schematic cross-sectional view used to illustrate the Ram wave propagating in the piezoelectric layer of the comparative example.

[0017] Figure 3B This is a schematic cross-sectional view used to illustrate the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0018] Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0019] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0020] Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set as p and the average thickness of the piezoelectric layer is set as d in the elastic wave device of the first embodiment.

[0021] Figure 7 This is a top view showing an example of an elastic wave device in the first embodiment having a pair of electrodes.

[0022] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0023] Figure 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the stray impedance, which is normalized by 180 degrees, in the case of a first embodiment of the elastic wave device with a plurality of elastic wave resonators.

[0024] Figure 10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth.

[0025] Figure 11 This is an illustrative 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.

[0026] Figure 12This is a partially cut-off perspective view used to illustrate the elastic wave device involved in the embodiments of this disclosure.

[0027] Figure 13 This is a top view showing an embodiment of the elastic wave device according to the first embodiment.

[0028] Figure 14 It is shown Figure 13 A diagram of an example cross-section along the XIV-XIV line.

[0029] Figure 15 It is shown Figure 13 The first deformed example is a cross-section of the portion along line XIV-XIV.

[0030] Figure 16 It is shown Figure 13 The figure shows the second modified example of the cross section along the XIV-XIV line.

[0031] Figure 17 It is shown Figure 13 The figure shows the third modified example of the cross-section along the XIV-XIV line. Detailed Implementation

[0032] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. However, the present disclosure is not limited to these embodiments. Furthermore, the embodiments described in this disclosure are exemplary, and partial substitutions or combinations of structures can be made between different embodiments. From the modified examples and the second embodiment onwards, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects based on the same structure will not be mentioned repeatedly in each embodiment.

[0033] (First Embodiment)

[0034] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment. Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0035] The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. In the first embodiment, the cutting angle of LiNbO3 and LiTaO3 is Z-cut. The cutting angle of LiNbO3 and LiTaO3 may also be rotational Y-cut or X-cut. Preferably, the propagation orientation is ±30° of Y propagation and X propagation.

[0036] The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the first-order mode of thickness shearing, it is preferably 50 nm or more and 1000 nm or less.

[0037] The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b that are opposite to each other in the Z direction. An electrode 3 and an electrode 4 are disposed on the first main surface 2a.

[0038] Here, electrode 3 is an example of a "first electrode finger," and electrode 4 is an example of a "second electrode finger." Figure 1A as well as Figure 1B In this configuration, multiple electrodes 3 are multiple "first electrode fingers" connected to the first busbar electrode 5. Multiple electrodes 4 are multiple "second electrode fingers" connected to the second busbar electrode 6. The multiple electrodes 3 and multiple electrodes 4 are interleaved and interlocked with each other. Thus, an IDT (Interdigital Transducer) electrode 30 is constructed, comprising multiple electrodes 3, multiple electrodes 4, the first busbar electrode 5, and the second busbar electrode 6.

[0039] Electrodes 3 and 4 are rectangular in shape and have a length direction. Electrode 3 and its adjacent electrode 4 are positioned 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 their length directions, are all directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that electrode 3 and its adjacent electrode 4 are positioned opposite each other in a direction that intersects the thickness direction of the piezoelectric layer 2. In the following description, the thickness direction of the piezoelectric layer 2 is sometimes designated as the Z direction (or the first direction), the length directions of electrodes 3 and 4 as the Y direction (or the second direction), and the direction orthogonal to their length directions as the X direction (or the third direction).

[0040] Furthermore, the length directions of electrodes 3 and 4 can also be aligned with... Figure 1A as well as Figure 1B The directions shown are reversed, being orthogonal to the length directions of electrodes 3 and 4. That is, in Figure 1A as well as Figure 1B Alternatively, electrodes 3 and 4 can extend in the direction in which the first busbar electrode 5 and the second busbar electrode 6 extend. In this case, the first busbar electrode 5 and the second busbar electrode 6 extend in... Figure 1A as well as Figure 1B The electrode 3 and electrode 4 extend in the same direction. Furthermore, multiple pairs of adjacent structures, consisting of an electrode 3 connected to one potential and an electrode 4 connected to another potential, are provided in a direction orthogonal to the length direction of the electrodes 3 and 4.

[0041] Here, "adjacent to electrode 3 and electrode 4" does not mean that electrode 3 and electrode 4 are configured in direct contact, but rather that electrode 3 and electrode 4 are configured with a gap between them. Furthermore, when electrode 3 and electrode 4 are adjacent, no electrodes connected to the signal electrode or ground electrode, including other electrodes 3 and 4, are placed between electrode 3 and electrode 4. The number of pairs does not need to be an integer; it can be 1.5 pairs, 2.5 pairs, etc.

[0042] The center-to-center distance between electrode 3 and electrode 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the center-to-center distance between electrode 3 and electrode 4 is the distance connecting the center of the width dimension of electrode 3 in a direction orthogonal to the length direction of electrode 3 and the center of the width dimension of electrode 4 in a direction orthogonal to the length direction of electrode 4.

[0043] Furthermore, when there are multiple electrodes 3 and 4 (when electrodes 3 and 4 are set as a pair of electrode groups, there are more than 1.5 pairs of electrode groups), the center-to-center distance of electrodes 3 and 4 refers to the average value of the center-to-center distances of adjacent electrodes 3 and 4 in more than 1.5 pairs of electrodes 3 and 4.

[0044] Furthermore, the widths of electrodes 3 and 4, i.e., their dimensions in the opposing directions, are preferably in the range of 150 nm or more and 1000 nm or less. Additionally, the center-to-center distance between electrodes 3 and 4 is defined as the distance connecting the center of the width dimension of electrode 3 in a direction orthogonal to the length direction of electrode 3 and the center of the width dimension of electrode 4 in a direction orthogonal to the length direction of electrode 4.

[0045] Furthermore, in the first embodiment, 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 a limitation if a piezoelectric material with other cut angles 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, 90° ± 10°).

[0046] On the second main surface 2b side of the piezoelectric layer 2, a support substrate 8 is stacked with a dielectric film 7 in between. The dielectric film 7 and the support substrate 8 have a frame-like shape, such as... Figure 2 As shown, it has openings 7a and 8a. As a result, a cavity (air gap) 9 is formed.

[0047] The void 9 is provided so as not to interfere with the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support substrate 8 is laminated on the second main surface 2b with the dielectric film 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 dielectric film 7 may not be provided. Therefore, the support substrate 8 may be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

[0048] The dielectric film 7 is formed of silicon oxide. However, in addition to silicon oxide, the dielectric film 7 can also be formed of suitable insulating materials such as silicon nitride and bauxite.

[0049] The support substrate 8 is formed of Si. The orientation of the surface on the piezoelectric layer 2 side of Si can be (100), (110), or (111). Preferably, it is Si with a high resistivity of 4kΩ or higher. However, the support substrate 8 can also be constructed using suitable insulating materials or semiconductor materials. For example, 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, as well as various ceramics such as diamond, glass, and semiconductors such as gallium nitride can be used.

[0050] The aforementioned electrodes 3, 4, and the first busbar electrode 5 and second busbar electrode 6 comprise suitable metals or alloys such as Al or AlCu alloys. In the first embodiment, electrodes 3, 4, 5, and 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 be used.

[0051] During driving, an alternating voltage is applied between multiple electrodes 3 and multiple electrodes 4. More specifically, an alternating voltage is applied between the first busbar electrode 5 and the second busbar electrode 6. As a result, the resonant characteristics of a bulk wave utilizing the thickness shear first-order mode excited in the piezoelectric layer 2 can be obtained.

[0052] 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 pairs of electrodes 3 and 4 is set as p. In this case, d / p is set to 0.5 or less. Therefore, a bulk wave with a thickness shear first mode can be effectively excited, resulting in good resonance characteristics. More preferably, d / p is 0.24 or less, in which case even better resonance characteristics can be obtained.

[0053] Furthermore, in the case where at least one of the electrodes 3 and 4 is multiple, as in the first embodiment, that is, when the electrodes 3 and 4 are set as a pair of electrode groups and there are 1.5 or more pairs of electrodes 3 and 4, the center-to-center distance p of adjacent electrodes 3 and 4 becomes the average distance between the centers of each adjacent electrode 3 and 4.

[0054] In the elastic wave device 1 of the first embodiment, the above-described structure is provided, so even if the number of pairs of electrodes 3 and 4 is reduced in order to achieve miniaturization, a decrease in the Q value is not easily generated. This is because it is a resonator that does not require reflectors on both sides, resulting in low propagation loss. Furthermore, the reason why the above-described reflectors are not required is because a body wave with a thickness shear first mode is utilized.

[0055] Figure 3A This is a schematic cross-sectional view used to illustrate the Ram wave propagating in the piezoelectric layer of the comparative example. Figure 3B This is a schematic cross-sectional view used to illustrate the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment. Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0056] exist Figure 3A In this case, it is an elastic wave device as described in Patent Document 1, which propagates Lamb waves in a piezoelectric layer. For example... Figure 3A As shown, the wave propagates in the piezoelectric layer 201 as indicated by the arrow. Here, the piezoelectric layer 201 has a first main surface 201a and a second main surface 201b, 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 electrodes 3 and 4 of the IDT electrode 30 are arranged. Figure 3A As shown, if it is a Lamb wave, the wave propagates in the X direction as shown. Because it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates in the X direction. Therefore, reflectors are placed on both sides to obtain resonant characteristics. As a result, wave propagation loss occurs, and the Q value decreases in the pursuit of miniaturization, that is, by reducing the number of pairs of electrodes 3 and 4.

[0057] In contrast, such as Figure 3B As shown, in the elastic wave device of the first embodiment, the vibration displacement is in the thickness shear direction. Therefore, the wave propagates and resonates approximately in the Z direction, which is the direction connecting the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2. 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, a reflector is not required. Therefore, no propagation loss occurs during propagation in a reflector. Thus, even if the number of electrode pairs including electrodes 3 and 4 is reduced to promote miniaturization, a decrease in the Q value is not easily generated.

[0058] In addition, such as Figure 4 As shown, the amplitude direction of the bulk wave of the first-order thickness shear mode is in the excitation region C of the piezoelectric layer 2 (reference). Figure 1B The first region 451 contained in region C and the second region 452 contained in region C become opposite. Figure 4 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.

[0059] In the elastic wave device 1, at least one pair of electrodes, including electrodes 3 and 4, is provided. However, since the wave is not propagated in the X direction, the number of electrode pairs including electrodes 3 and 4 does not necessarily need to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0060] For example, electrode 3 is an electrode connected to a signal potential, and electrode 4 is an electrode connected to a ground potential. However, it is also possible that electrode 3 is connected to a ground potential, and electrode 4 is connected to a signal potential. In the first embodiment, as described above, at least one pair of electrodes is either an electrode connected to a signal potential or an electrode connected to a ground potential, and no floating electrode is provided.

[0061] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. Additionally, [the following is also provided]... Figure 5 The design parameters of the elastic wave device 1 with the resonant characteristics shown are as follows.

[0062] Piezoelectric layer 2: LiNbO3 with Euler angles of (0°, 0°, 90°)

[0063] Thickness of piezoelectric layer 2: 400nm

[0064] Excitation region C (reference) Figure 1B Length: 40μm

[0065] Number of electrode pairs including electrodes 3 and 4: 21 pairs

[0066] Center-to-center distance (split) between electrodes 3 and 4: 3 μm

[0067] Width of electrodes 3 and 4: 500 nm

[0068] d / p: 0.133

[0069] Dielectric film 7: Silicon oxide film with a thickness of 1 μm

[0070] Support substrate 8: Si

[0071] In addition, the so-called incentive region C (refer to) Figure 1B The region C is the area where electrodes 3 and 4 overlap when viewed in the X direction, which is orthogonal to their length directions. The length of the excitation region C is its dimension along the length directions of electrodes 3 and 4.

[0072] In the first embodiment, the distance between the electrodes of the electrode pairs including electrodes 3 and electrodes 4 is set to be equal in all pairs. That is, electrodes 3 and electrodes 4 are arranged at equal intervals.

[0073] according to Figure 5 It is clear that, despite the absence of a reflector, a good resonant characteristic with a relative bandwidth of 12.5% ​​was still achieved.

[0074] 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, in the first embodiment, d / p is 0.5 or less, more preferably 0.24 or less. (Refer to...) Figure 6 This needs to be explained.

[0075] With obtained Figure 5 Similarly, the elastic wave device with the resonant characteristics shown is obtained by changing d / 2p, thus obtaining multiple elastic wave devices. Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set as p and the average thickness of the piezoelectric layer 2 is set as d in the elastic wave device of the first embodiment.

[0076] like Figure 6 As shown, if d / 2p exceeds 0.25, that is, if d / p > 0.5, then even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / 2p ≤ 0.25, that is, when d / p ≤ 0.5, if d / p is varied within this range, the relative bandwidth can be set to 5% or more, that is, a resonator with a high coupling coefficient can be constructed. Furthermore, when d / 2p is 0.12 or less, that is, 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 a wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be achieved. Therefore, it can be seen that, as in the first embodiment, by setting d / p to 0.5 or less, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear first-order mode of the bulk wave can be constructed.

[0077] Alternatively, at least one pair of electrodes can be used, and in the case of one pair of electrodes, p is defined as the center-to-center distance between adjacent electrodes 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, p can simply be defined as the average center-to-center distance between adjacent electrodes 3 and 4.

[0078] Furthermore, regarding the thickness d of the piezoelectric layer 2, even if the piezoelectric layer 2 has a thickness deviation, it is sufficient to use a value that has been averaged over its thickness.

[0079] Figure 7 This is a top view showing an example of an elastic wave device according to the first embodiment, in which a pair of electrodes are provided. In the elastic wave device 101, a pair of electrodes having electrodes 3 and 4 are provided on the first main surface 2a of the piezoelectric layer 2. Furthermore, Figure 7 K in the figure represents the cross width. As previously mentioned, in the elastic wave device of this disclosure, the number of electrode pairs can also be one. In this case, as long as the aforementioned d / p is less than or equal to 0.5, a first-order thickness shear mode of the bulk wave can be effectively excited.

[0080] In the elastic wave device 1, preferably, among the plurality of electrodes 3 and 4, the metallization ratio MR of any adjacent electrodes 3 and 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 and 4 overlap when viewed in opposing directions. In this case, stray emissions can be effectively reduced. (Refer to...) Figure 8 as well as Figure 9 This needs to be explained.

[0081] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. 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.

[0082] Reference Figure 1B The metallization ratio (MR) is explained. Figure 1BIn the electrode configuration, considering only a pair of electrodes 3 and 4, it is assumed that only this pair of electrodes 3 and 4 is provided. In this case, the portion enclosed by the dashed line is called the excitation region C. This excitation region C refers to the overlapping area of ​​electrode 3 with electrode 4, the overlapping area of ​​electrode 4 with electrode 3, and the overlapping area between electrode 3 and electrode 4 when viewed from a direction orthogonal to the length direction of electrodes 3 and 4 (i.e., the opposing direction). Furthermore, the ratio of the area of ​​electrode 3 and electrode 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.

[0083] In addition, when multiple pairs of electrodes 3 and 4 are provided, the ratio of the total area of ​​the metallized portion contained in the entire excitation region C to the total area of ​​the excitation region C can be used as MR.

[0084] Figure 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the stray impedance, which is normalized by 180 degrees and represents the magnitude of the stray, in the case where a plurality of elastic wave resonators are configured in the elastic wave device of the first embodiment. Furthermore, the relative bandwidth was adjusted by various changes to the film thickness of the piezoelectric layer 2 and the dimensions of the electrodes 3 and 4. In addition, Figure 9 This is the result when using piezoelectric layer 2 with Z-cut LiNbO3, but the same tendency occurs even when using piezoelectric layer 2 with other cut angles.

[0085] exist Figure 9 In the region enclosed by ellipse J, the stray energy increases to 1.0. According to... Figure 9 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 8 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 thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, etc.

[0086] Figure 10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth. In the elastic wave device 1 of the first embodiment, various elastic wave devices 1 with different d / 2p and MR were constructed, and the relative bandwidth was measured. Figure 10The 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 10 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 set to below 17%.

[0087] Figure 11 This is an illustrative 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 11 The area shown by the shading is the region where a relative bandwidth of at least 5% can be obtained. If the range of the region is approximated, it becomes the range represented by the following equations (1), (2) and (3).

[0088] (0°±10°, 0°~20°, any ψ)…Equation (1)

[0089] (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)

[0090] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ)…Equation (3)

[0091] Therefore, within the range of Euler angles in equations (1), (2), or (3) above, it is preferable to be able to sufficiently expand the relative bandwidth.

[0092] Figure 12 This is a partially cut-off perspective view used to illustrate the elastic wave device according to embodiments of this disclosure. Figure 12 In the diagram, the outer periphery of the cavity 9 is shown by a dashed line. The elastic wave device of this disclosure can also utilize plate waves. In this case, such as... Figure 12As shown, the elastic wave device 301 includes reflectors 310 and 311. Reflectors 310 and 311 are disposed on both sides of the electrodes 3 and 4 of the piezoelectric layer 2 in the direction of elastic wave propagation. In the elastic wave device 301, by applying an alternating electric field to the electrodes 3 and 4 on the cavity portion 9, a Lamb wave, which is a plate wave, can be excited. At this time, because reflectors 310 and 311 are disposed on both sides, resonance characteristics based on the Lamb wave as a plate wave can be obtained.

[0093] As explained above, in elastic wave devices 1 and 101, a first-order mode of thickness shearing is utilized for bulk waves. Furthermore, in elastic wave devices 1 and 101, electrodes 3 and 4 are adjacent to each other, and when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between electrodes 3 and 4 is set to p, d / p is set to 0.5 or less. Therefore, even when miniaturizing the elastic wave device, the Q value can be improved.

[0094] In the elastic wave devices 1 and 101, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. Preferably, on the first main surface 2a or the second main surface 2b of the piezoelectric layer 2, there are electrodes 3 and 4, which are opposite each other in a direction intersecting the thickness direction of the piezoelectric layer 2, and a protective film is covered on top of the electrodes 3 and 4.

[0095] Figure 13 This is a top view showing an embodiment of the elastic wave device according to the first embodiment. Figure 14 It is shown Figure 13 A diagram showing an example of a cross-section along the XIV-XIV line. (See diagram for example.) Figure 14 As shown, the elastic wave device 1A according to the first embodiment also includes a high thermal conductivity film 11. Furthermore, as... Figure 13 As shown, a wiring electrode 12 is connected to the IDT electrode 30, and a through hole 10 is provided in the piezoelectric layer 2.

[0096] In the first embodiment, the piezoelectric layer 2 includes a first piezoelectric body 21 and a second piezoelectric body 22. In this case, the thickness d of the piezoelectric layer 2 refers to the distance between the first main surface 2a and the second main surface 2b in the Z direction. The first piezoelectric body 21 is a piezoelectric body having a first main surface 2a. The second piezoelectric body 22 is a piezoelectric body having a second main surface 2b, and is stacked on top of the first piezoelectric body 21 in the Z direction. Furthermore, the first piezoelectric body 21 and the second piezoelectric body 22 are made of the same material.

[0097] The high thermal conductivity film 11 is a heat dissipation layer disposed within the piezoelectric layer 2 in the Z direction. In the first embodiment, the high thermal conductivity film 11 is configured to be sandwiched between the piezoelectric layer 2 in the Z direction. Figure 14In this example, a high thermal conductivity film 11 is disposed between the first piezoelectric element 21 and the second piezoelectric element 22 of the piezoelectric layer 2. The high thermal conductivity film 11 has higher thermal conductivity than the piezoelectric layer 2, and is preferably used as a bonding layer between the first piezoelectric element 21 and the second piezoelectric element 22 in the manufacture of the elastic wave device 1A described later. The high thermal conductivity film 11 can contain, for example, bauxite, silicon nitride, and aluminum nitride, as well as silicon oxide.

[0098] The wiring electrode 12 is an electrode disposed on the first main surface 2a. In the first embodiment, multiple wiring electrodes 12 are disposed and electrically connected to the busbar electrodes 5 and 6 of the IDT electrode 30, respectively. Like the IDT electrode 30, the wiring electrode 12 can contain a suitable metal or alloy.

[0099] In the first embodiment, the IDT electrode 30 is connected to the high thermal conductivity film 11. Figure 14 In the example, the busbar electrodes 5 and 6 in the IDT electrode 30 penetrate the first piezoelectric element 21 in the Z direction and are in direct contact with the high thermal conductivity film 11. By configuring it in this way, the heat generated by the excitation of the IDT electrode 30 can be dissipated to the high thermal conductivity film 11.

[0100] The through-hole 10 is a hole that penetrates the piezoelectric layer 2 in the Z direction. The through-hole 10 is located at a position overlapping the cavity 9 when viewed from above in the Z direction, and communicates with the cavity 9 in the Z direction. Therefore, the cavity 9 can be easily formed during the manufacture of the elastic wave device 1A, which will be described later. Furthermore, in Figure 13 In the example, the through hole 10 is rectangular when viewed from above in the Z direction, and there are two holes at both ends in the X direction of the cavity 9. However, this is just an example, and it can be set to any shape, and the number is not limited to this.

[0101] Hereinafter, an example of a manufacturing method for the elastic wave device 1A according to the first embodiment will be described. However, the manufacturing method for the elastic wave device 1A is not limited to the following method.

[0102] First, voids 9 are formed on a flat support substrate 8 by resist patterning, dry etching, and resist removal. Next, a sacrificial layer is formed in the voids 9 of the support substrate 8, and the sacrificial layer is embedded by surface grinding. Then, a dielectric film 7 is formed on the sacrificial layer side of the support substrate 8 as a bonding layer, and it is bonded to a second piezoelectric substrate on which a dielectric film 7 is also formed. After bonding, the second piezoelectric substrate is thinned by grinding to become a second piezoelectric body 22. Similarly, a high thermal conductivity film 11 is formed on the second piezoelectric body 22 as a bonding layer, and it is bonded to a first piezoelectric substrate on which a high thermal conductivity film 11 is formed. The first piezoelectric substrate after bonding is thinned by grinding to become a first piezoelectric body 21.

[0103] exist Figure 14 In this example, resist patterning and dry etching are further performed on the first main surface 2a of the piezoelectric layer 2 to form an opening in a portion of the first piezoelectric body 21. On the first main surface 2a, an IDT electrode 30 and a wiring electrode 12 are formed by stripping.

[0104] After forming the electrodes, the first main surface 2a is protected by resist patterning. Then, the first piezoelectric element 21, the high thermal conductivity film 11, the second piezoelectric element 22, and the dielectric film 7 are etched to form a through-hole 10. In this state, the resist is temporarily removed and surface protection based on resist patterning is performed again. By removing a portion of the sacrificial layer and the dielectric film 7, a void 9 is formed. Then, by removing the resist, the elastic wave device 1A according to the first embodiment is manufactured.

[0105] The elastic wave device 1A according to the first embodiment has been described above, but the structure of the elastic wave device is not limited to this. Figure 14 The example shown.

[0106] For example, the high thermal conductivity film 11 is not limited to a layer disposed in the Z direction between the first piezoelectric body 21 and the second piezoelectric body 22, but may also be a layer contained within the piezoelectric layer 2. That is, although in Figure 14 In the example, the high thermal conductivity film 11 is exposed in both the X and Y directions, but it can also be located within the piezoelectric layer 2 in any direction.

[0107] Furthermore, the IDT electrode 30 is not limited to direct contact with the high thermal conductivity film 11; it can also be connected to the high thermal conductivity film 11 via other metal components such as the wiring electrode 12. Hereinafter, variations in the connection method between the IDT electrode 30 and the high thermal conductivity film 11 will be described using the accompanying drawings. Additionally, in the following description, regarding the connection with… Figure 13 as well as Figure 14 The embodiments shown have the same structure, are labeled with the same reference numerals, and descriptions are omitted.

[0108] Figure 15 It is shown Figure 13 A diagram of the first deformed example of a cross-section along line XIV-XIV. (See diagram for reference.) Figure 15As shown, the IDT electrode 30 can also be connected to the high thermal conductivity film 11 via the through electrode 13. The through electrode 13 is an electrode whose end in the Z direction is connected to either the IDT electrode 30 or the wiring electrode 12. In the elastic wave device 1B according to the first modification, the through electrode 13 is disposed at a position overlapping the wiring electrode 12 when viewed from above in the Z direction, and is configured to pass through the wiring electrode 12, the piezoelectric layer 2, the high thermal conductivity film 11, the dielectric film 7, and the support substrate 8 in the Z direction. With this configuration, the heat generated by the excitation of the IDT electrode 30 can be dissipated to the high thermal conductivity film 11 via the through electrode 13. In addition, like the IDT electrode 30, the through electrode 13 can contain a suitable metal or alloy.

[0109] Figure 16 It is shown Figure 13 The second deformed example is shown in the cross-section of the portion along line XIV-XIV. (See figure.) Figure 16 As shown, the through electrode 13 only needs to contact the IDT electrode 30 or the wiring electrode 12 and the high thermal conductivity film 11, or it can only penetrate the piezoelectric layer 2. Even in the elastic wave device 1C according to the second modification, the heat generated by the excitation of the IDT electrode 30 can be dissipated to the high thermal conductivity film 11 through the through electrode 13.

[0110] Figure 17 It is shown Figure 13 The figure shows a third modified example of a cross-section along line XIV-XIV. The IDT electrode 30 can also be connected to the high thermal conductivity film 11 via a metal member that does not penetrate the piezoelectric layer 2. In the elastic wave device 1D according to the third modified example, the metal member that does not penetrate the piezoelectric layer 2 is, for example, a side electrode 14. The side electrode 14 is an electrode disposed on a surface parallel to the Z direction of both the piezoelectric layer 2 and the dielectric film 7. Figure 17 As shown, the side electrode 14 is connected to the wiring electrode 12 via one end in the Z direction. This configuration allows heat generated by the excitation of the IDT electrode 30 to be dissipated to the high thermal conductivity film 11 via the side electrode 14. Furthermore, like the IDT electrode 30, the side electrode 14 can also contain a suitable metal or alloy.

[0111] As described above, the elastic wave devices 1A to 1D according to the first embodiment include: a support substrate 8; a piezoelectric layer 2, disposed in a first direction which is the thickness direction of the support substrate 8, comprising lithium niobate or lithium tantalate, and having a first main surface 2a in the first direction; a void portion 9, disposed between the support substrate 8 and the piezoelectric layer 2; an IDT electrode 30, disposed in the first main surface 2a of the piezoelectric layer 2, and including a first busbar electrode 5 and a second busbar electrode 6 facing each other, a plurality of electrodes 3 whose base ends are connected to the first busbar electrode 5, and a base end. Multiple electrodes 4 connected to the second busbar electrode 6; wiring electrode 12 disposed on the first main surface 2a of the piezoelectric layer 2 and connected to the IDT electrode 30; and a high thermal conductivity film 11 disposed in the piezoelectric layer 2 in the first direction, having a thermal conductivity higher than that of the piezoelectric layer 2, at least a portion of the IDT electrode 30 being disposed in the region overlapping with the void portion 9 when viewed from above in the first direction, the high thermal conductivity film 11 being disposed in the region overlapping with the void portion 9 when viewed from above in the first direction, and the IDT electrode 30 being directly or via a metal connected to the high thermal conductivity film 11.

[0112] Therefore, the heat generated by the excitation of the IDT electrode 30 can be released to the high thermal conductivity film 11, thus suppressing heat accumulation.

[0113] As a preferred embodiment, the high thermal conductivity film 11 preferably comprises at least one of bauxite, silicon nitride, and aluminum nitride. This improves the thermal conductivity of the high thermal conductivity film 11 and further suppresses heat accumulation.

[0114] As a preferred embodiment, the high thermal conductivity film 11 preferably comprises silicon oxide. This improves the thermal conductivity of the high thermal conductivity film 11 and further suppresses heat accumulation.

[0115] Alternatively, the high thermal conductivity membrane 11 may also be disposed in a region that does not overlap with the void portion 9 when viewed from above in the first direction. Even in this case, heat accumulation can be suppressed.

[0116] Alternatively, it may also include a through electrode 13 that penetrates the piezoelectric layer 2, and the through electrode 13 is in contact with at least one of the IDT electrode 30 and the wiring electrode 12 and the high thermal conductivity film 11. Thus, the IDT electrode 30 can release heat to the high thermal conductivity film 11 via the through electrode 13, thereby suppressing heat accumulation.

[0117] As a preferred embodiment, the through electrode 13 penetrates the high thermal conductivity film 11. Therefore, the IDT electrode 30 can more reliably release heat to the high thermal conductivity film 11 via the through electrode 13, thus further suppressing heat accumulation.

[0118] As a more preferred embodiment, a dielectric film 7 is further provided between the support substrate 8 and the piezoelectric layer 2, and the through electrode 13 contacts the dielectric film 7. Thus, in the manufacture of the elastic wave device 1A, the piezoelectric layer 2 can be bonded to the support substrate 8 via the dielectric film 7, thereby making it easy to manufacture the elastic wave device 1A.

[0119] In a more preferred manner, the through electrode 13 is in contact with the support substrate 8. As a result, the IDT electrode 30 can also release heat to the support substrate 8 through the through electrode 13, thereby further suppressing heat accumulation.

[0120] Alternatively, the piezoelectric layer 2 may also include a side electrode 14 disposed on a surface parallel to the first direction, which contacts the wiring electrode 12 and the high thermal conductivity film 11. Thus, the IDT electrode 30 can release heat to the high thermal conductivity film 11 via the wiring electrode 12 and the side electrode 14, thereby further suppressing heat accumulation.

[0121] Preferably, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between adjacent electrodes 3 and 4 is set to p, d / p is 0.5 or less. This allows for miniaturization of the elastic wave device 1 and improves the Q value.

[0122] As a further preferred approach, the Euler angles of lithium niobate or lithium tantalate constituting the piezoelectric layer 2 are... It falls within the range of equation (1), equation (2), or equation (3) below. In this case, the relative bandwidth can be sufficiently expanded.

[0123] (0°±10°, 0°~20°, any ψ)…Equation (1)

[0124] (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)

[0125] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ)…Equation (3)

[0126] As a further preferred embodiment, the elastic wave device 1 is configured to utilize a bulk wave with a thickness shear mode. This increases the coupling coefficient and results in good resonance characteristics.

[0127] As a further preferred embodiment, d / p is 0.24 or less. This allows for miniaturization of the elastic wave device 1 and improves the Q value.

[0128] As a further preferred embodiment, the region where adjacent electrodes 3 and 4 overlap in the opposite direction is the excitation region C. When the metallization ratio of the multiple electrodes 3 and 4 relative to the excitation region C is set as MR, MR ≤ 1.75(d / p) + 0.075 is satisfied. In this case, the relative bandwidth can be reliably made to be less than 17%.

[0129] As a preferred embodiment, the elastic wave device 1 is configured to utilize plate waves. This allows for the acquisition of excellent resonance characteristics.

[0130] Furthermore, the above-described embodiments are intended to facilitate understanding of this disclosure and are not intended to limit its interpretation. This disclosure can be modified / improved without departing from its spirit, and it also includes equivalents.

[0131] Explanation of reference numerals in the attached figures

[0132] 1. 1A~1D, 101, 301: Elastic wave device;

[0133] 2: Piezoelectric layer;

[0134] 2a: First main face;

[0135] 2b: Second main face;

[0136] 3: Electrode (referring to the first electrode);

[0137] 4: Electrode (referring to the second electrode);

[0138] 5: Busbar electrode (first busbar electrode);

[0139] 6: Busbar electrode (second busbar electrode);

[0140] 7: Dielectric film;

[0141] 8: Support base plate;

[0142] 7a, 8a: Openings;

[0143] 9: Hollow section;

[0144] 10: Through hole;

[0145] 11: High thermal conductivity membrane;

[0146] 12: Wiring electrodes;

[0147] 13: Through electrode;

[0148] 14: Side electrode;

[0149] 21: The first piezoelectric element;

[0150] 22: Second piezoelectric element;

[0151] 30: IDT electrode;

[0152] 201: Piezoelectric layer;

[0153] 201a: 1st main surface;

[0154] 201b: Second main face;

[0155] 310, 311: Reflectors;

[0156] 451: Region 1;

[0157] 452: Region 2;

[0158] C: Incentive region;

[0159] VP1: Imaginary plane.

Claims

1. An elastic wave device, comprising: support base plate; A piezoelectric layer, disposed in a first direction which is the thickness direction of the support substrate, comprises lithium niobate or lithium tantalate, and has a main surface in the first direction; A void is disposed between the supporting substrate and the piezoelectric layer; An IDT electrode is disposed on the main surface of the piezoelectric layer and includes a first busbar and a second busbar that are opposite to each other, a plurality of first electrode fingers whose base ends are connected to the first busbar, and a plurality of second electrode fingers whose base ends are connected to the second busbar. A wiring electrode is disposed on the main surface of the piezoelectric layer and connected to the IDT electrode; as well as A high thermal conductivity film, disposed within the piezoelectric layer in the first direction, has a thermal conductivity higher than that of the piezoelectric layer. At least a portion of the IDT electrode is disposed in the region that overlaps with the cavity when viewed from above in the first direction. The high thermal conductivity membrane is disposed in the region that overlaps with the void portion when viewed from above in the first direction. The IDT electrode is connected to the high thermal conductivity film directly or via a metal.

2. The elastic wave device according to claim 1, wherein, The high thermal conductivity membrane comprises at least one of bauxite, silicon nitride, and aluminum nitride.

3. The elastic wave device according to claim 1, wherein, The high thermal conductivity film contains silicon oxide.

4. The elastic wave device according to any one of claims 1 to 3, wherein, The high thermal conductivity membrane is also disposed in a region that does not overlap with the cavity when viewed from above in the first direction.

5. The elastic wave device according to any one of claims 1 to 4, wherein, It also has a through electrode that penetrates the piezoelectric layer. The through electrode is in contact with at least one of the IDT electrode and the wiring electrode and the high thermal conductivity film.

6. The elastic wave device according to claim 5, wherein, The through electrode penetrates the high thermal conductivity membrane.

7. The elastic wave device according to claim 6, wherein, A dielectric film is also provided between the supporting substrate and the piezoelectric layer. The through electrode is in contact with the dielectric film.

8. The elastic wave device according to claim 6 or 7, wherein, The through electrode is in contact with the supporting substrate.

9. The elastic wave device according to any one of claims 1 to 5, wherein, It also includes: a side electrode disposed on a surface of the piezoelectric layer that is parallel to the first direction. The side electrode is in contact with the wiring electrode and the high thermal conductivity film.

10. The elastic wave device according to any one of claims 1 to 9, wherein, The thickness of the piezoelectric layer is set as d, and the center-to-center distance between adjacent first electrode fingers and second electrode fingers is set as p. In this case, d / p is less than 0.

5.

11. The elastic wave device according to any one of claims 1 to 10, wherein, Euler angles of lithium niobate or lithium tantalate constituting the piezoelectric layer It falls 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).

12. The elastic wave device according to claim 10 or 11, wherein, The elastic wave device is configured to utilize a body wave with a thickness shear mode.

13. The elastic wave device according to any one of claims 10 to 12, wherein, d / p is below 0.

24.

14. The elastic wave device according to any one of claims 10 to 13, wherein, The area where adjacent first electrode fingers and second electrode fingers overlap when viewed in opposite directions is the excitation region. When the metallization ratio of the plurality of first electrode fingers and second electrode fingers relative to the excitation region is set as MR, MR≤1.75(d / p)+0.075 is satisfied.

15. The elastic wave device according to any one of claims 1 to 9, wherein, The elastic wave device is configured to utilize plate waves.

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