Elastic wave device

Abstract

Suppressing crack formation in the piezoelectric layer. An elastic wave device includes: a support substrate having a thickness in a first direction; a piezoelectric layer disposed in the first direction of the support substrate; and an IDT electrode disposed in the piezoelectric layer, having a plurality of first electrode fingers and a plurality of second electrode fingers, the plurality of first electrode fingers extending in a second direction intersecting the first direction, the plurality of second electrode fingers opposing any one of the plurality of first electrode fingers in a third direction orthogonal to the second direction and extending in the second direction; a void portion is provided between the support substrate and the piezoelectric layer at a location where at least a portion overlaps with the IDT electrode in the first direction; at least one through-hole penetrating the piezoelectric layer is provided at a location where it does not overlap with the IDT electrode in the first direction relative to the IDT electrode, the through-hole communicating with the void portion; and a reinforcing strut extending in the first direction is provided within the void portion in a region where it does not overlap with the plurality of first electrode fingers and the plurality of second electrode fingers in the first direction but overlaps with the void portion.

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 Patent Document 1, when a void is provided between the support substrate and the piezoelectric layer, cracks may occur in the piezoelectric layer due to stray generation. Therefore, it is desirable to suppress the generation of cracks in the piezoelectric layer.

[0008] This disclosure is intended to solve the above-mentioned problems and aims to provide an elastic wave device that suppresses the generation of cracks in the piezoelectric layer.

[0009] means for solving problems

[0010] One aspect of the elastic wave device includes: a support substrate having a thickness in a first direction; a piezoelectric layer disposed in the first direction of the support substrate; and an IDT electrode disposed in the piezoelectric layer having a plurality of first electrode fingers and a plurality of second electrode fingers, the plurality of first electrode fingers extending in a second direction intersecting the first direction, the plurality of second electrode fingers opposing any one of the plurality of first electrode fingers in a third direction orthogonal to the second direction and extending in the second direction; a cavity is provided between the support substrate and the piezoelectric layer at a location where at least a portion overlaps with the IDT electrode in the first direction; at least one through hole penetrating the piezoelectric layer is provided at a location where it does not overlap with the IDT electrode in the first direction relative to the IDT electrode, the through hole communicating with the cavity; and a reinforcing strut extending in the first direction is provided within the cavity in a region where it does not overlap with the plurality of first electrode fingers and the plurality of second electrode fingers in the first direction but overlaps with the cavity.

[0011] Another embodiment of the elastic wave device includes: a support substrate having a thickness in a first direction; a piezoelectric layer disposed in the first direction of the support substrate; and an IDT electrode disposed in the piezoelectric layer having a plurality of first electrode fingers and a plurality of second electrode fingers, the plurality of first electrode fingers extending in a second direction intersecting the first direction, the plurality of second electrode fingers opposing any one of the plurality of first electrode fingers in a third direction orthogonal to the second direction and extending in the second direction; a cavity is provided between the support substrate and the piezoelectric layer at a location where at least a portion overlaps with the IDT electrode in the first direction; at a location where the IDT electrode does not overlap with the IDT electrode in the first direction, at least one through hole penetrating the piezoelectric layer is provided, the through hole communicating with the cavity; the elastic wave device has a reinforcing rib that does not overlap with the plurality of first electrode fingers and the plurality of second electrode fingers in the first direction and protrudes from the sidewall of the cavity into the cavity.

[0012] Invention Effects

[0013] According to this disclosure, it is possible to suppress the generation of cracks in the piezoelectric layer. Attached Figure Description

[0014] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment.

[0015] Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0016] Figure 2 It is along Figure 1A A sectional view of the portion along line II-II.

[0017] Figure 3A This is a schematic cross-sectional view used to illustrate the Lamb wave propagating in the piezoelectric layer of the comparative example.

[0018] Figure 3B This is a schematic cross-sectional view used to illustrate the first-order thickness shear mode of a bulk wave propagating in the piezoelectric layer of the first embodiment.

[0019] Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of a bulk wave in the thickness shear first-order mode propagating in the piezoelectric layer of the first embodiment.

[0020] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0021] Figure 6This is an explanatory diagram showing the relationship between d / 2p and the fractional bandwidth of the resonator when the center-to-center distance or the average center-to-center distance between 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.

[0022] Figure 7 This is a top view showing an example of an elastic wave device in the first embodiment having a pair of electrodes.

[0023] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0024] Figure 9 This is an explanatory diagram showing the relationship between the fractional bandwidth of the elastic wave device of the first embodiment, which consists of a plurality of elastic wave resonators, and the amount of phase rotation of the spurious impedance normalized to 180 degrees as the magnitude of the spurious signal.

[0025] Figure 10 This is an explanatory graph showing the relationship between d / 2p, metallization ratio (MR), and fractional bandwidth.

[0026] Figure 11 This is an illustrative diagram showing the mapping of the fractional bandwidth relative to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p approaches 0 infinitely.

[0027] Figure 12 This is a partially cutaway perspective view used to illustrate the elastic wave device involved in the embodiments of the present invention.

[0028] Figure 13A This is a top view showing a first embodiment of the elastic wave device according to the first embodiment.

[0029] Figure 13B It is along Figure 13A A sectional view of the BB line portion.

[0030] Figure 13C It is along Figure 13A A sectional view of the CC line portion.

[0031] Figure 14 This is a top view showing a second embodiment of the elastic wave device according to the first embodiment.

[0032] Figure 15 This is a top view showing a third embodiment of the elastic wave device according to the first embodiment.

[0033] Figure 16 This is a top view showing a fourth embodiment of the elastic wave device according to the first embodiment.

[0034] Figure 17A This is a top view showing the fifth embodiment of the elastic wave device according to the first embodiment.

[0035] Figure 17B It is along Figure 17A A sectional view of the BB line portion.

[0036] Figure 17C It is along Figure 17A A sectional view of the CC line portion.

[0037] Figure 18A This is a top view showing the sixth embodiment of the elastic wave device according to the first embodiment.

[0038] Figure 18B It is along Figure 18A A sectional view of the BB line portion.

[0039] Figure 18C It is along Figure 18A A sectional view of the CC line portion.

[0040] Figure 19A This is a top view showing an embodiment of the elastic wave device according to the second embodiment.

[0041] Figure 19B It is along Figure 19A A sectional view of the BB line portion.

[0042] Figure 19C It is along Figure 19A A sectional view of the CC line portion. Detailed Implementation

[0043] 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 illustrative, 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 explained. In particular, the same effects resulting from the same structure are not mentioned in each embodiment.

[0044] (First Embodiment)

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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. Electrode fingers 3 and 4 are provided on the first main surface 2a.

[0049] Here, electrode finger 3 is an example of "first electrode finger," and electrode finger 4 is an example of "second electrode finger." Figure 1A as well as Figure 1B In this configuration, multiple electrode fingers 3 are connected to the first bus bar 5. Multiple electrode fingers 4 are connected to the second bus bar 6. The multiple electrode fingers 3 and multiple electrode fingers 4 are interleaved and interlocked. Accordingly, an IDT electrode is constructed having electrode fingers 3, electrode fingers 4, the first bus bar 5, and the second bus bar 6.

[0050] Electrode fingers 3 and 4 have a rectangular shape and a length direction. Electrode finger 3 and its adjacent electrode finger 4 are positioned opposite each other in a direction orthogonal to this length direction. The length directions of electrode fingers 3 and 4, as well as the directions orthogonal to their length directions, intersect the thickness direction of the piezoelectric layer 2. Therefore, electrode fingers 3 and their adjacent electrode fingers 4 can also be described as being opposite each other in a direction intersecting the thickness direction of the piezoelectric layer 2. In the following description, the thickness direction of the piezoelectric layer 2 may sometimes be defined as the Z direction (or the first direction), the direction orthogonal to the length directions of electrode fingers 3 and 4 as the X direction (or the third direction), and the length directions of electrode fingers 3 and 4 as the Y direction (or the second direction).

[0051] In addition, the length direction of electrode finger 3 and electrode finger 4 can also be... Figure 1A as well as Figure 1B The directions shown are interchanged with those orthogonal to the length directions of electrode fingers 3 and 4. That is, electrode fingers 3 and 4 can also be positioned along... Figure 1A as well as Figure 1B 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 along... Figure 1A as well as Figure 1BThe middle electrode finger 3 and electrode finger 4 extend in the direction of extension. Moreover, there are multiple pairs of structures with an electrode finger 3 connected to one potential and an electrode finger 4 connected to another potential, arranged in a direction orthogonal to the length direction of the electrode fingers 3 and 4.

[0052] Here, the phrase "electrode 3 and electrode 4 are adjacent" does not mean that electrode 3 and electrode 4 are directly in contact, but rather that electrode 3 and electrode 4 are positioned with a gap between them. Furthermore, when electrode 3 and electrode 4 are adjacent, there are no electrodes (including other electrodes 3 and 4) connected to the signal electrode or ground electrode 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.

[0053] The center-to-center distance, or spacing, between electrode fingers 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the center-to-center distance between electrode fingers 3 and 4 is defined as the distance connecting the center of the width dimension of electrode finger 3 in a direction orthogonal to the length direction of electrode finger 3 and the center of the width dimension of electrode finger 4 in a direction orthogonal to the length direction of electrode finger 4.

[0054] Furthermore, when there are multiple electrode fingers 3 and 4 (when electrode fingers 3 and 4 are set as a pair of electrode groups, there are 1.5 or more pairs of electrode groups), the center-to-center distance of electrode fingers 3 and 4 refers to the average center-to-center distance of adjacent electrode fingers 3 and 4 in 1.5 or more pairs of electrode fingers 3 and 4.

[0055] Furthermore, the width of electrode fingers 3 and 4, i.e., the dimension of electrode fingers 3 and 4 in the opposing direction, is preferably in the range of 150 nm or more and 1000 nm or less. Additionally, the center-to-center distance between electrode fingers 3 and 4 is defined as 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.

[0056] Furthermore, in the first embodiment, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of electrode fingers 3 and 4 becomes the direction orthogonal to the polarization direction of piezoelectric layer 2. This is not limited to cases where a piezoelectric material with 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 electrode fingers 3 and 4 and the polarization direction is, for example, 90° ± 10°).

[0057] 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. Accordingly, a cavity (air gap) 9 is formed.

[0058] 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 on which at least one pair of electrode fingers 3 and electrode fingers 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.

[0059] 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.

[0060] The support substrate 8 is formed of Si. The orientation of the face on the piezoelectric layer 2 side of Si can be (100), (110), or (111). Preferably, Si with a high resistivity of 4kΩ or higher is preferred. However, the support substrate 8 can also be constructed using suitable insulating or semiconductor materials. For example, materials such as piezoelectric materials like 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, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.

[0061] 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 the first 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.

[0062] During driving, an alternating voltage is applied between multiple electrode fingers 3 and multiple electrode fingers 4. More specifically, an alternating voltage is applied between the first bus bar 5 and the second bus bar 6. Accordingly, the resonant characteristics of a bulk wave utilizing the thickness shear first-order mode excited in the piezoelectric layer 2 can be obtained.

[0063] 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 pairs of electrode fingers 3 and 4 is set to p, d / p is set to 0.5 or less. Therefore, the bulk wave of the aforementioned thickness shear first-order 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.

[0064] Furthermore, as in the first embodiment, when at least one of the electrode fingers 3 and 4 has multiple fingers, that is, when the electrode fingers 3 and 4 are set as a pair of electrode groups and there are 1.5 or more pairs of electrode fingers 3 and 4, the center-to-center distance p of adjacent electrode fingers 3 and 4 becomes the average distance between the centers of each adjacent electrode finger 3 and 4.

[0065] In the elastic wave device 1 of the first embodiment, because it has the above-described structure, even if the number of pairs of electrode fingers 3 and 4 is reduced 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 absence of the aforementioned reflectors is due to the utilization of a body wave with a thickness shear first-order mode.

[0066] Figure 3A This is a schematic cross-sectional view used to illustrate the Lamb wave propagating in the piezoelectric layer of the comparative example. Figure 3B This is a schematic cross-sectional view used to illustrate the first-order thickness shear mode of a bulk wave 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 a bulk wave in the thickness shear first-order mode propagating in the piezoelectric layer of the first embodiment.

[0067] exist Figure 3A In this case, it is an elastic wave device as described in Patent Document 1, in which Lamb waves propagate 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 the electrode fingers 3 and 4 of the IDT electrodes are arranged. Figure 3A As shown, for a Lamb wave, the wave propagates continuously in the X direction as illustrated. Because it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates in the X direction. Therefore, by placing reflectors on both sides, a resonant characteristic is obtained. Consequently, wave propagation loss occurs, and the Q value decreases when miniaturization is achieved, i.e., when the number of logarithms of electrode fingers 3 and 4 is reduced.

[0068] In contrast, such as Figure 3BAs shown, in the elastic wave device of the first embodiment, since the vibration displacement is in the thickness shear direction, 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 resonant characteristics can be obtained through the propagation of the wave in this Z-direction, a reflector is not required. Therefore, no propagation loss occurs when propagating to a reflector. Thus, even if the number of electrode pairs, including electrode fingers 3 and electrode fingers 4, is reduced to promote miniaturization, it is not easy to cause a decrease in the Q value.

[0069] In addition, such as Figure 4 As shown, the amplitude direction of the bulk wave in the first-order thickness shear mode is in the excitation region C of the piezoelectric layer 2 (reference). Figure 1B The first region 451 and the second region 452 included in the excitation region C become opposite. Figure 4 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 in excitation region C between a virtual plane VP1 orthogonal to the thickness direction of piezoelectric layer 2 and dividing piezoelectric layer 2 into two parts, and the first main surface 2a. The second region 452 is the region in excitation region C between the virtual plane VP1 and the second main surface 2b.

[0070] In the elastic wave device 1, at least one pair of electrodes, including electrode fingers 3 and electrode fingers 4, is provided. However, the wave is not propagated in the X direction, so the number of electrode pairs including electrode fingers 3 and electrode fingers 4 does not necessarily need to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0071] For example, electrode 3 is an electrode connected to the signal potential, and electrode 4 is an electrode connected to the ground potential. However, electrode 3 can also be connected to the ground potential, and electrode 4 can be connected to the signal potential. In the first 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.

[0072] 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, we obtain... Figure 5 The design parameters of the elastic wave device 1 with the resonant characteristics shown are as follows.

[0073] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°)

[0074] Thickness of piezoelectric layer 2: 400nm

[0075] Excitation region C (reference) Figure 1B Length: 40μm

[0076] Number of electrode pairs including electrode fingers 3 and 4: 21 pairs

[0077] Center-to-center distance (split) between electrode finger 3 and electrode finger 4: 3 μm

[0078] Width of electrode finger 3 and electrode finger 4: 500nm

[0079] d / p: 0.133

[0080] Dielectric film 7: 1μm thick silicon oxide film

[0081] Support substrate 8: Si

[0082] In addition, the so-called incentive region C (refer to) Figure 1B The region C is the overlapping area of ​​electrode fingers 3 and 4 when viewed in the X direction, which is orthogonal to the length directions of electrode fingers 3 and 4. The length of the excitation region C is the dimension of the excitation region C along the length directions of electrode fingers 3 and 4.

[0083] In the first embodiment, the distance between the electrodes of the electrode pairs, including electrode fingers 3 and electrode fingers 4, is set to be equal in all pairs. That is, the electrode fingers 3 and electrode fingers 4 are arranged at equal intervals.

[0084] As from Figure 5 As can be clearly seen, despite the absence of a reflector, a good resonant characteristic with a fractional bandwidth of 12.5% ​​was obtained.

[0085] 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, 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.

[0086] With obtained Figure 5 Similarly, by varying d / 2p, multiple elastic wave devices were obtained, based on the resonant characteristics of the elastic wave device shown. Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the fractional bandwidth of the resonator when the average distance between the centers of adjacent electrode fingers or the average distance between the centers 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.

[0087] like Figure 6As shown, if d / 2p exceeds 0.25, i.e., d / p > 0.5, even with adjustments to d / p, the fractional bandwidth is less than 5%. Conversely, when d / 2p ≤ 0.25, i.e., d / p ≤ 0.5, varying d / p within this range allows for a fractional bandwidth of 5% or more, enabling the construction of a resonator with a high coupling coefficient. Furthermore, when d / 2p is 0.12 or less, i.e., d / p is 0.24 or less, the fractional bandwidth can be increased to 7% or more. Moreover, adjusting d / p within this range yields a resonator with an even wider fractional bandwidth, achieving a resonator with an even higher coupling coefficient. 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 first-order mode of the bulk wave can be constructed.

[0088] Furthermore, at least one pair of electrodes can be a pair. In the case of a pair of electrodes, p is defined as the distance between the centers of adjacent electrode fingers 3 and 4. In addition, in the case of 1.5 or more pairs of electrodes, p can be defined as the average distance between the centers of adjacent electrode fingers 3 and 4.

[0089] Furthermore, regarding the thickness d of the piezoelectric layer 2, even if the piezoelectric layer 2 has a thickness deviation, the value obtained by averaging the thickness can be used.

[0090] 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 electrode fingers 3 and electrode fingers 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, if the aforementioned d / p is 0.5 or less, it is also possible to effectively excite the first-order mode of thickness shear in a bulk wave.

[0091] In the elastic wave device 1, it is preferable that, among the plurality of electrode fingers 3 and 4, the metallization ratio MR of the overlapping region (i.e., the excitation region C) when any adjacent electrode fingers 3 and 4 are viewed in opposite directions satisfies MR ≤ 1.75(d / p) + 0.075. In this case, stray emissions can be effectively reduced. (Refer to...) Figure 8 as well as Figure 9 This needs to be explained.

[0092] Figure 8This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. Strays, 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 metallization ratio MR is set to 0.35.

[0093] Reference Figure 1B To illustrate the metallization ratio (MR). In Figure 1B In the electrode structure, focusing on a pair of electrode fingers 3 and 4, it is assumed that only this pair of electrode fingers 3 and 4 are provided. In this case, the portion enclosed by the single-dotted line is called the excitation region C. The excitation region C refers to the region in electrode finger 3 that overlaps with electrode finger 4, the region in electrode finger 4 that overlaps with electrode finger 3, and the region between electrode fingers 3 and 4 when viewed from a direction orthogonal to their length direction (i.e., the opposing direction). Furthermore, the area of ​​electrode fingers 3 and 4 within the excitation region C relative 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.

[0094] In addition, when multiple pairs of electrode fingers 3 and 4 are provided, it is sufficient to set the ratio of the total area of ​​the metallized portion included in the entire excitation region C to the total area of ​​the excitation region C as MR.

[0095] Figure 9 This is an explanatory diagram showing the relationship between the fractional bandwidth and the phase rotation amount of the stray impedance normalized by 180 degrees, which is the magnitude of the stray, in the case of a plurality of elastic wave resonators constituting the elastic wave device of the first embodiment. Furthermore, various changes and adjustments were made to the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4 regarding the fractional bandwidth. In addition, Figure 9 This is the result when using piezoelectric layer 2 with Z-cut LiNbO3, but the same tendency also occurs when using piezoelectric layer 2 with other cut angles.

[0096] exist Figure 9 In the region enclosed by ellipse J, the stray energy increases to 1.0. (As shown from...) Figure 9 It is clear that if the fractional bandwidth exceeds 0.17, that is, if it exceeds 17%, then even if the parameters constituting the fractional bandwidth are changed, large spurious signals with a spur level greater than 1 will still appear in the passband. That is, as... Figure 8 As shown in the resonance characteristics, a large spurious signal, indicated by arrow B, appears within the frequency band. Therefore, the fractional bandwidth is preferably 17% or less. In this case, the spurious signal can be reduced by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrode fingers 3 and 4, etc.

[0097] Figure 10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio (MR), and fractional 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 fractional bandwidth was measured. Figure 10 The portion shown by the shading to the right of the dashed line D is the region with a fractional bandwidth of 17% or less. The boundary between this shaded region and the unshaded region is 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 achieve a fractional bandwidth of 17% or less. More preferably... Figure 10 The region to the right of MR = 3.5(d / 2p) + 0.05 is shown by the single-dotted line D1. That is, if MR ≤ 1.75(d / p) + 0.05, the fractional bandwidth can be reliably kept below 17%.

[0098] Figure 11 This is an explanatory diagram showing the mapping of the fractional bandwidth relative to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0. The portion shown by the overline in Figure 11 is the region where at least 5% fractional bandwidth can be obtained. If the range of the region is approximated, it becomes the range represented by the following equations (1), (2), and (3).

[0099] (0°±10°, 0°~20°, any ψ)... Equation (1)

[0100] (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)

[0101] (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 [~180°, any ψ)...Equation (3)

[0102] Therefore, within the range of Euler angles in equations (1), (2), or (3) above, it is preferable to be able to sufficiently broaden the fractional bandwidth.

[0103] Figure 12 This is a partially sectional perspective view illustrating the elastic wave device according to embodiments of the present invention. Figure 12In the diagram, the outer periphery of the cavity 9 is shown by a dashed line. The elastic wave device of the present invention can also be an elastic wave device utilizing plate waves. In this case, such as... Figure 12 As shown, the elastic wave device 301 includes reflectors 310 and 311. Reflectors 310 and 311 are disposed on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the direction of elastic wave propagation. In the elastic wave device 301, an alternating electric field is applied to the electrode fingers 3 and 4 on the cavity portion 9, thereby exciting a Lamb wave, which is a plate wave. Since reflectors 310 and 311 are disposed on both sides, resonance characteristics based on the Lamb wave as a plate wave can be obtained.

[0104] As explained above, in elastic wave devices 1 and 101, a first-order thickness shear mode volume wave is utilized. Furthermore, in elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes. When the thickness of the piezoelectric layer 2 is set to d, and the center-to-center distance between the first electrode finger 3 and the second electrode finger 4 is set to p, d / p is set to 0.5 or less. Therefore, even with miniaturization of the elastic wave device, the Q value can be improved.

[0105] In the elastic wave devices 1 and 101, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. On the first main surface 2a or the second main surface 2b of the piezoelectric layer 2, there are first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2, and it is preferable to cover the first electrode fingers 3 and the second electrode fingers 4 with a protective film.

[0106] Figure 13A This is a top view showing a first embodiment of the elastic wave device according to the first embodiment. Figure 13B It is along Figure 13A A sectional view of the BB line portion. Figure 13C It is along Figure 13A A cross-sectional view of the CC line portion. For example... Figure 13A As shown, the elastic wave device 1A includes a through hole 10 communicating with the cavity portion 9 and a reinforcing strut 11 supporting the piezoelectric layer 2 and the support substrate 8 between the cavity portion 9. Furthermore, in the first embodiment, the support substrate 8 is a plate-shaped member without an opening 8a. Therefore, the cavity portion 9 becomes a space surrounded by the second main surface 2b of the piezoelectric layer 2, the inner wall of the opening 7a of the dielectric film 7, and the surface of the support substrate 8 on the piezoelectric layer 2 side. Here, the cavity portion 9 also includes an outlet passage 9a serving as a cavity communicating with the through hole 10.

[0107] The through-hole 10 is a hole that penetrates the piezoelectric layer 2. The through-hole 10 is located at a position where, when viewed from above in the Z direction, at least a portion overlaps with the void 9 but does not overlap with the IDT electrode. In the first embodiment, as... Figure 13AAs shown, the through-hole 10 is provided at two locations: one on the center line BB of the IDT electrode in the Y direction, and the other at a position sandwiching the IDT electrode in the X direction. Furthermore, as... Figure 13B As shown, the through hole 10 communicates with the lead-out passage 9a of the cavity 9 described later in the Z direction. Therefore, in the first embodiment, as... Figure 13B As shown, the through holes 10 can be said to be interconnected via the void portion 9. Furthermore, it is preferable that at least two through holes 10 are provided in the piezoelectric layer 2, but one may also be provided. In addition, in the first embodiment, the shape of the through hole 10 is rectangular when viewed from above in the Z direction, but it is not limited to this; for example, it may also be circular, other polygonal shapes, etc.

[0108] The lead-out passage 9a is a cavity in the cavity 9 that communicates with the through hole 10. Viewed from above in the Z direction, the lead-out passage 9a is located at both ends of the cavity 9 in the X direction and overlaps with the through hole 10. That is, the lead-out passage 9a is located in the portion communicating with the through hole 10. In the first embodiment, viewed from above in the Z direction, the lead-out passage 9a is located in a region that does not overlap with the first electrode finger 3 and the second electrode finger 4. Furthermore, the area of ​​the lead-out passage 9a is preferably smaller than the area in the cavity 9 that overlaps with the IDT electrode. Furthermore, it is more preferable that the maximum size of the lead-out passage 9a in the Y direction is smaller than the maximum size of the area in the cavity 9 that overlaps with the IDT electrode in the Y direction. Additionally, in... Figure 13A In the example, the shape of the leading path 9a is rectangular when viewed from above in the Z direction, but it is not limited to this. For example, it can also be a trapezoid, a semicircle, or other shapes.

[0109] The reinforcing support 11 is a support disposed within the cavity 9 and supports the piezoelectric layer 2 and the support substrate 8. For example... Figure 13A As shown, the reinforcing support 11 is positioned in a region that overlaps with the cavity 9 but does not overlap with the first electrode finger 3 and the second electrode finger 4 when viewed from above in the Z direction. Furthermore, as... Figure 13C As shown, the reinforcing strut 11 is disposed inside the cavity 9. At this time, the upper end of the reinforcing strut 11 in the Z direction is bonded to the piezoelectric layer 2, and the lower end in the Z direction is bonded to the support substrate 8. Accordingly, the piezoelectric layer 2 is supported by the reinforcing strut 11, thus suppressing the deflection of the piezoelectric layer 2 and preventing crack formation.

[0110] In the first embodiment, the reinforcing struts 11 are not positioned near the lead-out passage 9a in the X direction. More specifically, viewed from above in the Z direction, four reinforcing struts 11 are provided at both ends in the X direction of the area excluding the lead-out passage 9a in the cavity 9, and at positions in the Y direction that do not overlap with the portion communicating with the lead-out passage 9a. Furthermore, the reinforcing struts 11 are pillars having length in the Z direction. In this case, the shape of the reinforcing struts 11, i.e., the side surface, preferably has a curved surface. Accordingly, during the manufacturing process of the elastic wave device 1A, it is possible to suppress the flow of etching solution that obstructs the flow into the cavity 9. In addition, Figure 13A The structure and shape of the reinforcing support 11 shown are merely examples and are not limited to them. Only one or more reinforcing supports 11 need to be provided, and the shape of the reinforcing support 11 can be arbitrary as long as its side surface includes a curved surface.

[0111] Furthermore, the reinforcing strut 11 is preferably formed of the same material as the dielectric film 7. In this case, the reinforcing strut 11 can be easily formed during the manufacturing process of the elastic wave device 1A. However, the reinforcing strut 11 is not limited to this; for example, it can also be formed of metals such as Ti, Al, Cu, and Ni. In this case, the reinforcing strut 11 has excellent thermal conductivity, thus improving the heat dissipation of the elastic wave device 1A.

[0112] Here, in the elastic wave device 1 according to the first embodiment, the lead-out passage 9a of the cavity 9 is not a necessary structure. Hereinafter, the second embodiment will be described using the accompanying drawings as a case where the cavity 9 does not have the lead-out passage 9a.

[0113] Figure 14 This is a top view showing a second embodiment of the elastic wave device according to the first embodiment. (As shown) Figure 14 As shown, the difference between the elastic wave device 1B of the second embodiment and the first embodiment is that the cavity 9 does not have an outlet passage 9a. In this case, the cavity 9 is configured to overlap with the through hole 10, so that it is directly connected to the through hole 10.

[0114] In the second embodiment, viewed from above in the Z direction, the reinforcing strut 11 is disposed in a region that does not overlap with the first electrode finger 3 and the second electrode finger 4 and overlaps with the cavity 9. More specifically, viewed from above in the Z direction, four reinforcing struts 11 are disposed at positions between the X-direction ends of the plurality of electrode fingers 3, 4 in the X direction and the through hole 10, and at positions in the Y direction that do not overlap with the through hole 10, the first electrode finger 3, and the second electrode finger 4. Accordingly, during the manufacturing process of the elastic wave device 1B, the flow of etching solution that obstructs the flow into the cavity 9 can be suppressed. Furthermore, Figure 14 The structure and shape of the reinforcing strut 11 shown are only one example and are not limited thereto.

[0115] Furthermore, in the elastic wave device 1, the position of the reinforcing support 11 is not limited to... Figure 13A as well as Figure 14 The location is shown. Hereinafter, the third and fourth embodiments will be described using the accompanying drawings, assuming that the reinforcing support 11 is not placed elsewhere.

[0116] Figure 15 This is a top view showing a third embodiment of the elastic wave device according to the first embodiment. (As shown) Figure 15 As shown, the difference between the third embodiment and the first embodiment is that the reinforcing pillar 11 is disposed inside the lead-out passage 9a. In the third embodiment, the reinforcing pillar 11 is disposed inside the lead-out passage 9a and at a position that does not overlap with the through hole 10 in the Z direction. In this case, the reinforcing pillar 11 is, for example, a cylinder having a length in the Z direction. The maximum length of the reinforcing pillar 11 in the Y direction is preferably smaller than the width of the lead-out passage 9a in the Y direction. Accordingly, the piezoelectric layer 2 is supported by the reinforcing pillar 11, thus suppressing the deflection of the piezoelectric layer 2 and preventing crack formation. Furthermore, Figure 15 The structure and shape of the reinforcing strut 11 shown are only one example and are not limited thereto.

[0117] Figure 16 This is a top view showing a fourth embodiment of the elastic wave device according to the first embodiment. Figure 16 As shown, the fourth embodiment differs from the first and third embodiments in that the reinforcing support 11 is disposed between adjacent electrode fingers 3 or 4. In the fourth embodiment, the reinforcing support 11 is disposed inside the cavity 9 and, viewed from above in the Z direction, is disposed between adjacent electrode fingers 3 or 4 in the X direction. In this case, as... Figure 16 As shown, electrode finger 3 or electrode finger 4 is positioned in the Z direction without overlapping with the reinforcing strut 11. Accordingly, the piezoelectric layer 2 is supported by the reinforcing strut 11, thus suppressing the deflection of the piezoelectric layer 2 and preventing crack formation. Furthermore, Figure 16 The structure and shape of the reinforcing strut 11 shown are only one example and are not limited thereto.

[0118] Furthermore, in the elastic wave device 1, the dielectric film 7 is not a necessary structure. In this case, the void portion 9 can also be provided in the piezoelectric layer 2 or the support substrate 8. Hereinafter, the fifth embodiment will be described with reference to the case where the void portion 9 is provided in the piezoelectric layer 2, and the sixth embodiment will be described with reference to the case where the void portion 9 is provided in the support substrate 8.

[0119] Figure 17A This is a top view showing the fifth embodiment of the elastic wave device according to the first embodiment. Figure 17B It is along Figure 17A A sectional view of the BB line portion. Figure 17C It is along Figure 17A A cross-sectional view of the CC line portion. For example... Figure 17B As shown, the difference between the fifth embodiment and the first embodiment is that the dielectric film 7 is missing, and the void portion 9 is provided in the piezoelectric layer 2. In this way, the void portion 9 can also be a space surrounded by the concave surface 2c of the piezoelectric layer 2 provided on the second main surface 2b and the surface on the side of the piezoelectric layer 2 of the support substrate 8.

[0120] Figure 18A This is a top view showing the sixth embodiment of the elastic wave device according to the first embodiment. Figure 18B It is along Figure 18A A sectional view of the BB line portion. Figure 18C It is along Figure 18A A cross-sectional view of the CC line portion. For example... Figure 18B As shown, the difference between the sixth embodiment and the first embodiment is that the dielectric film 7 is missing, and the void portion 9 is provided in the support substrate 8. In this way, the void portion 9 can also be a space surrounded by the second main surface 2b of the piezoelectric layer 2 and the concave surface 8c of the surface of the support substrate 8 provided on the side of the piezoelectric layer 2.

[0121] As described above, the elastic wave devices 1A to 1F according to the first embodiment include a support substrate 8 having a thickness in a first direction, a piezoelectric layer 2 disposed in the first direction of the support substrate 8, and an IDT electrode disposed in the piezoelectric layer 2. The IDT electrode has a plurality of first electrode fingers 3 extending in a second direction intersecting the first direction, and a plurality of second electrode fingers 4 opposing any one of the plurality of first electrode fingers 3 and extending in the second direction in a third direction orthogonal to the second direction. A cavity 9 is provided between the support substrate 8 and the piezoelectric layer 2 at a position where at least a portion overlaps with the IDT electrode in the first direction. At a position where it does not overlap with the IDT electrode in the first direction, at least one through hole 10 penetrating the piezoelectric layer 2 is provided, and the through hole 10 communicates with the cavity 9. In the region where it does not overlap with the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 in the first direction but overlaps with the cavity 9, a reinforcing strut 11 extending in the first direction is provided in the cavity 9.

[0122] With the above structure, the region of the piezoelectric layer 2 that overlaps with the cavity 9 in the first direction is supported by the reinforcing strut 11 within the cavity 9. Therefore, deflection of the piezoelectric layer 2 can be suppressed, thus suppressing the generation of cracks in the piezoelectric layer 2.

[0123] Furthermore, in the elastic wave devices 1A to 1F according to the first embodiment, the reinforcing pillar 11 has a curved shape when viewed from above in the first direction. Accordingly, when manufacturing the elastic wave devices 1A to 1F, if the etching solution flows into the cavity 9, the flow of the etching solution can be prevented from being blocked by the reinforcing pillar 11.

[0124] Furthermore, in the elastic wave devices 1A to 1D according to the first embodiment, a dielectric film 7 is provided on the support substrate 8, a portion of the dielectric film 7 has a void 9, and the reinforcing pillar 11 is made of the same material as the dielectric film 7. Accordingly, the reinforcing pillar 11 can be easily formed.

[0125] As is desired, the material of the dielectric film 7 includes at least one of silicon oxide, silicon nitride, and bauxite. Accordingly, an elastic wave device with good resonance characteristics can be provided.

[0126] Furthermore, in the elastic wave devices 1A to 1F according to the first embodiment, the material of the reinforcing strut 11 may also include metal. In this case, the reinforcing strut 11 has excellent thermal conductivity, thus improving the heat dissipation of the elastic wave devices 1A to 1F.

[0127] Furthermore, in the elastic wave devices 1A to 1C according to the first embodiment, when viewed from above in the first direction, the reinforcing strut 11 is disposed between the end of one of the plurality of first electrode fingers 3 or the plurality of second electrode fingers 4 located in the third direction and the through hole 10. Accordingly, the deflection of the piezoelectric layer 2 can be suppressed, and thus the generation of cracks in the piezoelectric layer 2 can be suppressed.

[0128] Furthermore, in the elastic wave devices 1A and 1C according to the first embodiment, the cavity 9 has an outlet passage 9a with an area smaller than the area of ​​the cavity 9 that overlaps with the IDT electrode in the first direction, and the reinforcing pillar 11 is disposed near the outlet passage 9a. Accordingly, when manufacturing the elastic wave devices 1A and 1C, when the etching solution flows into the cavity 9, it is possible to prevent the flow of the etching solution from being blocked by the reinforcing pillar 11.

[0129] Furthermore, in the elastic wave device 1D according to the first embodiment, when viewed from above in the first direction, the reinforcing strut 11 is disposed between adjacent first electrode fingers 3 or second electrode fingers 4 among a plurality of first electrode fingers 3 and a plurality of second electrode fingers 4. Accordingly, the deflection of the piezoelectric layer 2 can be suppressed, and thus the generation of cracks in the piezoelectric layer 2 can be suppressed.

[0130] As a desirable approach, in the elastic wave devices 1A to 1F according to the first embodiment, at least two through holes 10 are provided in the third direction, with an IDT electrode sandwiched between them, and the two through holes 10 are connected via the cavity 9. In this case, the elastic wave devices 1A to 1F can be easily manufactured.

[0131] Ideally, when the center-to-center distance between adjacent first electrode fingers 3 and second electrode fingers 4 is set to p, the thickness of the piezoelectric layer 2 is 2p or less. This enables miniaturization of the elastic wave device and improves the Q value.

[0132] As is desirable, the material of the piezoelectric layer 2 includes lithium niobate or lithium tantalate. Accordingly, an elastic wave device with good resonance characteristics can be provided.

[0133] As a more desirable approach, the Euler angles of lithium niobate or lithium tantalate constituting piezoelectric layer 2 are... θ and ψ are within the range of equations (1), (2), or (3) below. In this case, the fractional bandwidth can be sufficiently widened.

[0134] (0°±10°, 0°~20°, any ψ)... Equation (1)

[0135] (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)

[0136] (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 [~180°, any ψ)...Equation (3)

[0137] Ideally, when the thickness of the piezoelectric layer 2 is set to d, and the center-to-center distance between adjacent first electrode fingers 3 and second electrode fingers 4 among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 is set to p, d / p ≤ 0.5. Accordingly, the elastic wave device can be miniaturized, and the Q value can be improved.

[0138] As a more desirable approach, d / p should be below 0.24. This allows for the miniaturization of the elastic wave device and improves the Q value.

[0139] As a desired approach, the area where adjacent electrode fingers overlap when viewed in opposite directions is defined as the excitation region C. When the metallization ratio of multiple electrode fingers relative to the excitation region C is set as MR, MR ≤ 1.75(d / p) + 0.075 is satisfied. In this case, the fractional bandwidth can be reliably kept below 17%.

[0140] (Second Implementation)

[0141] Figures 19A to 19C This is a diagram of an embodiment of the elastic wave device according to the second embodiment. The elastic wave device 1G according to the second embodiment differs from that of the first embodiment in that it is provided with reinforcing ribs 12. In the second embodiment, the same reference numerals are used for structures identical to those in the first embodiment, and descriptions are omitted.

[0142] The reinforcing rib 12 is a support column provided on the wall of the cavity 9 and supporting the piezoelectric layer 2 and the support substrate 8. For example... Figure 19A As shown, viewed from above in the Z direction, the reinforcing rib 12 is positioned in a region that does not overlap with the first electrode finger 3 and the second electrode finger 4. The reinforcing rib 12 is configured to protrude from the side wall of the cavity 9 (the wall surface of the opening 7a) into the cavity 9. That is, a portion of the reinforcing rib 12 is embedded in the dielectric film 7 on one side, while the other side is exposed within the cavity 9. At this time, as... Figure 19C As shown, the upper end of the reinforcing rib 12 in the Z direction is bonded to the piezoelectric layer 2, and the lower end in the Z direction is bonded to the support substrate 8. Accordingly, the piezoelectric layer 2 is supported by the reinforcing rib 12, so that the deflection of the piezoelectric layer 2 can be suppressed and cracks can be prevented.

[0143] In this embodiment, reinforcing ribs 12 are provided near the lead-out passage 9a in the X direction. More specifically, four reinforcing ribs 12 are provided on the walls at both ends in the X direction of the cavity 9 (excluding the lead-out passage 9a) and at positions in the Y direction that do not overlap with the portion communicating with the lead-out passage 9a. Furthermore, in this embodiment, the reinforcing ribs 12 are cylindrical bodies with length in the Z direction and curved surfaces on their sides. Accordingly, during the manufacturing process of the elastic wave device 1G, it is possible to prevent obstruction of the flow of etching solution into the cavity 9. Additionally, Figure 19A The structure and shape of the reinforcing rib 12 shown are merely an example and are not limited thereto. Only one or more reinforcing ribs 12 need to be provided, and the shape of the reinforcing rib 12 can be any shape as long as its side surface includes a curved surface.

[0144] Furthermore, the reinforcing rib 12 is preferably formed of the same material as the dielectric film 7. In this case, the reinforcing rib 12 can be easily formed during the manufacturing process of the elastic wave device 1G. However, the reinforcing rib 12 is not limited to this; for example, it can also be formed of metals such as Ti, Al, Cu, and Ni. In this case, the reinforcing rib 12 has excellent thermal conductivity, thus improving the heat dissipation of the elastic wave device 1G.

[0145] As described above, the elastic wave device 1G according to the second embodiment includes a support substrate 8 having a thickness in a first direction, a piezoelectric layer 2 disposed in the first direction of the support substrate 8, and an IDT electrode disposed in the piezoelectric layer 2. The IDT electrode has a plurality of first electrode fingers 3 extending in a second direction intersecting the first direction, and a plurality of second electrode fingers 4 opposing any one of the plurality of first electrode fingers 3 and extending in the second direction in a third direction orthogonal to the second direction. A cavity 9 is provided between the support substrate 8 and the piezoelectric layer 2 at a position where at least a portion overlaps with the IDT electrode in the first direction. At a position where it does not overlap with the IDT electrode in the first direction, at least one through hole 10 penetrating the piezoelectric layer 2 is provided, and the through hole 10 communicates with the cavity 9. The elastic wave device has a reinforcing rib 12 that does not overlap with the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 in the first direction and protrudes from the sidewall of the cavity 9 into the cavity 9.

[0146] With the above structure, the region of the piezoelectric layer 2 that overlaps with the cavity 9 in the first direction is supported by the reinforcing rib 12 within the cavity 9. Therefore, deflection of the piezoelectric layer 2 can be suppressed, thus suppressing the generation of cracks in the piezoelectric layer 2.

[0147] Furthermore, in the elastic wave device 1G according to the second embodiment, the reinforcing rib 12 has a curved shape when viewed from above in the first direction. Accordingly, when manufacturing the elastic wave device 1G, if the etching solution flows into the cavity 9, the flow of the etching solution can be prevented from being blocked by the reinforcing rib 12.

[0148] Furthermore, in the elastic wave device 1G according to the second embodiment, a dielectric film 7 is provided on the support substrate 8, and a portion of the dielectric film 7 has a void 9. The reinforcing rib 12 is made of the same material as the dielectric film 7. Accordingly, the reinforcing rib 12 can be easily formed.

[0149] Furthermore, in the elastic wave device 1G according to the second embodiment, the material of the reinforcing rib 12 may also include metal. In this case, the reinforcing rib 12 has excellent thermal conductivity, thus improving the heat dissipation of the elastic wave device 1G.

[0150] Furthermore, in the elastic wave device 1G according to the second embodiment, the cavity 9 has an outlet passage 9a with an area smaller than the area of ​​the cavity 9 that overlaps with the IDT electrode in the first direction, and the reinforcing rib 12 is disposed near the outlet passage 9a. Accordingly, when manufacturing the elastic wave device 1G, if the etching solution flows into the cavity 9, the flow of the etching solution can be prevented from being blocked by the reinforcing rib 12.

[0151] 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 equivalents are also included in this disclosure.

[0152] Explanation of reference numerals in the attached figures

[0153] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 101, 301 Elastic Wave Device

[0154] 2 Piezoelectric layer

[0155] 2a First Main Face

[0156] 2b Second Main Face

[0157] 2c concave surface

[0158] 3 (First) Electrode Finger

[0159] 4 (2nd) Electrode Finger

[0160] 5. First Conduit

[0161] 6. Second Conduit

[0162] 7. Dielectric film

[0163] 8 Support base plate

[0164] 7a, 8a openings

[0165] 8c concave surface

[0166] 9. Hollow Section

[0167] 9a Outlet pathway

[0168] 10 Through Holes

[0169] 11. Strengthen the pillars

[0170] 12 Reinforcing Ribs

[0171] 201 piezoelectric layer

[0172] 201a 1st Main Side

[0173] 201b, second main page

[0174] 310, 311 reflectors

[0175] 451 Area 1

[0176] 452 Area 2

[0177] C. Excitation Region

[0178] VP1 Virtual Plane

[0179] d Thickness

[0180] p is the distance between centers.

Claims

1. An elastic wave device, comprising: A support substrate having a thickness in a first direction; A piezoelectric layer disposed in the first direction of the supporting substrate; and An IDT electrode, disposed in the piezoelectric layer, has a plurality of first electrode fingers and a plurality of second electrode fingers. The plurality of first electrode fingers extend in a second direction intersecting the first direction. The plurality of second electrode fingers are opposite to any one of the plurality of first electrode fingers in a third direction orthogonal to the second direction and extend in the second direction. A void is provided between the support substrate and the piezoelectric layer, at a location where at least a portion overlaps with the IDT electrode in the first direction. At a position in the first direction that does not overlap with the IDT electrode, there is at least one through-hole penetrating the piezoelectric layer, the through-hole communicating with the cavity portion. In the region that does not overlap with the plurality of first electrode fingers and the plurality of second electrode fingers in the first direction but overlaps with the cavity, a reinforcing strut extending in the first direction is provided within the cavity.

2. The elastic wave device according to claim 1, wherein, Viewed from above in the first direction, the reinforcing strut has a curved shape.

3. The elastic wave device according to claim 1 or 2, wherein, The elastic wave device further includes a dielectric film disposed on the support substrate, and the void portion is provided in a portion of the dielectric film. The reinforcing strut is made of the same material as the dielectric film.

4. The elastic wave device according to claim 1 or 2, wherein, The reinforcing strut is made of metal.

5. The elastic wave device according to any one of claims 1 to 4, wherein, Viewed from above in the first direction, the reinforcing strut is disposed between the first or second electrode finger located at the end in the third direction of the plurality of first electrode fingers and the plurality of second electrode fingers and the through hole.

6. The elastic wave device according to any one of claims 1 to 5, wherein, The cavity has an outgoing passage with an area smaller than the region of the cavity that overlaps with the IDT electrode in the first direction. The reinforcing support is positioned near the outlet passage.

7. The elastic wave device according to any one of claims 1 to 4, wherein, Viewed from above in the first direction, the reinforcing strut is disposed between adjacent first or second electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers.

8. An elastic wave device, comprising: A support substrate having a thickness in a first direction; A piezoelectric layer disposed in the first direction of the supporting substrate; and An IDT electrode, disposed in the piezoelectric layer, has a plurality of first electrode fingers and a plurality of second electrode fingers. The plurality of first electrode fingers extend in a second direction intersecting the first direction. The plurality of second electrode fingers are opposite to any one of the plurality of first electrode fingers in a third direction orthogonal to the second direction and extend in the second direction. A void is provided between the support substrate and the piezoelectric layer, at a location where at least a portion overlaps with the IDT electrode in the first direction. At a position in the first direction that does not overlap with the IDT electrode, there is at least one through-hole penetrating the piezoelectric layer, the through-hole communicating with the cavity portion. The elastic wave device has reinforcing ribs that do not overlap with the plurality of first electrode fingers and the plurality of second electrode fingers in the first direction, and protrude from the sidewall of the cavity into the cavity.

9. The elastic wave device according to claim 8, wherein, Viewed from above in the first direction, the reinforcing rib has a curved shape.

10. The elastic wave device according to claim 8 or 9, wherein, The elastic wave device further includes a dielectric film disposed on the support substrate, and the void portion is provided in a portion of the dielectric film. The reinforcing ribs are made of the same material as the dielectric film.

11. The elastic wave device according to claim 8 or 9, wherein, The reinforcing ribs are made of metal.

12. The elastic wave device according to any one of claims 8 to 11, wherein, The cavity has an outlet passage with an area smaller than the area overlapping the IDT electrode in the first direction, and the reinforcing rib is disposed near the outlet passage.

13. The elastic wave device according to claim 3 or 10, wherein, The dielectric film is made of at least one of silicon oxide, silicon nitride, and bauxite.

14. The elastic wave device according to any one of claims 1 to 13, wherein, At least two through holes are provided in the third direction, sandwiching the IDT electrode, and the two through holes are connected through the cavity.

15. The elastic wave device according to any one of claims 1 to 14, wherein, When the center-to-center distance between adjacent first and second electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is set as p, the thickness of the piezoelectric layer is 2p or less.

16. The elastic wave device according to any one of claims 1 to 15, wherein, The piezoelectric layer is made of lithium niobate or lithium tantalate.

17. The elastic wave device according to claim 16, 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).

18. The elastic wave device according to claim 16, wherein, When the thickness of the piezoelectric layer is set as d, and the center-to-center distance between adjacent first and second electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is set as p, d / p≤0.

5.

19. The elastic wave device according to claim 18, wherein, d / p is below 0.

24.

20. The elastic wave device according to claim 18 or 19, wherein, When adjacent electrode fingers are viewed in opposite directions, the overlapping area 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.

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