WO2023195523A1 - Elastic wave device - Google Patents

Abstract

An elastic wave device according to the present disclosure comprises: a support member having a cavity in one main surface; a piezoelectric layer provided on the one main surface of the support member; and an IDT electrode provided to the piezoelectric layer, at least part of said IDT electrode overlapping the cavity as seen in the lamination direction of the support member and the piezoelectric layer. The IDT electrode comprises: a first bus bar electrode; a second bus bar electrode facing the first bus bar electrode; first electrode fingers connected to the first bus bar electrode, the first electrode fingers extending from the first bus bar electrode toward the second bus bar electrode and being separate from the second bus bar electrode; second electrode fingers connected to the second bus bar electrode, the second electrode fingers extending from the second bus bar electrode toward the first bus bar electrode and being separate from the first bus bar electrode; and a reinforcing electrode provided to at least part of the electrode fingers of the first electrode fingers and the second electrode fingers. At least one first electrode finger and at least one second electrode finger are alternately arranged. As seen in the lamination direction, at least part of the reinforcing electrode overlaps the cavity.

Description

elastic wave device

The present disclosure relates to an acoustic wave device having a piezoelectric layer.

For example, Patent Document 1 discloses an elastic wave device that uses plate waves. The elastic wave device described in Patent Document 1 includes a support, a piezoelectric substrate, and an IDT electrode. The support body is provided with a cavity. The piezoelectric substrate is provided on the support body so as to overlap with the cavity. The IDT electrode is provided on the piezoelectric substrate so as to overlap with the cavity. In an elastic wave device, a plate wave is excited by an IDT electrode.

Japanese Patent Application Publication No. 2012-257019

In recent years, there has been a demand for elastic wave devices that can suppress deterioration of characteristics.

An object of the present disclosure is to provide an elastic wave device that can suppress deterioration of characteristics.

a support member having a hollow portion on its main surface;
a piezoelectric layer provided on one main surface of the support member;
an IDT electrode provided on the piezoelectric layer and at least partially overlapping the cavity when viewed from the stacking direction of the support member and the piezoelectric layer,
The IDT electrode is
a first busbar electrode;
a second busbar electrode facing the first busbar electrode;
a first electrode finger connected to the first busbar electrode, extending from the first busbar electrode toward the second busbar electrode, and separated from the second busbar electrode;
a second electrode finger connected to the second busbar electrode, extending from the second busbar electrode toward the first busbar electrode, and separated from the first busbar electrode;
a reinforcing electrode provided on at least some of the first electrode fingers and the second electrode fingers;
At least one of the first electrode fingers and at least one of the second electrode fingers are arranged alternately along an electrode finger facing direction that intersects with the electrode finger extending direction,
When viewed from the stacking direction, at least a portion of the reinforcing electrode overlaps with the cavity.

According to the present disclosure, it is possible to provide an elastic wave device that can suppress deterioration of characteristics.

A schematic perspective view showing the appearance of the elastic wave device of the first and second aspects Plan view showing the electrode structure on the piezoelectric layer A cross-sectional view of the portion along line AA in Figure 1A A schematic front sectional view for explaining Lamb waves propagating through a piezoelectric film of a conventional acoustic wave device. A schematic front sectional view for explaining waves of the elastic wave device of the present disclosure A schematic diagram showing a bulk wave when a voltage is applied between the first electrode and the second electrode such that the second electrode has a higher potential than the first electrode. A diagram showing resonance characteristics of an elastic wave device according to a first embodiment of the present disclosure A diagram showing the relationship between d/2p and the fractional band as a resonator of an elastic wave device A plan view of another elastic wave device according to the first embodiment of the present disclosure A reference diagram showing an example of resonance characteristics of an elastic wave device. A diagram showing the relationship between the fractional band when a large number of elastic wave resonators are configured and the amount of phase rotation of spurious impedance normalized by 180 degrees as the magnitude of spurious. A diagram showing the relationship between d/2p, metallization ratio MR, and fractional band A diagram showing a map of the fractional band with respect to the Euler angles (0°, θ, ψ) of LiNbO3 when d/p is brought as close to 0 as possible A partially cutaway perspective view for explaining an elastic wave device according to a first embodiment of the present disclosure A schematic plan view of an elastic wave device according to a second embodiment of the present disclosure A schematic end view of the elastic wave device shown in FIG. 13 taken along line AA. Enlarged view of the part surrounded by a dashed-dotted line in Figure 13 A schematic plan view of an elastic wave device according to a third embodiment of the present disclosure A schematic end view of the elastic wave device shown in FIG. 16 taken along line BB. Enlarged view of the part surrounded by a dashed-dotted line in Figure 16 A schematic plan view of an elastic wave device according to a fourth embodiment of the present disclosure A schematic end view of the elastic wave device shown in FIG. 19 taken along line C-C. Figure 21 is an enlarged view of the part surrounded by the dashed line in Figure 19. A schematic plan view of an elastic wave device according to a fifth embodiment of the present disclosure A schematic end view of the elastic wave device shown in FIG. 22 taken along line DD Enlarged view of the part surrounded by a dashed-dotted line in Figure 22 A schematic end view corresponding to the AA line in FIG. 14 of the elastic wave device according to the modified example. A schematic end view corresponding to the AA line in FIG. 14 of the elastic wave device according to the modified example. A schematic plan view of an example of a conventional elastic wave device 27 is an end view showing the manufacturing process of a conventional elastic wave device, and is a schematic end view corresponding to a section taken along the line EE of the elastic wave device shown in FIG. 27. 27 is an end view showing the manufacturing process of a conventional elastic wave device, and is a schematic end view corresponding to a section taken along the line EE of the elastic wave device shown in FIG. 27. 27 is an end view showing the manufacturing process of a conventional elastic wave device, and is a schematic end view corresponding to a section taken along the line EE of the elastic wave device shown in FIG. 27. 27 is an end view showing the manufacturing process of a conventional elastic wave device, and is a schematic end view corresponding to a section taken along the line EE of the elastic wave device shown in FIG. 27. 27 is an end view showing the manufacturing process of a conventional elastic wave device, and is a schematic end view corresponding to a section taken along the line EE of the elastic wave device shown in FIG. 27. 27 is an end view showing the manufacturing process of a conventional elastic wave device, and is a schematic end view corresponding to a section taken along the line EE of the elastic wave device shown in FIG. 27. A schematic end view of the elastic wave device shown in FIG. 27 taken along line E-E.

Acoustic wave devices according to first, second, and third aspects of the present disclosure include a piezoelectric layer made of lithium niobate or lithium tantalate, and a first electrode and a second electrode facing each other in a direction crossing the thickness direction of the piezoelectric layer. and an electrode.

The elastic wave device of the first aspect utilizes a bulk wave in a thickness shear mode.

Further, in the acoustic wave device of the second aspect, the first electrode and the second electrode are adjacent electrodes, the thickness of the piezoelectric layer is d, and the distance between the centers of the first electrode and the second electrode is p. In this case, d/p is 0.5 or less. Thereby, in the first and second aspects, the Q value can be increased even when miniaturization is promoted.

Furthermore, in the third aspect of the elastic wave device, Lamb waves are used as plate waves. Then, resonance characteristics due to the Lamb wave described above can be obtained.

An acoustic wave device according to a fourth aspect of the present disclosure includes a piezoelectric layer made of lithium niobate or lithium tantalate, and an upper electrode and a lower electrode that face each other in the thickness direction of the piezoelectric layer with the piezoelectric layer interposed therebetween. Take advantage of.

Hereinafter, the present disclosure will be clarified by describing specific embodiments of the elastic wave devices of the first to fourth aspects with reference to the drawings.

It should be noted that each embodiment described in this specification is an illustrative example, and it is possible to partially replace or combine the configurations between different embodiments.

(First embodiment)
FIG. 1A is a schematic perspective view showing the appearance of an acoustic wave device according to a first embodiment of the first and second aspects, and FIG. 1B is a plan view showing an electrode structure on a piezoelectric layer. , FIG. 2 is a cross-sectional view of a portion taken along line AA in FIG. 1A.

The acoustic wave device 1 has a piezoelectric layer 2 made of LiNbO ₃ . The piezoelectric layer 2 may be made of LiTaO ₃ . Although the cut angle of LiNbO ₃ and LiTaO ₃ is a Z cut in this embodiment, it may be a rotational Y cut or an X cut. Preferably, the propagation directions of Y propagation and X propagation are ±30°. The thickness of the piezoelectric layer 2 is not particularly limited, but is preferably 50 nm or more and 1000 nm or less in order to effectively excite the thickness shear mode.

The piezoelectric layer 2 has first and second main surfaces 2a and 2b that face each other. An electrode 3 and an electrode 4 are provided on the first main surface 2a. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In FIGS. 1A and 1B, the plurality of electrodes 3 are a plurality of first electrode fingers connected to the first bus bar 5. In FIGS. The plurality of electrodes 4 are a plurality of second electrode fingers connected to the second bus bar 6. The plurality of electrodes 3 and the plurality of electrodes 4 are interposed with each other.

The electrode 3 and the electrode 4 have a rectangular shape and have a length direction. The electrode 3 and the adjacent electrode 4 face each other in a direction perpendicular to this length direction. These plurality of electrodes 3 and 4, the first bus bar 5, and the second bus bar 6 constitute an IDT (Interdigital Transducer) electrode. The length direction of the electrodes 3 and 4 and the direction perpendicular to the length direction of the electrodes 3 and 4 are both directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can be said that the electrode 3 and the adjacent electrode 4 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2.

Furthermore, the length direction of the electrodes 3 and 4 may be replaced with the direction perpendicular to the length direction of the electrodes 3 and 4 shown in FIGS. 1A and 1B. That is, in FIGS. 1A and 1B, the electrodes 3 and 4 may extend in the direction in which the first bus bar 5 and the second bus bar 6 extend. In that case, the first bus bar 5 and the second bus bar 6 will extend in the direction in which the electrodes 3 and 4 extend in FIGS. 1A and 1B.

A plurality of pairs of structures in which an electrode 3 connected to one potential and an electrode 4 connected to the other potential are adjacent to each other are provided in a direction perpendicular to the length direction of the electrodes 3 and 4. There is. Here, the expression "electrode 3 and electrode 4 are adjacent" does not mean that electrode 3 and electrode 4 are arranged so as to be in direct contact with each other, but when electrode 3 and electrode 4 are arranged with a gap between them. refers to

Further, when the electrode 3 and the electrode 4 are adjacent to each other, no electrode connected to the hot electrode or the ground electrode, including the other electrodes 3 and 4, is arranged between the electrode 3 and the electrode 4. This logarithm does not need to be an integer pair, and may be 1.5 pairs, 2.5 pairs, or the like. The center-to-center distance between the electrodes 3 and 4, that is, the pitch, is preferably in the range of 1 μm or more and 10 μm or less. In addition, the center-to-center distance between the electrodes 3 and 4 refers to the center of the width dimension of the electrode 3 in the direction orthogonal to the length direction of the electrode 3, and the width dimension of the electrode 4 in the direction orthogonal to the length direction of the electrode 4. It is the distance between the center of Furthermore, when there is a plurality of at least one of the electrodes 3 and 4 ( electrodes 3 and 4 are a pair of electrode sets, and there are 1.5 or more pairs of electrode sets), the distance between the centers of the electrodes 3 and 4 is 1 It refers to the average value of the distance between the centers of adjacent electrodes 3 and 4 among 5 or more pairs of electrodes 3 and 4. Further, the width of the electrodes 3 and 4, that is, the dimension in the opposing direction of the electrodes 3 and 4, is preferably in the range of 150 nm or more and 1000 nm or less. Note that the distance between the centers of the electrodes 3 and 4 refers to the distance between the center of the dimension (width dimension) of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the center of the dimension (width dimension) of the electrode 4 in the direction orthogonal to the length direction of the electrode 4. This is the distance between the center of the dimension (width dimension).

Furthermore, in this embodiment, since a Z-cut piezoelectric layer is used, the direction perpendicular to the length direction of the electrodes 3 and 4 is the direction perpendicular to the polarization direction of the piezoelectric layer 2. This is not the case when a piezoelectric material having a different cut angle is used as the piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal, but approximately orthogonal (for example, the angle between the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is 90°±10°) But that's fine.

A support substrate 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an insulating layer 7 in between. The insulating layer 7 and the support substrate 8 constitute a support member. The insulating layer 7 and the support substrate 8 have a frame-like shape, and have openings 7a and 8a, as shown in FIG. Thereby, a cavity 9 is formed. The cavity 9 is provided so as not to impede the vibration of the intersection area C of the piezoelectric layer 2. Therefore, the support substrate 8 is laminated on the second main surface 2b with the insulating layer 7 interposed therebetween at a position that does not overlap with the portion where at least one pair of electrodes 3 and 4 are provided. Note that the insulating layer 7 may not be provided. Therefore, the support substrate 8 can be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

The insulating layer 7 is made of silicon oxide. However, other than silicon oxide, an appropriate insulating material such as silicon oxynitride or alumina can be used. The support substrate 8 is made of Si. The plane orientation of the Si surface on the piezoelectric layer 2 side may be (100), (110), or (111). Preferably, Si has a high resistivity of 4 kΩ or more. However, the support substrate 8 can also be constructed using an appropriate insulating material or semiconductor material. Examples of materials for the support substrate 8 include aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and starch. Various ceramics such as tite and forsterite, dielectrics such as diamond and glass, semiconductors such as gallium nitride, etc. can be used.

The plurality of electrodes 3 and 4 and the first and second bus bars 5 and 6 are made of a suitable metal or alloy such as Al or AlCu alloy. In this embodiment, the electrodes 3 and 4 and the first and second bus bars 5 and 6 have a structure in which an Al film is laminated on a Ti film. Note that an adhesive layer other than the Ti film may be used.

During driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. Thereby, it is possible to obtain resonance characteristics using the thickness shear mode bulk wave excited in the piezoelectric layer 2.

Further, in the acoustic wave device 1, when the thickness of the piezoelectric layer 2 is d, and the distance between the centers of any adjacent electrodes 3, 4 among the plurality of pairs of electrodes 3, 4 is p, d/p is 0. It is considered to be 5 or less. Therefore, the bulk wave in the thickness shear mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d/p is 0.24 or less, in which case even better resonance characteristics can be obtained.

In addition, when there is a plurality of at least one of the electrodes 3 and 4 as in the present embodiment, that is, when there are one pair of electrodes 3 and 4 and 1.5 or more pairs of electrodes 3 and 4, the electrodes 3 and 4 are adjacent to each other. The distance p between the centers of the electrodes 3 and 4 is the average distance between the centers of the adjacent electrodes 3 and 4.

Since the elastic wave device 1 of this embodiment has the above configuration, even if the logarithm of the electrodes 3 and 4 is reduced in an attempt to achieve miniaturization, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides and has little propagation loss. Further, the reason why the reflector is not required is because the bulk wave in the thickness shear mode is used.

The difference between the Lamb waves used in conventional elastic wave devices and the thickness-shear mode bulk waves will be explained with reference to FIGS. 3A and 3B.

FIG. 3A is a schematic front sectional view for explaining Lamb waves propagating through a piezoelectric film of a conventional acoustic wave device. A conventional elastic wave device is described in, for example, Japanese Patent Publication No. 2012-257019. As shown in FIG. 3A, in the conventional acoustic wave device, waves propagate in the piezoelectric film 201 as indicated by arrows. Here, in the piezoelectric film 201, the first main surface 201a and the second main surface 201b are opposite to each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. It is. The X direction is the direction in which the electrode fingers of the IDT electrodes are lined up. As shown in FIG. 3A, in the Lamb wave, the wave propagates in the X direction as shown. Since it is a plate wave, the piezoelectric film 201 vibrates as a whole, but since the wave propagates in the X direction, reflectors are placed on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is attempted, that is, when the number of logarithms of electrode fingers is reduced, the Q value decreases.

On the other hand, as shown in FIG. 3B, in the elastic wave device 1 of this embodiment, the vibration displacement is in the thickness-slip direction, so the waves are generated between the first principal surface 2a and the second principal surface of the piezoelectric layer 2. It propagates almost in the direction connecting the surface 2b, that is, in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Since resonance characteristics are obtained by the propagation of waves in the Z direction, a reflector is not required. Therefore, no propagation loss occurs when propagating to the reflector. Therefore, even if the number of electrode pairs consisting of electrodes 3 and 4 is reduced in an attempt to promote miniaturization, the Q value is unlikely to decrease.

Note that, as shown in FIG. 4, the amplitude direction of the bulk wave in the thickness shear mode is reversed between the first region 451 included in the intersection region C of the piezoelectric layer 2 and the second region 452 included in the intersection region C. Become. FIG. 4 schematically shows a bulk wave when a voltage is applied between electrode 3 and electrode 4 such that electrode 4 has a higher potential than electrode 3. In FIG. The first region 451 is a region of the intersection region C between a virtual plane VP1 that is perpendicular to the thickness direction of the piezoelectric layer 2 and bisects the piezoelectric layer 2, and the first main surface 2a. The second region 452 is a region of the intersection region C between the virtual plane VP1 and the second principal surface 2b.

As mentioned above, in the elastic wave device 1, at least one pair of electrodes consisting of the electrode 3 and the electrode 4 are arranged, but since the wave is not propagated in the X direction, the elastic wave device 1 is made up of the electrodes 3 and 4. There does not necessarily have to be a plurality of pairs of electrodes. That is, it is only necessary that at least one pair of electrodes be provided.

For example, the electrode 3 is an electrode connected to a hot potential, and the electrode 4 is an electrode connected to a ground potential. However, the electrode 3 may be connected to the ground potential and the electrode 4 may be connected to the hot potential. In this embodiment, at least one pair of electrodes is an electrode connected to a hot potential or an electrode connected to a ground potential, as described above, and no floating electrode is provided.

FIG. 5 is a diagram showing the resonance characteristics of the elastic wave device according to the first embodiment of the present invention. Note that the design parameters of the elastic wave device 1 that obtained this resonance characteristic are as follows.
Piezoelectric layer 2: LiNbO ₃ with Euler angles (0°, 0°, 90°), thickness = 400 nm. When viewed in a direction perpendicular to the length direction of electrodes 3 and 4, the length of the region where electrodes 3 and 4 overlap, that is, the intersection region C = 40 μm, the logarithm of the electrodes consisting of electrodes 3 and 4 = 21 pairs, center distance between electrodes = 3 μm, width of electrodes 3 and 4 = 500 nm, d/p = 0.133.
Insulating layer 7: silicon oxide film with a thickness of 1 μm.
Support substrate 8: Si.

Note that the length of the crossing region C is the dimension along the length direction of the electrodes 3 and 4 of the crossing region C.

In this embodiment, the inter-electrode distances of the electrode pairs consisting of the electrodes 3 and 4 were all made equal in multiple pairs. That is, the electrodes 3 and 4 were arranged at equal pitches.

As is clear from FIG. 5, good resonance characteristics with a fractional band of 12.5% are obtained despite not having a reflector.

By the way, when the thickness of the piezoelectric layer 2 is d, and the center-to-center distance between the electrodes 3 and 4 is p, in this embodiment, d/p is preferably 0.5 or less, as described above. is 0.24 or less. This will be explained with reference to FIG.

A plurality of elastic wave devices were obtained in the same way as the elastic wave devices that obtained the resonance characteristics shown in FIG. 5, except that d/2p was changed. FIG. 6 is a diagram showing the relationship between d/2p and the fractional band of the resonator of the elastic wave device.

As is clear from FIG. 6, when d/2p exceeds 0.25, that is, when d/p>0.5, the fractional band is less than 5% even if d/p is adjusted. On the other hand, if d/2p≦0.25, that is, d/p≦0.5, the fractional bandwidth can be increased to 5% or more by changing d/p within that range. In other words, a resonator having a high coupling coefficient can be constructed. Further, when d/2p is 0.12 or less, that is, when d/p is 0.24 or less, the fractional band can be increased to 7% or more. In addition, by adjusting d/p within this range, it is possible to obtain a resonator with an even wider specific band, and it is possible to realize a resonator with an even higher coupling coefficient. Therefore, as in the elastic wave device of the second aspect of the present disclosure, by setting d/p to 0.5 or less, a resonator having a high coupling coefficient that utilizes the bulk wave of the thickness shear mode is configured. I know what I can do.

Note that, as described above, the at least one pair of electrodes may be one pair, and in the case of one pair of electrodes, the above p is the distance between the centers of adjacent electrodes 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, the average distance between the centers of adjacent electrodes 3 and 4 may be set to p.

Also, regarding the thickness d of the piezoelectric layer, if the piezoelectric layer 2 has thickness variations, a value obtained by averaging the thicknesses may be adopted.

FIG. 7 is a plan view of another elastic wave device according to the first embodiment of the present disclosure. In the acoustic wave device 31, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first main surface 2a of the piezoelectric layer 2. Note that K in FIG. 7 is the intersection width. As described above, in the acoustic wave device 31 of the present invention, the number of pairs of electrodes may be one. Even in this case, if the above-mentioned d/p is 0.5 or less, bulk waves in the thickness shear mode can be excited effectively.

In the elastic wave device 1, preferably, in the plurality of electrodes 3, 4, the above-mentioned adjacent It is desirable that the metallization ratio MR of the electrodes 3 and 4 satisfies MR≦1.75(d/p)+0.075. That is, when viewed in the direction in which adjacent first electrode fingers and second electrode fingers are facing each other, the regions where the plurality of first electrode fingers and the plurality of second electrode fingers overlap intersect. region (excitation region), and when the metallization ratio of the plurality of first electrode fingers and the plurality of second electrode fingers with respect to the intersection region is MR, MR≦1.75 (d/p) + 0.075. It is preferable to meet the requirements. In that case, spurious can be effectively reduced.

This will be explained with reference to FIGS. 8 and 9. FIG. 8 is a reference diagram showing an example of the resonance characteristics of the elastic wave device 1. As shown in FIG. A spurious signal indicated by arrow B appears between the resonant frequency and the anti-resonant frequency. Note that d/p=0.08 and the Euler angles of LiNbO ₃ (0°, 0°, 90°). Further, the metallization ratio MR was set to 0.35.

The metallization ratio MR will be explained with reference to FIG. 1B. In the electrode structure of FIG. 1B, when focusing on a pair of electrodes 3 and 4, it is assumed that only this pair of electrodes 3 and 4 are provided. In this case, the area surrounded by the dashed line C becomes the intersection area. This intersection area is a region where electrode 3 overlaps electrode 4 when electrode 3 and electrode 4 are viewed in a direction perpendicular to the length direction of electrodes 3 and 4, that is, in a direction in which electrode 4 overlaps, and electrode 3 overlaps electrode 4 in electrode 4. and a region between electrodes 3 and 4 where electrodes 3 and 4 overlap. Then, the area of the electrodes 3 and 4 in the intersection region C with respect to the area of this intersection region becomes 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 intersection region.

Note that when multiple pairs of electrodes are provided, MR may be the ratio of the metallized portion included in all the intersection regions to the total area of the intersection regions.

FIG. 9 is a diagram showing the relationship between the fractional band and the amount of phase rotation of spurious impedance normalized by 180 degrees as the magnitude of spurious when a large number of elastic wave resonators are configured according to the present embodiment. be. Note that the specific band was adjusted by variously changing the thickness of the piezoelectric layer and the dimensions of the electrode. Further, although FIG. 9 shows the results when a Z-cut piezoelectric layer made of LiNbO ₃ is used, the same tendency is obtained when piezoelectric layers with other cut angles are used.

In the area surrounded by the ellipse J in FIG. 9, the spurious is as large as 1.0. As is clear from FIG. 9, when the fractional band exceeds 0.17, that is, exceeds 17%, a large spurious with a spurious level of 1 or more will affect the pass band even if the parameters that make up the fractional band are changed. Appear within. That is, as in the resonance characteristics shown in FIG. 8, a large spurious signal indicated by arrow B appears within the band. Therefore, it is preferable that the fractional band is 17% or less. In this case, by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, etc., the spurious can be reduced.

FIG. 10 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional band. Among the above elastic wave devices, various elastic wave devices having different d/2p and MR were constructed and the fractional bands were measured. The hatched area on the right side of the broken line D in FIG. 10 is a region where the fractional band is 17% or less. The boundary between the hatched area and the unhatched area is expressed as MR=3.5(d/2p)+0.075. That is, MR=1.75(d/p)+0.075. Therefore, preferably MR≦1.75 (d/p)+0.075. In that case, it is easy to set the fractional band to 17% or less. More preferably, it is the region to the right of MR=3.5(d/2p)+0.05 indicated by the dashed line D1 in FIG. That is, if MR≦1.75(d/p)+0.05, the fractional band can be reliably set to 17% or less.

FIG. 11 is a diagram showing a map of the fractional band with respect to Euler angles (0°, θ, ψ) of LiNbO ₃ when d/p is brought as close to 0 as possible. The hatched areas in FIG. 11 are areas where a fractional band of at least 5% can be obtained, and the range of the area can be approximated by the following equations (1), (2), and (3). ).

(0°±10°, 0° to 20°, arbitrary ψ)...Formula (1)

(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ² /900) ^1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) ² /900) ^1/2 ] ~ 180°) ...Formula (2)

(0°±10°, [180°-30° (1-(ψ-90) ² /8100) ^1/2 ] ~ 180°, arbitrary ψ) ...Formula (3)

Therefore, in the case of the Euler angle range of the above formula (1), formula (2), or formula (3), the fractional band can be made sufficiently wide, which is preferable.

FIG. 12 is a partially cutaway perspective view for explaining the elastic wave device according to the first embodiment of the present disclosure. The elastic wave device 81 has a support substrate 82 . The support substrate 82 is provided with an open recess on the upper surface. A piezoelectric layer 83 is laminated on the support substrate 82 . Thereby, a cavity 9 is formed. An IDT electrode 84 is provided on the piezoelectric layer 83 above the cavity 9 . Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction. In FIG. 12, the outer periphery of the cavity 9 is indicated by a broken line. Here, the IDT electrode 84 includes first and second bus bars 84a and 84b, an electrode 84c as a plurality of first electrode fingers, and an electrode 84d as a plurality of second electrode fingers. The plurality of electrodes 84c are connected to the first bus bar 84a. The plurality of electrodes 84d are connected to the second bus bar 84b. The plurality of electrodes 84c and the plurality of electrodes 84d are interposed with each other.

In the elastic wave device 81, by applying an alternating current electric field to the IDT electrode 84 on the cavity 9, a Lamb wave as a plate wave is excited. Since the reflectors 85 and 86 are provided on both sides, the resonance characteristic due to the Lamb wave described above can be obtained.

In this way, the elastic wave device of the present disclosure may utilize plate waves.

(Second embodiment)
An elastic wave device according to a second embodiment will be described. In the second embodiment, descriptions of contents that overlap with those in the first embodiment will be omitted as appropriate. In the second embodiment, the contents described in the first embodiment can be applied.

Problems with conventional elastic wave devices will be explained. FIG. 27 is a schematic plan view of an example of a conventional elastic wave device. 28 to 33 are end views showing the manufacturing process of a conventional elastic wave device, and are schematic end views corresponding to a section of the elastic wave device shown in FIG. 27 taken along the line EE. FIG. 34 is a schematic end view of the elastic wave device shown in FIG. 27 taken along line EE.

An acoustic wave device 600 is known in which a piezoelectric layer 620 covers a cavity 610B, so that a portion of the piezoelectric layer 620 facing the cavity 610B is configured as a membrane 621 (see FIGS. 27 and 34). An example of a method for manufacturing the acoustic wave device 600 having the cavity 610B will be described below with reference to FIGS. 28 to 34.

First, as shown in FIG. 28, a sacrificial layer 650 is formed on one main surface 620A of the piezoelectric layer 620. The sacrificial layer 650 is formed, for example, by patterning a resist and removing the resist by etching.

Next, as shown in FIG. 29, a bonding layer 660 is laminated on one main surface 620A of the piezoelectric layer 620. At this time, the sacrificial layer 650 is covered with the bonding layer 660.

Next, as shown in FIG. 30, a support substrate 670 is bonded to the bonding layer 660. The support member 610 is formed by the bonding layer 660 and the support substrate 670.

Next, as shown in FIG. 31, the piezoelectric layer 620 is thinned by grinding or the like.

Next, as shown in FIG. 32, an IDT electrode 630 and a laminated electrode 640 are formed on the other main surface 620C (the back surface of the one main surface 620A) of the piezoelectric layer 620 by lift-off or the like. Although not shown in FIG. 32, the IDT electrode 630 and the laminated electrode 640 are electrically connected. FIG. 32 shows a first electrode finger 633 and a second electrode finger 634 of the IDT electrode 630.

Next, as shown in FIG. 33, a through hole 620B is formed in the piezoelectric layer 620. The through hole 620B is formed by performing a known process such as resist patterning, dry etching, and resist removal.

Next, after the surface is protected by resist patterning, the sacrificial layer 650 is removed, and after the sacrificial layer 650 is removed, the resist that protects the surface is removed. In this manufacturing method, an etching solution permeates into the sacrificial layer 650 through the through hole 620B, and the sacrificial layer 650 is dissolved by the etching solution. The dissolved sacrificial layer 650 is discharged to the outside through the through hole 620B. As a result, as shown in FIG. 34, a cavity 610B is formed at the location where the sacrificial layer 650 was previously present, and a portion of the piezoelectric layer 620 facing the cavity 610B is configured as a membrane 621. . As a result, an elastic wave device 600 shown in FIGS. 27 and 34 is completed.

In the acoustic wave device 600 shown in FIGS. 27 and 34, the IDT electrode 630 includes a first busbar electrode 631 and a second busbar electrode 632 facing each other, and a plurality of first electrode fingers 633 connected to the first busbar electrode 631. and a plurality of second electrode fingers 634 connected to the second bus bar electrode 632. The plurality of first electrode fingers 633 and the plurality of second electrode fingers 634 are interposed with each other, and adjacent first electrode fingers 633 and second electrode fingers 634 constitute a pair of electrode sets. The first electrode finger 633 and the second electrode finger 634 are on the membrane 621.

Since the membrane 621 is thin, cracks may occur. For example, if a crack that occurs at a position 680 extends along the width direction as indicated by the broken line arrow in FIG. 27, there is a risk that the first electrode finger 633 will break. Depending on the position where the crack occurs, the second electrode finger 634 may also break. If the first electrode finger 633 or the second electrode finger 634 is disconnected, the filter characteristics of the elastic wave device 600 may change, and the characteristics of the elastic wave device 600 may deteriorate. For example, if the base end of the first electrode finger 633A is disconnected, the filter characteristics change because no capacitance is added to the area between the first electrode finger 633A and the second electrode finger 634A.

In particular, the second electrode fingers 634 are not present on both sides of the base end of the first electrode fingers 633 in the width direction, and the first electrode fingers 633 are not present on both sides of the base end of the second electrode fingers 634 in the width direction. not exist. Therefore, the strength of the membrane 621 near the base end portions of the first electrode finger 633 and the second electrode finger 634 is weaker than other parts of the membrane 621, and cracks are likely to occur.

Furthermore, if the base end portions of the first electrode finger 633 and the second electrode finger 634 are disconnected, the entirety of the disconnected first electrode finger 633 and second electrode finger 634 ceases to function. Therefore, the characteristics of the elastic wave device 600 may deteriorate significantly compared to a case where a wire other than the base end is disconnected.

In the elastic wave device of the second embodiment of the present disclosure, the possibility of disconnection of the first electrode finger and the second electrode finger can be reduced. Thereby, deterioration of the characteristics of the elastic wave device can be reduced.

FIG. 13 is a schematic plan view of an elastic wave device according to a second embodiment of the present disclosure. FIG. 14 is a schematic end view of the elastic wave device shown in FIG. 13 taken along line AA.

As shown in FIGS. 13 and 14, the acoustic wave device 100 includes a support member 110, a piezoelectric layer 120, an IDT electrode 130, and a laminated electrode 140. The support member 110 corresponds to the support member 8 of the first embodiment. The piezoelectric layer 120 corresponds to the piezoelectric layer 2 of the first embodiment.

The support member 110 has a thickness in the stacking direction D11. The stacking direction D11 is the thickness direction of the support member 110, and means the direction in which the support member 110 and the piezoelectric layer 120 are stacked. Note that, similarly to the first embodiment, an insulating layer may be interposed between the support member 110 and the piezoelectric layer 120.

The support member 110 is made of silicon, glass, crystal, or alumina, for example. In the second embodiment, the support member 110 is made of silicon oxide (SiOx), for example. Note that, as in the first embodiment, the support member 110 includes a support substrate (e.g., corresponding to the support substrate 8 in the first embodiment) and an intermediate layer provided on the support substrate (e.g., in the first embodiment). (corresponding to the insulating layer 7 in).

The support member 110 has a recess 111. The recessed portion 111 is recessed from one main surface 110A of the support member 110 in the stacking direction D11. A space defined by the recess 111 and one main surface 120A of the piezoelectric layer 120 is a cavity 110B. That is, the support member 110 has a cavity 110B on one main surface 110A. The cavity 110B corresponds to the cavity 9 of the first embodiment.

The piezoelectric layer 120 is laminated on the support member 110. One main surface 120A of the piezoelectric layer 120 is in contact with one main surface 110A of the support member 110. That is, the piezoelectric layer 120 is provided on one main surface 110A of the support member 110. The piezoelectric layer 120 closes the recess 111 of the support member 110.

The piezoelectric layer 120 has a membrane 121. The membrane 121 is a portion of the piezoelectric layer 120 that overlaps the cavity 110B when viewed from the stacking direction D11 (in other words, when viewed from above in the stacking direction D11). In other words, the membrane 121 is a portion of the piezoelectric layer 120 that is not in contact with the one main surface 110A of the support member 110 when viewed from above in the stacking direction D11. The cavity 110B can also be said to be a space partitioned into the recess 111 and the membrane 121. 13, FIG. 14, and FIG. 27 described above (and FIG. 16, FIG. 17, FIG. 19, FIG. 20, FIG. 22, FIG. 23, FIG. 25, and FIG. Boundaries with other parts are indicated by broken lines.

The shape of the membrane 121 when viewed in plan in the stacking direction D11 depends on the shape of the cavity 110B. The shapes of the membrane 121 and the cavity 110B are not limited to the shapes shown in FIGS. 13 and 14.

The piezoelectric layer 120 is made of, for example, lithium niobate (LiNbOx) or lithium tantalate (LiTaOx).

As shown in FIG. 13, the piezoelectric layer 120 has two through holes 120B. The through hole 120B penetrates the piezoelectric layer 120 in the stacking direction D11. The through hole 120B is formed at a position overlapping the cavity 110B when viewed from above in the stacking direction D11. The cavity 110B communicates with the outside of the acoustic wave device 100 via the through hole 120B. Note that the number of through holes 120B is not limited to two.

As shown in FIGS. 13 and 14, the IDT electrode 130 is laminated on the other main surface 120C of the piezoelectric layer 120. The other main surface 120C is the back surface of the one main surface 120A. In the second embodiment, the IDT electrode 130 has a first busbar electrode 131 and a second busbar electrode 132 facing each other, a first electrode finger 133 connected to the first busbar electrode 131, and a second busbar electrode 132. It has a second electrode finger 134 to be connected, and a reinforcing electrode 135 provided on the first electrode finger 133 and the second electrode finger 134. At least one first electrode finger 133 and at least one second electrode finger 134 are interposed with each other, and adjacent first electrode fingers 133 and second electrode fingers 134 constitute a pair of electrode sets. ing.

The first busbar electrode 131 corresponds to the electrode 5 of the first embodiment. The second busbar electrode 132 corresponds to the electrode 6 of the first embodiment. The first electrode finger 133 corresponds to the electrode 3 of the first embodiment. The second electrode finger 134 corresponds to the electrode 4 of the first embodiment.

As shown in FIG. 13, when viewed in plan in the stacking direction D11, at least a portion of the IDT electrode 130 is provided on the other main surface 120C of the piezoelectric layer 120 at a position overlapping with the cavity 110B. In the second embodiment, when viewed in plan in the stacking direction D11, the first electrode finger 133, the second electrode finger 134, and the reinforcing electrode 135 of the IDT electrode 130 are provided at a position overlapping with the cavity 110B. There is.

Each of the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134 are arranged to overlap when viewed from the electrode finger facing direction D12 (in other words, when viewed from the side in the electrode finger facing direction D12). Moreover, each of the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134 is arranged to extend in the electrode finger extension direction D13. The electrode finger facing direction D12 is a direction that intersects with the stacking direction D11 and is a direction along the other main surface 120C of the piezoelectric layer 120. The electrode finger extending direction D13 is a direction that intersects with the lamination direction D11 and a direction that intersects with the electrode finger facing direction D12. In the second embodiment, the stacking direction D11, the electrode finger facing direction D12, and the electrode finger extending direction D13 are orthogonal to each other.

When viewed in plan in the stacking direction D11, the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134 are arranged adjacent to each other. Further, when viewed from the side in the electrode finger facing direction D12, the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134 are arranged to overlap with each other. That is, at least one first electrode finger 133 and at least one second electrode finger 134 are arranged alternately along the electrode finger opposing direction D12. Adjacent first electrode fingers 133 and second electrode fingers 134 are arranged to face each other in the electrode finger facing direction D12, and constitute a pair of electrode sets.

Each of the plurality of first electrode fingers 133 extends from the first busbar electrode 131 toward the second busbar electrode 132 along the electrode finger extension direction D13. The base end portions of the plurality of first electrode fingers 133 are connected to the first busbar electrode 131. On the other hand, the tips of the plurality of first electrode fingers 133 are not connected to the second busbar electrode 132. That is, the tips of the plurality of first electrode fingers 133 are separated from the second busbar electrode 132.

Each of the plurality of second electrode fingers 134 extends from the second busbar electrode 132 toward the first busbar electrode 131 along the electrode finger extension direction D13. The base end portions of the plurality of second electrode fingers 134 are connected to the second busbar electrode 132. On the other hand, the tips of the plurality of second electrode fingers 134 are not connected to the first busbar electrode 131. That is, the tips of the plurality of second electrode fingers 134 are separated from the first busbar electrode 131.

The IDT electrode 130 has an intersection region (excitation region) C1 and a pair of gap regions C2. The intersection area C1 is an area where the adjacent first electrode finger 133 and second electrode finger 134 overlap when viewed from the side in the electrode finger opposing direction D12. The gap region C2 is a region where adjacent first electrode fingers 133 and second electrode fingers 134 do not overlap when viewed from the side in the electrode finger opposing direction D12. That is, in the plurality of first electrode fingers 133, the gap region C2 is a region on the first bus bar electrode 131 side with respect to the intersection region C1. Furthermore, in the plurality of second electrode fingers 134, the gap region C2 is a region on the second bus bar electrode 132 side with respect to the intersection region C1. In other words, the pair of gap regions C2 connects the gap between the tip of the first electrode finger 133 and the second busbar electrode 132 and the gap between the tip of the second electrode finger 134 and the first busbar electrode 131. It is an area.

The reinforcing electrodes 135 are provided on the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134. That is, the reinforcing electrode 135 is in contact with the first electrode finger 133 and the second electrode finger 134. In the second embodiment, the reinforcing electrode 135 is laminated on each first electrode finger 133 and on each second electrode finger 134, as shown in FIG.

FIG. 15 is an enlarged view of the portion surrounded by a dashed line in FIG. 13.

As shown in FIGS. 13 to 15, the reinforcing electrode 135 is provided on the membrane 121. That is, when viewed from above in the stacking direction D11, the reinforcing electrode 135 overlaps the cavity 110B. That is, in the second embodiment, the entire portion of the reinforcing electrode 135 overlaps with the cavity 110B when viewed in plan in the stacking direction D11.

Furthermore, when viewed in plan in the stacking direction D11, the reinforcing electrode 135 overlaps both the intersection region C1 and the gap region C2. That is, when viewed in plan in the stacking direction D11, a portion of the reinforcing electrode 135 is provided on the gap region C2.

Here, as described above, in the second embodiment, the reinforcing electrode 135 is provided at a position overlapping with the cavity 110B when viewed in plan in the stacking direction D11. That is, in the second embodiment, the reinforcing electrode 135 on the gap region C2 overlaps with the cavity portion 110B when viewed in plan in the stacking direction D11.

Note that in the second embodiment, the reinforcing electrode 135 overlaps both the intersection region C1 and the gap region C2 when viewed in plan in the stacking direction D11, but the invention is not limited to this. For example, the reinforcing electrode 135 may overlap only the gap region C2 and not the intersection region C1. That is, when viewed in plan in the stacking direction D11, the entire reinforcing electrode 135 may be provided on the gap region C2. As described above, at least a portion of the reinforcing electrode 135 may be provided on the gap region C2 when viewed in plan in the stacking direction D11.

Note that the reinforcing electrode 135 may be provided other than on the first electrode finger 133 or on the second electrode finger 134. For example, the reinforcing electrode 135 may be provided so as to contact the sides of the first electrode finger 133 and the second electrode finger 134. In other words, the reinforcing electrode 135 may be provided adjacent to the first electrode finger 133 and the second electrode finger 134 in the electrode finger opposing direction D12. Further, for example, the reinforcing electrode 135 may be provided so as to cover the sides and top of the first electrode finger 133 and the second electrode finger 134.

In the second embodiment, the reinforcing electrodes 135 are provided on all of the plurality of first electrode fingers 133 and all of the plurality of second electrode fingers 134. However, the reinforcing electrode 135 may be provided on some of the first electrode fingers 133 of the plurality of first electrode fingers 133, or may be provided on some of the second electrode fingers 134 of the plurality of second electrode fingers 134. It may also be provided on the finger 134. That is, the reinforcing electrode 135 is provided on at least some of the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134.

As shown in FIGS. 13 and 14, the laminated electrode 140 is laminated on the other main surface 120C of the piezoelectric layer 120, the first busbar electrode 131 of the IDT electrode 130, and the second busbar electrode 132 of the IDT electrode 130. ing. In the second embodiment, the laminated electrode 140 has two laminated electrodes 141 and 142. The laminated electrode 141 is laminated on the other main surface 120C of the piezoelectric layer 120 and the first busbar electrode 131 of the IDT electrode 130. The laminated electrode 142 is laminated on the other main surface 120C of the piezoelectric layer 120 and the second busbar electrode 132 of the IDT electrode 130.

If a crack occurs in the membrane 121, there is a risk that the first electrode finger 133 or the second electrode finger 134 will be disconnected due to the crack. However, according to the second embodiment, since the first electrode finger 133 and the second electrode finger 134 are reinforced by the reinforcing electrode 135, the possibility of disconnection of the first electrode finger 133 and the second electrode finger 134 is reduced. It can be lowered. Further, even if a portion of the first electrode finger 133 near the first bus bar electrode 131 is disconnected, electrical continuity between the first electrode finger 133 and the first bus bar electrode 131 can be ensured by the reinforcing electrode 135. Similarly, even if a portion of the second electrode finger 134 near the second bus bar electrode 132 is disconnected, electrical continuity between the second electrode finger 134 and the second bus bar electrode 132 can be ensured by the reinforcing electrode 135.

If a crack occurs in the vicinity of the first busbar electrode 131 or the second busbar electrode 132 in the membrane 121 and the crack extends along the electrode finger opposing direction D12, the first electrode finger 133 or the second busbar electrode 132 There is a risk that the electrode fingers 134 may be disconnected. However, as described above, the reinforcing electrode 135 can reduce the possibility of disconnection of the first electrode finger 133 and the second electrode finger 134.

As described above, it is possible to suppress fluctuations in the generated capacitance due to disconnection of the first electrode finger 133 and the second electrode finger 134, and thus it is possible to reduce unintended characteristic changes of the acoustic wave device 100.

(Third embodiment)
FIG. 16 is a schematic plan view of an elastic wave device according to a third embodiment of the present disclosure. FIG. 17 is a schematic end view of the elastic wave device shown in FIG. 16 taken along line BB. FIG. 18 is an enlarged view of a portion surrounded by a dashed line in FIG. 16.

The elastic wave device 100A according to the third embodiment differs from the elastic wave device 100 according to the second embodiment in that the reinforcing electrodes extend to the first busbar electrode 131 and the second busbar electrode 132. Hereinafter, differences from the second embodiment will be explained. Points in common with the elastic wave device 100 according to the second embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted in principle and will be explained as necessary.

As shown in FIGS. 16 to 18, the IDT electrode 130 of the acoustic wave device 100A has a reinforcing electrode 135A instead of the reinforcing electrode 135.

The reinforcing electrode 135A is provided on the first busbar electrode 131 and the second busbar electrode 132 in addition to the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134. In this respect, the reinforcing electrode 135A is provided on the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134, while the reinforcing electrode 135A is not provided on the first busbar electrode 131 and the second busbar electrode 132. is different.

The reinforcing electrode 135A provided on the first electrode finger 133 extends above the first busbar electrode 131. Furthermore, the reinforcing electrode 135A provided on the second electrode finger 134 extends above the second busbar electrode 132. That is, the reinforcing electrode 135A is provided from above the first electrode finger 133 to above the first bus bar electrode 131. Further, the reinforcing electrode 135A is provided from above the second electrode finger 134 to above the second busbar electrode 132.

Here, as described above, in the second embodiment, the entire portion of the reinforcing electrode 135 overlaps with the cavity 110B when viewed in plan in the stacking direction D11. One

On the other hand, in the third embodiment, the first electrode fingers 133 and the second electrode fingers 134 are provided at positions overlapping with the cavity 110B when viewed in plan in the stacking direction D11. On the other hand, when viewed in plan in the stacking direction D11, the first busbar electrode 131 and the second busbar electrode 132 are provided at positions that do not overlap with the cavity 110B.

That is, in the third embodiment, when viewed in plan in the stacking direction D11, the portions of the reinforcing electrode 135A provided in the first electrode fingers 133 and the second electrode fingers 134 overlap with the cavity portion 110B. On the other hand, the portions of the reinforcing electrode 135A provided in the first busbar electrode 131 and the second busbar electrode 132 do not overlap with the cavity 110B. That is, in the third embodiment, a portion of the reinforcing electrode 135 overlaps with the cavity 110B when viewed in plan in the stacking direction D11.

According to the third embodiment, the reinforcing electrode 135A can be made larger in the electrode finger extending direction D13. Further, the reinforcing electrode 135A is provided so as to straddle the first electrode finger 133 and the first bus bar electrode 131, and is provided so as to straddle the second electrode finger 134 and the second bus bar electrode 132. Thereby, the connection between the first electrode finger 133 and the first bus bar electrode 131 can be strengthened. Further, the connection between the second electrode finger 134 and the second bus bar electrode 132 can be strengthened.

(Fourth embodiment)
FIG. 19 is a schematic plan view of an elastic wave device according to a fourth embodiment of the present disclosure. FIG. 20 is a schematic end view of the elastic wave device shown in FIG. 19 taken along line CC. FIG. 21 is an enlarged view of a portion surrounded by a dashed line in FIG. 19.

The elastic wave device 100B according to the fourth embodiment differs from the elastic wave device 100 according to the second embodiment in that the laminated electrode 140 includes a reinforcing electrode 135B. Hereinafter, differences from the second embodiment will be explained. Points in common with the elastic wave device 100 according to the second embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted in principle and will be explained as necessary.

As shown in FIGS. 19 to 21, the laminated electrode 140 of the acoustic wave device 100A is configured integrally with the reinforcing electrode 135B of the IDT electrode 130. The reinforcing electrode 135B extends from the laminated electrode 140 along the electrode finger extension direction D13. The reinforcing electrode 135B extending from the laminated electrode 141 passes over the first bus bar electrode 131 and extends onto the first electrode finger 133. The reinforcing electrode 135B extending from the laminated electrode 142 extends onto the second electrode finger 134 via the second bus bar electrode 132. That is, like the reinforcing electrode 135A of the third embodiment, the reinforcing electrode 135B includes, in addition to the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134, the first busbar electrode 131 and the second busbar electrode 132. It is set in.

According to the fourth embodiment, the reinforcing electrode 135B can be made larger in the electrode finger extending direction D13. Further, the reinforcing electrode 135A is provided so as to straddle the first electrode finger 133 and the first bus bar electrode 131, and is provided so as to straddle the second electrode finger 134 and the second bus bar electrode 132. Thereby, the connection between the first electrode finger 133 and the first bus bar electrode 131 can be strengthened. Further, the connection between the second electrode finger 134 and the second bus bar electrode 132 can be strengthened.

(Fifth embodiment)
FIG. 22 is a schematic plan view of an elastic wave device according to a fifth embodiment of the present disclosure. FIG. 23 is a schematic end view of the elastic wave device shown in FIG. 22 taken along line DD. FIG. 24 is an enlarged view of a portion surrounded by a dashed line in FIG. 22.

The elastic wave device 100C according to the fifth embodiment differs from the elastic wave device 100A according to the second embodiment in that, first, the reinforcing electrode extends to the first busbar electrode 131 and the second busbar electrode 132. It is a point. Since this is similar to the third embodiment, the explanation will be omitted. The elastic wave device 100C according to the fifth embodiment differs from the elastic wave device 100A according to the second embodiment in that, secondly, the width of the reinforcing electrode is shorter than the width of the first electrode finger 133; This point is shorter than the width of the electrode finger 134. The second difference from the second embodiment will be explained below. Points in common with the elastic wave device 100 according to the second embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted in principle and will be explained as necessary.

As shown in FIGS. 22 to 24, the IDT electrode 130 of the acoustic wave device 100C has a reinforcing electrode 135C instead of the reinforcing electrode 135.

Similar to the reinforcing electrode 135A of the third embodiment, the reinforcing electrode 135C is provided on the first bus bar electrode 131 and the second bus bar electrode 132 in addition to the plurality of first electrode fingers 133 and the plurality of second electrode fingers 134. It is being The reinforcing electrode 135C provided on the first electrode finger 133 extends above the first busbar electrode 131. Furthermore, the reinforcing electrode 135C provided on the second electrode finger 134 extends above the second busbar electrode 132.

The width of the reinforcing electrode 135C provided on the first electrode finger 133 is shorter than the width of the first electrode finger 133. That is, the length of the reinforcing electrode 135C provided on the first electrode finger 133 in the electrode finger facing direction D12 is shorter than the length of the first electrode finger 133 in the electrode finger facing direction D12.

The width of the reinforcing electrode 135C provided on the second electrode finger 134 is shorter than the width of the second electrode finger 134. That is, the length of the reinforcing electrode 135C provided on the second electrode finger 134 in the electrode finger facing direction D12 is shorter than the length of the second electrode finger 134 in the electrode finger facing direction D12.

For example, as shown in FIG. 24, the length L1 of the reinforcing electrode 135C provided on the first electrode finger 133 in the electrode finger facing direction D12 is shorter than the length L2 of the first electrode finger 133 in the electrode finger facing direction D12. .

According to the fifth embodiment, even if variations in the dimensional accuracy and positional accuracy of the reinforcing electrode 135C, the first electrode finger 133, and the second electrode finger 134 occur due to tolerances, the reinforcing electrode 135C, the first electrode finger 133, and the second electrode finger 134 The possibility of the reinforcing electrode 135C protruding from the second electrode finger 134 in the electrode finger facing direction D12 (in other words, the possibility that the reinforcing electrode 135C is located outside the first electrode finger 133 and the second electrode finger 134 in the electrode finger facing direction D12) It can be lowered.

(Modifications of each embodiment)
FIG. 25 is a schematic end view of an elastic wave device 100D according to a modified example, taken along line AA in FIG. 14. In each of the embodiments described above, the first busbar electrode 131 and the second busbar electrode 132 do not overlap with the cavity 110B and the membrane 121 when viewed in plan in the stacking direction D11. However, as shown in FIG. 25, the first busbar electrode 131 and the second busbar electrode 132 may overlap the cavity 110B and the membrane 121 when viewed in plan in the stacking direction D11.

FIG. 26 is a schematic end view of an elastic wave device 100E according to a modification, taken along line AA in FIG. 14. In each of the embodiments described above, the entire first electrode finger 133 and the second electrode finger 134 overlap with the cavity 110B when viewed in plan in the stacking direction D11. However, as shown in FIG. 26, when viewed from above in the stacking direction D11, a part of the first electrode finger 133 and a part of the second electrode finger 134 overlap with the cavity 110B, and the remaining part of the first electrode finger 133 overlaps with the cavity 110B. The remaining portion of the second electrode finger 134 does not need to overlap the cavity 110B. That is, when viewed in plan in the stacking direction D11, the first electrode fingers 133 and the second electrode fingers 134 may extend to the outside of the cavity 110B.

(Summary of embodiment)
(1) The elastic wave device of the present disclosure includes:
a support member having a hollow portion on its main surface;
a piezoelectric layer provided on one main surface of the support member;
an IDT electrode provided on the piezoelectric layer and at least partially overlapping the cavity when viewed from the stacking direction of the support member and the piezoelectric layer,
The IDT electrode is
a first busbar electrode;
a second busbar electrode facing the first busbar electrode;
a first electrode finger connected to the first busbar electrode, extending from the first busbar electrode toward the second busbar electrode, and separated from the second busbar electrode;
a second electrode finger connected to the second busbar electrode, extending from the second busbar electrode toward the first busbar electrode, and separated from the first busbar electrode;
a reinforcing electrode provided on at least some of the first electrode fingers and the second electrode fingers;
At least one of the first electrode fingers and at least one of the second electrode fingers are arranged alternately along an electrode finger opposing direction that intersects the electrode finger extending direction,
When viewed from the stacking direction, at least a portion of the reinforcing electrode overlaps with the cavity.

(2) In the elastic wave device of (1),
The IDT electrode includes an intersection area where the first electrode finger and the second electrode finger that are adjacent to each other overlap when viewed from the electrode finger opposing direction, and a tip of the first electrode finger and the second bus bar electrode. and a pair of gap regions, a region connecting the gap between the tips of the second electrode fingers and the first bus bar electrode,
At least a portion of the reinforcing electrode may be provided on the gap region.

(3) In the elastic wave device of (2),
When viewed from the stacking direction, at least a portion of the reinforcing electrode on the gap region may overlap with the cavity.

(4) In any one of the elastic wave devices (1) to (3),
The reinforcing electrode provided on the first electrode finger may extend over the first busbar electrode,
The reinforcing electrode provided on the second electrode finger may extend over the second busbar electrode.

(5) Any one of the elastic wave devices (1) to (4) is
It may further include a laminated electrode laminated on each of the first busbar electrode and the second busbar electrode,
The laminated electrode may include the reinforcing electrode.

(6) In any one of the elastic wave devices (1) to (5),
The length of the reinforcing electrode provided on the first electrode finger in the electrode finger opposing direction may be shorter than the length of the first electrode finger in the electrode finger opposing direction,
The length of the reinforcing electrode provided on the second electrode finger in the direction in which the electrode finger faces may be shorter than the length of the second electrode finger in the direction in which the electrode finger faces.

(7) In any one of the elastic wave devices (1) to (6),
The support member may include a support substrate and an intermediate layer provided on the support substrate.

(8) In any one of the elastic wave devices (1) to (7),
When the thickness of the piezoelectric layer is d, and the center-to-center distance between the adjacent first and second electrode fingers is p, d/p may be 0.5 or less.

(9) In the elastic wave device of (8),
The d/p may be 0.24 or less.

(10) In any one of the elastic wave devices (1) to (9),
When the film thickness of the piezoelectric layer is d, and the center-to-center distance between the adjacent first electrode finger and the second electrode finger is p,
The area of the first electrode finger in the intersection area and the second When the metallization ratio, which is the ratio of the total area to the area of the electrode finger, is MR, MR may satisfy the following formula.
MR≦1.75×(d/p)+0.075

(11) In any one of the elastic wave devices (1) to (10),
The piezoelectric layer may be lithium niobate or lithium tantalate,
The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate may be within the range of the following formula (1), formula (2), or formula (3).
(0°±10°, 0° to 20°, arbitrary ψ) ...Formula (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ² /900) ^1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) ² /900) ^1/2 ] ~ 180°) ...Formula (2)
(0°±10°, [180°-30° (1-(ψ-90) ² /8100) ^1/2 ] ~ 180°, arbitrary ψ) ...Formula (3)

(12) In any one of the elastic wave devices (1) to (11),
It may be configured to be able to utilize bulk waves in thickness shear mode.

(13) In any one of the elastic wave devices (1) to (7),
It may be configured such that plate waves can be used.

Claims (13)

1. a support member having a hollow portion on its main surface;
   a piezoelectric layer provided on one main surface of the support member;
   an IDT electrode provided on the piezoelectric layer and at least partially overlapping the cavity when viewed from the stacking direction of the support member and the piezoelectric layer,
   The IDT electrode is
   a first busbar electrode;
   a second busbar electrode facing the first busbar electrode;
   a first electrode finger connected to the first busbar electrode, extending from the first busbar electrode toward the second busbar electrode, and separated from the second busbar electrode;
   a second electrode finger connected to the second busbar electrode, extending from the second busbar electrode toward the first busbar electrode, and separated from the first busbar electrode;
   a reinforcing electrode provided on at least some of the first electrode fingers and the second electrode fingers;
   At least one of the first electrode fingers and at least one of the second electrode fingers are arranged alternately along an electrode finger facing direction that intersects with the electrode finger extending direction,
   In the acoustic wave device, at least a portion of the reinforcing electrode overlaps with the cavity when viewed from the stacking direction.
2. The IDT electrode includes an intersection area where the first electrode finger and the second electrode finger that are adjacent to each other overlap when viewed from the electrode finger opposing direction, and a tip of the first electrode finger and the second bus bar electrode. and a pair of gap regions, a region connecting the gap between the tips of the second electrode fingers and the first bus bar electrode,
   The acoustic wave device according to claim 1, wherein at least a portion of the reinforcing electrode is provided on the gap region.
3. The acoustic wave device according to claim 2, wherein at least a portion of the reinforcing electrode on the gap region overlaps with the cavity when viewed from the stacking direction.
4. The reinforcing electrode provided on the first electrode finger extends over the first busbar electrode,
   The elastic wave device according to any one of claims 1 to 3, wherein the reinforcing electrode provided on the second electrode finger extends over the second busbar electrode.
5. further comprising a laminated electrode laminated on each of the first busbar electrode and the second busbar electrode,
   The acoustic wave device according to any one of claims 1 to 4, wherein the laminated electrode includes the reinforcing electrode.
6. The length of the reinforcing electrode provided on the first electrode finger in the electrode finger opposing direction is shorter than the length of the first electrode finger in the electrode finger opposing direction,
   6 . The length of the reinforcing electrode provided on the second electrode finger in the direction in which the electrode finger faces is shorter than the length of the second electrode finger in the direction in which the electrode finger faces. 6 . elastic wave device.
7. The acoustic wave device according to any one of claims 1 to 6, wherein the support member includes a support substrate and an intermediate layer provided on the support substrate.
8. From claim 1, wherein d/p is 0.5 or less, where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the adjacent first electrode fingers and the second electrode fingers. 7. The elastic wave device according to any one of 7.
9. The elastic wave device according to claim 8, wherein the d/p is 0.24 or less.
10. When the film thickness of the piezoelectric layer is d, and the center-to-center distance between the adjacent first electrode finger and the second electrode finger is p,
    The area of the first electrode finger in the intersection area and the second The elastic wave device according to any one of claims 1 to 9, wherein MR satisfies the following formula, where MR is a metallization ratio that is a ratio of the total area to the area of the electrode fingers.
    MR≦1.75×(d/p)+0.075
11. The piezoelectric layer is lithium niobate or lithium tantalate,
    Any one of claims 1 to 10, wherein the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate are in the range of the following formula (1), formula (2), or formula (3). The elastic wave device described in .
    (0°±10°, 0° to 20°, arbitrary ψ) ...Formula (1)
    (0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ² /900) ^1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) ² /900) ^1/2 ] ~ 180°) ...Formula (2)
    (0°±10°, [180°-30° (1-(ψ-90) ² /8100) ^1/2 ] ~ 180°, arbitrary ψ) ...Formula (3)
12. The elastic wave device according to any one of claims 1 to 11, configured to be able to utilize a bulk wave in a thickness shear mode.
13. The elastic wave device according to any one of claims 1 to 7, configured to be able to utilize plate waves.

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