WO2023085368A1 - Elastic wave device - Google Patents

Abstract

Provided is an elastic wave device in which the functional electrode is unlikely to sustain damage.　This elastic wave device 10 is equipped with: a support member 13 which includes a support substrate 16; a piezoelectric layer 14 provided on the support member 13; an IDT electrode 11 which has a plurality of electrode fingers and is provided on the piezoelectric layer 14; and a cap member 21 which is provided on the support substrate 16 so as to cover the piezoelectric layer 14. When seen from a plan view in the layering direction of the support member 13 and the piezoelectric layer 14, an acoustic reflector is formed in a position which overlaps at least a portion of the IDT electrode 11. If d is the thickness of the piezoelectric layer 14 and p is the distance between the centers of adjacent electrode fingers, d/p is 0.5 or less. The cap member 21 has a lateral wall section 24, and a top section 25 which is connected to the lateral wall section 24. The top section 25 includes a first main surface 25a which faces the IDT electrode 11, and a second main surface 25b opposite the first main surface 25a. At least the second main surface 25b of the top section 25 of the cap member 21 comprises a metal. One or more projecting parts 19 are further provided which are positioned on the first main surface 25a of the cap member 21 so as not to overlap the IDT electrode 11 when seen from the plan view. The projecting parts 19 comprise a resin.

Description

Acoustic wave device

The present invention relates to elastic wave devices.

Conventionally, acoustic wave devices have been widely used in filters for mobile phones. In recent years, there has been proposed an elastic wave device using a thickness-shear mode bulk wave, as described in Patent Document 1 below. In this elastic wave device, a piezoelectric layer is provided on a support. A pair of electrodes is provided on the piezoelectric layer. The paired electrodes face each other on the piezoelectric layer and are connected to different potentials. By applying an AC voltage between the electrodes, a thickness-shear mode bulk wave is excited.

Patent Document 2 below discloses an example of an elastic wave device using a piezoelectric substrate as a cover member. In this elastic wave device, a plurality of column members are provided between the piezoelectric substrate provided with the excitation electrodes and the piezoelectric substrate as the cover member.

U.S. Patent No. 10491192 WO2017/212742

In an elastic wave device that utilizes the thickness shear mode, when a cover member as described in Patent Document 2 is used, a certain degree of strength can be obtained as an elastic wave device. However, the lid member may chip or crack, and the strength may not be sufficient. In addition, when external pressure is applied to the cover member, the cover member may come into contact with the functional electrode for exciting bulk waves in the thickness-shear mode, and the electrode may be damaged.

An object of the present invention is to provide an elastic wave device in which functional electrodes are less likely to be damaged.

An elastic wave device according to the present invention includes a support member including a support substrate, a piezoelectric layer provided on the support member, an IDT electrode provided on the piezoelectric layer and having a plurality of electrode fingers, a cap member provided on the support substrate so as to cover the piezoelectric layer, and at least a part of the IDT electrode in a plan view along the stacking direction of the support member and the piezoelectric layer; An acoustic reflection portion is formed at an overlapping position, and d/p is 0.5 or less, where d is the thickness of the piezoelectric layer and p is the distance between the centers of the adjacent electrode fingers, and the cap member has a side wall portion and a top plate portion connected to the side wall portion, and the top plate portion has a first main surface facing the IDT electrode and a first main surface facing the first main surface. at least the top plate portion of the cap member is made of metal, and is provided on the first main surface of the cap member, and in plan view At least one protrusion provided so as not to overlap the IDT electrode is further provided, and the protrusion is made of resin.

According to the present invention, it is possible to provide an elastic wave device in which functional electrodes are less likely to be damaged.

FIG. 1 is a schematic front view showing the electrode structure of the element section in the acoustic wave device according to the first embodiment of the present invention, seen through the cap member from the top surface side. FIG. 2 is a schematic cross-sectional view taken along line II in FIG. FIG. 3 is a schematic cross-sectional view along line III-III in FIG. FIG. 4 is a schematic cross-sectional view showing a portion corresponding to line IV-IV in FIG. FIGS. 5A and 5B illustrate an electrode frame forming step, a side wall portion forming step, and a joint member forming step in an example of the method of manufacturing the elastic wave device according to the first embodiment of the present invention. 1 is a schematic front cross-sectional view for. FIGS. 6(a) and 6(b) are schematic front views for explaining a side wall bonding step and a substrate peeling step in an example of the method for manufacturing an acoustic wave device according to the first embodiment of the present invention; It is a sectional view. 7A to 7D show a through electrode forming step, a metal foil singulation step, and a conductive joining member forming step in an example of the method for manufacturing an acoustic wave device according to the first embodiment of the present invention. 5 is a schematic cross-sectional view showing a cross section corresponding to the portion shown in FIG. 4 for explaining the process and the supporting substrate singulation process; FIG. FIG. 8 is a schematic front cross-sectional view of an elastic wave device according to a second embodiment of the invention. FIGS. 9A and 9B are diagrams for explaining the metal layer laminating step and the conductive bonding member forming step in one example of the method for manufacturing the elastic wave device according to the second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a cross section corresponding to the portion shown in FIG. 4; FIG. 10 is a schematic cross-sectional view showing a cross-section corresponding to the portion shown in FIG. 3 and the configuration of the protrusions of the cap member according to the third embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing a cross-section corresponding to the portion shown in FIG. 3 and the configuration of the protrusions of the cap member according to the fourth embodiment of the present invention. FIG. 12 is a schematic front cross-sectional view of an elastic wave device according to a fifth embodiment of the invention. 13 is a schematic cross-sectional view taken along line III-III in FIG. 12. FIG. FIG. 14 is a schematic front cross-sectional view of an elastic wave device according to a sixth embodiment of the invention. 15 is a schematic cross-sectional view along line III-III in FIG. 14. FIG. FIG. 16(a) is a schematic perspective view showing the external appearance of an elastic wave device that utilizes a thickness shear mode bulk wave, and FIG. 16(b) is a plan view showing an electrode structure on a piezoelectric layer. FIG. 17 is a cross-sectional view of a portion taken along line AA in FIG. 16(a). FIG. 18(a) is a schematic front cross-sectional view for explaining a Lamb wave propagating through a piezoelectric film of an acoustic wave device, and FIG. 18(b) is a thickness shear propagating FIG. 2 is a schematic front cross-sectional view for explaining bulk waves in a mode; FIG. 19 is a diagram showing amplitude directions of bulk waves in the thickness shear mode. FIG. 20 is a diagram showing resonance characteristics of an elastic wave device that utilizes bulk waves in a thickness-shear mode. FIG. 21 is a diagram showing the relationship between d/p and the fractional bandwidth of the resonator, where p is the center-to-center distance between adjacent electrodes and d is the thickness of the piezoelectric layer. FIG. 22 is a plan view of an acoustic wave device that utilizes thickness shear mode bulk waves. FIG. 23 is a diagram showing the resonance characteristics of the elastic wave device of the reference example in which spurious appears. FIG. 24 is a diagram showing the relationship between the fractional bandwidth and the amount of phase rotation of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. FIG. 25 is a diagram showing the relationship between d/2p and the metallization ratio MR. FIG. 26 is a diagram showing a map of fractional bandwidth with respect to Euler angles (0°, θ, ψ) of LiNbO ₃ when d/p is infinitely close to 0. FIG. FIG. 27 is a front cross-sectional view of an elastic wave device having an acoustic multilayer film.

Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

It should be noted that each embodiment described in this specification is exemplary, and partial replacement or combination of configurations is possible between different embodiments.

FIG. 1 is a schematic front view showing the electrode structure of the element section in the elastic wave device according to the first embodiment of the present invention, seen through the cap member from the top surface side. FIG. 2 is a schematic cross-sectional view taken along line II in FIG. 1 is a schematic cross-sectional view taken along line II-II in FIG.

As shown in FIGS. 1 and 2, the elastic wave device 10 has a piezoelectric substrate 12 and a cap member 21. As shown in FIGS. As shown in FIG. 2, the piezoelectric substrate 12 has a support member 13 and a piezoelectric layer 14 . In this embodiment, the support member 13 includes a support substrate 16 and an insulating layer 15 . An insulating layer 15 is provided on the support substrate 16 . A piezoelectric layer 14 is provided on the insulating layer 15 . However, the support member 13 may be composed of only the support substrate 16 .

As the material of the support substrate 16, for example, semiconductors such as silicon, ceramics such as aluminum oxide, and the like can be used. As a material for the insulating layer 15, any suitable dielectric such as silicon oxide or tantalum oxide can be used. The piezoelectric layer 14 is, for example, a lithium niobate layer such as a _LiNbO3 layer or a lithium tantalate layer such as a _LiTaO3 layer.

As shown in FIG. 2, the insulating layer 15 is provided with recesses. A piezoelectric layer 14 is provided on the insulating layer 15 so as to close the recess. A hollow portion is thus formed. This hollow portion is the hollow portion 10a. In this embodiment, the support member 13 and the piezoelectric layer 14 are arranged such that a portion of the support member 13 and a portion of the piezoelectric layer 14 face each other with the hollow portion 10a interposed therebetween. However, the recess in the support member 13 may be provided over the insulating layer 15 and the support substrate 16 . Alternatively, the recess provided only in the support substrate 16 may be closed with the insulating layer 15 . The recess may be provided in the piezoelectric layer 14 . Note that the hollow portion 10 a may be a through hole provided in the support member 13 .

An IDT electrode 11 as a functional electrode is provided on the piezoelectric layer 14 . The elastic wave device 10 of this embodiment is an elastic wave resonator configured to be able to use bulk waves in a thickness-shear mode.

At least a portion of the IDT electrode 11 overlaps the hollow portion 10a of the piezoelectric substrate 12 in plan view. In this specification, the term “planar view” refers to viewing from the direction corresponding to the upper side in FIG. 2 along the stacking direction of the support member 13 and the piezoelectric layer 14 . In FIG. 2, for example, of the support substrate 16 and the piezoelectric layer 14, the piezoelectric layer 14 side is the upper side.

In this embodiment, the insulating layer 15, the piezoelectric layer 14, and the IDT electrode 11 constitute the element portion E. As shown in FIG. 1, in the present embodiment, the outer peripheral edge of the element portion E is the outer peripheral edge of the insulating layer 15 in plan view. Outside the peripheral edge of the element portion E, the peripheral edge of the support substrate 16 is positioned. In this specification, unless otherwise specified, the outer peripheral edge means the outer peripheral edge in plan view.

As shown in FIG. 2, a cap member 21 is provided on the support substrate 16 so as to cover the element section E. As shown in FIG. Therefore, the cap member 21 covers the piezoelectric layer 14 . More specifically, a cap member 21 is bonded to a portion of the support substrate 16 outside the outer peripheral edge of the insulating layer 15 .

More specifically, the cap member 21 has an electrode frame 22 , a joint member 23 , a side wall portion 24 and a top plate portion 25 . An electrode frame 22 is provided on the support substrate 16 so as to surround the insulating layer 15 . One ends of the electrode frame 22 and the side wall portion 24 are joined by a joining member 23 . A top plate portion 25 is connected to the other end portion of the side wall portion 24 . Thereby, an internal space surrounded by the support substrate 16 and the cap member 21 is configured. An element portion E is positioned in the internal space. However, the cap member 21 does not necessarily have to have the electrode frame 22 and the joint member 23 . One end of side wall portion 24 may be directly bonded to support substrate 16 .

The dashed-dotted line in FIG. 2 indicates the boundary between the side wall portion 24 and the top plate portion 25. The same applies to schematic front cross-sectional views other than FIG.

The top plate portion 25 faces the piezoelectric layer 14 and the IDT electrodes 11 . Specifically, the top plate portion 25 has a first main surface 25a and a second main surface 25b. The first main surface 25a and the second main surface 25b face each other. Of the first main surface 25a and the second main surface 25b, the first main surface 25a is located on the piezoelectric layer 14 side. The first main surface 25a faces the piezoelectric layer 14 and the IDT electrode 11 with a space therebetween.

In this embodiment, the electrode frame 22 is made of an appropriate metal. The joining member 23 is made of solder. It should be noted that an appropriate material other than solder may be used for the joining member 23 . The side wall portion 24 is made of Cu. Note that the side wall portion 24 may be made of metal other than Cu, appropriate ceramics, or the like. The top plate portion 25 is made of a single metal layer. Specifically, the top plate portion 25 is made of Cu. Note that the top plate portion 25 may be made of a metal other than Cu. Alternatively, the top plate portion 25 may be a laminate. In this case, the second main surface 25b may be made of metal. In the present specification, the term "a certain member is made of a certain material" includes the case where a minute amount of impurity is included to such an extent that the electrical characteristics of the acoustic wave device are not significantly degraded.

FIG. 3 is a schematic cross-sectional view along line III-III in FIG.

As shown in FIGS. 2 and 3, a feature of the present embodiment is that protrusions made of resin are formed on the first main surface 25a of the top plate portion 25 of the cap member 21 so as not to overlap the IDT electrodes 11 in plan view. The reason is that the portion 19 is provided. Thereby, the IDT electrode 11 as a functional electrode is less likely to be damaged. This is explained below.

For example, when mounting the elastic wave device 10 shown in FIG. 2 , the vicinity of the center of the top plate portion 25 of the cap member 21 may be deformed when the elastic wave device 10 is picked up. Specifically, the vicinity of the center of the top plate portion 25 may protrude toward the IDT electrode 11 side. In this case, the protrusions 19 provided on the cap member 21 contact portions other than the IDT electrodes 11 . Specifically, in the present embodiment, the protrusion 19 overlaps the piezoelectric layer 14 in plan view. Therefore, when the top plate portion 25 is deformed, the projecting portion 19 contacts a portion of the piezoelectric layer 14 other than the portion where the IDT electrode 11 is provided. Thereby, the deformation of the cap member 21 can be kept within the elastic deformation range. That is, the protrusion 19 suppresses plastic deformation of the cap member 21 . This can prevent the cap member 21 from coming into contact with the IDT electrode 11, and can make the IDT electrode 11 less likely to be damaged.

By the way, plastic deformation of the cap member 21 is suppressed even when the protrusion 19 is made of metal. On the other hand, since the protrusions 19 are made of resin as in the present embodiment, the piezoelectric layer 14 is less likely to be scratched or cracked even when the protrusions 19 come into contact with the piezoelectric layer 14 . Therefore, the elastic wave device 10 is much less likely to break due to the projecting portion 19 being made of resin.

Furthermore, the second main surface 25b of the cap member 21 is made of metal. As a result, cracks are less likely to occur in the cap member 21 . Therefore, it is possible to make the elastic wave device 10 more effectively difficult to break.

Further details of the configuration of this embodiment will be described below. As shown in FIG. 1, the IDT electrode 11 has a pair of busbars and a plurality of electrode fingers. A pair of busbars is specifically a first busbar 28A and a second busbar 28B. The first busbar 28A and the second busbar 28B face each other. The plurality of electrode fingers are specifically a plurality of first electrode fingers 29A and a plurality of second electrode fingers 29B. One ends of the plurality of first electrode fingers 29A are each connected to the first bus bar 28A. One end of each of the plurality of second electrode fingers 29B is connected to the second bus bar 28B. The plurality of first electrode fingers 29A and the plurality of second electrode fingers 29B are interdigitated with each other. The IDT electrode 11 may be composed of a single-layer metal film, or may be composed of a laminated metal film.

In the following, the first electrode finger 29A and the second electrode finger 29B may be simply referred to as electrode fingers. When the direction in which a plurality of electrode fingers extends is defined as the electrode finger extending direction, and the direction in which adjacent electrode fingers face each other is defined as the electrode finger facing direction, in the present embodiment, the electrode finger extending direction and the electrode finger facing direction are Orthogonal.

In the acoustic wave device 10, d/p is 0.5 or less, where d is the thickness of the piezoelectric layer 14 and p is the center-to-center distance between adjacent electrode fingers. As a result, thickness-shear mode bulk waves are preferably excited.

The intersecting region F is a region where adjacent electrode fingers overlap each other when viewed from the direction in which the electrode fingers are opposed. In an acoustic wave device that utilizes thickness-shear mode bulk waves, the crossover region F includes a plurality of excitation regions. Specifically, when viewed from the electrode-finger facing direction, the excitation region is the region where the adjacent electrode fingers overlap each other and the region between the centers of the adjacent electrode fingers.

By the way, the hollow portion 10a shown in FIG. 2 is the acoustic reflection portion in the present invention. The acoustic reflector can effectively confine the energy of the elastic wave to the piezoelectric layer 14 side. As the acoustic reflection portion, an acoustic reflection film such as an acoustic multilayer film, which will be described later, may be provided.

As shown in FIG. 1, a plurality of wiring electrodes 27 are provided on the piezoelectric layer 14 . Each wiring electrode 27 is electrically connected to the IDT electrode 11 . Each wiring electrode 27 includes a wiring and an electrode pad.

FIG. 4 is a schematic cross-sectional view showing a portion corresponding to line IV-IV in FIG.

A plurality of through electrodes 17 are provided so as to penetrate through the support member 13 and the piezoelectric layer 14 . One end of the through electrode 17 is connected to the electrode pad of the wiring electrode 27 . A bump 18 as a conductive bonding member is bonded to the other end of the through electrode 17 . Incidentally, the conductive bonding member is not limited to the bumps 18 . For example, a conductive adhesive may be used for the conductive joining member. The elastic wave device 10 is joined to a mounting substrate or the like with a conductive joining member.

The through electrodes 17 and the bumps 18 are used as wiring that electrically connects the elastic wave device 10 to the outside. Since the wiring includes the through electrode 17, the area of the piezoelectric layer 14 for forming the wiring can be reduced. Therefore, the acoustic wave device 10 can be made compact.

However, the through electrode 17 only needs to penetrate at least the support member 13 . If the through electrode 17 does not penetrate the piezoelectric layer 14 , the through electrode 17 may be electrically connected to the IDT electrode 11 via a wire or the like passing through the side surface of the piezoelectric layer 14 .

The piezoelectric layer 14 is provided with a plurality of through holes 14c. The through hole 14c is used to remove the sacrificial layer when forming the cavity 10a. However, the through hole 14c may not be provided. For example, through holes may be provided in the support substrate 16 and the insulating layer 15 by backside etching or the like. In this case, the through hole is the cavity. In addition, a step of closing the through hole as the hollow portion is also added.

In this embodiment, as shown in FIG. 3, a pair of protrusions 19 are provided on the first main surface 25a of the top plate portion 25 of the cap member 21. As shown in FIG. As shown in FIG. 2, the pair of protrusions 19 are opposed to each other with the IDT electrode 11 interposed therebetween in plan view. Thereby, contact of the cap member 21 with the IDT electrode 11 can be more reliably suppressed. Therefore, the IDT electrode 11 can be more reliably made difficult to break.

It should be noted that one protrusion 19 may be provided on the first main surface 25a of the top plate portion 25 . Alternatively, three or more projections 19 may be provided. Also in this case, it is preferable that at least one pair of protrusions 19 included in the plurality of protrusions 19 face each other with the IDT electrode 11 interposed therebetween in plan view.

It is preferable that the cap member 21 has the electrode frame 22 and the joint member 23 . It is preferable that the electrode frame 22 and the side wall portion 24 are joined by a joining member 23 . Thereby, the airtightness of the internal space surrounded by the support substrate 16 and the cap member 21 can be improved more reliably.

The second main surface 25b of the top plate portion 25 is preferably made of a ferromagnetic material such as Ni. In this case, the elastic wave device 10 can be fixed using a magnet and conveyed at high speed. This facilitates taping mounting.

An example of a method for manufacturing the elastic wave device 10 according to the first embodiment will be described below. In this example, although not shown, a plurality of elastic wave devices 10 are simultaneously obtained by simultaneously forming a plurality of elastic wave elements and separating them into individual pieces. However, one elastic wave device 10 may be provided.

FIGS. 5A and 5B illustrate an electrode frame forming step, a side wall portion forming step, and a joint member forming step in an example of the method of manufacturing the elastic wave device according to the first embodiment of the present invention. 1 is a schematic front cross-sectional view for. 6(a) and 6(b) are schematic front cross-sectional views for explaining a side wall bonding step and a substrate peeling step in an example of the method for manufacturing an acoustic wave device according to the first embodiment; be. 7A to 7D show a through electrode forming step, a metal foil singulation step, a conductive bonding member forming step, and a supporting step in an example of the method for manufacturing an acoustic wave device according to the first embodiment. FIG. 5 is a schematic cross-sectional view showing a cross section corresponding to the portion shown in FIG. 4 for explaining the substrate singulation step;

As shown in FIG. 5(a), an element portion E is provided on the support substrate 36. As shown in FIG. Next, an electrode frame 22 is formed so as to surround the element portion E. As shown in FIG. The electrode frame 22 can be formed using, for example, a lift-off method. Although not shown, a plurality of element portions E are provided on the support substrate 36, and a plurality of electrode frames 22 are formed so as to surround the plurality of element portions E, respectively.

On the other hand, as shown in FIG. 5(b), the metal foil 35 is attached onto the substrate 38 with the organic adhesive layer 39. Specifically, substrate 38 is a silicon substrate. However, materials other than silicon may be used for the substrate 38 . The metal foil 35 is Cu foil. However, the metal foil 35 may be a foil other than Cu.

Next, a resin layer made of photosensitive resin is formed on the metal foil 35 . Next, the resin layer is exposed and then developed to form a protruding resin portion. The protrusion 19 is formed by thermosetting the resin portion.

Next, after forming a resist pattern on the metal foil 35, the side wall portion 24 is formed by electroplating. Next, the joining member 23 is provided on the side wall portion 24 by performing solder plating. After that, the resist pattern is removed. Although not shown, the metal foil 35 is provided with a plurality of side wall portions 24 and bonding members 23 .

Next, as shown in FIG. 6( a ), the side wall portion 24 is joined to the electrode frame 22 on the support substrate 36 by the joining member 23 . At this time, the electrode frame 22 and the side wall portion 24 are joined by heating and melting the joining member 23 . Next, by removing the organic adhesive layer 39 with a solvent or the like, the metal foil 35 is separated from the substrate 38 as shown in FIG. 6(b).

Next, as shown in FIG. 7A, dry etching is performed from the side of the support substrate 36 on which the element portion E is not formed, thereby penetrating the support substrate 36, the insulating layer 15 and the piezoelectric layer 14. A hole 37 is formed. The through hole 37 is formed to reach the wiring electrode 27 . Next, seed layers are formed in the through holes 37 by performing seed layer plating. Next, the seed layer is plated with Cu to fill the through-hole 37 with the through-electrode 17 . However, the through electrode 17 may be formed of a metal other than Cu.

Next, a resist pattern is formed on the metal foil 35, and the metal foil 35 is singulated by etching to obtain the cap member 21 as shown in FIG. 7(b). Next, as shown in FIG. 7C, bumps 18 are formed as conductive bonding members by solder printing. Next, by separating the support substrate 36 into pieces by dicing or the like, the support substrate 16 is formed as shown in FIG. 7(d). As described above, the elastic wave device 10 is obtained.

FIG. 8 is a schematic front cross-sectional view of an elastic wave device according to a second embodiment.

This embodiment differs from the first embodiment in that the cap member 41 is a laminate. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device 10 of the first embodiment.

As shown in FIG. 8, the top plate portion 45 of the cap member 41 is a laminate. More specifically, a portion corresponding to the top plate portion in the first embodiment is covered with a metal layer. In this embodiment, the portion corresponding to the top plate portion in the first embodiment is the first layer 45A, and the metal layer is the second layer 45B. The first main surface 45a of the top plate portion 45 is the surface of the first layer 45A on the piezoelectric layer 14 side. The second main surface 45b is a surface of the second layer 45B that faces the first main surface 45a and is located on the outermost side of the top plate portion 45 .

The electrode frame 22, the joint member 23, and the portion corresponding to the side wall portion in the first embodiment are also covered with a metal layer. The side wall portion 44 in this embodiment includes the electrode frame 22, the joining member 23, a portion corresponding to the side wall portion in the first embodiment, and a portion covering these in the metal layer.

In this embodiment, the second layer 45B of the top plate portion 45 is a Ni layer. That is, the second main surface 45b of the top plate portion 45 is made of ferromagnetic metal. As a result, the elastic wave device can be fixed using the magnet and conveyed at high speed. This facilitates taping mounting. However, the material of the second layer 45B is not limited to Ni.

Also in this embodiment, similarly to the first embodiment, the projection 19 is provided on the first main surface 45a of the top plate portion 45 . Thereby, the IDT electrode 11 as a functional electrode is less likely to be damaged.

An example of a method for manufacturing an elastic wave device according to the second embodiment will be described below. In addition, for example, part of the manufacturing process of the elastic wave device of the second embodiment can be performed in the same manner as the processes from FIG. 5(a) to FIG. 7(b) shown above. Therefore, the steps after the step corresponding to FIG. 7B are shown below.

9(a) and 9(b) are shown in FIG. 4 for explaining the metal layer laminating step and the conductive bonding member forming step in an example of the method of manufacturing the elastic wave device according to the second embodiment. It is a schematic cross-sectional view showing a cross section corresponding to the portion shown.

As shown in FIG. 9(a), a metal layer is laminated on a member corresponding to the cap member in the first embodiment. Specifically, a Ni layer is laminated on the member by performing electroless plating. Thereby, the cap member 41 in the second embodiment is obtained.

Next, as shown in FIG. 9(b), bumps 18 as conductive joining members are formed by solder printing. Next, the support substrate 36 is separated into individual pieces by dicing or the like to form the support substrate 16 shown in FIG.

A third embodiment and a fourth embodiment, which differ from the first embodiment only in the configuration of the protrusions, will be described below. Furthermore, a fifth embodiment and a sixth embodiment, which differ from the second embodiment only in the configuration of the protrusions, are shown. Also in the third to sixth embodiments, as in the first and second embodiments, the IDT electrodes as functional electrodes are less likely to be damaged.

FIG. 10 is a schematic cross-sectional view showing a cross-section corresponding to the portion shown in FIG. 3 and the configuration of the protrusions of the cap member according to the third embodiment. In addition, in FIG. 10, the position of the IDT electrode in a plan view is indicated by a one-dot chain line. That is, the position of the IDT electrode 11 facing the top plate portion 25 of the gap member 21 is indicated by a dashed line. The same applies to the schematic cross-sectional views of the cap member from FIG. 10 onward.

In this embodiment, the first main surface 25a of the top plate portion 25 of the cap member 21 is provided with a pair of protrusions 19A. The projecting portion 19A has a rod-like shape extending in one direction in plan view. In the present embodiment, the protrusions 19A extend parallel to the extending direction of the electrode fingers. The pair of protrusions 19A are opposed to each other with the IDT electrode 11 interposed therebetween in plan view.

It should be noted that the direction in which the protrusion 19A extends is not limited to the above. The projecting portion 19A may extend obliquely with respect to the extending direction of the electrode finger. The protrusions 19A do not have to extend parallel to each other.

Plastic deformation of the cap member 21 is suppressed even when the protrusion 19A is made of metal. On the other hand, since the projecting portion 19A is made of resin as in the present embodiment, the piezoelectric layer 14 is less likely to be scratched or cracked even when the projecting portion 19A comes into contact with the piezoelectric layer 14 .

FIG. 11 is a schematic cross-sectional view showing a cross-section corresponding to the portion shown in FIG. 3 and the configuration of the protrusions of the cap member according to the fourth embodiment.

In this embodiment, only one protrusion 19B is provided on the first main surface 25a of the top plate portion 25 of the cap member 21. As shown in FIG. The projecting portion 19B has a frame-like shape in plan view. The projecting portion 19B surrounds the IDT electrode 11 in plan view. That is, the projecting portion 19B surrounds the portion of the top plate portion 25 of the gap member 21 facing the IDT electrode 11 .

Plastic deformation of the cap member 21 is suppressed even when the protrusion 19B is made of metal. On the other hand, since the projecting portion 19B is made of resin as in the present embodiment, the piezoelectric layer 14 is less likely to be scratched or cracked even when the projecting portion 19B comes into contact with the piezoelectric layer 14 .

FIG. 12 is a schematic front cross-sectional view of an elastic wave device according to a fifth embodiment. 13 is a schematic cross-sectional view taken along line III-III in FIG. 12. FIG.

As shown in FIGS. 12 and 13, in the present embodiment, the first main surface 45a of the top plate portion 45 of the cap member 41 is provided with a protrusion 19B similar to that of the fourth embodiment. However, the projecting portion 19B is arranged at a position close to the side wall portion 44 . More specifically, as shown in FIG. 13, when the distance between the side wall portion 44 and the protrusion 19B in plan view is defined as a dimension G, the dimension G is larger than the dimension along the thickness direction of the protrusion 19B. is also small.

When an external force is applied to the elastic wave device, the top plate portion 45 of the cap member 41 may be deformed. Specifically, the top plate portion 45 may protrude toward the IDT electrode 11 side. In this case, the protrusion 19B contacts the side wall portion 44 in this embodiment. Thereby, the deformation of the cap member 41 can be more reliably kept within the elastic deformation range. Therefore, the IDT electrode 11 is much less likely to break.

The dimension G is preferably 1/2 or less, more preferably 1/3 or less, of the dimension along the thickness direction of the protrusion 19B. In this case, deformation of the cap member 41 can be suppressed more reliably.

FIG. 14 is a schematic front cross-sectional view of an elastic wave device according to a sixth embodiment. 15 is a schematic cross-sectional view along line III-III in FIG. 14. FIG.

In this embodiment, as in the fourth and fifth embodiments, one frame-shaped projection 19C is provided on the first main surface 45a of the top plate portion 45 of the cap member 41. there is However, the projecting portion 19C is in contact with the side wall portion 44 .

As described above, when an external force is applied to the elastic wave device, the top plate portion 45 of the cap member 41 may protrude toward the IDT electrode 11 side. On the other hand, the projecting portion 19C is in contact with the side wall portion 44. As shown in FIG. Thereby, the deformation of the cap member 41 can be more reliably contained within the elastic deformation range. Therefore, the IDT electrode 11 is much less likely to be damaged.

The details of the thickness slip mode are described below. "Electrodes" in the IDT electrodes to be described later correspond to electrode fingers in the present invention. The supporting member in the following examples corresponds to the supporting substrate in the present invention.

FIG. 16(a) is a schematic perspective view showing the external appearance of an elastic wave device that utilizes a thickness shear mode bulk wave, and FIG. 16(b) is a plan view showing an electrode structure on a piezoelectric layer; FIG. 17 is a cross-sectional view of a portion taken along line AA in FIG. 16(a).

The acoustic wave device 1 has a piezoelectric layer 2 made of LiNbO ₃ . The piezoelectric layer 2 may consist of LiTaO ₃ . The cut angle of LiNbO ₃ and LiTaO ₃ is Z-cut, but may be rotational Y-cut or X-cut. Although the thickness of the piezoelectric layer 2 is not particularly limited, it is preferably 40 nm or more and 1000 nm or less, more 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 major surfaces 2a and 2b facing each other. Electrodes 3 and 4 are provided on the first main surface 2a. Here, the electrode 3 is an example of the "first electrode" and the electrode 4 is an example of the "second electrode". In FIGS. 16( a ) and 16 ( b ), the multiple electrodes 3 are multiple first electrode fingers connected to the first bus bar 5 . The multiple electrodes 4 are multiple second electrode fingers connected to the second bus bar 6 . The plurality of electrodes 3 and the plurality of electrodes 4 are interleaved with each other. The electrodes 3 and 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 the length direction. Both the length direction of the electrodes 3 and 4 and the direction orthogonal to the length direction of the electrodes 3 and 4 are directions crossing 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 crossing the thickness direction of the piezoelectric layer 2 . Moreover, the length direction of the electrodes 3 and 4 may be interchanged with the direction perpendicular to the length direction of the electrodes 3 and 4 shown in FIGS. 16(a) and 16(b). That is, in FIGS. 16A and 16B, the electrodes 3 and 4 may extend in the direction in which the first busbar 5 and the second busbar 6 extend. In that case, the first busbar 5 and the second busbar 6 extend in the direction in which the electrodes 3 and 4 extend in FIGS. 16(a) and 16(b). 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, when the electrodes 3 and 4 are adjacent to each other, it does not mean that the electrodes 3 and 4 are arranged so as to be in direct contact with each other, but that the electrodes 3 and 4 are arranged with a gap therebetween. point to When the electrodes 3 and 4 are adjacent to each other, no electrodes connected to the hot electrode or the ground electrode, including the other electrodes 3 and 4, are arranged between the electrodes 3 and 4. FIG. The logarithms need not be integer pairs, but may be 1.5 pairs, 2.5 pairs, or the like. The center-to-center distance or pitch between the electrodes 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Moreover, the width of the electrodes 3 and 4, that is, the dimension of the electrodes 3 and 4 in the facing direction is preferably in the range of 50 nm or more and 1000 nm or less, more preferably in the range of 150 nm or more and 1000 nm or less. Note that the center-to-center distance between the electrodes 3 and 4 means 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 distance between the center of the electrode 4 in the direction orthogonal to the length direction of the electrode 4. It is the distance connecting the center of the dimension (width dimension) of

In addition, since the Z-cut piezoelectric layer is used in the elastic wave device 1 , 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 with a different cut angle is used as the piezoelectric layer 2 . Here, "perpendicular" is not limited to being strictly perpendicular, but is substantially perpendicular (the angle formed by the direction perpendicular to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, 90° ± 10°). within the range).

A supporting member 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an insulating layer 7 interposed therebetween. The insulating layer 7 and the support member 8 have a frame shape and, as shown in FIG. 17, have through holes 7a and 8a. A cavity 9 is thereby formed. The cavity 9 is provided so as not to disturb the vibration of the excitation region C of the piezoelectric layer 2 . Therefore, the support member 8 is laminated on the second main surface 2b with the insulating layer 7 interposed therebetween at a position not overlapping 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 member 8 can be directly or indirectly laminated to the second main surface 2b of the piezoelectric layer 2 .

The insulating layer 7 is made of silicon oxide. However, in addition to silicon oxide, suitable insulating materials such as silicon oxynitride and alumina can be used. The support member 8 is made of Si. The plane orientation of the surface of Si on the piezoelectric layer 2 side may be (100), (110), or (111). It is desirable that the Si constituting the support member 8 has a high resistivity of 4 kΩcm or more. However, the supporting member 8 can also be constructed using an appropriate insulating material or semiconductor material.

Materials for the support member 8 include, for example, aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and steer. Various ceramics such as tight and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.

The plurality of electrodes 3, 4 and the first and second bus bars 5, 6 are made of appropriate metals or alloys such as Al, AlCu alloys. 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 adhesion layer other than the Ti film may be used.

When driving, an AC voltage is applied between the multiple electrodes 3 and the multiple electrodes 4 . More specifically, an AC voltage is applied between the first busbar 5 and the second busbar 6 . As a result, it is possible to obtain resonance characteristics using bulk waves in the thickness-shear mode excited in the piezoelectric layer 2 . Further, in the acoustic wave device 1, d/p is 0.0, where d is the thickness of the piezoelectric layer 2 and p is the center-to-center distance between any one of the pairs of electrodes 3 and 4 adjacent to each other. 5 or less. Therefore, the thickness-shear mode bulk wave 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.

Since the elastic wave device 1 has the above configuration, even if the logarithm of the electrodes 3 and 4 is reduced in an attempt to reduce the size, the Q value is unlikely to decrease. This is because the propagation loss is small even if the number of electrode fingers in the reflectors on both sides is reduced. The reason why the number of electrode fingers can be reduced is that the thickness-shear mode bulk wave is used. The difference between the Lamb wave used in the elastic wave device and the bulk wave in the thickness shear mode will be described with reference to FIGS. 18(a) and 18(b).

FIG. 18(a) is a schematic front cross-sectional view for explaining a Lamb wave propagating through a piezoelectric film of an acoustic wave device as described in Japanese Unexamined Patent Publication No. 2012-257019. Here, waves propagate through 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 face each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. is. The X direction is the direction in which the electrode fingers of the IDT electrodes are arranged. As shown in FIG. 18(a), the Lamb wave propagates in the X direction as shown. Since it is a plate wave, although the piezoelectric film 201 as a whole vibrates, since the wave propagates in the X direction, reflectors are arranged on both sides to obtain resonance characteristics. Therefore, a wave propagation loss occurs, and the Q value decreases when miniaturization is attempted, that is, when the logarithm of the electrode fingers is decreased.

On the other hand, as shown in FIG. 18(b), in the elastic wave device 1, since the vibration displacement is in the thickness slip direction, the wave is generated on the first main surface 2a and the second main surface of the piezoelectric layer 2. 2b, ie, the Z direction, and resonate. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Further, since resonance characteristics are obtained by propagating waves in the Z direction, propagation loss is unlikely to occur even if the number of electrode fingers of the reflector is reduced. Furthermore, even if the number of electrode pairs consisting of the electrodes 3 and 4 is reduced in an attempt to promote miniaturization, the Q value is unlikely to decrease.

Note that the amplitude direction of the bulk wave in the thickness-shear mode is opposite between the first region 451 included in the excitation region C of the piezoelectric layer 2 and the second region 452 included in the excitation region C, as shown in FIG. Become. FIG. 19 schematically shows bulk waves when a voltage is applied between the electrodes 3 and 4 so that the potential of the electrode 4 is higher than that of the electrode 3 . The first region 451 is a region of the excitation region C between the first main surface 2a and a virtual plane VP1 that is perpendicular to the thickness direction of the piezoelectric layer 2 and bisects the piezoelectric layer 2 . The second region 452 is a region of the excitation region C between the virtual plane VP1 and the second main surface 2b.

As described above, in the acoustic wave device 1, at least one pair of electrodes consisting of the electrodes 3 and 4 is arranged. The number of electrode pairs need not be plural. That is, it is sufficient that at least one pair of electrodes is 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, electrode 3 may also be connected to ground potential and electrode 4 to 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 electrodes are provided.

FIG. 20 is a diagram showing resonance characteristics of the elastic wave device shown in FIG. The design parameters of the elastic wave device 1 with this resonance characteristic are as follows.

Piezoelectric layer 2: LiNbO ₃ with Euler angles (0°, 0°, 90°), thickness = 400 nm.
When viewed in the direction orthogonal to the length direction of the electrodes 3 and 4, the length of the region where the electrodes 3 and 4 overlap, that is, the length of the excitation region C = 40 μm, the number of pairs 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 member 8: Si.

The length of the excitation region C is the dimension along the length direction of the electrodes 3 and 4 of the excitation region C.

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

As is clear from FIG. 20, good resonance characteristics with a fractional bandwidth of 12.5% are obtained in spite of having no 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 the present embodiment, d/p is more preferably 0.5 or less, as described above. is less than or equal to 0.24. This will be described with reference to FIG.

A plurality of elastic wave devices were obtained by changing d/p in the same manner as the elastic wave device that obtained the resonance characteristics shown in FIG. FIG. 21 is a diagram showing the relationship between this d/p and the fractional bandwidth of the acoustic wave device as a resonator.

As is clear from FIG. 21, when d/p>0.5, even if d/p is adjusted, the specific bandwidth is less than 5%. On the other hand, when d/p≤0.5, the specific bandwidth can be increased to 5% or more by changing d/p within that range. can be configured. Further, when d/p is 0.24 or less, the specific bandwidth can be increased to 7% or more. In addition, by adjusting d/p within this range, a resonator with a wider specific band can be obtained, and a resonator with a higher coupling coefficient can be realized. Therefore, by setting d/p to 0.5 or less, it is possible to construct a resonator having a high coupling coefficient using the thickness-shear mode bulk wave.

FIG. 22 is a plan view of an elastic wave device that utilizes thickness-shear mode bulk waves. In elastic wave device 80 , a pair of electrodes having electrode 3 and electrode 4 is provided on first main surface 2 a of piezoelectric layer 2 . Note that K in FIG. 22 is the crossing width. As described above, in the elastic wave device of the present invention, the number of pairs of electrodes may be one. Even in this case, if d/p is 0.5 or less, bulk waves in the thickness-shear mode can be effectively excited.

In the elastic wave device 1, preferably, in the plurality of electrodes 3 and 4, the adjacent excitation region C is an overlapping region when viewed in the direction in which any of the adjacent electrodes 3 and 4 are facing each other. It is desirable that the metallization ratio MR of the mating electrodes 3, 4 satisfy MR≤1.75(d/p)+0.075. In that case, spurious can be effectively reduced. This will be described with reference to FIGS. 23 and 24. FIG. FIG. 23 is a reference diagram showing an example of resonance characteristics of the acoustic wave device 1. As shown in FIG. A spurious signal indicated by an arrow B appears between the resonance frequency and the anti-resonance frequency. Note that d/p=0.08 and the Euler angles of LiNbO ₃ (0°, 0°, 90°). Also, the metallization ratio MR was set to 0.35.

The metallization ratio MR will be explained with reference to FIG. 16(b). In the electrode structure of FIG. 16(b), when focusing attention on the pair of electrodes 3 and 4, it is assumed that only the pair of electrodes 3 and 4 are provided. In this case, the excitation region C is the portion surrounded by the dashed-dotted line. The excitation region C is a region where the electrode 3 and the electrode 4 overlap each other when the electrodes 3 and 4 are viewed in a direction perpendicular to the length direction of the electrodes 3 and 4, i.e., in a facing direction. 3 and an overlapping area between the electrodes 3 and 4 in the area between the electrodes 3 and 4 . The area of the electrodes 3 and 4 in the excitation region C with respect to the area of the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallization portion to the area of the drive region C.

When a plurality of pairs of electrodes are provided, MR may be the ratio of the metallization portion included in the entire excitation region to the total area of the excitation region.

FIG. 24 is a diagram showing the relationship between the fractional bandwidth and the amount of phase rotation of the spurious impedance normalized by 180 degrees as the magnitude of the spurious when a large number of acoustic wave resonators are configured according to this embodiment. be. The ratio band was adjusted by changing the film thickness of the piezoelectric layer and the dimensions of the electrodes. Also, FIG. 24 shows the results when a Z-cut LiNbO ₃ piezoelectric layer is used, but the same tendency is obtained when piezoelectric layers with other cut angles are used.

In the area surrounded by ellipse J in FIG. 24, the spurious is as large as 1.0. As is clear from FIG. 24, when the fractional band exceeds 0.17, that is, when it exceeds 17%, even if a large spurious with a spurious level of 1 or more changes the parameters constituting the fractional band, the passband appear within. That is, as in the resonance characteristics shown in FIG. 23, a large spurious component indicated by arrow B appears within the band. Therefore, the specific bandwidth is preferably 17% or less. In this case, by adjusting the film thickness of the piezoelectric layer 2 and the dimensions of the electrodes 3 and 4, the spurious response can be reduced.

FIG. 25 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth. In the elastic wave device described above, various elastic wave devices having different d/2p and MR were constructed, and the fractional bandwidth was measured. The hatched portion on the right side of the dashed line D in FIG. 25 is the area where the fractional bandwidth is 17% or less. The boundary between the hatched area and the non-hatched area is expressed by 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 bandwidth to 17% or less. More preferably, it is the area on the right side of MR=3.5(d/2p)+0.05 indicated by the dashed-dotted line D1 in FIG. That is, if MR≤1.75(d/p)+0.05, the fractional bandwidth can be reliably reduced to 17% or less.

FIG. 26 is a diagram showing a map of fractional bandwidth with respect to Euler angles (0°, θ, ψ) of LiNbO ₃ when d/p is infinitely close to 0. FIG. The hatched portion in FIG. 26 is a region where a fractional bandwidth of at least 5% or more is obtained, and when the range of the region is approximated, the following formulas (1), (2) and (3) ).

(0°±10°, 0° to 20°, arbitrary ψ) Equation (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°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) ² /8100) ^1/2 ]~180°, arbitrary ψ) Equation (3)

Therefore, in the case of the Euler angle range of formula (1), formula (2), or formula (3), the fractional band can be sufficiently widened, which is preferable. The same applies when the piezoelectric layer 2 is a lithium tantalate layer.

FIG. 27 is a front cross-sectional view of an elastic wave device having an acoustic multilayer film.

In the acoustic wave device 81 , an acoustic multilayer film 82 is laminated on the second main surface 2 b of the piezoelectric layer 2 . The acoustic multilayer film 82 has a laminated structure of low acoustic impedance layers 82a, 82c, 82e with relatively low acoustic impedance and high acoustic impedance layers 82b, 82d with relatively high acoustic impedance. When the acoustic multilayer film 82 is used, the thickness shear mode bulk wave can be confined in the piezoelectric layer 2 without using the cavity 9 in the acoustic wave device 1 . Also in the elastic wave device 81, by setting d/p to 0.5 or less, it is possible to obtain resonance characteristics based on bulk waves in the thickness-shear mode. In the acoustic multilayer film 82, the number of lamination of the low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d is not particularly limited. At least one of the high acoustic impedance layers 82b, 82d should be arranged farther from the piezoelectric layer 2 than the low acoustic impedance layers 82a, 82c, 82e.

The low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d can be made of appropriate materials as long as the acoustic impedance relationship is satisfied. Examples of materials for the low acoustic impedance layers 82a, 82c, 82e include silicon oxide and silicon oxynitride. Materials for the high acoustic impedance layers 82b and 82d include alumina, silicon nitride, and metals.

In the first to sixth embodiments, for example, an acoustic multilayer film 82 shown in FIG. 27 may be provided as an acoustic reflecting film between the support member and the piezoelectric layer. Specifically, the support member and the piezoelectric layer may be arranged such that at least a portion of the support member and at least a portion of the piezoelectric layer face each other with the acoustic multilayer film 82 interposed therebetween. In this case, low acoustic impedance layers and high acoustic impedance layers may be alternately laminated in the acoustic multilayer film 82 . The acoustic multilayer film 82 may be an acoustic reflector in the elastic wave device.

In the elastic wave devices of the first to sixth embodiments that utilize thickness-shear mode bulk waves, d/p is preferably 0.5 or less, and more preferably 0.24 or less, as described above. is more preferred. Thereby, even better resonance characteristics can be obtained. Furthermore, in the excitation regions of the acoustic wave devices of the first to sixth embodiments that utilize thickness shear mode bulk waves, MR≦1.75(d/p)+0.075 is satisfied as described above. is preferred. In this case, spurious can be suppressed more reliably.

The piezoelectric layer in the elastic wave devices of the first to sixth embodiments that utilize thickness shear mode bulk waves is preferably a lithium niobate layer or a lithium tantalate layer. The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the above formula (1), formula (2), or formula (3). is preferred. In this case, the fractional bandwidth can be widened sufficiently.

REFERENCE SIGNS LIST 1 elastic wave device 2 piezoelectric layers 2a, 2b first and second main surfaces 3, 4 electrodes 5, 6 first and second bus bars 7 insulating layer 7a through hole 8 supporting member 8a Through hole 9 Hollow portion 10 Acoustic wave device 10a Hollow portion 11 IDT electrode 12 Piezoelectric substrate 13 Support member 14 Piezoelectric layer 14c Through hole 15 Insulating layer 16 Support substrate 17 Through electrode 18 Bumps 19, 19A to 19C Projection 21 Cap member 22 Electrode frame 23 Joining member 24 Side wall 25 Top plate 25a, 25b First and second main surfaces 27 Wiring electrodes 28A, 28B First and second bus bars 29A, 29B First and second electrode fingers 35 Metal foil 36 Support substrate 37 Through hole 38 Substrate 39 Organic adhesive layer 41 Cap member 44 Side wall portion 45 Top plate portions 45A, 45B... First and second layers 45a, 45b... First and second main surfaces 80, 81... Elastic wave device 82... Acoustic multilayer films 82a, 82c, 82e... Low acoustic impedance layer 82b, 82d... High acoustic impedance layer 201... Piezoelectric films 201a, 201b... First and second main surfaces 451, 452... First and second regions C... Excitation region E... Element part F... Intersection region VP1... Virtual plane

Claims (14)

1. a support member including a support substrate;
   a piezoelectric layer provided on the support member;
   an IDT electrode provided on the piezoelectric layer and having a plurality of electrode fingers;
   a cap member provided on the support substrate so as to cover the piezoelectric layer;
   with
   an acoustic reflection portion is formed at a position that overlaps at least a part of the IDT electrode in a plan view viewed along the stacking direction of the support member and the piezoelectric layer,
   where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the adjacent electrode fingers, d/p is 0.5 or less,
   The cap member has a side wall portion and a top plate portion connected to the side wall portion, and the top plate portion has a first main surface facing the IDT electrode and the first main surface. a second main surface facing the surface, wherein at least the second main surface of the top plate portion of the cap member is made of metal;
   further comprising at least one protrusion provided on the first main surface of the cap member and provided so as not to overlap the IDT electrode in plan view;
   An elastic wave device, wherein the protrusion is made of resin.
2. comprising a plurality of the protrusions,
   The elastic wave device according to claim 1, wherein the plurality of projections includes a pair of projections facing each other with the IDT electrode interposed therebetween in plan view.
3. The elastic wave device according to claim 1 or 2, wherein the protrusion has a rod-like shape extending in one direction in plan view.
4. The elastic wave device according to claim 1, wherein the protrusion has a frame-like shape and surrounds the IDT electrode in plan view.
5. The elastic wave device according to any one of claims 1 to 4, wherein the protrusion overlaps the piezoelectric layer in plan view.
6. The elastic wave device according to any one of claims 1 to 5, wherein a dimension that is a distance between the side wall portion of the cap member and the protrusion is smaller than a dimension along the thickness direction of the protrusion.
7. The elastic wave device according to claim 6, wherein the protrusion is in contact with the side wall of the cap member.
8. The elastic wave device according to any one of claims 1 to 7, further comprising a through electrode that penetrates at least the support member and is electrically connected to the IDT electrode.
9. The elastic wave device according to any one of claims 1 to 8, wherein the second main surface of the top plate portion of the cap member is made of ferromagnetic metal.
10. The acoustic reflecting portion is a hollow portion, and the supporting member and the piezoelectric layer are arranged such that a portion of the supporting member and a portion of the piezoelectric layer face each other with the hollow portion interposed therebetween. The elastic wave device according to any one of claims 1 to 9.
11. The acoustic reflection part is an acoustic reflection film including a high acoustic impedance layer with relatively high acoustic impedance and a low acoustic impedance layer with relatively low acoustic impedance, and at least a portion of the support member and the The elastic wave device according to any one of claims 1 to 9, wherein the support member and the piezoelectric layer are arranged such that at least part of the piezoelectric layer faces each other with the acoustic reflection film interposed therebetween. .
12. The elastic wave device according to any one of claims 1 to 11, wherein d/p is 0.24 or less.
13. When viewed from a direction orthogonal to the direction in which the plurality of electrode fingers extend, the region where the adjacent electrode fingers overlap each other, and the region between the centers of the adjacent electrode fingers is an excitation region, and the excitation region. The elastic wave device according to any one of claims 1 to 12, wherein MR ≤ 1.75 (d/p) + 0.075 is satisfied when MR is a metallization ratio of the plurality of electrode fingers with respect to .
14. the piezoelectric layer is made of lithium niobate or lithium tantalate,
    3. The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate forming the piezoelectric layer are within the range of the following formula (1), formula (2), or formula (3). 14. The elastic wave device according to any one of 1 to 13.
    (0°±10°, 0° to 20°, arbitrary ψ) Equation (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°) Equation (2)
    (0°±10°, [180°-30°(1-(ψ-90) ² /8100) ^1/2 ]~180°, arbitrary ψ) Equation (3)

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