Elastic wave device

Abstract

Provided is an elastic wave device in which peeling does not readily occur between an IDT electrode and a layer covering the IDT electrode. An elastic wave device (1) is provided with: a support substrate (3); an intermediate layer (4) provided on the support substrate (3); a piezoelectric layer (5) provided on the intermediate layer (4) and having a first main surface (5a) located on the intermediate layer (4) side and a second main surface (5b) facing the first main surface (5a); a first IDT electrode (7) provided on a first main surface (5a) of the piezoelectric layer (5) and embedded in the intermediate layer (4); and a second IDT electrode (27) provided on a second main surface (5b) of the piezoelectric layer (5). The first IDT electrode (7) has a plurality of electrode fingers. Each electrode finger includes a first surface (7a) and a second surface (7b) facing each other in the thickness direction of the electrode finger, and a side surface (7c) connected to the first surface (7a) and the second surface (7b). A side surface (7c) of an electrode finger in the first IDT electrode (7) has a first portion (7d) and a second portion (7e), and in at least one of the electrode fingers, the first portion (7d) and the second portion (7e) have mutually different inclination angles with respect to the thickness direction of the electrode finger.

Description

Technical Field

[0001] The present invention relates to elastic wave devices. Background Art

[0002] In the past, elastic wave devices have been widely used in filters for mobile phones and the like. Patent document 1 below discloses an example of a plate-type waveguide device as an elastic wave device. In one example of the elastic wave device described in patent document 1, IDTs (Interdigital Transducers) are provided on both sides of the piezoelectric layer. Both IDTs are covered by a low-speed wave propagation layer.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-044835 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In elastic wave devices, external forces or thermal stress caused by temperature changes may be applied during manufacturing or use. In elastic wave devices such as those described in Patent Document 1, when such forces are applied, peeling often occurs between the IDT and the low-speed wave propagation layer. In this case, it may be impossible to obtain desired electrical characteristics.

[0008] An object of the present invention is to provide an elastic wave device in which separation is unlikely to occur between an IDT electrode and a layer covering the IDT electrode.

[0009] Technical solutions to solve problems

[0010] The elastic wave device of the present invention comprises: a supporting substrate; an intermediate layer, which is arranged on the supporting substrate; a piezoelectric layer, which is arranged on the intermediate layer and has a first main surface located on the intermediate layer side, and a second main surface opposite to the first main surface; a first IDT electrode, which is arranged on the first main surface of the piezoelectric layer and buried in the intermediate layer; and a second IDT electrode, which is arranged on the second main surface of the piezoelectric layer, wherein the first IDT electrode has a plurality of electrode fingers, each of which includes a first surface and a second surface which are opposite to each other in the thickness direction of the electrode finger, and a side surface connected to the first surface and the second surface, the side surface of the electrode finger in the first IDT electrode has a first part and a second part, and in at least one of the electrode fingers, the first part and the second part are inclined at different angles relative to the thickness direction of the electrode finger.

[0011] Effects of the Invention

[0012] According to the elastic wave device of the present invention, separation is unlikely to occur between the IDT electrode and the layer covering the IDT electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a front cross-sectional view of the elastic wave device according to the first embodiment of the present invention.

[0014] Figure 2 It is a bottom view showing the electrode structure on the first principal surface of the piezoelectric layer in the first embodiment of the present invention.

[0015] Figure 3 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in the elastic wave device according to the first embodiment of the present invention.

[0016] Figure 4 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a second embodiment of the present invention.

[0017] Figure 5 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a third embodiment of the present invention.

[0018] Figure 6 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a fourth embodiment of the present invention.

[0019] Figure 7 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a modification of the fourth embodiment of the present invention.

[0020] Figure 8 It is a schematic plan view of an elastic wave device according to a fifth embodiment of the present invention.

[0021] Fig. 9 It is a graph showing the impedance frequency characteristics in the first embodiment and the fifth embodiment of the present invention.

[0022] Fig.10 It is a schematic plan view of an elastic wave device according to a sixth embodiment of the present invention.

[0023] Fig.11 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a seventh embodiment of the present invention.

[0024] Fig.12 It is a front cross-sectional view of an elastic wave device according to a modified example of the seventh embodiment of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to make the present invention clear.

[0026] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined among different embodiments.

[0027] Figure 1 It is a front cross-sectional view of the elastic wave device according to the first embodiment of the present invention.

[0028] The elastic wave device 1 has a piezoelectric substrate 2. The piezoelectric substrate 2 has a supporting substrate 3, an intermediate layer 4, and a piezoelectric layer 5. In the present embodiment, the intermediate layer 4 is a laminate. More specifically, the intermediate layer 4 has a first layer 4A and a second layer 4B. The first layer 4A of the intermediate layer 4 is provided on the supporting substrate 3. The second layer 4B is provided on the first layer 4A. The piezoelectric layer 5 is provided on the second layer 4B. In addition, the intermediate layer 4 may also be a single-layer dielectric layer, etc.

[0029] The piezoelectric layer 5 has a first principal surface 5a and a second principal surface 5b. The first principal surface 5a and the second principal surface 5b are opposite to each other. Of the first principal surface 5a and the second principal surface 5b, the first principal surface 5a is located on the intermediate layer 4 side. A first IDT electrode 7 is provided on the first principal surface 5a of the piezoelectric layer 5. The first IDT electrode 7 is buried in the intermediate layer 4. On the other hand, a second IDT electrode 27 is provided on the second principal surface 5b of the piezoelectric layer 5.

[0030] Figure 2 1 is a bottom view showing the electrode structure on the first main surface of the piezoelectric layer in the first embodiment. Figure 1 It is along Figure 2 Cross-sectional view of line II in FIG.

[0031] The first IDT electrode 7 has a pair of bus bars and a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19. Specifically, the pair of bus bars is a first bus bar 16 and a second bus bar 17. The first bus bar 16 and the second bus bar 17 are opposite to each other. One end of the plurality of first electrode fingers 18 is connected to the first bus bar 16, respectively. One end of the plurality of second electrode fingers 19 is connected to the second bus bar 17, respectively. The plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interlaced with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials.

[0032] Likewise, Figure 1The second IDT electrode 27 shown also has a pair of bus bars and a plurality of third electrode fingers 28 and a plurality of fourth electrode fingers 29. Specifically, the pair of bus bars of the second IDT electrode 27 is a third bus bar and a fourth bus bar. The third bus bar and the fourth bus bar are opposite to each other. One end of the plurality of third electrode fingers 28 is respectively connected to the third bus bar. One end of the plurality of fourth electrode fingers 29 is respectively connected to the fourth bus bar. The plurality of third electrode fingers 28 and the plurality of fourth electrode fingers 29 are interlaced with each other. The third electrode fingers 28 and the fourth electrode fingers 29 are connected to different potentials.

[0033] Hereinafter, the first electrode finger 18, the second electrode finger 19, the third electrode finger 28, and the fourth electrode finger 29 are sometimes simply described as electrode fingers. In each of the first IDT electrode 7 and the second IDT electrode 27, the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction. In the present embodiment, the electrode finger extension directions of the first IDT electrode 7 and the second IDT electrode 27 are parallel.

[0034] By applying an AC voltage to the first IDT electrode 7 and the second IDT electrode 27, elastic waves are excited. In addition, in the present embodiment, the propagation direction of the elastic wave is orthogonal to the direction in which the electrode fingers extend. A pair of reflectors 15A and 15B are provided on the first principal surface 5a of the piezoelectric layer 5. The reflectors 15A and 15B are opposed to each other with the first IDT electrode 7 sandwiched in a direction orthogonal to the direction in which the electrode fingers extend. Similarly, a pair of reflectors 25A and 25B are provided on the second principal surface 5b. The reflectors 25A and 25B are opposed to each other with the second IDT electrode 27 sandwiched in a direction orthogonal to the direction in which the electrode fingers extend.

[0035] In the present embodiment, the first IDT electrode 7, the reflector 15A and the reflector 15B are formed by stacking Pt layers and Al layers in sequence from the piezoelectric layer 5 side. On the other hand, the second IDT electrode 27, the reflector 25A and the reflector 25B include an Al layer. However, the materials and the number of layers of the first IDT electrode 7, the second IDT electrode 27 and each reflector are not limited to the above. For example, the first IDT electrode 7, the reflector 15A and the reflector 15B may also include more than 3 layers of stacked metal films, or may also include a single-layer metal film. Similarly, the second IDT electrode 27, the reflector 25A and the reflector 25B may also include a stacked metal film.

[0036] Figure 3 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in the elastic wave device according to the first embodiment.

[0037] Each electrode finger of the first IDT electrode 7 includes a first surface 7a, a second surface 7b, and a side surface 7c. The first surface 7a and the second surface 7b are opposite to each other in the thickness direction of each electrode finger. Of the first surface 7a and the second surface 7b, the first surface 7a is located on the piezoelectric layer 5 side. The side surface 7c is a surface connecting the first surface 7a and the second surface 7b. The side surface 7c of each electrode finger has a first portion 7d and a second portion 7e. More specifically, the first portion 7d and the second portion 7e are arranged in the thickness direction of each electrode finger. Of the first portion 7d and the second portion 7e, the first portion 7d is located on the piezoelectric layer 5 side. The end of the first portion 7d on the support substrate 3 side is connected to the end of the second portion 7e on the piezoelectric layer 5 side. In the present embodiment, of the side surfaces 7c, the first portion 7d is the side surface of the Pt layer, and the second portion 7e is the side surface of the Al layer.

[0038] Here, the angle θ at which the side surface 7c of the electrode finger is inclined relative to the thickness direction of the electrode finger is set as the inclination angle. When the side surface 7c of the electrode finger is inclined so that the width of the electrode finger becomes narrower as it is away from the piezoelectric layer 5, the inclination angle is set to a positive value. On the other hand, when the side surface 7c is inclined so that the width of the electrode finger becomes wider as it is away from the piezoelectric layer 5, the inclination angle is set to a negative value. The width of the electrode finger is the dimension of the electrode finger along the direction orthogonal to the extension direction of the electrode finger. In addition, in the first IDT electrode 7 of the elastic wave device 1, the side surface 7c of each electrode finger is inclined so that the width of the electrode finger becomes narrower as it is away from the piezoelectric layer 5.

[0039] The present embodiment is characterized in that, in the first IDT electrode 7 embedded in the intermediate layer 4, the side surface 7c of each electrode finger has a first portion 7d and a second portion 7e, and the inclination angles of the first portion 7d and the second portion 7e are different from each other. In addition, as long as the inclination angles of the first portion 7d and the second portion 7e are different from each other in at least one electrode finger, it is sufficient. As a result, the contact area between the electrode finger and the intermediate layer 4 can be increased, and the adhesion between the electrode finger and the intermediate layer 4 can be improved. Therefore, the bonding force between the first IDT electrode 7 and the intermediate layer 4 can be improved. Therefore, it is not easy to peel off between the first IDT electrode 7 and the intermediate layer 4 covering the first IDT electrode 7.

[0040] In addition, the first IDT electrode 7 can be formed by, for example, a lift-off method using a vacuum evaporation method, a sputtering method, or the like. At this time, the film forming speed when forming the portion including the first portion 7d in each electrode finger and the film forming speed when forming the portion including the second portion 7e can be made different from each other, so that the inclination angles of the first portion 7d and the second portion 7e are different from each other. However, the method of forming the first IDT electrode 7 is not limited to the above. For example, the inclination angles of the first portion 7d and the second portion 7e can also be made different from each other by etching or the like.

[0041] Hereinafter, further details of the structure of this embodiment will be described.

[0042] like Figure 2 As shown in FIG. 1 , in the first IDT electrode 7, when viewed from a direction perpendicular to the extending direction of the electrode fingers, the region where adjacent electrode fingers overlap each other is the intersection region C. Similarly, the second IDT electrode 27 also has an intersection region. The intersection region C of the first IDT electrode 7 and the intersection region of the second IDT electrode 27 overlap when viewed from above. In this specification, the term "viewed from above" refers to a region from the direction corresponding to the direction of the electrode fingers. Figure 1 Observe from the top of the middle. Figure 1 For example, the piezoelectric layer 5 is located on the upper side of the piezoelectric layer 5 and the supporting substrate 3 .

[0043] The centers of the plurality of electrode fingers in the intersection region C of the first IDT electrode 7 and the centers of the plurality of electrode fingers in the intersection region of the second IDT electrode 27 overlap when viewed from above. However, it is sufficient that at least a portion of the plurality of electrode fingers of the first IDT electrode 7 and at least a portion of the plurality of electrode fingers of the second IDT electrode 27 overlap when viewed from above. In addition, it is sufficient that the intersection regions of both sides overlap when viewed from above within an error range that does not significantly affect the electrical characteristics of the elastic wave device. Therefore, the misalignment due to manufacturing deviation is included in the overlap of the intersection regions of both sides when viewed from above.

[0044] The electrode finger pitches of the first IDT electrode 7 and the second IDT electrode 27 are the same. The electrode finger pitch is the distance between the centers of adjacent electrode fingers. In this specification, the same electrode finger pitch also includes a case where the electrode finger pitches are different within a tolerance range that does not significantly affect the electrical characteristics of the elastic wave device.

[0045] In this embodiment, Figure 1 The third electrode finger 28 of the second IDT electrode 27 is connected to the same potential as one of the first electrode finger 18 and the second electrode finger 19 of the first IDT electrode 7. The fourth electrode finger 29 is connected to the same potential as the other of the first electrode finger 18 and the second electrode finger 19.

[0046] In this embodiment, the potentials of the electrode fingers that overlap when viewed from above are in phase. However, the relationship between the potentials of the electrode fingers of the first IDT electrode 7 and the electrode fingers of the second IDT electrode 27 is not limited to the above. For example, the potentials of at least one pair of electrode fingers among the plurality of pairs of electrode fingers stacked in a plan view may be in phase.

[0047] The potential of the reflectors 15A, 15B, 25A, and 25B may be the same as that of the first electrode finger 18 of the first IDT electrode 7, or the same as that of the second electrode finger 19. Alternatively, each reflector may be a floating electrode. A floating electrode is an electrode that is not connected to a signal potential or a ground potential.

[0048] In the elastic wave device 1, silicon is used as the material of the support substrate 3. However, the material of the support substrate 3 is not limited to the above, and for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, dielectrics such as diamond and glass, semiconductors such as silicon and gallium nitride, or resins, or materials containing the above materials as main components can be used. In addition, in this specification, the so-called main component refers to a component that accounts for more than 50wt% in the component. The material of the above main component may exist in any state of single crystal, polycrystalline and amorphous, or in a state of mixed existence of them.

[0049] As the material of the first layer 4A of the intermediate layer 4, silicon nitride is used. However, the material of the first layer 4A is not limited to the above, and for example, aluminum nitride, lithium tantalate, lithium niobate, piezoelectrics such as quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, ceramics such as sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), diamond, or semiconductors such as silicon, or materials with the above materials as the main component can be used. In addition, the above spinel contains aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. As examples of the above spinel, MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4 can be listed.

[0050] Silicon oxide is used as the material of the second layer 4B of the intermediate layer 4. However, the material of the second layer 4B is not limited to the above, and for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds in which fluorine, carbon, or boron is added to silicon oxide, or materials containing the above materials as main components can be used.

[0051] In the above, the examples of the material of the first layer 4A of the intermediate layer 4 are different from the examples of the material of the second layer 4B. However, the materials listed as the examples of the material of the first layer 4A may be used for the second layer 4B. The materials listed as the examples of the material of the second layer 4B may be used for the first layer 4A. In addition, the number of layers of the intermediate layer 4 is not particularly limited, and may be 1 layer or 3 layers or more. In the case where the intermediate layer 4 has a plurality of layers, the materials of the plurality of layers may be different from each other.

[0052] Lithium niobate is used as the material of the piezoelectric layer 5. However, the material of the piezoelectric layer 5 is not limited to the above, and for example, lithium tantalate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate) may be used.

[0053] In this specification, the first IDT electrode 7 is buried in the intermediate layer 4, which means that the side surfaces 7c of the plurality of electrode fingers of the first IDT electrode 7 are in contact with the intermediate layer 4. For example, when the second surfaces 7b of the plurality of electrode fingers are in contact with a member other than the intermediate layer 4, the first IDT electrode 7 is also buried in the intermediate layer 4.

[0054] In this embodiment, the portion of the intermediate layer 4 where the first IDT electrode 7 is embedded is the second layer 4B. The material of the second layer 4B is different from that of the piezoelectric layer 5. Alternatively, the material of the portion of the intermediate layer 4 where the first IDT electrode 7 is embedded may be the same as that of the piezoelectric layer 5.

[0055] like Figure 1 As shown in the figure, the first IDT electrode 7 is directly provided on the first principal surface 5a of the piezoelectric layer 5. However, the first IDT electrode 7 may be provided indirectly on the first principal surface 5a via a dielectric film.

[0056] like Figure 3 As shown, each electrode finger of the second IDT electrode 27 includes a third surface 27a, a fourth surface 27b and a side surface 27c. The third surface 27a and the fourth surface 27b are opposite to each other in the thickness direction of each electrode finger. Of the third surface 27a and the fourth surface 27b, the third surface 27a is located on the piezoelectric layer 5 side. The side surface 27c is connected to the third surface 27a and the fourth surface 27b. In the present embodiment, the side surface 27c of each electrode finger is inclined relative to the thickness direction of each electrode finger. More specifically, the side surface 27c of each electrode finger is inclined so that the farther away from the piezoelectric layer 5, the narrower the width of each electrode finger becomes. In addition, the side surface 27c of each electrode finger may also extend parallel to the thickness direction of each electrode finger.

[0057] As described above, in the present invention, as long as the inclination angles of the first portion 7d and the second portion 7e are different from each other in at least one electrode finger of the first IDT electrode 7. However, it is preferred that the inclination angles of the first portion 7d and the second portion 7e are different from each other in a plurality of electrode fingers. It is more preferred that the inclination angles of the first portion 7d and the second portion 7e are different from each other in all electrode fingers. Accordingly, the bonding force between the first IDT electrode 7 and the intermediate layer 4 can be effectively improved. Therefore, the peeling between the first IDT electrode 7 and the intermediate layer 4 can be effectively suppressed.

[0058] In the first IDT electrode 7 of the present embodiment, the inclination angles of the first portion 7 d and the second portion 7 e of each electrode finger are not 0°. However, the inclination angle of one of the first portion 7 d and the second portion 7 e may be 0°.

[0059] In each electrode finger of the first IDT electrode 7, the inclination angle of the second portion 7e is larger than the inclination angle of the first portion 7d. Alternatively, the inclination angle of the second portion 7e may be smaller than the inclination angle of the first portion 7d.

[0060] The side surface 7c of each electrode finger of the first IDT electrode 7 in the elastic wave device 1 has a first portion 7d and a second portion 7e as a plurality of parts. The plurality of parts in the side surface 7c is not limited to two parts, and may be three or more parts. On the side surface 7c, three or more parts may be arranged in the thickness direction of the electrode finger, and the ends of adjacent parts may be connected to each other.

[0061] Figure 4 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in the elastic wave device according to the second embodiment.

[0062] The present embodiment is different from the first embodiment in that the side surface 37c of each electrode finger of the first IDT electrode 37 has a first portion 37d, a second portion 37e, and a third portion 37f as a plurality of portions. The first portion 37d, the second portion 37e, and the third portion 37f are arranged in sequence in the thickness direction of the electrode finger. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0063] The inclination angle of the second portion 37e in each electrode finger of the first IDT electrode 37 is the largest among the inclination angles of the multiple portions. The inclination angle of the first portion 37d is the smallest among the inclination angles of the multiple portions. Therefore, the inclination angle of the third portion 37f is greater than the inclination angle of the first portion 37d, and is smaller than the inclination angle of the second portion 37e. In this way, the side surface 37c of each electrode finger has multiple portions with different inclination angles. Accordingly, the bonding force between the first IDT electrode 37 and the intermediate layer 4 can be effectively improved. Therefore, the peeling between the first IDT electrode 37 and the intermediate layer 4 can be effectively suppressed.

[0064] In each electrode finger of the first IDT electrode 37, the magnitude relationship of the inclination angles of the plurality of portions of the side surface 37c is not limited to the above. For example, the inclination angle may be larger in the order of the first portion 37d, the second portion 37e, and the third portion 37f, or may be smaller in the order described above.

[0065] Figure 5 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a third embodiment.

[0066] The present embodiment is different from the first embodiment in that a dielectric film 46 is provided between the piezoelectric layer 5 and the first IDT electrode 7. More specifically, the dielectric film 46 is directly provided on the first principal surface 5a of the piezoelectric layer 5. Furthermore, the first IDT electrode 7 is indirectly provided on the first principal surface 5a of the piezoelectric layer 5 via the dielectric film 46. Figure 5 The dashed line in shows the boundary between the dielectric film 46 and the intermediate layer 4. Except for the above-described points, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0067] Silicon oxide is used as a material of the dielectric film 46. However, the material of the dielectric film 46 is not limited to the above, and for example, a dielectric such as silicon nitride may also be used.

[0068] The dielectric film 46 and the second layer 4B of the intermediate layer 4 are integrally formed of the same material. Alternatively, the dielectric film 46 and the second layer 4B of the intermediate layer 4 may include different materials.

[0069] In this embodiment, the fractional bandwidth and element capacitance of the elastic wave device can be easily adjusted by adjusting the thickness of the dielectric film 46. In addition, as in the first embodiment, the first IDT electrode 7 is embedded in the intermediate layer 4, and the first portion 7d and the second portion 7e of the side surface 7c of each electrode finger in the first IDT electrode 7 have different inclination angles. This can improve the bonding strength between the first IDT electrode 7 and the intermediate layer 4. Therefore, it is not easy to peel off between the first IDT electrode 7 and the intermediate layer 4.

[0070] Figure 6 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a fourth embodiment.

[0071] This embodiment differs from the first embodiment in the structure of the intermediate layer 54. This embodiment also differs from the first embodiment in the structure of the side surface 57c in each electrode finger of the first IDT electrode 57. Except for the above points, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0072] The intermediate layer 54 is a single layer and contains a piezoelectric material. More specifically, the material of the intermediate layer 54 is the same as the material of the piezoelectric body layer 5 . Figure 6The dashed line in shows the boundary between the intermediate layer 54 and the piezoelectric layer 5. The first principal surface 5a of the piezoelectric layer 5 is a surface through which the first surfaces 57a of the plurality of electrode fingers in the first IDT electrode 57 pass.

[0073] The piezoelectric layer 5 and the intermediate layer 54 are made of the same material and are integrally formed. Therefore, in the elastic wave device of this embodiment, the first IDT electrode 57 is embedded in the piezoelectric layer. Figure 6 The piezoelectric layer 5 and the intermediate layer 54 shown in the figure are formed as an integrated piezoelectric layer.

[0074] The side surface 57c of each electrode finger of the first IDT electrode 57 is inclined so that the width of the electrode finger becomes wider as it moves away from the piezoelectric layer 5. On the side surface 57c, the inclination angles of the first portion 57d and the second portion 57e are negative values. The inclination angle of the second portion 57e is greater than the inclination angle of the first portion 57d. In addition, the absolute value of the inclination angle of the second portion 57e is smaller than the absolute value of the inclination angle of the first portion 57d.

[0075] In this embodiment, as in the first embodiment, the first IDT electrode 57 is embedded in the intermediate layer 54, and the first portion 57d and the second portion 57e of the side surface 57c of each electrode finger in the first IDT electrode 57 have different inclination angles. This can improve the bonding strength between the first IDT electrode 57 and the intermediate layer 54. Therefore, it is difficult for the first IDT electrode 57 and the intermediate layer 54 to peel off.

[0076] In addition, if Figure 6 As shown, the second surface 57b of the plurality of electrode fingers in the first IDT electrode 57 is in contact with the support substrate 3. When manufacturing the elastic wave device of this embodiment, for example, the first IDT electrode 57 may be formed on the support substrate 3. Thereafter, a piezoelectric layer may be formed on the support substrate 3 so as to cover the first IDT electrode 57. For example, the piezoelectric layer may be formed by sputtering or the like. In addition, the piezoelectric layer is Figure 6 The intermediate layer 54 and the piezoelectric layer 5 shown in the figure are formed into an integrated piezoelectric layer. However, the method of forming the first IDT electrode 57 and the piezoelectric layer is not limited to the above. For example, after forming the piezoelectric layer, a groove portion may be provided in the piezoelectric layer. The first IDT electrode 57 may also be formed in the groove portion.

[0077] In addition, the second surfaces 57b of the plurality of electrode fingers in the first IDT electrode 57 do not necessarily need to be in contact with the support substrate 3. Figure 7In the variation of the fourth embodiment shown, the intermediate layer 64 has a plurality of layers. More specifically, the intermediate layer 64 has a first layer 64A and a second layer 64B. The first IDT electrode 57 is not buried in the first layer 64A. The second layer 64B is a portion of the intermediate layer 64 in which the first IDT electrode 57 is buried. Moreover, the material of the second layer 64B is the same as the material of the piezoelectric layer 5. On the other hand, the material of the first layer 64A is different from the material of the piezoelectric layer 5. The second surface 57b of each electrode finger of the first IDT electrode 57 is in contact with the first layer 64A.

[0078] In this modification, the second layer 64B of the intermediate layer 64 and the piezoelectric layer 5 are integrally formed. The integrally formed piezoelectric layer is indirectly provided on the support substrate 3 via the first layer 64A of the intermediate layer 64. In this modification, similarly to the fourth embodiment, peeling is not likely to occur between the first IDT electrode 57 and the intermediate layer 64.

[0079] Figure 8 FIG. 1 is a schematic top view of an elastic wave device according to a fifth embodiment. Figure 8 In the example, the reflector is omitted. Figure 8 This is a schematic top view, so it is relatively Figure 2 , Figure 8 Not only are the front and back sides opposite, but the configuration is also upside down.

[0080] The present embodiment differs from the first embodiment in that a first wiring 72 and a second wiring 73 are provided. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment. In the present embodiment, the plurality of fourth electrode fingers 29 of the second IDT electrode 27 are connected to a potential that is opposite in phase to the plurality of first electrode fingers 18 of the first IDT electrode 7.

[0081] The first wiring 72 is provided on the first main surface 5a of the piezoelectric layer 5. The first wiring 72 is connected to the first bus bar 16 of the first IDT electrode 7. The first wiring 72 is electrically connected to the plurality of first electrode fingers 18 via the first bus bar 16. In the present embodiment, the first wiring 72 and the first bus bar 16 are integrally formed of the same material. However, the first wiring 72 and the first bus bar 16 may also be formed of different materials.

[0082] The second wiring 73 is provided on the second main surface 5b of the piezoelectric layer 5. The second wiring 73 is connected to the fourth bus bar 77 of the second IDT electrode 27. The second wiring 73 is electrically connected to the plurality of fourth electrode fingers 29 via the fourth bus bar 77. In the present embodiment, the second wiring 73 and the fourth bus bar 77 are integrally formed of the same material. However, the second wiring 73 and the fourth bus bar 77 may also be formed of different materials.

[0083] In the present embodiment, the plurality of first electrode fingers 18 and the plurality of fourth electrode fingers 29 are connected to potentials in opposite phases to each other. Therefore, for example, when the first wiring 72, the first bus bar 16, and the plurality of first electrode fingers 18 are at a -potential, the second wiring 73, the fourth bus bar 77, and the plurality of fourth electrode fingers 29 are at a +potential.

[0084] like Figure 8 As shown, a portion of the first wiring 72 and a portion of the second wiring 73 overlap in a plan view. In this way, an overlapping region D is formed. More specifically, in the overlapping region D, the first wiring 72 and the second wiring 73 are opposed to each other via the piezoelectric layer 5. Accordingly, the element capacitance can be increased. This effect is shown below by comparing this embodiment with the first embodiment.

[0085] Fig. 9 It is a graph showing the impedance frequency characteristics in the first embodiment and the fifth embodiment.

[0086] In by Fig. 9 In the frequency domain on the low-frequency side shown by the arrow E in FIG, the larger the element capacitance, the lower the impedance. In the frequency domain shown by the arrow E, the impedance in the fifth embodiment is lower than the impedance in the first embodiment. Therefore, it can be seen that the element capacitance can be increased in the fifth embodiment. Therefore, in the fifth embodiment, the area of ​​the first IDT electrode 7 and the second IDT electrode 27 for obtaining the desired element capacitance can be reduced. Therefore, in the fifth embodiment, the miniaturization of the elastic wave device can be promoted.

[0087] Here, when the resonant frequency is fr and the antiresonant frequency is fa, the value represented by (|fa-fr| / fr)×100[%] is the fractional bandwidth of the elastic wave device. Fig. 9 As shown in FIG. 1 , the difference between the resonant frequency fr and the anti-resonant frequency fa is different between the fifth embodiment and the first embodiment. Therefore, the fractional bandwidth is different between the fifth embodiment and the first embodiment. This is because the fractional bandwidth depends on the element capacitance. In addition, in the fifth embodiment, by adjusting the area of ​​the overlapping region D, the element capacitance can be easily adjusted. Accordingly, the fractional bandwidth can be easily adjusted.

[0088] In the fifth embodiment, as in the first embodiment, the first IDT electrode 7 is embedded in the intermediate layer, and the first and second portions of the side surfaces of the electrode fingers in the first IDT electrode 7 have different inclination angles. This can improve the bonding strength between the first IDT electrode 7 and the intermediate layer. Therefore, peeling is less likely to occur between the first IDT electrode 7 and the intermediate layer.

[0089] In addition, Figure 8 , the configuration of the first wiring 72 and the second wiring 73 is schematically shown, and the reflector is omitted. For example, the overlapping region D may be located outside the reflector in the elastic wave propagation direction. In other words, for example, the reflector may be located between the overlapping region D and the first IDT electrode 7.

[0090] In the fifth embodiment, one first wiring 72 and one second wiring 73 are provided. However, two first wirings 72 and two second wirings 73 may be provided.

[0091] Fig.10 It is a schematic plan view of an elastic wave device according to a sixth embodiment.

[0092] The difference between this embodiment and the fifth embodiment is that two first wirings and two second wirings are provided. Specifically, the two first wirings are the first wiring 82A and the first wiring 82B. Specifically, the two second wirings are the second wiring 83A and the second wiring 83B. The difference between this embodiment and the fifth embodiment is that the first wiring 82A and the first wiring 82B and the second wiring 83A and the second wiring 83B are reflectors, respectively. Except for the above aspects, the elastic wave device of this embodiment has the same structure as the elastic wave device of the fifth embodiment.

[0093] As in the fifth embodiment, the first wiring 82A and the first wiring 82B are provided on the first principal surface 5a of the piezoelectric layer 5. The first wiring 82A includes a reflector portion 82c and a wiring portion 82d. The reflector portion 82c is a portion that functions as a reflector. The wiring portion 82d is connected to the reflector portion 82c. The wiring portion 82d is connected to the first bus bar 16 of the first IDT electrode 7. The first wiring 82B also includes a reflector portion 82e and a wiring portion 82f. The wiring portion 82f connects the reflector portion 82e and the first bus bar 16. The reflector portion 82c and the reflector portion 82e are opposed to each other with the first IDT electrode 7 sandwiched therebetween.

[0094] The second wiring 83A and the second wiring 83B are provided on the second main surface 5b of the piezoelectric layer 5. The second wiring 83A includes a reflector portion 83c and a wiring portion 83d. The wiring portion 83d connects the reflector portion 83c and the fourth bus bar 77. The second wiring 83B also includes a reflector portion 83e and a wiring portion 83f. The wiring portion 83f connects the reflector portion 83e and the fourth bus bar 77. The reflector portion 83c and the reflector portion 83e are opposed to each other with the second IDT electrode 27 interposed therebetween.

[0095] In the present embodiment, the plurality of first electrode fingers 18 and the plurality of fourth electrode fingers 29 are connected to potentials in opposite phases to each other. Therefore, for example, when the first wiring 82A, the first wiring 82B, the first bus bar 16, and the plurality of first electrode fingers 18 are at a -potential, the second wiring 83A, the second wiring 83B, the fourth bus bar 77, and the plurality of fourth electrode fingers 29 are at a +potential.

[0096] The reflector portion 82c of the first wiring 82A and the reflector portion 83c of the second wiring 83A overlap in a plan view. More specifically, the reflector portion 82c and the reflector portion 83c face each other with the piezoelectric layer 5 sandwiched therebetween. Similarly, the reflector portion 82e of the first wiring 82B and the reflector portion 83e of the second wiring 83B overlap in a plan view. More specifically, the reflector portion 82e and the reflector portion 83e face each other with the piezoelectric layer 5 sandwiched therebetween. Accordingly, the element capacitance can be increased.

[0097] In addition, in this embodiment, as in the first embodiment and the fifth embodiment, the first IDT electrode 7 is buried in the intermediate layer, and the first portion and the second portion of the side surface of each electrode finger in the first IDT electrode 7 have different inclination angles. This can improve the bonding strength between the first IDT electrode 7 and the intermediate layer. Therefore, it is difficult for peeling to occur between the first IDT electrode 7 and the intermediate layer.

[0098] In this embodiment, both the first wiring 82A and the second wiring 83A are reflectors. Both the first wiring 82B and the second wiring 83B are reflectors. However, at least one of the first wiring 82A and the second wiring 83A may be a reflector. Similarly, at least one of the first wiring 82B and the second wiring 83B may be a reflector.

[0099] In the present disclosure, the elastic wave device may include a protective film such as a silicon oxide film or a silicon nitride film that covers the second IDT electrode.

[0100] Fig.11 1 is a front cross-sectional view showing the vicinity of two pairs of electrode fingers of a first IDT electrode and a second IDT electrode in an elastic wave device according to a seventh embodiment.

[0101] The present embodiment differs from the first embodiment in that the thickness of the second layer 94B in the intermediate layer 94 is thinner than the thickness of each electrode finger of the first IDT electrode 7. The present embodiment also differs from the first embodiment in that a portion of the first layer 94A in the intermediate layer 94 is located between the electrode fingers of the first IDT electrode 7. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0102] In the present embodiment, the portion of the intermediate layer 94 in which the first IDT electrode 7 is embedded is the portion of the intermediate layer 94 that covers the first IDT electrode 7. That is, in the present embodiment, the first IDT electrode 7 is embedded in the second layer 94B of the intermediate layer 94. Moreover, as in the first embodiment, the first portion 7d and the second portion 7e of the side surface 7c of each electrode finger in the first IDT electrode 7 have different inclination angles. Accordingly, the bonding force between the first IDT electrode 7 and the intermediate layer 94 can be improved. Therefore, it is not easy to peel off between the first IDT electrode 7 and the intermediate layer 94.

[0103] Alternatively, the support substrate 3 may be opposed to the first IDT electrode 7 embedded in the intermediate layer 94 via the cavity. Fig.12 In the modification of the seventh embodiment shown, the first layer 104A of the intermediate layer 104 has a frame shape. On the other hand, the second layer 104B of the intermediate layer 104 covers the first IDT electrode 7 as in the seventh embodiment. That is, the first IDT electrode 7 is buried in the second layer 104B of the intermediate layer 104.

[0104] A cavity portion surrounded by the first layer 104A, the second layer 104B and the support substrate 3 in the intermediate layer 104 is formed. Therefore, the piezoelectric substrate 102 has a cavity portion. The support substrate 3 is opposite to the first IDT electrode 7 embedded in the second layer 104B of the intermediate layer 104 via the cavity portion. In this modified example, as in the seventh embodiment, peeling is not likely to occur between the first IDT electrode 7 and the second layer 104B in the intermediate layer 104.

[0105] In this modification, the materials of the first layer 104A and the second layer 104B in the intermediate layer 104 are different from each other. However, even when the first layer 104A has a frame shape, the materials of the first layer 104A and the second layer 104B may be the same.

[0106] In the structure of the present invention other than this modification, it is also possible to adopt a structure in which the second layer of the intermediate layer has a frame-like shape and the piezoelectric substrate has a cavity. For example, Figure 1 The first layer 4A of the intermediate layer 4 in the first embodiment shown may also have a frame-like shape. Alternatively, Figure 7 The first layer 64A of the intermediate layer 64 in the modified example of the fourth embodiment shown may also have a frame shape. In these cases, separation is unlikely to occur between the first IDT electrode and the second layer in the intermediate layer.

[0107] Examples of aspects of the elastic wave device according to the present invention are summarized below.

[0108] <1> An elastic wave device comprises: a supporting substrate; an intermediate layer arranged on the supporting substrate; a piezoelectric layer arranged on the intermediate layer and having a first principal surface located on the intermediate layer side and a second principal surface opposite to the first principal surface; a first IDT electrode arranged on the first principal surface of the piezoelectric layer and buried in the intermediate layer; and a second IDT electrode arranged on the second principal surface of the piezoelectric layer, the first IDT electrode having a plurality of electrode fingers, each of the electrode fingers respectively including a first surface and a second surface opposite to each other in the thickness direction of the electrode finger, and a side surface connected to the first surface and the second surface, the side surface of the electrode finger in the first IDT electrode having a first portion and a second portion, and in at least one of the electrode fingers, the first portion and the second portion are inclined at different angles relative to the thickness direction of the electrode finger.

[0109] <2> exist <1> In the elastic wave device described above, on the side surfaces of all the electrode fingers in the first IDT electrode, the first portion and the second portion have different inclination angles with respect to the thickness direction of the electrode fingers.

[0110] <3> exist <1> or <2> In the elastic wave device described above, a material of a portion of the intermediate layer in which the first IDT electrode is embedded is different from a material of the piezoelectric layer.

[0111] <4> exist <3> In the elastic wave device described above, the first IDT electrode is provided directly on the first principal surface of the piezoelectric layer.

[0112] <5> exist <3> In the elastic wave device described above, the elastic wave device further includes a dielectric film directly provided on the first main surface of the piezoelectric layer, and the first IDT electrode is indirectly provided on the first main surface of the piezoelectric layer via the dielectric film.

[0113] <6> exist <1> or <2> In the elastic wave device described above, a portion of the intermediate layer in which the first IDT electrode is embedded is made of the same material as that of the piezoelectric layer.

[0114] <7> exist <1> to <6> In the elastic wave device described in any one of the above, the intermediate layer includes a plurality of layers made of different materials.

[0115] <8> exist <1> to <7> In the elastic wave device described in any one of the items, the multiple electrode fingers of the first IDT electrode include a multiple first electrode fingers and a multiple second electrode fingers connected to different potentials, the second IDT electrode includes a multiple third electrode fingers and a multiple fourth electrode fingers connected to different potentials, the multiple fourth electrode fingers are connected to a potential that is opposite to the potential of the multiple first electrode fingers, and the elastic wave device also includes: a first wiring electrically connected to the multiple first electrode fingers of the first IDT electrode; and a second wiring electrically connected to the multiple fourth electrode fingers of the second IDT electrode, and a portion of the first wiring and a portion of the second wiring overlap when viewed from above.

[0116] <9> exist <8> In the elastic wave device described above, at least one of the first wiring and the second wiring is a reflector.

[0117] Description of Reference Numerals

[0118] 1…Elastic wave device

[0119] 2…Piezoelectric substrate

[0120] 3…Support base plate

[0121] 4…Middle Layer

[0122] 4A, 4B…1st floor, 2nd floor

[0123] 5…Piezoelectric layer

[0124] 5a, 5b... first main surface, second main surface

[0125] 7…First IDT electrode

[0126] 7a, 7b…side 1, side 2

[0127] 7c…side

[0128] 7d, 7e…Part 1, Part 2

[0129] 15A, 15B…Reflector

[0130] 16, 17…First bus bar, second bus bar

[0131] 18, 19…first electrode finger, second electrode finger

[0132] 25A, 25B…Reflector

[0133] 27…Second IDT electrode

[0134] 27a, 27b…side 3, side 4

[0135] 27c…side

[0136] 28, 29…third electrode finger, fourth electrode finger

[0137] 37…First IDT electrode

[0138] 37c…side

[0139] 37d~37f…Part 1~Part 3

[0140] 46…Dielectric film

[0141] 54…Middle layer

[0142] 57…First IDT electrode

[0143] 57a, 57b…first side, second side

[0144] 57c…side

[0145] 57d, 57e…Part 1, Part 2

[0146] 64…Middle layer

[0147] 64A, 64B…1st floor, 2nd floor

[0148] 72, 73 ... first wiring, second wiring

[0149] 77…Bus 4

[0150] 82A, 82B…first wiring

[0151] 82c…Reflector

[0152] 82d…Wiring Department

[0153] 82e…Reflector

[0154] 82f…Wiring Department

[0155] 83A, 83B...second wiring

[0156] 83c…Reflector

[0157] 83d…Wiring Department

[0158] 83e…Reflector

[0159] 83f…Wiring department

[0160] 94…Middle layer

[0161] 94A, 94B…1st floor, 2nd floor

[0162] 102…Piezoelectric substrate

[0163] 104…Middle Layer

[0164] 104A, 104B…1st floor, 2nd floor

[0165] C…Crossover area

[0166] D…Overlapping area.

Claims

1. An elastic wave device comprising: Support base plate: An intermediate layer is disposed on the supporting substrate; a piezoelectric layer provided on the intermediate layer and having a first principal surface located on the intermediate layer side and a second principal surface opposite to the first principal surface; a first IDT electrode provided on the first main surface of the piezoelectric layer and buried in the intermediate layer; and A second IDT electrode is provided on the second main surface of the piezoelectric layer. The first IDT electrode has a plurality of electrode fingers, each of which includes a first surface and a second surface facing each other in a thickness direction of the electrode finger, and a side surface connected to the first surface and the second surface. The side surface of the electrode finger in the first IDT electrode includes a first portion and a second portion, and in at least one of the electrode fingers, the first portion and the second portion are inclined at different angles with respect to a thickness direction of the electrode finger.

2. The elastic wave device according to claim 1, wherein: In the side surfaces of all the electrode fingers in the first IDT electrode, the first portion and the second portion have different inclination angles with respect to the thickness direction of the electrode fingers.

3. The elastic wave device according to claim 1 or 2, wherein: The material of a portion of the intermediate layer in which the first IDT electrode is buried is different from the material of the piezoelectric layer.

4. The elastic wave device according to claim 3, wherein: The first IDT electrode is directly provided on the first main surface of the piezoelectric layer.

5. The elastic wave device according to claim 3, wherein: The elastic wave device further includes a dielectric film provided directly on the first main surface of the piezoelectric layer. The first IDT electrode is indirectly provided on the first main surface of the piezoelectric layer via the dielectric film.

6. The elastic wave device according to claim 1 or 2, wherein: The material of the portion of the intermediate layer in which the first IDT electrode is buried is the same as the material of the piezoelectric layer.

7. The elastic wave device according to any one of claims 1 to 6, wherein: The intermediate layer includes a plurality of layers whose materials are different from each other.

8. The elastic wave device according to any one of claims 1 to 7, wherein: The plurality of electrode fingers of the first IDT electrode include a plurality of first electrode fingers and a plurality of second electrode fingers connected to different potentials from each other. The second IDT electrode includes a plurality of third electrode fingers and a plurality of fourth electrode fingers connected to different potentials from each other, the plurality of fourth electrode fingers being connected to a potential inverse to that of the plurality of first electrode fingers. The elastic wave device further comprises: a first wiring electrically connected to the plurality of first electrode fingers of the first IDT electrode; and a second wiring electrically connected to the plurality of fourth electrode fingers of the second IDT electrode, A portion of the first wiring and a portion of the second wiring overlap in a plan view.

9. The elastic wave device according to claim 8, wherein: At least one of the first wiring and the second wiring is a reflector.

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