WO2023140272A1 - Elastic wave device - Google Patents

Elastic wave device Download PDF

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Publication number
WO2023140272A1
WO2023140272A1 PCT/JP2023/001277 JP2023001277W WO2023140272A1 WO 2023140272 A1 WO2023140272 A1 WO 2023140272A1 JP 2023001277 W JP2023001277 W JP 2023001277W WO 2023140272 A1 WO2023140272 A1 WO 2023140272A1
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electrode
wave device
elastic wave
piezoelectric layer
electrodes
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PCT/JP2023/001277
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French (fr)
Japanese (ja)
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和則 井上
昌和 三村
明洋 井山
宗久 渡辺
年麿 米田
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株式会社村田製作所
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Publication of WO2023140272A1 publication Critical patent/WO2023140272A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/25—Constructional features of resonators using surface acoustic waves

Definitions

  • the present disclosure relates to an acoustic wave device including a piezoelectric layer (piezoelectric layer).
  • Patent Document 1 discloses an elastic wave device that uses plate waves.
  • An acoustic wave device described in Patent Document 1 includes a support, a piezoelectric substrate, and an IDT electrode.
  • the support is provided with a cavity.
  • a piezoelectric substrate is provided on the support so as to overlap the cavity.
  • the IDT electrode is provided on the piezoelectric substrate so as to overlap the cavity.
  • plate waves are excited by IDT electrodes.
  • the edge of the cavity does not include a straight portion extending parallel to the propagation direction of the Lamb waves excited by the IDT electrodes.
  • An object of the present disclosure is to provide an elastic wave device capable of suppressing the occurrence of cracks in the membrane portion.
  • An elastic wave device includes: a support substrate; a piezoelectric layer provided on the support substrate; a functional electrode provided on the piezoelectric layer; a hollow portion provided inside the support substrate and overlapping with a part of the functional electrode in a plan view along the stacking direction of the support substrate and the piezoelectric layer; and at least one protrusion extending in a direction intersecting the stacking direction from a portion of the supporting substrate forming the inner surface of the hollow portion and supporting the piezoelectric layer in the stacking direction.
  • an elastic wave device capable of suppressing the occurrence of cracks in the membrane portion.
  • FIG. 1 is a schematic perspective view showing the appearance of elastic wave devices of first and second aspects
  • FIG. FIG. 4 is a plan view showing an electrode structure on the piezoelectric layer; Sectional drawing of the part which follows the AA line in FIG. 1A.
  • FIG. 2 is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of a conventional elastic wave device.
  • FIG. 2 is a schematic front cross-sectional view for explaining waves of the elastic wave device of the present disclosure;
  • FIG. 4 is a schematic diagram showing a bulk wave when a voltage is applied between the first electrode and the second electrode so that the potential of the second electrode is higher than that of the first electrode.
  • FIG. 4 is a diagram showing resonance characteristics of the elastic wave device according to the first embodiment of the present disclosure;
  • FIG. 4 is a diagram showing the relationship between d/2p and the fractional bandwidth as a resonator of an acoustic wave device; The top view of another elastic wave device concerning a 1st embodiment of this indication.
  • FIG. 2 is a reference diagram showing an example of resonance characteristics of an elastic wave device;
  • FIG. 4 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; 4 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth;
  • FIG. 4 is a diagram showing a map of the fractional bandwidth with respect to the Euler angles (0°, ⁇ , ⁇ ) of LiNbO 3 when d/p is infinitely close to 0; 1 is a partially cutaway perspective view for explaining an elastic wave device according to a first embodiment of the present disclosure;
  • FIG. The top view which shows an example of the elastic wave apparatus of 2nd Embodiment of this indication. Sectional drawing along the XIV-XIV line of FIG. Sectional drawing along the XV-XV line of FIG. The top view which shows the 1st modification of the elastic wave apparatus of FIG.
  • the top view which shows the 2nd modification of the elastic wave apparatus of FIG.
  • the top view of the elastic wave device which is not provided with the protrusion.
  • FIG. 19 is a second cross-sectional view for explaining a state in which the membrane portion of the elastic wave device of FIG. 18 is deformed;
  • the elastic wave devices of the first, second, and third aspects of the present disclosure include, for example, a piezoelectric layer made of lithium niobate or lithium tantalate, and a first electrode and a second electrode that face each other in a direction intersecting the thickness direction of the piezoelectric layer.
  • the first electrode and the second electrode are adjacent electrodes, and d/p is 0.5 or less, where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the first electrode and the second electrode.
  • Lamb waves are used as plate waves. Then, resonance characteristics due to the Lamb wave can be obtained.
  • An elastic wave device includes a piezoelectric layer made of lithium niobate or lithium tantalate, and an upper electrode and a lower electrode facing each other in the thickness direction of the piezoelectric layer with the piezoelectric layer interposed therebetween, and utilizes bulk waves.
  • FIG. 1A is a schematic perspective view showing the appearance of the elastic wave device according to the first embodiment with respect to the first and second aspects
  • FIG. 1B is a plan view showing the electrode structure on the piezoelectric layer
  • FIG. 2 is a cross-sectional view along line AA in FIG. 1A.
  • the acoustic wave device 1 has a piezoelectric layer 2 made of LiNbO 3 .
  • the piezoelectric layer 2 may consist of LiTaO 3 .
  • the cut angle of LiNbO 3 and LiTaO 3 is Z-cut in this embodiment, but may be rotational Y-cut or X-cut.
  • the Y-propagation and X-propagation ⁇ 30° propagation orientations are preferred.
  • the thickness of the piezoelectric layer 2 is not particularly limited, it is preferably 50 nm or more and 1000 nm or less in order to effectively excite the thickness-shear primary mode.
  • the piezoelectric layer 2 has first and second main surfaces 2a and 2b facing each other. Electrodes 3 and 4 are provided on the first main surface 2a.
  • the electrode 3 is an example of the "first electrode” and the electrode 4 is an example of the "second electrode”.
  • the multiple electrodes 3 are multiple first electrode fingers connected to a first busbar 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 a length direction.
  • the electrode 3 and the adjacent electrode 4 face each other in a direction perpendicular to the length direction.
  • These electrodes 3 and 4, the first bus bar 5 and the second bus bar 6 constitute an IDT (Interdigital Transducer) electrode.
  • IDT Interdigital Transducer
  • 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 intersecting the thickness direction of the piezoelectric layer 2 .
  • the length direction of the electrodes 3 and 4 may be interchanged with the direction orthogonal to the length direction of the electrodes 3 and 4 shown in FIGS. 1A and 1B. That is, in FIGS. 1A and 1B, the electrodes 3 and 4 may extend in the direction in which the first 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. 1A and 1B.
  • a plurality of pairs of adjacent electrodes 3 connected to one potential and electrodes 4 connected to the other potential are provided in a direction perpendicular to the length direction of the electrodes 3 and 4 .
  • the electrodes 3 and 4 are adjacent to each other, not when the electrodes 3 and 4 are arranged so as to be in direct contact, but when the electrodes 3 and 4 are arranged with a gap therebetween.
  • the electrode 3 and the electrode 4 are adjacent to each other, no electrode connected to the hot electrode or the ground electrode, including the other electrodes 3 and 4, is arranged between the electrode 3 and the electrode 4.
  • 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 ⁇ m or more and 10 ⁇ m or less. Further, the center-to-center distance between the electrodes 3 and 4 is the distance connecting the center of the width dimension of the electrode 3 in the direction perpendicular to the length direction of the electrode 3 and the center of the width dimension of the electrode 4 in the direction perpendicular to the length direction of the electrode 4.
  • the center-to-center distance between the electrodes 3 and 4 refers to the average value of the center-to-center distances of the adjacent electrodes 3 and 4 among the 1.5 or more pairs of electrodes 3 and 4.
  • the width of the electrodes 3 and 4, that is, the dimension in the facing direction of the electrodes 3 and 4 is preferably in the range of 150 nm or more and 1000 nm or less.
  • the center-to-center distance between the electrodes 3 and 4 is the distance between the center of the dimension (width dimension) of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the center of the dimension (width dimension) of the electrode 4 in the direction orthogonal to the length direction of the electrode 4.
  • 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 .
  • “perpendicular” is not limited to being strictly perpendicular, but may be substantially perpendicular (the angle between the direction perpendicular to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, 90° ⁇ 10°).
  • 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. 2, have openings 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). Preferably, high-resistance Si having a resistivity of 4 k ⁇ or more is desirable. However, the supporting member 8 can also be constructed using an appropriate insulating material or semiconductor material.
  • Examples of materials for the support member 8 include piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and quartz crystal; various ceramics such as alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectrics such as diamond and glass; and semiconductors such as gallium nitride.
  • piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and quartz crystal
  • various ceramics such as alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite
  • dielectrics such as diamond and glass
  • semiconductors such as gallium nitride.
  • 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.
  • 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.
  • 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 a thickness-shear primary mode bulk wave excited in the piezoelectric layer 2 .
  • d/p is 0.5 or less, 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.
  • d/p is 0.24 or less, in which case even better resonance characteristics can be obtained.
  • the center-to-center distance p between the adjacent electrodes 3 and 4 is the average distance between the centers of the adjacent electrodes 3 and 4.
  • the elastic wave device 1 of the present embodiment has the above configuration, even if the logarithm of the electrodes 3 and 4 is reduced in order to reduce the size, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides, and the propagation loss is small. The reason why the above reflector is not required is that the bulk wave of the thickness-shlip primary mode is used.
  • FIG. 3A is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of a conventional elastic wave device.
  • a conventional elastic wave device is described, for example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2012-257019).
  • FIG. 3A in the conventional acoustic wave device, waves propagate through the piezoelectric film 201 as indicated by arrows.
  • 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.
  • the X direction is the direction in which the electrode fingers of the IDT electrodes are arranged. As shown in FIG.
  • the 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.
  • the wave propagates and resonates substantially in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, in the Z direction. 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, no reflector is required. Therefore, no propagation loss occurs when propagating to the reflector. Therefore, 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.
  • the amplitude direction of the bulk wave of the thickness shear primary 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. FIG. 4 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.
  • the elastic wave device 1 at least one pair of electrodes consisting of the electrodes 3 and 4 is arranged, but since the waves are not propagated in the X direction, the number of electrode pairs consisting of the electrodes 3 and 4 does not necessarily need to be plural. That is, it is sufficient that at least one pair of electrodes is provided.
  • the electrode 3 is an electrode connected to a hot potential
  • the electrode 4 is an electrode connected to a ground potential.
  • electrode 3 may also be connected to ground potential and electrode 4 to hot potential.
  • 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. 5 is a diagram showing resonance characteristics of the acoustic wave device according to the first embodiment of the present disclosure.
  • the design parameters of the elastic wave device 1 with this resonance characteristic are as follows.
  • the number of pairs of electrodes consisting of the electrodes 3 and 4 21 pairs
  • the center distance between the electrodes 3 ⁇ m
  • the width of the electrodes 3 and 4 500 nm
  • d/p 0.133.
  • Insulating layer 7 Silicon oxide film with a thickness of 1 ⁇ m.
  • 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.
  • 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.
  • d/p is 0.5 or less, more preferably 0.24 or less. This will be explained with reference to FIG.
  • FIG. 6 is a diagram showing the relationship between this d/2p and the fractional bandwidth of the acoustic wave device as a resonator.
  • At least one pair of electrodes may be one pair, and p is the center-to-center distance between adjacent electrodes 3 and 4 in the case of one pair of electrodes. In the case of 1.5 pairs or more of electrodes, the average distance between the centers of adjacent electrodes 3 and 4 should be p.
  • the thickness d of the piezoelectric layer if the piezoelectric layer 2 has variations in thickness, a value obtained by averaging the thickness may be adopted.
  • FIG. 7 is a plan view of another elastic wave device according to the first embodiment of the present disclosure.
  • elastic wave device 31 a pair of electrodes having electrode 3 and electrode 4 is provided on first main surface 2 a of piezoelectric layer 2 .
  • K in FIG. 7 is the intersection width.
  • the number of pairs of electrodes may be one. Even in this case, if the above d/p is 0.5 or less, it is possible to effectively excite the bulk wave in the primary mode of thickness shear.
  • the metallization ratio MR of the adjacent electrodes 3 and 4 with respect to the excitation region which is the overlapping region when viewed in the direction in which one of the adjacent electrodes 3 and 4 faces each other, satisfies MR ⁇ 1.75 (d/p)+0.075.
  • the region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap is the excitation region (intersection region), and when the metallization ratio of the plurality of first electrode fingers and the plurality of second electrode fingers to the excitation region is MR, it is preferable to satisfy MR ⁇ 1.75 (d/p)+0.075. In that case, spurious can be effectively reduced.
  • FIG. 8 is a reference diagram showing an example of resonance characteristics of the acoustic wave device 1.
  • a spurious signal indicated by an arrow B appears between the resonance frequency and the anti-resonance frequency.
  • d/p 0.08 and the Euler angles of LiNbO 3 (0°, 0°, 90°).
  • the metallization ratio MR was set to 0.35.
  • the metallization ratio MR will be explained with reference to FIG. 1B.
  • the portion surrounded by the dashed-dotted line C is the excitation region.
  • the excitation regions are regions in which the electrodes 3 and 4 overlap, regions in which the electrodes 4 overlap the electrodes 3, and regions between the electrodes 3 and 4 in which the electrodes 3 and 4 overlap.
  • the area of the electrodes 3 and 4 in the excitation region C with respect to the area of this excitation region 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.
  • MR may be the ratio of the metallization portion included in the entire excitation region to the total area of the excitation region.
  • FIG. 9 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 elastic wave resonators are configured according to this embodiment.
  • the ratio band was adjusted by changing the film thickness of the piezoelectric layer and the dimensions of the electrodes.
  • FIG. 9 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.
  • the spurious is as large as 1.0.
  • the fractional band exceeds 0.17, that is, exceeds 17%, a large spurious with a spurious level of 1 or more appears in the passband even if the parameters constituting the fractional band are changed. That is, as in the resonance characteristics shown in FIG. 8, 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. 10 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth.
  • 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. 10 is the area where the fractional bandwidth is 17% or less.
  • FIG. 11 is a diagram showing a map of the fractional bandwidth with respect to the Euler angles (0°, ⁇ , ⁇ ) of LiNbO 3 when d/p is infinitely close to 0.
  • the hatched portion in FIG. 11 is a region where a fractional bandwidth of at least 5% or more is obtained, and the range of the region is approximated by the following formulas (1), (2), and (3).
  • the fractional band can be sufficiently widened, which is preferable.
  • FIG. 12 is a partially cutaway perspective view for explaining an elastic wave device according to a modification of the first embodiment of the present disclosure.
  • the elastic wave device 81 has a support substrate 82 .
  • the support substrate 82 is provided with a concave portion that is open on the upper surface.
  • a piezoelectric layer 83 is laminated on the support substrate 82 .
  • a hollow portion 9 is thereby formed.
  • An IDT electrode 84 is provided on the piezoelectric layer 83 above the cavity 9 .
  • Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction.
  • the outer periphery of the hollow portion 9 is indicated by broken lines.
  • the IDT electrode 84 has first and second bus bars 84a and 84b, an electrode 84c as a plurality of first electrode fingers and an electrode 84d as a plurality of second electrode fingers.
  • the multiple electrodes 84c are connected to the first bus bar 84a.
  • the multiple electrodes 84d are connected to the second bus bar 84b.
  • the multiple electrodes 84c and the multiple electrodes 84d are interposed.
  • a Lamb wave as a plate wave is excited by applying an AC electric field to the IDT electrodes 84 on the cavity 9. Since the reflectors 85 and 86 are provided on both sides, the resonance characteristics due to the Lamb wave can be obtained.
  • the elastic wave device of the present disclosure may utilize plate waves.
  • the elastic wave device 1 includes a support substrate 110, a piezoelectric layer 2 provided on the support substrate 110, and a functional electrode 120 provided on the piezoelectric layer 2.
  • a hollow portion 9 and at least one protrusion 140 are provided inside the support substrate 110 .
  • the hollow portion 9 is provided at a position overlapping with a portion of the functional electrode 120 in plan view along the stacking direction (for example, Z direction) of the support substrate 110 and the piezoelectric layer 2 .
  • At least one protrusion 140 extends in a direction intersecting the stacking direction Z (for example, the Y direction) from a portion forming the inner surface of the hollow portion 9 of the support substrate 110 and supports the piezoelectric layer 2 in the stacking direction Z.
  • the piezoelectric layer 2 has a membrane portion 21 .
  • the membrane part 21 constitutes a part of the piezoelectric layer 2 that at least partially overlaps the hollow part 9 in the stacking direction Z, for example.
  • a functional electrode 120 is positioned on the membrane portion 21 to form an excitation region.
  • the elastic wave device 1 is provided with four protrusions 140 .
  • two projections 140 are provided on each of the two surfaces 111 and 112 that face in the Y direction, and are spaced apart in the X direction that intersects the stacking directions Z and Y directions.
  • Each protrusion 140 provided on the surface 111 faces one of the protrusions 140 provided on the surface 112 in the Y direction and forms a pair.
  • the elastic wave device 1 has at least a pair of projections 140 facing each other in the facing direction (for example, Y direction).
  • the functional electrode 120 is, for example, an IDT electrode having a plurality of electrode fingers, and is positioned between two wiring electrodes 130 spaced apart in a direction intersecting the stacking direction Z (eg, Y direction).
  • the plurality of electrode fingers of the functional electrode 120 each extend along the Y direction and are positioned with gaps along the X direction.
  • Each electrode finger of the functional electrode 120 is connected to one of the two wiring electrodes 130 .
  • W1 is the dimension of the projection 140 in the extension direction (eg, Y direction) of the projection when viewed along the stacking direction Z
  • W2 is the dimension of the projection 140 in the width direction (eg, X direction) intersecting with the extension direction.
  • the dimension W1 is 5 ⁇ m or more and 20 ⁇ m or less
  • the dimension W2 is 5 ⁇ m or more and 50 ⁇ m or less.
  • the two wiring electrodes 130 are respectively referred to as a first bus bar 131 and a second bus bar 132, the electrode finger connected to the first bus bar 131 is referred to as a first electrode finger 121, and the electrode finger connected to the second bus bar 132 is referred to as a second electrode finger 122.
  • Each projection 140 extends, for example, along the facing direction (eg, Y direction) in which the first busbar 131 and the second busbar 132 face each other.
  • the two protrusions 140 provided on the surface 111 are located farther from the second bus bar 132 than the connection ends 133 to which the first electrode fingers 121 of the first bus bar 131 are connected in the facing direction.
  • the two protrusions 140 provided on the surface 112 are located farther from the first bus bar 131 than the connection ends 134 to which the second electrode fingers 122 of the second bus bar 132 are connected in the facing direction.
  • a distance W3 between the protrusion 140 and the connection ends 133 and 134 in the opposing direction is, for example, 0 ⁇ m or more and 5 ⁇ m or less.
  • FIG. 15 shows the distance W3 between the projection 140 and the connecting end 133 as an example.
  • FIG. 18 and 19 show the elastic wave device 100 without the protrusion 140.
  • FIG. 20 a plurality of convex structures 210 may be generated in the membrane part 21 due to heating such as reflow for substrate mounting (see FIG. 20), and the convex structures 210 may spread in the vertical and horizontal directions of the membrane part 21 and become larger.
  • a large concave deformation occurs in the region where the convex structure 210 contacts in the horizontal direction of the functional electrode 120, and a membrane crack 220 may occur in the region where the concave deformation occurs (see FIG. 21).
  • the acoustic wave device 1 of the second embodiment includes a support substrate 110, a piezoelectric layer 2 provided on the support substrate 110, a functional electrode 120 provided on the piezoelectric layer 2, a cavity 9, and at least one projection 140.
  • the hollow portion 9 is provided inside the support substrate 110 and is positioned so as to partially overlap the functional electrode 120 in plan view along the stacking direction Z.
  • At least one protrusion 140 extends in a direction intersecting the stacking direction Z from a portion forming the inner surface of the cavity 9 of the support substrate 110 and supports the piezoelectric layer 2 in the stacking direction Z. As shown in FIG.
  • the elastic wave device 1 of the second embodiment can also be configured as follows.
  • the plurality of electrode fingers may all have the same dimension in the width direction, or may have two or more different dimensions in the width direction.
  • the electrode fingers positioned between one end 141 and the other end 142 in the width direction (for example, the X direction) intersecting the extension direction of the protrusion 140 are inner electrode fingers 123, and the electrode fingers not positioned between the one end 141 and the other end 142 of the protrusion 140 in the width direction are outer electrode fingers 124.
  • the functional electrode 120 may be configured such that the widthwise dimension W4 of the inner electrode fingers 123 is 1.05 times or more the widthwise dimension W5 of the outer electrode fingers 124 and smaller than the widthwise dimension W2 of the projection 140.
  • Positioning the electrode fingers of the functional electrode 120 in the extending direction of the protrusion 140 can more reliably suppress downward deformation of the membrane portion 21 .
  • the growth of convex structures in the membrane portion 21 is suppressed, and the occurrence of cracks in the membrane portion 21 can be suppressed.
  • the total width of the electrode fingers included in the functional electrode 120 is increased, deformation of the membrane portion 21 can be suppressed and heat dissipation can be improved.
  • FIG. 17 shows an example of an elastic wave device 1 including functional electrodes 120 in which a plurality of electrode fingers all have the same dimension W6 in the width direction.
  • the functional electrode 120 has a plurality of electrode fingers (first electrode fingers 121) positioned between one end 141 and the other end 142 in the width direction (e.g., X direction) of the projection 140 when viewed along the stacking direction Z.
  • the electrode fingers of the functional electrode 120 are positioned in the extending direction of the projection 140, so downward deformation of the membrane portion 21 can be suppressed more reliably.
  • the total width of the electrode fingers included in the functional electrode 120 is increased, deformation of the membrane portion 21 can be suppressed and heat dissipation can be improved.
  • the elastic wave device 1 can be manufactured using any method such as a method of forming the cavity 9 using a sacrificial layer or a method of etching the support substrate 110 from the back surface.
  • the support substrate 110 may include the support member 8 and the insulating layer (bonding layer) 7 provided on the support member 8 (see FIG. 2), or may be composed of the support member 8 alone.
  • the support substrate 110 includes the support member 8 and the insulating layer 7 provided on the support member 8 , for example, the insulating layer 7 is provided on one main surface of the support member 8 facing the piezoelectric layer 2 .
  • the cavity 9 is provided in the insulating layer 7 at a position overlapping with a part of the functional electrode 120 in plan view along the stacking direction Z. As shown in FIG.
  • At least part of the configuration of the elastic wave device 1 of the second embodiment may be added to the elastic wave device 1 of the first embodiment, or at least part of the configuration of the elastic wave device 1 of the first embodiment may be added to the elastic wave device 1 of the second embodiment.
  • the elastic wave device of the first aspect is a support substrate; a piezoelectric layer provided on the support substrate; a functional electrode provided on the piezoelectric layer; a hollow portion provided inside the support substrate and overlapping with a part of the functional electrode in a plan view along the stacking direction of the support substrate and the piezoelectric layer; and at least one protrusion extending in a direction intersecting the stacking direction from a portion of the supporting substrate forming the inner surface of the hollow portion and supporting the piezoelectric layer in the stacking direction.
  • the elastic wave device of the second aspect is the elastic wave device of the first aspect, When viewed along the stacking direction, the dimension of the projection in the extension direction is 5 ⁇ m or more and 20 ⁇ m or less, and the dimension of the projection in the width direction intersecting the extension direction is 5 ⁇ m or more and 50 ⁇ m or less.
  • the elastic wave device of the third aspect is the elastic wave device of the first aspect or the second aspect
  • the functional electrode is a first bus bar and a second bus bar facing each other in a direction intersecting the stacking direction; a first electrode finger connected to the first busbar and extending from the first busbar toward the second busbar; a second electrode finger connected to the second bus bar and extending from the second bus bar toward the first bus bar;
  • the protrusion extends along the facing direction in which the first bus bar and the second bus bar face each other, and is located farther from the second bus bar in the facing direction than a connection end to which the first electrode finger of the first bus bar is connected.
  • the elastic wave device of the fourth aspect is the elastic wave device of any one of the first to third aspects, A distance between the protrusion and the connection end in the opposing direction is 0 ⁇ m or more and 5 ⁇ m or less.
  • the elastic wave device of the fifth aspect is the elastic wave device of the fourth aspect, A pair of said protrusions which oppose in the said opposing direction are provided.
  • the elastic wave device of the sixth aspect is the elastic wave device of any one of the first to fifth aspects, wherein the functional electrode has a plurality of electrode fingers extending along the direction in which the projection extends, Among the plurality of electrode fingers, when viewed along the stacking direction, an electrode finger positioned between one end and the other end in the width direction intersecting the extension direction is defined as an inner electrode finger, and an electrode finger not positioned between one end and the other end in the width direction is defined as an outer electrode finger, the width direction dimension of the inner electrode finger is 1.05 times or more the width direction dimension of the outer electrode finger and smaller than the width direction dimension of the protrusion.
  • the elastic wave device of the seventh aspect is the elastic wave device of any one of the first to fifth aspects
  • the functional electrode is The protrusion extends along the extension direction, and has a plurality of electrode fingers located between one end and the other end in the width direction that intersects the extension direction when viewed along the stacking direction.
  • the elastic wave device of the eighth aspect is the elastic wave device of any one of the first to seventh aspects
  • the support substrate includes a support member and a bonding layer provided on the support member;
  • the bonding layer is provided on one main surface of the support member facing the piezoelectric layer,
  • the hollow portion is provided in the bonding layer at a position overlapping with a part of the functional electrode in plan view along the stacking direction.
  • the elastic wave device of the ninth aspect is the elastic wave device of any one of the first to eighth aspects,
  • the functional electrodes are IDT electrodes.
  • the elastic wave device of the tenth aspect is the elastic wave device of the ninth aspect, the piezoelectric layer contains lithium niobate or lithium tantalate, the IDT electrode has a first electrode finger and a second electrode finger facing each other in a direction intersecting the stacking direction; the first electrode finger and the second electrode finger are adjacent electrodes; Where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the first electrode finger and the second electrode finger, d/p is 0.5 or less.
  • the elastic wave device of the eleventh aspect is the elastic wave device of the tenth aspect, d/p is 0.24 or less.
  • the elastic wave device of the twelfth aspect is the elastic wave device of the tenth aspect or the eleventh aspect,
  • a metallization ratio MR which is a ratio of the area of the first electrode fingers and the second electrode fingers in the excitation region to the excitation region, which is the region where the first electrode fingers and the second electrode fingers overlap, satisfies MR ⁇ 1.75 (d/p)+0.075 in the direction crossing the stacking direction.
  • the elastic wave device of the thirteenth aspect is the elastic wave device of any one of the tenth to twelfth aspects,
  • the Euler angles ( ⁇ , ⁇ , ⁇ ) of the lithium niobate or lithium tantalate are within the range of the following formula (1), formula (2) or formula (3).
  • Equation (1) (0° ⁇ 10°, 20° to 80°, 0° to 60° (1-( ⁇ -50) 2/900 ) 1/2 ) or (0° ⁇ 10°, 20° to 80°, [180°-60° (1-( ⁇ -50) 2/900 ) 1/2 ] to 180°) Equation (2)
  • Equation (3) (0° ⁇ 10°, [180°-30°(1-( ⁇ -90) 2 /8100) 1/2 ] ⁇ 180°, arbitrary ⁇ ) Equation (3)
  • the elastic wave device of the fourteenth aspect is the elastic wave device of any one of the ninth to thirteenth aspects, the piezoelectric layer contains lithium niobate or lithium tantalate, It is configured to be able to utilize bulk waves in the thickness-shlip mode.
  • the elastic wave device of the fifteenth aspect is the elastic wave device of any one of the first to eighth aspects, the piezoelectric layer contains lithium niobate or lithium tantalate, It is configured to be able to use plate waves.

Abstract

In the present invention, an elastic wave device comprises a support substrate, a piezoelectric layer provided on the support substrate, a functional electrode provided on the piezoelectric layer, a cavity part, and at least one protrusion. The cavity part is provided in the interior of the support substrate, and positioned overlapping a portion of the functional electrode in plan view as viewed along the direction in which the support substrate and the piezoelectric layer have been layered The at least one protrusion extends in the direction intersecting the layering direction from a part constituting the inner surface of the cavity part of the support substrate, and supports the piezoelectric layer in the layering direction.

Description

弾性波装置Acoustic wave device
　本開示は、圧電層（圧電体層）を備える弾性波装置に関する。 The present disclosure relates to an acoustic wave device including a piezoelectric layer (piezoelectric layer).
　例えば、特許文献１には、板波を利用する弾性波装置が開示されている。特許文献１に記載の弾性波装置は、支持体と、圧電基板と、ＩＤＴ電極とを備えている。支持体には、空洞部が設けられている。圧電基板は、支持体の上に空洞部と重なるように設けられている。ＩＤＴ電極は、圧電基板の上に空洞部と重なるように設けられている。弾性波装置では、ＩＤＴ電極により板波が励振される。空洞部の端縁部は、ＩＤＴ電極により励振される板波の伝搬方向と平行に延びる直線部を含まない。 For example, Patent Document 1 discloses an elastic wave device that uses plate waves. An acoustic wave device described in Patent Document 1 includes a support, a piezoelectric substrate, and an IDT electrode. The support is provided with a cavity. A piezoelectric substrate is provided on the support so as to overlap the cavity. The IDT electrode is provided on the piezoelectric substrate so as to overlap the cavity. In an elastic wave device, plate waves are excited by IDT electrodes. The edge of the cavity does not include a straight portion extending parallel to the propagation direction of the Lamb waves excited by the IDT electrodes.
特開２０１２－２５７０１９号公報JP 2012-257019 A
　近年、メンブレン構造を有する弾性波装置において、メンブレン部におけるクラックの発生を抑制可能な弾性波装置が求められている。 In recent years, in elastic wave devices having a membrane structure, there has been a demand for elastic wave devices capable of suppressing the occurrence of cracks in the membrane portion.
　本開示は、メンブレン部におけるクラックの発生を抑制可能な弾性波装置を提供することを目的とする。 An object of the present disclosure is to provide an elastic wave device capable of suppressing the occurrence of cracks in the membrane portion.
　本開示の一態様の弾性波装置は、
　支持基板と、
　前記支持基板上に設けられた圧電体層と、
　前記圧電体層上に設けられた機能電極と、
　前記支持基板の内部に設けられ、前記支持基板および前記圧電体層の積層方向に沿って見た平面視において前記機能電極の一部と重なる位置にある空洞部と、
　前記支持基板の前記空洞部の内面を構成する部分から前記積層方向に交差する方向に延びて、前記積層方向において前記圧電体層を支持する少なくとも１つの突起と
を備える。 An elastic wave device according to one aspect of the present disclosure includes:
a support substrate;
a piezoelectric layer provided on the support substrate;
a functional electrode provided on the piezoelectric layer;
a hollow portion provided inside the support substrate and overlapping with a part of the functional electrode in a plan view along the stacking direction of the support substrate and the piezoelectric layer;
and at least one protrusion extending in a direction intersecting the stacking direction from a portion of the supporting substrate forming the inner surface of the hollow portion and supporting the piezoelectric layer in the stacking direction.
　本開示によれば、メンブレン部におけるクラックの発生を抑制可能な弾性波装置を提供できる。 According to the present disclosure, it is possible to provide an elastic wave device capable of suppressing the occurrence of cracks in the membrane portion.
第１，第２の態様の弾性波装置の外観を示す略図的斜視図。1 is a schematic perspective view showing the appearance of elastic wave devices of first and second aspects; FIG. 圧電層上の電極構造を示す平面図。FIG. 4 is a plan view showing an electrode structure on the piezoelectric layer; 図１Ａ中のＡ－Ａ線に沿う部分の断面図。Sectional drawing of the part which follows the AA line in FIG. 1A. 従来の弾性波装置の圧電膜を伝搬するラム波を説明するための模式的正面断面図。FIG. 2 is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of a conventional elastic wave device. 本開示の弾性波装置の波を説明するための模式的正面断面図。FIG. 2 is a schematic front cross-sectional view for explaining waves of the elastic wave device of the present disclosure; 第１の電極と第２の電極との間に、第２の電極が第１の電極よりも高電位となる電圧が印加された場合のバルク波を示す模式図。FIG. 4 is a schematic diagram showing a bulk wave when a voltage is applied between the first electrode and the second electrode so that the potential of the second electrode is higher than that of the first electrode. 本開示の第１実施形態に係る弾性波装置の共振特性を示す図。FIG. 4 is a diagram showing resonance characteristics of the elastic wave device according to the first embodiment of the present disclosure; ｄ／２ｐと、弾性波装置の共振子としての比帯域との関係を示す図。FIG. 4 is a diagram showing the relationship between d/2p and the fractional bandwidth as a resonator of an acoustic wave device; 本開示の第１実施形態に係る別の弾性波装置の平面図。The top view of another elastic wave device concerning a 1st embodiment of this indication. 弾性波装置の共振特性の一例を示す参考図。FIG. 2 is a reference diagram showing an example of resonance characteristics of an elastic wave device; 多数の弾性波共振子を構成した場合の比帯域と、スプリアスの大きさとしての１８０度で規格化されたスプリアスのインピーダンスの位相回転量との関係を示す図。FIG. 4 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; ｄ／２ｐと、メタライゼーション比ＭＲと、比帯域との関係を示す図。4 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth; FIG. ｄ／ｐを限りなく０に近づけた場合のＬｉＮｂＯ３のオイラー角（０°，θ，ψ）に対する比帯域のマップを示す図。FIG. 4 is a diagram showing a map of the fractional bandwidth with respect to the Euler angles (0°, θ, ψ) of LiNbO 3 when d/p is infinitely close to 0; 本開示の第１実施形態に係る弾性波装置を説明するための部分切り欠き斜視図。1 is a partially cutaway perspective view for explaining an elastic wave device according to a first embodiment of the present disclosure; FIG. 本開示の第２実施形態の弾性波装置の一例を示す平面図。The top view which shows an example of the elastic wave apparatus of 2nd Embodiment of this indication. 図１３のXIV-XIV線に沿った断面図。Sectional drawing along the XIV-XIV line of FIG. 図１４のXV-XV線に沿った断面図。Sectional drawing along the XV-XV line of FIG. 図１３の弾性波装置の第１の変形例を示す平面図。The top view which shows the 1st modification of the elastic wave apparatus of FIG. 図１３の弾性波装置の第２の変形例を示す平面図。The top view which shows the 2nd modification of the elastic wave apparatus of FIG. 突起を備えていない弾性波装置の平面図。The top view of the elastic wave device which is not provided with the protrusion. 図１８のXIX-XIX線に沿った断面図。Sectional drawing along the XIX-XIX line of FIG. 図１８の弾性波装置のメンブレン部が変形した状態を説明するための第１の断面図。The 1st sectional drawing for demonstrating the state which the membrane part of the elastic wave apparatus of FIG. 18 deform|transformed. 図１８の弾性波装置のメンブレン部が変形した状態を説明するための第２の断面図。FIG. 19 is a second cross-sectional view for explaining a state in which the membrane portion of the elastic wave device of FIG. 18 is deformed;
　以下、本開示の一例を添付図面に従って説明する。以下の説明は、本質的に例示に過ぎず、本開示、本開示の適用物、または、本開示の用途を制限することを意図するものではない。図面は模式的なものであり、各寸法の比率等は現実のものとは必ずしも合致していない。 An example of the present disclosure will be described below with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the disclosure, the application of the disclosure, or the uses of the disclosure. The drawings are schematic, and the ratio of each dimension does not necessarily match the actual one.
　本開示における第１，第２，第３の態様の弾性波装置は、例えば、ニオブ酸リチウムまたはタンタル酸リチウムからなる圧電層と、圧電層の厚み方向に交差する方向において対向する第１電極及び第２電極とを備える。 The elastic wave devices of the first, second, and third aspects of the present disclosure include, for example, a piezoelectric layer made of lithium niobate or lithium tantalate, and a first electrode and a second electrode that face each other in a direction intersecting the thickness direction of the piezoelectric layer.
　第１の態様の弾性波装置では、厚み滑り１次モードのバルク波が利用されている。 In the elastic wave device of the first aspect, bulk waves in the primary mode of thickness shear are used.
　また、第２の態様の弾性波装置では、第１電極及び前記第２電極は隣り合う電極同士であり、圧電層の厚みをｄ、第１電極及び第２電極の中心間距離をｐとした場合、ｄ／ｐが０．５以下とされている。それによって、第１，第２の態様では、小型化を進めた場合であっても、Ｑ値を高めることができる。 Further, in the elastic wave device of the second aspect, the first electrode and the second electrode are adjacent electrodes, and d/p is 0.5 or less, where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the first electrode and the second electrode. As a result, in the first and second aspects, the Q value can be increased even when the miniaturization is promoted.
　また、第３の態様の弾性波装置では、板波としてのラム波が利用される。そして、上記ラム波による共振特性を得ることができる。 Also, in the elastic wave device of the third aspect, Lamb waves are used as plate waves. Then, resonance characteristics due to the Lamb wave can be obtained.
　本開示における第４の態様の弾性波装置は、ニオブ酸リチウムまたはタンタル酸リチウムからなる圧電層と、圧電層を挟んで圧電層の厚み方向に対向する上部電極及び下部電極とを備え、バルク波を利用する。 An elastic wave device according to a fourth aspect of the present disclosure includes a piezoelectric layer made of lithium niobate or lithium tantalate, and an upper electrode and a lower electrode facing each other in the thickness direction of the piezoelectric layer with the piezoelectric layer interposed therebetween, and utilizes bulk waves.
　以下、図面を参照しつつ、第１～第４の態様の弾性波装置の具体的な実施形態を説明することにより、本開示を明らかにする。 Hereinafter, the present disclosure will be clarified by describing specific embodiments of the elastic wave devices of the first to fourth aspects with reference to the drawings.
　なお、本明細書に記載の各実施形態は、例示的なものであり、異なる実施形態間において、構成の部分的な置換または組み合わせが可能であることを指摘しておく。 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.
（第１実施形態）
　図１Ａは、第１，第２の態様についての第１実施形態に係る弾性波装置の外観を示す略図的斜視図であり、図１Ｂは、圧電層上の電極構造を示す平面図であり、図２は、図１Ａ中のＡ－Ａ線に沿う部分の断面図である。 (First embodiment)
FIG. 1A is a schematic perspective view showing the appearance of the elastic wave device according to the first embodiment with respect to the first and second aspects, FIG. 1B is a plan view showing the electrode structure on the piezoelectric layer, and FIG. 2 is a cross-sectional view along line AA in FIG. 1A.
　弾性波装置１は、ＬｉＮｂＯ３からなる圧電層２を有する。圧電層２は、ＬｉＴａＯ３からなるものであってもよい。ＬｉＮｂＯ３やＬｉＴａＯ３のカット角は、本実施形態では、Ｚカットであるが、回転ＹカットやＸカットであってもよい。好ましくは、Ｙ伝搬及びＸ伝搬±３０°の伝搬方位が好ましい。圧電層２の厚みは、特に限定されないが、厚み滑り１次モードを効果的に励振するには、５０ｎｍ以上、１０００ｎｍ以下が好ましい。 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 in this embodiment, but may be rotational Y-cut or X-cut. Preferably, the Y-propagation and X-propagation ±30° propagation orientations are preferred. Although the thickness of the piezoelectric layer 2 is not particularly limited, it is preferably 50 nm or more and 1000 nm or less in order to effectively excite the thickness-shear primary mode.
　圧電層２は、対向し合う第１，第２の主面２ａ，２ｂを有する。第１の主面２ａ上に、電極３及び電極４が設けられている。ここで電極３が「第１電極」の一例であり、電極４が「第２電極」の一例である。図１Ａ及び図１Ｂでは、複数の電極３が、第１のバスバー５に接続されている複数の第１の電極指である。複数の電極４は、第２のバスバー６に接続されている複数の第２の電極指である。複数の電極３及び複数の電極４は、互いに間挿し合っている。 The piezoelectric layer 2 has first and second main 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. 1A and 1B, the multiple electrodes 3 are multiple first electrode fingers connected to a first busbar 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.
　電極３及び電極４は、矩形形状を有し、長さ方向を有する。この長さ方向と直交する方向において、電極３と、隣りの電極４とが対向している。これら複数の電極３，４、及び第１のバスバー５，第２のバスバー６によりＩＤＴ（Ｉｎｔｅｒｄｉｇｉｔａｌ　Ｔｒａｎｓｕｄｕｃｅｒ）電極が構成されている。電極３，４の長さ方向、及び、電極３，４の長さ方向と直交する方向はいずれも、圧電層２の厚み方向に交差する方向である。このため、電極３と、隣りの電極４とは、圧電層２の厚み方向に交差する方向において対向しているともいえる。 The electrodes 3 and 4 have a rectangular shape and a length direction. The electrode 3 and the adjacent electrode 4 face each other in a direction perpendicular to the length direction. These electrodes 3 and 4, the first bus bar 5 and the second bus bar 6 constitute an IDT (Interdigital Transducer) electrode. 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 intersecting the thickness direction of the piezoelectric layer 2 .
　また、電極３，４の長さ方向が図１Ａ及び図１Ｂに示す電極３，４の長さ方向に直交する方向と入れ替わってもよい。すなわち、図１Ａ及び図１Ｂにおいて、第１のバスバー５及び第２のバスバー６が延びている方向に電極３，４を延ばしてもよい。その場合、第１のバスバー５及び第２のバスバー６は、図１Ａ及び図１Ｂにおいて電極３，４が延びている方向に延びることとなる。 Also, the length direction of the electrodes 3 and 4 may be interchanged with the direction orthogonal to the length direction of the electrodes 3 and 4 shown in FIGS. 1A and 1B. That is, in FIGS. 1A and 1B, the electrodes 3 and 4 may extend in the direction in which the first 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. 1A and 1B.
　そして、一方電位に接続される電極３と、他方電位に接続される電極４とが隣り合う１対の構造が、上記電極３，４の長さ方向と直交する方向に、複数対設けられている。ここで電極３と電極４とが隣り合うとは、電極３と電極４とが直接接触するように配置されている場合ではなく、電極３と電極４とが間隔を介して配置されている場合を指す。 A plurality of pairs of adjacent electrodes 3 connected to one potential and electrodes 4 connected to the other potential are provided in a direction perpendicular to the length direction of the electrodes 3 and 4 . Here, the electrodes 3 and 4 are adjacent to each other, not when the electrodes 3 and 4 are arranged so as to be in direct contact, but when the electrodes 3 and 4 are arranged with a gap therebetween.
　また、電極３と電極４とが隣り合う場合、電極３と電極４との間には、他の電極３，４を含む、ホット電極やグランド電極に接続される電極は配置されない。この対数は、整数対である必要はなく、１．５対や２．５対などであってもよい。電極３，４間の中心間距離すなわちピッチは、１μｍ以上、１０μｍ以下の範囲が好ましい。また、電極３，４間の中心間距離とは、電極３の長さ方向と直交する方向における電極３の幅寸法の中心と、電極４の長さ方向と直交する方向における電極４の幅寸法の中心とを結んだ距離となる。さらに、電極３，４の少なくとも一方が複数本ある場合（電極３，４を一対の電極組とし、１．５対以上の電極組がある場合）、電極３，４の中心間距離は、１．５対以上の電極３，４のうち隣り合う電極３，４それぞれの中心間距離の平均値を指す。また、電極３，４の幅、すなわち電極３，４の対向方向の寸法は、１５０ｎｍ以上、１０００ｎｍ以下の範囲が好ましい。なお、電極３，４間の中心間距離とは、電極３の長さ方向と直交する方向における電極３の寸法（幅寸法）の中心と、電極４の長さ方向と直交する方向における電極４の寸法（幅寸法）の中心とを結んだ距離となる。 Also, when the electrode 3 and the electrode 4 are adjacent to each other, no electrode connected to the hot electrode or the ground electrode, including the other electrodes 3 and 4, is arranged between the electrode 3 and the electrode 4. 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. Further, the center-to-center distance between the electrodes 3 and 4 is the distance connecting the center of the width dimension of the electrode 3 in the direction perpendicular to the length direction of the electrode 3 and the center of the width dimension of the electrode 4 in the direction perpendicular to the length direction of the electrode 4. Furthermore, when at least one of the electrodes 3 and 4 is a plurality (when the electrodes 3 and 4 are a pair of electrodes and there are 1.5 or more pairs of electrodes), the center-to-center distance between the electrodes 3 and 4 refers to the average value of the center-to-center distances of the adjacent electrodes 3 and 4 among the 1.5 or more pairs of electrodes 3 and 4. Moreover, the width of the electrodes 3 and 4, that is, the dimension in the facing direction of the electrodes 3 and 4 is preferably in the range of 150 nm or more and 1000 nm or less. The center-to-center distance between the electrodes 3 and 4 is the distance between the center of the dimension (width dimension) of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the center of the dimension (width dimension) of the electrode 4 in the direction orthogonal to the length direction of the electrode 4.
　また、本実施形態では、Ｚカットの圧電層を用いているため、電極３，４の長さ方向と直交する方向は、圧電層２の分極方向に直交する方向となる。圧電層２として他のカット角の圧電体を用いた場合には、この限りでない。ここにおいて、「直交」とは、厳密に直交する場合のみに限定されず、略直交（電極３，４の長さ方向と直交する方向と分極方向とのなす角度が例えば９０°±１０°）でもよい。 In addition, since the Z-cut piezoelectric layer is used in this embodiment, 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 may be substantially perpendicular (the angle between the direction perpendicular to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, 90°±10°).
　圧電層２の第２の主面２ｂ側には、絶縁層７を介して支持部材８が積層されている。絶縁層７及び支持部材８は、枠状の形状を有し、図２に示すように、開口部７ａ，８ａを有する。それによって、空洞部９が形成されている。空洞部９は、圧電層２の励振領域Ｃの振動を妨げないために設けられている。従って、上記支持部材８は、少なくとも１対の電極３，４が設けられている部分と重ならない位置において、第２の主面２ｂに絶縁層７を介して積層されている。なお、絶縁層７は設けられずともよい。従って、支持部材８は、圧電層２の第２の主面２ｂに直接または間接に積層され得る。 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. 2, have openings 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 .
　絶縁層７は、酸化ケイ素からなる。もっとも、酸化ケイ素の他、酸窒化ケイ素、アルミナなどの適宜の絶縁性材料を用いることができる。支持部材８は、Ｓｉからなる。Ｓｉの圧電層２側の面における面方位は（１００）や（１１０）であってもよく、（１１１）であってもよい。好ましくは、抵抗率４ｋΩ以上の高抵抗のＳｉが望ましい。もっとも、支持部材８についても適宜の絶縁性材料や半導体材料を用いて構成することができる。支持部材８の材料としては、例えば、酸化アルミニウム、タンタル酸リチウム、ニオブ酸リチウム、水晶などの圧電体、アルミナ、マグネシア、サファイア、窒化ケイ素、窒化アルミニウム、炭化ケイ素、ジルコニア、コージライト、ムライト、ステアタイト、フォルステライトなどの各種セラミック、ダイヤモンド、ガラスなどの誘電体、窒化ガリウムなどの半導体などを用いることができる。 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). Preferably, high-resistance Si having a resistivity of 4 kΩ or more is desirable. However, the supporting member 8 can also be constructed using an appropriate insulating material or semiconductor material. Examples of materials for the support member 8 include piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and quartz crystal; various ceramics such as alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectrics such as diamond and glass; and semiconductors such as gallium nitride.
　上記複数の電極３，４及び第１，第２のバスバー５，６は、Ａｌ、ＡｌＣｕ合金などの適宜の金属もしくは合金からなる。本実施形態では、電極３，４及び第１，第２のバスバー５，６は、Ｔｉ膜上にＡｌ膜を積層した構造を有する。なお、Ｔｉ膜以外の密着層を用いてもよい。 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.
　駆動に際しては、複数の電極３と、複数の電極４との間に交流電圧を印加する。より具体的には、第１のバスバー５と第２のバスバー６との間に交流電圧を印加する。それによって、圧電層２において励振される厚み滑り１次モードのバルク波を利用した、共振特性を得ることが可能とされている。 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 a thickness-shear primary mode bulk wave excited in the piezoelectric layer 2 .
　また、弾性波装置１では、圧電層２の厚みをｄ、複数対の電極３，４のうちいずれかの隣り合う電極３，４の中心間距離をｐとした場合、ｄ／ｐは０．５以下とされている。そのため、上記厚み滑り１次モードのバルク波が効果的に励振され、良好な共振特性を得ることができる。より好ましくは、ｄ／ｐは０．２４以下であり、その場合には、より一層良好な共振特性を得ることができる。 In the elastic wave device 1, d/p is 0.5 or less, 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. As a result, the thickness-shear primary 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.
　なお、本実施形態のように電極３，４の少なくとも一方が複数本ある場合、すなわち、電極３，４を１対の電極組とし、電極３，４が１．５対以上ある場合、隣り合う電極３，４の中心間距離ｐは、各隣り合う電極３，４の中心間距離の平均距離となる。 When at least one of the electrodes 3 and 4 is plural as in the present embodiment, that is, when the electrodes 3 and 4 form one pair of electrodes and there are 1.5 or more pairs of the electrodes 3 and 4, the center-to-center distance p between the adjacent electrodes 3 and 4 is the average distance between the centers of the adjacent electrodes 3 and 4.
　本実施形態の弾性波装置１では、上記構成を備えるため、小型化を図ろうとして、電極３，４の対数を小さくしたとしても、Ｑ値の低下が生じ難い。これは、両側に反射器を必要としない共振器であり、伝搬ロスが少ないためである。また、上記反射器を必要としないのは、厚み滑り１次モードのバルク波を利用していることによる。 Since the elastic wave device 1 of the present embodiment has the above configuration, even if the logarithm of the electrodes 3 and 4 is reduced in order to reduce the size, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides, and the propagation loss is small. The reason why the above reflector is not required is that the bulk wave of the thickness-shlip primary mode is used.
　従来の弾性波装置で利用したラム波と、上記厚み滑り１次モードのバルク波の相違を、図３Ａ及び図３Ｂを参照して説明する。 The difference between the Lamb wave used in the conventional elastic wave device and the bulk wave of the thickness shear primary mode will be described with reference to FIGS. 3A and 3B.
　図３Ａは、従来の弾性波装置の圧電膜を伝搬するラム波を説明するための模式的正面断面図である。従来の弾性波装置については、例えば、特許文献１（特開２０１２－２５７０１９号公報）に記載されている。図３Ａに示すように、従来の弾性波装置においては、圧電膜２０１中を矢印で示すように波が伝搬する。ここで、圧電膜２０１では、第１の主面２０１ａと、第２の主面２０１ｂとが対向しており、第１の主面２０１ａと第２の主面２０１ｂとを結ぶ厚み方向がＺ方向である。Ｘ方向は、ＩＤＴ電極の電極指が並んでいる方向である。図３Ａに示すように、ラム波では、波が図示のように、Ｘ方向に伝搬していく。板波であるため、圧電膜２０１が全体として振動するものの、波はＸ方向に伝搬するため、両側に反射器を配置して、共振特性を得ている。そのため、波の伝搬ロスが生じ、小型化を図った場合、すなわち電極指の対数を少なくした場合、Ｑ値が低下する。 FIG. 3A is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of a conventional elastic wave device. A conventional elastic wave device is described, for example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2012-257019). As shown in FIG. 3A, in the conventional acoustic wave device, 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. The X direction is the direction in which the electrode fingers of the IDT electrodes are arranged. As shown in FIG. 3A, in the Lamb wave, the 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.
　これに対して、図３Ｂに示すように、本実施形態の弾性波装置１では、振動変位は厚み滑り方向であるから、波は、圧電層２の第１の主面２ａと第２の主面２ｂとを結ぶ方向、すなわちＺ方向にほぼ伝搬し、共振する。すなわち、波のＸ方向成分がＺ方向成分に比べて著しく小さい。そして、このＺ方向の波の伝搬により共振特性が得られるため、反射器を必要としない。よって、反射器に伝搬する際の伝搬損失は生じない。従って、小型化を進めようとして、電極３，４からなる電極対の対数を減らしたとしても、Ｑ値の低下が生じ難い。 On the other hand, as shown in FIG. 3B, in the acoustic wave device 1 of the present embodiment, since the vibration displacement is in the thickness shear direction, the wave propagates and resonates substantially in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, in the Z direction. 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, no reflector is required. Therefore, no propagation loss occurs when propagating to the reflector. Therefore, 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.
　なお、厚み滑り１次モードのバルク波の振幅方向は、図４に示すように、圧電層２の励振領域Ｃに含まれる第１領域４５１と、励振領域Ｃに含まれる第２領域４５２とで逆になる。図４は、電極３と電極４との間に、電極４が電極３よりも高電位となる電圧が印加された場合のバルク波を模式的に示している。第１領域４５１は、励振領域Ｃのうち、圧電層２の厚み方向に直交し圧電層２を２分する仮想平面ＶＰ１と、第１の主面２ａとの間の領域である。第２領域４５２は、励振領域Ｃのうち、仮想平面ＶＰ１と、第２の主面２ｂとの間の領域である。 It should be noted that the amplitude direction of the bulk wave of the thickness shear primary 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. FIG. 4 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.
　上記のように、弾性波装置１では、電極３と電極４とからなる少なくとも１対の電極が配置されているが、Ｘ方向に波を伝搬させるものではないため、この電極３，４からなる電極対の対数は複数対ある必要は必ずしもない。すなわち、少なくとも１対の電極が設けられてさえおればよい。 As described above, in the elastic wave device 1, at least one pair of electrodes consisting of the electrodes 3 and 4 is arranged, but since the waves are not propagated in the X direction, the number of electrode pairs consisting of the electrodes 3 and 4 does not necessarily need to be plural. That is, it is sufficient that at least one pair of electrodes is provided.
　例えば、上記電極３がホット電位に接続される電極であり、電極４がグラウンド電位に接続される電極である。もっとも、電極３がグラウンド電位に、電極４がホット電位に接続されてもよい。本実施形態では、少なくとも１対の電極は、上記のように、ホット電位に接続される電極またはグラウンド電位に接続される電極であり、浮き電極は設けられていない。 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.
　図５は、本開示の第１実施形態の弾性波装置の共振特性を示す図である。なお、この共振特性を得た弾性波装置１の設計パラメータは以下の通りである。
　圧電層２：オイラー角（０°，０°，９０°）のＬｉＮｂＯ３、厚み＝４００ｎｍ。
　電極３と電極４の長さ方向と直交する方向に視たときに、電極３と電極４とが重なっている領域、すなわち励振領域Ｃの長さ＝４０μｍ、電極３，４からなる電極の対数＝２１対、電極間中心距離＝３μｍ、電極３，４の幅＝５００ｎｍ、ｄ／ｐ＝０．１３３。
　絶縁層７：１μｍの厚みの酸化ケイ素膜。
　支持部材８：Ｓｉ。 FIG. 5 is a diagram showing resonance characteristics of the acoustic wave device according to the first embodiment of the present disclosure. 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 a 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 consisting of the electrodes 3 and 4 = 21 pairs, the center distance between the electrodes = 3 µm, the width of the electrodes 3 and 4 = 500 nm, and d/p = 0.133.
Insulating layer 7: Silicon oxide film with a thickness of 1 μm.
Support member 8: Si.
　なお、励振領域Ｃの長さとは、励振領域Ｃの電極３，４の長さ方向に沿う寸法である。 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.
　本実施形態では、電極３，４からなる電極対の電極間距離は、複数対において全て等しくした。すなわち、電極３と電極４とを等ピッチで配置した。 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.
　図５から明らかなように、反射器を有しないにもかかわらず、比帯域が１２．５％である良好な共振特性が得られている。 As is clear from FIG. 5, good resonance characteristics with a specific bandwidth of 12.5% are obtained in spite of having no reflector.
　ところで、上記圧電層２の厚みをｄ、電極３と電極４との電極の中心間距離をｐとした場合、前述したように、本実施形態では、ｄ／ｐは０．５以下、より好ましくは０．２４以下である。これを、図６を参照して説明する。 By the way, when the thickness of the piezoelectric layer 2 is d and the distance between the centers of the electrodes 3 and 4 is p, in the present embodiment, d/p is 0.5 or less, more preferably 0.24 or less. This will be explained with reference to FIG.
　図５に示した共振特性を得た弾性波装置と同様に、但しｄ／２ｐを変化させ、複数の弾性波装置を得た。図６は、このｄ／２ｐと、弾性波装置の共振子としての比帯域との関係を示す図である。 A plurality of elastic wave devices were obtained by changing d/2p in the same manner as the elastic wave device that obtained the resonance characteristics shown in FIG. FIG. 6 is a diagram showing the relationship between this d/2p and the fractional bandwidth of the acoustic wave device as a resonator.
　図６から明らかなように、ｄ／２ｐが０．２５を超えると、すなわちｄ／ｐ＞０．５では、ｄ／ｐを調整しても、比帯域は５％未満である。これに対して、ｄ／２ｐ≦０．２５、すなわちｄ／ｐ≦０．５の場合には、その範囲内でｄ／ｐを変化させれば、比帯域を５％以上とすることができ、すなわち高い結合係数を有する共振子を構成することができる。また、ｄ／２ｐが０．１２以下の場合、すなわちｄ／ｐが０．２４以下の場合には、比帯域を７％以上と高めることができる。加えて、ｄ／ｐをこの範囲内で調整すれば、より一層比帯域の広い共振子を得ることができ、より一層高い結合係数を有する共振子を実現することができる。従って、本開示の第２の態様の弾性波装置のように、ｄ／ｐを０．５以下とすることにより、上記厚み滑り１次モードのバルク波を利用した、高い結合係数を有する共振子を構成し得ることがわかる。 As is clear from FIG. 6, when d/2p exceeds 0.25, that is, when d/p>0.5, even if d/p is adjusted, the fractional bandwidth is less than 5%. On the other hand, if d/2p≦0.25, that is, d/p≦0.5, the fractional bandwidth can be increased to 5% or more by changing d/p within that range, that is, a resonator having a high coupling coefficient can be constructed. Further, when d/2p is 0.12 or less, that is, when d/p is 0.24 or less, the 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 as in the elastic wave device of the second aspect of the present disclosure, it is possible to configure a resonator having a high coupling coefficient using the bulk wave of the primary thickness-shlip mode.
　なお、前述したように、少なくとも１対の電極は、１対でもよく、上記ｐは、１対の電極の場合、隣り合う電極３，４の中心間距離とする。また、１．５対以上の電極の場合には、隣り合う電極３，４の中心間距離の平均距離をｐとすればよい。 As described above, at least one pair of electrodes may be one pair, and p is the center-to-center distance between adjacent electrodes 3 and 4 in the case of one pair of electrodes. In the case of 1.5 pairs or more of electrodes, the average distance between the centers of adjacent electrodes 3 and 4 should be p.
　また、圧電層の厚みｄについても、圧電層２が厚みばらつきを有する場合、その厚みを平均化した値を採用すればよい。 Also, for the thickness d of the piezoelectric layer, if the piezoelectric layer 2 has variations in thickness, a value obtained by averaging the thickness may be adopted.
　図７は、本開示の第１実施形態に係る別の弾性波装置の平面図である。弾性波装置３１では、圧電層２の第１の主面２ａ上において、電極３と電極４とを有する１対の電極が設けられている。なお、図７中のＫが交差幅となる。前述したように、本開示の弾性波装置３１では、電極の対数は１対であってもよい。この場合においても、上記ｄ／ｐが０．５以下であれば、厚み滑り１次モードのバルク波を効果的に励振することができる。 FIG. 7 is a plan view of another elastic wave device according to the first embodiment of the present disclosure. In elastic wave device 31 , 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. 7 is the intersection width. As described above, in the elastic wave device 31 of the present disclosure, the number of pairs of electrodes may be one. Even in this case, if the above d/p is 0.5 or less, it is possible to effectively excite the bulk wave in the primary mode of thickness shear.
　弾性波装置１では、好ましくは、複数の電極３，４において、いずれかの隣り合う電極３，４が対向している方向に視たときに重なっている領域である励振領域に対する、上記隣り合う電極３，４のメタライゼーション比ＭＲが、ＭＲ≦１．７５（ｄ／ｐ）＋０．０７５を満たすことが望ましい。つまり、隣り合う複数の第１電極指と複数の第２電極指とが対向している方向に視たときに複数の第１電極指と複数の第２電極指とが重なっている領域が励振領域（交差領域）であり、励振領域に対する、複数の第１電極指及び複数の第２電極指のメタライゼーション比をＭＲとしたときに、ＭＲ≦１．７５（ｄ／ｐ）＋０．０７５を満たすことが好ましい。その場合には、スプリアスを効果的に小さくすることができる。 In the elastic wave device 1, it is preferable that the metallization ratio MR of the adjacent electrodes 3 and 4 with respect to the excitation region, which is the overlapping region when viewed in the direction in which one of the adjacent electrodes 3 and 4 faces each other, satisfies MR≦1.75 (d/p)+0.075. That is, when viewed in the direction in which the plurality of adjacent first electrode fingers and the plurality of second electrode fingers are opposed to each other, the region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap is the excitation region (intersection region), and when the metallization ratio of the plurality of first electrode fingers and the plurality of second electrode fingers to the excitation region is MR, it is preferable to satisfy MR≦1.75 (d/p)+0.075. In that case, spurious can be effectively reduced.
　これを、図８及び図９を参照して説明する。図８は、上記弾性波装置１の共振特性の一例を示す参考図である。矢印Ｂで示すスプリアスが、共振周波数と反共振周波数との間に現れている。なお、ｄ／ｐ＝０．０８として、かつＬｉＮｂＯ３のオイラー角（０°，０°，９０°）とした。また、上記メタライゼーション比ＭＲ＝０．３５とした。 This will be described with reference to FIGS. 8 and 9. FIG. FIG. 8 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.
　メタライゼーション比ＭＲを、図１Ｂを参照して説明する。図１Ｂの電極構造において、１対の電極３，４に着目した場合、この１対の電極３，４のみが設けられるとする。この場合、一点鎖線Ｃで囲まれた部分が励振領域となる。この励振領域とは、電極３と電極４とを、電極３，４の長さ方向と直交する方向すなわち対向方向に視たときに電極３における電極４と重なり合っている領域、電極４における電極３と重なり合っている領域、及び、電極３と電極４との間の領域における電極３と電極４とが重なり合っている領域である。そして、この励振領域の面積に対する、励振領域Ｃ内の電極３，４の面積が、メタライゼーション比ＭＲとなる。すなわち、メタライゼーション比ＭＲは、メタライゼーション部分の面積の励振領域の面積に対する比である。 The metallization ratio MR will be explained with reference to FIG. 1B. In the electrode structure of FIG. 1B, when focusing 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 portion surrounded by the dashed-dotted line C is the excitation region. 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 the facing direction, the excitation regions are regions in which the electrodes 3 and 4 overlap, regions in which the electrodes 4 overlap the electrodes 3, and regions between the electrodes 3 and 4 in which the electrodes 3 and 4 overlap. The area of the electrodes 3 and 4 in the excitation region C with respect to the area of this excitation region 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.
　なお、複数対の電極が設けられている場合、励振領域の面積の合計に対する全励振領域に含まれているメタライゼーション部分の割合をＭＲとすればよい。 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.
　図９は本実施形態に従って、多数の弾性波共振子を構成した場合の比帯域と、スプリアスの大きさとしての１８０度で規格化されたスプリアスのインピーダンスの位相回転量との関係を示す図である。なお、比帯域については、圧電層の膜厚や電極の寸法を種々変更し、調整した。また、図９は、ＺカットのＬｉＮｂＯ３からなる圧電層を用いた場合の結果であるが、他のカット角の圧電層を用いた場合においても、同様の傾向となる。 FIG. 9 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 elastic wave resonators are configured according to this embodiment. The ratio band was adjusted by changing the film thickness of the piezoelectric layer and the dimensions of the electrodes. Also, FIG. 9 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.
　図９中の楕円Ｊで囲まれている領域では、スプリアスが１．０と大きくなっている。図９から明らかなように、比帯域が０．１７を超えると、すなわち１７％を超えると、スプリアスレベルが１以上の大きなスプリアスが、比帯域を構成するパラメータを変化させたとしても、通過帯域内に現れる。すなわち、図８に示す共振特性のように、矢印Ｂで示す大きなスプリアスが帯域内に現れる。よって、比帯域は１７％以下であることが好ましい。この場合には、圧電層２の膜厚や電極３，４の寸法などを調整することにより、スプリアスを小さくすることができる。 In the area surrounded by ellipse J in FIG. 9, the spurious is as large as 1.0. As is clear from FIG. 9, when the fractional band exceeds 0.17, that is, exceeds 17%, a large spurious with a spurious level of 1 or more appears in the passband even if the parameters constituting the fractional band are changed. That is, as in the resonance characteristics shown in FIG. 8, 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.
　図１０は、ｄ／２ｐと、メタライゼーション比ＭＲと、比帯域との関係を示す図である。上記弾性波装置において、ｄ／２ｐと、ＭＲが異なる様々な弾性波装置を構成し、比帯域を測定した。図１０の破線Ｄの右側のハッチングを付して示した部分が、比帯域が１７％以下の領域である。このハッチングを付した領域と、付していない領域との境界は、ＭＲ＝３．５（ｄ／２ｐ）＋０．０７５で表される。すなわち、ＭＲ＝１．７５（ｄ／ｐ）＋０．０７５である。従って、好ましくは、ＭＲ≦１．７５（ｄ／ｐ）＋０．０７５である。その場合には、比帯域を１７％以下としやすい。より好ましくは、図１０中の一点鎖線Ｄ１で示すＭＲ＝３．５（ｄ／２ｐ）＋０．０５の右側の領域である。すなわち、ＭＲ≦１．７５（ｄ／ｐ）＋０．０５であれば、比帯域を確実に１７％以下にすることができる。 FIG. 10 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. 10 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.
　図１１は、ｄ／ｐを限りなく０に近づけた場合のＬｉＮｂＯ３のオイラー角（０°，θ，ψ）に対する比帯域のマップを示す図である。図１１のハッチングを付して示した部分が、少なくとも５％以上の比帯域が得られる領域であり、当該領域の範囲を近似すると、下記の式（１）、式（２）及び式（３）で表される範囲となる。 FIG. 11 is a diagram showing a map of the fractional bandwidth with respect to the Euler angles (0°, θ, ψ) of LiNbO 3 when d/p is infinitely close to 0. In FIG. The hatched portion in FIG. 11 is a region where a fractional bandwidth of at least 5% or more is obtained, and the range of the region is approximated by the following formulas (1), (2), and (3).
　（０°±１０°，０°～２０°，任意のψ）　　…式（１） (0°±10°, 0° to 20°, arbitrary ψ) ……Equation (1)
　（０°±１０°，２０°～８０°，０°～６０°（１－（θ－５０）２／９００）１／２）　または　（０°±１０°，２０°～８０°，［１８０°－６０°（１－（θ－５０）２／９００）１／２］～１８０°）　　…式（２） (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 ] to 180°) Equation (2)
　（０°±１０°，［１８０°－３０°（１－（ψ－９０）２／８１００）１／２］～１８０°，任意のψ）　　…式（３） (0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
　従って、上記式（１）、式（２）または式（３）のオイラー角範囲の場合、比帯域を十分に広くすることができ、好ましい。 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.
　図１２は、本開示の第１実施形態の変形例に係る弾性波装置を説明するための部分切り欠き斜視図である。弾性波装置８１は、支持基板８２を有する。支持基板８２には、上面に開いた凹部が設けられている。支持基板８２上に圧電層８３が積層されている。それによって、空洞部９が構成されている。この空洞部９の上方において圧電層８３上に、ＩＤＴ電極８４が設けられている。ＩＤＴ電極８４の弾性波伝搬方向両側に、反射器８５，８６が設けられている。図１２において、空洞部９の外周縁を破線で示す。ここでは、ＩＤＴ電極８４は、第１，第２のバスバー８４ａ，８４ｂと、複数本の第１の電極指としての電極８４ｃ及び複数本の第２の電極指としての電極８４ｄとを有する。複数本の電極８４ｃは、第１のバスバー８４ａに接続されている。複数本の電極８４ｄは、第２のバスバー８４ｂに接続されている。複数本の電極８４ｃと、複数本の電極８４ｄとは間挿し合っている。 FIG. 12 is a partially cutaway perspective view for explaining an elastic wave device according to a modification of the first embodiment of the present disclosure. The elastic wave device 81 has a support substrate 82 . The support substrate 82 is provided with a concave portion that is open on the upper surface. A piezoelectric layer 83 is laminated on the support substrate 82 . A hollow portion 9 is thereby formed. An IDT electrode 84 is provided on the piezoelectric layer 83 above the cavity 9 . Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction. In FIG. 12, the outer periphery of the hollow portion 9 is indicated by broken lines. Here, the IDT electrode 84 has first and second bus bars 84a and 84b, an electrode 84c as a plurality of first electrode fingers and an electrode 84d as a plurality of second electrode fingers. The multiple electrodes 84c are connected to the first bus bar 84a. The multiple electrodes 84d are connected to the second bus bar 84b. The multiple electrodes 84c and the multiple electrodes 84d are interposed.
　弾性波装置８１では、上記空洞部９上のＩＤＴ電極８４に、交流電界を印加することにより、板波としてのラム波が励振される。そして、反射器８５，８６が両側に設けられているため、上記ラム波による共振特性を得ることができる。 In the elastic wave device 81, a Lamb wave as a plate wave is excited by applying an AC electric field to the IDT electrodes 84 on the cavity 9. Since the reflectors 85 and 86 are provided on both sides, the resonance characteristics due to the Lamb wave can be obtained.
　このように、本開示の弾性波装置は、板波を利用するものであってもよい。 Thus, the elastic wave device of the present disclosure may utilize plate waves.
（第２実施形態）
　第２実施形態の弾性波装置１について説明する。第２実施形態においては、第１実施形態と重複する内容については適宜、説明を省略する。第２実施形態においては、第１実施形態で説明した内容を適用することができる。 (Second embodiment)
An elastic wave device 1 according to a second embodiment will be described. In the second embodiment, descriptions of the same contents as in the first embodiment will be omitted as appropriate. In the second embodiment, the contents described in the first embodiment can be applied.
　図１３および図１４に示すように、弾性波装置１は、支持基板１１０と、支持基板１１０上に設けられた圧電層２と、圧電層２上に設けられた機能電極１２０とを備える。支持基板１１０の内部には、空洞部９と、少なくとも１つの突起１４０とが設けられている。空洞部９は、支持基板１１０および圧電層２の積層方向（例えば、Ｚ方向）に沿って見た平面視において、機能電極１２０の一部と重なる位置に設けられている。少なくとも１つの突起１４０は、支持基板１１０の空洞部９の内面を構成する部分から積層方向Ｚに交差する方向（例えば、Ｙ方向）に延びて、積層方向Ｚにおいて圧電層２を支持する。 As shown in FIGS. 13 and 14, the elastic wave device 1 includes a support substrate 110, a piezoelectric layer 2 provided on the support substrate 110, and a functional electrode 120 provided on the piezoelectric layer 2. A hollow portion 9 and at least one protrusion 140 are provided inside the support substrate 110 . The hollow portion 9 is provided at a position overlapping with a portion of the functional electrode 120 in plan view along the stacking direction (for example, Z direction) of the support substrate 110 and the piezoelectric layer 2 . At least one protrusion 140 extends in a direction intersecting the stacking direction Z (for example, the Y direction) from a portion forming the inner surface of the hollow portion 9 of the support substrate 110 and supports the piezoelectric layer 2 in the stacking direction Z.
　圧電層２は、メンブレン部２１を有している。メンブレン部２１は、例えば、積層方向Ｚにおいて少なくとも部分的に空洞部９を重なる圧電層２の一部を構成している。メンブレン部２１には、機能電極１２０が位置し、励振領域を形成する。 The piezoelectric layer 2 has a membrane portion 21 . The membrane part 21 constitutes a part of the piezoelectric layer 2 that at least partially overlaps the hollow part 9 in the stacking direction Z, for example. A functional electrode 120 is positioned on the membrane portion 21 to form an excitation region.
　本実施形態では、弾性波装置１は、４つの突起１４０を備えている。各突起１４０は、空洞部９を構成する支持基板１１０の内面のうち、Ｙ方向に対向する２つの面１１１、１１２にそれぞれ２つ、積層方向ＺおよびＹ方向に交差するＸ方向に間隔を空けて設けられている。面１１１に設けられている各突起１４０は、面１１２に設けられている突起１４０の１つとＹ方向において対向し、対を成している。つまり、弾性波装置１は、対向方向（例えば、Ｙ方向）において対向する少なくとも一対の突起１４０を備えている。 In this embodiment, the elastic wave device 1 is provided with four protrusions 140 . Of the inner surfaces of the support substrate 110 forming the hollow portion 9, two projections 140 are provided on each of the two surfaces 111 and 112 that face in the Y direction, and are spaced apart in the X direction that intersects the stacking directions Z and Y directions. Each protrusion 140 provided on the surface 111 faces one of the protrusions 140 provided on the surface 112 in the Y direction and forms a pair. In other words, the elastic wave device 1 has at least a pair of projections 140 facing each other in the facing direction (for example, Y direction).
　機能電極１２０は、例えば、複数の電極指を有するＩＤＴ電極であり、積層方向Ｚに交差する方向（例えば、Ｙ方向）において間隔を空けて配置された２つの配線電極１３０の間に位置している。機能電極１２０の複数の電極指は、それぞれＹ方向に沿って延びており、Ｘ方向に沿って隙間を空けて位置している。機能電極１２０の各電極指は、２つの配線電極１３０のいずれかに接続されている。 The functional electrode 120 is, for example, an IDT electrode having a plurality of electrode fingers, and is positioned between two wiring electrodes 130 spaced apart in a direction intersecting the stacking direction Z (eg, Y direction). The plurality of electrode fingers of the functional electrode 120 each extend along the Y direction and are positioned with gaps along the X direction. Each electrode finger of the functional electrode 120 is connected to one of the two wiring electrodes 130 .
　図１５に示すように、積層方向Ｚに沿って見た場合における突起が延びる延長方向（例えば、Ｙ方向）における突起１４０の寸法をＷ１とし、延長方向に交差する幅方向（例えば、Ｘ方向）における突起１４０の寸法をＷ２とする。例えば、寸法Ｗ１は５μｍ以上２０μｍ以下であり、寸法Ｗ２は５μｍ以上５０μｍ以下である。 As shown in FIG. 15, W1 is the dimension of the projection 140 in the extension direction (eg, Y direction) of the projection when viewed along the stacking direction Z, and W2 is the dimension of the projection 140 in the width direction (eg, X direction) intersecting with the extension direction. For example, the dimension W1 is 5 μm or more and 20 μm or less, and the dimension W2 is 5 μm or more and 50 μm or less.
　２つの配線電極１３０をそれぞれ第１バスバー１３１および第２バスバー１３２とし、第１バスバー１３１に接続された電極指を第１電極指１２１とし、第２バスバー１３２に接続された電極指を第２電極指１２２とする。各突起１４０は、例えば、第１バスバー１３１および第２バスバー１３２が対向する対向方向（例えば、Ｙ方向）に沿って延びている。例えば、図１４に示すように、面１１１に設けられている２つの突起１４０は、対向方向において第１バスバー１３１の第１電極指１２１が接続されている接続端１３３よりも第２バスバー１３２から離れた位置にある。面１１２に設けられている２つの突起１４０は、対向方向において第２バスバー１３２の第２電極指１２２が接続されている接続端１３４よりも第１バスバー１３１から離れた位置にある。対向方向における突起１４０および接続端１３３、１３４の間の距離Ｗ３は、例えば、ゼロμｍ以上５μｍ以下である。図１５には、一例として、突起１４０および接続端１３３の間の距離Ｗ３を示している。 The two wiring electrodes 130 are respectively referred to as a first bus bar 131 and a second bus bar 132, the electrode finger connected to the first bus bar 131 is referred to as a first electrode finger 121, and the electrode finger connected to the second bus bar 132 is referred to as a second electrode finger 122. Each projection 140 extends, for example, along the facing direction (eg, Y direction) in which the first busbar 131 and the second busbar 132 face each other. For example, as shown in FIG. 14, the two protrusions 140 provided on the surface 111 are located farther from the second bus bar 132 than the connection ends 133 to which the first electrode fingers 121 of the first bus bar 131 are connected in the facing direction. The two protrusions 140 provided on the surface 112 are located farther from the first bus bar 131 than the connection ends 134 to which the second electrode fingers 122 of the second bus bar 132 are connected in the facing direction. A distance W3 between the protrusion 140 and the connection ends 133 and 134 in the opposing direction is, for example, 0 μm or more and 5 μm or less. FIG. 15 shows the distance W3 between the projection 140 and the connecting end 133 as an example.
　図１８および図１９に、突起１４０を備えていない弾性波装置１００を示す。弾性波装置１００では、基板実装のためのリフローなどの加熱により、メンブレン部２１に複数の凸構造２１０が発生し（図２０参照）、メンブレン部２１の縦横方向に凸構造２１０が広がって大きくなる場合がある。この場合、機能電極１２０の横方向における凸構造２１０が接触する領域で大きな凹変形が発生し、凹変形が発生した領域においてメンブレンクラック２２０が発生するおそれがある（図２１参照）。 18 and 19 show the elastic wave device 100 without the protrusion 140. FIG. In the acoustic wave device 100, a plurality of convex structures 210 may be generated in the membrane part 21 due to heating such as reflow for substrate mounting (see FIG. 20), and the convex structures 210 may spread in the vertical and horizontal directions of the membrane part 21 and become larger. In this case, a large concave deformation occurs in the region where the convex structure 210 contacts in the horizontal direction of the functional electrode 120, and a membrane crack 220 may occur in the region where the concave deformation occurs (see FIG. 21).
　第２実施形態の弾性波装置１では、支持基板１１０と、支持基板１１０上に設けられた圧電層２と、圧電層２上に設けられた機能電極１２０と、空洞部９と、少なくとも１つの突起１４０とを備える。空洞部９は、支持基板１１０の内部に設けられ、積層方向Ｚに沿って見た平面視において機能電極１２０の一部と重なる位置にある。少なくとも１つの突起１４０は、支持基板１１０の空洞部９の内面を構成する部分から積層方向Ｚに交差する方向に延びて、積層方向Ｚにおいて圧電層２を支持する。このような構成により、基板実装等のためのリフロー時において、メンブレン部２１に発生し得る凸構造の成長を抑制することができる。その結果、メンブレン部（言い換えると、圧電層２の空洞部９を覆う部分）におけるクラックの発生を抑制できる。 The acoustic wave device 1 of the second embodiment includes a support substrate 110, a piezoelectric layer 2 provided on the support substrate 110, a functional electrode 120 provided on the piezoelectric layer 2, a cavity 9, and at least one projection 140. The hollow portion 9 is provided inside the support substrate 110 and is positioned so as to partially overlap the functional electrode 120 in plan view along the stacking direction Z. As shown in FIG. At least one protrusion 140 extends in a direction intersecting the stacking direction Z from a portion forming the inner surface of the cavity 9 of the support substrate 110 and supports the piezoelectric layer 2 in the stacking direction Z. As shown in FIG. With such a configuration, it is possible to suppress the growth of convex structures that may occur in the membrane portion 21 during reflow for substrate mounting or the like. As a result, the occurrence of cracks in the membrane portion (in other words, the portion covering the hollow portion 9 of the piezoelectric layer 2) can be suppressed.
　第２実施形態の弾性波装置１は、次のように構成することもできる。 The elastic wave device 1 of the second embodiment can also be configured as follows.
　機能電極１２０は、複数の電極指が全て同じ幅方向の寸法を有していてもよいし、２種類以上の異なる幅方向の寸法を有していてもよい。 In the functional electrode 120, the plurality of electrode fingers may all have the same dimension in the width direction, or may have two or more different dimensions in the width direction.
　例えば、図１６に示すように、機能電極１２０の複数の電極指のうち、積層方向Ｚに沿って見た場合、突起１４０の延長方向に交差する幅方向（例えば、Ｘ方向）の一端１４１および他端１４２の間に位置する電極指を内電極指１２３とし、突起１４０の幅方向の一端１４１および他端１４２の間に位置しない電極指を外電極指１２４とする。この場合、内電極指１２３の幅方向の寸法Ｗ４が、外電極指１２４の幅方向の寸法Ｗ５の１．０５倍以上で、かつ、突起１４０の幅方向の寸法Ｗ２よりも小さくなるように、機能電極１２０を構成してもよい。突起１４０の延長方向に機能電極１２０の電極指を位置させることで、メンブレン部２１の下方向への変形をより確実に抑制できる。その結果、メンブレン部２１において凸構造の成長が抑制され、メンブレン部２１におけるクラックの発生を抑制できる。また、機能電極１２０に含まれる電極指の幅の合計が大きくなるので、メンブレン部２１の変形を抑制しつつ、放熱性を向上させることができる。 For example, as shown in FIG. 16, among the plurality of electrode fingers of the functional electrode 120, when viewed along the stacking direction Z, the electrode fingers positioned between one end 141 and the other end 142 in the width direction (for example, the X direction) intersecting the extension direction of the protrusion 140 are inner electrode fingers 123, and the electrode fingers not positioned between the one end 141 and the other end 142 of the protrusion 140 in the width direction are outer electrode fingers 124. In this case, the functional electrode 120 may be configured such that the widthwise dimension W4 of the inner electrode fingers 123 is 1.05 times or more the widthwise dimension W5 of the outer electrode fingers 124 and smaller than the widthwise dimension W2 of the projection 140. Positioning the electrode fingers of the functional electrode 120 in the extending direction of the protrusion 140 can more reliably suppress downward deformation of the membrane portion 21 . As a result, the growth of convex structures in the membrane portion 21 is suppressed, and the occurrence of cracks in the membrane portion 21 can be suppressed. In addition, since the total width of the electrode fingers included in the functional electrode 120 is increased, deformation of the membrane portion 21 can be suppressed and heat dissipation can be improved.
　図１７に、複数の電極指が全て同じ幅方向の寸法W６を有している機能電極１２０を備える弾性波装置１の一例と示す。図１７の弾性波装置１では、機能電極１２０が、積層方向Ｚに沿って見た場合、突起１４０の幅方向（例えば、Ｘ方向）の一端１４１および他端１４２の間に位置する複数の電極指（第１電極指１２１）を有している。この場合も図１６の弾性波装置１と同様に、突起１４０の延長方向に機能電極１２０の電極指が位置しているので、メンブレン部２１の下方向への変形をより確実に抑制できる。また、機能電極１２０に含まれる電極指の幅の合計が大きくなるので、メンブレン部２１の変形を抑制しつつ、放熱性を向上させることができる。 FIG. 17 shows an example of an elastic wave device 1 including functional electrodes 120 in which a plurality of electrode fingers all have the same dimension W6 in the width direction. In the elastic wave device 1 of FIG. 17, the functional electrode 120 has a plurality of electrode fingers (first electrode fingers 121) positioned between one end 141 and the other end 142 in the width direction (e.g., X direction) of the projection 140 when viewed along the stacking direction Z. In this case, similarly to the elastic wave device 1 of FIG. 16, the electrode fingers of the functional electrode 120 are positioned in the extending direction of the projection 140, so downward deformation of the membrane portion 21 can be suppressed more reliably. In addition, since the total width of the electrode fingers included in the functional electrode 120 is increased, deformation of the membrane portion 21 can be suppressed and heat dissipation can be improved.
　弾性波装置１は、犠牲層を用いて空洞部９を形成する方法、または、支持基板１１０を裏面からエッチングする方法等の任意の方法を用いて製造できる。 The elastic wave device 1 can be manufactured using any method such as a method of forming the cavity 9 using a sacrificial layer or a method of etching the support substrate 110 from the back surface.
　支持基板１１０は、支持部材８と支持部材８上に設けられた絶縁層（接合層）７とを含んでいてもよいし（図２参照）、支持部材８のみで構成されていてもよい。支持基板１１０が、支持部材８と、支持部材８の上に設けられた絶縁層７とを含む場合、例えば、絶縁層７は、圧電層２と対向する支持部材８の一方主面に設けられる。空洞部９は、積層方向Ｚに沿って見た平面視において機能電極１２０の一部と重なる位置で絶縁層７に設けられる。 The support substrate 110 may include the support member 8 and the insulating layer (bonding layer) 7 provided on the support member 8 (see FIG. 2), or may be composed of the support member 8 alone. When the support substrate 110 includes the support member 8 and the insulating layer 7 provided on the support member 8 , for example, the insulating layer 7 is provided on one main surface of the support member 8 facing the piezoelectric layer 2 . The cavity 9 is provided in the insulating layer 7 at a position overlapping with a part of the functional electrode 120 in plan view along the stacking direction Z. As shown in FIG.
　第１実施形態の弾性波装置１に、第２実施形態の弾性波装置１の構成の少なくとも一部を追加してもよいし、第２実施形態の弾性波装置１に、第１実施形態の弾性波装置１の構成の少なくとも一部を追加してもよい。 At least part of the configuration of the elastic wave device 1 of the second embodiment may be added to the elastic wave device 1 of the first embodiment, or at least part of the configuration of the elastic wave device 1 of the first embodiment may be added to the elastic wave device 1 of the second embodiment.
　以上、図面を参照して本開示における種々の実施形態を詳細に説明したが、最後に、本開示の種々の態様について説明する。 Various embodiments of the present disclosure have been described in detail above with reference to the drawings. Finally, various aspects of the present disclosure will be described.
　第１態様の弾性波装置は、
　支持基板と、
　前記支持基板上に設けられた圧電体層と、
　前記圧電体層上に設けられた機能電極と、
　前記支持基板の内部に設けられ、前記支持基板および前記圧電体層の積層方向に沿って見た平面視において前記機能電極の一部と重なる位置にある空洞部と、
　前記支持基板の前記空洞部の内面を構成する部分から前記積層方向に交差する方向に延びて、前記積層方向において前記圧電体層を支持する少なくとも１つの突起と
を備える。 The elastic wave device of the first aspect is
a support substrate;
a piezoelectric layer provided on the support substrate;
a functional electrode provided on the piezoelectric layer;
a hollow portion provided inside the support substrate and overlapping with a part of the functional electrode in a plan view along the stacking direction of the support substrate and the piezoelectric layer;
and at least one protrusion extending in a direction intersecting the stacking direction from a portion of the supporting substrate forming the inner surface of the hollow portion and supporting the piezoelectric layer in the stacking direction.
　第２態様の弾性波装置は、第１態様の弾性波装置において、
　前記積層方向に沿って見た場合、前記突起が延びる延長方向における前記突起の寸法が５μｍ以上２０μｍ以下であり、前記延長方向に交差する幅方向における前記突起の寸法が５μｍ以上５０μｍ以下である。 The elastic wave device of the second aspect is the elastic wave device of the first aspect,
When viewed along the stacking direction, the dimension of the projection in the extension direction is 5 μm or more and 20 μm or less, and the dimension of the projection in the width direction intersecting the extension direction is 5 μm or more and 50 μm or less.
　第３態様の弾性波装置は、第１態様または第２態様の弾性波装置において、
　前記機能電極が、
　前記積層方向に交差する方向において対向する第１バスバーおよび第２バスバーと、
　前記第１バスバーに接続され、前記第１バスバーから前記第２バスバーに向かって延びる第１電極指と、
　前記第２バスバーに接続され、前記第２バスバーから前記第１バスバーに向かって延びる第２電極指と
を有し、
　前記突起が、前記第１バスバーおよび前記第２バスバーが対向する対向方向に沿って延び、前記対向方向において前記第１バスバーの前記第１電極指が接続されている接続端よりも前記第２バスバーから離れた位置にある。 The elastic wave device of the third aspect is the elastic wave device of the first aspect or the second aspect,
The functional electrode is
a first bus bar and a second bus bar facing each other in a direction intersecting the stacking direction;
a first electrode finger connected to the first busbar and extending from the first busbar toward the second busbar;
a second electrode finger connected to the second bus bar and extending from the second bus bar toward the first bus bar;
The protrusion extends along the facing direction in which the first bus bar and the second bus bar face each other, and is located farther from the second bus bar in the facing direction than a connection end to which the first electrode finger of the first bus bar is connected.
　第４態様の弾性波装置は、第１態様～第３態様のいずれかの弾性波装置において、
　前記対向方向における前記突起および前記接続端の間の距離が、ゼロμｍ以上５μｍ以下である。 The elastic wave device of the fourth aspect is the elastic wave device of any one of the first to third aspects,
A distance between the protrusion and the connection end in the opposing direction is 0 μm or more and 5 μm or less.
　第５態様の弾性波装置は、第４態様の弾性波装置において、
　前記対向方向において対向する一対の前記突起を備える。 The elastic wave device of the fifth aspect is the elastic wave device of the fourth aspect,
A pair of said protrusions which oppose in the said opposing direction are provided.
　第６態様の弾性波装置は、第１態様～第５態様のいずれかの弾性波装置において、
　前記機能電極が、前記突起が延びる延長方向に沿って延びる複数の電極指を有し、
　前記複数の電極指のうち、前記積層方向に沿って見た場合、前記延長方向に交差する幅方向の一端および他端の間に位置する電極指を内電極指とし、前記幅方向の一端および他端の間に位置しない電極指を外電極指とすると、前記内電極指の前記幅方向の寸法が、前記外電極指の前記幅方向の寸法の１．０５倍以上で、かつ、前記突起の前記幅方向の寸法よりも小さい。 The elastic wave device of the sixth aspect is the elastic wave device of any one of the first to fifth aspects,
wherein the functional electrode has a plurality of electrode fingers extending along the direction in which the projection extends,
Among the plurality of electrode fingers, when viewed along the stacking direction, an electrode finger positioned between one end and the other end in the width direction intersecting the extension direction is defined as an inner electrode finger, and an electrode finger not positioned between one end and the other end in the width direction is defined as an outer electrode finger, the width direction dimension of the inner electrode finger is 1.05 times or more the width direction dimension of the outer electrode finger and smaller than the width direction dimension of the protrusion.
　第７態様の弾性波装置は、第１態様～第５態様のいずれかの弾性波装置において、
　前記機能電極が、
　前記突起が延びる延長方向に沿って延びると共に、前記積層方向に沿って見た場合、前記延長方向に交差する幅方向の一端および他端の間に位置する複数の電極指を有する。 The elastic wave device of the seventh aspect is the elastic wave device of any one of the first to fifth aspects,
The functional electrode is
The protrusion extends along the extension direction, and has a plurality of electrode fingers located between one end and the other end in the width direction that intersects the extension direction when viewed along the stacking direction.
　第８態様の弾性波装置は、第１態様～第７態様のいずれかの弾性波装置において、
　前記支持基板が、支持部材と、前記支持部材の上に設けられた接合層とを含み、
　前記接合層は、前記圧電体層と対向する前記支持部材の一方主面に設けられており、
　前記空洞部は、前記積層方向に沿って見た平面視において前記機能電極の一部と重なる位置で前記接合層に設けられている。 The elastic wave device of the eighth aspect is the elastic wave device of any one of the first to seventh aspects,
the support substrate includes a support member and a bonding layer provided on the support member;
The bonding layer is provided on one main surface of the support member facing the piezoelectric layer,
The hollow portion is provided in the bonding layer at a position overlapping with a part of the functional electrode in plan view along the stacking direction.
　第９態様の弾性波装置は、第１態様～第８態様のいずれかの弾性波装置において、
　前記機能電極がＩＤＴ電極である。 The elastic wave device of the ninth aspect is the elastic wave device of any one of the first to eighth aspects,
The functional electrodes are IDT electrodes.
　第１０態様の弾性波装置は、第９態様の弾性波装置において、
　前記圧電体層が、ニオブ酸リチウムまたはタンタル酸リチウムを含み、
　前記ＩＤＴ電極が、前記積層方向に交差する方向において対向する第１電極指および第２電極指を有し、
　前記第１電極指および前記第２電極指は隣り合う電極同士であり、
　前記圧電体層の厚みをｄ、前記第１電極指および前記第２電極指との中心間距離をｐとした場合、ｄ／ｐが０．５以下である。 The elastic wave device of the tenth aspect is the elastic wave device of the ninth aspect,
the piezoelectric layer contains lithium niobate or lithium tantalate,
the IDT electrode has a first electrode finger and a second electrode finger facing each other in a direction intersecting the stacking direction;
the first electrode finger and the second electrode finger are adjacent electrodes;
Where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the first electrode finger and the second electrode finger, d/p is 0.5 or less.
　第１１態様の弾性波装置は、第１０態様の弾性波装置において、
　ｄ／ｐが０．２４以下である。 The elastic wave device of the eleventh aspect is the elastic wave device of the tenth aspect,
d/p is 0.24 or less.
　第１２態様の弾性波装置は、第１０態様または第１１態様の弾性波装置において、
　前記積層方向に交差する方向において、前記第１電極指および前記第２電極指が重なり合っている領域である励振領域に対する、前記励振領域内の前記第１電極指および前記第２電極指の面積の割合であるメタライゼーション比ＭＲが、ＭＲ≦１．７５（ｄ／ｐ）＋０．０７５を満たす。 The elastic wave device of the twelfth aspect is the elastic wave device of the tenth aspect or the eleventh aspect,
A metallization ratio MR, which is a ratio of the area of the first electrode fingers and the second electrode fingers in the excitation region to the excitation region, which is the region where the first electrode fingers and the second electrode fingers overlap, satisfies MR≦1.75 (d/p)+0.075 in the direction crossing the stacking direction.
　第１３態様の弾性波装置は、第１０態様～第１２態様のいずれかの弾性波装置において、
　前記ニオブ酸リチウムまたはタンタル酸リチウムのオイラー角（φ，θ，ψ）が、以下の式（１）、式（２）または式（３）の範囲にある。
　（０°±１０°，０°～２０°，任意のψ）　　…式（１）
　（０°±１０°，２０°～８０°，０°～６０°（１－（θ－５０）２／９００）１／２）　または　（０°±１０°，２０°～８０°，［１８０°－６０°（１－（θ－５０）２／９００）１／２］～１８０°）　　…式（２）
　（０°±１０°，［１８０°－３０°（１－（ψ－９０）２／８１００）１／２］～１８０°，任意のψ）　　…式（３） The elastic wave device of the thirteenth aspect is the elastic wave device of any one of the tenth to twelfth aspects,
The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate are within the range of the following formula (1), formula (2) or formula (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 ] to 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
　第１４態様の弾性波装置は、第９態様～第１３態様のいずれかの弾性波装置において、
　前記圧電体層が、ニオブ酸リチウムまたはタンタル酸リチウムを含み、
　厚み滑りモードのバルク波を利用可能に構成されている。 The elastic wave device of the fourteenth aspect is the elastic wave device of any one of the ninth to thirteenth aspects,
the piezoelectric layer contains lithium niobate or lithium tantalate,
It is configured to be able to utilize bulk waves in the thickness-shlip mode.
　第１５態様の弾性波装置は、第１態様～第８態様のいずれかの弾性波装置において、
　前記圧電体層が、ニオブ酸リチウムまたはタンタル酸リチウムを含み、
　板波を利用可能に構成されている。 The elastic wave device of the fifteenth aspect is the elastic wave device of any one of the first to eighth aspects,
the piezoelectric layer contains lithium niobate or lithium tantalate,
It is configured to be able to use plate waves.
　前記様々な実施形態または変形例のうちの任意の実施形態または変形例を適宜組み合わせることにより、それぞれの有する効果を奏するようにすることができる。また、実施形態同士の組み合わせまたは実施例同士の組み合わせまたは実施形態と実施例との組み合わせが可能であると共に、異なる実施形態または実施例の中の特徴同士の組み合わせも可能である。 By appropriately combining any of the various embodiments or modifications described above, the respective effects can be achieved. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, as well as combinations of features in different embodiments or examples.
　本開示は、添付図面を参照しながら好ましい実施形態に関連して充分に記載されているが、この技術の熟練した人々にとっては種々の変形や修正は明白である。そのような変形や修正は、添付した請求の範囲による本開示の範囲から外れない限りにおいて、その中に含まれると理解されるべきである。 Although the present disclosure has been fully described in connection with preferred embodiments with reference to the accompanying drawings, various variations and modifications will be apparent to those skilled in the art. Such variations and modifications are to be understood as included therein insofar as they do not depart from the scope of the present disclosure by the appended claims.

Claims (15)

  1. 　支持基板と、
    　前記支持基板上に設けられた圧電体層と、
    　前記圧電体層上に設けられた機能電極と、
    　前記支持基板の内部に設けられ、前記支持基板および前記圧電体層の積層方向に沿って見た平面視において前記機能電極の一部と重なる位置にある空洞部と、
    　前記支持基板の前記空洞部の内面を構成する部分から前記積層方向に交差する方向に延びて、前記積層方向において前記圧電体層を支持する少なくとも１つの突起と
    を備える、弾性波装置。     a support substrate;
    a piezoelectric layer provided on the support substrate;
    a functional electrode provided on the piezoelectric layer;
    a hollow portion provided inside the support substrate and overlapping with a part of the functional electrode in a plan view along the stacking direction of the support substrate and the piezoelectric layer;
    and at least one projection extending in a direction intersecting the stacking direction from a portion of the support substrate forming the inner surface of the hollow portion and supporting the piezoelectric layer in the stacking direction.
  2. 　前記積層方向に沿って見た場合、前記突起が延びる延長方向における前記突起の寸法が５μｍ以上２０μｍ以下であり、前記延長方向に交差する幅方向における前記突起の寸法が５μｍ以上５０μｍ以下である、請求項１に記載の弾性波装置。 The elastic wave device according to claim 1, wherein, when viewed along the stacking direction, the dimension of the projection in the extension direction in which the projection extends is 5 µm or more and 20 µm or less, and the dimension of the projection in the width direction intersecting the extension direction is 5 µm or more and 50 µm or less.
  3. 　前記機能電極が、
    　前記積層方向に交差する方向において対向する第１バスバーおよび第２バスバーと、
    　前記第１バスバーに接続され、前記第１バスバーから前記第２バスバーに向かって延びる第１電極指と、
    　前記第２バスバーに接続され、前記第２バスバーから前記第１バスバーに向かって延びる第２電極指と
    を有し、
    　前記突起が、前記第１バスバーおよび前記第２バスバーが対向する対向方向に沿って延び、前記対向方向において前記第１バスバーの前記第１電極指が接続されている接続端よりも前記第２バスバーから離れた位置にある、請求項１または２に記載の弾性波装置。     The functional electrode is
    a first bus bar and a second bus bar facing each other in a direction intersecting the stacking direction;
    a first electrode finger connected to the first busbar and extending from the first busbar toward the second busbar;
    a second electrode finger connected to the second bus bar and extending from the second bus bar toward the first bus bar;
    The elastic wave device according to claim 1 or 2, wherein the protrusion extends along the facing direction in which the first bus bar and the second bus bar face each other, and is located farther from the second bus bar than a connection end to which the first electrode finger of the first bus bar is connected in the facing direction.
  4. 　前記対向方向における前記突起および前記接続端の間の距離が、ゼロμｍ以上５μｍ以下である、請求項３に記載の弾性波装置。 The elastic wave device according to claim 3, wherein the distance between the projection and the connection end in the opposing direction is 0 µm or more and 5 µm or less.
  5. 　前記対向方向において対向する一対の前記突起を備える、請求項４に記載の弾性波装置。 The elastic wave device according to claim 4, comprising a pair of said protrusions facing each other in said facing direction.
  6. 　前記機能電極が、前記突起が延びる延長方向に沿って延びる複数の電極指を有し、
    　前記複数の電極指のうち、前記積層方向に沿って見た場合、前記延長方向に交差する幅方向の一端および他端の間に位置する電極指を内電極指とし、前記幅方向の一端および他端の間に位置しない電極指を外電極指とすると、前記内電極指の前記幅方向の寸法が、前記外電極指の前記幅方向の寸法の１．０５倍以上で、かつ、前記突起の前記幅方向の寸法よりも小さい、請求項１から５のいずれか１つに記載の弾性波装置。     wherein the functional electrode has a plurality of electrode fingers extending along the direction in which the projection extends,
    The elastic wave device according to any one of claims 1 to 5, wherein, when viewed along the stacking direction, the electrode fingers positioned between one end and the other end in the width direction intersecting the extension direction are inner electrode fingers, and the electrode fingers not positioned between one end and the other end in the width direction are outer electrode fingers, the width direction dimension of the inner electrode fingers being 1.05 times or more the width direction dimension of the outer electrode fingers and smaller than the width direction dimension of the projection. .
  7. 　前記機能電極が、
    　前記突起が延びる延長方向に沿って延びると共に、前記積層方向に沿って見た場合、前記延長方向に交差する幅方向の一端および他端の間に位置する複数の電極指を有する、請求項１から５のいずれか１つに記載の弾性波装置。     The functional electrode is
    The elastic wave device according to any one of claims 1 to 5, wherein the projection extends along the extension direction and, when viewed along the stacking direction, has a plurality of electrode fingers located between one end and the other end in a width direction that intersects with the extension direction.
  8. 　前記支持基板が、支持部材と、前記支持部材の上に設けられた接合層とを含み、
    　前記接合層は、前記圧電体層と対向する前記支持部材の一方主面に設けられており、
    　前記空洞部は、前記積層方向に沿って見た平面視において前記機能電極の一部と重なる位置で前記接合層に設けられている、請求項１から７のいずれか１つに記載の弾性波装置。     the support substrate includes a support member and a bonding layer provided on the support member;
    The bonding layer is provided on one main surface of the support member facing the piezoelectric layer,
    The elastic wave device according to any one of claims 1 to 7, wherein the cavity is provided in the bonding layer at a position overlapping with a part of the functional electrode in plan view along the stacking direction.
  9. 　前記機能電極がＩＤＴ電極である、請求項１から８のいずれか１つに記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 8, wherein the functional electrode is an IDT electrode.
  10. 　前記圧電体層が、ニオブ酸リチウムまたはタンタル酸リチウムを含み、
    　前記ＩＤＴ電極が、前記積層方向に交差する方向において対向する第１電極指および第２電極指を有し、
    　前記第１電極指および前記第２電極指は隣り合う電極同士であり、
    　前記圧電体層の厚みをｄ、前記第１電極指および前記第２電極指との中心間距離をｐとした場合、ｄ／ｐが０．５以下である、請求項９に記載の弾性波装置。     the piezoelectric layer contains lithium niobate or lithium tantalate,
    the IDT electrode has a first electrode finger and a second electrode finger facing each other in a direction intersecting the stacking direction;
    the first electrode finger and the second electrode finger are adjacent electrodes;
    10. The elastic wave device according to claim 9, wherein d/p is 0.5 or less, where d is the thickness of the piezoelectric layer and p is the center-to-center distance between the first electrode finger and the second electrode finger.
  11. 　ｄ／ｐが０．２４以下である、請求項１０に記載の弾性波装置。 The elastic wave device according to claim 10, wherein d/p is 0.24 or less.
  12. 　前記積層方向に交差する方向において、前記第１電極指および前記第２電極指が重なり合っている領域である励振領域に対する、前記励振領域内の前記第１電極指および前記第２電極指の面積の割合であるメタライゼーション比ＭＲが、ＭＲ≦１．７５（ｄ／ｐ）＋０．０７５を満たす、請求項１０または１１に記載の弾性波装置。 The elastic wave device according to claim 10 or 11, wherein a metallization ratio MR, which is a ratio of the area of the first electrode fingers and the second electrode fingers in the excitation region to the excitation region, which is the region where the first electrode fingers and the second electrode fingers overlap, satisfies MR≦1.75 (d/p)+0.075 in the direction crossing the stacking direction.
  13. 　前記ニオブ酸リチウムまたはタンタル酸リチウムのオイラー角（φ，θ，ψ）が、以下の式（１）、式（２）または式（３）の範囲にある、請求項１０から１２のいずれか１つに記載の弾性波装置。
    　（０°±１０°，０°～２０°，任意のψ）　　…式（１）
    　（０°±１０°，２０°～８０°，０°～６０°（１－（θ－５０）２／９００）１／２）　または　（０°±１０°，２０°～８０°，［１８０°－６０°（１－（θ－５０）２／９００）１／２］～１８０°）　　…式（２）
    　（０°±１０°，［１８０°－３０°（１－（ψ－９０）２／８１００）１／２］～１８０°，任意のψ）　　…式（３）     The elastic wave device according to any one of claims 10 to 12, wherein Euler angles (φ, θ, ψ) of said lithium niobate or lithium tantalate are in the range of the following formula (1), formula (2) or formula (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 ] to 180°) Equation (2)
    (0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
  14. 　前記圧電体層が、ニオブ酸リチウムまたはタンタル酸リチウムを含み、
    　厚み滑りモードのバルク波を利用可能に構成されている、請求項９から１３のいずれか１つに記載の弾性波装置。     the piezoelectric layer contains lithium niobate or lithium tantalate,
    The acoustic wave device according to any one of claims 9 to 13, configured to be able to use thickness-shear mode bulk waves.
  15. 　前記圧電体層が、ニオブ酸リチウムまたはタンタル酸リチウムを含み、
    　板波を利用可能に構成されている、請求項１から８のいずれか１つに記載の弾性波装置。     the piezoelectric layer contains lithium niobate or lithium tantalate,
    The acoustic wave device according to any one of claims 1 to 8, configured to be able to use plate waves.
PCT/JP2023/001277 2022-01-19 2023-01-18 Elastic wave device WO2023140272A1 (en)

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