WO2022045086A1 - Elastic wave device - Google Patents

Elastic wave device Download PDF

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Publication number
WO2022045086A1
WO2022045086A1 PCT/JP2021/030875 JP2021030875W WO2022045086A1 WO 2022045086 A1 WO2022045086 A1 WO 2022045086A1 JP 2021030875 W JP2021030875 W JP 2021030875W WO 2022045086 A1 WO2022045086 A1 WO 2022045086A1
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electrode
piezoelectric layer
electrodes
elastic wave
wave device
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PCT/JP2021/030875
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French (fr)
Japanese (ja)
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峰文 大内
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株式会社村田製作所
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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
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • 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 elastic wave device having a piezoelectric layer containing lithium niobate or lithium tantalate.
  • Patent Document 1 describes an elastic wave device.
  • the present disclosure has been made in view of the above, and an object of the present disclosure is to provide an elastic wave device that suppresses deterioration of resonance characteristics.
  • the elastic wave device has a first main surface and a second main surface opposite to the first main surface and in a first direction with respect to the first main surface. At least one pair of electrodes facing each other in the second direction intersecting the first direction and adjacently provided on the first main surface, and the first pair of electrodes of the piezoelectric layer.
  • a protective film covering the main surface and the pair of electrodes is provided, and each of the pair of electrodes is on the first surface and the side opposite to the first surface and on the piezoelectric layer side.
  • the protective film has a second surface, and the upper surface of the protective film covering the first surface of at least one of the pair of electrodes is viewed in the first direction, and the protective film in the second direction.
  • Equation (1) is satisfied. 0.3 ⁇ L / H ⁇ 1.0 ...
  • FIG. 1A is a perspective view showing an elastic wave device of the first embodiment.
  • FIG. 1B is a plan view showing the electrode structure of the first embodiment.
  • FIG. 2 is a cross-sectional view of a portion of FIG. 1A along line II-II.
  • FIG. 3A is a schematic cross-sectional view for explaining a Lamb wave propagating in the piezoelectric layer of the comparative example.
  • FIG. 3B is a schematic cross-sectional view for explaining the bulk wave of the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment.
  • FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of the bulk wave in the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment.
  • FIG. 1A is a perspective view showing an elastic wave device of the first embodiment.
  • FIG. 1B is a plan view showing the electrode structure of the first embodiment.
  • FIG. 2 is a cross-sectional view of a portion of FIG. 1A along line
  • FIG. 5 is an explanatory diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment.
  • FIG. 6 shows d / 2p as a resonator in the elastic wave apparatus of the first embodiment, where p is the center-to-center distance or the average distance between the centers of adjacent electrodes and d is the average thickness of the piezoelectric layer. It is explanatory drawing which shows the relationship with the specific band of.
  • FIG. 7 is a plan view showing an example in which a pair of electrodes is provided in the elastic wave device of the first embodiment.
  • FIG. 8 is a modification of the first embodiment, and is a cross-sectional view of a portion of FIG. 1A along the line II-II.
  • FIG. 9 is a cross-sectional view of a portion of FIG.
  • FIG. 10 is an explanatory diagram for explaining the relationship between the protective film and spurious.
  • FIG. 11 is an explanatory diagram for explaining the relationship between the spurious frequency and the resonance frequency.
  • FIG. 12 is a cross-sectional view of another example of the portion along the IX-IX line of FIG. 1B.
  • FIG. 13 is a cross-sectional view of another example of the portion along the IX-IX line of FIG. 1B.
  • FIG. 14 is a cross-sectional view of another example of the portion along the IX-IX line of FIG. 1B.
  • FIG. 1A is a perspective view showing an elastic wave device of the first embodiment.
  • FIG. 1B is a plan view showing the electrode structure of the first embodiment.
  • the elastic wave device 1 of the first embodiment has a piezoelectric layer 2 made of LiNbO 3 .
  • the piezoelectric layer 2 may be made of LiTaO 3 .
  • the cut angle of LiNbO 3 and LiTaO 3 is Z-cut in the first embodiment.
  • the cut angle of LiNbO 3 or LiTaO 3 may be a rotary Y cut or an X cut. Propagation directions of Y propagation and X propagation ⁇ 30 ° are preferable.
  • the thickness of the piezoelectric layer 2 is not particularly limited, but is preferably 50 nm or more and 1000 nm or less in order to effectively excite the thickness slip primary mode.
  • the piezoelectric layer 2 has a first main surface 2a facing each other in the Z direction and a second main surface 2b.
  • the electrode 3 and the electrode 4 are provided on the first main surface 2a.
  • the electrode 3 is an example of the "first electrode”
  • the electrode 4 is an example of the "second electrode”.
  • a plurality of electrodes 3 are connected to the first bus bar 5.
  • the plurality of electrodes 4 are connected to the second bus bar 6.
  • the plurality of electrodes 3 and the plurality of electrodes 4 are interleaved with each other.
  • the electrode 3 and the electrode 4 have a rectangular shape and have a length direction.
  • the electrode 3 and the electrode 4 adjacent to the electrode 3 face each other in a direction orthogonal to the length direction.
  • the length direction of the electrode 3 and the electrode 4 and the direction orthogonal to the length direction of the electrode 3 and the electrode 4 are all directions intersecting with each other in the thickness direction of the piezoelectric layer 2. Therefore, it can be said that the electrode 3 and the electrode 4 adjacent to the electrode 3 face each other in a direction intersecting with each other in the thickness direction of the piezoelectric layer 2.
  • the thickness direction of the piezoelectric layer 2 is the Z direction (or the first direction)
  • the direction orthogonal to the length direction of the electrode 3 and the electrode 4 is the X direction (or the second direction)
  • the electrode 3 is the Y direction (or the third direction).
  • the length directions of the electrodes 3 and 4 may be replaced with the directions orthogonal to the length directions 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 be extended in the direction in which the first bus bar 5 and the second bus bar 6 are extended. In that case, the first bus bar 5 and the second bus bar 6 extend in the direction in which the electrodes 3 and 4 extend in FIGS. 1A and 1B. Then, a plurality of pairs of structures in which the electrode 3 connected to one potential and the electrode 4 connected to the other potential are adjacent to each other are provided in a direction orthogonal to the length direction of the electrodes 3 and 4. ing.
  • the case where the electrode 3 and the electrode 4 are adjacent to each other does not mean that the electrode 3 and the electrode 4 are arranged so as to be in direct contact with each other, but that the electrode 3 and the electrode 4 are arranged so as to be spaced apart from each other. Point to. Further, when the electrode 3 and the electrode 4 are adjacent to each other, the electrode connected to the hot electrode or the ground electrode, including the other electrode 3 and the electrode 4, is not arranged between the electrode 3 and the electrode 4. This logarithm does not have to be an integer pair, and may be 1.5 pairs, 2.5 pairs, or the like.
  • the distance between the centers between the electrode 3 and the electrode 4, that is, the pitch is preferably in the range of 1 ⁇ m or more and 10 ⁇ m or less.
  • the center-to-center distance between the electrode 3 and the electrode 4 is the center of the width dimension of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the electrode 4 in the direction orthogonal to the length direction of the electrode 4. It is the distance connecting the center of the width dimension of.
  • the electrodes 3 and 4 when there are a plurality of at least one of the electrodes 3 and 4 (when the electrodes 3 and 4 are a pair of electrodes and there are 1.5 or more pairs of electrodes), the electrodes 3 and 4
  • the center-to-center distance refers to the average value of the center-to-center distances of 1.5 pairs or more of the electrodes 3, the adjacent electrodes 3 and the electrodes 4.
  • the width of the electrode 3 and the electrode 4, that is, the dimensions of the electrode 3 and the electrode 4 in the facing direction are preferably in the range of 150 nm or more and 1000 nm or less.
  • the center-to-center distance between the electrode 3 and the electrode 4 is a direction orthogonal to 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 length direction of the electrode 4. It is the distance connected to the center of the dimension (width dimension) of the electrode 4 in.
  • the direction orthogonal to the length direction of the electrodes 3 and 4 is the direction orthogonal to the polarization direction of the piezoelectric layer 2. This does not apply when a piezoelectric material having another cut angle is used as the piezoelectric layer 2.
  • “orthogonal” is not limited to the case of being strictly orthogonal, and is substantially orthogonal (the angle formed by the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, 90 ° ⁇ 10 °). ) May be.
  • a support member 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 via an intermediate layer 7.
  • the intermediate layer 7 and the support member 8 have a frame-like shape and have openings 7a and 8a as shown in FIG. As a result, the cavity 9 (air gap) 9 is formed.
  • the cavity 9 is provided so as not to interfere with 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 via the intermediate layer 7 at a position where the support member 8 does not overlap with the portion where the at least one pair of electrodes 3 and the electrodes 4 are provided.
  • the intermediate layer 7 may not be provided. Therefore, the support member 8 can be directly or indirectly laminated on the second main surface 2b of the piezoelectric layer 2.
  • the intermediate layer 7 is an insulating layer and is made of silicon oxide.
  • the intermediate layer 7 can be formed of an appropriate insulating material such as silicon nitride or alumina in addition to silicon oxide.
  • the support member 8 is also called a support substrate and is made of Si.
  • the plane orientation of Si on the surface of the piezoelectric layer 2 side may be (100), (110), or (111).
  • high resistance Si having a resistivity of 4 k ⁇ or more is desirable.
  • the support member 8 can also be configured by using an appropriate insulating material or semiconductor material.
  • the material of the support member 8 include piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mulite, and steer.
  • Various ceramics such as tight and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.
  • the plurality of electrodes 3, the electrodes 4, the first bus bar 5, and the second bus bar 6 are made of an appropriate metal or alloy such as an Al or AlCu alloy.
  • the electrode 3, the electrode 4, the first bus bar 5, and the second bus bar 6 have a structure in which an Al film is laminated on a Ti film. An adhesive layer other than the Ti film may be used.
  • an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. As a result, it is possible to obtain resonance characteristics using the bulk wave of the thickness slip primary mode excited in the piezoelectric layer 2.
  • the thickness of the piezoelectric layer 2 when the thickness of the piezoelectric layer 2 is d, the distance between the centers of the plurality of pairs of electrodes 3, the adjacent electrodes 3 of the electrodes 4, and the electrodes 4 is p, d / p is It is said to be 0.5 or less. Therefore, the bulk wave in the thickness slip primary mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is 0.24 or less, in which case even better resonance characteristics can be obtained.
  • the electrodes 3 and 4 are 1.5 pairs.
  • the distance p between the centers of 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 first embodiment has the above configuration, the Q value is unlikely to decrease even if the logarithm of the electrodes 3 and 4 is reduced in order to reduce the size. This is because it is a resonator that does not require reflectors on both sides and has little propagation loss. Further, the reason why the above reflector is not required is that the bulk wave of the thickness slip primary mode is used.
  • FIG. 3A is a schematic cross-sectional view for explaining a Lamb wave propagating in the piezoelectric layer of the comparative example.
  • FIG. 3B is a schematic cross-sectional view for explaining the bulk wave of the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment.
  • FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of the bulk wave in the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment.
  • FIG. 3A is an elastic wave device as described in Patent Document 1, in which a ram wave propagates in a piezoelectric layer.
  • the wave propagates in the piezoelectric layer 201 as indicated by an arrow.
  • the piezoelectric layer 201 has a first main surface 201a and a second main surface 201b, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. ..
  • the X direction is the direction in which the electrode fingers of the IDT electrodes are lined up.
  • the wave propagates in the X direction as shown in the figure.
  • the piezoelectric layer 201 vibrates as a whole because it is a plate wave, the wave propagates in the X direction, so reflectors are arranged on both sides to obtain resonance characteristics. Therefore, a wave propagation loss occurs, and the Q value decreases when the size is reduced, that is, when the logarithm of the electrode fingers is reduced.
  • the wave is generated by the first main surface 2a and the second main surface 2a of the piezoelectric layer 2. It propagates substantially in the direction connecting the surface 2b, that is, in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. And since the resonance characteristic is obtained by the propagation of the wave in the Z direction, the reflector is not required. Therefore, there is no propagation loss when propagating to the reflector. Therefore, even if the logarithm of the electrode pair consisting of the electrodes 3 and 4 is reduced in order to promote miniaturization, the Q value is unlikely to decrease.
  • the amplitude directions of the bulk waves in the thickness slip primary mode are the first region 451 included in the excitation region C (see FIG. 1B) of the piezoelectric layer 2 and the first region 451 included in the excitation region C.
  • FIG. 4 schematically shows a bulk wave when a voltage at which the electrode 4 has a higher potential than that of the electrode 3 is applied between the electrode 3 and the electrode 4.
  • the first region 451 is a region of the excitation region C between the virtual plane VP1 orthogonal to the thickness direction of the piezoelectric layer 2 and dividing the piezoelectric layer 2 into two, and the first main surface 2a.
  • 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 electrode 3 and the electrode 4 is arranged, but since the wave is not propagated in the X direction, the logarithm of the electrode pair consisting of the electrode 3 and the electrode 4 Does not necessarily have to be multiple pairs. That is, it is only necessary to provide at least one pair of electrodes.
  • the electrode 3 is an electrode connected to a hot potential
  • the electrode 4 is an electrode connected to a ground potential.
  • the electrode 3 may be connected to the ground potential and the electrode 4 may be connected to the 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 is not provided with a floating electrode.
  • FIG. 5 is an explanatory diagram showing an example of the resonance characteristics of the elastic wave device of the first embodiment.
  • the design parameters of the elastic wave device 1 obtained with the resonance characteristics shown in FIG. 5 are as follows.
  • Piezoelectric layer 2 LiNbO 3 with Euler angles (0 °, 0 °, 90 °) Thickness of piezoelectric layer 2: 400 nm.
  • Excitation region C (see FIG. 1B) length: 40 ⁇ m
  • the logarithm of the electrode consisting of the electrode 3 and the electrode 4 21 pairs
  • the distance (pitch) between the centers between the electrode 3 and the electrode 4 p 3 ⁇ m Width of electrode 3 and electrode 4: 500 nm d / p: 0.133
  • Intermediate layer 7 1 ⁇ m thick silicon oxide film.
  • Support member 8 Si.
  • the excitation region C (see FIG. 1B) is a region where the electrode 3 and the electrode 4 overlap when viewed in the X direction orthogonal to the length direction of the electrode 3 and the electrode 4.
  • the length of the excitation region C is a dimension along the length direction of the electrodes 3 and 4 of the excitation region C.
  • the distance between the electrodes of the electrode pair consisting of the electrodes 3 and 4 is the same for the plurality of pairs. That is, the electrodes 3 and 4 are arranged at equal pitches.
  • d / p is 0.5 or less, more preferably 0.24. It is as follows. This will be described with reference to FIG.
  • FIG. 6 shows d / 2p as a resonator in the elastic wave apparatus of the first embodiment, where p is the center-to-center distance or the average distance between the centers of adjacent electrodes and d is the average thickness of the piezoelectric layer. It is explanatory drawing which shows the relationship with the specific band of.
  • the ratio band is less than 5% even if d / p is adjusted.
  • the specific band can be set to 5% or more by changing d / p within that range. That is, a resonator having a high coupling coefficient can be constructed.
  • the specific band can be increased to 7% or more.
  • d / p is adjusted within this range, a resonator having a wider specific band can be obtained, and a resonator having a higher coupling coefficient can be realized. Therefore, as in the second invention of the present application, by setting d / p to 0.5 or less, it is possible to construct a resonator having a high coupling coefficient using the bulk wave of the thickness slip primary mode. I understand.
  • At least one pair of electrodes may be one pair, and in the case of a pair of electrodes, p is the distance between the centers of the adjacent electrodes 3 and 4. In the case of 1.5 pairs or more of electrodes, the average distance between the centers of the adjacent electrodes 3 and 4 may be p.
  • the thickness d of the piezoelectric layer if the piezoelectric layer 2 has a thickness variation, a value obtained by averaging the thickness may be adopted.
  • FIG. 7 is a plan view showing an example in which a pair of electrodes is provided in the elastic wave device of the first embodiment.
  • a pair of electrodes having an electrode 3 and an electrode 4 is provided on the first main surface 2a of the piezoelectric layer 2.
  • K in FIG. 7 is an intersection width.
  • the logarithm of the electrodes may be one pair. Even in this case, if the d / p is 0.5 or less, the bulk wave in the thickness slip primary mode can be effectively excited.
  • FIG. 8 is a modified example of the first embodiment, and is a cross-sectional view of a portion of FIG. 1A along the line II-II.
  • the acoustic multilayer film 42 is laminated on the second main surface 2b of the piezoelectric layer 2.
  • the acoustic multilayer film 42 has a laminated structure of low acoustic impedance layers 42a, 42c, 42e having a relatively low acoustic impedance and high acoustic impedance layers 42b, 42d having a relatively high acoustic impedance.
  • the bulk wave in the thickness slip primary mode can be confined in the piezoelectric layer 2 without using the cavity 9 in the elastic wave device 1. Even in the elastic wave device 41, by setting the d / p to 0.5 or less, resonance characteristics based on the bulk wave in the thickness slip primary mode can be obtained.
  • the number of layers of the low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b, 42d is not particularly limited. It is sufficient that at least one high acoustic impedance layer 42b, 42d is arranged on the side farther from the piezoelectric layer 2 than the low acoustic impedance layers 42a, 42c, 42e.
  • the low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b, 42d can be made of an appropriate material as long as the relationship of the acoustic impedance is satisfied.
  • the material of the low acoustic impedance layers 42a, 42c, 42e silicon oxide, silicon nitride, or the like can be mentioned.
  • examples of the material of the high acoustic impedance layers 42b and 42d include alumina, silicon nitride, and metal.
  • the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate.
  • the first main surface 2a or the second main surface 2b of the piezoelectric layer 2 has a first electrode 3 and a second electrode 4 facing each other in a direction intersecting with each other in the thickness direction of the piezoelectric layer 2. It is desirable to cover the electrode 3 and the second electrode 4 with a protective film.
  • FIG. 9 is a cross-sectional view of a portion along the IX-IX line of FIG. 1B.
  • the protective film 11 is, for example, silicon oxide.
  • the protective film 11 may be an inorganic insulating film, and may be formed of, for example, silicon nitride.
  • the protective film 11 may be a laminated film in which silicon nitride and silicon oxide are laminated.
  • the protective film 11 is one or more of silicon oxide and silicon nitride.
  • the electrode 3 has a first surface 3U of the electrode 3 and a second surface 3D of the electrode 3 on the opposite side of the first surface 3U of the electrode 3 and on the side of the piezoelectric layer 2. It has a side surface 3SS of the electrode 3.
  • the width of the protective film 11 in the X direction is larger than the width of the electrode 3 in the X direction.
  • the protective film 11 has an end portion 11E of the upper surface 11U of the protective film 11 in the X direction.
  • the distance from the end portion 11E of the upper surface 11U of the protective film 11 to the end portion 11DE of the first surface 3U of the electrode 3 in the X direction is defined as the distance L.
  • the thickness from the first surface 3U of the electrode 3 (lower surface of the protective film 11) to the upper surface 11U of the protective film 11 is defined as the thickness H.
  • the electrode 4 has a first surface 4U of the electrode 4 and a second surface 4D of the electrode 4 on the opposite side of the first surface 4U of the electrode 4 and on the side of the piezoelectric layer 2. It has a side surface 4SS of the electrode 4.
  • the protective film 11 covers the first surface 4U and the side surface 4SS of the electrode 4, the width of the protective film 11 in the X direction is larger than the width of the electrode 4 in the X direction.
  • the protective film 11 has an end portion 11E of the upper surface 11U of the protective film 11 in the X direction.
  • the distance from the end portion 11E of the upper surface 11U of the protective film 11 to the end portion 11DE of the first surface 4U of the electrode 4 in the X direction is defined as the distance L.
  • the thickness from the first surface 4U (lower surface of the protective film 11) of the electrode 4 to the upper surface 11U of the protective film 11 is defined as the thickness H.
  • a value obtained by averaging the distance L may be adopted.
  • a value obtained by averaging the thickness H may be adopted.
  • FIG. 11 is an explanatory diagram for explaining the relationship between the spurious frequency and the resonance frequency.
  • the protective film 11 covers the electrode 3, the electrode 4, and the first main surface 2a of the piezoelectric layer 2. From the above-mentioned distance L and thickness H of the electrode 3 or the electrode 4, the value of L / H on the horizontal axis of FIG. 10 is calculated, and the value of the frequency Fspur / resonance frequency Fr at which spurious is generated for each value of L / H. Is plotted in FIG.
  • the frequency band between the resonance frequency Fr shown in FIG. 11 and the antiresonance frequency Fa is referred to as a pass band. It is desirable that the frequency Fspur at which spurious is generated does not interfere with the pass band.
  • the frequency Fspur in which spurious is generated shown in FIG. 11 is far from the resonance frequency Fr.
  • the resonance frequency Fr and the frequency Fspur in which spurious is generated need to be separated from each other by the resonance frequency Fr [MHz] ⁇ 5% or more. At this time, if Fspur / Fr ⁇ 0.95, spurious is less likely to interfere in the pass band.
  • the L / H is 0.931, the frequency Fspur in which spurious is generated is not in the pass band, and the deterioration of the resonance characteristic is suppressed.
  • the angle ⁇ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 3SS of the electrode 3 is 70 ° or more and 110 ° or less.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 9 and the side surface 3SS of the electrode 3 is 80 °.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 12 and the side surface 3SS of the electrode 3 is 70 °.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 13 and the side surface 3SS of the electrode 3 is 90 °.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 14 and the side surface 3SS of the electrode 3 is 110 °.
  • the angle ⁇ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 4SS of the electrode 4 is 70 ° or more and 110 ° or less.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 9 and the side surface 4SS of the electrode 4 is 80 °.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 12 and the side surface 4SS of the electrode 4 is 70 °.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 13 and the side surface 4SS of the electrode 4 is 90 °.
  • the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 14 and the side surface 4SS of the electrode 4 is 110 °.
  • the elastic wave device 1 faces the piezoelectric layer 2 in the X direction intersecting the Z direction, and at least one pair of electrodes 3 provided adjacent to each other on the first main surface 2a.
  • the electrode 4 is provided with a protective film 11 that covers the first main surface 2a of the piezoelectric layer 2, a pair of electrodes 3, and the electrode 4.
  • Each of the pair of electrodes 3 and 4 is on the opposite side of the first surface 3U and 4U of the electrode 3 and the electrode 4 and the first surface 3U and 4U, and on the second surface 3D on the piezoelectric layer 2 side. It has 4D and.
  • the upper surface 11U of the protective film 11 covering at least one of the electrodes 3 or the first surface 3U and 4U of the electrode 4 is viewed in the Z direction, and the upper surface 11U of the protective film 11 in the X direction.
  • the distance from the end portion 11UE to the end portion 11DE of the first surface 3U or the first surface 4U is L, and the thickness from the first surface 3U or the first surface 4U to the upper surface 11U of the protective film 11 is H.
  • the elastic wave device of the first embodiment satisfies the following formula (1). 0.3 ⁇ L / H ⁇ 1.0 ... (1)
  • the frequency Fspur in which spurious is generated is not in the pass band, and deterioration of resonance characteristics is suppressed.
  • first electrode 3 and the second electrode 4 are adjacent electrodes, and d / p is 0 when the thickness of the piezoelectric layer is d and the distance between the centers of the first electrode and the second electrode is p. It is said to be 5.5 or less. As a result, the elastic wave device can be miniaturized and the Q value can be increased.
  • the elastic wave device satisfies the following formula (2). 0.6 ⁇ L / H ⁇ 1.0 ... (2)
  • the angle ⁇ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 3SS of the electrode 3 is 70 ° or more and 110 ° or less.
  • the angle ⁇ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 4SS of the electrode 4 is 70 ° or more and 110 ° or less. This makes it easier to satisfy the above formula (1) or formula (2).
  • At least one protective film 11 is selected from the group of silicon oxide and silicon nitride. Thereby, the electrode 3, the electrode 4, and the piezoelectric layer 2 can be protected.

Abstract

Provided is an elastic wave device which suppresses a deterioration in resonance characteristics. This elastic wave device comprises a piezoelectric layer, a pair of electrodes, and a protective film. When the upper surface of the protective film which covers a first surface of the electrodes is viewed in a Z-direction, and when L is the distance from an end section of the upper surface of the protective film in an X-direction to an end section of the first surface of each of the electrodes, and H is the thickness from the first surface of each of the electrodes to the upper surface of the protective film, the elastic wave device satisfies the following expression (1).　(1): 0.3≤L/H<1.0

Description

弾性波装置Elastic wave device
　本開示は、ニオブ酸リチウム又はタンタル酸リチウムを含む圧電層を有する弾性波装置に関する。 The present disclosure relates to an elastic wave device having a piezoelectric layer containing lithium niobate or lithium tantalate.
　特許文献１には、弾性波装置が記載されている。 Patent Document 1 describes an elastic wave device.
特開２０１２－２５７０１９号公報Japanese Unexamined Patent Publication No. 2012-257019
　特許文献１記載の弾性波装置の電極を覆うように、保護膜を形成することで、弾性波装置の信頼性を高めることができる。しかしながら、保護膜に起因するスプリアスにより、弾性波装置の共振特性が劣化しやすくなる可能性がある。 By forming a protective film so as to cover the electrodes of the elastic wave device described in Patent Document 1, the reliability of the elastic wave device can be improved. However, spurious caused by the protective film may easily deteriorate the resonance characteristics of the elastic wave device.
　本開示は、上記に鑑みてなされたものであって、共振特性の劣化を抑制する弾性波装置を提供することを目的とする。 The present disclosure has been made in view of the above, and an object of the present disclosure is to provide an elastic wave device that suppresses deterioration of resonance characteristics.
　一態様に係る弾性波装置は、第１の主面と、前記第１の主面の反対側であって、かつ前記第１の主面に対して第１方向にある第２の主面とを有する圧電層と、前記第１方向に交差する第２方向において対向し、前記第１の主面の上に隣り合って設けられた少なくとも１対の電極と、前記圧電層の前記第１の主面と前記１対の電極とを覆う保護膜と、を備え、前記１対の電極のそれぞれは、第１面と、前記第１面と反対側であって、かつ前記圧電層側にある第２面と、を有し、前記１対の電極のうち、少なくとも１つの電極の前記第１面を覆う前記保護膜の上面を前記第１方向にみて、前記第２方向における前記保護膜の上面の端部から前記少なくとも１つの電極の前記第１面の端部までの距離をＬとし、前記少なくとも１つの電極の前記第１面から前記保護膜の上面までの厚みをＨとすると、下記式（１）を満たす。
　０．３≦Ｌ／Ｈ＜１．０　・・・　（１） The elastic wave device according to one embodiment has a first main surface and a second main surface opposite to the first main surface and in a first direction with respect to the first main surface. At least one pair of electrodes facing each other in the second direction intersecting the first direction and adjacently provided on the first main surface, and the first pair of electrodes of the piezoelectric layer. A protective film covering the main surface and the pair of electrodes is provided, and each of the pair of electrodes is on the first surface and the side opposite to the first surface and on the piezoelectric layer side. The protective film has a second surface, and the upper surface of the protective film covering the first surface of at least one of the pair of electrodes is viewed in the first direction, and the protective film in the second direction. Let L be the distance from the end of the upper surface to the end of the first surface of the at least one electrode, and H be the thickness of the at least one electrode from the first surface to the upper surface of the protective film. Equation (1) is satisfied.
0.3 ≤ L / H <1.0 ... (1)
　本開示によれば、共振特性の劣化を抑制することが可能となる。 According to the present disclosure, it is possible to suppress deterioration of resonance characteristics.
図１Ａは、第１実施形態の弾性波装置を示す斜視図である。FIG. 1A is a perspective view showing an elastic wave device of the first embodiment. 図１Ｂは、第１実施形態の電極構造を示す平面図である。FIG. 1B is a plan view showing the electrode structure of the first embodiment. 図２は、図１ＡのＩＩ－ＩＩ線に沿う部分の断面図である。FIG. 2 is a cross-sectional view of a portion of FIG. 1A along line II-II. 図３Ａは、比較例の圧電層を伝播するラム波を説明するための模式的な断面図である。FIG. 3A is a schematic cross-sectional view for explaining a Lamb wave propagating in the piezoelectric layer of the comparative example. 図３Ｂは、第１実施形態の圧電層を伝播する厚み滑り１次モードのバルク波を説明するための模式的な断面図である。FIG. 3B is a schematic cross-sectional view for explaining the bulk wave of the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment. 図４は、第１実施形態の圧電層を伝播する厚み滑り１次モードのバルク波の振幅方向を説明するための模式的な断面図である。FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of the bulk wave in the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment. 図５は、第１実施形態の弾性波装置の共振特性の例を示す説明図である。FIG. 5 is an explanatory diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment. 図６は、第１実施形態の弾性波装置において、隣り合う電極の中心間距離又は中心間距離の平均距離をｐ、圧電層の平均厚みをｄとした場合、ｄ／２ｐと、共振子としての比帯域との関係を示す説明図である。FIG. 6 shows d / 2p as a resonator in the elastic wave apparatus of the first embodiment, where p is the center-to-center distance or the average distance between the centers of adjacent electrodes and d is the average thickness of the piezoelectric layer. It is explanatory drawing which shows the relationship with the specific band of. 図７は、第１実施形態の弾性波装置において、１対の電極が設けられている例を示す平面図である。FIG. 7 is a plan view showing an example in which a pair of electrodes is provided in the elastic wave device of the first embodiment. 図８は、第１実施形態の変形例であって、図１ＡのＩＩ－ＩＩ線に沿う部分の断面図である。FIG. 8 is a modification of the first embodiment, and is a cross-sectional view of a portion of FIG. 1A along the line II-II. 図９は、図１ＢのＩＸ－ＩＸ線に沿う部分の断面図である。FIG. 9 is a cross-sectional view of a portion of FIG. 1B along the IX-IX line. 図１０は、保護膜とスプリアスとの関係を説明するための説明図である。FIG. 10 is an explanatory diagram for explaining the relationship between the protective film and spurious. 図１１は、スプリアスの周波数と共振周波数との関係を説明するための説明図である。FIG. 11 is an explanatory diagram for explaining the relationship between the spurious frequency and the resonance frequency. 図１２は、図１ＢのＩＸ－ＩＸ線に沿う部分の他の例の断面図である。FIG. 12 is a cross-sectional view of another example of the portion along the IX-IX line of FIG. 1B. 図１３は、図１ＢのＩＸ－ＩＸ線に沿う部分の他の例の断面図である。FIG. 13 is a cross-sectional view of another example of the portion along the IX-IX line of FIG. 1B. 図１４は、図１ＢのＩＸ－ＩＸ線に沿う部分の他の例の断面図である。FIG. 14 is a cross-sectional view of another example of the portion along the IX-IX line of FIG. 1B.
　以下に、本開示の実施の形態を図面に基づいて詳細に説明する。なお、この実施の形態により本開示が限定されるものではない。なお、本開示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又は組み合わせが可能である変形例や第２実施の形態以降では第１の実施形態と共通の事柄についての記述を省略し、異なる点についてのみ説明する。特に、同様の構成による同様の作用効果については実施形態毎には逐次言及しない。 Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to this embodiment. It should be noted that each embodiment described in the present disclosure is an exemplary example, and the first embodiment is described in a modified example in which the configurations can be partially replaced or combined between different embodiments, and in the second and subsequent embodiments. The description of the matters common to the embodiment will be omitted, and only the differences will be described. In particular, the same action and effect due to the same configuration will not be mentioned sequentially for each embodiment.
（第１実施形態）
　図１Ａは、第１実施形態の弾性波装置を示す斜視図である。図１Ｂは、第１実施形態の電極構造を示す平面図である。 (First Embodiment)
FIG. 1A is a perspective view showing an elastic wave device of the first embodiment. FIG. 1B is a plan view showing the electrode structure of the first embodiment.
　第１実施形態の弾性波装置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、第１実施形態では、Ｚカットである。ＬｉＮｂＯ３やＬｉＴａＯ３のカット角は、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。 The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 made of LiNbO 3 . The piezoelectric layer 2 may be made of LiTaO 3 . The cut angle of LiNbO 3 and LiTaO 3 is Z-cut in the first embodiment. The cut angle of LiNbO 3 or LiTaO 3 may be a rotary Y cut or an X cut. Propagation directions of Y propagation and X propagation ± 30 ° are preferable.
　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 thickness of the piezoelectric layer 2 is not particularly limited, but is preferably 50 nm or more and 1000 nm or less in order to effectively excite the thickness slip primary mode.
　圧電層２は、Ｚ方向に対向し合う第１の主面２ａと、第２の主面２ｂとを有する。第１の主面２ａ上に、電極３及び電極４が設けられている。 The piezoelectric layer 2 has a first main surface 2a facing each other in the Z direction and a second main surface 2b. The electrode 3 and the electrode 4 are provided on the first main surface 2a.
　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。複数の電極４は、第２のバスバー６に接続されている。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。 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, a plurality of electrodes 3 are connected to the first bus bar 5. The plurality of electrodes 4 are 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、電極３と隣接する電極４とが対向している。電極３、電極４の長さ方向、及び、電極３、電極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、電極３と隣接する電極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。第１実施形態では、圧電層２の厚み方向をＺ方向（又は第１方向）とし、電極３、電極４の長さ方向と直交する方向をＸ方向（又は第２方向）とし、電極３、電極４の長さ方向をＹ方向（又は第３方向）として、説明することがある。 The electrode 3 and the electrode 4 have a rectangular shape and have a length direction. The electrode 3 and the electrode 4 adjacent to the electrode 3 face each other in a direction orthogonal to the length direction. The length direction of the electrode 3 and the electrode 4 and the direction orthogonal to the length direction of the electrode 3 and the electrode 4 are all directions intersecting with each other in the thickness direction of the piezoelectric layer 2. Therefore, it can be said that the electrode 3 and the electrode 4 adjacent to the electrode 3 face each other in a direction intersecting with each other in the thickness direction of the piezoelectric layer 2. In the first embodiment, the thickness direction of the piezoelectric layer 2 is the Z direction (or the first direction), the direction orthogonal to the length direction of the electrode 3 and the electrode 4 is the X direction (or the second direction), and the electrode 3. The length direction of the electrode 4 may be described as the Y direction (or the third direction).
　また、電極３、電極４の長さ方向が図１Ａ及び図１Ｂに示す電極３、電極４の長さ方向に直交する方向と入れ替わっても良い。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、電極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、電極４が延びている方向に延びることとなる。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、電極４の長さ方向と直交する方向に、複数対設けられている。 Further, the length directions of the electrodes 3 and 4 may be replaced with the directions orthogonal to the length directions 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 be extended in the direction in which the first bus bar 5 and the second bus bar 6 are extended. In that case, the first bus bar 5 and the second bus bar 6 extend in the direction in which the electrodes 3 and 4 extend in FIGS. 1A and 1B. Then, a plurality of pairs of structures in which the electrode 3 connected to one potential and the electrode 4 connected to the other potential are adjacent to each other are provided in a direction orthogonal to the length direction of the electrodes 3 and 4. ing.
　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。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、電極４を含む、ホット電極やグラウ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。 Here, the case where the electrode 3 and the electrode 4 are adjacent to each other does not mean that the electrode 3 and the electrode 4 are arranged so as to be in direct contact with each other, but that the electrode 3 and the electrode 4 are arranged so as to be spaced apart from each other. Point to. Further, when the electrode 3 and the electrode 4 are adjacent to each other, the electrode connected to the hot electrode or the ground electrode, including the other electrode 3 and the electrode 4, is not arranged between the electrode 3 and the electrode 4. This logarithm does not have to be an integer pair, and may be 1.5 pairs, 2.5 pairs, or the like.
　電極３と電極４との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と電極４との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。 The distance between the centers between the electrode 3 and the electrode 4, that is, the pitch is preferably in the range of 1 μm or more and 10 μm or less. Further, the center-to-center distance between the electrode 3 and the electrode 4 is the center of the width dimension of the electrode 3 in the direction orthogonal to the length direction of the electrode 3 and the electrode 4 in the direction orthogonal to the length direction of the electrode 4. It is the distance connecting the center of the width dimension of.
　さらに、電極３、電極４の少なくとも一方が複数本ある場合（電極３、電極４を一対の電極組とした場合に、１．５対以上の電極組がある場合）、電極３、電極４の中心間距離は、１．５対以上の電極３、電極４のうち隣り合う電極３、電極４それぞれの中心間距離の平均値を指す。 Further, when there are a plurality of at least one of the electrodes 3 and 4 (when the electrodes 3 and 4 are a pair of electrodes and there are 1.5 or more pairs of electrodes), the electrodes 3 and 4 The center-to-center distance refers to the average value of the center-to-center distances of 1.5 pairs or more of the electrodes 3, the adjacent electrodes 3 and the electrodes 4.
　また、電極３、電極４の幅、すなわち電極３、電極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と電極４との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。 Further, the width of the electrode 3 and the electrode 4, that is, the dimensions of the electrode 3 and the electrode 4 in the facing direction are preferably in the range of 150 nm or more and 1000 nm or less. The center-to-center distance between the electrode 3 and the electrode 4 is a direction orthogonal to 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 length direction of the electrode 4. It is the distance connected to the center of the dimension (width dimension) of the electrode 4 in.
　また、第１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、電極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、電極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。 Further, in the first embodiment, since the Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrodes 3 and 4 is the direction orthogonal to the polarization direction of the piezoelectric layer 2. This does not apply when a piezoelectric material having another cut angle is used as the piezoelectric layer 2. Here, "orthogonal" is not limited to the case of being strictly orthogonal, and is substantially orthogonal (the angle formed by the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, 90 ° ± 10 °). ) May be.
　圧電層２の第２の主面２ｂ側には、中間層７を介して支持部材８が積層されている。中間層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（エアギャップ）９が形成されている。 A support member 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 via an intermediate layer 7. The intermediate layer 7 and the support member 8 have a frame-like shape and have openings 7a and 8a as shown in FIG. As a result, the cavity 9 (air gap) 9 is formed.
　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、電極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に中間層７を介して積層されている。なお、中間層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に直接又は間接に積層され得る。 The cavity 9 is provided so as not to interfere with 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 via the intermediate layer 7 at a position where the support member 8 does not overlap with the portion where the at least one pair of electrodes 3 and the electrodes 4 are provided. The intermediate layer 7 may not be provided. Therefore, the support member 8 can be directly or indirectly laminated on the second main surface 2b of the piezoelectric layer 2.
　中間層７は、絶縁層であり、酸化ケイ素で形成されている。もっとも、中間層７は、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で形成することができる。 The intermediate layer 7 is an insulating layer and is made of silicon oxide. However, the intermediate layer 7 can be formed of an appropriate insulating material such as silicon nitride or alumina in addition to silicon oxide.
　支持部材８は、支持基板ともいい、Ｓｉで形成されている。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 support member 8 is also called a support substrate and is made of Si. The plane orientation of Si on the surface of 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 support member 8 can also be configured by using an appropriate insulating material or semiconductor material. Examples of the material of the support member 8 include piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mulite, and steer. Various ceramics such as tight and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.
　上記複数の電極３、電極４及び第１のバスバー５、第２のバスバー６は、Ａｌ、ＡｌＣｕ合金などの適宜の金属もしくは合金からなる。第１実施形態では、電極３、電極４及び第１のバスバー５、第２のバスバー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, the electrodes 4, the first bus bar 5, and the second bus bar 6 are made of an appropriate metal or alloy such as an Al or AlCu alloy. In the first embodiment, the electrode 3, the electrode 4, the first bus bar 5, and the second bus bar 6 have a structure in which an Al film is laminated on a Ti film. An adhesive 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 plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. As a result, it is possible to obtain resonance characteristics using the bulk wave of the thickness slip primary mode 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、電極４のうちいずれかの隣り合う電極３、電極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。 Further, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is d, the distance between the centers of the plurality of pairs of electrodes 3, the adjacent electrodes 3 of the electrodes 4, and the electrodes 4 is p, d / p is It is said to be 0.5 or less. Therefore, the bulk wave in the thickness slip primary mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is 0.24 or less, in which case even better resonance characteristics can be obtained.
　なお、第１実施形態のように電極３、電極４の少なくとも一方が複数本ある場合、すなわち、電極３、電極４を１対の電極組とした場合に電極３、電極４が１．５対以上ある場合、隣り合う電極３、電極４の中心間距離ｐは、各隣り合う電極３、電極４の中心間距離の平均距離となる。 When there are a plurality of at least one of the electrodes 3 and 4 as in the first embodiment, that is, when the electrodes 3 and 4 are paired as a pair of electrodes, the electrodes 3 and 4 are 1.5 pairs. In the above case, the distance p between the centers of the adjacent electrodes 3 and 4 is the average distance between the centers of the adjacent electrodes 3 and 4.
　第１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、電極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 first embodiment has the above configuration, the Q value is unlikely to decrease even if the logarithm of the electrodes 3 and 4 is reduced in order to reduce the size. This is because it is a resonator that does not require reflectors on both sides and has little propagation loss. Further, the reason why the above reflector is not required is that the bulk wave of the thickness slip primary mode is used.
　図３Ａは、比較例の圧電層を伝播するラム波を説明するための模式的な断面図である。図３Ｂは、第１実施形態の圧電層を伝播する厚み滑り１次モードのバルク波を説明するための模式的な断面図である。図４は、第１実施形態の圧電層を伝播する厚み滑り１次モードのバルク波の振幅方向を説明するための模式的な断面図である。 FIG. 3A is a schematic cross-sectional view for explaining a Lamb wave propagating in the piezoelectric layer of the comparative example. FIG. 3B is a schematic cross-sectional view for explaining the bulk wave of the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment. FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of the bulk wave in the thickness slip primary mode propagating through the piezoelectric layer of the first embodiment.
　図３Ａでは、特許文献１に記載のような弾性波装置であり、圧電層をラム波が伝搬する。図３Ａに示すように、圧電層２０１中を矢印で示すように波が伝搬する。ここで、圧電層２０１には、第１の主面２０１ａと、第２の主面２０１ｂとがあり、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、圧電層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 an elastic wave device as described in Patent Document 1, in which a ram wave propagates in a piezoelectric layer. As shown in FIG. 3A, the wave propagates in the piezoelectric layer 201 as indicated by an arrow. Here, the piezoelectric layer 201 has a first main surface 201a and a second main surface 201b, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. .. The X direction is the direction in which the electrode fingers of the IDT electrodes are lined up. As shown in FIG. 3A, in a Lamb wave, the wave propagates in the X direction as shown in the figure. Since the piezoelectric layer 201 vibrates as a whole because it is a plate wave, the wave propagates in the X direction, so reflectors are arranged on both sides to obtain resonance characteristics. Therefore, a wave propagation loss occurs, and the Q value decreases when the size is reduced, that is, when the logarithm of the electrode fingers is reduced.
　これに対して、図３Ｂに示すように、第１実施形態の弾性波装置では、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、電極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 elastic wave device of the first embodiment, since the vibration displacement is in the thickness sliding direction, the wave is generated by the first main surface 2a and the second main surface 2a of the piezoelectric layer 2. It propagates substantially in the direction connecting the surface 2b, that is, in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. And since the resonance characteristic is obtained by the propagation of the wave in the Z direction, the reflector is not required. Therefore, there is no propagation loss when propagating to the reflector. Therefore, even if the logarithm of the electrode pair consisting of the electrodes 3 and 4 is reduced in order 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（図１Ｂ参照）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では、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ある。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。 As shown in FIG. 4, the amplitude directions of the bulk waves in the thickness slip primary mode are the first region 451 included in the excitation region C (see FIG. 1B) of the piezoelectric layer 2 and the first region 451 included in the excitation region C. The opposite is true for the two regions 452. FIG. 4 schematically shows a bulk wave when a voltage at which the electrode 4 has a higher potential than that of the electrode 3 is applied between the electrode 3 and the electrode 4. The first region 451 is a region of the excitation region C between the virtual plane VP1 orthogonal to the thickness direction of the piezoelectric layer 2 and dividing the piezoelectric layer 2 into two, and the first main surface 2a. The second region 452 is a region of the excitation region C between the virtual plane VP1 and the second main surface 2b.
　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、電極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。 In the elastic wave device 1, at least one pair of electrodes consisting of the electrode 3 and the electrode 4 is arranged, but since the wave is not propagated in the X direction, the logarithm of the electrode pair consisting of the electrode 3 and the electrode 4 Does not necessarily have to be multiple pairs. That is, it is only necessary to provide at least one pair of electrodes.
　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。第１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又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, the electrode 3 may be connected to the ground potential and the electrode 4 may be connected to the hot potential. In the first 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 is not provided with a floating electrode.
　図５は、第１実施形態の弾性波装置の共振特性の例を示す説明図である。なお、図５に示す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。 FIG. 5 is an explanatory diagram showing an example of the resonance characteristics of the elastic wave device of the first embodiment. The design parameters of the elastic wave device 1 obtained with the resonance characteristics shown in FIG. 5 are as follows.
　圧電層２：オイラー角（０°，０°，９０°）のＬｉＮｂＯ３
　圧電層２の厚み：４００ｎｍ。 Piezoelectric layer 2: LiNbO 3 with Euler angles (0 °, 0 °, 90 °)
Thickness of piezoelectric layer 2: 400 nm.
　励振領域Ｃ（図１Ｂ参照）の長さ：４０μｍ
　電極３、電極４からなる電極の対数：２１対
　電極３と電極４との間の中心間距離（ピッチ）ｐ：３μｍ
　電極３、電極４の幅：５００ｎｍ
　ｄ／ｐ：０．１３３ Excitation region C (see FIG. 1B) length: 40 μm
The logarithm of the electrode consisting of the electrode 3 and the electrode 4: 21 pairs The distance (pitch) between the centers between the electrode 3 and the electrode 4 p: 3 μm
Width of electrode 3 and electrode 4: 500 nm
d / p: 0.133
　中間層７：１μｍの厚みの酸化ケイ素膜。 Intermediate layer 7: 1 μm thick silicon oxide film.
　支持部材８：Ｓｉ。 Support member 8: Si.
　なお、励振領域Ｃ（図１Ｂ参照）とは、電極３と電極４の長さ方向と直交するＸ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である。励振領域Ｃの長さとは、励振領域Ｃの電極３、電極４の長さ方向に沿う寸法である。 The excitation region C (see FIG. 1B) is a region where the electrode 3 and the electrode 4 overlap when viewed in the X direction orthogonal to the length direction of the electrode 3 and the electrode 4. The length of the excitation region C is a dimension along the length direction of the electrodes 3 and 4 of the excitation region C.
　第１実施形態では、電極３、電極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 the first embodiment, the distance between the electrodes of the electrode pair consisting of the electrodes 3 and 4 is the same for the plurality of pairs. That is, the electrodes 3 and 4 are 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 band of 12.5% are obtained even though the reflector is not provided.
　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、第１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 first embodiment, d / p is 0.5 or less, more preferably 0.24. It is as follows. This will be described 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、第１実施形態の弾性波装置において、隣り合う電極の中心間距離又は中心間距離の平均距離をｐ、圧電層の平均厚みをｄとした場合、ｄ／２ｐと、共振子としての比帯域との関係を示す説明図である。 Similar to the elastic wave device that obtained the resonance characteristics shown in FIG. 5, however, d / 2p was changed to obtain a plurality of elastic wave devices. FIG. 6 shows d / 2p as a resonator in the elastic wave apparatus of the first embodiment, where p is the center-to-center distance or the average distance between the centers of adjacent electrodes and d is the average thickness of the piezoelectric layer. It is explanatory drawing which shows the relationship with the specific band of.
　図６に示すように、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、本願の第２の発明のように、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 shown in FIG. 6, when d / 2p exceeds 0.25, that is, when d / p> 0.5, the ratio band is less than 5% even if d / p is adjusted. On the other hand, in the case of d / 2p ≦ 0.25, that is, d / p ≦ 0.5, the specific band can be set 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 band can be increased to 7% or more. In addition, if d / p is adjusted within this range, a resonator having a wider specific band can be obtained, and a resonator having a higher coupling coefficient can be realized. Therefore, as in the second invention of the present application, by setting d / p to 0.5 or less, it is possible to construct a resonator having a high coupling coefficient using the bulk wave of the thickness slip primary mode. I understand.
　なお、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、電極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、電極４の中心間距離の平均距離をｐとすればよい。 Note that at least one pair of electrodes may be one pair, and in the case of a pair of electrodes, p is the distance between the centers of the adjacent electrodes 3 and 4. In the case of 1.5 pairs or more of electrodes, the average distance between the centers of the adjacent electrodes 3 and 4 may 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。 Further, as for the thickness d of the piezoelectric layer, if the piezoelectric layer 2 has a thickness variation, a value obtained by averaging the thickness may be adopted.
　図７は、第１実施形態の弾性波装置において、１対の電極が設けられている例を示す平面図である。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 showing an example in which a pair of electrodes is provided in the elastic wave device of the first embodiment. In the elastic wave device 31, a pair of electrodes having an electrode 3 and an electrode 4 is provided on the first main surface 2a of the piezoelectric layer 2. In addition, K in FIG. 7 is an intersection width. As described above, in the elastic wave device of the present disclosure, the logarithm of the electrodes may be one pair. Even in this case, if the d / p is 0.5 or less, the bulk wave in the thickness slip primary mode can be effectively excited.
　図８は、第１実施形態の変形例であって、図１ＡのＩＩ－ＩＩ線に沿う部分の断面図である。弾性波装置４１では、圧電層２の第２の主面２ｂに音響多層膜４２が積層されている。音響多層膜４２は、音響インピーダンスが相対的に低い低音響インピーダンス層４２ａ、４２ｃ、４２ｅと、音響インピーダンスが相対的に高い高音響インピーダンス層４２ｂ、４２ｄとの積層構造を有する。音響多層膜４２を用いた場合、弾性波装置１における空洞部９を用いずとも、厚み滑り１次モードのバルク波を圧電層２内に閉じ込めることができる。弾性波装置４１においても、上記ｄ／ｐを０．５以下とすることにより、厚み滑り１次モードのバルク波に基づく共振特性を得ることができる。なお、音響多層膜４２においては、その低音響インピーダンス層４２ａ、４２ｃ、４２ｅ及び高音響インピーダンス層４２ｂ、４２ｄの積層数は特に限定されない。低音響インピーダンス層４２ａ、４２ｃ、４２ｅよりも、少なくとも１層の高音響インピーダンス層４２ｂ、４２ｄが圧電層２から遠い側に配置されておりさえすればよい。 FIG. 8 is a modified example of the first embodiment, and is a cross-sectional view of a portion of FIG. 1A along the line II-II. In the elastic wave device 41, the acoustic multilayer film 42 is laminated on the second main surface 2b of the piezoelectric layer 2. The acoustic multilayer film 42 has a laminated structure of low acoustic impedance layers 42a, 42c, 42e having a relatively low acoustic impedance and high acoustic impedance layers 42b, 42d having a relatively high acoustic impedance. When the acoustic multilayer film 42 is used, the bulk wave in the thickness slip primary mode can be confined in the piezoelectric layer 2 without using the cavity 9 in the elastic wave device 1. Even in the elastic wave device 41, by setting the d / p to 0.5 or less, resonance characteristics based on the bulk wave in the thickness slip primary mode can be obtained. In the acoustic multilayer film 42, the number of layers of the low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b, 42d is not particularly limited. It is sufficient that at least one high acoustic impedance layer 42b, 42d is arranged on the side farther from the piezoelectric layer 2 than the low acoustic impedance layers 42a, 42c, 42e.
　上記低音響インピーダンス層４２ａ、４２ｃ、４２ｅ及び高音響インピーダンス層４２ｂ、４２ｄは、上記音響インピーダンスの関係を満たす限り、適宜の材料で構成することができる。例えば、低音響インピーダンス層４２ａ、４２ｃ、４２ｅの材料としては、酸化ケイ素又は酸窒化ケイ素などを挙げることができる。また、高音響インピーダンス層４２ｂ、４２ｄの材料としては、アルミナ、窒化ケイ素又は金属などを挙げることができる。 The low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b, 42d can be made of an appropriate material as long as the relationship of the acoustic impedance is satisfied. For example, as the material of the low acoustic impedance layers 42a, 42c, 42e, silicon oxide, silicon nitride, or the like can be mentioned. Further, examples of the material of the high acoustic impedance layers 42b and 42d include alumina, silicon nitride, and metal.
　実施形態１及び実施形態１の変形例の弾性波装置１、３１、４１では、圧電層２がニオブ酸リチウム又はタンタル酸リチウムで形成されている。圧電層２の第１の主面２ａ又は第２の主面２ｂには、圧電層２の厚み方向に交差する方向において対向する第１の電極３及び第２の電極４があり、第１の電極３及び第２の電極４の上を保護膜で覆うことが望ましい。 In the elastic wave devices 1, 31, and 41 of the first embodiment and the modified examples of the first embodiment, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. The first main surface 2a or the second main surface 2b of the piezoelectric layer 2 has a first electrode 3 and a second electrode 4 facing each other in a direction intersecting with each other in the thickness direction of the piezoelectric layer 2. It is desirable to cover the electrode 3 and the second electrode 4 with a protective film.
　図９は、図１ＢのＩＸ－ＩＸ線に沿う部分の断面図である。 FIG. 9 is a cross-sectional view of a portion along the IX-IX line of FIG. 1B.
　保護膜１１は、例えば酸化ケイ素である。保護膜１１は、無機絶縁膜であればよく、例えば、窒化ケイ素で形成されてもよい。保護膜１１は、窒化ケイ素と酸化ケイ素が積層された積層膜であってもよい。保護膜１１は、酸化ケイ素及び窒化ケイ素のいずれか１以上である。 The protective film 11 is, for example, silicon oxide. The protective film 11 may be an inorganic insulating film, and may be formed of, for example, silicon nitride. The protective film 11 may be a laminated film in which silicon nitride and silicon oxide are laminated. The protective film 11 is one or more of silicon oxide and silicon nitride.
　図９に示すように、電極３は、電極３の第１面３Ｕと、電極３の第１面３Ｕと反対側であって、かつ圧電層２側にある電極３の第２面３Ｄと、電極３の側面３ＳＳとを有している。 As shown in FIG. 9, the electrode 3 has a first surface 3U of the electrode 3 and a second surface 3D of the electrode 3 on the opposite side of the first surface 3U of the electrode 3 and on the side of the piezoelectric layer 2. It has a side surface 3SS of the electrode 3.
　保護膜１１は、電極３の第１面３Ｕ及び側面３ＳＳを覆うので、保護膜１１のＸ方向の幅が電極３のＸ方向の幅よりも大きくなる。これにより、保護膜１１の上面１１ＵをＺ方向にみて、保護膜１１には、Ｘ方向における保護膜１１の上面１１Ｕの端部１１Ｅがある。また、保護膜１１の上面１１Ｕの端部１１ＥからＸ方向における電極３の第１面３Ｕの端部１１ＤＥまでの距離を距離Ｌとする。電極３の第１面３Ｕ（保護膜１１の下面）から保護膜１１の上面１１Ｕまでの厚みを厚みＨとする。 Since the protective film 11 covers the first surface 3U and the side surface 3SS of the electrode 3, the width of the protective film 11 in the X direction is larger than the width of the electrode 3 in the X direction. As a result, when the upper surface 11U of the protective film 11 is viewed in the Z direction, the protective film 11 has an end portion 11E of the upper surface 11U of the protective film 11 in the X direction. Further, the distance from the end portion 11E of the upper surface 11U of the protective film 11 to the end portion 11DE of the first surface 3U of the electrode 3 in the X direction is defined as the distance L. The thickness from the first surface 3U of the electrode 3 (lower surface of the protective film 11) to the upper surface 11U of the protective film 11 is defined as the thickness H.
　図９に示すように、電極４は、電極４の第１面４Ｕと、電極４の第１面４Ｕと反対側であって、かつ圧電層２側にある電極４の第２面４Ｄと、電極４の側面４ＳＳとを有している。 As shown in FIG. 9, the electrode 4 has a first surface 4U of the electrode 4 and a second surface 4D of the electrode 4 on the opposite side of the first surface 4U of the electrode 4 and on the side of the piezoelectric layer 2. It has a side surface 4SS of the electrode 4.
　保護膜１１は、電極４の第１面４Ｕ及び側面４ＳＳを覆うので、保護膜１１のＸ方向の幅が電極４のＸ方向の幅よりも大きくなる。これにより、保護膜１１の上面１１ＵをＺ方向にみて、保護膜１１には、Ｘ方向における保護膜１１の上面１１Ｕの端部１１Ｅがある。また、保護膜１１の上面１１Ｕの端部１１ＥからＸ方向における電極４の第１面４Ｕの端部１１ＤＥまでの距離を距離Ｌとする。電極４の第１面４Ｕ（保護膜１１の下面）から保護膜１１の上面１１Ｕまでの厚みを厚みＨとする。 Since the protective film 11 covers the first surface 4U and the side surface 4SS of the electrode 4, the width of the protective film 11 in the X direction is larger than the width of the electrode 4 in the X direction. As a result, when the upper surface 11U of the protective film 11 is viewed in the Z direction, the protective film 11 has an end portion 11E of the upper surface 11U of the protective film 11 in the X direction. Further, the distance from the end portion 11E of the upper surface 11U of the protective film 11 to the end portion 11DE of the first surface 4U of the electrode 4 in the X direction is defined as the distance L. The thickness from the first surface 4U (lower surface of the protective film 11) of the electrode 4 to the upper surface 11U of the protective film 11 is defined as the thickness H.
　なお、距離Ｌがばらつきを有する場合、その距離Ｌを平均化した値を採用すればよい。同様に、厚みＨがばらつきを有する場合、その厚みＨを平均化した値を採用すればよい。 If the distance L has a variation, a value obtained by averaging the distance L may be adopted. Similarly, when the thickness H has a variation, a value obtained by averaging the thickness H may be adopted.
　図１１は、スプリアスの周波数と共振周波数との関係を説明するための説明図である。図９に示すように、保護膜１１は、電極３、電極４及び圧電層２の第１の主面２ａを覆っている。電極３又は電極４の上述した距離Ｌと厚みＨとから、図１０の横軸のＬ／Ｈの値を算出し、Ｌ／Ｈの値毎のスプリアスが発生する周波数Ｆｓｐｕｒ／共振周波数Ｆｒの値を図１０にプロットしている。ここで、図１１に示す共振周波数Ｆｒと、反共振周波数Ｆａとの間の周波数帯域を通過帯域という。スプリアスが発生する周波数Ｆｓｐｕｒは、通過帯域に干渉しないことが望ましい。 FIG. 11 is an explanatory diagram for explaining the relationship between the spurious frequency and the resonance frequency. As shown in FIG. 9, the protective film 11 covers the electrode 3, the electrode 4, and the first main surface 2a of the piezoelectric layer 2. From the above-mentioned distance L and thickness H of the electrode 3 or the electrode 4, the value of L / H on the horizontal axis of FIG. 10 is calculated, and the value of the frequency Fspur / resonance frequency Fr at which spurious is generated for each value of L / H. Is plotted in FIG. Here, the frequency band between the resonance frequency Fr shown in FIG. 11 and the antiresonance frequency Fa is referred to as a pass band. It is desirable that the frequency Fspur at which spurious is generated does not interfere with the pass band.
　このため、図１１に示すスプリアスが発生する周波数Ｆｓｐｕｒは、共振周波数Ｆｒから離れていることがより望ましい。スプリアスが通過帯域内に干渉しないために、本発明者は、共振周波数Ｆｒと、スプリアスが発生する周波数Ｆｓｐｕｒとの間を共振周波数Ｆｒ［ＭＨｚ］×５％以上離す必要があることを見いだした。このとき、Ｆｓｐｕｒ／Ｆｒ≦０．９５であれば、スプリアスが通過帯域内に干渉しにくくなる。 Therefore, it is more desirable that the frequency Fspur in which spurious is generated shown in FIG. 11 is far from the resonance frequency Fr. In order for spurious to not interfere in the pass band, the present inventor has found that the resonance frequency Fr and the frequency Fspur in which spurious is generated need to be separated from each other by the resonance frequency Fr [MHz] × 5% or more. At this time, if Fspur / Fr ≦ 0.95, spurious is less likely to interfere in the pass band.
　シミュレーションの条件は以下の通りであり、評価結果が図１０に示されている。
　電極３と電極４との間の中心間距離（ピッチ）：４．２μｍ
　電極３の第２面３Ｄ及び電極４の第２面４Ｄの各Ｘ方向幅：０．９μｍ
　電極３及び電極４の各膜厚：０．５μｍ
　圧電層の膜厚：０．４μｍ
　電極３及び電極４の材料：Ａｌ
　圧電層のカット角：Ｚカット
　保護膜の材料：二酸化ケイ素
　保護膜の厚みＨ：１２０ｎｍ
　距離Ｌ：１２ｎｍ以上１０８ｎｍ以下 The conditions of the simulation are as follows, and the evaluation results are shown in FIG.
Center-to-center distance (pitch) between electrode 3 and electrode 4: 4.2 μm
Width of each of the second surface 3D of the electrode 3 and the second surface 4D of the electrode 4 in the X direction: 0.9 μm
Film thickness of electrode 3 and electrode 4: 0.5 μm
Piezoelectric layer film thickness: 0.4 μm
Material of electrode 3 and electrode 4: Al
Piezoelectric layer cut angle: Z cut Protective film material: Silicon dioxide Protective film thickness H: 120 nm
Distance L: 12 nm or more and 108 nm or less
　図１０に示すように、Ｆｓｐｕｒ／Ｆｒ≦０．９５を満たすためには、下記（１）を満たす必要がある。
　０．３≦Ｌ／Ｈ＜１．０　・・・　（１） As shown in FIG. 10, in order to satisfy Fspur / Fr ≦ 0.95, it is necessary to satisfy the following (1).
0.3 ≤ L / H <1.0 ... (1)
　これにより、スプリアスが通過帯域内に干渉しにくくなる。例えば、図１１に示す共振特性では、Ｌ／Ｈが０．９３１であり、スプリアスが発生する周波数Ｆｓｐｕｒは、通過帯域になく、共振特性の劣化が抑制されている。 This makes it difficult for spurious to interfere in the passband. For example, in the resonance characteristic shown in FIG. 11, the L / H is 0.931, the frequency Fspur in which spurious is generated is not in the pass band, and the deterioration of the resonance characteristic is suppressed.
　図１０に示すように、Ｆｓｐｕｒ／Ｆｒ≦０．９３５を満たすためには、下記（２）を満たす必要がある。
　０．６≦Ｌ／Ｈ＜１．０　・・・　（２） As shown in FIG. 10, in order to satisfy Fspur / Fr ≦ 0.935, it is necessary to satisfy the following (2).
0.6 ≤ L / H <1.0 ... (2)
　これにより、さらに、スプリアスが通過帯域内に干渉しにくくなる。 This further makes it less likely that spurious will interfere in the passband.
　図１２から図１４は、図１ＢのＩＸ－ＩＸ線に沿う部分の他の例の断面図である。圧電層２の第１の主面２ａと、電極３の側面３ＳＳとがなす角度θは、７０°以上１１０°以下である。例えば、図９に示す圧電層２の第１の主面２ａと、電極３の側面３ＳＳとがなす角度は、８０°である。例えば、図１２に示す圧電層２の第１の主面２ａと、電極３の側面３ＳＳとがなす角度は、７０°である。図１３に示す圧電層２の第１の主面２ａと、電極３の側面３ＳＳとがなす角度は、９０°である。図１４に示す圧電層２の第１の主面２ａと、電極３の側面３ＳＳとがなす角度は、１１０°である。 12 to 14 are cross-sectional views of another example of the portion along the IX-IX line of FIG. 1B. The angle θ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 3SS of the electrode 3 is 70 ° or more and 110 ° or less. For example, the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 9 and the side surface 3SS of the electrode 3 is 80 °. For example, the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 12 and the side surface 3SS of the electrode 3 is 70 °. The angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 13 and the side surface 3SS of the electrode 3 is 90 °. The angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 14 and the side surface 3SS of the electrode 3 is 110 °.
　同様に、圧電層２の第１の主面２ａと、電極４の側面４ＳＳとがなす角度θは、７０°以上１１０°以下である。例えば、図９に示す圧電層２の第１の主面２ａと、電極４の側面４ＳＳとがなす角度は、８０°である。例えば、図１２に示す圧電層２の第１の主面２ａと、電極４の側面４ＳＳとがなす角度は、７０°である。図１３に示す圧電層２の第１の主面２ａと、電極４の側面４ＳＳとがなす角度は、９０°である。図１４に示す圧電層２の第１の主面２ａと、電極４の側面４ＳＳとがなす角度は、１１０°である。 Similarly, the angle θ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 4SS of the electrode 4 is 70 ° or more and 110 ° or less. For example, the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 9 and the side surface 4SS of the electrode 4 is 80 °. For example, the angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 12 and the side surface 4SS of the electrode 4 is 70 °. The angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 13 and the side surface 4SS of the electrode 4 is 90 °. The angle formed by the first main surface 2a of the piezoelectric layer 2 shown in FIG. 14 and the side surface 4SS of the electrode 4 is 110 °.
　以上説明したように、弾性波装置１は、圧電層２と、Ｚ方向に交差するＸ方向において対向し、第１の主面２ａの上に隣り合って設けられた少なくとも１対の電極３、電極４と、圧電層２の第１の主面２ａと１対の電極３、電極４とを覆う保護膜１１と、を備える。１対の電極３、電極４のそれぞれは、電極３、電極４の第１面３Ｕ、４Ｕと、第１面３Ｕ、４Ｕと反対側であって、かつ圧電層２側にある第２面３Ｄ、４Ｄと、を有している。 As described above, the elastic wave device 1 faces the piezoelectric layer 2 in the X direction intersecting the Z direction, and at least one pair of electrodes 3 provided adjacent to each other on the first main surface 2a. The electrode 4 is provided with a protective film 11 that covers the first main surface 2a of the piezoelectric layer 2, a pair of electrodes 3, and the electrode 4. Each of the pair of electrodes 3 and 4 is on the opposite side of the first surface 3U and 4U of the electrode 3 and the electrode 4 and the first surface 3U and 4U, and on the second surface 3D on the piezoelectric layer 2 side. It has 4D and.
　１対の電極３、電極４のうち、少なくとも１つの電極３又は電極４の第１面３Ｕ、４Ｕを覆う保護膜１１の上面１１ＵをＺ方向にみて、Ｘ方向における保護膜１１の上面１１Ｕの端部１１ＵＥから第１面３Ｕ又は第１面４Ｕの端部１１ＤＥまでの距離をＬとし、第１面３Ｕ又は第１面４Ｕから保護膜１１の上面１１Ｕまでの厚みをＨとする。このとき、第１実施形態の弾性波装置は、下記式（１）を満たす。
　０．３≦Ｌ／Ｈ＜１．０　・・・　（１） Of the pair of electrodes 3 and 4, the upper surface 11U of the protective film 11 covering at least one of the electrodes 3 or the first surface 3U and 4U of the electrode 4 is viewed in the Z direction, and the upper surface 11U of the protective film 11 in the X direction. The distance from the end portion 11UE to the end portion 11DE of the first surface 3U or the first surface 4U is L, and the thickness from the first surface 3U or the first surface 4U to the upper surface 11U of the protective film 11 is H. At this time, the elastic wave device of the first embodiment satisfies the following formula (1).
0.3 ≤ L / H <1.0 ... (1)
　これにより、スプリアスが発生する周波数Ｆｓｐｕｒは、通過帯域になく、共振特性の劣化が抑制されている。 As a result, the frequency Fspur in which spurious is generated is not in the pass band, and deterioration of resonance characteristics is suppressed.
　弾性波装置１、３１、４１では、厚み滑り１次モードのバルク波が利用されている。これにより、結合係数が高まり、良好な共振特性が得られる弾性波装置を提供することができる。 In the elastic wave devices 1, 31, and 41, bulk waves in the thickness slip primary mode are used. This makes it possible to provide an elastic wave device in which the coupling coefficient is increased and good resonance characteristics can be obtained.
　また、第１の電極３及び第２の電極４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。これにより、弾性波装置を小型化でき、かつＱ値を高めることができる。 Further, the first electrode 3 and the second electrode 4 are adjacent electrodes, and d / p is 0 when the thickness of the piezoelectric layer is d and the distance between the centers of the first electrode and the second electrode is p. It is said to be 5.5 or less. As a result, the elastic wave device can be miniaturized and the Q value can be increased.
　さらに望ましい態様として、弾性波装置は、下記式（２）を満たす。
　０．６≦Ｌ／Ｈ＜１．０　・・・　（２） As a more desirable embodiment, the elastic wave device satisfies the following formula (2).
0.6 ≤ L / H <1.0 ... (2)
　これにより、さらに、スプリアスが通過帯域内に干渉しにくくなる。 This further makes it less likely that spurious will interfere in the passband.
　圧電層２の第１の主面２ａと、電極３の側面３ＳＳとがなす角度θは、７０°以上１１０°以下である。同様に、圧電層２の第１の主面２ａと、電極４の側面４ＳＳとがなす角度θは、７０°以上１１０°以下である。これにより、上記式（１）又は式（２）を満たしやすくなる。 The angle θ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 3SS of the electrode 3 is 70 ° or more and 110 ° or less. Similarly, the angle θ formed by the first main surface 2a of the piezoelectric layer 2 and the side surface 4SS of the electrode 4 is 70 ° or more and 110 ° or less. This makes it easier to satisfy the above formula (1) or formula (2).
　保護膜１１は、酸化ケイ素及び窒化ケイ素の群から少なくとも１つ選択される。これにより、電極３、電極４及び圧電層２を保護することができる。 At least one protective film 11 is selected from the group of silicon oxide and silicon nitride. Thereby, the electrode 3, the electrode 4, and the piezoelectric layer 2 can be protected.
　なお、上記した実施の形態は、本開示の理解を容易にするためのものであり、本開示を限定して解釈するためのものではない。本開示は、その趣旨を逸脱することなく、変更／改良され得るとともに、本開示にはその等価物も含まれる。 It should be noted that the above-described embodiment is for facilitating the understanding of the present disclosure, and is not for limiting the interpretation of the present disclosure. The present disclosure may be modified / improved without departing from its spirit, and the present disclosure also includes its equivalents.
１、３１、４１　弾性波装置
２　圧電層
２ａ　第１の主面
２ｂ　第２の主面
３　電極（第１の電極）
３Ｄ　第２面
３ＳＳ　側面
３Ｕ　第１面
４　電極（第２の電極）
４Ｄ　第２面
４ＳＳ　側面
４Ｕ　第１面
５　第１のバスバー
６　第２のバスバー
７　中間層
８　支持部材
９　空洞部
１１　保護膜
１１Ｄ　下面
１１ＤＥ　端部
１１Ｅ　端部
１１Ｕ　上面
２０１　圧電層
２０１ａ　第１の主面
２０１ｂ　第２の主面
Ｃ　励振領域
Ｆａ　反共振周波数
Ｆｒ　共振周波数
Ｆｓｐｕｒ　周波数
Ｈ　保護膜の厚み
Ｌ　保護膜の距離
ｄ　圧電層の平均厚み
ｐ　隣り合う電極の中心間距離又は中心間距離の平均距離
θ　角度 1, 31, 41 Elastic wave device 2 Piezoelectric layer 2a First main surface 2b Second main surface 3 Electrode (first electrode)
3D 2nd surface 3SS side surface 3U 1st surface 4 electrode (2nd electrode)
4D 2nd surface 4SS Side surface 4U 1st surface 5 1st bus bar 6 2nd bus bar 7 Intermediate layer 8 Support member 9 Cavity 11 Protective film 11D Lower surface 11DE End 11E End 11U Upper surface 201 Piezoelectric layer 201a 1st main Surface 201b Second main surface C Excitation region Fa Anti-resonance frequency F Resonance frequency Fspur Frequency H Protective film thickness L Protective film distance d Average thickness of piezoelectric layer p Average distance between centers of adjacent electrodes or average distance between centers θ angle

Claims (6)

  1. 　第１の主面と、前記第１の主面の反対側であって、かつ前記第１の主面に対して第１方向にある第２の主面とを有する圧電層と、
    　前記第１方向に交差する第２方向において対向し、前記第１の主面の上に隣り合って設けられた少なくとも１対の電極と、
    　前記圧電層の前記第１の主面と前記１対の電極とを覆う保護膜と、を備え、
    　前記１対の電極のそれぞれは、第１面と、前記第１面と反対側であって、かつ前記圧電層側にある第２面と、を有し、
    　前記１対の電極のうち、少なくとも１つの電極の前記第１面を覆う前記保護膜の上面を前記第１方向にみて、前記第２方向における前記保護膜の上面の端部から前記少なくとも１つの電極の前記第１面の端部までの距離をＬとし、前記少なくとも１つの電極の前記第１面から前記保護膜の上面までの厚みをＨとすると、下記式（１）を満たす、弾性波装置。
    　０．３≦Ｌ／Ｈ＜１．０　・・・　（１）     A piezoelectric layer having a first main surface and a second main surface opposite to the first main surface and in a first direction with respect to the first main surface.
    With at least one pair of electrodes facing each other in the second direction intersecting the first direction and adjacently provided on the first main surface.
    A protective film covering the first main surface of the piezoelectric layer and the pair of electrodes is provided.
    Each of the pair of electrodes has a first surface and a second surface opposite to the first surface and on the piezoelectric layer side.
    Of the pair of electrodes, the upper surface of the protective film covering the first surface of at least one electrode is viewed in the first direction, and at least one of the protective films from the end of the upper surface of the protective film in the second direction. Assuming that the distance to the end of the first surface of the electrode is L and the thickness of at least one electrode from the first surface to the upper surface of the protective film is H, an elastic wave satisfying the following formula (1). Device.
    0.3 ≤ L / H <1.0 ... (1)
  2. 　請求項１に記載の弾性波装置であって、
    　前記圧電層は、ニオブ酸リチウム又はタンタル酸リチウムを含み、
    　厚み滑り１次モードのバルク波を利用する、弾性波装置。     The elastic wave device according to claim 1.
    The piezoelectric layer contains lithium niobate or lithium tantalate and contains.
    An elastic wave device that uses bulk waves in the primary mode of thickness slip.
  3. 　請求項１に記載の弾性波装置であって、
    　前記圧電層は、ニオブ酸リチウム又はタンタル酸リチウムを含み、
    　前記圧電層の平均厚みをｄ、隣り合う電極の中心間距離をｐとして、ｄ／ｐが０．５以下である、弾性波装置。     The elastic wave device according to claim 1.
    The piezoelectric layer contains lithium niobate or lithium tantalate and contains.
    An elastic wave device having d / p of 0.5 or less, where d is the average thickness of the piezoelectric layer and p is the distance between the centers of adjacent electrodes.
  4. 　請求項１から３のいずれか１項に記載の弾性波装置であって、
    　下記式（２）を満たす、弾性波装置。
    　０．６≦Ｌ／Ｈ＜１．０　・・・　（２）     The elastic wave device according to any one of claims 1 to 3.
    An elastic wave device that satisfies the following formula (2).
    0.6 ≤ L / H <1.0 ... (2)
  5. 　請求項１から４のいずれか１項に記載の弾性波装置であって、
    　前記保護膜は、酸化ケイ素及び窒化ケイ素の群から少なくとも１つ選択される、
    　弾性波装置。     The elastic wave device according to any one of claims 1 to 4.
    The protective film is selected from the group of silicon oxide and silicon nitride.
    Elastic wave device.
  6. 　請求項１から５のいずれか１項に記載の弾性波装置であって、
    　前記圧電層の前記第１の主面と、前記電極の側面とがなす角度は、７０°以上１１０°以下である、
    　弾性波装置。     The elastic wave device according to any one of claims 1 to 5.
    The angle between the first main surface of the piezoelectric layer and the side surface of the electrode is 70 ° or more and 110 ° or less.
    Elastic wave device.
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JP2001168671A (en) * 1999-12-07 2001-06-22 Matsushita Electric Ind Co Ltd Surface acoustic wave device and its manufacture
JP2006109287A (en) * 2004-10-08 2006-04-20 Alps Electric Co Ltd Surface acoustic wave element and manufacturing method thereof
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