WO2023013741A1 - Elastic wave device - Google Patents
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- WO2023013741A1 WO2023013741A1 PCT/JP2022/030013 JP2022030013W WO2023013741A1 WO 2023013741 A1 WO2023013741 A1 WO 2023013741A1 JP 2022030013 W JP2022030013 W JP 2022030013W WO 2023013741 A1 WO2023013741 A1 WO 2023013741A1
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- electrode
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- electrode fingers
- wave device
- piezoelectric layer
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- 239000000758 substrate Substances 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims description 48
- 230000005284 excitation Effects 0.000 claims description 27
- 239000013078 crystal Substances 0.000 claims description 14
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims description 8
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 7
- 150000002500 ions Chemical class 0.000 claims description 2
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- 235000019687 Lamb Nutrition 0.000 description 7
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 4
- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
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- 229910002601 GaN Inorganic materials 0.000 description 1
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 1
- 229910003327 LiNbO3 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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- 229910052681 coesite Inorganic materials 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
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- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
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- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
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- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
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- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
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Images
Classifications
-
- 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 elastic wave devices.
- Patent Document 1 describes an elastic wave device.
- leakage of elastic waves may occur in the direction in which the electrode fingers extend.
- the present disclosure is intended to solve the above-described problems, and aims to suppress leakage of elastic waves.
- An elastic wave device includes a support member including a support substrate having a thickness in a first direction, a piezoelectric layer provided in the first direction of the support member, a main surface of the piezoelectric layer provided, a plurality of first electrode fingers extending in a second direction intersecting the first direction; a first busbar electrode to which the plurality of first electrode fingers are connected; an IDT electrode having a plurality of second electrode fingers facing any one of the plurality of first electrode fingers and extending in the second direction; and a second busbar electrode to which the plurality of second electrode fingers are connected; a gap between at least one first electrode finger and the second busbar electrode or between at least one second electrode finger and the first busbar electrode in plan view in the first direction
- the region has a non-piezoelectric region containing non-piezoelectric material.
- elastic wave leakage can be suppressed.
- FIG. 1A is a perspective view showing an elastic wave device according to a 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 along line II-II of FIG. 1A.
- FIG. 3A is a schematic cross-sectional view for explaining Lamb waves propagating through the piezoelectric layer of the comparative example.
- FIG. 3B is a schematic cross-sectional view for explaining a thickness-shear primary mode bulk wave propagating through the piezoelectric layer of the first embodiment.
- FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of a thickness-shear primary mode bulk wave propagating in the piezoelectric layer of the first embodiment.
- FIG. 1A is a perspective view showing an elastic wave device according to a 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 along line II
- FIG. 5 is an explanatory diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment.
- FIG. 2 is an explanatory diagram showing the relationship between , and the fractional band.
- FIG. FIG. 7 is a plan view showing an example in which a pair of electrodes are provided in the elastic wave device of the first embodiment.
- FIG. 8 is a reference diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment.
- FIG. 9 shows the ratio bandwidth when a large number of elastic wave resonators are configured in the elastic wave device of the first embodiment, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. is an explanatory diagram showing the relationship between.
- FIG. 9 shows the ratio bandwidth when a large number of elastic wave resonators are configured in the elastic wave device of the first embodiment, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the magnitude of the spurious.
- FIG. 10 is an explanatory diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth.
- FIG. 11 is an explanatory diagram showing a map of the fractional band with respect to the Euler angles (0°, ⁇ , ⁇ ) of LiNbO 3 when d/p is infinitely close to 0.
- FIG. 12 is a modification of the first embodiment, and is a cross-sectional view of a portion taken along line II-II of FIG. 1A.
- FIG. 13 is a partially cutaway perspective view for explaining the elastic wave device according to the embodiment of the present disclosure.
- 14 is a plan view showing an example of the elastic wave device according to the first embodiment;
- FIG. 15 is a cross-sectional view taken along line XV-XV of FIG. 14.
- FIG. 16 is an explanatory diagram showing an example of admittance characteristics of the elastic wave device according to the first embodiment.
- FIG. 17 is a plan view showing an example of the elastic wave device according to the second embodiment.
- 18 is a cross-sectional view taken along line XVIII-XVIII of FIG. 17.
- FIG. 1A is a perspective view showing an elastic wave device according to a 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 consist of LiTaO 3 .
- the cut angle of LiNbO 3 and LiTaO 3 is Z-cut in the first embodiment.
- the cut angles of LiNbO 3 and LiTaO 3 may be rotated 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 a first main surface 2a and a second main surface 2b facing each other in the Z direction. Electrode fingers 3 and 4 are provided on the first main surface 2a.
- the electrode finger 3 is an example of the "first electrode finger” and the electrode finger 4 is an example of the "second electrode finger”.
- the multiple electrode fingers 3 are multiple “first electrodes” connected to the first busbar electrodes 5 .
- a plurality of electrode fingers 4 are a plurality of “second electrodes” connected to second busbar electrodes 6 .
- the plurality of electrode fingers 3 and the plurality of electrode fingers 4 are interdigitated with each other.
- an IDT (Interdigital Transducer) electrode including electrode fingers 3 , electrode fingers 4 , first busbar electrodes 5 , and second busbar electrodes 6 is configured.
- the electrode fingers 3 and 4 have a rectangular shape and a length direction.
- the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in a direction perpendicular to the length direction.
- Both the length direction of the electrode fingers 3 and 4 and the direction orthogonal to the length direction of the electrode fingers 3 and 4 are directions that intersect the thickness direction of the piezoelectric layer 2 . Therefore, it can be said that the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2 .
- the thickness direction of the piezoelectric layer 2 is defined as the Z direction (or first direction)
- the length direction of the electrode fingers 3 and 4 is defined as the Y direction (or second direction)
- the electrode fingers 3 and electrode fingers 4 may be described as the X direction (or the third direction).
- the length direction of the electrode fingers 3 and 4 may be interchanged with the direction orthogonal to the length direction of the electrode fingers 3 and 4 shown in FIGS. 1A and 1B. That is, in FIGS. 1A and 1B, the electrode fingers 3 and 4 may extend in the direction in which the first busbar electrodes 5 and the second busbar electrodes 6 extend. In that case, the first busbar electrode 5 and the second busbar electrode 6 extend in the direction in which the electrode fingers 3 and 4 extend in FIGS. 1A and 1B.
- a pair of structures in which the electrode fingers 3 connected to one potential and the electrode fingers 4 connected to the other potential are adjacent to each other are arranged in a direction perpendicular to the length direction of the electrode fingers 3 and 4. Multiple pairs are provided.
- the electrode finger 3 and the electrode finger 4 are adjacent to each other, not when the electrode finger 3 and the electrode finger 4 are arranged so as to be in direct contact, but when the electrode finger 3 and the electrode finger 4 are arranged with a gap therebetween. It refers to the case where the When the electrode finger 3 and the electrode finger 4 are adjacent to each other, there are electrodes connected to the hot electrode and the ground electrode, including other electrode fingers 3 and 4, between the electrode finger 3 and the electrode finger 4. is not placed.
- the logarithms need not be integer pairs, but may be 1.5 pairs, 2.5 pairs, or the like.
- the center-to-center distance, that is, the pitch, between the electrode fingers 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 electrode fingers 3 and 4 means the center of the width dimension of the electrode fingers 3 in the direction orthogonal to the length direction of the electrode fingers 3 and the distance orthogonal to the length direction of the electrode fingers 4 . It is the distance connecting the center of the width dimension of the electrode finger 4 in the direction of
- the electrode fingers 3 and 4 when at least one of the electrode fingers 3 and 4 is plural (when there are 1.5 or more pairs of electrodes when the electrode fingers 3 and 4 are paired as a pair of electrode pairs), the electrode fingers 3.
- the center-to-center distance of the electrode fingers 4 refers to the average value of the center-to-center distances of adjacent electrode fingers 3 and electrode fingers 4 among 1.5 or more pairs of electrode fingers 3 and electrode fingers 4 .
- the width of the electrode fingers 3 and 4 that is, the dimension in the facing direction of the electrode fingers 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 electrode fingers 3 and 4 is the distance between the center of the dimension (width dimension) of the electrode finger 3 in the direction perpendicular to the length direction of the electrode finger 3 and the length of the electrode finger 4. It is the distance connecting the center of the dimension (width dimension) of the electrode finger 4 in the direction orthogonal to the direction.
- the direction orthogonal to the length direction of the electrode fingers 3 and 4 is the direction orthogonal to the polarization direction of the piezoelectric layer 2 .
- “perpendicular” is not limited to being strictly perpendicular, but substantially perpendicular (the angle formed by the direction perpendicular to the length direction of the electrode fingers 3 and electrode fingers 4 and the polarization direction is, for example, 90° ⁇ 10°).
- a support substrate 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an intermediate layer 7 interposed therebetween.
- the intermediate layer 7 and the support substrate 8 have a frame shape and, as shown in FIG. 2, openings 7a and 8a.
- a space (air gap) 9 is thereby formed.
- the space 9 is provided so as not to disturb the vibration of the excitation region C of the piezoelectric layer 2 . Therefore, the support substrate 8 is laminated on the second main surface 2b with the intermediate layer 7 interposed therebetween at a position not overlapping the portion where at least one pair of electrode fingers 3 and 4 are provided. Note that the intermediate layer 7 may not be provided. Therefore, the support substrate 8 can be directly or indirectly laminated to the second main surface 2b of the piezoelectric layer 2 .
- the intermediate layer 7 is made of silicon oxide.
- the intermediate layer 7 can be formed of an appropriate insulating material other than silicon oxide, such as silicon nitride and alumina.
- the support substrate 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).
- high-resistance Si having a resistivity of 4 k ⁇ or more is desirable.
- the support substrate 8 can also be constructed using an appropriate insulating material or semiconductor material.
- Materials for the support substrate 8 include, for example, aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and steer.
- Various ceramics such as tight and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.
- the plurality of electrode fingers 3, electrode fingers 4, first busbar electrodes 5, and second busbar electrodes 6 are made of appropriate metals or alloys such as Al and AlCu alloys.
- the electrode fingers 3, the electrode fingers 4, the first busbar electrodes 5, and the second busbar electrodes 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 electrode fingers 3 and the multiple electrode fingers 4 . More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 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 set to 0.5 or less.
- 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.
- the electrode fingers 3 and the electrode fingers 4 When at least one of the electrode fingers 3 and the electrode fingers 4 is plural as in the first embodiment, that is, when the electrode fingers 3 and the electrode fingers 4 form a pair of electrodes, the electrode fingers 3 and the electrode fingers When there are 1.5 pairs or more of 4, the center-to-center distance p between the adjacent electrode fingers 3 and 4 is the average distance between the center-to-center distances between the adjacent electrode fingers 3 and 4 .
- the acoustic wave device 1 of the first embodiment has the above configuration, even if the logarithms of the electrode fingers 3 and 4 are reduced in an attempt 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 cross-sectional view for explaining Lamb waves propagating through the piezoelectric layer of the comparative example.
- FIG. 3B is a schematic cross-sectional view for explaining a thickness-shear primary mode bulk wave propagating through the piezoelectric layer of the first embodiment.
- FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of a thickness-shear primary mode bulk wave propagating in the piezoelectric layer of the first embodiment.
- FIG. 3A shows an acoustic wave device as described in Patent Document 1, in which Lamb waves propagate through the piezoelectric layer.
- waves propagate through the piezoelectric layer 201 as indicated by arrows.
- the piezoelectric layer 201 has a first principal surface 201a and a second principal surface 201b, and the thickness direction connecting the first principal surface 201a and the second principal surface 201b is the Z direction.
- the X direction is the direction in which the electrode fingers 3 and 4 of the IDT electrodes are aligned.
- the wave propagates in the X direction as shown.
- the wave is generated between the first main surface 2a and the second main surface 2a of the piezoelectric layer 2. It propagates almost in the direction connecting the surface 2b, that is, in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. 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 electrode fingers 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 primary thickness-shear mode is the first region 251 included in the excitation region C (see FIG. 1B) of the piezoelectric layer 2 and the first region 251 included in the excitation region C (see FIG. 1B). 2 area 252 is reversed.
- FIG. 4 schematically shows bulk waves when a voltage is applied between the electrode fingers 3 so that the electrode fingers 4 have a higher potential than the electrode fingers 3 .
- the first region 251 is a region of the excitation region C between the virtual plane VP1 that is perpendicular to the thickness direction of the piezoelectric layer 2 and bisects the piezoelectric layer 2 and the first main surface 2a.
- the second region 252 is a region of the excitation region C between the virtual plane VP1 and the second main surface 2b.
- At least one pair of electrodes consisting of the electrode fingers 3 and 4 is arranged. It is not always necessary to have a plurality of pairs of electrode pairs. That is, it is sufficient that at least one pair of electrodes is provided.
- the electrode finger 3 is an electrode connected to a hot potential
- the electrode finger 4 is an electrode connected to a ground potential.
- the electrode finger 3 may be connected to the ground potential and the electrode finger 4 to the hot potential.
- the at least one pair of electrodes are, as described above, electrodes connected to a hot potential or electrodes connected to a ground potential, and no floating electrodes are provided.
- FIG. 5 is an explanatory diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment.
- the design parameters of the acoustic wave device 1 that obtained the resonance characteristics shown in FIG. 5 are as follows.
- Piezoelectric layer 2 LiNbO3 with Euler angles (0°, 0°, 90°) Thickness of piezoelectric layer 2: 400 nm
- Length of excitation region C (see FIG. 1B): 40 ⁇ m Number of electrode pairs consisting of electrode fingers 3 and 4: 21 pairs Center-to-center distance (pitch) between electrode fingers 3 and 4: 3 ⁇ m Width of electrode fingers 3 and 4: 500 nm d/p: 0.133
- Middle layer 7 Silicon oxide film with a thickness of 1 ⁇ m
- Support substrate 8 Si
- the excitation region C (see FIG. 1B) is a region where the electrode fingers 3 and 4 overlap when viewed in the X direction perpendicular to the length direction of the electrode fingers 3 and 4. .
- the length of the excitation region C is the dimension along the length direction of the electrode fingers 3 and 4 of the excitation region C. As shown in FIG. Here, the excitation region C is an example of the "intersection region".
- the inter-electrode distances of the electrode pairs consisting of the electrode fingers 3 and 4 are all equal in a plurality of pairs. That is, the electrode fingers 3 and the electrode fingers 4 are 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 shows d/2p, where p is the center-to-center distance between adjacent electrodes or the average distance of the center-to-center distances, and d is the average thickness of the piezoelectric layer 2. It is an explanatory view showing the relationship with the fractional bandwidth as.
- At least one pair of electrodes may be one pair, and the above p is the center-to-center distance between adjacent electrode fingers 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 electrode fingers 3 and 4 should be p.
- the thickness d of the piezoelectric layer 2 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 showing an example in which a pair of electrodes are provided in the elastic wave device of the first embodiment.
- a pair of electrodes having electrode fingers 3 and 4 are 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 excitation region is an overlapping region of the plurality of electrode fingers 3 and 4 when viewed in the direction in which any adjacent electrode fingers 3 and 4 are facing each other. It is desirable that the metallization ratio MR of the adjacent electrode fingers 3 and 4 with respect to the region C satisfies MR ⁇ 1.75(d/p)+0.075. In that case, spurious can be effectively reduced. 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 elastic wave device of the first embodiment.
- 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 excitation region C is the portion surrounded by the dashed-dotted line.
- the excitation region C is a region where the electrode fingers 3 and 4 overlap with the electrode fingers 4 when viewed in a direction perpendicular to the length direction of the electrode fingers 3 and 4, that is, in a facing direction. a region where the electrode fingers 3 overlap each other; and a region between the electrode fingers 3 and 4 where the electrode fingers 3 and 4 overlap each other.
- the area of the electrode fingers 3 and 4 in the excitation region C with respect to the area of the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallization portion to the area of the excitation region C.
- the ratio of the metallization portion included in the entire excitation region C to the total area of the excitation region C should be MR.
- FIG. 9 shows the ratio bandwidth when a large number of elastic wave resonators are configured in the elastic wave device of the first embodiment, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. is an explanatory diagram showing the relationship between.
- the ratio band was adjusted by changing the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4 in various ways.
- FIG. 9 shows the results when the piezoelectric layer 2 made of Z-cut LiNbO 3 is used, but the same tendency is obtained when the piezoelectric layer 2 with other cut angles is 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 changes the parameters constituting the fractional band, even if the passband appear within. 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 electrode fingers 3 and 4, the spurious response can be reduced.
- FIG. 10 is an explanatory diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth.
- various elastic wave devices 1 with different d/2p and MR were configured, 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 an explanatory diagram showing a map of the fractional band with respect to the Euler angles (0°, ⁇ , ⁇ ) of LiNbO 3 when d/p is infinitely close to 0.
- FIG. A hatched portion in FIG. 11 is a region where a fractional bandwidth of at least 5% or more is obtained. When the range of the area is approximated, it becomes the range represented by the following formulas (1), (2) and (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 ] ⁇ 180°) Equation (2) (0° ⁇ 10°, [180°-30°(1-( ⁇ -90) 2 /8100) 1/2 ] ⁇ 180°, arbitrary ⁇ ) Equation (3)
- the fractional band can be sufficiently widened, which is preferable.
- FIG. 12 is a modification of the first embodiment, and is a cross-sectional view of a portion taken along line II-II of FIG. 1A.
- an acoustic multilayer film 42 is laminated on the second main surface 2 b of the piezoelectric layer 2 .
- the acoustic multilayer film 42 has a laminated structure of low acoustic impedance layers 42a, 42c, 42e with relatively low acoustic impedance and high acoustic impedance layers 42b, 42d with relatively high acoustic impedance.
- the low acoustic impedance layer is, for example, a layer of SiO2
- the high acoustic impedance layer is, for example, a metal layer such as W, Pt or a dielectric layer such as AlN, SiN.
- the thickness-shear primary mode bulk wave can be confined in the piezoelectric layer 2 without using the space 9 in the elastic wave device 1 .
- the acoustic wave device 41 by setting the above d/p to 0.5 or less, it is possible to obtain resonance characteristics based on bulk waves in the first-order thickness shear mode.
- the number of lamination of the low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b, 42d is not particularly limited. At least one of the high acoustic impedance layers 42b, 42d needs to be arranged 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 appropriate materials as long as the acoustic impedance relationship is satisfied.
- Examples of materials for the low acoustic impedance layers 42a, 42c, and 42e include silicon oxide and silicon oxynitride.
- Materials for the high acoustic impedance layers 42b and 42d include alumina, silicon nitride, and metals.
- FIG. 13 is a partially cutaway perspective view for explaining the elastic wave device according to the embodiment of the present disclosure.
- the outer peripheral edge of the space portion 9 is indicated by a dashed line.
- the elastic wave device of the present disclosure may utilize plate waves.
- the elastic wave device 301 has reflectors 310 and 311 as shown in FIG. Reflectors 310 and 311 are provided on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the acoustic wave propagation direction.
- a Lamb wave as a plate wave is excited by applying an AC electric field to the electrode fingers 3 and 4 on the space 9.
- the reflectors 310 and 311 are provided on both sides, it is possible to obtain resonance characteristics due to Lamb waves as Lamb waves.
- the elastic wave devices 1 and 101 use bulk waves in the primary mode of thickness shear.
- the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes, the thickness of the piezoelectric layer 2 is d, and the center of the first electrode finger 3 and the second electrode finger 4 is d/p is set to 0.5 or less, where p is the distance between them.
- the Q value can be increased even if the elastic wave device is miniaturized.
- the piezoelectric layer 2 is made of lithium niobate or lithium tantalate.
- the first principal surface 2a or the second principal surface 2b of the piezoelectric layer 2 has first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2. It is desirable to cover the finger 3 and the second electrode finger 4 with a protective film.
- FIG. 14 is a plan view showing an example of the elastic wave device according to the first embodiment.
- 15 is a cross-sectional view taken along line XV-XV of FIG. 14.
- FIG. An acoustic wave device 1A according to the first embodiment includes a piezoelectric layer 2, IDT electrodes including electrode fingers 3 and 4 and busbar electrodes 5 and 6, and a support member.
- the support member is a member provided with the support substrate 8 .
- the support member consists of a support substrate 8 .
- the piezoelectric layer 2 is provided on the support substrate 8 in the Z direction.
- the support member may further include an intermediate layer 7 provided in the Z direction of the support substrate 8 .
- the support member has a space portion 9 at a position at least partially overlapping with the IDT electrode when viewed from above in the Z direction.
- the space 9 is provided so as to penetrate the support substrate 8 in the Z direction, but this is only an example, and may be provided only on the piezoelectric layer 2 side of the support member.
- the piezoelectric layer 2 is provided in the Z direction of the support member.
- the piezoelectric layer 2 is a layer containing piezoelectric lithium niobate and unavoidable impurities, and is, for example, single crystal Z-cut lithium niobate.
- the present inventors have found that in an elastic wave device that utilizes a thickness-shear first-order bulk elastic wave, an elastic wave leakage mode is generated outside the intersection region C in the Y direction, and the first bus bar electrode 5 or the second bus bar electrode 5 It was found that an elastic wave leakage mode occurs outside the busbar electrodes 6 in the Y direction.
- the inventors of the present invention found that the leakage of elastic waves can be suppressed by providing the non-piezoelectric region 20 in the gap region.
- the gap region refers to a region between the first electrode fingers 3 and the second busbar electrodes 6 in the Y direction or between the second electrode fingers 4 and the first busbar electrodes 5 in the Y direction.
- the non-piezoelectric region 20 will be described below.
- the non-piezoelectric region 20 is a region including the non-piezoelectric body 21 when viewed in plan in the Z direction. More specifically, the non-piezoelectric region 20 is a region composed of the non-piezoelectric body 21 and the portion of the piezoelectric layer 2 that overlaps the non-piezoelectric body 21 in plan view in the Z direction. In the first embodiment, the non-piezoelectric region 20 is a region made of a non-piezoelectric material 21 . A non-piezoelectric region 20 is in the gap region. In the first embodiment, the non-piezoelectric region 20 is in the region between the busbar electrodes 5, 6 and the intersection region C in the Y direction. As a result, excitation of elastic waves in the gap region is inhibited, so leakage of elastic waves can be suppressed.
- the non-piezoelectric material 21 is a material that does not exhibit piezoelectricity at all, or a material with low piezoelectricity. More specifically, the non-piezoelectric material 21 refers to a material whose absolute value of the piezoelectric constant e15 is 50% or less with respect to the piezoelectric layer 2 in the intersection region C. In the first embodiment, the non-piezoelectric body 21 is provided so as to penetrate the piezoelectric layer 2 in the Z direction.
- the non-piezoelectric material 21 is a material similar to that of the piezoelectric layer 2 in the intersection region C and having lower crystallinity and orientation than the piezoelectric layer 2, such as non-single crystal lithium niobate.
- non-single crystal refers to polycrystal, amorphous, or a crystal in an intermediate state between polycrystal and amorphous.
- the electromechanical coupling coefficient of the non-piezoelectric body 21 can be made smaller than the electromechanical coupling coefficient of the piezoelectric layer 2 .
- the piezoelectricity and orientation of the material depend on the electromechanical coupling coefficient, the piezoelectricity and orientation of the non-piezoelectric body 21 can be made smaller than those of the piezoelectric layer 2 . Thereby, the piezoelectricity of the non-piezoelectric body 21 can be suppressed, and the leakage of elastic waves can be further suppressed.
- the non-piezoelectric material 21 is preferably non-oriented.
- the electromechanical coupling coefficient of the non-piezoelectric body 21 can be made smaller than the electromechanical coupling coefficient of the piezoelectric layer 2 more reliably. Therefore, the piezoelectric constant of the non-piezoelectric body 21 can be made smaller than the piezoelectric constant of the piezoelectric layer 2 more reliably.
- the non-piezoelectric material 21 is not limited to the amorphous material of the same kind as the piezoelectric layer 2 .
- the non-piezoelectric material 21 may be, for example, a material obtained by partially reversing the polarization of the material of the piezoelectric layer 2 . In this case, the piezoelectricity of the non-piezoelectric body 21 can be suppressed.
- the non-piezoelectric material 21 may be made of a material different from that of the piezoelectric layer 2 .
- the non-piezoelectric body 21 may be, for example, lithium niobate that is damaged by ion implantation of a specific element.
- the specific element is, for example, hydrogen, helium, or the like.
- the non-piezoelectric material 21 can be non-single-crystal, so that the piezoelectricity of the non-piezoelectric material 21 can be suppressed.
- FIG. 16 is an explanatory diagram showing an example of admittance characteristics of the elastic wave device according to the first embodiment.
- the example is the elastic wave device 1A according to the first embodiment
- the comparative example is the elastic wave device without the non-piezoelectric region 20 .
- the elastic wave device according to the example has a narrower peak width at the resonance frequency than the elastic wave device according to the comparative example, so propagation loss is suppressed, and elastic wave leakage is suppressed. found to be suppressed.
- the acoustic wave device 1A includes a support member including the support substrate 8 having a thickness in the first direction, the piezoelectric layer 2 provided in the first direction of the support member, and the piezoelectric layer 2 provided in the first direction.
- a plurality of first electrode fingers 3 provided on the main surface (first main surface 2a) of the layer 2 and extending in a second direction intersecting the first direction; , a plurality of second electrode fingers 4 facing any one of the plurality of first electrode fingers 3 in a third direction orthogonal to the second direction and extending in the second direction, and a plurality of second electrode fingers 4 and an IDT electrode having a second busbar electrode 6 to which is connected, and when viewed in the first direction, between at least one first electrode finger 3 and the second busbar electrode 6
- a non-piezoelectric region 20 containing a non-piezoelectric body 21 is provided in the gap region between one second electrode finger 4 and the first busbar electrode 5 .
- the non-piezoelectric region 20 overlaps the first electrode finger 3 or the second electrode finger 4 when viewed in plan in the first direction. Even in this case, leakage of elastic waves can be suppressed.
- the thickness-shear primary mode bulk wave can be confined within the piezoelectric layer 2 .
- the supporting member includes, on the piezoelectric layer 2 side, one or more low acoustic impedance layers 42a, 42c, and 42e having an acoustic impedance lower than that of the piezoelectric layer 2 and one or more high acoustic impedance layers 42a, 42c, and 42e having an acoustic impedance higher than that of the piezoelectric layer 2. It has an acoustic reflection layer (acoustic multilayer film 42) including acoustic impedance layers 42b and 42d. As a result, the thickness-shear primary mode bulk wave can be confined within the piezoelectric layer 2 .
- the piezoelectric layer 2 is a single crystal material
- the non-piezoelectric body 21 is a polycrystalline single crystal material, an amorphous single crystal material, or a single crystal material into which ions of a specific element are implanted. It is a material that has been As a result, the electromechanical coupling coefficient of the non-piezoelectric body 21 can be made smaller than the electromechanical coupling coefficient of the piezoelectric layer 2 , and the piezoelectricity and orientation of the non-piezoelectric body 21 can be made smaller than those of the piezoelectric layer 2 . can. Thereby, the piezoelectricity of the non-piezoelectric body 21 can be suppressed, and the leakage of elastic waves can be further suppressed.
- the piezoelectric layer 2 is Z-cut, and the second Euler angle ⁇ of the piezoelectric layer 2 is -15° or more and 15° or less. Even in this case, leakage of elastic waves can be suppressed.
- the thickness of the piezoelectric layer 2 is the center-to-center distance between the adjacent first electrode fingers 3 and the second electrode fingers 4 among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4. It is 2p or less when p.
- the piezoelectric layer 2 contains lithium niobate or lithium tantalate. As a result, it is possible to provide an elastic wave device capable of obtaining good resonance characteristics.
- it is configured to be able to use bulk waves in the thickness-shlip mode. As a result, it is possible to provide an elastic wave device with a high coupling coefficient and good resonance characteristics.
- the thickness of the piezoelectric layer 2 is d, and the center-to-center distance between the adjacent first electrode fingers 3 and second electrode fingers 4 among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 is p. , d/p ⁇ 0.5.
- the acoustic wave device 1 can be miniaturized and the Q value can be increased.
- d/p is 0.24 or less.
- the region where the first electrode fingers 3 and the second electrode fingers 4 overlap when viewed in the third direction is the excitation region C, and the first electrode fingers 3 and the second electrode fingers 3 with respect to the excitation region C
- the metallization ratio of finger 4 is MR, MR ⁇ 1.75(d/p)+0.075 is satisfied.
- the fractional bandwidth can be reliably set to 17% or less.
- the piezoelectric layer 2 is made of lithium niobate or lithium tantalate, and the Euler angles ( ⁇ , ⁇ , ⁇ ) of lithium niobate or lithium tantalate satisfy the following formula (1), formula (2) or It is in the range of formula (3). In this case, the fractional bandwidth can be widened sufficiently.
- 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 ] ⁇ 180°) Equation (2) (0° ⁇ 10°, [180°-30°(1-( ⁇ -90) 2 /8100) 1/2 ] ⁇ 180°, arbitrary ⁇ ) Equation (3)
- FIG. 17 is a plan view showing an example of the elastic wave device according to the second embodiment.
- 18 is a cross-sectional view taken along line XVIII-XVIII of FIG. 17.
- FIG. An elastic wave device 1B according to the second embodiment differs from the first embodiment in that a non-piezoelectric region 20B contains a piezoelectric material.
- An elastic wave device 1B according to the second embodiment will be described below with reference to the drawings.
- symbol is attached
- the elastic wave device 1B has a non-piezoelectric region 20B in the region between the busbar electrodes 5, 6 and the intersection region C in the Y direction.
- the non-piezoelectric regions 20B are spaced apart in the X direction so as not to overlap the electrode fingers 3 and 4 when viewed in plan in the first direction.
- the non-piezoelectric region 20B includes a region made of the non-piezoelectric body 21B and a region of the piezoelectric layer 2 that overlaps the non-piezoelectric body 21B when viewed in plan in the Z direction.
- the piezoelectric constant e15 in the region overlapping the non-piezoelectric body 21B is 50% or more of the piezoelectric constant e15 of the piezoelectric material in the intersecting region C when viewed in plan in the Z direction. Even in this case, leakage of elastic waves can be suppressed.
- the non-piezoelectric material 21 is a protective film made of a dielectric material, such as silicon oxide.
- the non-piezoelectric body 21 is provided at a position that does not overlap with the intersection region C when viewed from above in the Z direction.
- the non-piezoelectric body 21 is provided in the gap region.
- ds is larger than dp. That is, the thickness ds of the non-piezoelectric body 21B is less than 50% of the thickness (ds+dp) of the non-piezoelectric region 20B.
- the coupling coefficient of the gap region is significantly reduced compared to the coupling coefficient of the piezoelectric layer 2 in the intersection region C.
- FIG. As a result, excitation of elastic waves in the gap region is inhibited, and leakage of elastic waves can be suppressed.
- the non-piezoelectric regions 20B are spaced apart in the third direction. Even in this case, leakage of elastic waves can be suppressed.
- the non-piezoelectric body 21B contains silicon oxide. Even in this case, leakage of elastic waves can be suppressed.
- the non-piezoelectric body 21B is laminated on the piezoelectric layer 2, and the thickness ds of the non-piezoelectric body 21B is greater than the thickness dp of the piezoelectric layer 2.
- the coupling coefficient of the gap region is significantly reduced compared to the coupling coefficient of the intersection region C.
- FIG. As a result, excitation of elastic waves in the gap region is inhibited, and leakage of elastic waves can be suppressed.
- the non-piezoelectric region 20B further includes a portion of the piezoelectric layer 2 overlapping the non-piezoelectric body 21 in plan view in the first direction, and the non-piezoelectric body 21B has a thickness ds is greater than the thickness dp of a portion of the piezoelectric layer 2 .
- the coupling coefficient of the gap region is significantly reduced compared to the coupling coefficient of the intersection region C.
- FIG. As a result, excitation of elastic waves in the gap region is inhibited, and leakage of elastic waves can be suppressed.
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Abstract
The present invention suppresses leakage of elastic waves. This elastic wave device comprises: a support member equipped with a support substrate which is thick in a first direction; and an IDT electrode that has a piezoelectric layer provided in the first direction of the support member, a plurality of first electrode fingers provided on a main surface of the piezoelectric layer and extending in a second direction intersecting the first direction, a first busbar electrode to which the plurality of first electrode fingers are connected, a plurality of second electrode fingers lying opposite any of the plurality of first electrode fingers in a third direction orthogonal to the second direction and extending in the second direction, and a second busbar electrode to which the plurality of second electrode fingers are connected. The present invention has, in plan view in the first direction, a non-piezoelectric region containing a non-piezoelectric body in a gap region between at least one of the first electrode fingers and the second busbar electrode, or between at least one of the second electrode fingers and the first busbar electrode.
Description
本開示は、弾性波装置に関する。
The present disclosure relates to elastic wave devices.
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.
特許文献1に示す弾性波装置は、電極指が延びる方向に弾性波の漏洩が生じる可能性があった。
In the elastic wave device shown in Patent Document 1, leakage of elastic waves may occur in the direction in which the electrode fingers extend.
本開示は、上述した課題を解決するものであり、弾性波の漏洩を抑制することを目的とする。
The present disclosure is intended to solve the above-described problems, and aims to suppress leakage of elastic waves.
一態様に係る弾性波装置は、第1方向に厚みを有する支持基板を備える支持部材と、前記支持部材の前記第1方向に設けられた圧電層と、前記圧電層の主面に設けられ、前記第1方向に交差する第2方向に延びる複数の第1電極指と、前記複数の第1電極指が接続された第1のバスバー電極と、前記第2方向に直交する第3方向に前記複数の第1電極指のいずれかと対向し、前記第2方向に延びる複数の第2電極指と、前記複数の第2電極指が接続された第2のバスバー電極と、を有するIDT電極と、を備え、前記第1方向に平面視して、少なくとも1つの第1電極指と前記第2のバスバー電極との間又は少なくとも1つの第2電極指と前記第1のバスバー電極との間のギャップ領域において、非圧電体を含む非圧電性領域を有する。
An elastic wave device according to one aspect includes a support member including a support substrate having a thickness in a first direction, a piezoelectric layer provided in the first direction of the support member, a main surface of the piezoelectric layer provided, a plurality of first electrode fingers extending in a second direction intersecting the first direction; a first busbar electrode to which the plurality of first electrode fingers are connected; an IDT electrode having a plurality of second electrode fingers facing any one of the plurality of first electrode fingers and extending in the second direction; and a second busbar electrode to which the plurality of second electrode fingers are connected; a gap between at least one first electrode finger and the second busbar electrode or between at least one second electrode finger and the first busbar electrode in plan view in the first direction The region has a non-piezoelectric region containing non-piezoelectric material.
本開示によれば、弾性波の漏洩を抑制することができる。
According to the present disclosure, elastic wave leakage can be suppressed.
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。
Below, embodiments of the present disclosure will be described in detail based on the drawings. Note that the present disclosure is not limited by this embodiment. It should be noted that each embodiment described in the present disclosure is an exemplary one, and among different embodiments, a modification that allows partial replacement or combination of configurations, and the first embodiment after the second embodiment A description of matters common to the embodiment will be omitted, and only different points will be described. In particular, similar actions and effects due to similar configurations 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)
1A is a perspective view showing an elastic wave device according to a first embodiment; FIG. FIG. 1B is a plan view showing the electrode structure of the first embodiment.
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)
1A is a perspective view showing an elastic wave device according to a first embodiment; FIG. 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 consist of LiTaO 3 . The cut angle of LiNbO 3 and LiTaO 3 is Z-cut in the first embodiment. The cut angles of LiNbO 3 and LiTaO 3 may be rotated Y-cut or X-cut. Preferably, the Y-propagation and X-propagation ±30° propagation orientations are preferred.
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。
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、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、電極指3及び電極指4が設けられている。
The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b facing each other in the Z direction. Electrode fingers 3 and 4 are provided on the first main surface 2a.
ここで電極指3が「第1電極指」の一例であり、電極指4が「第2電極指」の一例である。図1A及び図1Bでは、複数の電極指3は、第1のバスバー電極5に接続されている複数の「第1電極」である。複数の電極指4は、第2のバスバー電極6に接続されている複数の「第2電極」である。複数の電極指3及び複数の電極指4は、互いに間挿し合っている。これにより、電極指3と、電極指4と、第1のバスバー電極5と、第2のバスバー電極6と、を備えるIDT(Interdigital Transuducer)電極が構成される。
Here, the electrode finger 3 is an example of the "first electrode finger" and the electrode finger 4 is an example of the "second electrode finger". In FIGS. 1A and 1B , the multiple electrode fingers 3 are multiple “first electrodes” connected to the first busbar electrodes 5 . A plurality of electrode fingers 4 are a plurality of “second electrodes” connected to second busbar electrodes 6 . The plurality of electrode fingers 3 and the plurality of electrode fingers 4 are interdigitated with each other. Thus, an IDT (Interdigital Transducer) electrode including electrode fingers 3 , electrode fingers 4 , first busbar electrodes 5 , and second busbar electrodes 6 is configured.
電極指3及び電極指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、電極指3と、電極指3と隣接する電極指4とが対向している。電極指3、電極指4の長さ方向、及び、電極指3、電極指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、電極指3と、電極指3と隣接する電極指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。以下の説明では、圧電層2の厚み方向をZ方向(又は第1方向)とし、電極指3、電極指4の長さ方向をY方向(又は第2方向)とし、電極指3、電極指4の直交する方向をX方向(又は第3方向)として、説明することがある。
The electrode fingers 3 and 4 have a rectangular shape and a length direction. The electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in a direction perpendicular to the length direction. Both the length direction of the electrode fingers 3 and 4 and the direction orthogonal to the length direction of the electrode fingers 3 and 4 are directions that intersect the thickness direction of the piezoelectric layer 2 . Therefore, it can be said that the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2 . In the following description, the thickness direction of the piezoelectric layer 2 is defined as the Z direction (or first direction), the length direction of the electrode fingers 3 and 4 is defined as the Y direction (or second direction), and the electrode fingers 3 and electrode fingers 4 may be described as the X direction (or the third direction).
また、電極指3、電極指4の長さ方向が図1A及び図1Bに示す電極指3、電極指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のバスバー電極5及び第2のバスバー電極6が延びている方向に電極指3、電極指4を延ばしてもよい。その場合、第1のバスバー電極5及び第2のバスバー電極6は、図1A及び図1Bにおいて電極指3、電極指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指3と、他方電位に接続される電極指4とが隣り合う1対の構造が、上記電極指3、電極指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 direction of the electrode fingers 3 and 4 may be interchanged with the direction orthogonal to the length direction of the electrode fingers 3 and 4 shown in FIGS. 1A and 1B. That is, in FIGS. 1A and 1B, the electrode fingers 3 and 4 may extend in the direction in which the first busbar electrodes 5 and the second busbar electrodes 6 extend. In that case, the first busbar electrode 5 and the second busbar electrode 6 extend in the direction in which the electrode fingers 3 and 4 extend in FIGS. 1A and 1B. A pair of structures in which the electrode fingers 3 connected to one potential and the electrode fingers 4 connected to the other potential are adjacent to each other are arranged in a direction perpendicular to the length direction of the electrode fingers 3 and 4. Multiple pairs are provided.
ここで電極指3と電極指4とが隣り合うとは、電極指3と電極指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、電極指3と電極指4とが間隔を介して配置されている場合を指す。また、電極指3と電極指4とが隣り合う場合、電極指3と電極指4との間には、他の電極指3、電極指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 electrode finger 3 and the electrode finger 4 are adjacent to each other, not when the electrode finger 3 and the electrode finger 4 are arranged so as to be in direct contact, but when the electrode finger 3 and the electrode finger 4 are arranged with a gap therebetween. It refers to the case where the When the electrode finger 3 and the electrode finger 4 are adjacent to each other, there are electrodes connected to the hot electrode and the ground electrode, including other electrode fingers 3 and 4, between the electrode finger 3 and the electrode finger 4. is not placed. The logarithms need not be integer pairs, but may be 1.5 pairs, 2.5 pairs, or the like.
電極指3と電極指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、電極指3と電極指4との間の中心間距離とは、電極指3の長さ方向と直交する方向における電極指3の幅寸法の中心と、電極指4の長さ方向と直交する方向における電極指4の幅寸法の中心とを結んだ距離となる。
The center-to-center distance, that is, the pitch, between the electrode fingers 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 electrode fingers 3 and 4 means the center of the width dimension of the electrode fingers 3 in the direction orthogonal to the length direction of the electrode fingers 3 and the distance orthogonal to the length direction of the electrode fingers 4 . It is the distance connecting the center of the width dimension of the electrode finger 4 in the direction of
さらに、電極指3、電極指4の少なくとも一方が複数本ある場合(電極指3、電極指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)、電極指3、電極指4の中心間距離は、1.5対以上の電極指3、電極指4のうち隣り合う電極指3、電極指4それぞれの中心間距離の平均値を指す。
Furthermore, when at least one of the electrode fingers 3 and 4 is plural (when there are 1.5 or more pairs of electrodes when the electrode fingers 3 and 4 are paired as a pair of electrode pairs), the electrode fingers 3. The center-to-center distance of the electrode fingers 4 refers to the average value of the center-to-center distances of adjacent electrode fingers 3 and electrode fingers 4 among 1.5 or more pairs of electrode fingers 3 and electrode fingers 4 .
また、電極指3、電極指4の幅、すなわち電極指3、電極指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、電極指3と電極指4との間の中心間距離とは、電極指3の長さ方向と直交する方向における電極指3の寸法(幅寸法)の中心と、電極指4の長さ方向と直交する方向における電極指4の寸法(幅寸法)の中心とを結んだ距離となる。
Also, the width of the electrode fingers 3 and 4, that is, the dimension in the facing direction of the electrode fingers 3 and 4 is preferably in the range of 150 nm or more and 1000 nm or less. Note that the center-to-center distance between the electrode fingers 3 and 4 is the distance between the center of the dimension (width dimension) of the electrode finger 3 in the direction perpendicular to the length direction of the electrode finger 3 and the length of the electrode finger 4. It is the distance connecting the center of the dimension (width dimension) of the electrode finger 4 in the direction orthogonal to the direction.
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、電極指3、電極指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(電極指3、電極指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。
Also, in the first embodiment, since the Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrode fingers 3 and 4 is the direction orthogonal 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 substantially perpendicular (the angle formed by the direction perpendicular to the length direction of the electrode fingers 3 and electrode fingers 4 and the polarization direction is, for example, 90° ± 10°).
圧電層2の第2の主面2b側には、中間層7を介して支持基板8が積層されている。中間層7及び支持基板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、空間部(エアギャップ)9が形成されている。
A support substrate 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an intermediate layer 7 interposed therebetween. The intermediate layer 7 and the support substrate 8 have a frame shape and, as shown in FIG. 2, openings 7a and 8a. A space (air gap) 9 is thereby formed.
空間部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、上記支持基板8は、少なくとも1対の電極指3、電極指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、支持基板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 space 9 is provided so as not to disturb the vibration of the excitation region C of the piezoelectric layer 2 . Therefore, the support substrate 8 is laminated on the second main surface 2b with the intermediate layer 7 interposed therebetween at a position not overlapping the portion where at least one pair of electrode fingers 3 and 4 are provided. Note that the intermediate layer 7 may not be provided. Therefore, the support substrate 8 can be directly or indirectly laminated to the second main surface 2b of the piezoelectric layer 2 .
中間層7は、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、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 made of silicon oxide. However, the intermediate layer 7 can be formed of an appropriate insulating material other than silicon oxide, such as silicon nitride and alumina.
支持基板8は、Siにより形成されている。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、支持基板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。支持基板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 substrate 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 support substrate 8 can also be constructed using an appropriate insulating material or semiconductor material. Materials for the support substrate 8 include, for example, aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and steer. Various ceramics such as tight and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.
上記複数の電極指3、電極指4及び第1のバスバー電極5、第2のバスバー電極6は、Al、AlCu合金などの適宜の金属又は合金からなる。第1実施形態では、電極指3、電極指4及び第1のバスバー電極5、第2のバスバー電極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 electrode fingers 3, electrode fingers 4, first busbar electrodes 5, and second busbar electrodes 6 are made of appropriate metals or alloys such as Al and AlCu alloys. In the first embodiment, the electrode fingers 3, the electrode fingers 4, the first busbar electrodes 5, and the second busbar electrodes 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、複数の電極指3と、複数の電極指4との間に交流電圧を印加する。より具体的には、第1のバスバー電極5と第2のバスバー電極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 electrode fingers 3 and the multiple electrode fingers 4 . More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 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、複数対の電極指3、電極指4のうちいずれかの隣り合う電極指3、電極指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, and the center-to-center distance between any one of the plurality of pairs of electrode fingers 3 and 4 adjacent to each other is p, d/p is set to 0.5 or less. 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、第1実施形態のように電極指3、電極指4の少なくとも一方が複数本ある場合、すなわち、電極指3、電極指4を1対の電極組とした場合に電極指3、電極指4が1.5対以上ある場合、隣り合う電極指3、電極指4の中心間距離pは、各隣り合う電極指3、電極指4の中心間距離の平均距離となる。
When at least one of the electrode fingers 3 and the electrode fingers 4 is plural as in the first embodiment, that is, when the electrode fingers 3 and the electrode fingers 4 form a pair of electrodes, the electrode fingers 3 and the electrode fingers When there are 1.5 pairs or more of 4, the center-to-center distance p between the adjacent electrode fingers 3 and 4 is the average distance between the center-to-center distances between the adjacent electrode fingers 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、電極指3、電極指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 acoustic wave device 1 of the first embodiment has the above configuration, even if the logarithms of the electrode fingers 3 and 4 are reduced in an attempt 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.
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 Lamb waves propagating through the piezoelectric layer of the comparative example. FIG. 3B is a schematic cross-sectional view for explaining a thickness-shear primary mode bulk wave propagating through the piezoelectric layer of the first embodiment. FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of a thickness-shear primary mode bulk wave propagating in 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3、4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3、4の対数を少なくした場合、Q値が低下する。
FIG. 3A shows an acoustic wave device as described in Patent Document 1, in which Lamb waves propagate through the piezoelectric layer. As shown in FIG. 3A, waves propagate through the piezoelectric layer 201 as indicated by arrows. Here, the piezoelectric layer 201 has a first principal surface 201a and a second principal surface 201b, and the thickness direction connecting the first principal surface 201a and the second principal surface 201b is the Z direction. . The X direction is the direction in which the electrode fingers 3 and 4 of the IDT electrodes are aligned. 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 layer 201 vibrates as a whole, the wave propagates in the X direction, so reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is attempted, that is, when the number of logarithms of the electrode fingers 3 and 4 is reduced, the Q value is lowered.
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、電極指3、電極指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 of the first embodiment, since the vibration displacement is in the thickness sliding direction, the wave is generated between the first main surface 2a and the second main surface 2a of the piezoelectric layer 2. It propagates almost in the direction connecting the surface 2b, that is, in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. 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 electrode fingers 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(図1B参照)に含まれる第1領域251と、励振領域Cに含まれる第2領域252とで逆になる。図4では、電極指3と電極指4との間に、電極指4が電極指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251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252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 direction of the bulk wave of the primary thickness-shear mode is the first region 251 included in the excitation region C (see FIG. 1B) of the piezoelectric layer 2 and the first region 251 included in the excitation region C (see FIG. 1B). 2 area 252 is reversed. FIG. 4 schematically shows bulk waves when a voltage is applied between the electrode fingers 3 so that the electrode fingers 4 have a higher potential than the electrode fingers 3 . The first region 251 is a region of the excitation region C between the virtual plane VP1 that is perpendicular to the thickness direction of the piezoelectric layer 2 and bisects the piezoelectric layer 2 and the first main surface 2a. The second region 252 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、電極指3と電極指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、この電極指3、電極指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 fingers 3 and 4 is arranged. It is not always necessary to have a plurality of pairs of electrode pairs. That is, it is sufficient that at least one pair of electrodes is provided.
例えば、上記電極指3がホット電位に接続される電極であり、電極指4がグラウンド電位に接続される電極である。もっとも、電極指3がグラウンド電位に、電極指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 finger 3 is an electrode connected to a hot potential, and the electrode finger 4 is an electrode connected to a ground potential. However, the electrode finger 3 may be connected to the ground potential and the electrode finger 4 to the hot potential. In the first embodiment, the at least one pair of electrodes are, as described above, electrodes connected to a hot potential or electrodes connected to a ground potential, and no floating electrodes are provided.
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 resonance characteristics of the elastic wave device of the first embodiment. The design parameters of the acoustic wave device 1 that obtained 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: LiNbO3 with Euler angles (0°, 0°, 90°)
Thickness of piezoelectric layer 2: 400 nm
圧電層2の厚み:400nm Piezoelectric layer 2: LiNbO3 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
電極指3、電極指4からなる電極の対数:21対
電極指3と電極指4との間の中心間距離(ピッチ):3μm
電極指3、電極指4の幅:500nm
d/p:0.133 Length of excitation region C (see FIG. 1B): 40 μm
Number of electrode pairs consisting ofelectrode fingers 3 and 4: 21 pairs Center-to-center distance (pitch) between electrode fingers 3 and 4: 3 μm
Width ofelectrode fingers 3 and 4: 500 nm
d/p: 0.133
電極指3、電極指4からなる電極の対数:21対
電極指3と電極指4との間の中心間距離(ピッチ):3μm
電極指3、電極指4の幅:500nm
d/p:0.133 Length of excitation region C (see FIG. 1B): 40 μm
Number of electrode pairs consisting of
Width of
d/p: 0.133
中間層7:1μmの厚みの酸化ケイ素膜
Middle layer 7: Silicon oxide film with a thickness of 1 μm
支持基板8:Si
Support substrate 8: Si
なお、励振領域C(図1B参照)とは、電極指3と電極指4の長さ方向と直交するX方向に視たときに、電極指3と電極指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の電極指3、電極指4の長さ方向に沿う寸法である。ここで、励振領域Cとは、「交差領域」の一例である。
The excitation region C (see FIG. 1B) is a region where the electrode fingers 3 and 4 overlap when viewed in the X direction perpendicular to the length direction of the electrode fingers 3 and 4. . The length of the excitation region C is the dimension along the length direction of the electrode fingers 3 and 4 of the excitation region C. As shown in FIG. Here, the excitation region C is an example of the "intersection region".
第1実施形態では、電極指3、電極指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、電極指3と電極指4とを等ピッチで配置した。
In the first embodiment, the inter-electrode distances of the electrode pairs consisting of the electrode fingers 3 and 4 are all equal in a plurality of pairs. That is, the electrode fingers 3 and the electrode fingers 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 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、電極指3と電極指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 center-to-center distance between the electrode fingers 3 and 4 is p, in the first 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、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2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。
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. In the elastic wave device of the first embodiment, FIG. 6 shows d/2p, where p is the center-to-center distance between adjacent electrodes or the average distance of the center-to-center distances, and d is the average thickness of the piezoelectric layer 2. It is an explanatory view showing the relationship with the fractional bandwidth as.
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、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, even if d/p is adjusted, the fractional bandwidth is less than 5%. On the other hand, when d/2p≦0.25, that is, when d/p≦0.5, the specific 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, it is possible to construct a resonator having a high coupling coefficient using the thickness-shear primary mode bulk wave.
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、隣り合う電極指3、電極指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、隣り合う電極指3、電極指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 the above p is the center-to-center distance between adjacent electrode fingers 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 electrode fingers 3 and 4 should be p.
また、圧電層2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 2, if the piezoelectric layer 2 has variations in thickness, 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101では、圧電層2の第1の主面2a上において、電極指3と電極指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。この場合でも、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 are provided in the elastic wave device of the first embodiment. In elastic wave device 101 , a pair of electrodes having electrode fingers 3 and 4 are 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 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、複数の電極指3、電極指4において、いずれかの隣り合う電極指3、電極指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Cに対する、上記隣り合う電極指3、電極指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。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。これを、図8及び図9を参照して説明する。
In the elastic wave device 1, preferably, the excitation region is an overlapping region of the plurality of electrode fingers 3 and 4 when viewed in the direction in which any adjacent electrode fingers 3 and 4 are facing each other. It is desirable that the metallization ratio MR of the adjacent electrode fingers 3 and 4 with respect to the region C satisfies MR≦1.75(d/p)+0.075. In that case, spurious can be effectively reduced. This will be described with reference to FIGS. 8 and 9. FIG.
図8は、第1実施形態の弾性波装置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***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。
FIG. 8 is a reference diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment. 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対の電極指3、電極指4に着目した場合、この1対の電極指3、電極指4のみが設けられるとする。この場合、一点鎖線で囲まれた部分が励振領域Cとなる。この励振領域Cとは、電極指3と電極指4とを、電極指3、電極指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指3における電極指4と重なり合っている領域、電極指4における電極指3と重なり合っている領域、及び、電極指3と電極指4との間の領域における電極指3と電極指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Cの面積に対する、励振領域C内の電極指3、電極指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C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 electrode fingers 3 and 4, it is assumed that only the pair of electrode fingers 3 and 4 are provided. In this case, the excitation region C is the portion surrounded by the dashed-dotted line. The excitation region C is a region where the electrode fingers 3 and 4 overlap with the electrode fingers 4 when viewed in a direction perpendicular to the length direction of the electrode fingers 3 and 4, that is, in a facing direction. a region where the electrode fingers 3 overlap each other; and a region between the electrode fingers 3 and 4 where the electrode fingers 3 and 4 overlap each other. The area of the electrode fingers 3 and 4 in the excitation region C with respect to the area of the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallization portion to the area of the excitation region C.
なお、複数対の電極指3、電極指4が設けられている場合、励振領域Cの面積の合計に対する全励振領域C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 electrode fingers 3 and 4 are provided, the ratio of the metallization portion included in the entire excitation region C to the total area of the excitation region C should be MR.
図9は、第1実施形態の弾性波装置の、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説明図である。なお、比帯域については、圧電層2の膜厚や電極指3、電極指4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2を用いた場合の結果であるが、他のカット角の圧電層2を用いた場合においても、同様の傾向となる。
FIG. 9 shows the ratio bandwidth when a large number of elastic wave resonators are configured in the elastic wave device of the first embodiment, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. is an explanatory diagram showing the relationship between. The ratio band was adjusted by changing the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4 in various ways. FIG. 9 shows the results when the piezoelectric layer 2 made of Z-cut LiNbO 3 is used, but the same tendency is obtained when the piezoelectric layer 2 with other cut angles is 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の膜厚や電極指3、電極指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 changes the parameters constituting the fractional band, even if the passband appear within. 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 electrode fingers 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説明図である。第1実施形態の弾性波装置1において、d/2pと、MRが異なる様々な弾性波装置1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 an explanatory diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth. In the elastic wave device 1 of the first embodiment, various elastic wave devices 1 with different d/2p and MR were configured, 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説明図である。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る。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 an explanatory diagram showing a map of the fractional band with respect to the Euler angles (0°, θ, ψ) of LiNbO 3 when d/p is infinitely close to 0. FIG. A hatched portion in FIG. 11 is a region where a fractional bandwidth of at least 5% or more is obtained. When the range of the area is approximated, it becomes the range represented by the following formulas (1), (2) and (3).
(0°±10°、0°~20°、任意のψ) …式(1)
(0°±10°、20°~80°、0°~60°(1-(θ-50)2/900)1/2)又は(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) (0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) 2 /900) 1/2 ] ~ 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
(0°±10°、20°~80°、0°~60°(1-(θ-50)2/900)1/2)又は(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) (0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) 2 /900) 1/2 ] ~ 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
従って、上記式(1)、式(2)又は式(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、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。低音響インピーダンス層は、例えばSiO2の層であり、高音響インピーダンス層は、例えばW、Pt等の金属層又はAlN、SiN等の誘電体層である。音響多層膜42を用いた場合、弾性波装置1における空間部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. 12 is a modification of the first embodiment, and is a cross-sectional view of a portion taken along line II-II of FIG. 1A. In the acoustic wave device 41 , an acoustic multilayer film 42 is laminated on the second main surface 2 b of the piezoelectric layer 2 . The acoustic multilayer film 42 has a laminated structure of low acoustic impedance layers 42a, 42c, 42e with relatively low acoustic impedance and high acoustic impedance layers 42b, 42d with relatively high acoustic impedance. The low acoustic impedance layer is, for example, a layer of SiO2 , and the high acoustic impedance layer is, for example, a metal layer such as W, Pt or a dielectric layer such as AlN, SiN. When the acoustic multilayer film 42 is used, the thickness-shear primary mode bulk wave can be confined in the piezoelectric layer 2 without using the space 9 in the elastic wave device 1 . Also in the acoustic wave device 41, by setting the above d/p to 0.5 or less, it is possible to obtain resonance characteristics based on bulk waves in the first-order thickness shear mode. In the acoustic multilayer film 42, the number of lamination of the low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b, 42d is not particularly limited. At least one of the high acoustic impedance layers 42b, 42d needs to be arranged 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、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、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 appropriate materials as long as the acoustic impedance relationship is satisfied. Examples of materials for the low acoustic impedance layers 42a, 42c, and 42e include silicon oxide and silicon oxynitride. Materials for the high acoustic impedance layers 42b and 42d include alumina, silicon nitride, and metals.
図13は、本開示の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である。図13において、空間部9の外周縁を破線で示す。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。この場合、図12に示すように、弾性波装置301は、反射器310、311を有する。反射器310、311は、圧電層2の電極指3、4の弾性波伝搬方向両側に設けられる。弾性波装置301では、空間部9上の電極指3、4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。このとき、反射器310、311が両側に設けられているため、板波としてのラム波による共振特性を得ることができる。
FIG. 13 is a partially cutaway perspective view for explaining the elastic wave device according to the embodiment of the present disclosure. In FIG. 13, the outer peripheral edge of the space portion 9 is indicated by a dashed line. The elastic wave device of the present disclosure may utilize plate waves. In this case, the elastic wave device 301 has reflectors 310 and 311 as shown in FIG. Reflectors 310 and 311 are provided on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the acoustic wave propagation direction. In the elastic wave device 301, a Lamb wave as a plate wave is excited by applying an AC electric field to the electrode fingers 3 and 4 on the space 9. FIG. At this time, since the reflectors 310 and 311 are provided on both sides, it is possible to obtain resonance characteristics due to Lamb waves as Lamb waves.
以上説明したように、弾性波装置1、101では、厚み滑り1次モードのバルク波が利用されている。また、弾性波装置1、101では、第1電極指3及び第2電極指4は隣り合う電極同士であり、圧電層2の厚みをd、第1電極指3及び第2電極指4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、弾性波装置が小型化しても、Q値を高めることができる。
As described above, the elastic wave devices 1 and 101 use bulk waves in the primary mode of thickness shear. In the elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes, the thickness of the piezoelectric layer 2 is d, and the center of the first electrode finger 3 and the second electrode finger 4 is d/p is set to 0.5 or less, where p is the distance between them. As a result, the Q value can be increased even if the elastic wave device is miniaturized.
弾性波装置1、101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電極指3及び第2電極指4があり、第1電極指3及び第2電極指4の上を保護膜で覆うことが望ましい。
In the elastic wave devices 1 and 101, the piezoelectric layer 2 is made of lithium niobate or lithium tantalate. The first principal surface 2a or the second principal surface 2b of the piezoelectric layer 2 has first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2. It is desirable to cover the finger 3 and the second electrode finger 4 with a protective film.
図14は、第1実施形態に係る弾性波装置の一例を示す平面図である。図15は、図14のXV-XV線の断面図である。第1実施形態に係る弾性波装置1Aは、圧電層2と、電極指3,4及びバスバー電極5、6を備えるIDT電極と、支持部材とを備える。
FIG. 14 is a plan view showing an example of the elastic wave device according to the first embodiment. 15 is a cross-sectional view taken along line XV-XV of FIG. 14. FIG. An acoustic wave device 1A according to the first embodiment includes a piezoelectric layer 2, IDT electrodes including electrode fingers 3 and 4 and busbar electrodes 5 and 6, and a support member.
支持部材は、支持基板8を備える部材である。第1実施形態では、支持部材は、支持基板8からなる。第1実施形態において、圧電層2は、支持基板8のZ方向に設けられる。なお、支持部材は、支持基板8のZ方向に設けられた中間層7をさらに備えてもよい。支持部材には、Z方向に平面視して、IDT電極と少なくとも一部が重なる位置に空間部9がある。図15の例では、空間部9は、支持基板8をZ方向に貫通するように設けられるが、あくまで一例であり、支持部材の圧電層2側のみに設けられるものであってもよい。
The support member is a member provided with the support substrate 8 . In the first embodiment, the support member consists of a support substrate 8 . In the first embodiment, the piezoelectric layer 2 is provided on the support substrate 8 in the Z direction. Note that the support member may further include an intermediate layer 7 provided in the Z direction of the support substrate 8 . The support member has a space portion 9 at a position at least partially overlapping with the IDT electrode when viewed from above in the Z direction. In the example of FIG. 15, the space 9 is provided so as to penetrate the support substrate 8 in the Z direction, but this is only an example, and may be provided only on the piezoelectric layer 2 side of the support member.
圧電層2は、支持部材のZ方向に設けられる。第1実施形態において、圧電層2は、圧電性を有するニオブ酸リチウム及び不可避不純物を含む層であり、例えば、単結晶のZカットのニオブ酸リチウムである。
The piezoelectric layer 2 is provided in the Z direction of the support member. In the first embodiment, the piezoelectric layer 2 is a layer containing piezoelectric lithium niobate and unavoidable impurities, and is, for example, single crystal Z-cut lithium niobate.
ここで、厚み滑り1次モードのバルク弾性波を利用する弾性波装置では、圧電層2の面で弾性波が漏洩する可能性がある。弾性波の漏洩は、電極指3、4の延びる方向(Y方向)で大きくなる。また、圧電層2がZカットであって、第2オイラー角θが、-15°以上+15°以下となっている場合、弾性波がより漏洩する可能性がある。
Here, in an elastic wave device that utilizes bulk elastic waves in the primary mode of thickness shear, there is a possibility that the elastic waves will leak on the surface of the piezoelectric layer 2 . Elastic wave leakage increases in the direction in which the electrode fingers 3 and 4 extend (Y direction). Further, when the piezoelectric layer 2 is Z-cut and the second Euler angle θ is -15° or more and +15° or less, more elastic waves may leak.
本発明者は、厚み滑り1次モードのバルク弾性波を利用する弾性波装置について、交差領域CのY方向の外側で、弾性波の漏洩のモードが生じ、第1のバスバー電極5又は第2のバスバー電極6のY方向の外側に、弾性波の漏洩のモードが発生することを見出した。このことから、本発明者は、鋭意研究の結果、ギャップ領域に非圧電性領域20を設けることで、弾性波の漏洩を抑制できることを想起した。ギャップ領域とは、第1電極指3と第2のバスバー電極6とのY方向の間又は第2電極指4と第1のバスバー電極5とのY方向の間の領域を指す。以下、非圧電性領域20について説明する。
The present inventors have found that in an elastic wave device that utilizes a thickness-shear first-order bulk elastic wave, an elastic wave leakage mode is generated outside the intersection region C in the Y direction, and the first bus bar electrode 5 or the second bus bar electrode 5 It was found that an elastic wave leakage mode occurs outside the busbar electrodes 6 in the Y direction. As a result of extensive research, the inventors of the present invention found that the leakage of elastic waves can be suppressed by providing the non-piezoelectric region 20 in the gap region. The gap region refers to a region between the first electrode fingers 3 and the second busbar electrodes 6 in the Y direction or between the second electrode fingers 4 and the first busbar electrodes 5 in the Y direction. The non-piezoelectric region 20 will be described below.
非圧電性領域20は、Z方向に平面視して、非圧電体21を含む領域である。より詳しくは、非圧電性領域20とは、非圧電体21と、Z方向に平面視して、非圧電体21と重なる圧電層2の部分からなる領域である。第1実施形態では、非圧電性領域20は、非圧電体21からなる領域である。非圧電性領域20は、ギャップ領域にある。第1実施形態では、非圧電性領域20は、バスバー電極5、6と、交差領域Cとの、Y方向の間の領域にある。これにより、ギャップ領域での弾性波の励振が阻害されるので、弾性波の漏洩を抑制できる。
The non-piezoelectric region 20 is a region including the non-piezoelectric body 21 when viewed in plan in the Z direction. More specifically, the non-piezoelectric region 20 is a region composed of the non-piezoelectric body 21 and the portion of the piezoelectric layer 2 that overlaps the non-piezoelectric body 21 in plan view in the Z direction. In the first embodiment, the non-piezoelectric region 20 is a region made of a non-piezoelectric material 21 . A non-piezoelectric region 20 is in the gap region. In the first embodiment, the non-piezoelectric region 20 is in the region between the busbar electrodes 5, 6 and the intersection region C in the Y direction. As a result, excitation of elastic waves in the gap region is inhibited, so leakage of elastic waves can be suppressed.
非圧電体21は、圧電性を全く呈さない材料、又は、圧電性が小さい材料である。より詳しくは、非圧電体21とは、圧電定数e15の絶対値が、交差領域Cにおける圧電層2に対して、50%以下である材料をいう。第1実施形態では、非圧電体21は、圧電層2をZ方向に貫通するように設けられる。
The non-piezoelectric material 21 is a material that does not exhibit piezoelectricity at all, or a material with low piezoelectricity. More specifically, the non-piezoelectric material 21 refers to a material whose absolute value of the piezoelectric constant e15 is 50% or less with respect to the piezoelectric layer 2 in the intersection region C. In the first embodiment, the non-piezoelectric body 21 is provided so as to penetrate the piezoelectric layer 2 in the Z direction.
第1実施形態では、非圧電体21は、交差領域Cにおける圧電層2と同種の材料の結晶性及び配向性が圧電層2より低い材料であり、例えば、ニオブ酸リチウムの非単結晶である。ここで、非単結晶とは、多結晶、アモルファス、又は、多結晶とアモルファスとの中間の状態にある結晶をいう。これにより、非圧電体21の電気機械結合係数を、圧電層2の電気機械結合係数よりも小さくすることができる。したがって、材料の圧電性及び配向性は、電気機械結合係数に依存するので、非圧電体21の圧電性及び配向性を、圧電層2より小さくすることができる。これにより、非圧電体21の圧電性を抑制し、弾性波の漏洩をより抑制できる。
In the first embodiment, the non-piezoelectric material 21 is a material similar to that of the piezoelectric layer 2 in the intersection region C and having lower crystallinity and orientation than the piezoelectric layer 2, such as non-single crystal lithium niobate. . Here, non-single crystal refers to polycrystal, amorphous, or a crystal in an intermediate state between polycrystal and amorphous. Thereby, the electromechanical coupling coefficient of the non-piezoelectric body 21 can be made smaller than the electromechanical coupling coefficient of the piezoelectric layer 2 . Therefore, since the piezoelectricity and orientation of the material depend on the electromechanical coupling coefficient, the piezoelectricity and orientation of the non-piezoelectric body 21 can be made smaller than those of the piezoelectric layer 2 . Thereby, the piezoelectricity of the non-piezoelectric body 21 can be suppressed, and the leakage of elastic waves can be further suppressed.
非圧電体21は、好ましくは、無配向である。この場合、非圧電体21の電気機械結合係数を、圧電層2の電気機械結合係数よりもより確実に小さくすることができる。したがって、非圧電体21の圧電定数を、圧電層2の圧電定数よりもより確実に小さくすることができる。
The non-piezoelectric material 21 is preferably non-oriented. In this case, the electromechanical coupling coefficient of the non-piezoelectric body 21 can be made smaller than the electromechanical coupling coefficient of the piezoelectric layer 2 more reliably. Therefore, the piezoelectric constant of the non-piezoelectric body 21 can be made smaller than the piezoelectric constant of the piezoelectric layer 2 more reliably.
なお、非圧電体21は、圧電層2と同種の材料の非結晶体に限られない。非圧電体21は、例えば、圧電層2の材料を部分的に分極反転させたものであってもよい。この場合、非圧電体21の圧電性を抑制することができる。また、非圧電体21は、圧電層2と異なる材料であってもよい。非圧電体21は、例えば、特定元素のイオン注入を行い、ダメージを与えたニオブ酸リチウムであってもよい。ここで、特定元素は、例えば、水素、ヘリウム等である。この場合、非圧電体21を非単結晶にすることができるので、非圧電体21の圧電性を抑制することができる。
It should be noted that the non-piezoelectric material 21 is not limited to the amorphous material of the same kind as the piezoelectric layer 2 . The non-piezoelectric material 21 may be, for example, a material obtained by partially reversing the polarization of the material of the piezoelectric layer 2 . In this case, the piezoelectricity of the non-piezoelectric body 21 can be suppressed. Also, the non-piezoelectric material 21 may be made of a material different from that of the piezoelectric layer 2 . The non-piezoelectric body 21 may be, for example, lithium niobate that is damaged by ion implantation of a specific element. Here, the specific element is, for example, hydrogen, helium, or the like. In this case, the non-piezoelectric material 21 can be non-single-crystal, so that the piezoelectricity of the non-piezoelectric material 21 can be suppressed.
図16は、第1実施形態に係る弾性波装置のアドミタンス特性の一例を示す説明図である。図16において、実施例は、第1実施形態に係る弾性波装置1Aであり、比較例は、非圧電性領域20を有さない弾性波装置である。図16に示すように、実施例に係る弾性波装置は、比較例に係る弾性波装置より、共振周波数におけるピーク幅が狭くなっているため、伝搬ロスが抑制されており、弾性波の漏洩が抑制されていることがわかる。
FIG. 16 is an explanatory diagram showing an example of admittance characteristics of the elastic wave device according to the first embodiment. In FIG. 16 , the example is the elastic wave device 1A according to the first embodiment, and the comparative example is the elastic wave device without the non-piezoelectric region 20 . As shown in FIG. 16, the elastic wave device according to the example has a narrower peak width at the resonance frequency than the elastic wave device according to the comparative example, so propagation loss is suppressed, and elastic wave leakage is suppressed. found to be suppressed.
以上説明したように、第1実施形態に係る弾性波装置1Aは、第1方向に厚みを有する支持基板8を備える支持部材と、支持部材の第1方向に設けられた圧電層2と、圧電層2の主面(第1の主面2a)に設けられ、第1方向に交差する第2方向に延びる複数の第1電極指3と、複数の第1電極指3が接続された第1のバスバー電極5と、第2方向に直交する第3方向に複数の第1電極指3のいずれかと対向し、第2方向に延びる複数の第2電極指4と、複数の第2電極指4が接続された第2のバスバー電極6と、を有するIDT電極と、を備え、第1方向に平面視して、少なくとも1つの第1電極指3と第2のバスバー電極6との間又は少なくとも1つの第2電極指4と第1のバスバー電極5との間のギャップ領域において、非圧電体21を含む非圧電性領域20を有する。
As described above, the acoustic wave device 1A according to the first embodiment includes a support member including the support substrate 8 having a thickness in the first direction, the piezoelectric layer 2 provided in the first direction of the support member, and the piezoelectric layer 2 provided in the first direction. A plurality of first electrode fingers 3 provided on the main surface (first main surface 2a) of the layer 2 and extending in a second direction intersecting the first direction; , a plurality of second electrode fingers 4 facing any one of the plurality of first electrode fingers 3 in a third direction orthogonal to the second direction and extending in the second direction, and a plurality of second electrode fingers 4 and an IDT electrode having a second busbar electrode 6 to which is connected, and when viewed in the first direction, between at least one first electrode finger 3 and the second busbar electrode 6 A non-piezoelectric region 20 containing a non-piezoelectric body 21 is provided in the gap region between one second electrode finger 4 and the first busbar electrode 5 .
これにより、ギャップ領域における弾性波の励振が阻害され、弾性波の漏洩のモードの発生が抑制されるので、弾性波の漏洩を抑制できる。
As a result, the excitation of elastic waves in the gap region is inhibited, and the generation of modes of leakage of elastic waves is suppressed, so that leakage of elastic waves can be suppressed.
また、第1方向に平面視して、非圧電性領域20は、第1電極指3又は第2電極指4と重なる。この場合でも、弾性波の漏洩を抑制できる。
In addition, the non-piezoelectric region 20 overlaps the first electrode finger 3 or the second electrode finger 4 when viewed in plan in the first direction. Even in this case, leakage of elastic waves can be suppressed.
また、第1方向に平面視して、IDT電極と少なくとも一部が重なる位置に空間部9を構成するように配置されている。これにより、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。
Further, it is arranged so as to form a space portion 9 at a position at least partially overlapping with the IDT electrode when viewed in plan in the first direction. As a result, the thickness-shear primary mode bulk wave can be confined within the piezoelectric layer 2 .
また、支持部材は、圧電層2側に、圧電層2よりも低い音響インピーダンスを有する1以上の低音響インピーダンス層42a、42c、42eと、圧電層2よりも高い音響インピーダンスを有する1以上の高音響インピーダンス層42b、42dと、を含む音響反射層(音響多層膜42)を有する。これにより、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。
Further, the supporting member includes, on the piezoelectric layer 2 side, one or more low acoustic impedance layers 42a, 42c, and 42e having an acoustic impedance lower than that of the piezoelectric layer 2 and one or more high acoustic impedance layers 42a, 42c, and 42e having an acoustic impedance higher than that of the piezoelectric layer 2. It has an acoustic reflection layer (acoustic multilayer film 42) including acoustic impedance layers 42b and 42d. As a result, the thickness-shear primary mode bulk wave can be confined within the piezoelectric layer 2 .
望ましい態様として、圧電層2は、単結晶材料であり、非圧電体21は、単結晶材料が多結晶化した材料、単結晶材料がアモルファス化した材料又は単結晶材料に特定元素のイオンが注入された材料である。これにより、非圧電体21の電気機械結合係数を、圧電層2の電気機械結合係数よりも小さくすることができ、非圧電体21の圧電性及び配向性を、圧電層2より小さくすることができる。これにより、非圧電体21の圧電性を抑制し、弾性波の漏洩をより抑制できる。
In a preferred embodiment, the piezoelectric layer 2 is a single crystal material, and the non-piezoelectric body 21 is a polycrystalline single crystal material, an amorphous single crystal material, or a single crystal material into which ions of a specific element are implanted. It is a material that has been As a result, the electromechanical coupling coefficient of the non-piezoelectric body 21 can be made smaller than the electromechanical coupling coefficient of the piezoelectric layer 2 , and the piezoelectricity and orientation of the non-piezoelectric body 21 can be made smaller than those of the piezoelectric layer 2 . can. Thereby, the piezoelectricity of the non-piezoelectric body 21 can be suppressed, and the leakage of elastic waves can be further suppressed.
また、圧電層2は、Zカットであり、圧電層2の第2オイラー角θは、-15°以上かつ15°以下である。この場合でも、弾性波の漏洩を抑制できる。
The piezoelectric layer 2 is Z-cut, and the second Euler angle θ of the piezoelectric layer 2 is -15° or more and 15° or less. Even in this case, leakage of elastic waves can be suppressed.
望ましい態様として、圧電層2の厚みは、複数の第1電極指3及び複数の第2電極指4のうち、隣り合う第1電極指3と第2電極指4との間の中心間距離をpとした場合に2p以下である。これにより、弾性波装置1を小型化でき、かつQ値を高めることができる。
As a desirable aspect, the thickness of the piezoelectric layer 2 is the center-to-center distance between the adjacent first electrode fingers 3 and the second electrode fingers 4 among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4. It is 2p or less when p. Thereby, the acoustic wave device 1 can be miniaturized and the Q value can be increased.
望ましい態様として、圧電層2が、ニオブ酸リチウム又はタンタル酸リチウムを含む。これにより、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。
As a preferred embodiment, the piezoelectric layer 2 contains lithium niobate or lithium tantalate. As a result, it is possible to provide an elastic wave device capable of obtaining good resonance characteristics.
望ましい態様として、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。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。
As a desirable aspect, it is configured to be able to use bulk waves in the thickness-shlip mode. As a result, it is possible to provide an elastic wave device with a high coupling coefficient and good resonance characteristics.
望ましい態様として、圧電層2の厚みをd、複数の第1電極指3及び複数の第2電極指4のうち、隣り合う第1電極指3と第2電極指4との中心間距離をpとした場合、d/p≦0.5である。これにより、弾性波装置1を小型化でき、かつQ値を高めることができる。
As a desirable mode, the thickness of the piezoelectric layer 2 is d, and the center-to-center distance between the adjacent first electrode fingers 3 and second electrode fingers 4 among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 is p. , d/p≦0.5. Thereby, the acoustic wave device 1 can be miniaturized and the Q value can be increased.
より望ましい態様として、d/pが0.24以下である。これにより、弾性波装置1を小型化でき、かつQ値を高めることができる。
As a more desirable aspect, d/p is 0.24 or less. Thereby, the acoustic wave device 1 can be miniaturized and the Q value can be increased.
望ましい態様として、第3方向に見たときに第1電極指3と第2電極指4とが重なっている領域が励振領域Cであり、励振領域Cに対する、第1電極指3及び第2電極指4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。この場合、比帯域を確実に17%以下にすることができる。
As a desirable mode, the region where the first electrode fingers 3 and the second electrode fingers 4 overlap when viewed in the third direction is the excitation region C, and the first electrode fingers 3 and the second electrode fingers 3 with respect to the excitation region C When the metallization ratio of finger 4 is MR, MR≦1.75(d/p)+0.075 is satisfied. In this case, the fractional bandwidth can be reliably set to 17% or less.
望ましい態様として、圧電層2は、ニオブ酸リチウム又はタンタル酸リチウムであり、ニオブ酸リチウム又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)又は式(3)の範囲にある。この場合、比帯域を十分に広くすることができる。
As a preferred embodiment, the piezoelectric layer 2 is made of lithium niobate or lithium tantalate, and the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate satisfy the following formula (1), formula (2) or It is in the range of formula (3). In this case, the fractional bandwidth can be widened sufficiently.
(0°±10°,0°~20°,任意のψ) …式(1)
(0°±10°,20°~80°,0°~60°(1-(θ-50)2/900)1/2) 又は (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) (0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50)2/900) 1/2 ] ~ 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
(0°±10°,20°~80°,0°~60°(1-(θ-50)2/900)1/2) 又は (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) (0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50)2/900) 1/2 ] ~ 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
(第2実施形態)
図17は、第2実施形態に係る弾性波装置の一例を示す平面図である。図18は、図17のXVIII-XVIII線の断面図である。第2実施形態に係る弾性波装置1Bは、非圧電性領域20Bに圧電性を有する材料を含む点で第1実施形態と異なる。以下、図面を用いて第2実施形態に係る弾性波装置1Bについて説明する。なお、第1実施形態に係る弾性波装置1Aと同様の構成については、符号を付して説明を省略する。 (Second embodiment)
FIG. 17 is a plan view showing an example of the elastic wave device according to the second embodiment. 18 is a cross-sectional view taken along line XVIII-XVIII of FIG. 17. FIG. Anelastic wave device 1B according to the second embodiment differs from the first embodiment in that a non-piezoelectric region 20B contains a piezoelectric material. An elastic wave device 1B according to the second embodiment will be described below with reference to the drawings. In addition, about the structure similar to 1 A of elastic wave apparatuses which concern on 1st Embodiment, the code|symbol is attached|subjected and description is abbreviate|omitted.
図17は、第2実施形態に係る弾性波装置の一例を示す平面図である。図18は、図17のXVIII-XVIII線の断面図である。第2実施形態に係る弾性波装置1Bは、非圧電性領域20Bに圧電性を有する材料を含む点で第1実施形態と異なる。以下、図面を用いて第2実施形態に係る弾性波装置1Bについて説明する。なお、第1実施形態に係る弾性波装置1Aと同様の構成については、符号を付して説明を省略する。 (Second embodiment)
FIG. 17 is a plan view showing an example of the elastic wave device according to the second embodiment. 18 is a cross-sectional view taken along line XVIII-XVIII of FIG. 17. FIG. An
弾性波装置1Bは、バスバー電極5、6と、交差領域Cとの、Y方向の間の領域に、非圧電性領域20Bを有する。第2実施形態において、非圧電性領域20Bは、第1方向に平面視して、電極指3、4と重ならないよう、X方向に間隔を開けて配置されている。
The elastic wave device 1B has a non-piezoelectric region 20B in the region between the busbar electrodes 5, 6 and the intersection region C in the Y direction. In the second embodiment, the non-piezoelectric regions 20B are spaced apart in the X direction so as not to overlap the electrode fingers 3 and 4 when viewed in plan in the first direction.
図18に示すように、第2実施形態では、非圧電性領域20Bは、非圧電体21Bからなる領域と、圧電層2のうち、Z方向に平面視して、非圧電体21Bと重なる領域とからなる。この場合、Z方向に平面視して、非圧電体21Bと重なる領域における圧電定数e15は、交差領域Cにおける圧電材料の圧電定数e15の50%以上である。この場合でも、弾性波の漏洩を抑制できる。
As shown in FIG. 18, in the second embodiment, the non-piezoelectric region 20B includes a region made of the non-piezoelectric body 21B and a region of the piezoelectric layer 2 that overlaps the non-piezoelectric body 21B when viewed in plan in the Z direction. Consists of In this case, the piezoelectric constant e15 in the region overlapping the non-piezoelectric body 21B is 50% or more of the piezoelectric constant e15 of the piezoelectric material in the intersecting region C when viewed in plan in the Z direction. Even in this case, leakage of elastic waves can be suppressed.
第2実施形態では、非圧電体21は、誘電体からなる保護膜であり、例えば、酸化シリコンからなる。この場合、非圧電体21は、Z方向に平面視して、交差領域Cと重ならない位置に設けられる。図18の例では、非圧電体21は、ギャップ領域に設けられる。ここで、非圧電体21Bの厚みをds、圧電層2の厚みをdpとした場合、dsはdpより大きい。すなわち、非圧電体21Bの厚みdsは、非圧電性領域20Bの厚み(ds+dp)に対して50%未満である。これにより、ギャップ領域の結合係数は、交差領域Cにおける圧電層2の結合係数に比べて大幅に低下する。そのため、ギャップ領域での弾性波の励振が阻害されるので、弾性波の漏洩を抑制できる。
In the second embodiment, the non-piezoelectric material 21 is a protective film made of a dielectric material, such as silicon oxide. In this case, the non-piezoelectric body 21 is provided at a position that does not overlap with the intersection region C when viewed from above in the Z direction. In the example of FIG. 18, the non-piezoelectric body 21 is provided in the gap region. Here, when the thickness of the non-piezoelectric body 21B is ds and the thickness of the piezoelectric layer 2 is dp, ds is larger than dp. That is, the thickness ds of the non-piezoelectric body 21B is less than 50% of the thickness (ds+dp) of the non-piezoelectric region 20B. As a result, the coupling coefficient of the gap region is significantly reduced compared to the coupling coefficient of the piezoelectric layer 2 in the intersection region C. FIG. As a result, excitation of elastic waves in the gap region is inhibited, and leakage of elastic waves can be suppressed.
以上説明したように、第2実施形態に係る弾性波装置1Bは、非圧電性領域20Bは、第3方向に間隔をあけて配置されている。この場合でも、弾性波の漏洩を抑制できる。
As described above, in the elastic wave device 1B according to the second embodiment, the non-piezoelectric regions 20B are spaced apart in the third direction. Even in this case, leakage of elastic waves can be suppressed.
また、非圧電体21Bは、酸化シリコンを含む。この場合でも、弾性波の漏洩を抑制できる。
Also, the non-piezoelectric body 21B contains silicon oxide. Even in this case, leakage of elastic waves can be suppressed.
望ましい態様として、非圧電体21Bは、圧電層2に積層され、非圧電体21Bの厚みdsは、圧電層2の厚みdpよりも大きい。これにより、ギャップ領域の結合係数は、交差領域Cの結合係数に比べて大幅に低下する。そのため、ギャップ領域での弾性波の励振が阻害されるので、弾性波の漏洩を抑制できる。
As a desirable mode, the non-piezoelectric body 21B is laminated on the piezoelectric layer 2, and the thickness ds of the non-piezoelectric body 21B is greater than the thickness dp of the piezoelectric layer 2. As a result, the coupling coefficient of the gap region is significantly reduced compared to the coupling coefficient of the intersection region C. FIG. As a result, excitation of elastic waves in the gap region is inhibited, and leakage of elastic waves can be suppressed.
望ましい態様として、非圧電性領域20Bは、第1方向に平面視して、非圧電体21と重なる圧電層2の一部をさらに含み、非圧電性領域20Bにおいて、非圧電体21Bの厚みdsは、圧電層2の一部の厚みdpよりも大きい。これにより、ギャップ領域の結合係数は、交差領域Cの結合係数に比べて大幅に低下する。そのため、ギャップ領域での弾性波の励振が阻害されるので、弾性波の漏洩を抑制できる。
As a preferred embodiment, the non-piezoelectric region 20B further includes a portion of the piezoelectric layer 2 overlapping the non-piezoelectric body 21 in plan view in the first direction, and the non-piezoelectric body 21B has a thickness ds is greater than the thickness dp of a portion of the piezoelectric layer 2 . As a result, the coupling coefficient of the gap region is significantly reduced compared to the coupling coefficient of the intersection region C. FIG. As a result, excitation of elastic waves in the gap region is inhibited, and leakage of elastic waves can be suppressed.
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 embodiments are intended to facilitate understanding of the present disclosure, and are not intended to limit and interpret the present disclosure. This disclosure may be modified/modified without departing from its spirit, and this disclosure also includes equivalents thereof.
1、1A、1B、41、101、301 弾性波装置
2 圧電層
2a 第1の主面
2b 第2の主面
3 電極指(第1電極指)
4 電極指(第2電極指)
5 バスバー電極(第1のバスバー電極)
6 バスバー電極(第2のバスバー電極)
7 中間層
7a 開口部
8 支持基板
8a 開口部
9 空間部
20、20B 非圧電性領域
21、21B 非圧電体
42 音響多層膜
42a、42c、42e 低音響インピーダンス層
42b、42d 高音響インピーダンス層
201 圧電層
201a 第1の主面
201b 第2の主面
251 第1領域
252 第2領域
310、311 反射器
ds、dp 厚み
C 励振領域(交差領域)
VP1 仮想平面 1, 1A, 1B, 41, 101, 301elastic wave device 2 piezoelectric layer 2a first main surface 2b second main surface 3 electrode fingers (first electrode fingers)
4 electrode finger (second electrode finger)
5 busbar electrode (first busbar electrode)
6 busbar electrode (second busbar electrode)
7intermediate layer 7a opening 8 supporting substrate 8a opening 9 space 20, 20B non-piezoelectric regions 21, 21B non-piezoelectric body 42 acoustic multilayer films 42a, 42c, 42e low acoustic impedance layers 42b, 42d high acoustic impedance layer 201 piezoelectric Layer 201a First main surface 201b Second main surface 251 First region 252 Second regions 310, 311 Reflectors ds, dp Thickness C Exciting region (intersection region)
VP1 virtual plane
2 圧電層
2a 第1の主面
2b 第2の主面
3 電極指(第1電極指)
4 電極指(第2電極指)
5 バスバー電極(第1のバスバー電極)
6 バスバー電極(第2のバスバー電極)
7 中間層
7a 開口部
8 支持基板
8a 開口部
9 空間部
20、20B 非圧電性領域
21、21B 非圧電体
42 音響多層膜
42a、42c、42e 低音響インピーダンス層
42b、42d 高音響インピーダンス層
201 圧電層
201a 第1の主面
201b 第2の主面
251 第1領域
252 第2領域
310、311 反射器
ds、dp 厚み
C 励振領域(交差領域)
VP1 仮想平面 1, 1A, 1B, 41, 101, 301
4 electrode finger (second electrode finger)
5 busbar electrode (first busbar electrode)
6 busbar electrode (second busbar electrode)
7
VP1 virtual plane
Claims (17)
- 第1方向に厚みを有する支持基板を備える支持部材と、
前記支持部材の前記第1方向に設けられた圧電層と、
前記圧電層の主面に設けられ、前記第1方向に交差する第2方向に延びる複数の第1電極指と、前記複数の第1電極指が接続された第1のバスバー電極と、前記第2方向に直交する第3方向に前記複数の第1電極指のいずれかと対向し、前記第2方向に延びる複数の第2電極指と、前記複数の第2電極指が接続された第2のバスバー電極と、を有するIDT電極と、を備え、
前記第1方向に平面視して、少なくとも1つの第1電極指と前記第2のバスバー電極との間又は少なくとも1つの第2電極指と前記第1のバスバー電極との間のギャップ領域において、非圧電体を含む非圧電性領域を有する、弾性波装置。 a support member comprising a support substrate having a thickness in a first direction;
a piezoelectric layer provided in the first direction of the support member;
a plurality of first electrode fingers provided on the main surface of the piezoelectric layer and extending in a second direction intersecting the first direction; a first bus bar electrode to which the plurality of first electrode fingers are connected; a plurality of second electrode fingers facing any one of the plurality of first electrode fingers in a third direction orthogonal to the two directions and extending in the second direction; and a second electrode finger connected to the plurality of second electrode fingers. an IDT electrode having a busbar electrode,
In a gap region between at least one first electrode finger and the second busbar electrode or between at least one second electrode finger and the first busbar electrode when viewed in plan in the first direction, An acoustic wave device having a non-piezoelectric region containing a non-piezoelectric material. - 前記第1方向に平面視して、前記非圧電性領域は、前記第1電極指又は前記第2電極指と重なる、請求項1に記載の弾性波装置。 The elastic wave device according to claim 1, wherein the non-piezoelectric region overlaps with the first electrode finger or the second electrode finger when viewed in the first direction.
- 前記第1方向に平面視して、前記非圧電性領域は、前記第3方向に間隔をあけて配置されている、請求項1に記載の弾性波装置。 The elastic wave device according to claim 1, wherein the non-piezoelectric regions are spaced apart in the third direction when viewed in plan in the first direction.
- 前記第1方向に平面視して、前記IDT電極と少なくとも一部が重なる位置に空間部を構成するように配置されている、請求項1から3のいずれか1項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 3, arranged so as to form a space at a position at least partially overlapping with the IDT electrode when viewed in plan in the first direction.
- 前記支持部材は、前記圧電層側に、前記圧電層よりも低い音響インピーダンスを有する1以上の低音響インピーダンス層と、前記圧電層よりも高い音響インピーダンスを有する1以上の高音響インピーダンス層と、を含む音響反射層を有する、請求項1から3のいずれか1項に記載の弾性波装置。 The support member includes, on the piezoelectric layer side, one or more low acoustic impedance layers having an acoustic impedance lower than that of the piezoelectric layer and one or more high acoustic impedance layers having an acoustic impedance higher than that of the piezoelectric layer. 4. An acoustic wave device according to any one of claims 1 to 3, comprising an acoustic reflective layer comprising:
- 前記圧電層は、単結晶材料であり、
前記非圧電体は、前記単結晶材料が多結晶化した材料、前記単結晶材料がアモルファス化した材料又は前記単結晶材料に特定元素のイオンが注入された材料である、請求項1から5のいずれか1項に記載の弾性波装置。 The piezoelectric layer is a single crystal material,
6. The non-piezoelectric material according to any one of claims 1 to 5, wherein the non-piezoelectric material is a material obtained by polycrystallizing the single crystal material, a material obtained by amorphizing the single crystal material, or a material obtained by implanting ions of a specific element into the single crystal material. The elastic wave device according to any one of claims 1 to 3. - 前記非圧電体は、酸化シリコンを含む、請求項1から5のいずれか1項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 5, wherein the non-piezoelectric body contains silicon oxide.
- 前記非圧電体は、前記圧電層に積層され、
前記非圧電体の厚みは、前記圧電層の厚みよりも大きい、請求項7に記載の弾性波装置。 The non-piezoelectric material is laminated on the piezoelectric layer,
The elastic wave device according to claim 7, wherein the thickness of said non-piezoelectric material is greater than the thickness of said piezoelectric layer. - 前記非圧電性領域は、前記第1方向に平面視して、前記非圧電体と重なる前記圧電層の一部をさらに含み、
前記非圧電性領域において、前記非圧電体の厚みは、前記圧電層の一部の厚みよりも大きい、請求項1から8のいずれか1項に記載の弾性波装置。 The non-piezoelectric region further includes a portion of the piezoelectric layer that overlaps the non-piezoelectric body in plan view in the first direction,
The elastic wave device according to any one of claims 1 to 8, wherein the thickness of the non-piezoelectric material in the non-piezoelectric region is greater than the thickness of a portion of the piezoelectric layer. - 前記圧電層は、Zカットであり、
前記圧電層の第2オイラー角θは、-15°以上かつ15°以下である、請求項1から9のいずれか1項に記載の弾性波装置。 The piezoelectric layer is Z-cut,
The elastic wave device according to any one of claims 1 to 9, wherein the second Euler angle θ of the piezoelectric layer is -15° or more and 15° or less. - 前記圧電層の厚みは、前記複数の第1電極指と前記複数の第2電極指のうち、隣り合う第1電極指と第2電極指との間の中心間距離をpとした場合に2p以下である、請求項1から10のいずれか1項に記載の弾性波装置。 The thickness of the piezoelectric layer is 2p, where p is the center-to-center distance between the first electrode fingers and the second electrode fingers that are adjacent to each other among the plurality of first electrode fingers and the plurality of second electrode fingers. The elastic wave device according to any one of claims 1 to 10, wherein:
- 前記圧電層が、ニオブ酸リチウム又はタンタル酸リチウムを含む、請求項1から11のいずれか1項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 11, wherein the piezoelectric layer contains lithium niobate or lithium tantalate.
- 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1から12のいずれか1項に記載の弾性波装置。 The acoustic wave device according to any one of claims 1 to 12, configured to be able to use bulk waves in thickness shear mode.
- 前記圧電層の厚みをd、前記複数の第1電極指と前記複数の第2電極指のうち、隣り合う前記第1電極指と前記第2電極指との中心間距離をpとした場合、d/p≦0.5である、請求項1から13のいずれか1項に記載の弾性波装置。 When the thickness of the piezoelectric layer is d, and the center-to-center distance between the first electrode fingers and the second electrode fingers adjacent to each other among the plurality of first electrode fingers and the plurality of second electrode fingers is p, The elastic wave device according to any one of claims 1 to 13, wherein d/p≤0.5.
- 前記d/pが0.24以下である、請求項14に記載の弾性波装置。 The elastic wave device according to claim 14, wherein said d/p is 0.24 or less.
- 前記第3方向に見たときに前記第1電極指と前記第2電極指とが重なっている領域が励振領域であり、前記励振領域に対する、前記第1電極指及び前記第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、請求項1から15のいずれか1項に記載の弾性波装置。 A region in which the first electrode finger and the second electrode finger overlap when viewed in the third direction is an excitation region, and the first electrode finger and the second electrode finger are metabolized with respect to the excitation region. The elastic wave device according to any one of claims 1 to 15, wherein MR≤1.75(d/p)+0.075 is satisfied when MR is a rise ratio.
- 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であり、前記ニオブ酸リチウム又は前記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)又は式(3)の範囲にある、請求項1から請求項16のいずれか1項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) 又は (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 piezoelectric layer is lithium niobate or lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate are given by the following formula (1), formula (2), or formula ( 17. The elastic wave device according to any one of claims 1 to 16, which falls within the range of 3).
(0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) 2 /900) 1/2 ] ~ 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
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