WO2023199837A1 - Elastic wave device - Google Patents
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- WO2023199837A1 WO2023199837A1 PCT/JP2023/014216 JP2023014216W WO2023199837A1 WO 2023199837 A1 WO2023199837 A1 WO 2023199837A1 JP 2023014216 W JP2023014216 W JP 2023014216W WO 2023199837 A1 WO2023199837 A1 WO 2023199837A1
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- substrate
- piezoelectric layer
- electrode
- wave device
- electrodes
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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
- H03H9/25—Constructional features of resonators using surface acoustic waves
Definitions
- the present invention relates to an elastic wave device.
- acoustic wave devices including a piezoelectric layer made of lithium niobate or lithium tantalate are known.
- Patent Document 1 discloses a support in which a cavity is formed, a piezoelectric substrate provided on the support so as to overlap with the cavity, and a piezoelectric substrate provided on the piezoelectric substrate so as to overlap with the cavity.
- An acoustic wave device is provided with an IDT (Interdigital Transducer) electrode provided, and a plate wave is excited by the IDT electrode, wherein an edge of the cavity portion is provided with a plate wave excited by the IDT electrode.
- An elastic wave device is disclosed that does not include a straight portion extending parallel to the propagation direction of the wave.
- a support substrate is made of silicon (Si)
- the material of the support substrate and the material of the piezoelectric substrate are Since the coefficients of linear expansion are different, stress is applied to the piezoelectric layer above the cavity, and there is a risk that cracks may occur in the piezoelectric layer.
- An object of the present invention is to provide an elastic wave device that can prevent cracks from occurring in a piezoelectric layer.
- the elastic wave device of the present invention includes a support member having a cavity on one main surface, a piezoelectric layer provided on the one main surface of the support member so as to cover the cavity, and at least one of the piezoelectric layers.
- a functional electrode is provided on the main surface so that at least a portion thereof overlaps with the cavity when viewed from the thickness direction of the piezoelectric layer.
- the support member includes a first substrate and an intermediate layer provided between the first substrate and the piezoelectric layer. The support member contains the same kind of material as the piezoelectric layer.
- an acoustic wave device that can prevent cracks from occurring in the piezoelectric layer.
- FIG. 1 is a cross-sectional view schematically showing an example of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a cross-sectional view showing a calculation model of the elastic wave device.
- FIG. 3 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG. 2.
- FIG. 4 is a plan view showing the relationship between the Y direction shown in FIG. 2 and functional electrodes.
- FIG. 5 is a graph showing the dependence of the coefficient of linear expansion in the X direction on the maximum principal stress of the portion indicated by the arrow in FIG.
- FIG. 6 is a graph showing the dependence of the linear expansion coefficient in the X direction on the reduction rate of the relative maximum principal stress.
- FIG. 5 is a graph showing the dependence of the coefficient of linear expansion in the X direction on the maximum principal stress of the portion indicated by the arrow in FIG.
- FIG. 6 is a graph showing the dependence of the linear expansion coefficient in the X direction on the reduction rate of the relative maximum
- FIG. 7 is a graph showing the relationship between the coefficient of linear expansion in the X direction and the cut angle of the piezoelectric layer.
- FIG. 8 is a cross-sectional view schematically showing an example of the process of forming a sacrificial layer on a piezoelectric substrate.
- FIG. 9 is a cross-sectional view schematically showing an example of the process of forming the intermediate layer.
- FIG. 10 is a cross-sectional view schematically showing an example of the process of bonding the first substrate to the intermediate layer.
- FIG. 11 is a cross-sectional view schematically showing an example of a process of thinning a piezoelectric substrate.
- FIG. 12 is a cross-sectional view schematically showing an example of the process of forming functional electrodes, busbar electrodes, and wiring electrodes.
- FIG. 13 is a cross-sectional view schematically showing an example of the process of forming a through hole.
- FIG. 14 is a cross-sectional view schematically showing an example of the process of removing the sacrificial layer.
- FIG. 15 is a cross-sectional view schematically showing another example of the elastic wave device according to the first embodiment of the present invention.
- FIG. 16 is a cross-sectional view schematically showing an example of an elastic wave device according to a second embodiment of the present invention.
- FIG. 17 is a cross-sectional view schematically showing another example of the elastic wave device according to the second embodiment of the present invention.
- FIG. 18 is a cross-sectional view schematically showing still another example of the elastic wave device according to the second embodiment of the present invention.
- FIG. 19 is a sectional view schematically showing a first modification of the elastic wave device according to the first embodiment of the present invention.
- FIG. 20 is a sectional view schematically showing a second modification of the elastic wave device according to the first embodiment of the present invention.
- 21A to 21E are cross-sectional views schematically showing an example of a method of forming a cavity on the first substrate side of the support member.
- FIG. 22 is a schematic perspective view showing the appearance of an example of an elastic wave device that utilizes bulk waves in thickness shear mode.
- FIG. 23 is a plan view showing the electrode structure on the piezoelectric layer of the acoustic wave device shown in FIG.
- FIG. 24 is a cross-sectional view of a portion taken along line AA in FIG. 22.
- FIG. 25 is a schematic front sectional view for explaining Lamb waves propagating through the piezoelectric film of the acoustic wave device.
- FIG. 26 is a schematic front sectional view for explaining a thickness shear mode bulk wave propagating through a piezoelectric layer of an elastic wave device.
- FIG. 27 is a diagram showing the amplitude direction of the bulk wave in the thickness shear mode.
- FIG. 28 is a diagram showing an example of resonance characteristics of the elastic wave device shown in FIG. 22.
- FIG. 29 is a diagram showing the relationship between d/2p and the fractional band as a resonator of an acoustic wave device, where p is the distance between the centers of adjacent electrodes and d is the thickness of the piezoelectric layer.
- FIG. 30 is a plan view of another example of an elastic wave device that uses thickness-shear mode bulk waves.
- FIG. 31 is a reference diagram showing an example of the resonance characteristics of the elastic wave device shown in FIG. 22.
- FIG. 32 is a diagram showing the relationship between the fractional band and the amount of phase rotation of spurious impedance normalized by 180 degrees as the magnitude of spurious when a large number of elastic wave resonators are configured according to the present embodiment. It is.
- FIG. 33 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional band.
- FIG. 34 is a diagram showing a map of fractional bands with respect to Euler angles (0°, ⁇ , ⁇ ) of LiNbO 3 when d/p is brought as close to 0 as possible.
- FIG. 35 is a partially cutaway perspective view for explaining an example of an elastic wave device that uses Lamb waves.
- FIG. 36 is a cross-sectional view schematically showing an example of an elastic wave device that uses bulk waves.
- the acoustic wave device of the present invention includes a piezoelectric layer made of lithium niobate or lithium tantalate, a first electrode and a first electrode facing each other in a direction crossing the thickness direction of the piezoelectric layer. 2 electrodes.
- a bulk wave in a thickness shear mode such as a primary thickness shear mode is used.
- the first electrode and the second electrode are adjacent electrodes, and when the thickness of the piezoelectric layer is d and the distance between the centers of the first electrode and the second electrode is p, d/ p is set to be 0.5 or less.
- the Q value can be increased even when miniaturization is promoted.
- Lamb waves are used as plate waves. Then, resonance characteristics due to the Lamb wave described above can be obtained.
- the acoustic wave device of the present invention includes a piezoelectric layer made of lithium niobate or lithium tantalate, and an upper electrode and a lower electrode that face each other in the thickness direction of the piezoelectric layer with the piezoelectric layer in between.
- bulk waves are utilized.
- FIG. 1 is a cross-sectional view schematically showing an example of an elastic wave device according to a first embodiment of the present invention.
- the elastic wave device 10 shown in FIG. 1 includes a support member 20, a piezoelectric layer 21, and a functional electrode 22.
- the support member 20 has a cavity 23 on one main surface (the upper main surface in FIG. 1).
- the piezoelectric layer 21 is provided on one main surface of the support member 20 so as to cover the cavity 23.
- the piezoelectric layer 21 is made of, for example, lithium niobate (LiNbO x ) or lithium tantalate (LiTaO x ). In that case, the piezoelectric layer 21 may be composed of LiNbO 3 or LiTaO 3 .
- the functional electrode 22 is provided on at least one main surface of the piezoelectric layer 21.
- the functional electrode 22 is provided on one main surface (the upper main surface in FIG. 1) of the piezoelectric layer 21.
- the functional electrode 22 is provided so that at least a portion thereof overlaps with the cavity 23 when viewed from the thickness direction of the piezoelectric layer 21 (vertical direction in FIG. 1).
- the functional electrode 22 may be provided so that the entirety thereof overlaps with the cavity 23, or a part of the functional electrode 22 may be provided so as to overlap with the cavity 23. .
- the functional electrode 22 is, for example, an IDT electrode provided on one main surface of the piezoelectric layer 21.
- the functional electrode 22 is connected to a busbar electrode and wiring electrode 24, and a two-layer wiring 25.
- the support member 20 includes a first substrate 31 and an intermediate layer (also referred to as a bonding layer or an insulating layer) 41 provided between the first substrate 31 and the piezoelectric layer 21.
- the intermediate layer 41 is made of silicon oxide (SiO x ) such as silicon dioxide (SiO 2 ), for example.
- the cavity 23 may or may not penetrate the support member 20 in the thickness direction (vertical direction in FIG. 1).
- the cavity 23 may be provided so as to penetrate the intermediate layer 41 in the thickness direction, or the cavity 23 may be provided so as not to penetrate the intermediate layer 41 in the thickness direction.
- the support member 20 contains the same kind of material as the piezoelectric layer 21.
- the term "materials of the same kind” includes not only cases where the materials are completely the same, but also cases where the crystallinity or orientation is different, and cases where the presence or absence or concentration of additives is different. The same applies to the following.
- the piezoelectric layer 21 on which the functional electrode 22 is provided with the support member 20 containing the same material as the piezoelectric layer 21, it is possible to reduce the difference in linear expansion coefficient between the two. can. Thereby, stress on the membrane portion 21M, which is a part of the piezoelectric layer 21, can be reduced and cracks generated in the piezoelectric layer 21 can be prevented.
- the portion of the piezoelectric layer located in the region overlapping with the cavity when viewed from the thickness direction is also referred to as a "membrane portion.”
- the thickness of the first substrate 31 may be the same as the thickness of the piezoelectric layer 21, may be greater than the thickness of the piezoelectric layer 21, or may be smaller than the thickness of the piezoelectric layer 21.
- the thickness of the first substrate 31 may be the same as the thickness of the intermediate layer 41, may be greater than the thickness of the intermediate layer 41, or may be smaller than the thickness of the intermediate layer 41.
- the first substrate 31 is made of the same kind of material as the piezoelectric layer 21, for example.
- the first substrate 31 is preferably a piezoelectric substrate.
- the first substrate 31 is made of, for example, lithium niobate (LiNbO x ) or lithium tantalate (LiTaO x ).
- the first substrate 31 may be made of LiNbO 3 or LiTaO 3 .
- the following two-dimensional model is used to evaluate the relationship between the linear expansion coefficient of the first substrate 31 and the stress that causes cracks in the membrane portion 21M. A simulation was conducted.
- FIG. 2 is a cross-sectional view showing a calculation model of the elastic wave device.
- FIG. 3 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG. 2.
- FIG. FIG. 4 is a plan view showing the relationship between the Y direction shown in FIG. 2 and functional electrodes.
- the elastic wave device 10A shown in FIG. 2 includes a support member 20, a piezoelectric layer 21, a functional electrode 22 (see FIG. 4), a single-layer electrode 24A, and a double-layer electrode 25A.
- the support member 20 has a cavity 23 on one main surface (the upper main surface in FIG. 2).
- the support member 20 includes a first substrate 31 and an intermediate layer 41 provided between the first substrate 31 and the piezoelectric layer 21.
- the constituent material of the piezoelectric layer 21 is lithium niobate (LiNbO 3 ), the functional electrode 22 is an IDT electrode, and the constituent material of the intermediate layer 41 is silicon dioxide (SiO 2 ).
- Stress generation conditions Heat to the maximum reflow temperature (270°C).
- Material conditions (1) When the first substrate 31 is made of Si, the orientation of lithium niobate in the piezoelectric layer 21 is changed. (2) When the first substrate 31 is made of the same lithium niobate as the piezoelectric layer 21, the orientation of the lithium niobate in the piezoelectric layer 21 is changed.
- FIG. 5 is a graph showing the dependence of the linear expansion coefficient in the X direction on the maximum principal stress in the portion indicated by the arrow in FIG.
- the linear expansion coefficient of the piezoelectric layer 21 in the X direction is smaller than when the first substrate 31 is made of Si (Si substrate). It can be seen that the larger the value, the smaller the maximum principal stress.
- FIG. 6 is a graph showing the dependence of the coefficient of linear expansion in the X direction on the reduction rate of the relative maximum principal stress.
- FIG. 7 is a graph showing the relationship between the coefficient of linear expansion in the X direction and the cut angle of the piezoelectric layer.
- the piezoelectric layer 21 is made of lithium niobate such as LiNbO 3 , if the rotational Y cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less, Since the effect of reducing the maximum principal stress by 5% or more is expected, it is considered to be effective against cracks. Therefore, it is preferable that the piezoelectric layer 21 is made of lithium niobate such as LiNbO 3 and that the rotational Y-cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less.
- the piezoelectric layer 21 and the first substrate 31 are made of lithium niobate such as LiNbO 3 and that the rotational Y-cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less.
- the elastic wave device of the present invention is manufactured, for example, by the following method.
- FIG. 8 is a cross-sectional view schematically showing an example of the process of forming a sacrificial layer on a piezoelectric substrate.
- a sacrificial layer 50 is formed on the piezoelectric substrate 30.
- the piezoelectric substrate 30 for example, a substrate made of LiNbO 3 or LiTaO 3 is used.
- the material for the sacrificial layer 50 an appropriate material that can be removed by etching, which will be described later, is used.
- an appropriate material that can be removed by etching which will be described later, is used.
- ZnO or the like is used.
- the sacrificial layer 50 can be formed, for example, by the following method. First, a ZnO film is formed by sputtering. Thereafter, resist coating, exposure and development are performed in this order. Next, a pattern of the sacrificial layer 50 is formed by performing wet etching. Note that the sacrificial layer 50 may be formed by other methods.
- FIG. 9 is a cross-sectional view schematically showing an example of the process of forming the intermediate layer.
- the surface of the intermediate layer 41 is planarized.
- the intermediate layer 41 for example, a SiO 2 film or the like is formed.
- the intermediate layer 41 can be formed by, for example, a sputtering method.
- the intermediate layer 41 can be planarized by, for example, chemical mechanical polishing (CMP).
- FIG. 10 is a cross-sectional view schematically showing an example of the process of bonding the first substrate to the intermediate layer.
- the first substrate 31 is bonded to the intermediate layer 41. Thereby, the support member 20 is formed.
- a piezoelectric substrate made of, for example, LiNbO 3 or LiTaO 3 is used.
- FIG. 11 is a cross-sectional view schematically showing an example of the process of thinning the piezoelectric substrate.
- the piezoelectric substrate 30 is thinned. As a result, the piezoelectric layer 21 is formed.
- the piezoelectric substrate 30 can be thinned by, for example, a smart cut method, polishing, or the like.
- FIG. 12 is a cross-sectional view schematically showing an example of the process of forming functional electrodes, busbar electrodes, and wiring electrodes.
- a functional electrode 22, a busbar electrode, and a wiring electrode 24 are formed on one main surface of the piezoelectric layer 21.
- the functional electrode 22, the bus bar electrode, and the wiring electrode 24 can be formed by, for example, a lift-off method.
- a two-layer wiring 25 is also formed on one main surface of the piezoelectric layer 21.
- FIG. 13 is a cross-sectional view schematically showing an example of the step of forming a through hole.
- through holes 51 are formed in the piezoelectric layer 21.
- the through hole 51 is formed to reach the sacrificial layer 50.
- the through hole 51 can be formed by, for example, a dry etching method.
- the through hole 51 is used as an etching hole.
- FIG. 14 is a cross-sectional view schematically showing an example of the process of removing the sacrificial layer.
- the sacrificial layer 50 is removed using the through hole 51.
- a cavity 23 is formed in the support member 20.
- the elastic wave device 10 is obtained.
- FIG. 15 is a cross-sectional view schematically showing another example of the elastic wave device according to the first embodiment of the present invention.
- the support member 20 may further include a second substrate 32 made of Si on the opposite side of the intermediate layer 41 with the first substrate 31 in between.
- the thickness of the second substrate 32 may be the same as the thickness of the first substrate 31, may be greater than the thickness of the first substrate 31, or may be smaller than the thickness of the first substrate 31.
- the thickness of the second substrate 32 may be the same as the thickness of the piezoelectric layer 21, may be greater than the thickness of the piezoelectric layer 21, or may be smaller than the thickness of the piezoelectric layer 21.
- the thickness of the second substrate 32 may be the same as the thickness of the intermediate layer 41, may be greater than the thickness of the intermediate layer 41, or may be smaller than the thickness of the intermediate layer 41.
- the outer circumferential edge of the second substrate 32 be located outside the outer circumferential edge of the first substrate 31 when viewed from the thickness direction. That is, it is preferable that the outer periphery of the first substrate 31 is located inside the outer periphery of the second substrate 32 when viewed from the thickness direction.
- An intermediate layer 42 may be provided between the first substrate 31 and the second substrate 32.
- the intermediate layer 42 may not be provided between the first substrate 31 and the second substrate 32. That is, the first substrate 31 and the second substrate 32 may be directly bonded.
- the material constituting the intermediate layer 42 is preferably the same type of material as the material constituting the intermediate layer 41.
- the thickness of the intermediate layer 42 may be the same as the thickness of the intermediate layer 41, may be greater than the thickness of the intermediate layer 41, or may be smaller than the thickness of the intermediate layer 41.
- the thickness of the intermediate layer 42 may be the same as the thickness of the piezoelectric layer 21, may be greater than the thickness of the piezoelectric layer 21, or may be smaller than the thickness of the piezoelectric layer 21.
- the thickness of the intermediate layer 42 may be the same as the thickness of the first substrate 31, may be greater than the thickness of the first substrate 31, or may be smaller than the thickness of the first substrate 31.
- the thickness of the intermediate layer 42 may be the same as the thickness of the second substrate 32, may be greater than the thickness of the second substrate 32, or may be smaller than the thickness of the second substrate 32.
- the support member further includes a second substrate made of Si on the opposite side of the intermediate layer with the first substrate in between. Furthermore, a third substrate made of Si or metal is provided with a gap between the piezoelectric layer and the main surface of the piezoelectric layer opposite to the cavity, and the second substrate and the third substrate are metal-bonded. Hermetically sealed.
- the piezoelectric layer provided with the functional electrode is held by a support member containing the same kind of material as the piezoelectric layer, so that both The difference in linear expansion coefficient can be reduced. This can reduce stress on the membrane portion, which is a part of the piezoelectric layer, and prevent cracks from occurring in the piezoelectric layer.
- the supporting member is of the same type as the piezoelectric layer.
- the flexural strength is weaker than that of a Si substrate which is commonly used as a support substrate.
- the support member further includes a second substrate made of Si, and the second substrate made of Si and the third substrate made of Si or metal are hermetically sealed by metal bonding, thereby improving the grindability of the substrate. As a result, a low-profile, hermetically sealed package structure can be realized.
- FIG. 16 is a cross-sectional view schematically showing an example of an elastic wave device according to the second embodiment of the present invention.
- the elastic wave device 10C shown in FIG. 16 includes a support member 20, a piezoelectric layer 21, and a functional electrode 22.
- the support member 20 has a cavity 23 on one main surface (the upper main surface in FIG. 16).
- the piezoelectric layer 21 is provided on one main surface of the support member 20 so as to cover the cavity 23.
- the functional electrode 22 is provided on at least one main surface of the piezoelectric layer 21.
- the functional electrode 22 is provided on one main surface (the upper main surface in FIG. 16) of the piezoelectric layer 21.
- the functional electrode 22 is, for example, an IDT electrode provided on one main surface of the piezoelectric layer 21.
- the functional electrode 22 is connected to a busbar electrode and wiring electrode 24, and a two-layer wiring 25.
- the support member 20 includes a first substrate 31 and an intermediate layer 41 provided between the first substrate 31 and the piezoelectric layer 21.
- the support member 20 contains the same type of material as the piezoelectric layer 21.
- the first substrate 31 is made of the same kind of material as the piezoelectric layer 21, for example.
- the intermediate layer 41 is made of silicon oxide (SiO x ) such as silicon dioxide (SiO 2 ), for example.
- the support member 20 further includes a second substrate 32 made of Si on the opposite side of the intermediate layer 41 with the first substrate 31 in between.
- the intermediate layer 42 may be provided between the first substrate 31 and the second substrate 32, or the intermediate layer 42 may not be provided.
- the elastic wave device 10C further includes a third substrate 33 made of Si or metal.
- the third substrate 33 is provided at a distance from the piezoelectric layer 21 so as to face the main surface of the piezoelectric layer 21 on the side opposite to the cavity 23 .
- the third substrate 33 is made of, for example, Si. In that case, the second substrate 32 and the third substrate 33 are both Si substrates.
- the third substrate 33 is made of metal.
- the third substrate 33 is, for example, a metal substrate made of Cu or the like.
- the thickness of the third substrate 33 may be the same as the thickness of the first substrate 31, may be greater than the thickness of the first substrate 31, or may be smaller than the thickness of the first substrate 31. Further, the thickness of the third substrate 33 may be the same as the thickness of the second substrate 32, may be greater than the thickness of the second substrate 32, or may be smaller than the thickness of the second substrate 32.
- the second substrate 32 and the third substrate 33 are hermetically sealed by metal bonding.
- the metal bond is, for example, Au-Au bond or solder bond.
- the second substrate 32 and the third substrate 33 are hermetically sealed by a metal seal 35 and a solder seal 37.
- the elastic wave device 10C further includes a terminal electrode 45 that is electrically connected to the functional electrode 22.
- the terminal electrode 45 is exposed on the surface of the second substrate 32 on the opposite side to the first substrate 31. That is, the terminal electrode 45 is arranged on the second substrate 32 side.
- the terminal electrode 45 is provided so as to penetrate the support member 20 in the thickness direction.
- Solder balls 47 are provided on the surface of the second substrate 32 on the opposite side from the first substrate 31.
- the solder ball 47 is electrically connected to the functional electrode 22 via the terminal electrode 45, the two-layer wiring 25, and the like.
- FIG. 17 is a cross-sectional view schematically showing another example of the elastic wave device according to the second embodiment of the present invention.
- the cross sections of the piezoelectric layer 21, intermediate layer 41, and first substrate 31 may have a tapered shape toward the piezoelectric layer 21 side.
- the cross section of the intermediate layer 42 may also have a tapered shape toward the piezoelectric layer 21 side.
- the cross sections of the support member 20 and the piezoelectric layer 21 excluding the second substrate 32 may have a tapered shape toward the piezoelectric layer 21 side.
- FIG. 18 is a cross-sectional view schematically showing still another example of the elastic wave device according to the second embodiment of the present invention.
- the terminal electrode 45 is exposed on the surface of the third substrate 33 on the opposite side from the piezoelectric layer 21. That is, the terminal electrode 45 is arranged on the third substrate 33 side.
- the terminal electrode 45 penetrates the third substrate 33 in the thickness direction and reaches the surface of the second substrate 32 on the first substrate 31 side.
- a two-layer wiring 25 extending to the surface of the second substrate 32 on the first substrate 31 side is connected to the terminal electrode 45.
- Solder balls 47 are provided on the surface of the third substrate 33 on the opposite side from the piezoelectric layer 21.
- the solder ball 47 is electrically connected to the functional electrode 22 via the terminal electrode 45, the two-layer wiring 25, and the like.
- the cross sections of the piezoelectric layer 21, intermediate layer 41, and first substrate 31 may have a tapered shape toward the piezoelectric layer 21 side.
- the cross section of the intermediate layer 42 may also have a tapered shape toward the piezoelectric layer 21 side.
- the cross sections of the support member 20 and the piezoelectric layer 21 excluding the second substrate 32 may have a tapered shape toward the piezoelectric layer 21 side.
- the elastic wave device of the present invention is not limited to the above embodiments, and various applications and modifications can be made within the scope of the present invention regarding the configuration, manufacturing conditions, etc. of the elastic wave device.
- the cavity is provided on the intermediate layer side of the support member, but the cavity may be provided on the first substrate side of the support member.
- FIG. 19 is a cross-sectional view schematically showing a first modification of the elastic wave device according to the first embodiment of the present invention.
- a cavity 23 is provided on the first substrate 31 side of the support member 20.
- An intermediate layer 41 is provided between the piezoelectric layer 21 and the cavity 23.
- the first substrate 31 is made of the same kind of material as the piezoelectric layer 21, for example.
- the cavity 23 can be formed on the first substrate 31 side by diffusing various metals such as titanium (Ti) into the first substrate 31 using heat.
- FIG. 20 is a sectional view schematically showing a second modification of the elastic wave device according to the first embodiment of the present invention.
- a cavity 23 is provided on the first substrate 31 side of the support member 20.
- the intermediate layer 41 may not be provided between the piezoelectric layer 21 and the cavity 23.
- FIGS. 21A to 21E are cross-sectional views schematically showing an example of a method for forming a cavity on the first substrate side of the support member.
- a piezoelectric substrate 30 having an intermediate layer 41 provided on its surface is prepared.
- a first substrate 31 in which a sacrificial layer 50 is embedded is prepared.
- the piezoelectric substrate 30 and the first substrate 31 are bonded by atomic diffusion bonding (ADB) so that the intermediate layer 41 and the sacrificial layer 50 face each other.
- ADB atomic diffusion bonding
- the piezoelectric substrate 30 and the first substrate 31 are bonded via a metal layer 52 such as Ti.
- heat treatment is performed on the joined piezoelectric substrate 30 and first substrate 31. Due to the heat treatment, metal such as Ti contained in the metal layer 52 is diffused into the piezoelectric material (lithium niobate, etc.) of the first substrate 31.
- the piezoelectric substrate 30 is thinned to form the piezoelectric layer 21, and electrodes such as the functional electrode 22 are formed.
- the sacrificial layer 50 is removed using the through hole 51.
- the metal layer 52 on the sacrificial layer 50 is removed together with the sacrificial layer 50.
- a cavity 23 is formed on the first substrate 31 side of the support member 20.
- an elastic wave device that utilizes a thickness shear mode and a plate wave will be described using as an example an elastic wave device in which the material of the support substrate corresponding to the first substrate is not limited to the same type of material as the piezoelectric layer. Note that the following description uses an example in which the functional electrode is an IDT electrode.
- FIG. 22 is a schematic perspective view showing the appearance of an example of an elastic wave device that utilizes bulk waves in thickness shear mode.
- FIG. 23 is a plan view showing the electrode structure on the piezoelectric layer of the acoustic wave device shown in FIG. 22.
- FIG. 24 is a cross-sectional view of a portion taken along line AA in FIG. 22.
- the acoustic wave device 1 has a piezoelectric layer 2 made of, for example, LiNbO 3 .
- the piezoelectric layer 2 may be made of LiTaO 3 .
- the cut angle of LiNbO 3 or LiTaO 3 is, for example, a Z cut, but may also be a rotational Y cut or an X cut.
- the propagation directions of Y propagation and X propagation are ⁇ 30°.
- the thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably 50 nm or more and 1000 nm or less.
- the piezoelectric layer 2 has a first main surface 2a and a second main surface 2b that face each other.
- Electrode 3 and an electrode 4 are provided on the first main surface 2a of the piezoelectric layer 2, on the first main surface 2a of the piezoelectric layer 2, an electrode 3 and an electrode 4 are provided.
- electrode 3 is an example of a "first electrode”
- electrode 4 is an example of a "second electrode”.
- the plurality of electrodes 3 are the plurality of first electrode fingers connected to the first busbar electrode 5.
- the plurality of electrodes 4 are a plurality of second electrode fingers connected to the second busbar electrode 6.
- the plurality of electrodes 3 and the plurality of electrodes 4 are interposed with each other. Electrode 3 and electrode 4 have a rectangular shape and have a length direction.
- the electrode 3 and the adjacent electrode 4 face each other in a direction perpendicular to this length direction.
- Electrodes 3 and 4 constitute an IDT (Interdigital Transducer) electrode.
- the length direction of the electrodes 3 and 4 and the direction perpendicular to the length direction of the electrodes 3 and 4 are both directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can be said that the electrode 3 and the adjacent electrode 4 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2. Further, the length direction of the electrodes 3 and 4 may be replaced with the direction perpendicular to the length direction of the electrodes 3 and 4 shown in FIGS. 22 and 23. That is, in FIGS.
- the electrodes 3 and 4 may be extended in the direction in which the first busbar electrode 5 and the second busbar electrode 6 are extended. In that case, the first busbar electrode 5 and the second busbar electrode 6 will extend in the direction in which the electrodes 3 and 4 extend in FIGS. 22 and 23.
- a plurality of pairs of structures in which an electrode 3 connected to one potential and an electrode 4 connected to the other potential are adjacent to each other are provided in a direction perpendicular to the length direction of the electrodes 3 and 4.
- the expression “electrode 3 and electrode 4 are adjacent” does not mean that electrode 3 and electrode 4 are arranged so as to be in direct contact with each other, but when electrode 3 and electrode 4 are arranged with a gap between them.
- the center-to-center distance between the electrodes 3 and 4, that is, the pitch, is preferably in the range of 1 ⁇ m or more and 10 ⁇ m or less. Note that the center-to-center distance between the electrodes 3 and 4 refers to the center of the width dimension of the electrode 3 in the direction orthogonal to the length direction of the electrode 3, and the width dimension of the electrode 4 in the direction orthogonal to the length direction of the electrode 4.
- the distance between the center of refers to the average value of the distance between the centers of adjacent electrodes 3 and 4 among 1.5 or more pairs of electrodes 3 and 4.
- the width of the electrodes 3 and 4, that is, the dimension in the opposing direction of the electrodes 3 and 4 is preferably in the range of 150 nm or more and 1000 nm or less.
- the direction perpendicular to the length direction of the electrodes 3 and 4 is the direction perpendicular to the polarization direction of the piezoelectric layer 2.
- “orthogonal” is not limited to strictly orthogonal, but approximately orthogonal (for example, the angle between the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is 90° ⁇ 10°) But that's fine.
- a support substrate 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an intermediate layer (also called a bonding layer) 7 interposed therebetween.
- the intermediate layer 7 and the support substrate 8 have a frame-like shape, and have openings 7a and 8a, as shown in FIG. Thereby, a cavity 9 is formed.
- the cavity 9 is provided so as not to hinder the vibration of the excitation region C (see FIG. 23) 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 that does not overlap with the portion where at least one pair of electrodes 3 and 4 are provided. Note that the intermediate layer 7 may not be provided. Therefore, the support substrate 8 can be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2.
- the intermediate layer 7 is made of silicon oxide, for example. However, other than silicon oxide, an appropriate insulating material such as silicon oxynitride or alumina can be used.
- the support substrate 8 is made of Si. The plane orientation of the Si surface on the piezoelectric layer 2 side may be (100), (110), or (111). Preferably, Si has a high resistivity of 4 k ⁇ or more. However, the support substrate 8 can also be constructed using an appropriate insulating material or semiconductor material.
- Examples of materials for the support substrate 8 include aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and starch.
- Various ceramics such as tite and forsterite, dielectrics such as diamond and glass, semiconductors such as gallium nitride, etc. can be used.
- the plurality of electrodes 3, electrodes 4, first busbar electrode 5, and second busbar electrode 6 are made of an appropriate metal or alloy such as Al or AlCu alloy.
- the electrode 3, the electrode 4, the first busbar electrode 5, and the second busbar electrode 6 have a structure in which an Al film is laminated on a Ti film. Note that an adhesive layer other than the Ti film may be used.
- an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 6.
- d/p is 0. It is considered to be 5 or less. Therefore, the bulk wave in the thickness shear mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d/p is 0.24 or less, in which case even better resonance characteristics can be obtained.
- the distance p between the centers of the adjacent electrodes 3 and 4 is the average distance between the centers of the adjacent electrodes 3 and 4.
- the elastic wave device 1 of this embodiment has the above configuration, even if the logarithm of the electrodes 3 and 4 is reduced in an attempt to achieve miniaturization, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides and has little propagation loss. Further, the reason why the reflector is not required is because the bulk wave in the thickness shear mode is used. The difference between the Lamb wave used in a conventional elastic wave device and the thickness-shear mode bulk wave will be explained with reference to FIGS. 25 and 26.
- FIG. 25 is a schematic front sectional view for explaining Lamb waves propagating through the piezoelectric film of the acoustic wave device.
- the piezoelectric film 201 in the elastic wave device described in Patent Document 1 (Japanese Patent Publication No. 2012-257019), waves propagate in the piezoelectric film 201 as indicated by arrows.
- the first main surface 201a and the second main surface 201b are opposite to each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. It is.
- the X direction is the direction in which the electrode fingers of the IDT electrodes are lined up.
- the Lamb wave the wave propagates in the X direction as shown.
- the piezoelectric film 201 vibrates as a whole, but since the wave propagates in the X direction, reflectors are placed 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 electrode fingers is reduced, the Q value decreases.
- FIG. 26 is a schematic front cross-sectional view for explaining a thickness-shear mode bulk wave propagating through a piezoelectric layer of an elastic wave device.
- the waves connect the first main surface 2a and the second main surface 2b of the piezoelectric layer 2. It propagates almost in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Since resonance characteristics are obtained by the propagation of waves in the Z direction, a reflector is not required. Therefore, no propagation loss occurs when propagating to the reflector. Therefore, even if the number of electrode pairs consisting of electrodes 3 and 4 is reduced in an attempt to promote miniaturization, the Q value is unlikely to decrease.
- FIG. 27 is a diagram showing the amplitude direction of the bulk wave in the thickness shear mode. As shown in FIG. 27, the amplitude direction of the bulk wave in the thickness shear mode is opposite between the first region 451 included in the excitation region C of the piezoelectric layer 2 and the second region 452 included in the excitation region C.
- FIG. 27 schematically shows a bulk wave when a voltage is applied between electrode 3 and electrode 4 such that electrode 4 has a higher potential than electrode 3.
- the first region 451 is a region of the excitation region C between a 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 452 is a region of the excitation region C between the virtual plane VP1 and the second principal surface 2b.
- the elastic wave device 1 As mentioned above, in the elastic wave device 1, at least one pair of electrodes consisting of the electrode 3 and the electrode 4 are arranged, but since the wave is not propagated in the X direction, the elastic wave device 1 is made up of the electrodes 3 and 4. There does not necessarily have to be a plurality of pairs of electrodes. That is, it is only necessary that at least one pair of electrodes be provided.
- the electrode 3 is an electrode connected to a hot potential
- the electrode 4 is an electrode connected to a ground potential.
- the electrode 3 may be connected to the ground potential
- the electrode 4 may be connected to the hot potential.
- at least one pair of electrodes is an electrode connected to a hot potential or an electrode connected to a ground potential, as described above, and no floating electrode is provided.
- FIG. 28 is a diagram showing an example of the resonance characteristics of the elastic wave device shown in FIG. 22. Note that the design parameters of the elastic wave device 1 that obtained this resonance characteristic are as follows.
- Intermediate layer 7 silicon oxide film with a thickness of 1 ⁇ m.
- Support substrate 8 Si substrate.
- the length of the excitation region C is a dimension along the length direction of the electrodes 3 and 4 of the excitation region C.
- the distances between the electrode pairs made up of the electrodes 3 and 4 were all equal in multiple pairs. That is, the electrodes 3 and 4 were arranged at equal pitches.
- d/p is preferably 0.5 or less, More preferably it is 0.24 or less. This will be explained with reference to FIG. 29.
- FIG. 29 is a diagram showing the relationship between d/2p and the fractional band as a resonator of an acoustic wave device, where p is the distance between the centers of adjacent electrodes and d is the thickness of the piezoelectric layer.
- the at least one pair of electrodes may be one pair, and in the case of one pair of electrodes, the above p is the distance between the centers of adjacent electrodes 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, the average distance between the centers of adjacent electrodes 3 and 4 may be set to p.
- the thickness d of the piezoelectric layer if the piezoelectric layer 2 has thickness variations, a value obtained by averaging the thicknesses may be adopted.
- FIG. 30 is a plan view of another example of an elastic wave device that utilizes bulk waves in thickness-shear mode.
- a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first main surface 2a of the piezoelectric layer 2.
- K in FIG. 30 is the intersection width.
- the number of pairs of electrodes may be one. Even in this case, if the above-mentioned d/p is 0.5 or less, bulk waves in the thickness shear mode can be excited effectively.
- the metallization ratio MR of the adjacent electrodes 3 and 4 satisfies MR ⁇ 1.75(d/p)+0.075. In that case, spurious can be effectively reduced. This will be explained with reference to FIGS. 31 and 32.
- FIG. 31 is a reference diagram showing an example of the resonance characteristics of the elastic wave device shown in FIG. 22.
- a spurious signal indicated by arrow B appears between the resonant frequency and the anti-resonant 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. 23.
- the area surrounded by the dashed line C becomes the excitation region.
- This excitation region is the region where the electrode 3 overlaps the electrode 4 when the electrode 3 and the electrode 4 are viewed in a direction perpendicular to the length direction of the electrodes 3 and 4, that is, in a direction in which they face each other. and a region between electrodes 3 and 4 where electrodes 3 and 4 overlap.
- the area of the electrodes 3 and 4 in the excitation region C with respect to the area of this excitation region becomes the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallized portion to the area of the excitation region.
- MR may be the ratio of the metallized portion included in all the excitation regions to the total area of the excitation regions.
- FIG. 32 is a diagram showing the relationship between the fractional band and the amount of phase rotation of spurious impedance normalized by 180 degrees as the magnitude of spurious when a large number of elastic wave resonators are configured according to the present embodiment. It is. Note that the specific band was adjusted by variously changing the thickness of the piezoelectric layer and the dimensions of the electrode. Furthermore, although FIG. 32 shows the results when a Z-cut piezoelectric layer made of LiNbO 3 is used, the same tendency occurs even when piezoelectric layers with other cut angles are used.
- the spurious is as large as 1.0.
- the fractional band exceeds 0.17, that is, exceeds 17%, a large spurious with a spurious level of 1 or more will affect the pass band even if the parameters constituting the fractional band are changed. Appear within. That is, as in the resonance characteristic shown in FIG. 31, a large spurious signal indicated by arrow B appears within the band. Therefore, it is preferable that the fractional band is 17% or less. In this case, by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, etc., the spurious can be reduced.
- FIG. 33 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional band.
- various elastic wave devices having different d/2p and MR were constructed and the fractional bands were measured.
- the hatched area on the right side of the broken line D in FIG. 33 is the area where the fractional band is 17% or less.
- FIG. 34 is a diagram showing a map of fractional bands with respect to Euler angles (0°, ⁇ , ⁇ ) of LiNbO 3 when d/p is brought as close to 0 as possible.
- the hatched areas in FIG. 34 are regions where a fractional band of at least 5% can be obtained, and the range of these regions can be approximated by the following equations (1), (2), and (3). ).
- ...Formula (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°)
- ...Formula (2) (0° ⁇ 10°, [180°-30° (1-( ⁇ -90) 2 /8100) 1/2 ] ⁇ 180°, arbitrary ⁇ ) ...Formula (3) Therefore, the Euler angle range of formula (1), formula (2), or formula (3) above is preferable because the fractional band can be made sufficiently wide.
- FIG. 35 is a partially cutaway perspective view for explaining an example of an elastic wave device that utilizes Lamb waves.
- the elastic wave device 81 has a support substrate 82.
- the support substrate 82 is provided with an open recess on the upper surface.
- a piezoelectric layer 83 is laminated on the support substrate 82 . Thereby, a cavity 9 is formed.
- An IDT electrode 84 is provided on the piezoelectric layer 83 above the cavity 9 .
- Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction. In FIG. 35, the outer periphery of the cavity 9 is shown by a broken line.
- the IDT electrode 84 includes a first busbar electrode 84a, a second busbar electrode 84b, an electrode 84c as a plurality of first electrode fingers, and an electrode 84d as a plurality of second electrode fingers. and has.
- the plurality of electrodes 84c are connected to the first busbar electrode 84a.
- the plurality of electrodes 84d are connected to the second busbar electrode 84b.
- the plurality of electrodes 84c and the plurality of electrodes 84d are interposed with each other.
- the elastic wave device 81 by applying an alternating current electric field to the IDT electrode 84 on the cavity 9, a Lamb wave as a plate wave is excited. Since the reflectors 85 and 86 are provided on both sides, the resonance characteristic due to the Lamb wave described above can be obtained.
- the elastic wave device of the present invention may utilize plate waves such as Lamb waves.
- the elastic wave device of the present invention may utilize bulk waves. That is, the elastic wave device of the present invention can also be applied to a bulk acoustic wave (BAW) element.
- the functional electrodes are an upper electrode and a lower electrode.
- FIG. 36 is a cross-sectional view schematically showing an example of an elastic wave device that uses bulk waves.
- the elastic wave device 90 includes a support substrate 91.
- a cavity 93 is provided so as to penetrate the support substrate 91.
- a piezoelectric layer 92 is laminated on a support substrate 91 .
- An upper electrode 94 is provided on the first main surface 92a of the piezoelectric layer 92, and a lower electrode 95 is provided on the second main surface 92b of the piezoelectric layer 92.
- an intermediate layer may be provided between the support substrate 91 and the piezoelectric layer 92.
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Abstract
An elastic wave device 10 comprises: a support member 20 having a cavity 23 in one main surface thereof; a piezoelectric layer 21 provided on the one main surface of the support member 20 so as to cover the cavity 23; and a functional electrode 22 provided on at least one of the main surfaces of the piezoelectric layer 21 so as to at least partially overlap with the cavity 23 when viewed from the thickness direction of the piezoelectric layer 21. The support member 20 includes a first substrate 31 and an intermediate layer 41 provided between the first substrate 31 and the piezoelectric layer 21. The support member 20 contains the same type of material as the piezoelectric layer 21.
Description
本発明は、弾性波装置に関する。
The present invention relates to an elastic wave device.
従来、ニオブ酸リチウム又はタンタル酸リチウムからなる圧電層を備える弾性波装置が知られている。
Conventionally, acoustic wave devices including a piezoelectric layer made of lithium niobate or lithium tantalate are known.
特許文献1には、空洞部が形成された支持体と、上記支持体の上に上記空洞部と重なるように設けられている圧電基板と、上記圧電基板の上に上記空洞部と重なるように設けられているIDT(Interdigital Transducer)電極と、を備え、上記IDT電極により板波が励振される弾性波装置であって、上記空洞部の端縁部は、上記IDT電極により励振される板波の伝搬方向と平行に延びる直線部を含まない、弾性波装置が開示されている。
Patent Document 1 discloses a support in which a cavity is formed, a piezoelectric substrate provided on the support so as to overlap with the cavity, and a piezoelectric substrate provided on the piezoelectric substrate so as to overlap with the cavity. An acoustic wave device is provided with an IDT (Interdigital Transducer) electrode provided, and a plate wave is excited by the IDT electrode, wherein an edge of the cavity portion is provided with a plate wave excited by the IDT electrode. An elastic wave device is disclosed that does not include a straight portion extending parallel to the propagation direction of the wave.
特許文献1に記載されているような弾性波装置において、支持体(以下、支持基板という)がシリコン(Si)からなる場合、支持基板の材料と圧電基板(以下、圧電層という)の材料とでは線膨張係数が異なることから、空洞部上の圧電層に応力がかかり、圧電層にクラックが発生するおそれがあった。
In an acoustic wave device as described in Patent Document 1, when the support body (hereinafter referred to as a support substrate) is made of silicon (Si), the material of the support substrate and the material of the piezoelectric substrate (hereinafter referred to as a piezoelectric layer) are Since the coefficients of linear expansion are different, stress is applied to the piezoelectric layer above the cavity, and there is a risk that cracks may occur in the piezoelectric layer.
本発明は、圧電層に発生するクラックを防止することが可能な弾性波装置を提供することを目的とする。
An object of the present invention is to provide an elastic wave device that can prevent cracks from occurring in a piezoelectric layer.
本発明の弾性波装置は、空洞部を一方主面に有する支持部材と、上記空洞部を覆うように上記支持部材の上記一方主面に設けられた圧電層と、上記圧電層の少なくとも一方の主面に、上記圧電層の厚み方向から見て少なくとも一部が上記空洞部と重なるように設けられた機能電極と、を備える。上記支持部材は、第1基板と、上記第1基板と上記圧電層との間に設けられた中間層と、を含む。上記支持部材は、上記圧電層と同種の材料を含有する。
The elastic wave device of the present invention includes a support member having a cavity on one main surface, a piezoelectric layer provided on the one main surface of the support member so as to cover the cavity, and at least one of the piezoelectric layers. A functional electrode is provided on the main surface so that at least a portion thereof overlaps with the cavity when viewed from the thickness direction of the piezoelectric layer. The support member includes a first substrate and an intermediate layer provided between the first substrate and the piezoelectric layer. The support member contains the same kind of material as the piezoelectric layer.
本発明によれば、圧電層に発生するクラックを防止することが可能な弾性波装置を提供することができる。
According to the present invention, it is possible to provide an acoustic wave device that can prevent cracks from occurring in the piezoelectric layer.
以下、本発明の弾性波装置について説明する。
Hereinafter, the elastic wave device of the present invention will be explained.
本発明の弾性波装置は、第1、第2及び第3の態様において、ニオブ酸リチウム又はタンタル酸リチウムからなる圧電層と、圧電層の厚み方向に交差する方向において対向する第1電極及び第2電極とを備える。
In the first, second and third aspects, the acoustic wave device of the present invention includes a piezoelectric layer made of lithium niobate or lithium tantalate, a first electrode and a first electrode facing each other in a direction crossing the thickness direction of the piezoelectric layer. 2 electrodes.
第1の態様では、厚み滑り1次モード等の厚み滑りモードのバルク波が利用されている。また、第2の態様では、第1電極及び前記第2電極は隣り合う電極同士であり、圧電層の厚みをd、第1電極及び第2電極の中心間距離をpとした場合、d/pが0.5以下とされている。それによって、第1及び第2の態様では、小型化を進めた場合であっても、Q値を高めることができる。
In the first aspect, a bulk wave in a thickness shear mode such as a primary thickness shear mode is used. Further, in the second aspect, the first electrode and the second electrode are adjacent electrodes, and when the thickness of the piezoelectric layer is d and the distance between the centers of the first electrode and the second electrode is p, d/ p is set to be 0.5 or less. Thereby, in the first and second aspects, the Q value can be increased even when miniaturization is promoted.
また、第3の態様では、板波としてのラム波が利用される。そして、上記ラム波による共振特性を得ることができる。
Furthermore, in the third aspect, Lamb waves are used as plate waves. Then, resonance characteristics due to the Lamb wave described above can be obtained.
本発明の弾性波装置は、第4の態様において、ニオブ酸リチウム又はタンタル酸リチウムからなる圧電層と、圧電層を挟んで圧電層の厚み方向に対向する上部電極及び下部電極とを備える。第4の態様では、バルク波が利用される。
In a fourth aspect, the acoustic wave device of the present invention includes a piezoelectric layer made of lithium niobate or lithium tantalate, and an upper electrode and a lower electrode that face each other in the thickness direction of the piezoelectric layer with the piezoelectric layer in between. In a fourth aspect, bulk waves are utilized.
以下、図面を参照しつつ、本発明の具体的な実施形態を説明することにより、本発明を明らかにする。
Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.
以下に示す図面は模式的なものであり、その寸法、縦横比の縮尺等は実際の製品とは異なる場合がある。
The drawings shown below are schematic, and their dimensions, aspect ratios, etc. may differ from the actual product.
なお、本明細書に記載の各実施形態は、例示的なものであり、異なる実施形態間において、構成の部分的な置換又は組み合わせが可能である。また、各実施形態を特に区別しない場合、単に「本発明の弾性波装置」という。
Note that each embodiment described in this specification is an illustrative example, and parts of the configurations can be partially replaced or combined between different embodiments. In addition, unless there is a particular distinction between the embodiments, they will simply be referred to as "the elastic wave device of the present invention."
[第1実施形態]
図1は、本発明の第1実施形態に係る弾性波装置の一例を模式的に示す断面図である。 [First embodiment]
FIG. 1 is a cross-sectional view schematically showing an example of an elastic wave device according to a first embodiment of the present invention.
図1は、本発明の第1実施形態に係る弾性波装置の一例を模式的に示す断面図である。 [First embodiment]
FIG. 1 is a cross-sectional view schematically showing an example of an elastic wave device according to a first embodiment of the present invention.
図1に示す弾性波装置10は、支持部材20と、圧電層21と、機能電極22と、を備える。
The elastic wave device 10 shown in FIG. 1 includes a support member 20, a piezoelectric layer 21, and a functional electrode 22.
支持部材20は、空洞部23を一方主面(図1では上側の主面)に有する。
The support member 20 has a cavity 23 on one main surface (the upper main surface in FIG. 1).
圧電層21は、空洞部23を覆うように支持部材20の一方主面に設けられている。
The piezoelectric layer 21 is provided on one main surface of the support member 20 so as to cover the cavity 23.
圧電層21は、例えば、ニオブ酸リチウム(LiNbOx)又はタンタル酸リチウム(LiTaOx)からなる。その場合、圧電層21は、LiNbO3又はLiTaO3から構成されてもよい。
The piezoelectric layer 21 is made of, for example, lithium niobate (LiNbO x ) or lithium tantalate (LiTaO x ). In that case, the piezoelectric layer 21 may be composed of LiNbO 3 or LiTaO 3 .
機能電極22は、圧電層21の少なくとも一方の主面に設けられている。図1に示す例では、圧電層21の一方の主面(図1では上側の主面)に機能電極22が設けられている。
The functional electrode 22 is provided on at least one main surface of the piezoelectric layer 21. In the example shown in FIG. 1, the functional electrode 22 is provided on one main surface (the upper main surface in FIG. 1) of the piezoelectric layer 21.
機能電極22は、圧電層21の厚み方向(図1では上下方向)から見て少なくとも一部が空洞部23と重なるように設けられている。圧電層21の厚み方向から見て、機能電極22の全部が空洞部23と重なるように設けられていてもよく、機能電極22の一部が空洞部23と重なるように設けられていてもよい。
The functional electrode 22 is provided so that at least a portion thereof overlaps with the cavity 23 when viewed from the thickness direction of the piezoelectric layer 21 (vertical direction in FIG. 1). When viewed from the thickness direction of the piezoelectric layer 21, the functional electrode 22 may be provided so that the entirety thereof overlaps with the cavity 23, or a part of the functional electrode 22 may be provided so as to overlap with the cavity 23. .
機能電極22は、例えば、圧電層21の一方の主面に設けられたIDT電極である。
The functional electrode 22 is, for example, an IDT electrode provided on one main surface of the piezoelectric layer 21.
図1に示す例では、機能電極22には、バスバー電極及び配線電極24と、2層配線25とが接続されている。
In the example shown in FIG. 1, the functional electrode 22 is connected to a busbar electrode and wiring electrode 24, and a two-layer wiring 25.
支持部材20は、第1基板31と、第1基板31と圧電層21との間に設けられた中間層(接合層、絶縁層ともいう)41と、を含む。
The support member 20 includes a first substrate 31 and an intermediate layer (also referred to as a bonding layer or an insulating layer) 41 provided between the first substrate 31 and the piezoelectric layer 21.
中間層41は、例えば、二酸化ケイ素(SiO2)等の酸化ケイ素(SiOx)からなる。
The intermediate layer 41 is made of silicon oxide (SiO x ) such as silicon dioxide (SiO 2 ), for example.
空洞部23は、支持部材20を厚み方向(図1では上下方向)に貫通してもよく、貫通しなくてもよい。例えば、中間層41を厚み方向に貫通するように空洞部23が設けられていてもよく、中間層41を厚み方向に貫通しないように空洞部23が設けられていてもよい。
The cavity 23 may or may not penetrate the support member 20 in the thickness direction (vertical direction in FIG. 1). For example, the cavity 23 may be provided so as to penetrate the intermediate layer 41 in the thickness direction, or the cavity 23 may be provided so as not to penetrate the intermediate layer 41 in the thickness direction.
支持部材20は、圧電層21と同種の材料を含有する。
The support member 20 contains the same kind of material as the piezoelectric layer 21.
本明細書において、「同種の材料」とは、完全に同じ材料である場合だけでなく、結晶性又は配向性が異なる場合や、添加物の有無又は濃度が異なる場合も含む。以下においても同様である。
In this specification, the term "materials of the same kind" includes not only cases where the materials are completely the same, but also cases where the crystallinity or orientation is different, and cases where the presence or absence or concentration of additives is different. The same applies to the following.
弾性波装置10では、機能電極22が設けられている圧電層21を、圧電層21と同種の材料を含有する支持部材20で保持することにより、両者の線膨張係数の差を小さくすることができる。これにより、圧電層21の一部であるメンブレン部21Mへの応力を軽減し、圧電層21に発生するクラックを防止することができる。
In the acoustic wave device 10, by holding the piezoelectric layer 21 on which the functional electrode 22 is provided with the support member 20 containing the same material as the piezoelectric layer 21, it is possible to reduce the difference in linear expansion coefficient between the two. can. Thereby, stress on the membrane portion 21M, which is a part of the piezoelectric layer 21, can be reduced and cracks generated in the piezoelectric layer 21 can be prevented.
本明細書では、厚み方向から見て空洞部と重なる領域に位置する圧電層の部分を「メンブレン部」とも称する。
In this specification, the portion of the piezoelectric layer located in the region overlapping with the cavity when viewed from the thickness direction is also referred to as a "membrane portion."
第1基板31の厚みは、圧電層21の厚みと同じでもよく、圧電層21の厚みより大きくてもよく、圧電層21の厚みより小さくてもよい。第1基板31の厚みは、中間層41の厚みと同じでもよく、中間層41の厚みより大きくてもよく、中間層41の厚みより小さくてもよい。
The thickness of the first substrate 31 may be the same as the thickness of the piezoelectric layer 21, may be greater than the thickness of the piezoelectric layer 21, or may be smaller than the thickness of the piezoelectric layer 21. The thickness of the first substrate 31 may be the same as the thickness of the intermediate layer 41, may be greater than the thickness of the intermediate layer 41, or may be smaller than the thickness of the intermediate layer 41.
第1基板31は、例えば、圧電層21と同種の材料からなる。このように、第1基板31は、圧電基板であることが好ましい。具体的には、第1基板31は、例えば、ニオブ酸リチウム(LiNbOx)又はタンタル酸リチウム(LiTaOx)からなる。その場合、第1基板31は、LiNbO3又はLiTaO3から構成されてもよい。
The first substrate 31 is made of the same kind of material as the piezoelectric layer 21, for example. Thus, the first substrate 31 is preferably a piezoelectric substrate. Specifically, the first substrate 31 is made of, for example, lithium niobate (LiNbO x ) or lithium tantalate (LiTaO x ). In that case, the first substrate 31 may be made of LiNbO 3 or LiTaO 3 .
第1基板31が圧電基板である場合の定量的な効果を検証するため、以下の2次元モデルを用いて、第1基板31の線膨張係数とメンブレン部21Mにクラックを引き起こす応力との関係のシミュレーションを実施した。
In order to verify the quantitative effect when the first substrate 31 is a piezoelectric substrate, the following two-dimensional model is used to evaluate the relationship between the linear expansion coefficient of the first substrate 31 and the stress that causes cracks in the membrane portion 21M. A simulation was conducted.
図2は、弾性波装置の計算モデルを示す断面図である。図3は、図2において破線で囲む部分を拡大した断面図である。図4は、図2に示すY方向と機能電極との関係を示す平面図である。
FIG. 2 is a cross-sectional view showing a calculation model of the elastic wave device. FIG. 3 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG. 2. FIG. FIG. 4 is a plan view showing the relationship between the Y direction shown in FIG. 2 and functional electrodes.
図2に示す弾性波装置10Aは、支持部材20と、圧電層21と、機能電極22(図4参照)と、1層電極24Aと、2層電極25Aと、を備える。支持部材20は、空洞部23を一方主面(図2では上側の主面)に有する。
The elastic wave device 10A shown in FIG. 2 includes a support member 20, a piezoelectric layer 21, a functional electrode 22 (see FIG. 4), a single-layer electrode 24A, and a double-layer electrode 25A. The support member 20 has a cavity 23 on one main surface (the upper main surface in FIG. 2).
支持部材20は、第1基板31と、第1基板31と圧電層21との間に設けられた中間層41と、を含む。
The support member 20 includes a first substrate 31 and an intermediate layer 41 provided between the first substrate 31 and the piezoelectric layer 21.
圧電層21の構成材料はニオブ酸リチウム(LiNbO3)、機能電極22はIDT電極、中間層41の構成材料は二酸化ケイ素(SiO2)とする。
The constituent material of the piezoelectric layer 21 is lithium niobate (LiNbO 3 ), the functional electrode 22 is an IDT electrode, and the constituent material of the intermediate layer 41 is silicon dioxide (SiO 2 ).
メンブレン部21Mにおけるクラックは、圧電層21と中間層41との近傍で、かつ、機能電極22が設けられていない圧電層21の領域で発生すると考えられている。また、クラックでは、セラミックの亀裂として特徴的なツイストハックルが確認されている。一般的に、セラミックのクラックは、セラミック内部に発生する主応力に起因すると考えられている。
It is thought that cracks in the membrane portion 21M occur in the vicinity of the piezoelectric layer 21 and the intermediate layer 41 and in the region of the piezoelectric layer 21 where the functional electrode 22 is not provided. Additionally, twisted hackles, which are characteristic of ceramic cracks, have been observed. It is generally believed that cracks in ceramics are caused by principal stress generated within the ceramic.
以上のことから、メンブレン部21Mにクラックが発生しやすいと考えられる図3中に矢印で示す部分の主応力の最大値(最大主応力ともいう)をシミュレーションにより計算した。
Based on the above, the maximum value of the principal stress (also referred to as maximum principal stress) in the portion indicated by the arrow in FIG. 3, where it is thought that cracks are likely to occur in the membrane portion 21M, was calculated by simulation.
シミュレーションに用いた計算条件を以下に示す。
応力発生条件:リフローの最大温度(270℃)まで加熱する。
材料条件:
(1)第1基板31がSiからなる場合において、圧電層21のニオブ酸リチウムの方位を変化させる。
(2)第1基板31が圧電層21と同じニオブ酸リチウムからなる場合において、圧電層21のニオブ酸リチウムの方位を変化させる。 The calculation conditions used for the simulation are shown below.
Stress generation conditions: Heat to the maximum reflow temperature (270°C).
Material conditions:
(1) When thefirst substrate 31 is made of Si, the orientation of lithium niobate in the piezoelectric layer 21 is changed.
(2) When thefirst substrate 31 is made of the same lithium niobate as the piezoelectric layer 21, the orientation of the lithium niobate in the piezoelectric layer 21 is changed.
応力発生条件:リフローの最大温度(270℃)まで加熱する。
材料条件:
(1)第1基板31がSiからなる場合において、圧電層21のニオブ酸リチウムの方位を変化させる。
(2)第1基板31が圧電層21と同じニオブ酸リチウムからなる場合において、圧電層21のニオブ酸リチウムの方位を変化させる。 The calculation conditions used for the simulation are shown below.
Stress generation conditions: Heat to the maximum reflow temperature (270°C).
Material conditions:
(1) When the
(2) When the
図5は、図3中に矢印で示す部分の最大主応力に対するX方向の線膨張係数依存性を示すグラフである。
FIG. 5 is a graph showing the dependence of the linear expansion coefficient in the X direction on the maximum principal stress in the portion indicated by the arrow in FIG.
図5より、第1基板31がニオブ酸リチウムからなる場合(LN基板)には、第1基板31がSiからなる場合(Si基板)に比べて、圧電層21のX方向の線膨張係数が大きくなるほど、最大主応力が小さくなることが分かる。
From FIG. 5, when the first substrate 31 is made of lithium niobate (LN substrate), the linear expansion coefficient of the piezoelectric layer 21 in the X direction is smaller than when the first substrate 31 is made of Si (Si substrate). It can be seen that the larger the value, the smaller the maximum principal stress.
図6は、相対的な最大主応力の低減割合に対するX方向の線膨張係数依存性を示すグラフである。
FIG. 6 is a graph showing the dependence of the coefficient of linear expansion in the X direction on the reduction rate of the relative maximum principal stress.
図5の結果から相対的な最大主応力の低減割合を求めたところ、図6に示すように、圧電層21のX方向の線膨張係数が0.8ppm/℃以上であれば、最大主応力が5%以上低減される効果が見込まれる。
When the relative reduction rate of the maximum principal stress was calculated from the results of FIG. 5, as shown in FIG. 6, if the coefficient of linear expansion of the piezoelectric layer 21 in the It is expected that the effect will be reduced by 5% or more.
図7は、X方向の線膨張係数と圧電層のカット角との関係を示すグラフである。
FIG. 7 is a graph showing the relationship between the coefficient of linear expansion in the X direction and the cut angle of the piezoelectric layer.
図7より、圧電層21のカット角が90度以上163度以下の範囲であれば、0.8ppm/℃以上の線膨張係数が得られるため、最大主応力が5%以上低減される効果が見込まれる。
From FIG. 7, if the cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less, a linear expansion coefficient of 0.8 ppm/℃ or more can be obtained, so the maximum principal stress can be reduced by 5% or more. expected.
図5、図6及び図7の結果より、圧電層21がLiNbO3等のニオブ酸リチウムからなる場合には、圧電層21の回転Yカット角が90度以上163度以下の範囲であれば、最大主応力が5%以上低減される効果が見込まれるため、クラックに対して有効であると考えられる。したがって、圧電層21がLiNbO3等のニオブ酸リチウムからなり、圧電層21の回転Yカット角が90度以上163度以下の範囲であることが好ましい。特に、圧電層21及び第1基板31がLiNbO3等のニオブ酸リチウムからなり、圧電層21の回転Yカット角が90度以上163度以下の範囲であることが好ましい。
From the results of FIGS. 5, 6, and 7, when the piezoelectric layer 21 is made of lithium niobate such as LiNbO 3 , if the rotational Y cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less, Since the effect of reducing the maximum principal stress by 5% or more is expected, it is considered to be effective against cracks. Therefore, it is preferable that the piezoelectric layer 21 is made of lithium niobate such as LiNbO 3 and that the rotational Y-cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less. In particular, it is preferable that the piezoelectric layer 21 and the first substrate 31 are made of lithium niobate such as LiNbO 3 and that the rotational Y-cut angle of the piezoelectric layer 21 is in the range of 90 degrees or more and 163 degrees or less.
本発明の弾性波装置は、例えば、以下の方法により製造される。
The elastic wave device of the present invention is manufactured, for example, by the following method.
図8は、圧電基板上に犠牲層を形成する工程の一例を模式的に示す断面図である。
FIG. 8 is a cross-sectional view schematically showing an example of the process of forming a sacrificial layer on a piezoelectric substrate.
図8に示すように、圧電基板30上に犠牲層50を形成する。
As shown in FIG. 8, a sacrificial layer 50 is formed on the piezoelectric substrate 30.
圧電基板30としては、例えば、LiNbO3又はLiTaO3等からなる基板が用いられる。
As the piezoelectric substrate 30, for example, a substrate made of LiNbO 3 or LiTaO 3 is used.
犠牲層50の材料としては、後述するエッチングにより除去され得る適宜の材料が用いられる。例えば、ZnO等が用いられる。
As the material for the sacrificial layer 50, an appropriate material that can be removed by etching, which will be described later, is used. For example, ZnO or the like is used.
犠牲層50は、例えば、以下の方法により形成することができる。まず、スパッタリング法によりZnO膜を形成する。その後、レジスト塗布、露光及び現像をこの順に行う。次に、ウェットエッチングを行うことにより、犠牲層50のパターンを形成する。なお、犠牲層50は、他の方法により形成されてもよい。
The sacrificial layer 50 can be formed, for example, by the following method. First, a ZnO film is formed by sputtering. Thereafter, resist coating, exposure and development are performed in this order. Next, a pattern of the sacrificial layer 50 is formed by performing wet etching. Note that the sacrificial layer 50 may be formed by other methods.
図9は、中間層を形成する工程の一例を模式的に示す断面図である。
FIG. 9 is a cross-sectional view schematically showing an example of the process of forming the intermediate layer.
図9に示すように、犠牲層50を覆うように中間層41を形成した後、中間層41の表面を平坦化する。
As shown in FIG. 9, after forming the intermediate layer 41 to cover the sacrificial layer 50, the surface of the intermediate layer 41 is planarized.
中間層41として、例えば、SiO2膜等が形成される。中間層41は、例えば、スパッタリング法等により形成することができる。中間層41の平坦化は、例えば、化学的機械研磨(CMP)等により行うことができる。
As the intermediate layer 41, for example, a SiO 2 film or the like is formed. The intermediate layer 41 can be formed by, for example, a sputtering method. The intermediate layer 41 can be planarized by, for example, chemical mechanical polishing (CMP).
図10は、中間層に第1基板を接合する工程の一例を模式的に示す断面図である。
FIG. 10 is a cross-sectional view schematically showing an example of the process of bonding the first substrate to the intermediate layer.
図10に示すように、中間層41に第1基板31を接合する。これにより、支持部材20が形成される。
As shown in FIG. 10, the first substrate 31 is bonded to the intermediate layer 41. Thereby, the support member 20 is formed.
第1基板31としては、例えば、LiNbO3又はLiTaO3等からなる圧電基板が用いられる。
As the first substrate 31, a piezoelectric substrate made of, for example, LiNbO 3 or LiTaO 3 is used.
図11は、圧電基板を薄化する工程の一例を模式的に示す断面図である。
FIG. 11 is a cross-sectional view schematically showing an example of the process of thinning the piezoelectric substrate.
図11に示すように、圧電基板30を薄化する。これにより、圧電層21が形成される。圧電基板30の薄化は、例えば、スマートカット法、研磨等により行うことができる。
As shown in FIG. 11, the piezoelectric substrate 30 is thinned. As a result, the piezoelectric layer 21 is formed. The piezoelectric substrate 30 can be thinned by, for example, a smart cut method, polishing, or the like.
図12は、機能電極、バスバー電極及び配線電極を形成する工程の一例を模式的に示す断面図である。
FIG. 12 is a cross-sectional view schematically showing an example of the process of forming functional electrodes, busbar electrodes, and wiring electrodes.
図12に示すように、圧電層21の一方主面上に、機能電極22、バスバー電極及び配線電極24を形成する。機能電極22、バスバー電極及び配線電極24は、例えば、リフトオフ法等により形成することができる。図示されていないが、圧電層21の一方主面上には、2層配線25(図1参照)も形成する。
As shown in FIG. 12, a functional electrode 22, a busbar electrode, and a wiring electrode 24 are formed on one main surface of the piezoelectric layer 21. The functional electrode 22, the bus bar electrode, and the wiring electrode 24 can be formed by, for example, a lift-off method. Although not shown, a two-layer wiring 25 (see FIG. 1) is also formed on one main surface of the piezoelectric layer 21.
図13は、貫通孔を形成する工程の一例を模式的に示す断面図である。
FIG. 13 is a cross-sectional view schematically showing an example of the step of forming a through hole.
図13に示すように、圧電層21に貫通孔51を形成する。貫通孔51は、犠牲層50に至るように形成される。貫通孔51は、例えば、ドライエッチング法等により形成することができる。貫通孔51は、エッチングホールとして利用される。
As shown in FIG. 13, through holes 51 are formed in the piezoelectric layer 21. The through hole 51 is formed to reach the sacrificial layer 50. The through hole 51 can be formed by, for example, a dry etching method. The through hole 51 is used as an etching hole.
図14は、犠牲層を除去する工程の一例を模式的に示す断面図である。
FIG. 14 is a cross-sectional view schematically showing an example of the process of removing the sacrificial layer.
図14に示すように、貫通孔51を利用して、犠牲層50を除去する。犠牲層50の材料がZnOである場合、例えば、酢酸、リン酸及び水の混合溶液(酢酸:リン酸:水=1:1:10)を用いたウェットエッチングにより犠牲層50を除去することができる。
As shown in FIG. 14, the sacrificial layer 50 is removed using the through hole 51. When the material of the sacrificial layer 50 is ZnO, the sacrificial layer 50 can be removed, for example, by wet etching using a mixed solution of acetic acid, phosphoric acid, and water (acetic acid: phosphoric acid: water = 1:1:10). can.
犠牲層50が除去されることで、支持部材20に空洞部23が形成される。
By removing the sacrificial layer 50, a cavity 23 is formed in the support member 20.
以上により、弾性波装置10が得られる。
Through the above steps, the elastic wave device 10 is obtained.
図15は、本発明の第1実施形態に係る弾性波装置の別の一例を模式的に示す断面図である。
FIG. 15 is a cross-sectional view schematically showing another example of the elastic wave device according to the first embodiment of the present invention.
図15に示す弾性波装置10Bのように、支持部材20は、第1基板31を挟んで中間層41とは反対側に、Siからなる第2基板32をさらに含んでもよい。
As in the elastic wave device 10B shown in FIG. 15, the support member 20 may further include a second substrate 32 made of Si on the opposite side of the intermediate layer 41 with the first substrate 31 in between.
第2基板32の厚みは、第1基板31の厚みと同じでもよく、第1基板31の厚みより大きくてもよく、第1基板31の厚みより小さくてもよい。第2基板32の厚みは、圧電層21の厚みと同じでもよく、圧電層21の厚みより大きくてもよく、圧電層21の厚みより小さくてもよい。第2基板32の厚みは、中間層41の厚みと同じでもよく、中間層41の厚みより大きくてもよく、中間層41の厚みより小さくてもよい。
The thickness of the second substrate 32 may be the same as the thickness of the first substrate 31, may be greater than the thickness of the first substrate 31, or may be smaller than the thickness of the first substrate 31. The thickness of the second substrate 32 may be the same as the thickness of the piezoelectric layer 21, may be greater than the thickness of the piezoelectric layer 21, or may be smaller than the thickness of the piezoelectric layer 21. The thickness of the second substrate 32 may be the same as the thickness of the intermediate layer 41, may be greater than the thickness of the intermediate layer 41, or may be smaller than the thickness of the intermediate layer 41.
厚み方向から見たとき、第2基板32の外周縁は、第1基板31の外周縁よりも外側に位置することが好ましい。すなわち、厚み方向から見たとき、第2基板32の外周縁の内側に第1基板31の外周縁が収まっていることが好ましい。
It is preferable that the outer circumferential edge of the second substrate 32 be located outside the outer circumferential edge of the first substrate 31 when viewed from the thickness direction. That is, it is preferable that the outer periphery of the first substrate 31 is located inside the outer periphery of the second substrate 32 when viewed from the thickness direction.
第1基板31と第2基板32との間には、中間層42が設けられていてもよい。
An intermediate layer 42 may be provided between the first substrate 31 and the second substrate 32.
あるいは、第1基板31と第2基板32との間には、中間層42が設けられていなくてもよい。すなわち、第1基板31と第2基板32とが直接接合されていてもよい。
Alternatively, the intermediate layer 42 may not be provided between the first substrate 31 and the second substrate 32. That is, the first substrate 31 and the second substrate 32 may be directly bonded.
中間層42を構成する材料は、中間層41を構成する材料と同種の材料であることが好ましい。
The material constituting the intermediate layer 42 is preferably the same type of material as the material constituting the intermediate layer 41.
中間層42の厚みは、中間層41の厚みと同じでもよく、中間層41の厚みより大きくてもよく、中間層41の厚みより小さくてもよい。中間層42の厚みは、圧電層21の厚みと同じでもよく、圧電層21の厚みより大きくてもよく、圧電層21の厚みより小さくてもよい。中間層42の厚みは、第1基板31の厚みと同じでもよく、第1基板31の厚みより大きくてもよく、第1基板31の厚みより小さくてもよい。中間層42の厚みは、第2基板32の厚みと同じでもよく、第2基板32の厚みより大きくてもよく、第2基板32の厚みより小さくてもよい。
The thickness of the intermediate layer 42 may be the same as the thickness of the intermediate layer 41, may be greater than the thickness of the intermediate layer 41, or may be smaller than the thickness of the intermediate layer 41. The thickness of the intermediate layer 42 may be the same as the thickness of the piezoelectric layer 21, may be greater than the thickness of the piezoelectric layer 21, or may be smaller than the thickness of the piezoelectric layer 21. The thickness of the intermediate layer 42 may be the same as the thickness of the first substrate 31, may be greater than the thickness of the first substrate 31, or may be smaller than the thickness of the first substrate 31. The thickness of the intermediate layer 42 may be the same as the thickness of the second substrate 32, may be greater than the thickness of the second substrate 32, or may be smaller than the thickness of the second substrate 32.
[第2実施形態]
本発明の第2実施形態に係る弾性波装置では、支持部材は、第1基板を挟んで中間層とは反対側に、Siからなる第2基板をさらに含む。さらに、Si又は金属からなる第3基板が、空洞部とは反対側の圧電層の主面と対向するように圧電層と間隔を空けて設けられ、第2基板と第3基板とが金属接合によって気密封止されている。 [Second embodiment]
In the elastic wave device according to the second embodiment of the present invention, the support member further includes a second substrate made of Si on the opposite side of the intermediate layer with the first substrate in between. Furthermore, a third substrate made of Si or metal is provided with a gap between the piezoelectric layer and the main surface of the piezoelectric layer opposite to the cavity, and the second substrate and the third substrate are metal-bonded. Hermetically sealed.
本発明の第2実施形態に係る弾性波装置では、支持部材は、第1基板を挟んで中間層とは反対側に、Siからなる第2基板をさらに含む。さらに、Si又は金属からなる第3基板が、空洞部とは反対側の圧電層の主面と対向するように圧電層と間隔を空けて設けられ、第2基板と第3基板とが金属接合によって気密封止されている。 [Second embodiment]
In the elastic wave device according to the second embodiment of the present invention, the support member further includes a second substrate made of Si on the opposite side of the intermediate layer with the first substrate in between. Furthermore, a third substrate made of Si or metal is provided with a gap between the piezoelectric layer and the main surface of the piezoelectric layer opposite to the cavity, and the second substrate and the third substrate are metal-bonded. Hermetically sealed.
本発明の第2実施形態に係る弾性波装置では、第1実施形態と同様、機能電極が設けられている圧電層を、圧電層と同種の材料を含有する支持部材で保持することにより、両者の線膨張係数の差を小さくすることができる。これにより、圧電層の一部であるメンブレン部への応力を軽減し、圧電層に発生するクラックを防止することができる。
In the acoustic wave device according to the second embodiment of the present invention, as in the first embodiment, the piezoelectric layer provided with the functional electrode is held by a support member containing the same kind of material as the piezoelectric layer, so that both The difference in linear expansion coefficient can be reduced. This can reduce stress on the membrane portion, which is a part of the piezoelectric layer, and prevent cracks from occurring in the piezoelectric layer.
その一方、小型・低背構造を実現するために一般的に用いられるAu-Au接合又ははんだ接合等の金属接合でウェハ同士を貼り合わせる気密封止パッケージ構造では、支持部材が圧電層と同種の材料を含有する場合、支持基板として一般的なSi基板よりも抗折強度が弱いため、研削による薄型化が難しいという問題があった。
On the other hand, in the hermetically sealed package structure in which wafers are bonded together using metal bonding such as Au-Au bonding or solder bonding, which is generally used to realize a compact and low-profile structure, the supporting member is of the same type as the piezoelectric layer. In the case of containing a material, there is a problem in that it is difficult to reduce the thickness by grinding because the flexural strength is weaker than that of a Si substrate which is commonly used as a support substrate.
そこで、支持部材がSiからなる第2基板をさらに含み、Siからなる第2基板とSi又は金属からなる第3基板とが金属接合によって気密封止されることで、基板の研削性を向上させて、低背の気密封止パッケージ構造を実現することができる。
Therefore, the support member further includes a second substrate made of Si, and the second substrate made of Si and the third substrate made of Si or metal are hermetically sealed by metal bonding, thereby improving the grindability of the substrate. As a result, a low-profile, hermetically sealed package structure can be realized.
図16は、本発明の第2実施形態に係る弾性波装置の一例を模式的に示す断面図である。
FIG. 16 is a cross-sectional view schematically showing an example of an elastic wave device according to the second embodiment of the present invention.
図16に示す弾性波装置10Cは、支持部材20と、圧電層21と、機能電極22と、を備える。
The elastic wave device 10C shown in FIG. 16 includes a support member 20, a piezoelectric layer 21, and a functional electrode 22.
支持部材20は、空洞部23を一方主面(図16では上側の主面)に有する。
The support member 20 has a cavity 23 on one main surface (the upper main surface in FIG. 16).
圧電層21は、空洞部23を覆うように支持部材20の一方主面に設けられている。
The piezoelectric layer 21 is provided on one main surface of the support member 20 so as to cover the cavity 23.
機能電極22は、圧電層21の少なくとも一方の主面に設けられている。図16に示す例では、圧電層21の一方の主面(図16では上側の主面)に機能電極22が設けられている。
The functional electrode 22 is provided on at least one main surface of the piezoelectric layer 21. In the example shown in FIG. 16, the functional electrode 22 is provided on one main surface (the upper main surface in FIG. 16) of the piezoelectric layer 21.
機能電極22は、例えば、圧電層21の一方の主面に設けられたIDT電極である。
The functional electrode 22 is, for example, an IDT electrode provided on one main surface of the piezoelectric layer 21.
図16に示す例では、機能電極22には、バスバー電極及び配線電極24と、2層配線25とが接続されている。
In the example shown in FIG. 16, the functional electrode 22 is connected to a busbar electrode and wiring electrode 24, and a two-layer wiring 25.
支持部材20は、第1基板31と、第1基板31と圧電層21との間に設けられた中間層41と、を含む。
The support member 20 includes a first substrate 31 and an intermediate layer 41 provided between the first substrate 31 and the piezoelectric layer 21.
第1実施形態と同様、支持部材20は、圧電層21と同種の材料を含有する。第1基板31は、例えば、圧電層21と同種の材料からなる。中間層41は、例えば、二酸化ケイ素(SiO2)等の酸化ケイ素(SiOx)からなる。
Similar to the first embodiment, the support member 20 contains the same type of material as the piezoelectric layer 21. The first substrate 31 is made of the same kind of material as the piezoelectric layer 21, for example. The intermediate layer 41 is made of silicon oxide (SiO x ) such as silicon dioxide (SiO 2 ), for example.
支持部材20は、第1基板31を挟んで中間層41とは反対側に、Siからなる第2基板32をさらに含む。
The support member 20 further includes a second substrate 32 made of Si on the opposite side of the intermediate layer 41 with the first substrate 31 in between.
第1基板31と第2基板32との間には、中間層42が設けられていてもよく、中間層42が設けられていなくてもよい。
The intermediate layer 42 may be provided between the first substrate 31 and the second substrate 32, or the intermediate layer 42 may not be provided.
弾性波装置10Cは、Si又は金属からなる第3基板33をさらに備える。第3基板33は、空洞部23とは反対側の圧電層21の主面と対向するように圧電層21と間隔を空けて設けられている。
The elastic wave device 10C further includes a third substrate 33 made of Si or metal. The third substrate 33 is provided at a distance from the piezoelectric layer 21 so as to face the main surface of the piezoelectric layer 21 on the side opposite to the cavity 23 .
第3基板33は、例えば、Siからなる。その場合、第2基板32及び第3基板33は、いずれもSi基板である。
The third substrate 33 is made of, for example, Si. In that case, the second substrate 32 and the third substrate 33 are both Si substrates.
あるいは、第3基板33は、金属からなる。その場合、第3基板33は、例えば、Cu等からなる金属基板である。
Alternatively, the third substrate 33 is made of metal. In that case, the third substrate 33 is, for example, a metal substrate made of Cu or the like.
第3基板33の厚みは、第1基板31の厚みと同じでもよく、第1基板31の厚みより大きくてもよく、第1基板31の厚みより小さくてもよい。また、第3基板33の厚みは、第2基板32の厚みと同じでもよく、第2基板32の厚みより大きくてもよく、第2基板32の厚みより小さくてもよい。
The thickness of the third substrate 33 may be the same as the thickness of the first substrate 31, may be greater than the thickness of the first substrate 31, or may be smaller than the thickness of the first substrate 31. Further, the thickness of the third substrate 33 may be the same as the thickness of the second substrate 32, may be greater than the thickness of the second substrate 32, or may be smaller than the thickness of the second substrate 32.
図16に示すように、第2基板32と第3基板33とが金属接合によって気密封止されている。
As shown in FIG. 16, the second substrate 32 and the third substrate 33 are hermetically sealed by metal bonding.
金属接合は、例えば、Au-Au接合又ははんだ接合である。
The metal bond is, for example, Au-Au bond or solder bond.
図16に示す例では、金属シール35及びはんだシール37によって第2基板32と第3基板33とが気密封止されている。
In the example shown in FIG. 16, the second substrate 32 and the third substrate 33 are hermetically sealed by a metal seal 35 and a solder seal 37.
弾性波装置10Cは、機能電極22と電気的に接続されている端子電極45をさらに備える。
The elastic wave device 10C further includes a terminal electrode 45 that is electrically connected to the functional electrode 22.
図16に示す例では、端子電極45は、第1基板31とは反対側の第2基板32の表面に露出している。すなわち、端子電極45が第2基板32側に配置されている。
In the example shown in FIG. 16, the terminal electrode 45 is exposed on the surface of the second substrate 32 on the opposite side to the first substrate 31. That is, the terminal electrode 45 is arranged on the second substrate 32 side.
具体的には、端子電極45は、支持部材20を厚み方向に貫通するように設けられている。
Specifically, the terminal electrode 45 is provided so as to penetrate the support member 20 in the thickness direction.
第1基板31とは反対側の第2基板32の表面には、はんだボール47が設けられている。はんだボール47は、端子電極45及び2層配線25等を介して機能電極22と電気的に接続されている。
Solder balls 47 are provided on the surface of the second substrate 32 on the opposite side from the first substrate 31. The solder ball 47 is electrically connected to the functional electrode 22 via the terminal electrode 45, the two-layer wiring 25, and the like.
図17は、本発明の第2実施形態に係る弾性波装置の別の一例を模式的に示す断面図である。
FIG. 17 is a cross-sectional view schematically showing another example of the elastic wave device according to the second embodiment of the present invention.
図17に示す弾性波装置10Dのように、圧電層21、中間層41及び第1基板31の断面は、圧電層21側に向かってテーパー形状を有してもよい。第1基板31と第2基板32との間に中間層42が設けられている場合には、中間層42の断面も圧電層21側に向かってテーパー形状を有してもよい。このように、第2基板32を除く支持部材20及び圧電層21の断面は、圧電層21側に向かってテーパー形状を有してもよい。
As in the acoustic wave device 10D shown in FIG. 17, the cross sections of the piezoelectric layer 21, intermediate layer 41, and first substrate 31 may have a tapered shape toward the piezoelectric layer 21 side. When the intermediate layer 42 is provided between the first substrate 31 and the second substrate 32, the cross section of the intermediate layer 42 may also have a tapered shape toward the piezoelectric layer 21 side. In this way, the cross sections of the support member 20 and the piezoelectric layer 21 excluding the second substrate 32 may have a tapered shape toward the piezoelectric layer 21 side.
図18は、本発明の第2実施形態に係る弾性波装置のさらに別の一例を模式的に示す断面図である。
FIG. 18 is a cross-sectional view schematically showing still another example of the elastic wave device according to the second embodiment of the present invention.
図18に示す弾性波装置10Eでは、端子電極45は、圧電層21とは反対側の第3基板33の表面に露出している。すなわち、端子電極45が第3基板33側に配置されている。
In the acoustic wave device 10E shown in FIG. 18, the terminal electrode 45 is exposed on the surface of the third substrate 33 on the opposite side from the piezoelectric layer 21. That is, the terminal electrode 45 is arranged on the third substrate 33 side.
図18に示す例では、端子電極45は、第3基板33を厚み方向に貫通して、第1基板31側の第2基板32の表面に達している。そして、第1基板31側の第2基板32の表面にまで延びた2層配線25が端子電極45と接続されている。
In the example shown in FIG. 18, the terminal electrode 45 penetrates the third substrate 33 in the thickness direction and reaches the surface of the second substrate 32 on the first substrate 31 side. A two-layer wiring 25 extending to the surface of the second substrate 32 on the first substrate 31 side is connected to the terminal electrode 45.
圧電層21とは反対側の第3基板33の表面には、はんだボール47が設けられている。はんだボール47は、端子電極45及び2層配線25等を介して機能電極22と電気的に接続されている。
Solder balls 47 are provided on the surface of the third substrate 33 on the opposite side from the piezoelectric layer 21. The solder ball 47 is electrically connected to the functional electrode 22 via the terminal electrode 45, the two-layer wiring 25, and the like.
図18に示すように、圧電層21、中間層41及び第1基板31の断面は、圧電層21側に向かってテーパー形状を有してもよい。第1基板31と第2基板32との間に中間層42が設けられている場合には、中間層42の断面も圧電層21側に向かってテーパー形状を有してもよい。このように、第2基板32を除く支持部材20及び圧電層21の断面は、圧電層21側に向かってテーパー形状を有してもよい。
As shown in FIG. 18, the cross sections of the piezoelectric layer 21, intermediate layer 41, and first substrate 31 may have a tapered shape toward the piezoelectric layer 21 side. When the intermediate layer 42 is provided between the first substrate 31 and the second substrate 32, the cross section of the intermediate layer 42 may also have a tapered shape toward the piezoelectric layer 21 side. In this way, the cross sections of the support member 20 and the piezoelectric layer 21 excluding the second substrate 32 may have a tapered shape toward the piezoelectric layer 21 side.
[その他の実施形態]
本発明の弾性波装置は、上記実施形態に限定されるものではなく、弾性波装置の構成、製造条件等に関し、本発明の範囲内において、種々の応用、変形を加えることが可能である。 [Other embodiments]
The elastic wave device of the present invention is not limited to the above embodiments, and various applications and modifications can be made within the scope of the present invention regarding the configuration, manufacturing conditions, etc. of the elastic wave device.
本発明の弾性波装置は、上記実施形態に限定されるものではなく、弾性波装置の構成、製造条件等に関し、本発明の範囲内において、種々の応用、変形を加えることが可能である。 [Other embodiments]
The elastic wave device of the present invention is not limited to the above embodiments, and various applications and modifications can be made within the scope of the present invention regarding the configuration, manufacturing conditions, etc. of the elastic wave device.
本発明の第1実施形態及び第2実施形態では、支持部材の中間層側に空洞部が設けられているが、支持部材の第1基板側に空洞部が設けられていてもよい。
In the first and second embodiments of the present invention, the cavity is provided on the intermediate layer side of the support member, but the cavity may be provided on the first substrate side of the support member.
以下、本発明の第1実施形態に係る弾性波装置の変形例を説明するが、本発明の第2実施形態に係る弾性波装置についても同様である。
Hereinafter, a modification of the elastic wave device according to the first embodiment of the present invention will be described, but the same applies to the elastic wave device according to the second embodiment of the present invention.
図19は、本発明の第1実施形態に係る弾性波装置の第1変形例を模式的に示す断面図である。
FIG. 19 is a cross-sectional view schematically showing a first modification of the elastic wave device according to the first embodiment of the present invention.
図19に示す弾性波装置10Fでは、支持部材20の第1基板31側に空洞部23が設けられている。圧電層21と空洞部23との間には中間層41が設けられている。第1基板31は、例えば、圧電層21と同種の材料からなる。
In the elastic wave device 10F shown in FIG. 19, a cavity 23 is provided on the first substrate 31 side of the support member 20. An intermediate layer 41 is provided between the piezoelectric layer 21 and the cavity 23. The first substrate 31 is made of the same kind of material as the piezoelectric layer 21, for example.
後述するように、第1基板31にチタン(Ti)等の各種金属を熱で拡散させることにより、第1基板31側に空洞部23を形成することができる。
As will be described later, the cavity 23 can be formed on the first substrate 31 side by diffusing various metals such as titanium (Ti) into the first substrate 31 using heat.
図20は、本発明の第1実施形態に係る弾性波装置の第2変形例を模式的に示す断面図である。
FIG. 20 is a sectional view schematically showing a second modification of the elastic wave device according to the first embodiment of the present invention.
図20に示す弾性波装置10Gにおいても、支持部材20の第1基板31側に空洞部23が設けられている。図20に示すように、圧電層21と空洞部23との間に中間層41が設けられていなくてもよい。
Also in the elastic wave device 10G shown in FIG. 20, a cavity 23 is provided on the first substrate 31 side of the support member 20. As shown in FIG. 20, the intermediate layer 41 may not be provided between the piezoelectric layer 21 and the cavity 23.
図21A~図21Eは、支持部材の第1基板側に空洞部を形成する方法の一例を模式的に示す断面図である。
FIGS. 21A to 21E are cross-sectional views schematically showing an example of a method for forming a cavity on the first substrate side of the support member.
まず、図21Aに示すように、中間層41が表面に設けられた圧電基板30を用意する。
First, as shown in FIG. 21A, a piezoelectric substrate 30 having an intermediate layer 41 provided on its surface is prepared.
別途、図21Bに示すように、犠牲層50が埋め込まれた第1基板31を用意する。
Separately, as shown in FIG. 21B, a first substrate 31 in which a sacrificial layer 50 is embedded is prepared.
次に、図21Cに示すように、中間層41と犠牲層50とが向かい合うように圧電基板30と第1基板31とを原子拡散接合(Atomic Diffusion Bonding、ADB)により接合させる。
Next, as shown in FIG. 21C, the piezoelectric substrate 30 and the first substrate 31 are bonded by atomic diffusion bonding (ADB) so that the intermediate layer 41 and the sacrificial layer 50 face each other.
図21Cに示す例では、Ti等の金属層52を介して圧電基板30と第1基板31とが接合されている。
In the example shown in FIG. 21C, the piezoelectric substrate 30 and the first substrate 31 are bonded via a metal layer 52 such as Ti.
続いて、図21Dに示すように、接合された圧電基板30及び第1基板31に対して熱処理を行う。熱処理により、金属層52に含まれるTi等の金属は、第1基板31の圧電材料(ニオブ酸リチウム等)に拡散する。
Subsequently, as shown in FIG. 21D, heat treatment is performed on the joined piezoelectric substrate 30 and first substrate 31. Due to the heat treatment, metal such as Ti contained in the metal layer 52 is diffused into the piezoelectric material (lithium niobate, etc.) of the first substrate 31.
そして、図21Eに示すように、圧電基板30を薄化して圧電層21を形成し、機能電極22等の電極を形成する。その後、貫通孔51を利用して犠牲層50を除去する。犠牲層50上の金属層52は犠牲層50とともに除去される。これにより、支持部材20の第1基板31側に空洞部23が形成される。
Then, as shown in FIG. 21E, the piezoelectric substrate 30 is thinned to form the piezoelectric layer 21, and electrodes such as the functional electrode 22 are formed. Thereafter, the sacrificial layer 50 is removed using the through hole 51. The metal layer 52 on the sacrificial layer 50 is removed together with the sacrificial layer 50. As a result, a cavity 23 is formed on the first substrate 31 side of the support member 20.
以下において、第1基板に相当する支持基板の材料が圧電層と同種の材料に限定されない弾性波装置を例として用いて、厚み滑りモード及び板波を利用する弾性波装置の詳細を説明する。なお、以下においては、機能電極がIDT電極である場合の例を用いて説明する。
In the following, details of an elastic wave device that utilizes a thickness shear mode and a plate wave will be described using as an example an elastic wave device in which the material of the support substrate corresponding to the first substrate is not limited to the same type of material as the piezoelectric layer. Note that the following description uses an example in which the functional electrode is an IDT electrode.
図22は、厚み滑りモードのバルク波を利用する弾性波装置の一例の外観を示す略図的斜視図である。図23は、図22に示す弾性波装置の圧電層上の電極構造を示す平面図である。図24は、図22中のA-A線に沿う部分の断面図である。
FIG. 22 is a schematic perspective view showing the appearance of an example of an elastic wave device that utilizes bulk waves in thickness shear mode. FIG. 23 is a plan view showing the electrode structure on the piezoelectric layer of the acoustic wave device shown in FIG. 22. FIG. 24 is a cross-sectional view of a portion taken along line AA in FIG. 22.
弾性波装置1は、例えば、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又はLiTaO3のカット角は、例えばZカットであるが、回転Yカット又はXカットであってもよい。好ましくは、Y伝搬及びX伝搬±30°の伝搬方位が好ましい。圧電層2の厚みは、特に限定されないが、厚み滑りモードを効果的に励振するには、50nm以上、1000nm以下であることが好ましい。圧電層2は、対向し合う第1の主面2a及び第2の主面2bを有する。圧電層2の第1の主面2a上に、電極3及び電極4が設けられている。ここで電極3が「第1電極」の一例であり、電極4が「第2電極」の一例である。図22及び図23では、複数の電極3が、第1のバスバー電極5に接続されている複数の第1の電極指である。複数の電極4は、第2のバスバー電極6に接続されている複数の第2の電極指である。複数の電極3及び複数の電極4は、互いに間挿し合っている。電極3及び電極4は、矩形形状を有し、長さ方向を有する。この長さ方向と直交する方向において、電極3と、隣りの電極4とが対向している。これら複数の電極3、電極4、第1のバスバー電極5及び第2のバスバー電極6によりIDT(Interdigital Transducer)電極が構成されている。電極3,4の長さ方向、及び、電極3,4の長さ方向と直交する方向はいずれも、圧電層2の厚み方向に交差する方向である。このため、電極3と、隣りの電極4とは、圧電層2の厚み方向に交差する方向において対向しているともいえる。また、電極3,4の長さ方向が図22及び図23に示す電極3,4の長さ方向に直交する方向と入れ替わってもよい。すなわち、図22及び図23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3,4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22及び図23において電極3,4が延びている方向に延びることとなる。そして、一方電位に接続される電極3と、他方電位に接続される電極4とが隣り合う1対の構造が、上記電極3,4の長さ方向と直交する方向に、複数対設けられている。ここで電極3と電極4とが隣り合うとは、電極3と電極4とが直接接触するように配置されている場合ではなく、電極3と電極4とが間隔を介して配置されている場合を指す。また、電極3と電極4とが隣り合う場合、電極3と電極4との間には、他の電極3,4を含む、ホット電極又はグランド電極に接続される電極は配置されない。この対数は、整数対である必要はなく、1.5対又は2.5対などであってもよい。電極3,4間の中心間距離すなわちピッチは、1μm以上、10μm以下の範囲が好ましい。なお、電極3,4間の中心間距離とは、電極3の長さ方向と直交する方向における電極3の幅寸法の中心と、電極4の長さ方向と直交する方向における電極4の幅寸法の中心とを結んだ距離となる。さらに、電極3,4の少なくとも一方が複数本ある場合(電極3,4を一対の電極組とした場合に、1.5対以上の電極組がある場合)、電極3,4の中心間距離は、1.5対以上の電極3,4のうち隣り合う電極3,4それぞれの中心間距離の平均値を指す。また、電極3,4の幅、すなわち電極3,4の対向方向の寸法は、150nm以上、1000nm以下の範囲が好ましい。
The acoustic wave device 1 has a piezoelectric layer 2 made of, for example, LiNbO 3 . The piezoelectric layer 2 may be made of LiTaO 3 . The cut angle of LiNbO 3 or LiTaO 3 is, for example, a Z cut, but may also be a rotational Y cut or an X cut. Preferably, the propagation directions of Y propagation and X propagation are ±30°. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably 50 nm or more and 1000 nm or less. The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b that face each other. On the first main surface 2a of the piezoelectric layer 2, an electrode 3 and an electrode 4 are provided. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In FIGS. 22 and 23, the plurality of electrodes 3 are the plurality of first electrode fingers connected to the first busbar electrode 5. In FIGS. The plurality of electrodes 4 are a plurality of second electrode fingers connected to the second busbar electrode 6. The plurality of electrodes 3 and the plurality of electrodes 4 are interposed with each other. Electrode 3 and electrode 4 have a rectangular shape and have a length direction. The electrode 3 and the adjacent electrode 4 face each other in a direction perpendicular to this length direction. These plurality of electrodes 3, electrodes 4, first busbar electrodes 5, and second busbar electrodes 6 constitute an IDT (Interdigital Transducer) electrode. The length direction of the electrodes 3 and 4 and the direction perpendicular to the length direction of the electrodes 3 and 4 are both directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can be said that the electrode 3 and the adjacent electrode 4 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2. Further, the length direction of the electrodes 3 and 4 may be replaced with the direction perpendicular to the length direction of the electrodes 3 and 4 shown in FIGS. 22 and 23. That is, in FIGS. 22 and 23, the electrodes 3 and 4 may be extended in the direction in which the first busbar electrode 5 and the second busbar electrode 6 are extended. In that case, the first busbar electrode 5 and the second busbar electrode 6 will extend in the direction in which the electrodes 3 and 4 extend in FIGS. 22 and 23. A plurality of pairs of structures in which an electrode 3 connected to one potential and an electrode 4 connected to the other potential are adjacent to each other are provided in a direction perpendicular to the length direction of the electrodes 3 and 4. There is. Here, the expression "electrode 3 and electrode 4 are adjacent" does not mean that electrode 3 and electrode 4 are arranged so as to be in direct contact with each other, but when electrode 3 and electrode 4 are arranged with a gap between them. refers to Further, when the electrode 3 and the electrode 4 are adjacent to each other, no electrode connected to the hot electrode or the ground electrode, including the other electrodes 3 and 4, is arranged between the electrode 3 and the electrode 4. This logarithm does not need to be an integer pair, but may be 1.5 pairs, 2.5 pairs, or the like. The center-to-center distance between the electrodes 3 and 4, that is, the pitch, is preferably in the range of 1 μm or more and 10 μm or less. Note that the center-to-center distance between the electrodes 3 and 4 refers to the center of the width dimension of the electrode 3 in the direction orthogonal to the length direction of the electrode 3, and the width dimension of the electrode 4 in the direction orthogonal to the length direction of the electrode 4. It is the distance between the center of Furthermore, if there is a plurality of at least one of the electrodes 3 and 4 (when the electrodes 3 and 4 are a pair of electrode sets, and there are 1.5 or more pairs of electrode sets), the distance between the centers of the electrodes 3 and 4 refers to the average value of the distance between the centers of adjacent electrodes 3 and 4 among 1.5 or more pairs of electrodes 3 and 4. Further, the width of the electrodes 3 and 4, that is, the dimension in the opposing direction of the electrodes 3 and 4, is preferably in the range of 150 nm or more and 1000 nm or less.
本実施形態において、Zカットの圧電層を用いる場合、電極3,4の長さ方向と直交する方向は、圧電層2の分極方向に直交する方向となる。圧電層2として他のカット角の圧電体を用いた場合には、この限りでない。ここにおいて、「直交」とは、厳密に直交する場合のみに限定されず、略直交(電極3,4の長さ方向と直交する方向と分極方向とのなす角度が例えば90°±10°)でもよい。
In this embodiment, when using a Z-cut piezoelectric layer, the direction perpendicular to the length direction of the electrodes 3 and 4 is the direction perpendicular to the polarization direction of the piezoelectric layer 2. This is not the case when a piezoelectric material having a different cut angle is used as the piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal, but approximately orthogonal (for example, the angle between the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is 90°±10°) But that's fine.
圧電層2の第2の主面2b側には、中間層(接合層とも呼ばれる)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24に示すように、開口部7a,8aを有する。それによって、空洞部9が形成されている。空洞部9は、圧電層2の励振領域C(図23参照)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3,4が設けられている部分と重ならない位置において、第2の主面2bに中間層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に直接または間接に積層され得る。
A support substrate 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an intermediate layer (also called a bonding layer) 7 interposed therebetween. The intermediate layer 7 and the support substrate 8 have a frame-like shape, and have openings 7a and 8a, as shown in FIG. Thereby, a cavity 9 is formed. The cavity 9 is provided so as not to hinder the vibration of the excitation region C (see FIG. 23) 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 that does not overlap with the portion where at least one pair of electrodes 3 and 4 are provided. Note that the intermediate layer 7 may not be provided. Therefore, the support substrate 8 can be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2.
中間層7は、例えば、酸化ケイ素からなる。もっとも、酸化ケイ素の他、酸窒化ケイ素、アルミナなどの適宜の絶縁性材料を用いることができる。支持基板8は、Siからなる。Siの圧電層2側の面における面方位は(100)又は(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 intermediate layer 7 is made of silicon oxide, for example. However, other than silicon oxide, an appropriate insulating material such as silicon oxynitride or alumina can be used. The support substrate 8 is made of Si. The plane orientation of the Si surface on the piezoelectric layer 2 side may be (100), (110), or (111). Preferably, Si has a high resistivity of 4 kΩ or more. However, the support substrate 8 can also be constructed using an appropriate insulating material or semiconductor material. Examples of materials for the support substrate 8 include aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and starch. Various ceramics such as tite and forsterite, dielectrics such as diamond and glass, semiconductors such as gallium nitride, etc. can be used.
上記複数の電極3、電極4、第1のバスバー電極5及び第2のバスバー電極6は、Al、AlCu合金などの適宜の金属もしくは合金からなる。本実施形態では、電極3、電極4、第1のバスバー電極5及び第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 electrodes 3, electrodes 4, first busbar electrode 5, and second busbar electrode 6 are made of an appropriate metal or alloy such as Al or AlCu alloy. In this embodiment, the electrode 3, the electrode 4, the first busbar electrode 5, and the second busbar electrode 6 have a structure in which an Al film is laminated on a Ti film. Note that an adhesive layer other than the Ti film may be used.
駆動に際しては、複数の電極3と、複数の電極4との間に交流電圧を印加する。より具体的には、第1のバスバー電極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。また、弾性波装置1では、圧電層2の厚みをd、複数対の電極3,4のうちいずれかの隣り合う電極3,4の中心間距離をpとした場合、d/pは0.5以下とされている。そのため、上記厚み滑り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。なお、本実施形態のように電極3,4の少なくとも一方が複数本ある場合、すなわち、電極3,4を1対の電極組とした場合に電極3,4が1.5対以上ある場合、隣り合う電極3,4の中心間距離pは、各隣り合う電極3,4の中心間距離の平均距離となる。
During driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 6. Thereby, it is possible to obtain resonance characteristics using the thickness shear mode bulk wave excited in the piezoelectric layer 2. Further, in the acoustic wave device 1, when the thickness of the piezoelectric layer 2 is d, and the distance between the centers of any adjacent electrodes 3, 4 among the plurality of pairs of electrodes 3, 4 is p, d/p is 0. It is considered to be 5 or less. Therefore, the bulk wave in the thickness shear mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d/p is 0.24 or less, in which case even better resonance characteristics can be obtained. Note that when there is a plurality of at least one of the electrodes 3 and 4 as in this embodiment, that is, when there are 1.5 or more pairs of electrodes 3 and 4 when the electrodes 3 and 4 are one pair of electrodes, The distance p between the centers of the adjacent electrodes 3 and 4 is the average distance between the centers of the adjacent electrodes 3 and 4.
本実施形態の弾性波装置1では、上記構成を備えるため、小型化を図ろうとして、電極3,4の対数を小さくしたとしても、Q値の低下が生じ難い。これは、両側に反射器を必要としない共振器であり、伝搬ロスが少ないためである。また、上記反射器を必要としないのは、厚み滑りモードのバルク波を利用していることによる。従来の弾性波装置で利用したラム波と、上記厚み滑りモードのバルク波の相違を、図25及び図26を参照して説明する。
Since the elastic wave device 1 of this embodiment has the above configuration, even if the logarithm of the electrodes 3 and 4 is reduced in an attempt to achieve miniaturization, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides and has little propagation loss. Further, the reason why the reflector is not required is because the bulk wave in the thickness shear mode is used. The difference between the Lamb wave used in a conventional elastic wave device and the thickness-shear mode bulk wave will be explained with reference to FIGS. 25 and 26.
図25は、弾性波装置の圧電膜を伝搬するラム波を説明するための模式的正面断面図である。図25に示すように、特許文献1(日本公開特許公報 特開2012-257019号公報)に記載のような弾性波装置では、圧電膜201中を矢印で示すように波が伝搬する。ここで、圧電膜201では、第1の主面201aと、第2の主面201bとが対向しており、第1の主面201aと第2の主面201bとを結ぶ厚み方向がZ方向である。X方向は、IDT電極の電極指が並んでいる方向である。図25に示すように、ラム波では、波が図示のように、X方向に伝搬していく。板波であるため、圧電膜201が全体として振動するものの、波はX方向に伝搬するため、両側に反射器を配置して、共振特性を得ている。そのため、波の伝搬ロスが生じ、小型化を図った場合、すなわち電極指の対数を少なくした場合、Q値が低下する。
FIG. 25 is a schematic front sectional view for explaining Lamb waves propagating through the piezoelectric film of the acoustic wave device. As shown in FIG. 25, in the elastic wave device described in Patent Document 1 (Japanese Patent Publication No. 2012-257019), waves propagate in the piezoelectric film 201 as indicated by arrows. Here, in the piezoelectric film 201, the first main surface 201a and the second main surface 201b are opposite to each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. It is. The X direction is the direction in which the electrode fingers of the IDT electrodes are lined up. As shown in FIG. 25, in the Lamb wave, the wave propagates in the X direction as shown. Since it is a plate wave, the piezoelectric film 201 vibrates as a whole, but since the wave propagates in the X direction, reflectors are placed 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 electrode fingers is reduced, the Q value decreases.
これに対して、図26は、弾性波装置の圧電層を伝播する厚み滑りモードのバルク波を説明するための模式的正面断面図である。図26に示すように、本実施形態の弾性波装置1では、振動変位は厚み滑り方向であるから、波は、圧電層2の第1の主面2aと第2の主面2bとを結ぶ方向、すなわちZ方向にほぼ伝搬し、共振する。すなわち、波のX方向成分がZ方向成分に比べて著しく小さい。そして、このZ方向の波の伝搬により共振特性が得られるため、反射器を必要としない。よって、反射器に伝搬する際の伝搬損失は生じない。従って、小型化を進めようとして、電極3,4からなる電極対の対数を減らしたとしても、Q値の低下が生じ難い。
On the other hand, FIG. 26 is a schematic front cross-sectional view for explaining a thickness-shear mode bulk wave propagating through a piezoelectric layer of an elastic wave device. As shown in FIG. 26, in the elastic wave device 1 of this embodiment, since the vibration displacement is in the thickness-slip direction, the waves connect the first main surface 2a and the second main surface 2b of the piezoelectric layer 2. It propagates almost in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Since resonance characteristics are obtained by the propagation of waves in the Z direction, a reflector is not required. Therefore, no propagation loss occurs when propagating to the reflector. Therefore, even if the number of electrode pairs consisting of electrodes 3 and 4 is reduced in an attempt to promote miniaturization, the Q value is unlikely to decrease.
図27は、厚み滑りモードのバルク波の振幅方向を示す図である。厚み滑りモードのバルク波の振幅方向は、図27に示すように、圧電層2の励振領域Cに含まれる第1領域451と、励振領域Cに含まれる第2領域452とで逆になる。図27では、電極3と電極4との間に、電極4が電極3よりも高電位となる電圧が印加された場合のバルク波を模式的に示してある。第1領域451は、励振領域Cのうち、圧電層2の厚み方向に直交し圧電層2を2分する仮想平面VP1と、第1の主面2aとの間の領域である。第2領域452は、励振領域Cのうち、仮想平面VP1と、第2の主面2bとの間の領域である。
FIG. 27 is a diagram showing the amplitude direction of the bulk wave in the thickness shear mode. As shown in FIG. 27, the amplitude direction of the bulk wave in the thickness shear mode is opposite between the first region 451 included in the excitation region C of the piezoelectric layer 2 and the second region 452 included in the excitation region C. FIG. 27 schematically shows a bulk wave when a voltage is applied between electrode 3 and electrode 4 such that electrode 4 has a higher potential than electrode 3. In FIG. The first region 451 is a region of the excitation region C between a 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 452 is a region of the excitation region C between the virtual plane VP1 and the second principal surface 2b.
上記のように、弾性波装置1では、電極3と電極4とからなる少なくとも1対の電極が配置されているが、X方向に波を伝搬させるものではないため、この電極3,4からなる電極対の対数は複数対ある必要は必ずしもない。すなわち、少なくとも1対の電極が設けられてさえおればよい。
As mentioned above, in the elastic wave device 1, at least one pair of electrodes consisting of the electrode 3 and the electrode 4 are arranged, but since the wave is not propagated in the X direction, the elastic wave device 1 is made up of the electrodes 3 and 4. There does not necessarily have to be a plurality of pairs of electrodes. That is, it is only necessary that at least one pair of electrodes be provided.
例えば、上記電極3がホット電位に接続される電極であり、電極4がグランド電位に接続される電極である。もっとも、電極3がグランド電位に、電極4がホット電位に接続されてもよい。本実施形態では、少なくとも1対の電極は、上記のように、ホット電位に接続される電極またはグランド電位に接続される電極であり、浮き電極は設けられていない。
For example, the electrode 3 is an electrode connected to a hot potential, and the electrode 4 is an electrode connected to a ground potential. However, the electrode 3 may be connected to the ground potential, and the electrode 4 may be connected to the hot potential. In this embodiment, at least one pair of electrodes is an electrode connected to a hot potential or an electrode connected to a ground potential, as described above, and no floating electrode is provided.
図28は、図22に示す弾性波装置の共振特性の一例を示す図である。なお、この共振特性を得た弾性波装置1の設計パラメータは以下の通りである。
FIG. 28 is a diagram showing an example of the resonance characteristics of the elastic wave device shown in FIG. 22. Note that the design parameters of the elastic wave device 1 that obtained this resonance characteristic are as follows.
圧電層2:オイラー角(0°,0°,90°)のLiNbO3、厚み=400nm。
電極3と電極4の長さ方向と直交する方向に視たときに、電極3と電極4とが重なっている領域、すなわち励振領域Cの長さ=40μm、電極3,4からなる電極の対数=21対、電極間中心距離=3μm、電極3,4の幅=500nm、d/p=0.133。
中間層7:1μmの厚みの酸化ケイ素膜。
支持基板8:Si基板。 Piezoelectric layer 2: LiNbO 3 with Euler angles (0°, 0°, 90°), thickness = 400 nm.
When viewed in a direction perpendicular to the length direction of electrodes 3 and 4, the area where electrodes 3 and 4 overlap, that is, the length of excitation area C = 40 μm, the logarithm of electrodes consisting of electrodes 3 and 4 = 21 pairs, center distance between electrodes = 3 μm, width of electrodes 3 and 4 = 500 nm, d/p = 0.133.
Intermediate layer 7: silicon oxide film with a thickness of 1 μm.
Support substrate 8: Si substrate.
電極3と電極4の長さ方向と直交する方向に視たときに、電極3と電極4とが重なっている領域、すなわち励振領域Cの長さ=40μm、電極3,4からなる電極の対数=21対、電極間中心距離=3μm、電極3,4の幅=500nm、d/p=0.133。
中間層7:1μmの厚みの酸化ケイ素膜。
支持基板8:Si基板。 Piezoelectric layer 2: LiNbO 3 with Euler angles (0°, 0°, 90°), thickness = 400 nm.
When viewed in a direction perpendicular to the length direction of
Intermediate layer 7: silicon oxide film with a thickness of 1 μm.
Support substrate 8: Si substrate.
なお、励振領域Cの長さとは、励振領域Cの電極3,4の長さ方向に沿う寸法である。
Note that the length of the excitation region C is a dimension along the length direction of the electrodes 3 and 4 of the excitation region C.
弾性波装置1では、電極3,4からなる電極対の電極間距離は、複数対において全て等しくした。すなわち、電極3と電極4とを等ピッチで配置した。
In the elastic wave device 1, the distances between the electrode pairs made up of the electrodes 3 and 4 were all equal in multiple pairs. That is, the electrodes 3 and 4 were arranged at equal pitches.
図28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. 28, good resonance characteristics with a fractional band of 12.5% are obtained despite not having a reflector.
ところで、上記圧電層2の厚みをd、電極3と電極4との電極の中心間距離をpとした場合、前述したように、本実施形態では、好ましくは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29を参照して説明する。
By the way, if the thickness of the piezoelectric layer 2 is d, and the center-to-center distance between the electrodes 3 and 4 is p, then in this embodiment, as described above, d/p is preferably 0.5 or less, More preferably it is 0.24 or less. This will be explained with reference to FIG. 29.
図28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29は、隣り合う電極の中心間距離をp、圧電層の厚みをdとした場合のd/2pと、弾性波装置の共振子としての比帯域との関係を示す図である。
A plurality of elastic wave devices were obtained in the same manner as the elastic wave device that obtained the resonance characteristics shown in FIG. 28, except that d/2p was changed. FIG. 29 is a diagram showing the relationship between d/2p and the fractional band as a resonator of an acoustic wave device, where p is the distance between the centers of adjacent electrodes and d is the thickness of the piezoelectric layer.
図29から明らかなように、d/2pが0.25を超えると、すなわちd/p>0.5では、d/pを調整しても、比帯域は5%未満である。これに対して、d/2p≦0.25、すなわちd/p≦0.5の場合には、その範囲内でd/pを変化させれば、比帯域を5%以上とすることができ、すなわち高い結合係数を有する共振子を構成することができる。また、d/2pが0.12以下の場合、すなわちd/pが0.24以下の場合には、比帯域を7%以上と高めることができる。加えて、d/pをこの範囲内で調整すれば、より一層比帯域の広い共振子を得ることができ、より一層高い結合係数を有する共振子を実現することができる。従って、d/pを0.5以下とすることにより、上記厚み滑りモードのバルク波を利用した、高い結合係数を有する共振子を構成し得ることがわかる。
As is clear from FIG. 29, when d/2p exceeds 0.25, that is, when d/p>0.5, the fractional band is less than 5% even if d/p is adjusted. On the other hand, if d/2p≦0.25, that is, d/p≦0.5, the fractional bandwidth can be increased to 5% or more by changing d/p within that range. In other words, 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 fractional band can be increased to 7% or more. In addition, by adjusting d/p within this range, it is possible to obtain a resonator with an even wider specific band, and it is possible to realize a resonator with an even higher coupling coefficient. Therefore, it can be seen that by setting d/p to 0.5 or less, it is possible to construct a resonator that utilizes the bulk wave of the thickness shear mode and has a high coupling coefficient.
なお、前述したように、少なくとも1対の電極は、1対でもよく、上記pは、1対の電極の場合、隣り合う電極3,4の中心間距離とする。また、1.5対以上の電極の場合には、隣り合う電極3,4の中心間距離の平均距離をpとすればよい。
Note that, as described above, the at least one pair of electrodes may be one pair, and in the case of one pair of electrodes, the above p is the distance between the centers of adjacent electrodes 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, the average distance between the centers of adjacent electrodes 3 and 4 may be set to p.
また、圧電層の厚みdについては、圧電層2が厚みばらつきを有する場合、その厚みを平均化した値を採用すればよい。
Further, regarding the thickness d of the piezoelectric layer, if the piezoelectric layer 2 has thickness variations, a value obtained by averaging the thicknesses may be adopted.
図30は、厚み滑りモードのバルク波を利用する弾性波装置の別の一例の平面図である。
FIG. 30 is a plan view of another example of an elastic wave device that utilizes bulk waves in thickness-shear mode.
弾性波装置61では、圧電層2の第1の主面2a上において、電極3と電極4とを有する1対の電極が設けられている。なお、図30中のKが交差幅となる。前述したように、本実施形態の弾性波装置では、電極の対数は1対であってもよい。この場合においても、上記d/pが0.5以下であれば、厚み滑りモードのバルク波を効果的に励振することができる。
In the elastic wave device 61, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first main surface 2a of the piezoelectric layer 2. Note that K in FIG. 30 is the intersection width. As described above, in the elastic wave device of this embodiment, the number of pairs of electrodes may be one. Even in this case, if the above-mentioned d/p is 0.5 or less, bulk waves in the thickness shear mode can be excited effectively.
本実施形態の弾性波装置では、好ましくは、複数の電極3,4において、いずれかの隣り合う電極3,4が対向している方向に視たときに重なっている領域である励振領域に対する、上記隣り合う電極3,4のメタライゼーション比MRが、MR≦1.75(d/p)+0.075を満たすことが望ましい。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31及び図32を参照して説明する。
In the elastic wave device of this embodiment, preferably, in the plurality of electrodes 3 and 4, for an excitation region that is an overlapping region when viewed in the direction in which any of the adjacent electrodes 3 and 4 are facing each other, It is desirable that the metallization ratio MR of the adjacent electrodes 3 and 4 satisfies MR≦1.75(d/p)+0.075. In that case, spurious can be effectively reduced. This will be explained with reference to FIGS. 31 and 32.
図31は、図22に示す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. 31 is a reference diagram showing an example of the resonance characteristics of the elastic wave device shown in FIG. 22. A spurious signal indicated by arrow B appears between the resonant frequency and the anti-resonant frequency. Note that d/p=0.08 and the Euler angles of LiNbO 3 (0°, 0°, 90°). Further, the metallization ratio MR was set to 0.35.
メタライゼーション比MRを、図23を参照して説明する。図23の電極構造において、1対の電極3,4に着目した場合、この1対の電極3,4のみが設けられるとする。この場合、一点鎖線Cで囲まれた部分が励振領域となる。この励振領域とは、電極3と電極4とを、電極3,4の長さ方向と直交する方向すなわち対向方向に視たときに電極3における電極4と重なり合っている領域、電極4における電極3と重なり合っている領域、及び、電極3と電極4との間の領域における電極3と電極4とが重なり合っている領域である。そして、この励振領域の面積に対する、励振領域C内の電極3,4の面積が、メタライゼーション比MRとなる。すなわち、メタライゼーション比MRは、メタライゼーション部分の面積の励振領域の面積に対する比である。
The metallization ratio MR will be explained with reference to FIG. 23. In the electrode structure of FIG. 23, when focusing on a pair of electrodes 3 and 4, it is assumed that only this pair of electrodes 3 and 4 are provided. In this case, the area surrounded by the dashed line C becomes the excitation region. This excitation region is the region where the electrode 3 overlaps the electrode 4 when the electrode 3 and the electrode 4 are viewed in a direction perpendicular to the length direction of the electrodes 3 and 4, that is, in a direction in which they face each other. and a region between electrodes 3 and 4 where electrodes 3 and 4 overlap. Then, the area of the electrodes 3 and 4 in the excitation region C with respect to the area of this excitation region becomes the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallized portion to the area of the excitation region.
なお、複数対の電極が設けられている場合、励振領域の面積の合計に対する全励振領域に含まれているメタライゼーション部分の割合をMRとすればよい。
Note that when multiple pairs of electrodes are provided, MR may be the ratio of the metallized portion included in all the excitation regions to the total area of the excitation regions.
図32は、本実施形態に従って、多数の弾性波共振子を構成した場合の比帯域と、スプリアスの大きさとしての180度で規格化されたスプリアスのインピーダンスの位相回転量との関係を示す図である。なお、比帯域については、圧電層の膜厚や電極の寸法を種々変更し、調整した。また、図32は、ZカットのLiNbO3からなる圧電層を用いた場合の結果であるが、他のカット角の圧電層を用いた場合においても、同様の傾向となる。
FIG. 32 is a diagram showing the relationship between the fractional band and the amount of phase rotation of spurious impedance normalized by 180 degrees as the magnitude of spurious when a large number of elastic wave resonators are configured according to the present embodiment. It is. Note that the specific band was adjusted by variously changing the thickness of the piezoelectric layer and the dimensions of the electrode. Furthermore, although FIG. 32 shows the results when a Z-cut piezoelectric layer made of LiNbO 3 is used, the same tendency occurs even when piezoelectric layers with other cut angles are used.
図32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32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31に示す共振特性のように、矢印Bで示す大きなスプリアスが帯域内に現れる。よって、比帯域は17%以下であることが好ましい。この場合には、圧電層2の膜厚や電極3,4の寸法などを調整することにより、スプリアスを小さくすることができる。
In the region surrounded by the ellipse J in FIG. 32, the spurious is as large as 1.0. As is clear from FIG. 32, when the fractional band exceeds 0.17, that is, exceeds 17%, a large spurious with a spurious level of 1 or more will affect the pass band even if the parameters constituting the fractional band are changed. Appear within. That is, as in the resonance characteristic shown in FIG. 31, a large spurious signal indicated by arrow B appears within the band. Therefore, it is preferable that the fractional band is 17% or less. In this case, by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, etc., the spurious can be reduced.
図33は、d/2pと、メタライゼーション比MRと、比帯域との関係を示す図である。上記弾性波装置において、d/2pと、MRが異なる様々な弾性波装置を構成し、比帯域を測定した。
FIG. 33 is a diagram showing the relationship between d/2p, metallization ratio MR, and fractional band. Among the above elastic wave devices, various elastic wave devices having different d/2p and MR were constructed and the fractional bands were measured.
図33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33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。
The hatched area on the right side of the broken line D in FIG. 33 is the area where the fractional band is 17% or less. The boundary between the hatched area and the unhatched area is expressed as 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 band to 17% or less. More preferably, it is the region to the right of MR=3.5(d/2p)+0.05 indicated by the dashed line D1 in FIG. That is, if MR≦1.75(d/p)+0.05, the fractional band can be reliably set to 17% or less.
図34は、d/pを限りなく0に近づけた場合のLiNbO3のオイラー角(0°,θ,ψ)に対する比帯域のマップを示す図である。
FIG. 34 is a diagram showing a map of fractional bands with respect to Euler angles (0°, θ, ψ) of LiNbO 3 when d/p is brought as close to 0 as possible.
図34のハッチングを付して示した部分が、少なくとも5%以上の比帯域が得られる領域であり、当該領域の範囲を近似すると、下記の式(1)、式(2)及び式(3)で表される範囲となる。
(0°±10°,0°~20°,任意のψ) …式(1)
(0°±10°,20°~80°,0°~60°(1-(θ-50)2/900)1/2) または (0°±10°,20°~80°,[180°-60°(1-(θ-50)2/900)1/2]~180°) …式(2)
(0°±10°,[180°-30°(1-(ψ-90)2/8100)1/2]~180°,任意のψ) …式(3)
従って、上記式(1)、式(2)または式(3)のオイラー角範囲の場合、比帯域を十分に広くすることができるため好ましい。 The hatched areas in FIG. 34 are regions where a fractional band of at least 5% can be obtained, and the range of these regions can be approximated by the following equations (1), (2), and (3). ).
(0°±10°, 0° to 20°, arbitrary ψ) ...Formula (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°) ...Formula (2)
(0°±10°, [180°-30° (1-(ψ-90) 2 /8100) 1/2 ] ~ 180°, arbitrary ψ) ...Formula (3)
Therefore, the Euler angle range of formula (1), formula (2), or formula (3) above is preferable because the fractional band can be made sufficiently wide.
(0°±10°,0°~20°,任意のψ) …式(1)
(0°±10°,20°~80°,0°~60°(1-(θ-50)2/900)1/2) または (0°±10°,20°~80°,[180°-60°(1-(θ-50)2/900)1/2]~180°) …式(2)
(0°±10°,[180°-30°(1-(ψ-90)2/8100)1/2]~180°,任意のψ) …式(3)
従って、上記式(1)、式(2)または式(3)のオイラー角範囲の場合、比帯域を十分に広くすることができるため好ましい。 The hatched areas in FIG. 34 are regions where a fractional band of at least 5% can be obtained, and the range of these regions can be approximated by the following equations (1), (2), and (3). ).
(0°±10°, 0° to 20°, arbitrary ψ) ...Formula (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°) ...Formula (2)
(0°±10°, [180°-30° (1-(ψ-90) 2 /8100) 1/2 ] ~ 180°, arbitrary ψ) ...Formula (3)
Therefore, the Euler angle range of formula (1), formula (2), or formula (3) above is preferable because the fractional band can be made sufficiently wide.
図35は、ラム波を利用する弾性波装置の一例を説明するための部分切り欠き斜視図である。
FIG. 35 is a partially cutaway perspective view for explaining an example of an elastic wave device that utilizes Lamb waves.
弾性波装置81は、支持基板82を有する。支持基板82には、上面に開いた凹部が設けられている。支持基板82上に圧電層83が積層されている。それによって、空洞部9が構成されている。この空洞部9の上方において圧電層83上に、IDT電極84が設けられている。IDT電極84の弾性波伝搬方向両側に、反射器85,86が設けられている。図35において、空洞部9の外周縁を破線で示す。ここでは、IDT電極84は、第1のバスバー電極84aと、第2のバスバー電極84bと、複数本の第1の電極指としての電極84cと、複数本の第2の電極指としての電極84dとを有する。複数本の電極84cは、第1のバスバー電極84aに接続されている。複数本の電極84dは、第2のバスバー電極84bに接続されている。複数本の電極84cと、複数本の電極84dとは間挿し合っている。
The elastic wave device 81 has a support substrate 82. The support substrate 82 is provided with an open recess on the upper surface. A piezoelectric layer 83 is laminated on the support substrate 82 . Thereby, a cavity 9 is formed. An IDT electrode 84 is provided on the piezoelectric layer 83 above the cavity 9 . Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction. In FIG. 35, the outer periphery of the cavity 9 is shown by a broken line. Here, the IDT electrode 84 includes a first busbar electrode 84a, a second busbar electrode 84b, an electrode 84c as a plurality of first electrode fingers, and an electrode 84d as a plurality of second electrode fingers. and has. The plurality of electrodes 84c are connected to the first busbar electrode 84a. The plurality of electrodes 84d are connected to the second busbar electrode 84b. The plurality of electrodes 84c and the plurality of electrodes 84d are interposed with each other.
弾性波装置81では、上記空洞部9上のIDT電極84に、交流電界を印加することにより、板波としてのラム波が励振される。そして、反射器85,86が両側に設けられているため、上記ラム波による共振特性を得ることができる。
In the elastic wave device 81, by applying an alternating current electric field to the IDT electrode 84 on the cavity 9, a Lamb wave as a plate wave is excited. Since the reflectors 85 and 86 are provided on both sides, the resonance characteristic due to the Lamb wave described above can be obtained.
このように、本発明の弾性波装置は、ラム波等の板波を利用するものであってもよい。
In this way, the elastic wave device of the present invention may utilize plate waves such as Lamb waves.
また、本発明の弾性波装置は、バルク波を利用するものであってもよい。すなわち、本発明の弾性波装置は、バルク弾性波(BAW)素子にも適用できる。この場合、機能電極は、上部電極及び下部電極である。
Furthermore, the elastic wave device of the present invention may utilize bulk waves. That is, the elastic wave device of the present invention can also be applied to a bulk acoustic wave (BAW) element. In this case, the functional electrodes are an upper electrode and a lower electrode.
図36は、バルク波を利用する弾性波装置の一例を模式的に示す断面図である。
FIG. 36 is a cross-sectional view schematically showing an example of an elastic wave device that uses bulk waves.
弾性波装置90は、支持基板91を備える。支持基板91を貫通するように空洞部93が設けられている。支持基板91上に圧電層92が積層されている。圧電層92の第1の主面92aには上部電極94が設けられ、圧電層92の第2の主面92bには下部電極95が設けられている。図示されていないが、支持基板91と圧電層92との間には、中間層が設けられていてもよい。
The elastic wave device 90 includes a support substrate 91. A cavity 93 is provided so as to penetrate the support substrate 91. A piezoelectric layer 92 is laminated on a support substrate 91 . An upper electrode 94 is provided on the first main surface 92a of the piezoelectric layer 92, and a lower electrode 95 is provided on the second main surface 92b of the piezoelectric layer 92. Although not shown, an intermediate layer may be provided between the support substrate 91 and the piezoelectric layer 92.
1 弾性波装置
2 圧電層
2a 圧電層の第1の主面
2b 圧電層の第2の主面
3 第1電極
4 第2電極
5 第1のバスバー電極
6 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 空洞部
10、10A、10B、10C、10D、10E、10F、10G 弾性波装置
20 支持部材
21 圧電層
21M メンブレン部
22 機能電極
23 空洞部
24 バスバー電極及び配線電極
24A 1層電極
25 2層配線
25A 2層電極
30 圧電基板
31 第1基板
32 第2基板
33 第3基板
35 金属シール
37 はんだシール
41、42 中間層
45 端子電極
47 はんだボール
50 犠牲層
51 貫通孔
52 金属層
61 弾性波装置
81 弾性波装置
82 支持基板
83 圧電層
84 IDT電極
84a 第1のバスバー電極
84b 第2のバスバー電極
84c 第1電極(第1電極指)
84d 第2電極(第2電極指)
85、86 反射器
90 弾性波装置
91 支持基板
92 圧電層
92a 圧電層の第1の主面
92b 圧電層の第2の主面
93 空洞部
94 上部電極
95 下部電極
201 圧電膜
201a 圧電膜の第1の主面
201b 圧電膜の第2の主面
451 第1領域
452 第2領域
C 励振領域
VP1 仮想平面 1Acoustic wave device 2 Piezoelectric layer 2a First main surface of piezoelectric layer 2b Second main surface of piezoelectric layer 3 First electrode 4 Second electrode 5 First busbar electrode 6 Second busbar electrode 7 Intermediate layer 7a Opening Part 8 Support substrate 8a Opening 9 Cavity 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G Acoustic wave device 20 Support member 21 Piezoelectric layer 21M Membrane section 22 Functional electrode 23 Cavity 24 Bus bar electrode and wiring electrode 24A 1st layer electrode 25 2nd layer wiring 25A 2nd layer electrode 30 Piezoelectric substrate 31 1st substrate 32 2nd substrate 33 3rd substrate 35 Metal seal 37 Solder seal 41, 42 Intermediate layer 45 Terminal electrode 47 Solder ball 50 Sacrificial layer 51 Through hole 52 Metal layer 61 Acoustic wave device 81 Acoustic wave device 82 Support substrate 83 Piezoelectric layer 84 IDT electrode 84a First busbar electrode 84b Second busbar electrode 84c First electrode (first electrode finger)
84d Second electrode (second electrode finger)
85, 86reflector 90 acoustic wave device 91 support substrate 92 piezoelectric layer 92a first main surface of piezoelectric layer 92b second main surface of piezoelectric layer 93 cavity 94 upper electrode 95 lower electrode 201 piezoelectric film 201a first main surface of piezoelectric film 1 principal surface 201b second principal surface of piezoelectric film 451 first region 452 second region C excitation region VP1 virtual plane
2 圧電層
2a 圧電層の第1の主面
2b 圧電層の第2の主面
3 第1電極
4 第2電極
5 第1のバスバー電極
6 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 空洞部
10、10A、10B、10C、10D、10E、10F、10G 弾性波装置
20 支持部材
21 圧電層
21M メンブレン部
22 機能電極
23 空洞部
24 バスバー電極及び配線電極
24A 1層電極
25 2層配線
25A 2層電極
30 圧電基板
31 第1基板
32 第2基板
33 第3基板
35 金属シール
37 はんだシール
41、42 中間層
45 端子電極
47 はんだボール
50 犠牲層
51 貫通孔
52 金属層
61 弾性波装置
81 弾性波装置
82 支持基板
83 圧電層
84 IDT電極
84a 第1のバスバー電極
84b 第2のバスバー電極
84c 第1電極(第1電極指)
84d 第2電極(第2電極指)
85、86 反射器
90 弾性波装置
91 支持基板
92 圧電層
92a 圧電層の第1の主面
92b 圧電層の第2の主面
93 空洞部
94 上部電極
95 下部電極
201 圧電膜
201a 圧電膜の第1の主面
201b 圧電膜の第2の主面
451 第1領域
452 第2領域
C 励振領域
VP1 仮想平面 1
84d Second electrode (second electrode finger)
85, 86
Claims (20)
- 空洞部を一方主面に有する支持部材と、
前記空洞部を覆うように前記支持部材の前記一方主面に設けられた圧電層と、
前記圧電層の少なくとも一方の主面に、前記圧電層の厚み方向から見て少なくとも一部が前記空洞部と重なるように設けられた機能電極と、
を備え、
前記支持部材は、第1基板と、前記第1基板と前記圧電層との間に設けられた中間層と、を含み、
前記支持部材は、前記圧電層と同種の材料を含有する、
弾性波装置。 a support member having a hollow portion on one main surface;
a piezoelectric layer provided on the one main surface of the support member so as to cover the cavity;
a functional electrode provided on at least one main surface of the piezoelectric layer so that at least a portion thereof overlaps with the cavity when viewed from the thickness direction of the piezoelectric layer;
Equipped with
The support member includes a first substrate and an intermediate layer provided between the first substrate and the piezoelectric layer,
The support member contains the same kind of material as the piezoelectric layer,
Elastic wave device. - 前記第1基板は、前記圧電層と同種の材料からなる、
請求項1に記載の弾性波装置。 The first substrate is made of the same material as the piezoelectric layer,
The elastic wave device according to claim 1. - 前記圧電層がニオブ酸リチウムからなり、
前記圧電層の回転Yカット角が90度以上163度以下の範囲である、
請求項1又は2に記載の弾性波装置。 the piezoelectric layer is made of lithium niobate,
The rotational Y cut angle of the piezoelectric layer is in the range of 90 degrees or more and 163 degrees or less,
The elastic wave device according to claim 1 or 2. - 前記支持部材は、前記第1基板を挟んで前記中間層とは反対側に、Siからなる第2基板をさらに含む、
請求項1~3のいずれか1項に記載の弾性波装置。 The support member further includes a second substrate made of Si on the opposite side of the intermediate layer with the first substrate in between.
The elastic wave device according to any one of claims 1 to 3. - 前記空洞部とは反対側の前記圧電層の主面と対向するように前記圧電層と間隔を空けて設けられ、Si又は金属からなる第3基板をさらに備え、
前記第2基板と前記第3基板とが金属接合によって気密封止されている、
請求項4に記載の弾性波装置。 further comprising a third substrate made of Si or metal and provided at a distance from the piezoelectric layer so as to face the main surface of the piezoelectric layer on the opposite side to the cavity,
the second substrate and the third substrate are hermetically sealed by metal bonding;
The elastic wave device according to claim 4. - 前記機能電極と電気的に接続されている端子電極をさらに備え、
前記端子電極は、前記第1基板とは反対側の前記第2基板の表面に露出している、
請求項5に記載の弾性波装置。 further comprising a terminal electrode electrically connected to the functional electrode,
the terminal electrode is exposed on a surface of the second substrate opposite to the first substrate;
The elastic wave device according to claim 5. - 前記機能電極と電気的に接続されている端子電極をさらに備え、
前記端子電極は、前記圧電層とは反対側の前記第3基板の表面に露出している、
請求項5に記載の弾性波装置。 further comprising a terminal electrode electrically connected to the functional electrode,
the terminal electrode is exposed on a surface of the third substrate opposite to the piezoelectric layer;
The elastic wave device according to claim 5. - 前記金属接合は、Au-Au接合又ははんだ接合である、
請求項5~7のいずれか1項に記載の弾性波装置。 The metal bond is an Au-Au bond or a solder bond,
The elastic wave device according to any one of claims 5 to 7. - 前記第3基板は、Siからなる、
請求項5~8のいずれか1項に記載の弾性波装置。 The third substrate is made of Si,
The elastic wave device according to any one of claims 5 to 8. - 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からなる、
請求項1~9のいずれか1項に記載の弾性波装置。 The piezoelectric layer is made of lithium niobate or lithium tantalate,
The elastic wave device according to any one of claims 1 to 9. - 前記機能電極は、1以上の第1電極と、前記1以上の第1電極が接続された第1のバスバー電極と、1以上の第2電極と、前記1以上の第2電極が接続された第2のバスバー電極と、を有する、
請求項1~10のいずれか1項に記載の弾性波装置。 The functional electrode includes one or more first electrodes, a first busbar electrode to which the one or more first electrodes are connected, one or more second electrodes, and the one or more second electrodes to which the functional electrode is connected. a second busbar electrode;
The elastic wave device according to any one of claims 1 to 10. - 前記圧電層の厚みは、前記1以上の第1電極と前記1以上の第2電極のうち、隣り合う第1電極と第2電極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11に記載の弾性波装置。 The thickness of the piezoelectric layer is 2p or less, where p is the center-to-center distance between adjacent first electrodes and second electrodes among the one or more first electrodes and the one or more second electrodes. be,
The elastic wave device according to claim 11. - 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11に記載の弾性波装置。 It is configured to be able to utilize bulk waves in thickness-slip mode.
The elastic wave device according to claim 11. - 前記圧電層の厚みをd、前記1以上の第1電極と前記1以上の第2電極のうち、隣り合う第1電極と第2電極との間の中心間距離をpとした場合、d/p≦0.5である、
請求項11に記載の弾性波装置。 If the thickness of the piezoelectric layer is d, and the center-to-center distance between adjacent first and second electrodes among the one or more first electrodes and the one or more second electrodes is p, then d/ p≦0.5,
The elastic wave device according to claim 11. - d/p≦0.24である、
請求項14に記載の弾性波装置。 d/p≦0.24,
The elastic wave device according to claim 14. - 前記1以上の第1電極と前記1以上の第2電極のうち、隣り合う第1電極と第2電極とが対向している方向に視たときに重なっている励振領域の面積に対する、前記隣り合う第1電極と第2電極との面積の割合であるメタライゼーション比をMR、前記圧電層の厚みをd、前記隣り合う第1電極と第2電極との中心間距離をpとした場合、MR≦1.75(d/p)+0.075である、
請求項11、12、14又は15に記載の弾性波装置。 Of the one or more first electrodes and the one or more second electrodes, the area of the excitation region that overlaps when viewed in the direction in which adjacent first electrodes and second electrodes face each other, When the metallization ratio, which is the area ratio of the first electrode and the second electrode that match, is MR, the thickness of the piezoelectric layer is d, and the distance between the centers of the adjacent first and second electrodes is p, MR≦1.75(d/p)+0.075,
The elastic wave device according to claim 11, 12, 14 or 15. - MR≦1.75(d/p)+0.05である、
請求項16に記載の弾性波装置。 MR≦1.75(d/p)+0.05,
The elastic wave device according to claim 16. - 前記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、
請求項11に記載の弾性波装置。
(0°±10°,0°~20°,任意のψ) …式(1)
(0°±10°,20°~80°,0°~60°(1-(θ-50)2/900)1/2) または (0°±10°,20°~80°,[180°-60°(1-(θ-50)2/900)1/2]~180°) …式(2)
(0°±10°,[180°-30°(1-(ψ-90)2/8100)1/2]~180°,任意のψ) …式(3) The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate are in the range of the following formula (1), formula (2) or formula (3),
The elastic wave device according to claim 11.
(0°±10°, 0° to 20°, arbitrary ψ) ...Formula (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°) ...Formula (2)
(0°±10°, [180°-30° (1-(ψ-90) 2 /8100) 1/2 ] ~ 180°, arbitrary ψ) ...Formula (3) - 板波を利用可能に構成されている、
請求項1~11のいずれか1項に記載の弾性波装置。 Configured to utilize plate waves,
The elastic wave device according to any one of claims 1 to 11. - 前記圧電層が、前記一方主面と対向し合う他方主面を有し、
前記機能電極が、前記圧電層の前記一方主面に設けられている上部電極と、前記他方主面に設けられている下部電極を有し、
前記上部電極及び前記下部電極が対向し合っている、請求項1~10のいずれか1項に記載の弾性波装置。 The piezoelectric layer has a second main surface facing the one main surface,
The functional electrode has an upper electrode provided on the one main surface of the piezoelectric layer and a lower electrode provided on the other main surface,
The acoustic wave device according to claim 1, wherein the upper electrode and the lower electrode face each other.
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