Elastic wave device

Abstract

Provided is an elastic wave device that suppresses degradation of a resonance characteristic. The elastic wave device includes a piezoelectric layer and a plurality of electrodes including at least one pair of electrodes that face each other in a second direction intersecting a first direction and are arranged adjacent to each other on a first main surface. In the second direction, at least three or more of the plurality of electrodes are arranged. Further, the plurality of electrodes include at least two electrodes having different film thicknesses. The plurality of electrodes include at least two electrodes having the same film thickness and arranged adjacent to each other. Alternatively, in the second direction, at least three or more of the plurality of electrodes are arranged, and the plurality of electrodes include at least three electrodes having different film thicknesses.

Description

Technical Field

[0001] This disclosure relates to an elastic wave device having a piezoelectric layer comprising lithium niobate or lithium tantalate. Background Technology

[0002] Patent document 1 describes an elastic wave device.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-257019 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In elastic wave devices, the resonant characteristics of the device may be easily degraded due to stray noise.

[0008] This disclosure was made in view of the above circumstances, and its object is to provide an elastic wave device that suppresses the deterioration of resonance characteristics.

[0009] means for solving problems

[0010] An elastic wave device comprises: a piezoelectric layer having a first main surface and a second main surface, the second main surface being located on the opposite side of the first main surface and in a first direction relative to the first main surface; and a plurality of electrodes, including at least a pair of electrodes facing each other in a second direction intersecting the first direction and disposed adjacently on the first main surface, wherein at least three or more of the plurality of electrodes are arranged in the second direction, the plurality of electrodes including at least two electrodes with different film thicknesses, and the plurality of electrodes including at least two electrodes with the same film thickness and adjacent to each other.

[0011] Another type of elastic wave device includes: a piezoelectric layer having a first main surface and a second main surface, the second main surface being located on the opposite side of the first main surface and in a first direction relative to the first main surface; and a plurality of electrodes including at least a pair of electrodes facing each other in a second direction intersecting the first direction and disposed adjacently on the first main surface, wherein at least three of the plurality of electrodes are arranged in the second direction, the plurality of electrodes including at least three electrodes with different film thicknesses.

[0012] Invention Effects

[0013] According to this disclosure, it is possible to suppress the deterioration of resonance characteristics. Attached Figure Description

[0014] Figure 1A This is a perspective view showing the elastic wave device according to the first embodiment.

[0015] Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0016] Figure 2 It is along Figure 1A A partial sectional view of line II-II.

[0017] Figure 3A This is a schematic cross-sectional view used to illustrate the Lamb wave propagating in the piezoelectric layer of the comparative example.

[0018] Figure 3B This is a schematic cross-sectional view used to illustrate the first-order thickness shear mode of a bulk wave propagating in the piezoelectric layer of the first embodiment.

[0019] Figure 4 It is a schematic cross-sectional view used to illustrate the amplitude direction of a bulk wave in the thickness shear first-order mode propagating in the piezoelectric layer of the first embodiment.

[0020] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0021] Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the fractional bandwidth of the resonator in the elastic wave device of the first embodiment, where p is the average distance between the centers of adjacent electrodes and d is the average thickness of the piezoelectric layer.

[0022] Figure 7 This is a top view showing an example of an elastic wave device in the first embodiment having a pair of electrodes.

[0023] Figure 8 This is a variation of the first embodiment, and is along... Figure 1A A partial sectional view of line II-II.

[0024] Figure 9 In the first embodiment, along Figure 1B A partial sectional view of the IX-IX line.

[0025] Figure 10A This is an explanatory diagram illustrating the relationship between spurious emissions and frequency in the first embodiment.

[0026] Figure 10B This is an explanatory diagram used to illustrate the relationship between spurious emissions and frequencies in the comparative example.

[0027] Figure 11 In the second embodiment, along Figure 1BA partial sectional view of the IX-IX line.

[0028] Figure 12 In the third embodiment, along Figure 1B A partial sectional view of the IX-IX line.

[0029] Figure 13 In the fourth embodiment, along Figure 1B A partial sectional view of the IX-IX line.

[0030] Figure 14 In the fifth embodiment, along Figure 1B A partial sectional view of the IX-IX line.

[0031] Figure 15 In the sixth embodiment along Figure 1B A partial sectional view of the IX-IX line. Detailed Implementation

[0032] The embodiments of this disclosure will now be described in detail based on the accompanying drawings. It should be noted that this disclosure is not limited by these embodiments. Furthermore, the embodiments described in this disclosure are illustrative, and partial structural substitutions or combinations are possible between different embodiments. In modified examples and second embodiments, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects produced by the same structure are not mentioned repeatedly in each embodiment.

[0033] (First Implementation)

[0034] Figure 1A This is a perspective view showing the elastic wave device according to the first embodiment. Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0035] The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. The cutting angle of LiNbO3 or LiTaO3 in the first embodiment is Z-cut. The cutting angle of LiNbO3 or LiTaO3 may also be rotational Y-cut or X-cut. Preferably, the propagation orientation is ±30° of Y propagation and X propagation.

[0036] The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the first-order mode of thickness shearing, it is preferably 50 nm or more and 1000 nm or less.

[0037] The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b opposite to each other in the Z direction. An electrode 3 and an electrode 4 are disposed on the first main surface 2a.

[0038] Here, electrode 3 is an example of a "first electrode," and electrode 4 is an example of a "second electrode." Figure 1A and Figure 1B In this configuration, multiple electrodes 3 are connected to the first busbar 5. Multiple electrodes 4 are connected to the second busbar 6. The multiple electrodes 3 and multiple electrodes 4 are inserted alternately into each other.

[0039] Electrodes 3 and 4 are rectangular in shape and have a length direction. Electrode 3 is positioned opposite its adjacent electrode 4 in a direction orthogonal to this length direction. The length directions of electrodes 3 and 4, as well as the directions orthogonal to their length directions, intersect the thickness direction of the piezoelectric layer 2. Therefore, electrode 3 and its adjacent electrode 4 can also be described as being opposite each other in a direction intersecting the thickness direction of the piezoelectric layer 2. In the following description, the thickness direction of the piezoelectric layer 2 may sometimes be defined as the Z direction (or a first direction), the direction orthogonal to the length directions of electrodes 3 and 4 as the X direction (or a second direction), and the length directions of electrodes 3 and 4 as the Y direction (or a third direction).

[0040] In addition, the length directions of electrodes 3 and 4 can also be aligned with... Figure 1A and Figure 1B The directions shown are interchanged, being orthogonal to the length directions of electrodes 3 and 4. That is, in Figure 1A and Figure 1B Alternatively, electrodes 3 and 4 can extend along the directions in which the first busbar 5 and the second busbar 6 extend. In this case, the first busbar 5 and the second busbar 6... Figure 1A and Figure 1B The electrode extends along the direction in which electrodes 3 and 4 extend. Furthermore, multiple pairs of structures are provided in a direction orthogonal to the length direction of electrodes 3 and 4, where an electrode 3 connected to one potential is adjacent to an electrode 4 connected to another potential.

[0041] Here, "electrode 3 and electrode 4 are adjacent" does not mean that electrode 3 and electrode 4 are configured in direct contact, but rather that electrode 3 and electrode 4 are configured with a gap between them. Furthermore, when electrode 3 and electrode 4 are adjacent, no other electrodes (including those connected to the signal electrode and ground electrode) are configured between electrode 3 and electrode 4. The number of pairs does not need to be an integer; it can be 1.5 pairs, 2.5 pairs, etc.

[0042] The center-to-center distance, i.e., the spacing, between electrodes 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the center-to-center distance between electrodes 3 and 4 is the distance obtained by connecting the center of the width dimension of electrode 3 in a direction orthogonal to the length direction of electrode 3 and the center of the width dimension of electrode 4 in a direction orthogonal to the length direction of electrode 4.

[0043] Furthermore, when at least one of electrodes 3 and 4 has multiple electrodes (when electrodes 3 and 4 are set as a pair of electrode groups, there are 1.5 or more pairs of electrode groups), the center-to-center distance of electrodes 3 and 4 refers to the average value of the center-to-center distances of adjacent electrodes 3 and 4 in 1.5 or more pairs of electrodes 3 and 4.

[0044] Furthermore, the widths of electrodes 3 and 4, i.e., the dimensions of electrodes 3 and 4 in their opposing directions, are preferably in the range of 150 nm or more and 1000 nm or less. It should be noted that the center-to-center distance between electrodes 3 and 4 is the distance obtained by connecting the center of the dimension (width) of electrode 3 in a direction orthogonal to the length direction of electrode 3 and the center of the dimension (width) of electrode 4 in a direction orthogonal to the length direction of electrode 4.

[0045] Furthermore, in the first embodiment, a Z-cut piezoelectric layer is used; therefore, the direction orthogonal to the length directions of electrodes 3 and 4 becomes the direction orthogonal to the polarization direction of piezoelectric layer 2. This is not limited to cases where a piezoelectric material with a different cut angle is used as piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal; it can also be approximately orthogonal (the angle between the direction orthogonal to the length directions of electrodes 3 and 4 and the polarization direction is, for example, 90° ± 10°).

[0046] On the second main surface 2b side of the piezoelectric layer 2, a support member 8 is stacked with an intermediate layer 7 in between. The intermediate layer 7 and the support member 8 have a frame-like shape, such as... Figure 2 As shown, it has openings 7a and 8a. As a result, a cavity (air gap) 9 is formed.

[0047] The void 9 is provided so as not to interfere with the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support member 8 is stacked on the second main surface 2b with an intermediate layer 7 in a position that does not overlap with the portion where at least one pair of electrodes 3 and 4 are provided. It should be noted that the intermediate layer 7 may also be omitted. Therefore, the support member 8 can be stacked directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

[0048] The intermediate layer 7 is an insulating layer formed of silicon oxide. However, in addition to silicon oxide, the intermediate layer 7 can also be formed of suitable insulating materials such as silicon oxynitride or bauxite.

[0049] The support member 8, also known as the support substrate, is formed of Si. The orientation of the surface on the piezoelectric layer 2 side of Si can be (100), (110), or (111). Preferably, it is Si with a high resistivity of 4 kΩ or higher. However, suitable insulating materials and semiconductor materials can also be used to construct the support member 8. For example, materials such as piezoelectric materials such as alumina, lithium tantalate, lithium niobate, and quartz, bauxite, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and forsterite, as well as various ceramics, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used as materials for the support member 8.

[0050] The aforementioned electrodes 3 and 4, as well as the first busbar 5 and the second busbar 6, comprise suitable metals or alloys such as Al and AlCu alloys. In the first embodiment, the electrodes 3 and 4, and the first busbar 5 and the second busbar 6 have a structure in which an Al film is laminated on a Ti film. It should be noted that a bonding layer other than a Ti film may also be used.

[0051] During driving, an alternating voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an alternating voltage is applied between the first busbar 5 and the second busbar 6. As a result, the resonant characteristics of a bulk wave utilizing the thickness shear first-order mode excited in the piezoelectric layer 2 can be obtained.

[0052] Furthermore, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any two adjacent pairs of electrodes 3 and 4 is set to p, d / p is 0.5 or less. Therefore, the bulk wave of the aforementioned thickness shear first-order 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.

[0053] It should be noted that when at least one of the electrodes 3 and 4 has multiple electrodes as in the first embodiment, that is, when the electrodes 3 and 4 are set as a pair of electrode groups and there are 1.5 or more pairs of electrodes 3 and 4, the center-to-center distance p of adjacent electrodes 3 and 4 becomes the average distance between the centers of each adjacent electrode 3 and 4.

[0054] In the elastic wave device 1 of the first embodiment, due to the above-described structure, even if the number of pairs of electrodes 3 and 4 is reduced to achieve miniaturization, it is difficult to cause a decrease in the Q value. This is because it is a resonator that does not require reflectors on both sides, resulting in low propagation loss. Furthermore, the reason why the aforementioned reflectors are not required is because a first-order thickness shear mode body wave is utilized.

[0055] Figure 3AThis is a schematic cross-sectional view used to illustrate the Lamb wave propagating in the piezoelectric layer of the comparative example. Figure 3B This is a schematic cross-sectional view used to illustrate the first-order thickness shear mode of a bulk wave propagating in the piezoelectric layer of the first embodiment. Figure 4 It is a schematic cross-sectional view used to illustrate the amplitude direction of a bulk wave in the thickness shear first-order mode propagating in the piezoelectric layer of the first embodiment.

[0056] exist Figure 3A In this case, it is an elastic wave device as described in Patent Document 1, in which Lamb waves propagate in a piezoelectric layer. For example... Figure 3A As shown, the wave propagates in the piezoelectric layer 201 as indicated by the arrow. Here, the piezoelectric layer 201 has a first main surface 201a and a second main surface 201b, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z-direction. The X-direction is the direction in which the electrode fingers of the IDT electrodes are arranged. Figure 3A As shown, for a Lamb wave, the wave propagates along the X direction as illustrated. Since it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates along the X direction, thus resonant characteristics are obtained by placing reflectors on both sides. Therefore, wave propagation loss occurs, and the Q value decreases when miniaturization is achieved, i.e., when the number of electrode finger pairs is reduced.

[0057] In contrast, such as Figure 3B As shown, in the elastic wave device of the first embodiment, the vibration displacement is in the thickness shear direction. Therefore, the wave propagates approximately along the Z direction, which is the direction connecting the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2, and generates resonance. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained through the propagation of the wave in this Z-direction, a reflector is not required. Therefore, no propagation loss occurs when propagating in a reflector. Therefore, even if the number of electrode pairs, including electrodes 3 and 4, is reduced to promote miniaturization, it is difficult to cause a decrease in the Q value.

[0058] It should be noted that, as Figure 4 As shown, the amplitude direction of the bulk wave in the first-order thickness shear mode is in the excitation region C of the piezoelectric layer 2 (reference). Figure 1B The first region 451 contained in the excitation region C is the opposite of the second region 452 contained in the excitation region C. Figure 4 The diagram schematically illustrates a body wave when a voltage higher than the potential of electrode 3 is applied between electrodes 3 and 4. The first region 451 is the region in excitation region C between a virtual plane VP1, orthogonal to the thickness direction of piezoelectric layer 2 and dividing piezoelectric layer 2 in two, and the first main surface 2a. The second region 452 is the region in excitation region C between the virtual plane VP1 and the second main surface 2b.

[0059] In the elastic wave device 1, at least one pair of electrodes, including electrode 3 and electrode 4, is provided, but the wave is not propagated in the X direction. Therefore, the number of electrode pairs including electrode 3 and electrode 4 does not necessarily have to be multiple pairs. That is, it is sufficient to provide at least one pair of electrodes.

[0060] For example, electrode 3 is an electrode connected to the signal potential, and electrode 4 is an electrode connected to the ground potential. Alternatively, electrode 3 can be connected to the ground potential, and electrode 4 can be connected to the signal potential. In the first embodiment, as described above, at least one pair of electrodes is connected to both the signal potential and the ground potential, and no floating electrode is provided.

[0061] Figure 5 This is an explanatory diagram illustrating an example of the resonant characteristics of the elastic wave device according to the first embodiment. It should be noted that... Figure 5 The design parameters of the elastic wave device 1 with the resonant characteristics shown are as follows.

[0062] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°)

[0063] Thickness of piezoelectric layer 2: 400nm.

[0064] Excitation region C (reference) Figure 1B Length: 40μm

[0065] The number of electrode pairs, including electrodes 3 and 4, is 21.

[0066] Center-to-center distance (split) between electrodes 3 and 4: 3 μm

[0067] Width of electrodes 3 and 4: 500 nm

[0068] d / p: 0.133

[0069] Intermediate layer 7: Silicon oxide film with a thickness of 1 μm.

[0070] Supporting component 8: Si.

[0071] It should be noted that the excitation region C (refer to...) Figure 1B The region C is the area where electrodes 3 and 4 overlap when viewed along the X direction, which is orthogonal to the length directions of electrodes 3 and 4. The length of the excitation region C refers to its dimension along the length directions of electrodes 3 and 4.

[0072] In the first embodiment, the distance between the electrodes of the electrode pairs including electrodes 3 and 4 is equal in all pairs. That is, electrodes 3 and 4 are arranged at equal intervals.

[0073] according to Figure 5It can be seen that, despite not having a reflector, a good resonant characteristic with a fractional bandwidth of 12.5% ​​was obtained.

[0074] However, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between the electrodes of electrode 3 and electrode 4 is set to p, in the first embodiment, d / p is 0.5 or less, more preferably 0.24 or less. (Refer to...) Figure 6 This needs to be explained.

[0075] With Get Figure 5 Similarly, by varying d / 2p, multiple elastic wave devices can be obtained, just as shown in the example of the elastic wave device with resonant characteristics. Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the fractional bandwidth of the resonator in the elastic wave device of the first embodiment, where p is the average distance between the centers of adjacent electrodes and d is the average thickness of the piezoelectric layer.

[0076] like Figure 6 As shown, when d / 2p exceeds 0.25, i.e., when d / p > 0.5, even with adjustments to d / p, the fractional bandwidth is less than 5%. Conversely, when d / 2p ≤ 0.25, i.e., d / p ≤ 0.5, varying d / p within this range allows for a fractional bandwidth of 5% or more, enabling the construction of a resonator with a high coupling coefficient. Furthermore, when d / 2p is below 0.12, i.e., below 0.24, the fractional bandwidth can be increased to 7% or more. Moreover, adjusting d / p within this range yields a resonator with an even wider fractional bandwidth, achieving a resonator with a higher coupling coefficient. Therefore, it can be concluded that by setting d / p to 0.5 or less, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear first-order mode of the bulk wave can be constructed.

[0077] It should be noted that at least one pair of electrodes can also be a pair. In the case of a pair of electrodes, p refers to the center-to-center distance between adjacent electrodes 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, the average center-to-center distance between adjacent electrodes 3 and 4 can be set as p.

[0078] In addition, regarding the thickness d of the piezoelectric layer, the value obtained by averaging the thickness can be used when the piezoelectric layer 2 has a thickness deviation.

[0079] Figure 7 This is a top view showing an example of an elastic wave device according to the first embodiment, in which a pair of electrodes are provided. In the elastic wave device 31, a pair of electrodes having electrodes 3 and 4 are provided on the first main surface 2a of the piezoelectric layer 2. It should be noted that... Figure 7K in the figure represents the cross width. As described above, in the elastic wave device of this disclosure, the number of electrode pairs can also be one. In this case, if the above d / p is less than or equal to 0.5, it is also possible to effectively excite a first-order thickness shear mode of a bulk wave.

[0080] Figure 8 This is a variation of the first embodiment, and is along... Figure 1A A partial cross-sectional view along line II-II. In the elastic wave device 41, an acoustic multilayer film 42 is stacked on the second main surface 2b of the piezoelectric layer 2. The acoustic multilayer film 42 has a stacked structure of low acoustic impedance layers 42a, 42c, and 42e with relatively low acoustic impedance and high acoustic impedance layers 42b and 42d with relatively high acoustic impedance. When the acoustic multilayer film 42 is used, even without using the void portion 9 in the elastic wave device 1, the bulk wave of the thickness shear first-order mode can be contained within the piezoelectric layer 2. In the elastic wave device 41, by setting the above-mentioned d / p to 0.5 or less, the resonance characteristics of the bulk wave based on the thickness shear first-order mode can also be obtained. It should be noted that the number of stacked low acoustic impedance layers 42a, 42c, and 42e and high acoustic impedance layers 42b and 42d in the acoustic multilayer film 42 is not particularly limited. At least one high acoustic impedance layer 42b, 42d is disposed on the side away from the piezoelectric layer 2 compared to the low acoustic impedance layers 42a, 42c, 42e.

[0081] The aforementioned low acoustic impedance layers 42a, 42c, and 42e, and high acoustic impedance layers 42b and 42d, can be made of suitable materials as long as they satisfy the aforementioned acoustic impedance relationship. For example, silicon oxide or silicon oxynitride can be used as materials for the low acoustic impedance layers 42a, 42c, and 42e. Furthermore, alumina, silicon nitride, or metals can be used as materials for the high acoustic impedance layers 42b and 42d.

[0082] As explained above, in elastic wave devices 1, 31, and 41, a first-order thickness shear mode volume wave is utilized. Furthermore, in elastic wave devices 1, 31, and 41, the first electrode 3 and the second electrode 4 are adjacent electrodes, and when the thickness of the piezoelectric layer is set to d and the center-to-center distance between the first and second electrodes is set to p, d / p is 0.5 or less. Therefore, even with miniaturization of the elastic wave device, the Q value can be improved.

[0083] In the elastic wave devices 1, 31, and 41, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. Preferably, a first electrode 3 and a second electrode 4 are provided on the first main surface 2a or the second main surface 2b of the piezoelectric layer 2, and a protective film is used to cover the first electrode 3 and the second electrode 4.

[0084] Figure 9 In the first embodiment, along Figure 1BA partial cross-sectional view of line IX-IX. For ease of understanding, the thickness difference is magnified compared to the actual film thickness difference. Figure 9 The film thicknesses of electrodes 3 and 4 are shown. In the first embodiment, as... Figure 9 As shown, Figure 2 The film thickness of electrodes 3 and 4 shown is any one of film thicknesses ft1, ft2, ft3, ft4, and ft5. In the following description, electrodes 3 and 4 will be described as electrode 50 without distinction. The difference between film thickness ft1 and film thickness ft2 is, for example, 10 nm. The difference between film thickness ft2 and film thickness ft3 is, for example, 10 nm. The difference between film thickness ft3 and film thickness ft4 is, for example, 10 nm. The difference between film thickness ft4 and film thickness ft5 is, for example, 10 nm. When film thickness ft1 is 580 nm, film thickness ft2 is 590 nm, film thickness ft3 is 600 nm, film thickness ft4 is 610 nm, and film thickness ft5 is 620 nm.

[0085] The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft1 is seven. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft2 is seven. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft3 is seven. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft4 is seven. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft5 is seven. Thus, the number of electrodes 50 with different film thicknesses than each other, sandwiched between each other by the same electrode 50, arranged in the X direction is fixed. It should be noted that among the electrodes 50 with the same film thickness, there are also cases where the film thickness of one electrode 50 is within ±5% of the film thickness of another electrode 50.

[0086] Electrodes 50 are arranged along the X direction in sequence, with film thicknesses ft1, ft2, ft3, ft4, ft5, ft4, ft3, ft2, and ft1 forming a combination of film thicknesses. This combination of film thicknesses is repeated in the X direction. Thus, the arrangement of electrodes 50 in the X direction exhibits regularity within the combination of film thicknesses. For example, electrodes 50 of film thickness ft1 are periodically arranged in the X direction at a ratio of one in every eight.

[0087] Figure 10A This is an explanatory diagram illustrating the relationship between spurious emissions and frequency in the first embodiment. The simulation conditions for Example 1BL of the first embodiment are described below. Figure 10A The evaluation results are shown.

[0088] The center-to-center distance (split) between electrode 3 and electrode 4: 4.2 μm

[0089] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 127.5°, 0°)

[0090] Piezoelectric layer thickness: 0.5µm

[0091] Materials of electrodes 3 and 4: Al

[0092] The center-to-center distance (split) between electrode 3 and electrode 4: 3.14 μm

[0093] The line widths of electrodes 3 and 4 are 1.26 μm.

[0094] The gap width between the first busbar and electrode 4 and the gap width between the second busbar and electrode 3 are both 1.90 μm.

[0095] Number of electrode pairs: 20 pairs (41 electrodes)

[0096] Film thicknesses of electrodes 3 and 4: With film thickness ft1 at 580 nm, film thickness ft2 is 590 nm, film thickness ft3 is 600 nm, film thickness ft4 is 610 nm, and film thickness ft5 is 620 nm. According to... Figure 9 The combination of film thicknesses shown includes electrodes 3 and 4.

[0097] Figure 10B This is an explanatory diagram used to illustrate the relationship between spurious emissions and frequencies in the comparative example.

[0098] The simulation conditions for the comparative example RL are as follows: Figure 10B The evaluation results are shown.

[0099] The center-to-center distance (split) between electrode 3 and electrode 4: 4.2 μm

[0100] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 127.5°, 0°)

[0101] Piezoelectric layer thickness: 0.5µm

[0102] Materials of electrodes 3 and 4: A1

[0103] The center-to-center distance (split) between electrode 3 and electrode 4: 3.14 μm

[0104] The line widths of electrodes 3 and 4 are 1.26 μm.

[0105] The gap width between the first busbar and electrode 4 and the gap width between the second busbar and electrode 3 are both 1.90 μm.

[0106] Number of electrode pairs: 20 pairs (41 electrodes)

[0107] The total film thickness of electrodes 3 and 4 is 600 nm.

[0108] exist Figure 10A and Figure 10B The diagram shows the resonant characteristics when the horizontal axis represents frequency and the vertical axis represents phase. When... Figure 10A China confirms and Figure 10B When the spurious frequencies of the comparative example RL appear in the text are the same, it can be seen that the intensity of the spurious frequencies at the positions indicated by the arrows is suppressed.

[0109] (Second Implementation)

[0110] Figure 11 In the second embodiment, along Figure 1B A partial cross-sectional view of line IX-IX. For ease of understanding, the thickness difference is shown magnified compared to the actual film thickness difference. Figure 11 The film thicknesses of electrodes 3 and 4 are shown. In the second embodiment, Figure 11 The film thickness of electrodes 3 and 4 shown is any one of film thicknesses ft1, ft2, ft3, and ft4.

[0111] The film thicknesses of electrodes 3 and 4 satisfy the relationship ft1 < ft2 < ft3 < ft4. The difference in film thickness between ft1 and ft2 is smaller than the difference in film thickness between ft2 and ft3. In the second embodiment, the film thickness differences between adjacent electrodes 3 and 4 are different. Furthermore, the film thicknesses of the three electrodes 3 and 4 arranged in the X direction are different.

[0112] The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft1 is four. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft2 is four. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft3 is one or four. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft4 is four. Thus, the number of electrodes 50 sandwiched between each other by the same electrode 50 in the X direction, with film thicknesses different from those of each electrode 50, follows a regular pattern. It should be noted that among the electrodes 50 with the same film thickness, there are also cases where the film thickness of one electrode 50 is within ±5% of the film thickness of another electrode 50.

[0113] Electrodes 50 are arranged in the X direction in sequence, with film thicknesses ft1, ft2, ft3, ft4, ft3, and ft1 forming a combination of film thicknesses. This combination of film thicknesses is repeated in the X direction. Thus, the arrangement of electrodes 50 in the X direction exhibits regularity within the combination of film thicknesses. For example, electrodes 50 of film thickness ft1 are periodically arranged in the X direction at a ratio of one in every five.

[0114] (Third Implementation)

[0115] Figure 12 In the third embodiment, along Figure 1B A partial cross-sectional view of line IX-IX. For ease of understanding, the thickness difference is shown magnified compared to the actual film thickness difference. Figure 12 The film thicknesses of electrodes 3 and 4 are shown. In the third embodiment, Figure 12 The film thickness of electrodes 3 and 4 shown is any one of film thicknesses ft1, ft2, and ft3.

[0116] The film thicknesses of electrodes 3 and 4 satisfy the relationship ft1 < ft2 < ft3. The film thickness difference between film thickness ft1 and film thickness ft2 is the same as the film thickness difference between film thickness ft2 and film thickness ft3. In the third embodiment, the film thickness difference between adjacent electrodes 3 and 4 is the same. Furthermore, the film thicknesses of the three electrodes 3 and 4 arranged in the X direction are different.

[0117] The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft1 is three. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft2 is three. The number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness ft3 is three. Thus, the number of electrodes 50 sandwiched between each other by the same electrode 50 in the X direction, whose film thickness is different from that of each electrode 50, is fixed. It should be noted that the electrodes 50 with the same film thickness also include the case where the film thickness of one electrode 50 is within ±5% of the film thickness of another electrode 50.

[0118] Electrodes 50 are arranged in the X direction in sequence, with film thicknesses ft1, ft2, ft3, ft2, and ft1 forming a combination of film thicknesses. This combination of film thicknesses is repeated in the X direction. Thus, the arrangement of electrodes 50 in the X direction exhibits regularity in the combination of film thicknesses. For example, electrodes 50 of film thickness ft1 are periodically arranged in the X direction at a ratio of one in every four.

[0119] (Fourth Implementation)

[0120] Figure 13 In the fourth embodiment, along Figure 1B A partial cross-sectional view of line IX-IX. For ease of understanding, the thickness difference is shown magnified compared to the actual film thickness difference. Figure 13 The film thicknesses of electrodes 3 and 4 are shown. In the fourth embodiment, Figure 13 The film thickness of electrodes 3 and 4 shown is any one of film thickness ft1 and film thickness ft2.

[0121] The film thicknesses of electrodes 3 and 4 satisfy the relationship ft1 < ft2. The elastic wave device of the fourth embodiment includes at least two electrodes 50 with different film thicknesses, and has a region where adjacent electrodes 50 in the X direction have the same film thickness. It should be noted that when adjacent electrodes 3 and 4 have the same film thickness, this also includes cases where the film thickness of one electrode 3 is within ±5% of the film thickness of the other electrode 4.

[0122] Multiple electrodes 50 are arranged in the X direction as a combination of film thicknesses, namely, two electrodes 50 with the same film thickness ft2 arranged in the X direction and three electrodes 50 with the same film thickness ft1 arranged in the X direction. This combination of film thicknesses repeats in the X direction. Thus, the electrodes 50 arranged in the X direction exhibit regularity in the combination of film thicknesses.

[0123] (Fifth Implementation)

[0124] Figure 14 In the fifth embodiment, along Figure 1B A partial cross-sectional view of line IX-IX. For ease of understanding, the thickness difference is shown magnified compared to the actual film thickness difference. Figure 14 The film thicknesses of electrodes 3 and 4 are shown. In the fifth embodiment, Figure 13 The film thickness of electrodes 3 and 4 shown is any one of film thicknesses ft1, ft2, ft3, ft4, ft5, and ft6.

[0125] The film thicknesses of electrodes 3 and 4 satisfy the relationship ft1 < ft2 < ft3 < ft4 < ft5 < ft6. The difference in film thickness between ft1 and ft2 is smaller than the difference in film thickness between ft2 and ft3. In the fifth embodiment, there is a region where the film thickness difference between adjacent electrodes 3 and 4 is different.

[0126] The elastic wave device of the fifth embodiment includes at least six electrodes 50 with different film thicknesses, and has a region in which adjacent electrodes 50 in the X direction have the same film thickness ft1. It should be noted that when adjacent electrodes 3 and 4 have the same film thickness, it also includes the case where the film thickness of one electrode 3 is within ±5% of the film thickness of the other electrode 4.

[0127] The elastic wave device of the fifth embodiment includes a region in which at least three electrodes 50 with different film thicknesses are arranged in the X direction. The film thicknesses of the electrodes 50 arranged in the X direction are random. Thus, the film thicknesses of the electrodes 50 arranged in the X direction are not regular.

[0128] (Sixth Implementation Method)

[0129] Figure 15 In the sixth embodiment along Figure 1B A partial cross-sectional view of line IX-IX. For ease of understanding, the thickness difference is shown magnified compared to the actual film thickness difference. Figure 15 The film thicknesses of electrodes 3 and 4 are shown. In the sixth embodiment, Figure 15 The film thickness of electrodes 3 and 4 shown is any one of film thickness ft1 and film thickness ft2.

[0130] The film thicknesses of electrodes 3 and 4 satisfy the relationship ft1 < ft2. The elastic wave device of the sixth embodiment includes at least two electrodes 50 with different film thicknesses, and has a region where adjacent electrodes 50 in the X direction have the same film thickness. It should be noted that when adjacent electrodes 3 and 4 have the same film thickness, it also includes the case where the film thickness of one electrode 3 is within ±5% of the film thickness of the other electrode 4.

[0131] Multiple electrodes 50 are arranged in the X direction as a combination of film thicknesses, such as two electrodes 50 of the same film thickness ft1 arranged in the X direction and three electrodes 50 of the same film thickness ft1 arranged in the X direction. This combination of film thicknesses repeats in the X direction. In this way, the electrodes 50 arranged in the X direction have a regularity in the combination of film thicknesses.

[0132] The elastic wave device of the sixth embodiment includes a region in which at least two electrodes 50 with different film thicknesses are arranged in the X direction. The film thicknesses of the electrodes 50 arranged in the X direction are random. Thus, the film thicknesses of the electrodes 50 arranged in the X direction are not regular.

[0133] As described above, the elastic wave device includes: a piezoelectric layer 2 having a first main surface 2a and a second main surface 2b, the second main surface 2b being located on the opposite side of the first main surface 2a and in the Z direction relative to the first main surface 2a; and a plurality of electrodes 50 including at least one pair of electrodes 3 and 4, the at least one pair of electrodes 3 and 4 being opposed in the X direction intersecting the Z direction and disposed adjacent to each other on the first main surface 2a.

[0134] Moreover, as in the first, second, third, and fifth embodiments, at least three of the plurality of electrodes 50 are arranged in the X direction, and the plurality of electrodes 50 include at least three electrodes with different film thicknesses.

[0135] Therefore, even if the film thickness of electrode 50 is different, it is difficult to affect the resonant frequency and anti-resonant frequency. On the other hand, when the film thickness of electrode 50 is different, stray emissions are reduced, which can suppress the deterioration of resonant characteristics.

[0136] At least three electrodes 3 with different film thicknesses have the same polarity. At least three electrodes 4 with different film thicknesses have the same polarity. As a result, stray emissions are reduced, and the degradation of resonance characteristics can be suppressed.

[0137] Furthermore, as in the fourth and sixth embodiments, at least three of the plurality of electrodes 50 are arranged in the X direction, and the plurality of electrodes 50 includes at least two electrodes with different film thicknesses. Alternatively, as in the fifth embodiment, the plurality of electrodes 50 may include at least two adjacent electrodes with the same film thickness.

[0138] Therefore, even if the film thickness of electrode 50 is different, it is difficult to affect the resonant frequency and anti-resonant frequency. On the other hand, when the film thickness of electrode 50 is different, stray emissions are reduced, which can suppress the deterioration of resonant characteristics.

[0139] At least two electrodes 3 with different film thicknesses have the same polarity. At least two electrodes 4 with different film thicknesses have the same polarity. As a result, stray emissions are reduced, and the degradation of resonant characteristics can be suppressed.

[0140] In elastic wave devices 1, 31, and 41, a first-order thickness shear mode of volume wave is utilized. This enables the provision of elastic wave devices with higher coupling coefficients and better resonance characteristics.

[0141] Furthermore, when the first electrode 3 and the second electrode 4 are adjacent electrodes 50, and the thickness of the piezoelectric layer is set to d and the center-to-center distance between the first electrode and the second electrode is set to p, d / p is 0.5 or less. This allows for miniaturization of the elastic wave device and improves the Q value.

[0142] As a preferred embodiment, the film thickness of the electrodes 50 arranged in the X direction is regular. Therefore, by varying the regularity, it is easy to shift the frequency of a specific stray or to easily change the intensity of a specific stray.

[0143] As a preferred embodiment, the number of electrodes 50 with different film thicknesses that are sandwiched between each other in the X direction by electrodes 50 of the same film thickness is fixed. Thus, by varying the number of electrodes 50 sandwiched between each other in the X direction by electrodes 50 of the same film thickness, it is easy to shift the frequency of a specific stray emission or to change the intensity of a specific stray emission.

[0144] As a preferred embodiment, the film thickness of the electrodes 50 arranged in the X direction is irregular. This allows for the suppression of large stray emissions at specific frequencies.

[0145] It should be noted that the above-described embodiments are for the purpose of facilitating understanding of this disclosure and are not intended to limit the interpretation of this disclosure. This disclosure can be modified / improved without departing from its spirit, and its equivalents are also included in this disclosure.

[0146] Explanation of reference numerals in the attached figures

[0147] 1, 31, 41 Elastic wave devices;

[0148] 2. Piezoelectric layer;

[0149] 2a First main face;

[0150] 2b Second main face;

[0151] 3. Electrode (first electrode);

[0152] 4. Electrode (second electrode);

[0153] 5. First busbar;

[0154] 6. Second busbar;

[0155] 7. Intermediate layer;

[0156] 7a Opening;

[0157] 8. Supporting components;

[0158] 8a Opening;

[0159] 9. Cavity section;

[0160] 42. Acoustic multilayer membrane;

[0161] 42a Low acoustic impedance layer;

[0162] 42b High acoustic impedance layer;

[0163] 42c Low acoustic impedance layer;

[0164] 42d high acoustic impedance layer;

[0165] 42e Low acoustic impedance layer;

[0166] 50 electrodes;

[0167] 201 Piezoelectric layer;

[0168] 201a First Main Page;

[0169] 201b Second Main Page;

[0170] 451 First Region;

[0171] 452 Second Zone;

[0172] C. Incentive region;

[0173] VP1 Virtual plane;

[0174] Y rotation;

[0175] d Thickness;

[0176] ft1, ft2, ft3, ft4, ft5, ft6 film thickness;

[0177] p is the distance between centers.

Claims

1. An elastic wave device, comprising: A piezoelectric layer having a first main surface and a second main surface, the second main surface being located opposite to the first main surface and in a first direction relative to the first main surface; and A plurality of electrodes, including at least one pair of electrodes, which are opposed in a second direction intersecting the first direction and disposed adjacent to each other on the first main surface. At least three of the plurality of electrodes are arranged in the second direction. The plurality of electrodes includes at least two electrodes with different film thicknesses. The plurality of electrodes includes at least two adjacent electrodes with the same film thickness. When the average thickness of the piezoelectric layer is set as d and the center-to-center distance between adjacent electrodes is set as p, d / p is less than 0.

5.

2. The elastic wave device according to claim 1, wherein, At least two electrodes with different film thicknesses have the same polarity.

3. The elastic wave device according to claim 2, wherein, The at least three electrodes with different film thicknesses have the same polarity.

4. The elastic wave device according to claim 3, wherein, The plurality of electrodes includes at least two adjacent electrodes with the same film thickness.

5. The elastic wave device according to any one of claims 1 to 4, wherein, The piezoelectric layer includes lithium niobate or lithium tantalate. The elastic wave device utilizes a first-order thickness shear mode body wave.

6. The elastic wave device according to any one of claims 1 to 4, wherein, The piezoelectric layer includes lithium niobate or lithium tantalate.

7. The elastic wave device according to any one of claims 1 to 4, wherein, The film thickness of the electrodes arranged in the second direction is regular.

8. The elastic wave device according to any one of claims 1 to 4, wherein, The number of electrodes with different film thicknesses sandwiched between each other by electrodes of the same film thickness in the second direction is fixed.

9. The elastic wave device according to any one of claims 1 to 4, wherein, The film thickness of the electrodes arranged in the second direction is irregular.

10. An elastic wave device, comprising: A piezoelectric layer having a first main surface and a second main surface, the second main surface being located opposite to the first main surface and in a first direction relative to the first main surface; and A plurality of electrodes, including at least one pair of electrodes, which are opposed in a second direction intersecting the first direction and disposed adjacent to each other on the first main surface. At least three of the plurality of electrodes are arranged in the second direction. The plurality of electrodes includes at least three electrodes with different film thicknesses. When the average thickness of the piezoelectric layer is set as d and the center-to-center distance between adjacent electrodes is set as p, d / p is less than 0.

5.

11. The elastic wave device according to claim 10, wherein, The plurality of electrodes includes at least two adjacent electrodes with the same film thickness.

12. The elastic wave device according to claim 10 or 11, wherein, The piezoelectric layer includes lithium niobate or lithium tantalate. The elastic wave device utilizes a first-order thickness shear mode body wave.

13. The elastic wave device according to claim 10 or 11, wherein, The piezoelectric layer includes lithium niobate or lithium tantalate.

14. The elastic wave device according to claim 10 or 11, wherein, The film thickness of the electrodes arranged in the second direction is regular.

15. The elastic wave device according to claim 10 or 11, wherein, The number of electrodes with different film thicknesses sandwiched between each other by electrodes of the same film thickness in the second direction is fixed.

16. The elastic wave device according to claim 10 or 11, wherein, The film thickness of the electrodes arranged in the second direction is irregular.

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