Elastic wave device and method for manufacturing elastic wave device

Abstract

The frequency characteristics of adjacent resonators are made uniform. The elastic wave device includes a plurality of resonators. Each of the plurality of resonators includes a support member having a thickness in a first direction, a piezoelectric layer provided in the first direction of the support member, a functional electrode provided in the first direction of the piezoelectric layer, and a protective film provided in the first direction of the piezoelectric layer in which the resonators are provided. In the support member, a space portion is provided at a position at which at least a portion overlaps the functional electrode in a plan view in the first direction. The plurality of resonators includes a first resonator and a second resonator adjacent to the first resonator. The elastic modulus of the protective film at a first position is different from the elastic modulus of the protective film at a second position different from the first position. The first position overlaps the space portion of the first resonator in a plan view in the first direction. The second position overlaps the space portion of the second resonator in plan view in the first direction.

Description

Technical Field

[0001] The present disclosure relates to an elastic wave device and a method for manufacturing the elastic wave device. Background Art

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

[0003] Prior Art Literature

[0004] Patent Literature

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

[0006] Problem that the invention aims to solve

[0007] In the elastic wave device disclosed in Patent Document 1, in order to make the frequency characteristics uniform, the film thickness of the protective film is sometimes adjusted by a processing device so that it becomes a thickness corresponding to the thickness of the piezoelectric layer. In this case, in order to make the frequency characteristics uniform at adjacent positions and positions where the difference in the thickness of the piezoelectric layer is large, it is sometimes necessary to process to a degree exceeding that which the processing device can handle, and the film thickness of the protective film changes drastically. Therefore, it becomes difficult to adjust the film thickness of the protective film corresponding to the thickness of the piezoelectric layer, and it may be difficult to make the frequency characteristics of adjacent resonators uniform.

[0008] The present disclosure is to solve the above-mentioned problems, and an object of the present disclosure is to make the frequency characteristics of adjacent resonators or elastic wave devices uniform.

[0009] Means used to solve problems

[0010] An elastic wave device involved in one embodiment includes a plurality of resonators, each of which includes: a supporting member having a thickness in a first direction; a piezoelectric layer arranged on the supporting member in the first direction; a functional electrode arranged on the piezoelectric layer in the first direction; and a protective film arranged in the first direction of the piezoelectric layer on which the resonators are arranged, wherein in the supporting member, a space portion is present at a position at which at least a portion overlaps with the functional electrode when viewed from above in the first direction, the plurality of resonators include a first resonator and a second resonator adjacent to the first resonator, an elastic modulus at a first position of the protective film is different from an elastic modulus at a second position different from the first position, the first position overlaps with the space portion of the first resonator when viewed from above in the first direction, and the second position overlaps with the space portion of the second resonator when viewed from above in the first direction.

[0011] A method for manufacturing an elastic wave device in one embodiment comprises: a stacking step of stacking a piezoelectric layer on a supporting member; an electrode forming step of forming a functional electrode on the piezoelectric layer; a protective film forming step of forming a protective film on the piezoelectric layer on which the functional electrode is formed; and a singulation step of singulating the supporting member after the protective film forming step to form an elastic wave device, wherein the piezoelectric layer stacked on the supporting member in the stacking step has a first position and a second position, the second position being a position where the thickness of the piezoelectric layer is thinner than the thickness of the piezoelectric layer at the first position, a first elastic wave device having the piezoelectric layer having the first position and a second elastic wave device having the piezoelectric layer having the second position are adjacent to each other before the singulation step, and in the protective film forming step, the elastic modulus of the protective film formed at the first position is formed to be different from the elastic modulus of the protective film formed at the second position.

[0012] Effects of the Invention

[0013] According to the present disclosure, the frequency characteristics of adjacent resonators or elastic wave devices can be made uniform. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0016] Figure 2 It is along Figure 1A A cross-sectional view of a portion taken along line II-II.

[0017] Figure 3A This is a schematic cross-sectional view for explaining Lamb waves propagating through the piezoelectric layer of the comparative example.

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

[0019] Figure 4 This is a schematic cross-sectional view for explaining the amplitude direction of the bulk wave of the thickness shear first-order mode propagating through the piezoelectric layer of the first embodiment.

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

[0021] Figure 6This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set to p and the average thickness of the piezoelectric layer is set to d in the elastic wave device of the first embodiment.

[0022] Figure 7 This is a schematic plan view showing an example in which a pair of electrodes is provided in the elastic wave device according to the first embodiment.

[0023] Figure 8 This is a reference diagram showing an example of the resonance characteristics of the elastic wave device according to the first embodiment.

[0024] Fig. 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the impedance of the spurious normalized by 180 degrees, which is the magnitude of the spurious, when a large number of spurious wave resonators are configured in the elastic wave device according to the first embodiment.

[0025] Fig.10 It is an explanatory diagram showing the relationship among d / 2p, metallization ratio MR and relative bandwidth.

[0026] Fig.11 This is an explanatory diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0027] Fig.12 This is a partially cutaway perspective view for explaining an elastic wave device according to an embodiment of the present disclosure.

[0028] Fig.13 It is a schematic cross-sectional view showing a part of the elastic wave device according to the first embodiment.

[0029] Fig.14 It is shown Fig.13 FIG. 2 is a circuit diagram of an example of an elastic wave device according to the first embodiment.

[0030] Fig.15 This is a diagram for explaining the relationship between the thickness of the piezoelectric layer of the elastic wave device according to the first embodiment and the required film thickness of the protective film.

[0031] Fig.16 It is a schematic cross-sectional view for explaining a lamination step in the method for manufacturing the elastic wave device according to the second embodiment.

[0032] Fig.17 It is a schematic cross-sectional view for explaining an electrode forming step in the method for manufacturing an elastic wave device according to the second embodiment.

[0033] Fig.18It is a schematic cross-sectional view for explaining a protective film forming step in the method for manufacturing an elastic wave device according to the second embodiment.

[0034] Fig.19 It is a schematic cross-sectional view for explaining a film thickness adjustment step in the method for manufacturing an elastic wave device according to the second embodiment.

[0035] Fig. 20 It is a schematic cross-sectional view for explaining a singulation step in the method for manufacturing the elastic wave device according to the second embodiment.

[0036] Fig.21 This is a schematic cross-sectional view for explaining an etching step of the elastic wave device according to the second embodiment.

[0037] Fig. 22 This is a flowchart showing a method for manufacturing an elastic wave device according to the second embodiment. DETAILED DESCRIPTION

[0038] Hereinafter, the embodiments of the present disclosure are described in detail based on the accompanying drawings. In addition, the present disclosure is not limited to the embodiments. In addition, the various embodiments described in the present disclosure are illustrative, and partial replacement or combination of structures can be performed between different embodiments. After the modified example and the second embodiment, the description of matters common to the first embodiment is omitted, and only the differences are described. In particular, the same effects brought about by the same structure are not mentioned one by one in each embodiment.

[0039] (First embodiment)

[0040] Figure 1A It is a perspective view showing the elastic wave device according to the first embodiment. Figure 1B It is a plan view showing the electrode structure of the first embodiment.

[0041] The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 including LiNbO3. The piezoelectric layer 2 may also be a piezoelectric layer including LiTaO3. The cutting angle of LiNbO3 and LiTaO3 in the first embodiment is Z-cut. The cutting angle of LiNbO3 and LiTaO3 may also be a rotated Y-cut or X-cut. Preferably, the propagation azimuth of Y propagation and X propagation is ±30°.

[0042] The thickness of the piezoelectric layer 2 is not particularly limited, but is preferably 50 nm to 1000 nm in order to effectively excite the thickness shear first-order mode.

[0043] The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b facing each other in the Z direction. The first main surface 2a is provided with electrode fingers 3 and electrode fingers 4. Alternatively, the electrode fingers 3 and electrode fingers 4 may be provided on the second main surface 2b.

[0044] Here, electrode finger 3 is an example of a "first electrode finger", and electrode finger 4 is an example of a "second electrode finger". Figure 1A as well as Figure 1B In the figure, the plurality of electrode fingers 3 are a plurality of "first electrode fingers" connected to the first bus bar 5. The plurality of electrode fingers 4 are a plurality of "second electrode fingers" connected to the second bus bar 6. The plurality of electrode fingers 3 and the plurality of electrode fingers 4 are interlaced with each other. Thus, an IDT (Interdigital Transducer) electrode having the electrode fingers 3, the electrode fingers 4, the first bus bar 5 and the second bus bar 6 is formed.

[0045] The electrode finger 3 and the electrode finger 4 have a rectangular shape and have a length direction. In a direction orthogonal to the length direction, the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 are opposed to each other. The length direction of the electrode fingers 3 and 4 and the direction orthogonal to the length direction of the electrode fingers 3 and 4 are directions intersecting the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 are opposed to 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 is sometimes set as the Z direction (or the first direction), the length direction of the electrode fingers 3 and the electrode fingers 4 is set as the Y direction (or the second direction), and the direction orthogonal to the electrode fingers 3 and the electrode fingers 4 is set as the X direction (or the third direction).

[0046] In addition, the length direction of the electrode fingers 3 and 4 can also be the same as Figure 1A as well as Figure 1B The length directions of the electrode fingers 3 and 4 shown are orthogonal to each other. Figure 1A as well as Figure 1B In the embodiment, the electrode fingers 3 and 4 may be extended in the direction in which the first bus bar 5 and the second bus bar 6 extend. In this case, the first bus bar 5 and the second bus bar 6 extend in the direction in which the first bus bar 5 and the second bus bar 6 extend. Figure 1A as well as Figure 1B The electrode fingers 3 and 4 extend in the extending direction. In addition, a plurality of pairs of adjacent electrode fingers 3 and 4 connected to one potential and another potential are provided in a direction perpendicular to the longitudinal direction of the electrode fingers 3 and 4.

[0047] Here, the so-called electrode finger 3 and electrode finger 4 are adjacent to each other, which means that the electrode finger 3 and electrode finger 4 are arranged with a gap, rather than the electrode finger 3 and electrode finger 4 are arranged in direct contact. In addition, when the electrode finger 3 and electrode finger 4 are adjacent to each other, electrodes connected to the signal (hot) electrode and the ground electrode including other electrode fingers 3 and electrode fingers 4 are not arranged between the electrode finger 3 and the electrode finger 4. The number of pairs does not need to be an integer pair, and can also be 1.5 pairs, 2.5 pairs, etc.

[0048] The center-to-center distance between electrode fingers 3 and electrode fingers 4, i.e., the spacing, is preferably in the range of 1 μm or more and 10 μm or less. In addition, the center-to-center distance between electrode fingers 3 and electrode fingers 4 is the distance connecting the center of the width dimension of electrode finger 3 in the direction perpendicular to the length direction of electrode finger 3 and the center of the width dimension of electrode finger 4 in the direction perpendicular to the length direction of electrode finger 4.

[0049] Furthermore, when at least one of the electrode fingers 3 and the electrode fingers 4 has multiple electrodes (when the electrode fingers 3 and the electrode fingers 4 are set as a pair of electrode groups, there are more than 1.5 pairs of electrode groups), the center-to-center distance of the electrode fingers 3 and the electrode fingers 4 refers to the average value of the center-to-center distances of adjacent electrode fingers 3 and the electrode fingers 4 among the more than 1.5 pairs of electrode fingers 3 and the electrode fingers 4.

[0050] In addition, the width of the electrode finger 3 and the electrode finger 4, that is, the size of the electrode finger 3 and the electrode finger 4 in the opposing direction is preferably in the range of 150 nm or more and 1000 nm or less. In addition, the so-called center-to-center distance between the electrode finger 3 and the electrode finger 4 is the distance connecting the center of the size (width dimension) of the electrode finger 3 in the direction orthogonal to the length direction of the electrode finger 3 and the center of the size (width dimension) of the electrode finger 4 in the direction orthogonal to the length direction of the electrode finger 4.

[0051] In the first embodiment, since a Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrode fingers 3 and 4 is a direction orthogonal to the polarization direction of the piezoelectric layer 2. This is not limited to the case where a piezoelectric body with another cutting angle is used as the piezoelectric layer 2. Here, the so-called "orthogonal" is not limited to the case of being strictly orthogonal, but may be approximately orthogonal (the angle formed by the direction orthogonal to the length direction of the electrode fingers 3 and 4 and the polarization direction is, for example, 90°±10°).

[0052] On the second main surface 2b side of the piezoelectric layer 2, a support substrate 8 is stacked via an intermediate layer 7. The intermediate layer 7 and the support substrate 8 form a support member. The intermediate layer 7 and the support substrate 8 have a frame-like shape, such as Figure 2As shown, the support substrate 8 has openings 7a and 8a. Thus, a space portion (air gap) 9 is formed. In addition, the support substrate 8 may also have a shape having a recessed portion. In addition, the space portion 9 may also be formed by a recessed portion provided in an intermediate layer.

[0053] The space portion 9 is provided so as not to hinder the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support substrate 8 is laminated on the second main surface 2b via the intermediate layer 7 at a position that does not overlap with the portion where at least one pair of electrode fingers 3 and electrode fingers 4 are provided. In addition, the support substrate 8 may be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2. That is, the intermediate layer 7 may not be provided. In this case, the support substrate 8 forms a support member.

[0054] The intermediate layer 7 is made of silicon oxide. However, the intermediate layer 7 may be made of a suitable insulating material other than silicon oxide, such as silicon nitride or alumina.

[0055] The supporting substrate 8 is formed of Si. The surface orientation of the Si on the side of the piezoelectric layer 2 can be (100), (110), or (111). Preferably, high-resistance Si with a resistivity of more than 4 kΩ is suitable. However, the supporting substrate 8 can also be composed of appropriate insulating materials or semiconductor materials. As the material of the supporting substrate 8, for example, piezoelectrics such as aluminum oxide, lithium tantalate, lithium niobate, and quartz, alumina, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, various ceramics, dielectrics such as diamond and glass, semiconductors such as gallium nitride, etc. can be used.

[0056] The plurality of electrode fingers 3, electrode fingers 4, first bus bar 5, and second bus bar 6 are made of appropriate metal or alloy such as Al, AlCu alloy, etc. In the first embodiment, the electrode fingers 3, electrode fingers 4, first bus bar 5, and second bus bar 6 have a structure in which an Al film is stacked on a Ti film. Alternatively, a bonding layer other than a Ti film may be used.

[0057] During driving, an AC voltage is applied between the electrode fingers 3 and the electrode fingers 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. This can obtain resonance characteristics of bulk waves using the thickness shear first-order mode excited in the piezoelectric layer 2.

[0058] In the elastic wave device 1, when the thickness of the piezoelectric layer 2 is d and the center-to-center distance between any adjacent electrode fingers 3 and 4 among the plurality of pairs of electrode fingers 3 and 4 is p, d / p is set to be 0.5 or less. Therefore, the bulk wave of the thickness shear first-order mode can be 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.

[0059] In addition, when there are multiple electrode fingers 3 and 4 as in the first embodiment, that is, when the electrode fingers 3 and 4 are set as a pair of electrode groups and there are more than 1.5 pairs of electrode fingers 3 and 4, the center distance between adjacent electrode fingers 3 and 4 becomes the average distance between the center distances of each adjacent electrode finger 3 and 4.

[0060] In the elastic wave device 1 of the first embodiment, since it has the above-mentioned structure, even if the number of pairs of electrode fingers 3 and 4 is reduced to achieve miniaturization, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides, and the propagation loss is small. In addition, the above-mentioned reflectors are not required because the bulk wave of the thickness shear first-order mode is used.

[0061] Figure 3A This is a schematic cross-sectional view for explaining Lamb waves propagating through a piezoelectric layer of a comparative example. Figure 3B This is a schematic cross-sectional view for explaining a bulk wave of a thickness shear first-order mode propagating through the piezoelectric layer of the first embodiment. Figure 4 This is a schematic cross-sectional view for explaining the amplitude direction of the bulk wave of the thickness shear first-order mode propagating through the piezoelectric layer of the first embodiment.

[0062] exist Figure 3A In the elastic wave device described in Patent Document 1, Lamb waves propagate in the piezoelectric layer. Figure 3A As shown in FIG. 1 , the wave propagates in the piezoelectric layer 201 as shown 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 3 and 4 of the IDT electrode are arranged. Figure 3A As shown, for Lamb waves, the waves propagate in the X direction as shown in the figure. Since it is a plate wave, the piezoelectric layer 201 vibrates as a whole, but since the wave propagates in the X direction, reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is achieved, that is, when the number of pairs of electrode fingers 3 and 4 is reduced, the Q value decreases.

[0063] In contrast, Figure 3BAs shown, in the elastic wave device of the first embodiment, since the vibration displacement is in the thickness shear direction, the wave propagates and resonates roughly in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, in the Z direction. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained by the propagation of the wave 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 pairs of electrode pairs including the electrode fingers 3 and the electrode fingers 4 is reduced in order to promote miniaturization, it is difficult to cause a decrease in the Q value.

[0064] In addition, if Figure 4 As shown, the amplitude direction of the body wave of the thickness shear first-order mode is in the excitation area C of the piezoelectric layer 2 (refer to Figure 1B ) and the second region 252 included in the excitation region C are opposite. Figure 4 , a body wave is schematically shown when a voltage is applied between electrode finger 3 and electrode finger 4 so that electrode finger 4 has a higher potential than electrode finger 3. The first region 251 is a region between the first principal surface 2a and the imaginary plane VP1 that is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts in the excitation region C. The second region 252 is a region between the imaginary plane VP1 and the second principal surface 2b in the excitation region C.

[0065] Although at least one pair of electrodes including electrode fingers 3 and electrode fingers 4 is provided in elastic wave device 1, since the wave is not propagated in the X direction, the number of electrode pairs including electrode fingers 3 and electrode fingers 4 does not necessarily need to be multiple. In other words, at least one pair of electrodes is sufficient.

[0066] For example, the electrode finger 3 is an electrode connected to the signal potential, and the electrode finger 4 is an electrode connected to the ground potential. However, the electrode finger 3 may be connected to the ground potential, and the electrode finger 4 may be connected to the signal potential. In the first embodiment, as described above, at least one pair of electrodes is an electrode connected to the signal potential or an electrode connected to the ground potential, and no floating electrode is provided.

[0067] Figure 5 is an explanatory diagram showing an example of the resonance characteristics of the elastic wave device according to the first embodiment. Figure 5 The design parameters of elastic wave device 1 having the resonance characteristics shown are as follows.

[0068] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°)

[0069] Thickness of piezoelectric layer 2: 400nm

[0070] Excitation area C (refer to Figure 1B ) length: 40μm

[0071] Number of pairs of electrodes including electrode finger 3 and electrode finger 4: 21 pairs

[0072] Center-to-center distance (pitch) between electrode finger 3 and electrode finger 4: 3 μm

[0073] Width of electrode finger 3 and electrode finger 4: 500nm

[0074] d / p:0.133

[0075] Intermediate layer 7: 1 μm thick silicon oxide film

[0076] Support substrate 8: Si

[0077] In addition, the so-called excitation area C (refer to Figure 1B ), is the area where the electrode fingers 3 and 4 overlap when viewed in the X direction orthogonal to the length direction of the electrode fingers 3 and 4. The length of the excitation region C is the dimension of the excitation region C along the length direction of the electrode fingers 3 and 4. Here, the excitation region C is an example of an “intersection region”.

[0078] In the first embodiment, the center-to-center distances of the electrode pairs including the electrode fingers 3 and the electrode fingers 4 are all equal in a plurality of pairs. That is, the electrode fingers 3 and the electrode fingers 4 are arranged at equal intervals.

[0079] Depend on Figure 5 It is clear that, despite the absence of a reflector, a good resonance characteristic with a relative bandwidth of 12.5% ​​is obtained.

[0080] In addition, when the thickness of the piezoelectric layer 2 is d and the center-to-center distance between the electrode fingers 3 and 4 is p, in the first embodiment, d / p is 0.5 or less, and more preferably 0.24 or less. Figure 6 Explain it.

[0081] and got Figure 5 The elastic wave devices having the same resonant characteristics as those shown above are obtained by changing d / 2p. Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set to p and the average thickness of the piezoelectric layer 2 is set to d in the elastic wave device of the first embodiment.

[0082] like Figure 6As shown in the figure, if d / 2p exceeds 0.25, that is, when d / p>0.5, even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / 2p≤0.25, that is, d / p≤0.5, if d / p is changed within this range, the relative bandwidth can be set to more than 5%, that is, a resonator with a high coupling coefficient can be constructed. In addition, when d / 2p is less than 0.12, that is, when d / p is less than 0.24, the relative bandwidth can be increased to more than 7%. Moreover, if d / p is adjusted within this range, a resonator with a wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be realized. Therefore, it can be seen that by setting d / p to less than 0.5, a resonator with a high coupling coefficient that utilizes the body wave of the above-mentioned thickness shear first-order mode can be constructed.

[0083] In addition, at least one pair of electrodes may be one pair, and in the case of one pair of electrodes, the above p is set to the distance between the centers of adjacent electrode fingers 3 and 4. In the case of more than 1.5 pairs of electrodes, the average distance between the centers of adjacent electrode fingers 3 and 4 may be set to p.

[0084] Furthermore, regarding the thickness d of the piezoelectric layer 2 , even when the piezoelectric layer 2 has thickness variations, an average value of the thicknesses may be used.

[0085] Figure 7 1 is a schematic top view showing an example in which a pair of electrodes is provided in the elastic wave device of the first embodiment. In the elastic wave device 101, a pair of electrodes including electrode fingers 3 and electrode fingers 4 are provided on the first principal surface 2a of the piezoelectric layer 2. Figure 7 K in is the crossing width. As described above, in the elastic wave device of the present disclosure, the number of pairs of electrodes may be 1 pair. In this case as well, as long as the above d / p is 0.5 or less, the body wave of the thickness shear first-order mode can be effectively excited.

[0086] In the elastic wave device 1, it is preferred that the metallization ratio MR of any adjacent electrode fingers 3 and electrode fingers 4 among the plurality of electrode fingers 3 and electrode fingers 4 relative to the excitation region C satisfies MR≤1.75(d / p)+0.075, and the excitation region C is a region where the adjacent electrode fingers 3 and electrode fingers 4 overlap when viewed in opposite directions. In this case, the stray can be effectively reduced. Figure 8 as well as Fig. 9 Explain it.

[0087] Figure 8This is a reference diagram showing an example of the resonance characteristics of the elastic wave device of the first embodiment. The spurious signal indicated by arrow B appears between the resonance frequency and the antiresonance frequency. In addition, d / p=0.08 is set, and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). In addition, the metallization ratio MR is set to 0.35.

[0088] Reference Figure 1B To illustrate the metallization ratio MR. Figure 1B In the electrode structure, when focusing on one pair of electrode fingers 3 and electrode fingers 4, it is assumed that only the one pair of electrode fingers 3 and electrode fingers 4 are provided. In this case, the portion surrounded by the single-dot chain line becomes the excitation region C. The so-called excitation region C refers to the region of the electrode fingers 3 overlapping with the electrode fingers 4, the region of the electrode fingers 4 overlapping with the electrode fingers 3, and the region between the electrode fingers 3 and the electrode fingers 4 overlapping with each other when the electrode fingers 3 and the electrode fingers 4 are observed in the direction perpendicular to the length direction of the electrode fingers 3 and the electrode fingers 4, that is, in the opposite direction. And, the area of ​​the electrode fingers 3 and the electrode fingers 4 in the excitation region C relative to the area of ​​the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0089] When a plurality of pairs of electrode fingers 3 and electrode fingers 4 are provided, the ratio of the total area of ​​the metallized portions included in all the excitation regions C to the excitation regions C may be defined as MR.

[0090] Fig. 9 This is an explanatory diagram showing the relationship between the relative bandwidth of the elastic wave device of the first embodiment, when a plurality of elastic wave resonators are formed, and the phase rotation amount of the impedance of the spurious signal normalized by 180 degrees as the magnitude of the spurious signal. In addition, the relative bandwidth was adjusted by making various changes to the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4. In addition, Fig. 9 These are the results obtained when the piezoelectric layer 2 including Z-cut LiNbO 3 is used; however, the same tendency is observed when the piezoelectric layer 2 having other cut angles is used.

[0091] exist Fig. 9 In the area surrounded by ellipse J, the spurious value is as large as 1.0. Fig. 9 It is clear that if the relative bandwidth exceeds 0.17, that is, if it exceeds 17%, even if the parameters constituting the relative bandwidth are changed, large spurious with a spurious level of 1 or more will appear in the passband. Figure 8 As shown in the resonance characteristics, large spurious signals indicated by arrow B appear in the frequency band. Therefore, the relative bandwidth is preferably 17% or less. In this case, spurious signals can be reduced by adjusting the film thickness of the piezoelectric layer 2, the size of the electrode fingers 3 and 4, and the like.

[0092] Fig.10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio MR, and relative bandwidth. In the elastic wave device 1 according to the first embodiment, various elastic wave devices 1 having different d / 2p and MR were constructed, and the relative bandwidth was measured. Fig.10 The portion marked with shade on the right side of the dotted line D is an area where the relative bandwidth is less than 17%. The boundary between the shaded area and the unshaded area is represented by MR=3.5(d / 2p)+0.075. That is, MR=1.75(d / p)+0.075. Therefore, it is preferred that MR≤1.75(d / p)+0.075. In this case, it is easy to set the relative bandwidth to less than 17%. More preferably, Fig.10 The area on the right side of MR=3.5(d / 2p)+0.05 indicated by the dashed line D1 in FIG. 1. That is, if MR≤1.75(d / p)+0.05, the relative bandwidth can be reliably set to 17% or less.

[0093] Fig.11 This is an explanatory diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible. Fig.11 The portion indicated by hatching is a region where a relative bandwidth of at least 5% is obtained. If the range of the region is approximated, it becomes a range represented by the following equations (1), (2), and (3).

[0094] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0095] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, {180°-60°(1-(θ-50) 2 / 900) 1 / 2}~180°) …Formula (2)

[0096] (0°±10°, {180°-30° (1-(ψ-90) 2 / 8100) 1 / 2}~180°, any ψ) …Formula (3)

[0097] Therefore, in the case of the Euler angle range of the above-mentioned formula (1), formula (2) or formula (3), the relative bandwidth can be sufficiently widened, which is preferable.

[0098] Fig.12 FIG. 1 is a partially cutaway perspective view for explaining an elastic wave device according to an embodiment of the present disclosure. Fig.12 In FIG. 1 , the outer periphery of the space portion 9 is shown by a dotted line. The elastic wave device disclosed in the present invention may also be an elastic wave device using plate waves. In this case, Fig.12 As shown, the elastic wave device 301 has reflectors 310 and 311. The reflectors 310 and 311 are arranged on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the direction of propagation of the elastic wave. In the elastic wave device 301, by applying an alternating electric field to the electrode fingers 3 and 4 on the space portion 9, Lamb waves as plate waves can be excited. At this time, since the reflectors 310 and 311 are arranged on both sides, the resonance characteristics caused by the Lamb waves as plate waves can be obtained.

[0099] As described above, in the elastic wave devices 1 and 101, the bulk wave of the thickness shear first-order mode is used. In addition, in the elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes, and when the thickness of the piezoelectric layer 2 is d and the center distance between the first electrode finger 3 and the second electrode finger 4 is p, d / p is set to be less than or equal to 0.5. Thus, even if the elastic wave device is miniaturized, the Q value can be improved.

[0100] In the elastic wave device 1, 101, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. On the first principal surface 2a or the second principal surface 2b of the piezoelectric layer 2, there are first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2, and the first electrode fingers 3 and the second electrode fingers 4 are preferably covered with a protective film.

[0101] Fig.13 FIG. 2 is a schematic cross-sectional view showing a portion of the elastic wave device according to the first embodiment. Fig.13 As shown, the elastic wave device 1A involved in the first embodiment is an elastic wave device having a plurality of resonators. The plurality of resonators include a first resonator R1 and a second resonator R2. The first resonator R1 and the second resonator R2 are adjacent to each other when viewed from above in the Z direction. The two resonators are adjacent to each other, which means that there is no other elastic wave device between the two resonators when viewed from above in the Z direction. The first resonator R1 and the second resonator R2 include a functional electrode, a support member 80, a piezoelectric layer 2, and a protective film 14.

[0102] The functional electrodes of the first resonator R1 and the second resonator R2 are IDT electrodes including electrode fingers 3 and 4 and bus bars 5 and 6. The IDT electrodes are provided on the first principal surface 2a of the piezoelectric layer 2.

[0103] The support member 80 includes a support substrate 8 and an intermediate layer 7. The support member 80 has a plurality of space portions 9. When viewed from above in the Z direction, the space portions 9 are provided at positions where at least a portion overlaps with the first resonator R1 and the second resonator R2. Fig.13In the example of , the space portion 9 only penetrates the intermediate layer 7, but is not limited to this, and may be a space portion that penetrates the support member 80 in the Z direction, or may be a space portion provided on the piezoelectric layer 2 side of the intermediate layer 7. In addition, the support member 80 is not limited to this, and may be a support member that does not have the intermediate layer 7 but includes the support substrate 8. In this case, the space portion 9 may also be a space portion provided on the piezoelectric layer 2 side of the support substrate 8. In the following description, the space portion 9 located at a position overlapping with the first resonator R1 and the second resonator R2 when viewed from above in the Z direction is respectively described as the space portion of the first resonator R1 and the space portion of the second resonator R2.

[0104] The piezoelectric layer 2 has a through hole 2H. The through hole 2H is a hole that penetrates the piezoelectric layer 2 and the protective film 14 in the Z direction. The through hole 2H communicates with the space 9. The through hole 2H is provided at a position that does not overlap with the functional electrode of the resonator when viewed in the Z direction.

[0105] The thickness of the piezoelectric layer 2 varies depending on the position on the XY plane. When viewed from above in the Z direction, the thickness of the piezoelectric layer 2 at the position overlapping with the second position P2 is smaller than the thickness of the piezoelectric layer 2 at the position overlapping with the first position P1. The so-called first position P1 is a position at the position of the protective film 14 described later and overlapping with the space portion of the first resonator R1 when viewed from above in the Z direction. The so-called second position P2 is a position different from the first position P1, at the position of the protective film 14 and overlapping with the space portion of the second resonator R2 when viewed from above in the Z direction. The difference in the thickness of the piezoelectric layer 2 is derived from the manufacturing deviation in the process of stacking the piezoelectric layer 2. In this case, due to the difference in the thickness of the piezoelectric layer 2 at the first position P1 and the second position P2, the frequency characteristics of the adjacent first resonator R1 and second resonator differ.

[0106] The thickness of the piezoelectric layer 2 can be measured by optical measurement such as ellipsometry or high-frequency probe (RF probe) measurement. Here, when the RF probe measurement is used, the RF probe measurement is performed on the mode of the elastic wave device 1A, that is, the mode whose frequency depends on the thickness of the piezoelectric layer 2, and the obtained frequency of the mode is converted into the thickness of the piezoelectric layer 2, thereby obtaining the distribution of the thickness of the piezoelectric layer in the XY plane.

[0107] The protective film 14 is a film provided on the main surface of the piezoelectric layer 2. The protective film 14 includes a dielectric such as silicon oxide or silicon oxynitride. For example, the protective film 14 includes silicon oxide. The protective film 14 is provided as a single layer over the entire surface of the first main surface 2a of the piezoelectric layer 2 so as to cover the first main surface 2a, the first resonator R1, and the functional electrode of the second resonator. Here, the protective film 14 is a single layer, which means that the protective film 14 includes the same material over the Z direction.

[0108] The thickness of the protective film 14 varies depending on the position on the XY plane. The thickness of the protective film 14 is different at the first position P1 and the second position P2. In the first embodiment, the thickness of the protective film 14 at the first position P1 is smaller than the thickness at the second position P2. Here, like the thickness of the piezoelectric layer 2, the thickness of the protective film 14 can be measured by optical measurement such as ellipsometry or RF probe measurement. As a result, the difference in frequency characteristics between the first resonator R1 and the second resonator R2 caused by the difference in thickness of the piezoelectric layer 2 can be reduced.

[0109] Hereinafter, the thickness of the piezoelectric layer 2 required to make the frequency characteristics of the first resonator R1 and the second resonator R2 uniform is described as the required thickness of the piezoelectric layer 2. Here, if the elastic modulus of the protective film 14 is set to be uniform in the XY plane, when the difference between the thickness of the piezoelectric layer 2 at the first position P1 and the second position P2 is large, it is necessary to process so that the difference between the thickness of the protective film 14 required at the first position P1 and the second position P2 becomes large. In this case, the difference in the thickness of the protective film 14 required may increase to a degree that makes processing difficult.

[0110] The elastic modulus of the protective film 14 is different depending on the position on the XY plane. The elastic modulus of the protective film 14 is different at the first position P1 and the second position P2. In the first embodiment, the elastic modulus of the protective film 14 at the first position P1 is smaller than the elastic modulus at the second position P2. The elastic modulus of the protective film 14 can be measured as a longitudinal wave elastic modulus measured by a pulse laser method, an X-ray reflectivity method, or the like. Thus, it is possible to suppress the frequency characteristics of the adjacent first resonator R1 and the second resonator R2 from becoming different due to the difference in the thickness of the piezoelectric layer 2. In addition, thereby, it is possible to reduce the difference in the film thickness of the protective film 14 required at the first position P1 and the second position P2 to a processable degree, so that it is possible to easily adjust the film thickness of the protective film corresponding to the distribution of the thickness of the piezoelectric layer. Therefore, it is possible to make the frequency characteristics of the adjacent first resonator R1 and the second resonator R2 uniform.

[0111] When the protective film 14 is stacked by sputtering, the elastic modulus of the protective film 14 can be adjusted by changing parameters such as the bias power of the sputtering device according to the position in the XY plane. In addition, the elastic modulus of the protective film 14 can also be adjusted by changing the composition of the protective film 14 according to the position in the XY plane. For example, when the protective film 14 includes silicon oxide or silicon oxynitride, the elastic modulus of the protective film 14 can be locally increased by locally increasing the composition ratio of Si.

[0112] Fig.14 It is shown Fig.13FIG. 1 is a circuit diagram of an example of an elastic wave device according to the first embodiment. Fig.14 As shown, elastic wave device 1A is a so-called ladder filter having an input terminal IN, an output terminal OUT, a series arm connecting the input terminal IN and the output terminal OUT, and a parallel arm connecting a node of the series arm and ground. The plurality of resonators provided in elastic wave device 1A include a series arm resonator provided in the series arm and a parallel arm resonator provided in the parallel arm. Fig.14 In the embodiment, the series arm resonator is the resonator SR1 to SR3. One terminal of the resonator SR1 to SR3 as the series arm resonator is electrically connected to the input terminal IN, and the other terminal is electrically connected to the output terminal OUT. Here, the resonators SR1 to SR3 are electrically connected in series. On the other hand, in Fig.14 In the embodiment, the parallel arm resonators are resonators PR1 to PR4. One terminal of resonator PR1 is electrically connected to input terminal IN via wiring, and the other terminal is electrically connected to ground. One terminal of resonator PR2 is electrically connected to wiring connecting resonator SR1 and resonator SR2, and the other terminal is electrically connected to ground. One terminal of resonator PR3 is electrically connected to wiring connecting resonator SR2 and resonator SR3, and the other terminal is electrically connected to ground. One terminal of resonator PR4 is electrically connected to output terminal OUT via wiring, and the other terminal is electrically connected to ground. In addition, Fig.14 The numbers and alignments of the series arm resonators and parallel arm resonators shown are merely examples and are not limited thereto. For example, the series arm resonators and parallel arm resonators may be resonators divided by resonators connected in parallel or in series.

[0113] The first resonator R1 and the second resonator R2 are resonators inserted in the same signal path. That is, the first resonator R1 and the second resonator R2 are both series arm resonators or parallel arm resonators. In the first embodiment, one of the two resonators adjacent to each other among the resonators SR1 to SR3 is the first resonator R1, and the other is the second resonator R2. Thus, since the frequency characteristics of the series arm resonators can be made uniform, the frequency characteristics of the elastic wave device 1A can be improved. In the first embodiment, one of the two resonators adjacent to each other among the resonators PR1 to PR4 is the first resonator R1, and the other is the second resonator R2. Thus, since the frequency characteristics of the parallel arm resonators can be made uniform, the frequency characteristics of the elastic wave device 1A can be improved.

[0114] Fig.15 1 is a diagram illustrating the relationship between the thickness of the piezoelectric layer of the elastic wave device according to the first embodiment and the required film thickness of the protective film. Fig.15The thickness of the protective film required to make the frequency characteristics of the resonators involved in positions 1 to 5 of the piezoelectric layer the same, assuming the thickness of the piezoelectric layer 2. Positions 1 to 5 of the piezoelectric layer are different positions of the piezoelectric layer 2. Here, the resonators involved in positions 1 to 5 of the piezoelectric layer are resonators that are arranged at positions overlapping with the space portion 9 that overlaps with positions 1 to 5 of the piezoelectric layer when viewed from above in the Z direction. Here, the resonator involved in position 2 of the piezoelectric layer is adjacent to the resonators involved in positions 1 and 3 of the piezoelectric layer, and the resonator involved in position 4 of the piezoelectric layer is adjacent to the resonators involved in positions 3 and 5 of the piezoelectric layer. Fig.15 In the comparative example, the elastic wave device is one in which the elastic modulus of the protective film 14 is made uniform in the XY plane. Fig.15 In the embodiment, the elastic wave device according to the first embodiment is provided in which the elastic modulus of the protective film 14 is reduced as the thickness of the piezoelectric layer 2 increases. Fig.15 As shown, it can be seen that by making the elastic modulus of the protective film 14 different according to the distribution of the thickness of the piezoelectric layer 2, the difference in the thickness of the protective film 14 required at positions related to adjacent resonators can be reduced, and the distribution of the thickness of the protective film 14 can be smoothed.

[0115] As described above, the elastic wave device according to the first embodiment includes a plurality of resonators, each of which includes a support member 80 having a thickness in the first direction, a piezoelectric layer 2 provided in the first direction of the support member 80, a functional electrode provided in the first direction of the piezoelectric layer 2, and a protective film 14 provided in the first direction of the piezoelectric layer 2 on which the resonator is provided. In the support member 80, a space portion 9 is provided at a position at least partially overlapping with the functional electrode when viewed from above in the first direction. The plurality of resonators include a first resonator R1 and a second resonator R2 adjacent to the first resonator R1. The elastic modulus at the first position P1 of the protective film 19 is different from the elastic modulus at the second position P2 different from the first position P1. The first position P1 overlaps with the space portion 9 of the first resonator R1 when viewed from above in the first direction. The second position P2 overlaps with the space portion 9 of the second resonator R2 when viewed from above in the first direction. Thus, it is possible to suppress the frequency characteristics of the adjacent first resonator R1 and second resonator R2 from becoming different due to the difference in thickness of the piezoelectric layer 2. Furthermore, when the protective film 14 is processed to adjust the film thickness, the difference in the film thickness of the protective film 14 required at the first position P1 and the second position P2 can be reduced to a processable level. Therefore, the frequency characteristics of the adjacent first resonator R1 and second resonator R2 can be made uniform.

[0116] As a preferred embodiment, the thickness of the piezoelectric layer 2 at the position overlapping with the second position P2 when viewed from above in the first direction is thinner than the thickness of the piezoelectric layer 2 at the position overlapping with the first position P1, and the elastic modulus of the protective film 14 at the first position P1 when viewed from above in the first direction is smaller than the elastic modulus of the protective film 14 at the second position P2. As a result, the frequency characteristics of the adjacent first resonator R1 and second resonator R2 can be further suppressed from becoming different due to the difference in the thickness of the piezoelectric layer 2. In addition, the difference in the film thickness of the protective film 14 required at the first position P1 and the second position P2 can be further reduced to a processable level. Therefore, the frequency characteristics of the adjacent first resonator R1 and second resonator R2 can be made uniform.

[0117] As a preferred embodiment, the device further comprises an input terminal IN, an output terminal OUT, a series arm connecting the input terminal IN and the output terminal OUT, and a parallel arm connecting a node of the series arm to ground. The plurality of resonators include a series arm resonator provided in the series arm and a parallel arm resonator provided in the parallel arm, and the first resonator and the second resonator are series arm resonators. Thus, the frequency characteristics of the series arm resonators can be made uniform.

[0118] As a preferred embodiment, the device further comprises an input terminal IN, an output terminal OUT, a series arm connecting the input terminal IN and the output terminal OUT, and a parallel arm connecting a node of the series arm to ground. The plurality of resonators include a series arm resonator provided in the series arm and a parallel arm resonator provided in the parallel arm, and the first resonator and the second resonator are parallel arm resonators. Thus, the frequency characteristics of the parallel arm resonators can be made uniform.

[0119] As a preferred embodiment, the piezoelectric layer 2 includes lithium niobate or lithium tantalate. This can provide an elastic wave device that can obtain good resonance characteristics.

[0120] As a more preferred embodiment, the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer 2 are within the ranges of the following formula (1), formula (2), or formula (3). In this case, the relative bandwidth can be sufficiently widened.

[0121] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0122] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2)

[0123] (0°±10°, [180°-30° (1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ) …Formula (3)

[0124] As a preferred embodiment, the functional electrode is an IDT electrode having a first bus bar 5, a second bus bar 6 opposite to the first bus bar 5, a plurality of first electrode fingers 3 connected at one end to the first bus bar 5, and a plurality of second electrode fingers 4 connected at one end to the first bus bar 5. Thus, a bulk wave of a thickness shear first-order mode can be excited.

[0125] As a preferred embodiment, when the film thickness of the piezoelectric layer 2 is d and the center-to-center distance between adjacent first electrode fingers 3 and second electrode fingers 4 is p, d / p is equal to or less than 0.5. This can effectively excite bulk waves of the thickness shear first-order mode.

[0126] As a more preferred embodiment, d / p is equal to or less than 0.24. This makes it possible to more effectively excite the bulk wave of the thickness shear first-order mode.

[0127] As a preferred method, when the overlapping region of the adjacent first electrode fingers 3 and second electrode fingers 4 when viewed in opposite directions is set as the excitation region, when the metallization ratio of the plurality of first electrode fingers 3 and second electrode fingers 4 relative to the excitation region is set as MR, MR≤1.75(d / p)+0.075 is satisfied. Thus, the stray light can be effectively reduced.

[0128] As a preferred embodiment, the structure is such that a thickness shear mode bulk wave can be utilized. This improves the coupling coefficient and enables obtaining good resonance characteristics.

[0129] (Second embodiment)

[0130] Hereinafter, an elastic wave device according to the second embodiment will be described. In the first embodiment, an elastic wave device in which the elastic modulus of the protective film 14 is different at each position overlapping with the space portion of the resonator according to the distribution of the thickness of the piezoelectric layer 2 in one elastic wave device 1A is described, but in the second embodiment, in the manufacturing process of a plurality of elastic wave devices, the elastic modulus of the protective film 14 is different in each elastic wave device according to the distribution of the thickness of the piezoelectric layer 2 in one wafer. Hereinafter, a manufacturing method of the elastic wave device according to the second embodiment will be described using the accompanying drawings. The elastic wave device according to the second embodiment includes a stacking process, an electrode forming process, a protective film forming process, a film thickness inspection process, a film thickness adjustment process, a singulation process, and an etching process.

[0131] Fig.162 is a schematic cross-sectional view for explaining a lamination step in a method for manufacturing an elastic wave device according to the second embodiment. Fig.16 As shown, the lamination process is a process of laminating the piezoelectric layer 2 on the supporting member 80. In the second embodiment, the sacrificial layer 7S and the intermediate layer 7 are laminated on the supporting substrate 8, and the piezoelectric layer 2 is laminated on the sacrificial layer 7S and the intermediate layer 7 side of the supporting substrate 8, thereby laminating the piezoelectric layer 2 on the supporting member 80. Here, the laminated piezoelectric layer 2 is thinned by grinding the main surface of the piezoelectric layer 2 on the side opposite to the second main surface 2b. At this time, the thickness of the first position P1 and the second position P2 of the piezoelectric layer 2 are different. In the following, the laminated body of the piezoelectric layer 2, the intermediate layer 7 and the supporting substrate 8 forming a plurality of elastic wave devices is sometimes referred to as a "mother substrate" for explanation.

[0132] Here, the first position P1 is located at the piezoelectric layer of the first elastic wave device 1B, and the second position P2 is located at the piezoelectric layer of the second elastic wave device 1C. The first elastic wave device 1B and the second elastic wave device 1C are elastic wave devices according to the second embodiment. Before the singulation process described later, the first elastic wave device 1B and the second elastic wave device 1C are adjacent to each other on the mother substrate. The two elastic wave devices are adjacent to each other, which means that there is no other elastic wave device between the two elastic wave devices when viewed from above in the Z direction.

[0133] Fig.17 2 is a schematic cross-sectional view for explaining an electrode forming step in a method for manufacturing an elastic wave device according to the second embodiment. Fig.17 As shown in FIG. 1 , the electrode forming step is a step of forming a functional electrode of the resonator on the piezoelectric layer 2. In the second embodiment, a plurality of functional electrodes are provided on the first main surface 2a of the piezoelectric layer 2. Here, the functional electrode is a Figure 2 The IDT electrodes shown are electrode fingers 3 and 4 and bus bars 5 and 6. In the second embodiment, each of the functional electrodes is provided at a position where at least a portion overlaps with the sacrificial layer 7S in a plan view in the Z direction.

[0134] In the second embodiment, the distribution of the thickness of the piezoelectric layer is measured before the protective film forming step. For example, after the piezoelectric layer 2 is stacked, the distribution of the thickness of the piezoelectric layer is measured using optical measurements such as ellipsometry. In addition, the distribution of the thickness of the piezoelectric layer 2 can also be obtained by measuring the frequency of the mode of the elastic wave device using an RF probe measurement after the functional electrode is formed. In this case, the RF probe measurement is performed on the mode whose frequency depends on the thickness of the piezoelectric layer 2, and the obtained frequency of the mode is converted into the thickness of the piezoelectric layer 2, thereby obtaining the distribution of the thickness of the piezoelectric layer 2.

[0135] Fig.182 is a schematic cross-sectional view for explaining a protective film forming step in a method for manufacturing an elastic wave device according to a second embodiment. Fig.18 As shown, the protective film forming process is a process of forming a protective film 14 on the piezoelectric layer 2 on which the functional electrode is formed. In the second embodiment, the protective film 14 is formed on the first main surface 2a of the piezoelectric layer 2 so as to cover the functional electrode. At this time, based on the distribution of the thickness of the piezoelectric layer 2 measured as described above, the protective film 14 is formed so that the elastic modulus of the protective film 14 set at the first position P1 and the second position P2 are different. Specifically, the density of the protective film is locally increased by using a processing device, thereby locally increasing the elastic modulus. In addition, in the case where the protective film 14 includes silicon oxide, the elastic modulus can also be locally increased by locally increasing the amount of silicon relative to oxygen. Thereby, in the film thickness adjustment process described later, the distribution of the film thickness of the desired protective film 14 can be smoothed to a degree that can be processed. After laminating the protective film 14, the distribution of the elastic modulus of the protective film 14 is measured by a pulse laser method, an X-ray reflectivity method, or the like. Thus, based on the distribution of the thickness of the piezoelectric layer 2 and the distribution of the elastic modulus of the protective film 14 measured as described above, the distribution of the film thickness of the protective film 14 required can be calculated.

[0136] The film thickness inspection process is a process for inspecting by measuring the distribution of the film thickness of the protective film 14. In the film thickness inspection process, the distribution of the film thickness of the protective film 14 is measured using the above-mentioned method for measuring the distribution of the film thickness of the piezoelectric layer 2. In the film thickness inspection process, if the distribution of the film thickness of the protective film 14 is inconsistent with the distribution of the film thickness of the required protective film 14, it is determined that the film thickness of the protective film 14 is inappropriate, and the process proceeds to the film thickness adjustment process. On the other hand, in the film thickness inspection process, if the distribution of the film thickness of the protective film 14 is consistent with the distribution of the film thickness of the required protective film 14, it is determined that the film thickness of the protective film 14 is appropriate, and the process proceeds to the singulation process.

[0137] Fig.19 2 is a schematic cross-sectional view for explaining a film thickness adjustment step in a method for manufacturing an elastic wave device according to the second embodiment. Fig.19 As shown, the film thickness adjustment process is a process for adjusting the film thickness of the protective film 14. In the film thickness adjustment process, the film thickness of the protective film 14 is adjusted by thinning the protective film 14 using ion milling. Ion milling is performed by processing the protective film 14 using an ion beam while moving the irradiation position of the ion beam along a processing path in a certain direction. After the film thickness adjustment process, the film thickness inspection process is entered again. The film thickness adjustment process and the film thickness inspection process are repeated until the film thickness of the protective film 14 is determined to be appropriate in the film thickness inspection process. As a result, the frequency characteristics of the first elastic wave device 1B and the second elastic wave device 1C can be made uniform in the singulation process described later.

[0138] Fig. 20 2 is a schematic cross-sectional view for explaining the singulation step of the method for manufacturing the elastic wave device according to the second embodiment. Fig. 20 As shown, the singulation step is a step of singulating the mother substrate after the protective film forming step into a plurality of elastic wave devices. In the singulation step, the mother substrate is patterned into a grid shape to remove the boundary portions of the chip units of the plurality of elastic wave devices, thereby dividing the plurality of elastic wave devices including the first elastic wave device 1B and the second elastic wave device 1C into chip units.

[0139] Fig.21 FIG. 2 is a schematic cross-sectional view for explaining the etching process of the elastic wave device according to the second embodiment. Fig.21 As shown, the etching process is a process of removing the sacrificial layer 7S to form the space portion 9. More specifically, in the etching process, a through hole 2H is provided at a position where the piezoelectric layer 2 overlaps with the sacrificial layer 7S when viewed from above in the Z direction, and after the inner wall of the through hole 2H is protected with a resist, an etching solution is injected from the through hole 2H to dissolve the sacrificial layer 7S to form the space portion 9. In the second embodiment, the through hole 2H is provided by dry etching the piezoelectric layer 2 after the resist is patterned. In addition, after the sacrificial layer 7S is dissolved, the resist on the inner wall of the through hole 2H is removed. Thus, a plurality of elastic wave devices including a first elastic wave device 1B and a second elastic wave device 1C are manufactured.

[0140] Fig. 22 FIG. 4 is a flow chart showing a method for manufacturing an elastic wave device according to the second embodiment. Fig. 22 As shown, the manufacturing method of the elastic wave device involved in the second embodiment is carried out in the following order. The piezoelectric layer 2 is stacked on the supporting member 80 (step S10), electrodes such as functional electrodes are formed on the piezoelectric layer 2 (step S20), the protective film 14 is stacked on the piezoelectric layer 2 (step S30), and the film thickness of the protective film is inspected (step S40). When the result of the inspection is that the distribution of the film thickness of the protective film is inappropriate (step S50: No), the film thickness of the protective film 14 is adjusted (step S60). The inspection of the film thickness of the protective film 14 and the adjustment of the film thickness of the protective film 14 are repeated until the distribution of the film thickness of the protective film becomes the desired distribution of the film thickness of the protective film 14. When the result of the inspection is that the distribution of the film thickness of the protective film is appropriate (step S50: Yes), the mother substrate is singulated as an elastic wave device (step S70), and the sacrificial layer 7S is etched (step S80), thereby manufacturing the elastic wave device involved in the second embodiment. In addition, the manufacturing method of the elastic wave device involved in the second embodiment is not limited to Fig. 22 The related processes may include other steps, for example, and the steps may be interchanged with each other.

[0141] As described above, the method for manufacturing an elastic wave device according to the second embodiment includes a lamination step of laminating the piezoelectric layer 2 on the support member 80, an electrode formation step of forming a functional electrode on the piezoelectric layer 2, a protective film formation step of forming the protective film 14 on the piezoelectric layer 2 on which the functional electrode is formed, and a singulation step of singulating the support member 80 after the protective film formation step into individual pieces to form an elastic wave device. In the lamination step, the piezoelectric layer 2 stacked on the support member 80 has a first position P1 and a second position P2, the second position P2 being a position where the thickness of the piezoelectric layer 2 is thinner than the thickness of the piezoelectric layer 2 at the first position P1. The first elastic wave device 1B having the piezoelectric layer 2 having the first position P1 and the second elastic wave device 1C having the piezoelectric layer 2 having the second position P2 are adjacent to each other before the singulation step. In the protective film formation step, the elastic modulus of the protective film 14 formed at the first position P1 is formed to be different from the elastic modulus of the protective film 14 formed at the second position P2. Thus, it is possible to suppress the frequency characteristics of the adjacent first elastic wave device 1B and second elastic wave device 1C from becoming different due to the difference in thickness of the piezoelectric layer 2. In addition, when the protective film 14 is processed to adjust the film thickness, the difference in the film thickness of the protective film 14 required at the first position P1 and the second position P2 can be reduced to a degree that allows processing. Therefore, the frequency characteristics of the adjacent first elastic wave device 1B and second elastic wave device 1C can be made uniform.

[0142] As a preferred embodiment, there is also a film thickness adjustment step for adjusting the film thickness of the protective film 14. Thus, the film thickness of the protective film 14 of the adjacent first elastic wave device 1B and the second elastic wave device 1C can be made to be the desired film thickness of the protective film 14, so that the frequency characteristics of the adjacent first elastic wave device 1B and the second elastic wave device 1C can be further made uniform.

[0143] In addition, in the film thickness adjustment step, ion milling is used to adjust the film thickness of the protective film 14. In this case, since the elastic modulus of the protective film 14 is locally different in the protective film lamination step, the distribution of the film thickness of the protective film 14 required to make the frequency characteristics of the first position P1 and the second position P2 the same is set to be smooth to the extent that can be processed by ion milling, so that the frequency characteristics of the adjacent first elastic wave device 1B and second elastic wave device 1C can be made uniform.

[0144] In addition, the above-mentioned embodiments are for easy understanding of the present disclosure, and are not intended to be interpreted in a limiting manner. The present disclosure can be changed / improved without departing from the gist thereof, and the present disclosure also includes its equivalents.

[0145] In addition, the present invention can also adopt the following aspects.

[0146] <1> An elastic wave device comprises a plurality of resonators.

[0147] The plurality of resonators respectively include:

[0148] A supporting member having a thickness in a first direction;

[0149] A piezoelectric layer is arranged in the first direction of the supporting member;

[0150] A functional electrode is arranged in the first direction of the piezoelectric layer; and

[0151] a protective film disposed in a first direction of the piezoelectric layer on which the resonator is disposed,

[0152] The support member has a space portion at a position at which at least a portion overlaps with the functional electrode when viewed from above in the first direction.

[0153] The plurality of resonators include a first resonator and a second resonator adjacent to the first resonator.

[0154] The elastic modulus of the protective film at a first position is different from the elastic modulus of the protective film at a second position different from the first position.

[0155] The first position overlaps with the space portion of the first resonator when viewed in plan in the first direction.

[0156] The second position overlaps with a space portion of the second resonator in a plan view in the first direction.

[0157] <2> according to <1> The elastic wave device, wherein:

[0158] When viewed from above in the first direction, the thickness of the piezoelectric layer at a position overlapping the second position is thinner than the thickness of the piezoelectric layer at a position overlapping the first position.

[0159] The protective film has an elastic modulus at the first position smaller than an elastic modulus at the second position in a plan view in the first direction.

[0160] <3> according to <1> or <2> The elastic wave device, wherein:

[0161] The elastic wave device further includes an input terminal, an output terminal, a series arm connecting the input terminal and the output terminal, and a parallel arm connecting a node of the series arm and a ground.

[0162] The plurality of resonators include a series arm resonator disposed in the series arm and a parallel arm resonator disposed in the parallel arm,

[0163] The first resonator and the second resonator are the series arm resonators.

[0164] <4> according to <1> or <2> The elastic wave device, wherein:

[0165] The elastic wave device further includes an input terminal, an output terminal, a series arm connecting the input terminal and the output terminal, and a parallel arm connecting a node of the series arm and a ground.

[0166] The plurality of resonators include a series arm resonator disposed in the series arm and a parallel arm resonator disposed in the parallel arm,

[0167] The first resonator and the second resonator are the parallel arm resonators.

[0168] <5> according to <1> to <4> The elastic wave device as described in any one of the preceding claims, wherein:

[0169] The piezoelectric layer includes lithium niobate or lithium tantalate.

[0170] <6> according to <5> The elastic wave device, wherein:

[0171] The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3),

[0172] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0173] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2)

[0174] (0°±10°, [180°-30° (1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, arbitrary ψ) …Formula (3).

[0175] <7> according to <1> to <6> The elastic wave device as described in any one of the preceding claims, wherein:

[0176] The functional electrode is an IDT electrode including a first bus bar, a second bus bar facing the first bus bar, a plurality of first electrode fingers connected at one end to the first bus bar, and a plurality of second electrode fingers connected at one end to the first bus bar.

[0177] <8> according to <7> The elastic wave device, wherein:

[0178] When the film thickness of the piezoelectric layer is denoted by d and the center-to-center distance between the adjacent first electrode fingers and the second electrode fingers is denoted by p, d / p is equal to or less than 0.5.

[0179] <9> according to <8> The elastic wave device, wherein:

[0180] The d / p is 0.24 or less.

[0181] <10> according to <7> to <9> The elastic wave device as described in any one of the preceding claims, wherein:

[0182] When an area where the adjacent first electrode fingers and second electrode fingers overlap when viewed in opposite directions is defined as an excitation area, and when a metallization ratio of the first electrode fingers and the second electrode fingers relative to the excitation area is defined as MR, MR≤1.75(d / p)+0.075 is satisfied.

[0183] <11> according to <1> to <10> The elastic wave device as described in any one of the preceding claims, wherein:

[0184] The elastic wave device is configured to utilize thickness shear mode bulk waves.

[0185] <12> A method for manufacturing an elastic wave device, comprising:

[0186] A lamination step of laminating a piezoelectric layer on a supporting member;

[0187] An electrode forming step of forming a functional electrode on the piezoelectric layer;

[0188] a protective film forming step of forming a protective film on the piezoelectric layer on which the functional electrode is formed; and

[0189] a singulation step of singulating the support member after the protective film forming step into individual pieces to form an elastic wave device,

[0190] The piezoelectric layer stacked on the support member in the stacking step has a first position and a second position, the second position being a position where the thickness of the piezoelectric layer is thinner than the thickness of the piezoelectric layer at the first position,

[0191] A first elastic wave device including a piezoelectric layer having the first position and a second elastic wave device including a piezoelectric layer having the second position are adjacent to each other before the singulation step.

[0192] In the protective film forming step, the protective film formed at the first position is formed to have an elastic modulus different from an elastic modulus of the protective film formed at the second position.

[0193] <13> according to <12> The method for manufacturing an elastic wave device, wherein:

[0194] The manufacturing method further includes a film thickness adjusting step of adjusting the film thickness of the protective film.

[0195] <14> according to <13> The method for manufacturing an elastic wave device, wherein:

[0196] In the film thickness adjustment step, the film thickness of the protective film is adjusted by ion milling.

[0197] Description of Reference Numerals

[0198] 1. 1A~1C, 101, 301 Elastic wave device

[0199] 2 Piezoelectric layer

[0200] 2a 1st main surface

[0201] 2b Second main surface

[0202] 2H Through hole

[0203] 3 electrode fingers (1st electrode finger)

[0204] 4 electrode fingers (2nd electrode finger)

[0205] 5 Bus Bar 1

[0206] 6 Bus Bar 2

[0207] 7 Middle Layer

[0208] 7a Opening

[0209] 7S Sacrificial layer

[0210] 8 Support base plate

[0211] 8a Opening

[0212] 9 Space Department

[0213] 14 Protective film

[0214] 80 Supporting member

[0215] 201 Piezoelectric layer

[0216] 201a 1st Main Side

[0217] 201b Second main surface

[0218] 251 Area 1

[0219] 252 Area 2

[0220] 310, 311 reflectors

[0221] C Excitation region (crossover region)

[0222] P1 1st position

[0223] P2 2nd position

[0224] R1 1st resonator

[0225] R2 2nd resonator

[0226] VP1 Fantasy plane.

Claims

1. An elastic wave device comprising a plurality of resonators, The plurality of resonators respectively include: A supporting member having a thickness in a first direction; A piezoelectric layer is arranged in the first direction of the supporting member; A functional electrode is arranged in the first direction of the piezoelectric layer; and a protective film disposed in a first direction of the piezoelectric layer on which the resonator is disposed, The support member has a space portion at a position at which at least a portion overlaps with the functional electrode when viewed from above in the first direction. The plurality of resonators include a first resonator and a second resonator adjacent to the first resonator. The elastic modulus at a first position of the protective film is different from the elastic modulus at a second position different from the first position, The first position overlaps with the space portion of the first resonator when viewed in plan in the first direction. The second position overlaps with a space portion of the second resonator in a plan view in the first direction.

2. The elastic wave device according to claim 1, wherein: When viewed from above in the first direction, the thickness of the piezoelectric layer at a position overlapping the second position is thinner than the thickness of the piezoelectric layer at a position overlapping the first position. The protective film has an elastic modulus at the first position smaller than an elastic modulus at the second position in a plan view in the first direction.

3. The elastic wave device according to claim 1 or 2, wherein: The elastic wave device further includes an input terminal, an output terminal, a series arm connecting the input terminal and the output terminal, and a parallel arm connecting a node of the series arm and a ground. The plurality of resonators include a series arm resonator disposed in the series arm and a parallel arm resonator disposed in the parallel arm, The first resonator and the second resonator are the series arm resonators.

4. The elastic wave device according to claim 1 or 2, wherein: The elastic wave device further includes an input terminal, an output terminal, a series arm connecting the input terminal and the output terminal, and a parallel arm connecting a node of the series arm and a ground. The plurality of resonators include a series arm resonator disposed in the series arm and a parallel arm resonator disposed in the parallel arm, The first resonator and the second resonator are the parallel arm resonators.

5. The elastic wave device according to claim 1, wherein: The piezoelectric layer includes lithium niobate or lithium tantalate.

6. The elastic wave device according to claim 5, wherein: The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3), (0°±10°, 0°~20°, arbitrary ψ) …Formula (1) (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~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).

7. The elastic wave device according to claim 1, wherein: The functional electrode is an IDT electrode including a first bus bar, a second bus bar facing the first bus bar, a plurality of first electrode fingers connected at one end to the first bus bar, and a plurality of second electrode fingers connected at one end to the first bus bar.

8. The elastic wave device according to claim 7, wherein: When the film thickness of the piezoelectric layer is denoted by d and the center-to-center distance between the adjacent first electrode fingers and the second electrode fingers is denoted by p, d / p is equal to or less than 0.

5.

9. The elastic wave device according to claim 8, wherein: The d / p is 0.24 or less.

10. The elastic wave device according to claim 7, wherein: When an area where the adjacent first electrode fingers and second electrode fingers overlap when viewed in opposite directions is defined as an excitation area, and when a metallization ratio of the first electrode fingers and the second electrode fingers relative to the excitation area is defined as MR, MR≤1.75(d / p)+0.075 is satisfied.

11. The elastic wave device according to claim 1, wherein: The elastic wave device is configured to utilize thickness shear mode body waves.

12. A method for manufacturing an elastic wave device, comprising: A lamination step of laminating a piezoelectric layer on a supporting member; An electrode forming step of forming a functional electrode on the piezoelectric layer; a protective film forming step of forming a protective film on the piezoelectric layer on which the functional electrode is formed; as well as a singulation step of singulating the support member after the protective film forming step into individual pieces to form an elastic wave device, The piezoelectric layer stacked on the support member in the stacking step has a first position and a second position, the second position being a position where the thickness of the piezoelectric layer is thinner than the thickness of the piezoelectric layer at the first position, A first elastic wave device including a piezoelectric layer having the first position and a second elastic wave device including a piezoelectric layer having the second position are adjacent to each other before the singulation step. In the protective film forming step, the protective film formed at the first position is formed to have an elastic modulus different from an elastic modulus of the protective film formed at the second position.

13. The method for manufacturing an elastic wave device according to claim 12, wherein: The manufacturing method further includes a film thickness adjusting step of adjusting the film thickness of the protective film.

14. The method for manufacturing an elastic wave device according to claim 13, wherein: In the film thickness adjustment step, the film thickness of the protective film is adjusted by ion milling.

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