WO2023157958A1 - Elastic wave device and method for producing elastic wave device - Google Patents

Abstract

The present invention suppresses cracking of a piezoelectric layer. This elastic wave device comprises: an elastic wave element comprising a piezoelectric layer that is thick in a first direction and has a first main surface and a second main surface, a functional electrode provided to at least one of the first main surface and the second main surface, a bump connected to the functional electrode, and a support member provided to the second main surface side with respect to the piezoelectric layer; and a mounting substrate connected with the elastic wave element via the bump. The support member comprises a support substrate. The support member has a space on the piezoelectric layer side of the support member and a through hole passing through the support substrate. The through hole communicates with the space.

Description

ELASTIC WAVE DEVICE AND METHOD FOR MANUFACTURING ELASTIC WAVE DEVICE

The present disclosure relates to an elastic wave device and a method for manufacturing an elastic wave device.

Patent Document 1 describes an elastic wave device.

JP 2012-257019 A

In the acoustic wave device shown in Patent Document 1, the piezoelectric layer may be provided with a through hole for the purpose of etching a sacrificial layer for forming a space between the support substrate and the piezoelectric layer. In this case, there is a possibility that cracks originating from the through-holes may occur in the piezoelectric layer.

The present disclosure is intended to solve the above-described problems, and aims to suppress the occurrence of cracks in the piezoelectric layer.

An elastic wave device according to one aspect includes a piezoelectric layer having a thickness in a first direction and having a first main surface and a second main surface; an acoustic wave element comprising: a functional electrode provided on at least one of them; a bump connected to the functional electrode; and a support member provided on the second principal surface side with respect to the piezoelectric layer; a mounting substrate connected to the acoustic wave element via a mounting substrate, wherein the support member includes a support substrate, and the support member includes a space portion on the piezoelectric layer side of the support member; and a through hole that penetrates the substrate, and the through hole communicates with the space.

A method of manufacturing an acoustic wave device according to one aspect includes a through-hole forming step of forming a through-hole in a support substrate, a lamination step of laminating a piezoelectric layer on the support substrate, and an electrode formation step of forming a functional electrode on the piezoelectric layer. a bump forming step of forming bumps connected to the functional electrodes; a mounting step of attaching the bumps to a mounting substrate; and a space forming step of forming a space, immediately after the stacking step. A sacrificial layer is laminated between the piezoelectric layer and the support substrate, and a part of the sacrificial layer is exposed in the through hole immediately before the space forming step, In the space forming step, the space is formed by etching the sacrificial layer.

According to the present disclosure, it is possible to suppress the occurrence of cracks in the piezoelectric layer.

1A is a perspective view showing an elastic wave device according to a first embodiment; FIG. FIG. 1B is a plan view showing the electrode structure of the first embodiment. FIG. 2 is a cross-sectional view of a portion along line II-II of FIG. 1A. FIG. 3A is a schematic cross-sectional view for explaining Lamb waves propagating through the piezoelectric layer of the comparative example. FIG. 3B is a schematic cross-sectional view for explaining a thickness-shear primary mode bulk wave propagating through the piezoelectric layer of the first embodiment. FIG. 4 is a schematic cross-sectional view for explaining the amplitude direction of a thickness-shear primary mode bulk wave propagating through the piezoelectric layer of the first embodiment. FIG. 5 is an explanatory diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment. In the elastic wave device of the first embodiment, FIG. 2 is an explanatory diagram showing the relationship between , and the fractional band. FIG. FIG. 7 is a plan view showing an example in which a pair of electrodes are provided in the elastic wave device of the first embodiment. FIG. 8 is a reference diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment. FIG. 9 shows the ratio bandwidth when a large number of elastic wave resonators are configured in the elastic wave device of the first embodiment, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. is an explanatory diagram showing the relationship between. FIG. 10 is an explanatory diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth. FIG. 11 is an explanatory diagram showing a map of the fractional band with respect to the Euler angles (0°, θ, ψ) of LiNbO ₃ when d/p is infinitely close to 0. FIG. FIG. 12 is a partially cutaway perspective view for explaining the elastic wave device according to the embodiment of the present disclosure. FIG. 13 is a schematic cross-sectional view showing an example of the elastic wave device according to the first embodiment. FIG. 14 is a schematic plan view showing an example of the acoustic wave device according to the first embodiment; 15 is a cross-sectional view taken along line XV-XV of FIG. 14. FIG. 16 is a schematic cross-sectional view showing a first modification of the elastic wave device according to the first embodiment; FIG. 17 is a schematic plan view showing a second modification of the elastic wave device according to the first embodiment; FIG. 18A and 18B are schematic cross-sectional views illustrating a through-hole forming process according to the first embodiment. 19A and 19B are schematic cross-sectional views illustrating a bonding process according to the first embodiment. FIG. 20 is a schematic cross-sectional view for explaining the thinning process according to the first embodiment. 21A and 21B are schematic cross-sectional views for explaining the functional electrode forming process according to the first embodiment. 22A and 22B are schematic cross-sectional views illustrating a reinforcing electrode forming process according to the first embodiment. 23A and 23B are schematic cross-sectional views illustrating a bump forming process according to the first embodiment. FIG. 24 is a schematic cross-sectional view for explaining the grooving process according to the first embodiment. FIG. 25 is a schematic cross-sectional view explaining the grinding process according to the first embodiment. 26A and 26B are schematic cross-sectional views illustrating a singulation process according to the first embodiment. 27A and 27B are schematic cross-sectional views illustrating a mounting process according to the first embodiment. 28A and 28B are schematic cross-sectional views illustrating a space forming step according to the first embodiment. FIG. 29 is a schematic cross-sectional view for explaining the packaging process according to the first embodiment. FIG. 30 is a schematic cross-sectional view for explaining the re-singulation process according to the first embodiment. FIG. 31 is a schematic cross-sectional view for explaining a bonding process according to the first modified example of the first embodiment; FIG. 32 is a schematic cross-sectional view explaining a thinning process according to the first modification of the first embodiment. 33A and 33B are schematic cross-sectional views for explaining the functional electrode forming process according to the first modification of the first embodiment. 34A and 34B are schematic cross-sectional views illustrating a step of forming a reinforcing electrode according to the first modification of the first embodiment. FIG. 35 is a schematic cross-sectional view for explaining a bump formation process according to the first modification of the first embodiment; FIG. 36 is a schematic cross-sectional view explaining a grooving process according to the first modification of the first embodiment. FIG. 37 is a schematic cross-sectional view explaining a grinding process according to the first modification of the first embodiment; FIG. 38 is a schematic cross-sectional view explaining a through-hole forming step according to a modification of the first modification.

Below, embodiments of the present disclosure will be described in detail based on the drawings. Note that the present disclosure is not limited by this embodiment. It should be noted that each embodiment described in the present disclosure is exemplary, and between different embodiments, the configuration can be partially replaced or combined. A description of matters common to the embodiment will be omitted, and only different points will be described. In particular, similar actions and effects due to similar configurations will not be mentioned sequentially for each embodiment.

(First embodiment)
1A is a perspective view showing an elastic wave device according to a first embodiment; FIG. FIG. 1B is a plan view showing the electrode structure of the first embodiment.

The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 made of LiNbO ₃ . The piezoelectric layer 2 may consist of LiTaO ₃ . The cut angle of LiNbO ₃ and LiTaO ₃ is Z-cut in the first embodiment. The cut angles of LiNbO ₃ and LiTaO ₃ may be rotated Y-cut or X-cut. Preferably, the Y-propagation and X-propagation ±30° propagation orientations are preferred.

Although the thickness of the piezoelectric layer 2 is not particularly limited, it is preferably 50 nm or more and 1000 nm or less in order to effectively excite the thickness shear primary mode.

The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b facing each other in the Z direction. Electrode fingers 3 and 4 are provided on the first main surface 2a.

Here, the electrode finger 3 is an example of the "first electrode finger" and the electrode finger 4 is an example of the "second electrode finger". In FIGS. 1A and 1B , the multiple electrode fingers 3 are multiple “first electrode fingers” connected to the first busbar electrodes 5 . The multiple electrode fingers 4 are multiple “second electrode fingers” connected to the second busbar electrodes 6 . The plurality of electrode fingers 3 and the plurality of electrode fingers 4 are interdigitated with each other. Thus, an IDT (Interdigital Transducer) electrode including electrode fingers 3 , electrode fingers 4 , first busbar electrodes 5 , and second busbar electrodes 6 is configured.

The electrode fingers 3 and 4 have a rectangular shape and a length direction. The electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in a direction perpendicular to the length direction. The length direction of the electrode fingers 3 and 4 and the direction perpendicular to the length direction of the electrode fingers 3 and 4 are directions that intersect the thickness direction of the piezoelectric layer 2 . Therefore, it can be said that the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2 . In the following description, the thickness direction of the piezoelectric layer 2 is defined as the Z direction (or first direction), the length direction of the electrode fingers 3 and 4 is defined as the Y direction (or second direction), and the electrode fingers 3 and electrode fingers 4 may be described as the X direction (or the third direction).

Further, the length direction of the electrode fingers 3 and 4 may be interchanged with the direction orthogonal to the length direction of the electrode fingers 3 and 4 shown in FIGS. 1A and 1B. That is, in FIGS. 1A and 1B, the electrode fingers 3 and 4 may extend in the direction in which the first busbar electrodes 5 and the second busbar electrodes 6 extend. In that case, the first busbar electrode 5 and the second busbar electrode 6 extend in the direction in which the electrode fingers 3 and 4 extend in FIGS. 1A and 1B. A pair of structures in which the electrode fingers 3 connected to one potential and the electrode fingers 4 connected to the other potential are adjacent to each other are arranged in a direction perpendicular to the length direction of the electrode fingers 3 and 4. Multiple pairs are provided.

Here, the electrode finger 3 and the electrode finger 4 are adjacent to each other, not when the electrode finger 3 and the electrode finger 4 are arranged so as to be in direct contact, but when the electrode finger 3 and the electrode finger 4 are arranged with a gap therebetween. It refers to the case where the When the electrode finger 3 and the electrode finger 4 are adjacent to each other, there are electrodes connected to the hot electrode and the ground electrode, including other electrode fingers 3 and 4, between the electrode finger 3 and the electrode finger 4. is not placed. The logarithms need not be integer pairs, but may be 1.5 pairs, 2.5 pairs, and so on.

The center-to-center distance, that is, the pitch, between the electrode fingers 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Further, the center-to-center distance between the electrode fingers 3 and 4 means the center of the width dimension of the electrode fingers 3 in the direction orthogonal to the length direction of the electrode fingers 3 and the distance orthogonal to the length direction of the electrode fingers 4 . It is the distance connecting the center of the width dimension of the electrode finger 4 in the direction of

Furthermore, when at least one of the electrode fingers 3 and 4 is plural (when there are 1.5 or more pairs of electrodes when the electrode fingers 3 and 4 are paired as a pair of electrode pairs), the electrode fingers 3. The center-to-center distance of the electrode fingers 4 refers to the average value of the center-to-center distances of adjacent electrode fingers 3 and electrode fingers 4 among 1.5 or more pairs of electrode fingers 3 and electrode fingers 4 .

Also, the width of the electrode fingers 3 and 4, that is, the dimension in the facing direction of the electrode fingers 3 and 4 is preferably in the range of 150 nm or more and 1000 nm or less. Note that the center-to-center distance between the electrode fingers 3 and 4 is the distance between the center of the dimension (width dimension) of the electrode finger 3 in the direction perpendicular to the length direction of the electrode finger 3 and the length of the electrode finger 4. It is the distance connecting the center of the dimension (width dimension) of the electrode finger 4 in the direction orthogonal to the direction.

Also, in the first embodiment, since the Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrode fingers 3 and 4 is the direction orthogonal to the polarization direction of the piezoelectric layer 2 . This is not the case when a piezoelectric material with a different cut angle is used as the piezoelectric layer 2 . Here, "perpendicular" is not limited to being strictly perpendicular, but substantially perpendicular (the angle formed by the direction perpendicular to the length direction of the electrode fingers 3 and electrode fingers 4 and the polarization direction is, for example, 90° ± 10°).

A support substrate 8 is laminated on the second main surface 2b side of the piezoelectric layer 2 with an intermediate layer 7 interposed therebetween. The intermediate layer 7 and the support substrate 8 have a frame shape and, as shown in FIG. 2, openings 7a and 8a. A space (air gap) 9 is thereby formed.

The space 9 is provided so as not to disturb the vibration of the excitation region C of the piezoelectric layer 2 . Therefore, the supporting substrate 8 is laminated on the second main surface 2b with the intermediate layer 7 interposed therebetween at a position not overlapping the portion where at least one pair of electrode fingers 3 and 4 are provided. Note that the intermediate layer 7 may not be provided. Therefore, the support substrate 8 can be directly or indirectly laminated to the second main surface 2b of the piezoelectric layer 2 .

The intermediate layer 7 is made of silicon oxide. However, the intermediate layer 7 can be formed of an appropriate insulating material other than silicon oxide, such as silicon nitride and alumina.

The support substrate 8 is made of Si. The plane orientation of the surface of Si on the piezoelectric layer 2 side may be (100), (110), or (111). Preferably, high-resistance Si having a resistivity of 4 kΩ or more is desirable. However, the support substrate 8 can also be constructed using an appropriate insulating material or semiconductor material. Materials for the support substrate 8 include, for example, aluminum oxide, lithium tantalate, lithium niobate, piezoelectric materials such as crystal, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, and steer. Various ceramics such as tight and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.

The plurality of electrode fingers 3, electrode fingers 4, first busbar electrodes 5, and second busbar electrodes 6 are made of appropriate metals or alloys such as Al and AlCu alloys. In the first embodiment, the electrode fingers 3, the electrode fingers 4, the first busbar electrodes 5, and the second busbar electrodes 6 have a structure in which an Al film is laminated on a Ti film. Note that an adhesion layer other than the Ti film may be used.

When driving, an alternating voltage is applied between the multiple electrode fingers 3 and the multiple electrode fingers 4 . More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 6 . As a result, it is possible to obtain resonance characteristics using a thickness-shear primary mode bulk wave excited in the piezoelectric layer 2 .

Further, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is d, and the center-to-center distance between any one of the plurality of pairs of electrode fingers 3 and 4 adjacent to each other is p, d/p is set to 0.5 or less. As a result, the thickness-shear primary mode bulk wave is effectively excited, and good resonance characteristics can be obtained. More preferably, d/p is 0.24 or less, in which case even better resonance characteristics can be obtained.

When at least one of the electrode fingers 3 and the electrode fingers 4 is plural as in the first embodiment, that is, when the electrode fingers 3 and the electrode fingers 4 form a pair of electrodes, the electrode fingers 3 and the electrode fingers When there are 1.5 pairs or more of 4, the center-to-center distance between the adjacent electrode fingers 3 and 4 is the average distance between the center-to-center distances between the adjacent electrode fingers 3 and 4 .

Since the acoustic wave device 1 of the first embodiment has the above configuration, even if the logarithms of the electrode fingers 3 and 4 are reduced in an attempt to reduce the size, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides, and the propagation loss is small. The reason why the above reflector is not required is that the bulk wave of the thickness-shlip primary mode is used.

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

FIG. 3A shows an acoustic wave device as described in Patent Document 1, in which Lamb waves propagate through the piezoelectric layer. As shown in FIG. 3A, waves propagate through the piezoelectric layer 201 as indicated by arrows. Here, the piezoelectric layer 201 has a first principal surface 201a and a second principal surface 201b, and the thickness direction connecting the first principal surface 201a and the second principal surface 201b is the Z direction. . The X direction is the direction in which the electrode fingers 3 and 4 of the IDT electrodes are aligned. As shown in FIG. 3A, in the Lamb wave, the wave propagates in the X direction as shown. Since it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates in the X direction, so reflectors are arranged on both sides to obtain resonance characteristics. Therefore, a wave propagation loss occurs, and the Q value decreases when miniaturization is attempted, that is, when the number of logarithms of the electrode fingers 3 and 4 is decreased.

On the other hand, as shown in FIG. 3B, in the acoustic wave device of the first embodiment, since the vibration displacement is in the thickness sliding direction, the wave is generated between the first main surface 2a and the second main surface 2a of the piezoelectric layer 2. It propagates almost in the direction connecting the surface 2b, that is, in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Further, since resonance characteristics are obtained by propagating waves in the Z direction, no reflector is required. Therefore, no propagation loss occurs when propagating to the reflector. Therefore, even if the number of electrode pairs consisting of the electrode fingers 3 and 4 is reduced in an attempt to promote miniaturization, the Q value is unlikely to decrease.

As shown in FIG. 4, the amplitude direction of the bulk wave of the primary thickness-shear mode is the first region 251 included in the excitation region C (see FIG. 1B) of the piezoelectric layer 2 and the first region 251 included in the excitation region C (see FIG. 1B). 2 area 252 is reversed. FIG. 4 schematically shows bulk waves when a voltage is applied between the electrode fingers 3 so that the electrode fingers 4 have a higher potential than the electrode fingers 3 . The first region 251 is a region of the excitation region C between the virtual plane VP1 that is perpendicular to the thickness direction of the piezoelectric layer 2 and bisects the piezoelectric layer 2 and the first main surface 2a. The second region 252 is a region of the excitation region C between the virtual plane VP1 and the second main surface 2b.

In the elastic wave device 1, at least one pair of electrodes consisting of the electrode fingers 3 and 4 is arranged. It is not always necessary to have a plurality of pairs of electrode pairs. That is, it is sufficient that at least one pair of electrodes is provided.

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

FIG. 5 is an explanatory diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment. The design parameters of the acoustic wave device 1 that obtained the resonance characteristics shown in FIG. 5 are as follows.

Piezoelectric layer 2: _LiNbO3 with Euler angles (0°, 0°, 90°)
Thickness of piezoelectric layer 2: 400 nm

Length of excitation region C (see FIG. 1B): 40 μm
Number of electrode pairs consisting of electrode fingers 3 and 4: 21 pairs Center-to-center distance (pitch) between electrode fingers 3 and 4: 3 μm
Width of electrode fingers 3 and 4: 500 nm
d/p: 0.133

　Middle layer 7: Silicon oxide film with a thickness of 1 μm

Support substrate 8: Si

The excitation region C (see FIG. 1B) is a region where the electrode fingers 3 and 4 overlap when viewed in the X direction perpendicular to the length direction of the electrode fingers 3 and 4. . The length of the excitation region C is the dimension along the length direction of the electrode fingers 3 and 4 of the excitation region C. As shown in FIG. Here, the excitation region C is an example of the "intersection region".

In the first embodiment, the center-to-center distances of the electrode pairs consisting of the electrode fingers 3 and 4 are all made equal in the plurality of pairs. That is, the electrode fingers 3 and the electrode fingers 4 are arranged at equal pitches.

As is clear from FIG. 5, good resonance characteristics with a specific bandwidth of 12.5% are obtained in spite of having no reflector.

By the way, when the thickness of the piezoelectric layer 2 is d, and the center-to-center distance between the electrode fingers 3 and 4 is p, in the first embodiment, d/p is 0.5 or less, more preferably 0. .24 or less. This will be explained with reference to FIG.

A plurality of elastic wave devices were obtained by changing d/2p in the same manner as the elastic wave device that obtained the resonance characteristics shown in FIG. In the elastic wave device of the first embodiment, FIG. It is an explanatory view showing the relationship with the fractional bandwidth as.

As shown in FIG. 6, when d/2p exceeds 0.25, that is, when d/p>0.5, even if d/p is adjusted, the fractional bandwidth is less than 5%. On the other hand, when d/2p≦0.25, that is, when d/p≦0.5, the specific bandwidth can be increased to 5% or more by changing d/p within that range. , that is, a resonator having a high coupling coefficient can be constructed. Further, when d/2p is 0.12 or less, that is, when d/p is 0.24 or less, the specific bandwidth can be increased to 7% or more. In addition, by adjusting d/p within this range, a resonator with a wider specific band can be obtained, and a resonator with a higher coupling coefficient can be realized. Therefore, by setting d/p to 0.5 or less, it is possible to construct a resonator having a high coupling coefficient using the thickness-shear primary mode bulk wave.

It should be noted that at least one pair of electrodes may be one pair, and the above p is the center-to-center distance between adjacent electrode fingers 3 and 4 in the case of one pair of electrodes. In the case of 1.5 pairs or more of electrodes, the average distance between the centers of the adjacent electrode fingers 3 and 4 should be p.

Also, for the thickness d of the piezoelectric layer 2, if the piezoelectric layer 2 has variations in thickness, a value obtained by averaging the thickness may be adopted.

FIG. 7 is a plan view showing an example in which a pair of electrodes are provided in the elastic wave device of the first embodiment. In elastic wave device 101 , a pair of electrodes having electrode fingers 3 and 4 are provided on first main surface 2 a of piezoelectric layer 2 . Note that K in FIG. 7 is the intersection width. As described above, in the elastic wave device of the present disclosure, the number of pairs of electrodes may be one. Even in this case, if the above d/p is 0.5 or less, it is possible to effectively excite the bulk wave in the primary mode of thickness shear.

In the elastic wave device 1, preferably, the excitation region is an overlapping region of the plurality of electrode fingers 3 and 4 when viewed in the direction in which any adjacent electrode fingers 3 and 4 are facing each other. It is desirable that the metallization ratio MR of the adjacent electrode fingers 3 and 4 with respect to the region C satisfies MR≦1.75(d/p)+0.075. In that case, spurious can be effectively reduced. This will be described with reference to FIGS. 8 and 9. FIG.

FIG. 8 is a reference diagram showing an example of resonance characteristics of the elastic wave device of the first embodiment. A spurious signal indicated by an arrow B appears between the resonance frequency and the anti-resonance frequency. Note that d/p=0.08 and the Euler angles of LiNbO ₃ (0°, 0°, 90°). Also, the metallization ratio MR was set to 0.35.

The metallization ratio MR will be explained with reference to FIG. 1B. In the electrode structure of FIG. 1B, when focusing on the pair of electrode fingers 3 and 4, it is assumed that only the pair of electrode fingers 3 and 4 are provided. In this case, the excitation region C is the portion surrounded by the dashed-dotted line. The excitation region C refers to the electrode finger that overlaps the electrode finger 4 when the electrode finger 3 and the electrode finger 4 are viewed in a direction orthogonal to the length direction of the electrode finger 3 and the electrode finger 4, that is, in the opposing direction. 3, a region of the electrode finger 4 overlapping the electrode finger 3, and a region between the electrode finger 3 and the electrode finger 4 where the electrode finger 3 and the electrode finger 4 overlap. The area of the electrode fingers 3 and 4 in the excitation region C with respect to the area of the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallization portion to the area of the excitation region C.

When a plurality of pairs of electrode fingers 3 and 4 are provided, the ratio of the metallization portion included in the entire excitation region C to the total area of the excitation region C should be MR.

FIG. 9 shows the ratio bandwidth when a large number of elastic wave resonators are configured in the elastic wave device of the first embodiment, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. is an explanatory diagram showing the relationship between. The ratio band was adjusted by changing the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4 . FIG. 9 shows the results when the piezoelectric layer 2 made of Z-cut LiNbO ₃ is used, but the same tendency is obtained when the piezoelectric layer 2 with other cut angles is used.

In the area surrounded by ellipse J in FIG. 9, the spurious is as large as 1.0. As is clear from FIG. 9, when the fractional band exceeds 0.17, that is, when it exceeds 17%, a large spurious with a spurious level of 1 or more changes the parameters constituting the fractional band, even if the passband appear within. That is, as in the resonance characteristics shown in FIG. 8, a large spurious component indicated by arrow B appears within the band. Therefore, the specific bandwidth is preferably 17% or less. In this case, by adjusting the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4, the spurious response can be reduced.

FIG. 10 is an explanatory diagram showing the relationship between d/2p, metallization ratio MR, and fractional bandwidth. In the elastic wave device 1 of the first embodiment, various elastic wave devices 1 with different d/2p and MR were configured, and the fractional bandwidth was measured. The hatched portion on the right side of the dashed line D in FIG. 10 is the area where the fractional bandwidth is 17% or less. The boundary between the hatched area and the non-hatched area is expressed by MR=3.5(d/2p)+0.075. That is, MR=1.75(d/p)+0.075. Therefore, preferably MR≤1.75(d/p)+0.075. In that case, it is easy to set the fractional bandwidth to 17% or less. More preferably, it is the area on the right side of MR=3.5(d/2p)+0.05 indicated by the dashed-dotted line D1 in FIG. That is, if MR≤1.75(d/p)+0.05, the fractional bandwidth can be reliably reduced to 17% or less.

FIG. 11 is an explanatory diagram showing a map of the fractional band with respect to the Euler angles (0°, θ, ψ) of LiNbO ₃ when d/p is infinitely close to 0. FIG. A hatched portion in FIG. 11 is a region where a fractional bandwidth of at least 5% or more is obtained. When the range of the area is approximated, it becomes the range represented by the following formulas (1), (2) and (3).

(0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ² /900) ^1/2 ) or (0°±10°, 20° to 80°, {180 °-60° (1-(θ-50) ² /900) ^1/2 } ~ 180°) Equation (2)
(0°±10°, {180°−30°(1−(ψ−90) ² /8100) ^1/2 } to 180°, arbitrary ψ) Equation (3)

Therefore, in the case of the Euler angle range of formula (1), formula (2), or formula (3), the fractional band can be sufficiently widened, which is preferable.

FIG. 12 is a partially cutaway perspective view for explaining the elastic wave device according to the embodiment of the present disclosure. In FIG. 12, the outer peripheral edge of the space 9 is indicated by a dashed line. The elastic wave device of the present disclosure may utilize plate waves. In this case, the elastic wave device 301 has reflectors 310 and 311 as shown in FIG. Reflectors 310 and 311 are provided on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the acoustic wave propagation direction. In the elastic wave device 301, a Lamb wave as a plate wave is excited by applying an AC electric field to the electrode fingers 3 and 4 on the space 9. FIG. At this time, since the reflectors 310 and 311 are provided on both sides, it is possible to obtain resonance characteristics due to Lamb waves as plate waves.

As described above, the elastic wave devices 1 and 101 use bulk waves in the primary mode of thickness shear. In the elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes, the thickness of the piezoelectric layer 2 is d, and the center of the first electrode finger 3 and the second electrode finger 4 is d/p is set to 0.5 or less, where p is the distance between them. As a result, the Q value can be increased even if the elastic wave device is miniaturized.

In the elastic wave devices 1 and 101, the piezoelectric layer 2 is made of lithium niobate or lithium tantalate. The first principal surface 2a or the second principal surface 2b of the piezoelectric layer 2 has first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2. It is desirable to cover the finger 3 and the second electrode finger 4 with a protective film.

FIG. 13 is a schematic cross-sectional view showing an example of the elastic wave device according to the first embodiment. An elastic wave device 1A according to the first embodiment includes an elastic wave element 10A, a mounting board 40, and a package 60. As shown in FIG.

FIG. 14 is a schematic plan view showing an example of the acoustic wave device according to the first embodiment. 15 is a cross-sectional view taken along line XV-XV of FIG. 14. FIG. As shown in FIG. 14, the acoustic wave device 10A according to the first embodiment is an acoustic wave device having resonators R1 to R3 parallel to each other. As shown in FIGS. 13 to 15, the acoustic wave device 10A according to the first embodiment includes a piezoelectric layer 2, functional electrodes 30, wiring electrodes 35, reinforcing electrodes 14, bumps 50, and supporting members 80. Prepare.

The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b. In the following description, the direction from the first principal surface 2a to the second principal surface 2b of the piezoelectric layer 2 is upward, and the direction from the second principal surface 2b to the first principal surface 2a of the piezoelectric layer 2 is downward. described as.

The functional electrode 30 is an IDT electrode having first electrode fingers 3 , second electrode fingers 4 , first busbar electrodes 5 , and second busbar electrodes 6 . The functional electrode 30 is provided on at least one of the first main surface 2 a and the second main surface 2 b of the piezoelectric layer 2 . In the example of FIG. 13, the functional electrode 30 is provided on the first main surface 2a of the piezoelectric layer 2. In the example of FIG.

The wiring electrode 35 is a wiring electrically connected to the functional electrode 30 . In the first embodiment, the wiring electrode 35 is provided on the first main surface 2a of the piezoelectric layer 2. As shown in FIG. The material of the wiring electrodes 35 may be the same as the material of the functional electrodes 30 .

The reinforcing electrode 14 is provided on the side opposite to the support substrate 8 side in the Z direction with respect to the piezoelectric layer 2 . The reinforcing electrodes 14 are electrically connected to the functional electrodes 30 . In the first embodiment, the reinforcing electrode 14 is laminated on the surface of the busbar electrodes 5 and 6 of the functional electrode 30 or the surface of the wiring electrode 35 opposite to the piezoelectric layer 2 side. The reinforcing electrode 14 is made of Cu or Al, for example. As a result, the piezoelectric layer 2 is reinforced by the reinforcing electrode 14, so damage to the piezoelectric layer 2 can be suppressed.

The bump 50 is an extraction electrode of the acoustic wave device 10A. The bump 50 is provided on the side opposite to the support substrate 8 in the Z direction with respect to the piezoelectric layer 2 . In the first embodiment, the bumps 50 are laminated on the surface of the reinforcing electrode 14 opposite to the piezoelectric layer 2 side. The bumps 50 are made of Au or solder, for example. Thereby, the bumps 50 are electrically connected to the functional electrodes 30 .

The resonators R1 to R3 are resonators including at least a pair of electrode fingers 3,4. Each of the resonators R1 to R3 has the functional electrode 30, and the support member 80 and the piezoelectric layer 2 that overlap at least a part of the functional electrode 30 when viewed from above in the Z direction. In the example of FIG. 14, the resonators R1 to R3 are parallel resonators and share the busbar electrodes 5,6.

The support member 80 is provided on the second principal surface 2b side with respect to the piezoelectric layer 2 . Support member 80 includes intermediate layer 7 and support substrate 8 . The intermediate layer 7 is provided on the piezoelectric layer 2 side with respect to the support substrate 8 . The support member 80 has a first space portion 91 and a through hole 8H.

The first space 91 is a space on the piezoelectric layer 2 side of the support member 80 . In the first embodiment, the first space 91 is a space in the intermediate layer 7 . The first space portion 91 is positioned so that at least a portion of the first space portion 91 overlaps with the functional electrode 30 in plan view in the Z direction. In the example of FIG. 13, the first space 91 penetrates the intermediate layer 7 in the Z direction. That is, the first space portion 91 is a space between the piezoelectric layer 2 and the support substrate 8 . The first space portion 91 is not limited to penetrating the intermediate layer 7 in the Z direction, and may be a space on the piezoelectric layer 2 side of the intermediate layer 7 .

In the first embodiment, the first space portion 91 has a plurality of resonator space portions 91a and a plurality of lead portions 91b. The resonator space portion 91a is a space for not interfering with the vibration of the excitation regions of the resonators R1 to R3. The resonator space portion 91a is an example of a "functional portion". The resonator space portions 91a are provided at positions overlapping the excitation regions C of the resonators R1 to R3 when viewed in the Z direction. The lead-out portion 91b is a space that communicates with the resonator space portion 91a. The drawer portion 91b is an example of a “non-functional portion”. The lead-out portion 91b is provided at a position that does not overlap the excitation regions C of the resonators R1 to R3 when viewed in the Z direction. At least a portion of the lead portion 91b is provided so as to overlap the reinforcing electrode 14 in plan view in the Z direction. In the example of FIG. 14, one resonator space portion 91a communicates with two lead portions 91b. Here, in the resonator space portion 91a, the portions where the two lead portions 91b are communicated face each other in the direction perpendicular to the Z direction. Also, one lead-out portion 91b communicates with one or two resonator space portions 91a. Therefore, the plurality of resonator space portions 91a communicate with each other through the lead portions 91b. As a result, the inflow and outflow paths of the etchant for dissolving the sacrificial layer 7S become linear between the through holes 8H in the space forming step in the method of manufacturing the elastic wave device 1A, which will be described later. and discharge can be facilitated.

The through-hole 8H is a hole penetrating through the support substrate 8 . In the first embodiment, a plurality of through holes 8H are provided. Further, when viewed in plan in the Z direction, the area of the region overlapping the through hole 8H is smaller than the area of the region overlapping the first space portion 91 . This can prevent the piezoelectric layer 2 from being damaged due to the formation of the through hole 8H.

At least a part of the through-hole 8H overlaps with the first space 91 when viewed in plan in the Z direction. The through hole 8H is provided at a position that does not overlap with the resonator space 91a when viewed in plan in the Z direction. In the example of FIG. 14, the through hole 8H overlaps with the lead portion 91b. In the first embodiment, the through-hole 8H is positioned so that at least a portion of the through-hole 8H overlaps the reinforcing electrode 14 in a plan view in the Z direction. In the example of FIG. 14, the through-hole 8H is positioned so as to overlap the reinforcing electrode 14 . In other words, the through hole 8H overlaps the portion of the piezoelectric layer 2 that overlaps the reinforcing electrode 14 when viewed in plan in the Z direction. This can suppress the occurrence of cracks in the piezoelectric layer 2 due to the through holes 8H.

The through hole 8H communicates with the first space 91. In the first embodiment, the through hole 8H communicates with the lead portion 91b at the end on the piezoelectric layer 2 side. That is, the plurality of through holes 8H communicate with the first space portion 91. As shown in FIG. Therefore, in the example of FIG. 14, the through hole 8H communicates with the plurality of resonator space portions 91a through the lead portions 91b. As a result, the through hole 8H can be used as a hole (etching hole) for injecting and discharging an etchant in a space forming step, which will be described later. can be formed, and the occurrence of cracks in the piezoelectric layer 2 can be suppressed.

The mounting board 40 is a board on which the acoustic wave element 10A is mounted. The mounting substrate 40 is provided on the opposite side of the piezoelectric layer 2 from the support substrate 8 in the Z direction of the acoustic wave element 10A. The mounting substrate 40 includes a substrate 41 and substrate wiring 42 . The substrate wiring 42 is wiring provided on one main surface of the substrate 41 . The substrate wiring 42 is electrically connected to the bumps 50 . Thereby, the mounting board 40 is electrically connected to the functional electrode 30 .

The package 60 is a package that accommodates the acoustic wave element 10A inside. As shown in FIG. 13, the package 60 covers the end of the through-hole 8H in the Z direction opposite to the piezoelectric layer 2 . As a result, the end of the through hole 8H opposite to the piezoelectric layer 2 is supported by the package 60, so that damage to the support member 80 starting from the through hole 8H can be suppressed. As shown in FIG. 13, the package 60 covers the end of the through hole 8H in the Z direction opposite to the piezoelectric layer 2 so as to be liquid-tight. As a result, the through hole 8H and the first space 91 are liquid-tight, so that deterioration of the elastic wave device due to moisture in the air can be suppressed. In the example of FIG. 13, the shape of the package 60 is a rectangular parallelepiped box shape lacking one surface, and one surface in the Z direction is an opening.

A second space 92 is provided inside the package 60 and the mounting substrate 40 . The second space 92 is a space between the first main surface 2a of the piezoelectric layer 2 and the mounting board 40 in the Z direction. More specifically, the second space 92 is surrounded by the package 60, the surface of the piezoelectric layer 2 opposite to the support substrate 8 (first main surface 2a), and the surface of the mounting substrate 40 on the piezoelectric layer 2 side. It is a space with In the first embodiment, the package 60 covers the side surface of the acoustic wave element 10A, that is, the surface in the direction crossing the Z direction. Therefore, the second space 92 is liquid-tight. In other words, the package 60 and the mounting substrate 40 are joined so that the inside is liquid-tight. As a result, damage to the functional electrode 30 due to moisture in the air or the like can be suppressed.

The elastic wave device according to the first embodiment is not limited to the elastic wave device 1A shown in FIGS. 13 to 15, and may be modifications described below. In addition, about the same structure as FIG. 13, the code|symbol is attached and description is abbreviate|omitted.

FIG. 16 is a schematic cross-sectional view showing a first modified example of the elastic wave device according to the first embodiment. As shown in FIG. 16, in an elastic wave device 1B according to the first modified example, an elastic wave element 10B includes a functional electrode 30A provided on the second main surface 2b of the piezoelectric layer 2. As shown in FIG. In the example of FIG. 16, the functional electrode 30A according to the first modified example is connected to the wiring electrode 35A penetrating the piezoelectric layer 2, thereby electrically connecting the functional electrode 30A and the reinforcing electrode 14 together. In the example of FIG. 16, the reinforcing electrode 14 is provided directly on the first main surface 2a of the piezoelectric layer 2. In the example of FIG.

FIG. 17 is a schematic plan view showing a second modification of the elastic wave device according to the first embodiment. As shown in FIG. 17, in an elastic wave device 1C according to the second modification, an elastic wave element 10C includes functional electrodes 30 provided on the second main surface 2b and and a functional electrode 30A provided. In the example of FIG. 17, functional electrodes 30 and 30A according to the second modification are connected to wiring electrodes 35 and 35A, respectively. Thereby, the functional electrodes 30 and 30A and the reinforcing electrode 14 are electrically connected.

As described above, the elastic wave device 1A according to the first embodiment has a thickness in the first direction (Z direction) and the piezoelectric layer 2 having the first main surface 2a and the second main surface 2b. a functional electrode 30 provided on at least one of the first principal surface 2a and the second principal surface 2b; a bump 50 connected to the functional electrode 30; and a mounting substrate 40 connected to the acoustic wave element 10A via the bumps 50. The support member 80 includes a support substrate 8 , and the support member 80 has a space portion (first space portion 91 ) on the piezoelectric layer 2 side of the support member 80 and a through hole 8</b>H passing through the support substrate 8 . There is, and the through hole 8H communicates with the space.

As a result, the through holes 8H can be used as holes (etching holes) for injecting and discharging an etchant in manufacturing the elastic wave device 1A. The occurrence of cracks in the piezoelectric layer 2 can be suppressed.

As a desirable aspect, it further includes a package 60 that accommodates the acoustic wave device 10A. The package 60 covers the end of the through hole 8H opposite to the piezoelectric layer 2 . As a result, the end of the through hole 8H opposite to the piezoelectric layer 2 is supported by the package 60, so that damage to the support member 80 starting from the through hole 8H can be suppressed.

As a desirable aspect, the support member 80 further includes an intermediate layer 7 provided on the piezoelectric layer 2 side of the support substrate 8 . The space is in intermediate layer 7 . Thereby, the frequency temperature characteristic of the elastic wave device can be improved.

Also, the through hole 8H may at least partially overlap with the space when viewed in plan in the first direction. Even in this case, the occurrence of cracks in the piezoelectric layer 2 can be suppressed.

As a desirable aspect, when viewed in plan in the first direction, the area of the region overlapping the space is smaller than the area of the region overlapping the through hole 8H. This can prevent the piezoelectric layer 2 from being damaged due to the formation of the through hole 8H.

Also, a plurality of through-holes 8H may be provided, and the space may communicate with at least two through-holes 8H. Even in this case, the occurrence of cracks in the piezoelectric layer 2 can be suppressed.

Preferably, the functional electrode 30 includes a plurality of first electrode fingers 3 extending in a second direction (Y direction) perpendicular to the first direction and a third direction (X direction) perpendicular to the first and second directions. and a plurality of second electrode fingers 4 facing any one of the plurality of first electrode fingers 3 and extending in the second direction, and at least a portion of the functional electrode 30 is a space portion when viewed in plan in the first direction It is provided so as to overlap with the Thereby, the electrode fingers 3 and 4 can vibrate the piezoelectric layer 2 satisfactorily.

As a desirable mode, the acoustic wave element 10A further includes a reinforcing electrode 14 provided between the piezoelectric layer 2 and the bump 50, and the through hole 8H has at least a part thereof as the reinforcing electrode 14 when viewed in plan in the first direction. provided so as to overlap. This can suppress the occurrence of cracks in the piezoelectric layer 2 due to the through holes 8H.

As a desirable mode, when the region where the adjacent first electrode fingers 3 and the second electrode fingers 4 overlap when viewed in the direction in which they face each other is defined as an excitation region C, the space is arranged in the first direction in a plan view. and a functional portion (resonator space portion 91a) that overlaps with the excitation region and a non-functional portion (drawer portion 91b) that does not overlap with the excitation region C. It is provided at a position that does not overlap with the functional portion, and is provided so that at least a portion of the non-functional portion overlaps with the reinforcing electrode 14 when viewed in plan in the first direction. As a result, it is possible to suppress the functional portion from being damaged by the processing of the support substrate 8 in the below-described penetration forming step, so that the acoustic wave device can be miniaturized without lowering the mechanical strength.

As a desirable aspect, d/p is 0.5 or less, where d is the film thickness of the piezoelectric layer 2 and p is the center-to-center distance between the adjacent first electrode fingers 3 and second electrode fingers 4 . As a result, it is possible to effectively excite the bulk wave of the first-order thickness-shlip mode.

As a preferred embodiment, the piezoelectric layer 2 contains lithium niobate or lithium tantalate. As a result, it is possible to provide an elastic wave device capable of obtaining good resonance characteristics.

As a desirable mode, 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). . In this case, the fractional bandwidth can be reliably set to 17% or less.

(0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ² /900) ^1/2 ) or (0°±10°, 20° to 80°, {180 °-60° (1-(θ-50) ² /900) ^1/2 } ~ 180°) Equation (2)
(0°±10°, {180°−30°(1−(ψ−90) ² /8100) ^1/2 } to 180°, arbitrary ψ) Equation (3)

As a desirable aspect, it is configured to be able to use bulk waves in the thickness-shlip mode. As a result, it is possible to provide an elastic wave device with a high coupling coefficient and good resonance characteristics.

As a desirable mode, d/p is 0.24 or less, where d is the film thickness of the piezoelectric layer and p is the center-to-center distance between the adjacent first electrode fingers 3 and second electrode fingers 4 . This makes it possible to more effectively excite the bulk wave of the first-order thickness-shlip mode.

As a desirable mode, when the excitation region is the region where the adjacent first electrode fingers and the second electrode fingers overlap each other when viewed in the direction in which they face each other, the plurality of first electrode fingers 3 and the plurality of second electrode fingers with respect to the excitation region. When the metallization ratio of the two electrode fingers 4 is MR, MR≦1.75(d/p)+0.075 is satisfied. This can effectively reduce spurious.

As a desirable aspect, it is configured so that plate waves can be used. This can effectively reduce spurious.

An example of the method for manufacturing the elastic wave device according to the first embodiment will be described below with reference to the drawings. A method for manufacturing an acoustic wave device according to the first embodiment includes a through-hole forming step, a laminating step, a functional electrode forming step, a reinforcing electrode forming step, a bump forming step, a grooving step, a grinding step, It has a singulation process, a mounting process, a space forming process, a packaging process, and a re-singulation process. In the first embodiment, the stacking process includes a bonding process and a thinning process.

FIG. 18 is a schematic cross-sectional view for explaining the through-hole forming process according to the first embodiment. As shown in FIG. 18 , the through-hole forming step is a step of forming through-holes 8H in the support substrate 8 . Here, the support substrate 8 before the through-hole forming process is a silicon wafer. In the first embodiment, the through holes 8H are formed by perforating the support substrate 8 by deep etching such as reactive ion etching. Here, the perforation of the support substrate 8 is performed so that the length in the Z direction of the through holes 8H is equal to or greater than the thickness of the support substrate 8 in the singulation process described later.

FIG. 19 is a schematic cross-sectional view for explaining the bonding process according to the first embodiment. As shown in FIG. 19 , the bonding step is a step of bonding the piezoelectric layer 2 to the support substrate 8 . In the first embodiment, the bonding process is performed by forming the sacrificial layer 7S, forming the intermediate layer 7, and bonding the piezoelectric layer 2 and the support substrate 8 together.

The sacrificial layer 7S is formed on a part of the second main surface 2b of the piezoelectric layer 2 by resist patterning. In the example of FIG. 19, the sacrificial layer 7S is formed at a position overlapping the through hole 8H when viewed from above in the Z direction when the piezoelectric layer 2 and the support substrate 8 are bonded together.

The intermediate layer 7 is deposited on the second main surface 2 b of the piezoelectric layer 2 . In the example of FIG. 19, after the intermediate layer 7 is formed on the second main surface 2b of the piezoelectric layer 2 and the sacrificial layer 7S, the intermediate layer 7 is ground so that the surface to be bonded to the support substrate 8 becomes flat. do. In the example of FIG. 19, the sacrificial layer 7S is exposed on the surface on the side to be bonded to the support substrate 8 by grinding the intermediate layer 7. In the example of FIG.

The piezoelectric layer 2 and the support substrate 8 are bonded together by bonding the second main surface 2b of the piezoelectric layer 2 and the surface of the support substrate 8 on which the through holes 8H are formed through the intermediate layer 7. be done.

Through this process, the sacrificial layer 7S is laminated between the piezoelectric layer 2 and the support substrate 8. In addition, the sacrificial layer 7S overlaps the through hole 8H when viewed in plan in the Z direction, and the sacrificial layer 7S is exposed in the through hole 8H. As a result, the sacrificial layer 7S can be etched by injecting an etchant from the through hole 8H in the space forming step described later.

FIG. 20 is a schematic cross-sectional view explaining the thinning process according to the first embodiment. As shown in FIG. 20, the thinning step is a step of thinning the piezoelectric layer 2 . In the first embodiment, the piezoelectric layer 2 is thinned by grinding the main surface of the piezoelectric layer 2 opposite to the second main surface 2b. Thereby, the first main surface 2a of the piezoelectric layer 2 is formed.

FIG. 21 is a schematic cross-sectional view for explaining the functional electrode forming process according to the first embodiment. As shown in FIG. 21, the functional electrode forming step is a step of forming the functional electrodes 30 . Here, the functional electrode 30 is provided so that at least a part thereof overlaps with the sacrificial layer 7S when viewed in plan in the Z direction. In the first embodiment, the functional electrode 30 and the wiring electrode 35 are formed on the first main surface 2a of the piezoelectric layer 2 by lift-off, for example.

FIG. 22 is a schematic cross-sectional view for explaining the reinforcing electrode forming process according to the first embodiment. As shown in FIG. 22 , the reinforcing electrode forming step is a step of forming the reinforcing electrodes 14 . The reinforcing electrode 14 is provided on the side opposite to the support substrate 8 in the Z direction with respect to the piezoelectric layer 2 and at a position overlapping the through hole 8H when viewed from above in the Z direction. In the first embodiment, the reinforcement electrode 14 is laminated on the wiring electrode 35 by patterning, for example. As a result, the reinforcement electrode 14 can reinforce the piezoelectric layer 2 in the portion overlapping the through hole 8H in plan view in the Z direction, thereby suppressing damage to the piezoelectric layer 2 caused by the through hole 8H.

FIG. 23 is a schematic cross-sectional view for explaining the bump forming process according to the first embodiment. As shown in FIG. 23, the bump forming step is a step of forming bumps 50 . The bump 50 is provided on the side opposite to the support substrate 8 in the Z direction with respect to the piezoelectric layer 2 . In the first embodiment, bumps 50 are formed on reinforcing electrodes 14 . Thereby, the bumps 50 and the functional electrodes 30 are electrically connected.

FIG. 24 is a schematic cross-sectional view for explaining the grooving process according to the first embodiment. As shown in FIG. 24, the grooving step is a step of forming grooves G in the support substrate 8 . In the grooving step, so-called half-cut dicing is performed to partially remove the support substrate 8 in the region overlapping the boundary where the acoustic wave elements 10A are singulated in a plan view in the Z direction. In a first embodiment, the support substrate 8 is grooved by etching.

FIG. 25 is a schematic cross-sectional view explaining the grinding process according to the first embodiment. As shown in FIG. 25, the grinding step is a step of grinding the surface of the support substrate 8 on which the through holes 8H are not provided, and is a so-called back grinding. Thereby, the support substrate 8 is thinned.

FIG. 26 is a schematic cross-sectional view for explaining the singulation process according to the first embodiment. As shown in FIG. 26, the singulation step is a step of singulating into acoustic wave devices 10A. In the first embodiment, the surface of the support substrate 8 on which the through holes 8H are not provided is further ground to separate the acoustic wave elements 10A. As a result, the end of the through hole 8H opposite to the piezoelectric layer 2 is opened, and the inside of the through hole 8H becomes an open space. etchant can be injected to etch the sacrificial layer 7S.

FIG. 27 is a schematic cross-sectional view explaining the mounting process according to the first embodiment. As shown in FIG. 27, the mounting process is a process of attaching the acoustic wave element 10A to the mounting board 40. As shown in FIG. In the mounting process, the mounting substrate 40 is provided on the opposite side of the piezoelectric layer 2 from the supporting substrate 8 in the Z direction of the acoustic wave element 10A. In the first embodiment, the acoustic wave device 10A is mounted on the mounting substrate 40 by so-called flip-chip bonding, in which the bumps 50 of the acoustic wave device 10A are bonded to the substrate wiring 42 of the mounting substrate 40 with an adhesive such as resin (not shown). .

28A and 28B are schematic cross-sectional views for explaining the space forming process according to the first embodiment. As shown in FIG. 28, the space forming step is a step of removing the sacrificial layer 7S to form the first space 91. As shown in FIG. Since part of the sacrificial layer 7S is exposed to the through hole 8H immediately before the space forming step, the sacrificial layer 7S is dissolved by injecting an etchant from the through hole 8H in the space forming step. , the first space portion 91 can be formed. In the first embodiment, the inner wall of the through hole 8H is protected with a resist, and the etchant is injected from the end of the through hole 8H opposite to the piezoelectric layer 2 to dissolve the sacrificial layer 7S. After discharging from 8H, the resist on the inner wall of the through hole 8H is removed. Thereby, the first space portion 91 can be formed without forming a through hole in the piezoelectric layer 2 .

FIG. 29 is a schematic cross-sectional view explaining the packaging process according to the first embodiment. As shown in FIG. 29, the packaging process is a process of packaging the acoustic wave device 10A. In the first embodiment, the surface opposite to the piezoelectric layer 2 and the boundary between the acoustic wave elements 10A are laminated to form the package 60, and the end of the through hole 8H opposite to the piezoelectric layer 2 is Cover with package 60 . As a result, the end of the through hole 8H opposite to the piezoelectric layer 2 is supported by the package 60, so that damage to the support member 80 starting from the through hole 8H can be suppressed. In the first embodiment, the end of the through hole 8</b>H on the side opposite to the piezoelectric layer 2 side is closed by being covered with the package 60 . As a result, the through hole 8H and the first space 91 are liquid-tight, so that deterioration of the elastic wave device due to moisture in the air can be suppressed. In the packaging process, the package 60 and the mounting substrate 40 are joined together so that the X-direction and Y-direction surfaces of the acoustic wave device 10A are covered with the package 60, so that the inside of the second space 92 is becomes liquid-tight. As a result, it is possible to prevent the functional electrode 30 from being damaged by moisture in the air or the like.

FIG. 30 is a schematic cross-sectional view explaining the re-singulation process according to the first embodiment. As shown in FIG. 30, the re-singulation step is a step of singulating into elastic wave devices 1A. In the first embodiment, the package 60 and the substrate 41 at the boundaries between the elastic wave devices 10A are partially removed to separate the elastic wave devices 1A again. Thereby, 1 A of elastic wave apparatuses which concern on 1st Embodiment are manufactured.

An example of the method for manufacturing the elastic wave device according to the first embodiment has been described above. It may be a method related to

31 to 38 are schematic cross-sectional views explaining one step of the method for manufacturing the elastic wave device according to the first modified example of the first embodiment. As shown in FIGS. 31 to 38, in the first modified example, the through-hole forming step is performed after the grinding step. As shown in FIGS. 31 to 37, in the first modified example, the stacking process, the functional electrode forming process, the reinforcing electrode forming process, the bump forming process, the grooving process, and the grinding process are performed on the support substrate 8. is performed in a state in which the through hole 8H is not formed.

FIG. 38 is a schematic cross-sectional view for explaining the through-hole forming process according to the first modified example of the first embodiment. In the first modification, the support substrate 8 is perforated so as to penetrate the support substrate 8 in the Z direction. Here, the through hole 8H is provided at a position overlapping with the sacrificial layer 7S and the reinforcing electrode 14 when viewed from above in the Z direction. As a result, the sacrificial layer 7S is exposed in the through hole 8H, so that in the space forming step after the through hole forming step, an etchant is injected from the end of the through hole 8H opposite to the piezoelectric layer 2 to expose the sacrificial layer 7S. can be etched. In addition, since the through-hole 8H is provided at a position overlapping the piezoelectric layer 2 in the portion overlapping with the reinforcing electrode 14 when viewed in plan in the Z direction, damage to the piezoelectric layer 2 caused by the through-hole 8H can be suppressed.

In the first modified example, after the through-hole forming process described in FIG. 38, as shown in FIGS. A singulation process is performed. Thereby, 1 A of elastic wave apparatuses can be manufactured.

As described above, the method of manufacturing the elastic wave device according to the first embodiment includes a through-hole forming step of forming the through-hole 8H in the support substrate 8, a lamination step of laminating the piezoelectric layer 2 on the support substrate 8, A functional electrode forming step of forming the functional electrode 30 on the piezoelectric layer 2, a bump forming step of forming the bump 50 connected to the functional electrode 30, a mounting step of attaching the bump 50 to the mounting substrate 40, a space portion (first and a space forming step of forming a space 91). Immediately after the lamination step, the sacrificial layer 7S is laminated between the piezoelectric layer 2 and the support substrate 8. Immediately before the space forming step, part of the sacrificial layer 7S is exposed in the through hole 8H. In the space forming step, the space is formed by etching the sacrificial layer 7S. As a result, the space can be formed by etching the sacrificial layer 7S without providing the through hole 8H in the piezoelectric layer 2, so that the generation of cracks in the piezoelectric layer 2 can be suppressed.

A preferred embodiment further includes a singulation step of singulating into the acoustic wave devices 10A and a packaging step of packaging the acoustic wave devices 10A. In the packaging process, the end of the through hole 8H opposite to the piezoelectric layer 2 is covered with the package 60 . As a result, the end of the through hole 8H opposite to the piezoelectric layer 2 is supported by the package 60, so that damage to the support member 80 starting from the through hole 8H can be suppressed.

As a desirable mode, the method further includes a reinforcing electrode forming step for providing the reinforcing electrode 14, and immediately before the space forming step, the reinforcing electrode 14 overlaps the through-hole 8H in a plan view in the thickness direction of the support substrate 8. Accordingly, it is possible to prevent the piezoelectric layer 2 from being damaged by the through hole 8H.

It should be noted that the above-described embodiments are intended to facilitate understanding of the present disclosure, and are not intended to limit and interpret the present disclosure. This disclosure may be modified/improved without departing from its spirit, and this disclosure also includes equivalents thereof.

1, 1A to 1C, 101, 301 elastic wave device 2 piezoelectric layer 2a first main surface 2b second main surface 3 electrode finger (first electrode finger)
4 electrode finger (second electrode finger)
5 busbar electrode (first busbar electrode)
6 busbar electrode (second busbar electrode)
7 intermediate layer 7a opening 7S sacrificial layer 8 support substrate 8a opening 8H through hole 9 space 10A to 10C elastic wave element 14 reinforcing electrodes 30, 30A functional electrodes 35, 35A wiring electrode 40 mounting substrate 41 substrate 42 substrate wiring 50 bump 60 package 80 support member 91 first space 91a resonator space 91b lead-out portion 92 second space 201 piezoelectric layer 201a first main surface 201b second main surface 251 first region 252 second regions 310, 311 reflection Device C excitation region (intersection region)
G grooves R1 to R3 resonator VP1 virtual plane

Claims (19)

1. a piezoelectric layer having a thickness in a first direction and having a first principal surface and a second principal surface; and a functional electrode provided on at least one of the first principal surface and the second principal surface. and a bump connected to the functional electrode, and a support member provided on the second principal surface side with respect to the piezoelectric layer;
   a mounting substrate connected to the acoustic wave element via the bump;
   with
   The support member comprises a support substrate,
   The support member has a space portion on the piezoelectric layer side of the support member and a through hole penetrating the support substrate,
   The elastic wave device, wherein the through hole communicates with the space.
2. further comprising a package that houses the acoustic wave element,
   The elastic wave device according to claim 1, wherein the package covers an end of the through hole opposite to the piezoelectric layer.
3. The support member further comprises an intermediate layer provided on the piezoelectric layer side of the support substrate,
   3. The elastic wave device according to claim 1, wherein said space is in said intermediate layer.
4. The elastic wave device according to claim 3, wherein at least a part of the through-hole overlaps with the space when viewed in the first direction.
5. The elastic wave device according to any one of claims 1 to 4, wherein the area of the region overlapping with the space is smaller than the area of the region overlapping with the through hole when viewed in plan in the first direction.
6. A plurality of the through holes are provided,
   The elastic wave device according to any one of claims 1 to 5, wherein the space portion communicates with at least two of the through holes.
7. The functional electrode has a plurality of first electrode fingers extending in a second direction orthogonal to the first direction, or a plurality of first electrode fingers extending in a third direction orthogonal to the first direction and the second direction. a plurality of second electrode fingers facing the second direction and extending in the second direction;
   The elastic wave device according to any one of claims 1 to 6, wherein the functional electrode is provided so that at least a part of the functional electrode overlaps the space when viewed in plan in the first direction.
8. The acoustic wave element further includes a reinforcing electrode provided between the piezoelectric layer and the bump,
   The elastic wave device according to claim 7 , wherein the through hole is provided so that at least a part of the through hole overlaps with the reinforcing electrode in plan view in the first direction.
9. When the region where the adjacent first electrode fingers and the second electrode fingers overlap each other when viewed in the direction in which they face each other is defined as an excitation region, the space portion, when viewed in plan in the first direction, is: Having a functional portion that overlaps with the excitation region and a non-functional portion that does not overlap with the excitation region,
   The through hole is provided at a position not overlapping the functional portion when viewed in plan in the first direction,
   The elastic wave device according to claim 8, wherein at least a portion of said non-functional portion overlaps said reinforcing electrode when viewed in plan in said first direction.
10. 10. The ratio d/p is 0.5 or less, where d is the film thickness of the piezoelectric layer and p is the center-to-center distance between the adjacent first electrode fingers and the second electrode fingers. 1. The elastic wave device according to claim 1.
11. The acoustic wave device according to any one of claims 7 to 10, wherein the piezoelectric layer contains lithium niobate or lithium tantalate.
12. 3. The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate forming the piezoelectric layer are within the range of the following formula (1), formula (2), or formula (3). 12. The elastic wave device according to 11.
    (0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
    (0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ² /900) ^1/2 ) or (0°±10°, 20° to 80°, {180 °-60° (1-(θ-50) ² /900) ^1/2 } ~ 180°) Equation (2)
    (0°±10°, {180°−30°(1−(ψ−90) ² /8100) ^1/2 } to 180°, arbitrary ψ) Equation (3)
13. The elastic wave device according to any one of claims 7 to 12, configured to be able to use thickness shear mode bulk waves.
14. 14. Any one of claims 7 to 13, wherein d/p is 0.24 or less, where d is the film thickness of the piezoelectric layer and p is the distance between the centers of the adjacent first electrode fingers and the second electrode fingers. 1. The elastic wave device according to claim 1.
15. When the region where the adjacent first electrode fingers and the second electrode fingers overlap each other when viewed in the facing direction is the excitation region, the plurality of the first electrode fingers and the second electrode fingers with respect to the excitation region are defined as the excitation region. The elastic wave device according to any one of claims 7 to 14, wherein MR ≤ 1.75 (d/p) + 0.075 is satisfied, where MR is the metallization ratio of the two electrode fingers.
16. The elastic wave device according to any one of claims 1 to 8, configured to be able to use plate waves.
17. a through-hole forming step of forming a through-hole in the support substrate;
    a lamination step of laminating a piezoelectric layer on the support substrate;
    an electrode forming step of forming a functional electrode on the piezoelectric layer;
    a bump forming step of forming bumps connected to the functional electrodes;
    a mounting step of attaching the bumps to a mounting substrate;
    A space portion forming step of forming a space portion;
    has
    Immediately after the lamination step, a sacrificial layer is laminated between the piezoelectric layer and the support substrate,
    A portion of the sacrificial layer is exposed in the through hole immediately before the space forming step,
    In the space forming step, the space is formed by etching the sacrificial layer.
18. a singulation step of singulating into acoustic wave devices;
    further comprising a packaging step of packaging the acoustic wave device,
    18. The method of manufacturing an acoustic wave device according to claim 17, wherein in said packaging step, an end of said through-hole opposite to said piezoelectric layer is covered with a package.
19. Further having a reinforcing electrode forming step of providing a reinforcing electrode,
    19. The method of manufacturing an elastic wave device according to claim 17, wherein immediately before said space forming step, said reinforcing electrode overlaps with said through-hole when viewed in plan in the thickness direction of said support substrate.

Images