WO2023013694A1

WO2023013694A1 - Elastic wave apparatus and method for manufacturing elastic wave apparatus

Info

Publication number: WO2023013694A1
Application number: PCT/JP2022/029841
Authority: WO
Inventors: 毅山根; 誠二甲斐
Original assignee: 株式会社村田製作所
Priority date: 2021-08-03
Filing date: 2022-08-03
Publication date: 2023-02-09

Abstract

The present invention addresses the problem of suppressing variation in chip size. This elastic wave apparatus comprises: a first substrate; a piezoelectric layer that overlaps the first substrate as seen in a first direction and has a first main surface and a second main surface on the opposite side from the first main surface; a functional electrode provided to at least one of the first main surface and the second main surface of the piezoelectric layer; a second surface facing the first main surface of the piezoelectric layer in the first direction; and a support supporting the second substrate between the first main surface of the piezoelectric layer and the second substrate. The second substrate is smaller than the first substrate as seen in the first direction, the contour of the second substrate is on the inside of the contour of the first substrate as seen in the first direction, and, as seen in a planar direction orthogonal to the first direction, an end surface of at least one contour of the piezoelectric layer on the second substrate side of the first substrate, a metal on the outside of the piezoelectric layer, and a silicon nitride on the outside of the piezoelectric layer, is at least partially exposed.

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 disclosed in Patent Document 1, when the electrodes are covered with a substrate, packaged in a wafer level, and separated into individual pieces by dicing, the characteristics may deteriorate due to variations in the chip size (the size of the acoustic wave device). had a nature.

The present disclosure is intended to solve the above-described problems, and aims to suppress variations in chip size.

An acoustic wave device according to one aspect is a piezoelectric device having a first substrate, a first main surface overlapping the first substrate when viewed in a first direction, and a second main surface opposite to the first main surface. a layer, a functional electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer, and a second substrate facing the first main surface of the piezoelectric layer in the first direction. and a support portion that supports the second substrate between the first main surface of the piezoelectric layer and the second substrate, wherein the second substrate is the first substrate when viewed in the first direction. The outer shape of the second substrate is inside the outer shape of the first substrate when viewed in the first direction, and the second substrate of the first substrate when viewed in a plane direction orthogonal to the first direction. An edge face of at least one of the piezoelectric layer on the substrate side, the metal on the outside of the piezoelectric layer, and the silicon nitride on the outside of the piezoelectric layer is at least partially exposed.

A method of manufacturing an elastic wave device according to one aspect includes: a piezoelectric layer having a first main surface and a second main surface opposite to the first main surface; A first substrate formed at a position overlapping with a functional electrode provided on at least one of two main surfaces in a first direction, a second substrate facing the first main surface of the piezoelectric layer, and a support portion. a bonding step of bonding through the first substrate; a resist forming step of forming a resist on the second substrate after the bonding step; a polishing step of, after the etching step, polishing the main surface of the first substrate opposite to the second substrate to thin the first substrate and singulate it; and in the bonding step, a position where none of the piezoelectric layer on the second substrate side of the first substrate, the metal on the outside of the piezoelectric layer, and the silicon nitride on the outside of the piezoelectric layer is elastic In the resist forming step, the resist is smaller than the area surrounded by the boundary when viewed in the first direction, and the outer shape of the resist is , inside the region surrounded by the boundary when viewed in the first direction, and in the etching step, the piezoelectric layer on the second substrate side of the first substrate, the metal outside the piezoelectric layer, and the At least one of the silicon nitrides on the outside of the piezoelectric layer serves as a mask for regulating the outer shape of the singulated first substrate.

According to the present disclosure, variations in chip size can be suppressed.

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 in 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. 13 is a plan view showing an example of the elastic wave device according to the first embodiment; FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. 13. FIG. 15 is a plan view of an acoustic wave element substrate of the acoustic wave device according to the first embodiment. FIG. 16 is a plan view of a cover member of the elastic wave device according to the first embodiment; FIG. FIG. 17 is a schematic cross-sectional view for explaining a bonding process for forming a support member for the acoustic wave device substrate. FIG. 18 is a schematic cross-sectional view for explaining an electrode forming process for forming functional electrodes of the acoustic wave device substrate. FIG. 19 is a schematic cross-sectional view for explaining a first space portion forming step for forming the first space portion of the acoustic wave device substrate. FIG. 20 is a schematic cross-sectional view for explaining a cover member forming process for forming the cover member. FIG. 21 is a schematic cross-sectional view for explaining a bonding step of bonding the acoustic wave device substrate and the cover member via the supporting portion. FIG. 22 is a schematic cross-sectional view for explaining a thinning step for thinning the second substrate. FIG. 23 is a schematic cross-sectional view for explaining a through-via forming step for forming through-vias in the second substrate. FIG. 24 is a schematic cross-sectional view for explaining a terminal electrode forming step for forming terminal electrodes on the second substrate. FIG. 25 is a schematic cross-sectional view for explaining the step of forming an insulating film for insulating the periphery of the terminal electrode. FIG. 26 is a schematic cross-sectional view for explaining a resist forming step of forming a resist on the second substrate. FIG. 27 is a schematic cross-sectional view for explaining an etching step of dividing the second substrate into pieces and etching a part of the first substrate. FIG. 28 is a cross-sectional view for explaining a polishing step of polishing the main surface of the first substrate opposite to the second substrate to thin the first substrate and singulate it. FIG. 29 is a cross-sectional view showing an example of the elastic wave device according to the second embodiment. FIG. 30 is a cross-sectional view showing an example of an elastic wave device according to the third embodiment.

Below, embodiments of the present disclosure will be described in detail based on the drawings. Note that the present disclosure is not limited by this embodiment. It should be noted that each embodiment described in the present disclosure is an exemplary one, and among different embodiments, a modification that allows partial replacement or combination of configurations, and the first embodiment after the second embodiment A description of matters common to the embodiment will be omitted, and only different points will be described. In particular, similar actions and effects due to similar configurations will not be mentioned sequentially for each embodiment.

(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. Both the length direction of the

electrode fingers

3 and 4 and the direction orthogonal to the length direction of the

electrode fingers

3 and 4 are directions that intersect the thickness direction of the piezoelectric layer 2 . Therefore, it can be said that the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 face each other in the direction intersecting the thickness direction of the piezoelectric layer 2 . In the following description, the thickness direction of the piezoelectric layer 2 is defined as the Z direction (or first direction), the length direction of the

electrode fingers

3 and 4 is defined as the Y direction (or second direction), and the electrode fingers 3 and electrode fingers 4 may be described as the X direction (or the third direction).

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, or the like.

The center-to-center distance, that is, the pitch, between the

electrode fingers

3 and 4 is preferably in the range of 1 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 support substrate 8 is laminated on the second main surface 2b with the intermediate layer 7 interposed therebetween at a position not overlapping the portion where at least one pair of

electrode fingers

3 and 4 are provided. Note that the intermediate layer 7 may not be provided. Therefore, the support substrate 8 can be directly or indirectly laminated to the second main surface 2b of the piezoelectric layer 2 .

The intermediate layer 7 is made of silicon oxide. 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 an appropriate metal or alloy such as Al or an AlCu alloy. 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 AC voltage is applied between the multiple electrode fingers 3 and the multiple electrode fingers 4 . More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 6 . As a result, it is possible to obtain resonance characteristics using a thickness-shear primary mode bulk wave excited in the piezoelectric layer 2 .

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 p between the

adjacent electrode fingers

3 and 4 is the average distance between the center-to-center distances between the

adjacent electrode fingers

3 and 4 .

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 in the piezoelectric layer of the first embodiment.

FIG. 3A shows an acoustic wave device as described in Patent Document 1, in which Lamb waves propagate through the piezoelectric layer. As shown in FIG. 3A, waves propagate through the piezoelectric layer 201 as indicated by arrows. Here, the piezoelectric layer 201 has a first principal surface 201a and a second principal surface 201b, and the thickness direction connecting the first principal surface 201a and the second principal surface 201b is the Z direction. The X direction is the direction in which the

electrode fingers

3 and 4 of the IDT electrodes are aligned. As shown in FIG. 3A, in the Lamb wave, the wave propagates in the X direction as shown. Since it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates in the X direction, so reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is attempted, that is, when the number of logarithms of the

electrode fingers

3 and 4 is reduced, the Q value is lowered.

On the other hand, as shown in FIG. 3B, in the elastic wave device of the first embodiment, since the vibration displacement is in the thickness sliding direction, the wave is applied to the first main surface 2a and the second main surface 2b of the piezoelectric layer 2. , 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 orthogonal 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.

In the first embodiment, the inter-electrode distances of the electrode pairs consisting of the

electrode fingers

3 and 4 are all equal in a plurality of pairs. That is, the electrode fingers 3 and the electrode fingers 4 are arranged at equal pitches.

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. 6 shows d/2p, where p is the center-to-center distance between adjacent electrodes or the average distance of the center-to-center distances, and d is the average thickness of the piezoelectric layer 2. It is an explanatory view showing the relationship with the fractional bandwidth as.

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.

Note that at least one pair of electrodes may be one pair, and the above p is the center-to-center distance between

adjacent electrode fingers

3 and 4 in the case of one pair of electrodes. In the case of 1.5 pairs or more of electrodes, the average distance between the centers of

adjacent electrode fingers

3 and 4 should be p.

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 is a region where the

electrode fingers

3 and 4 overlap with the electrode fingers 4 when viewed in a direction perpendicular to the length direction of the

electrode fingers

3 and 4, that is, in a facing direction. a region where the electrode fingers 3 overlap each other; and a region between the

electrode fingers

3 and 4 where the

electrode fingers

3 and 4 overlap each other. The area of the

electrode fingers

3 and 4 in the excitation region C with respect to the area of the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of the metallization portion to the area of the excitation region C.

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, 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 ]~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 Lamb 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 a first electrode finger 3 and a second electrode finger 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2. and the second electrode fingers 4 are desirably covered with a protective film.

FIG. 13 is a plan view showing an example of the elastic wave device according to the first embodiment. FIG. 13 is a plan view of the acoustic wave device from the side where the acoustic wave device substrate 10 is provided. 14 is a cross-sectional view taken along line XIV-XIV in FIG. 13. FIG. As shown in FIGS. 13 and 14, the elastic wave device according to the first embodiment includes an elastic wave element substrate 10 and a cover member 40. As shown in FIGS. The acoustic wave device substrate 10 and the cover member 40 are joined by a support portion. The support is a member that includes the first metal layer 35, the second metal layer 14 and the seal metal layers 43,44. In the following description, one of the directions parallel to the Z direction may be described as upward.

In the following, when viewed from above in the Z direction, the outermost closed line in the outline of the range occupied by a certain member will be described as the outer shape of that member. In the following description, a surface that overlaps the outer shape of a certain member when viewed in the Z direction and is not substantially parallel to the XY plane is defined as an end face of the outer shape of the member.

FIG. 15 is a plan view of the elastic wave element substrate of the elastic wave device according to the first embodiment. FIG. 15 is a plan view of the acoustic wave device substrate 10 from the side where the cover member 40 is provided. As shown in FIG. 15, the acoustic wave device substrate 10 is a member having at least one functional electrode 30. As shown in FIG. In the first embodiment, the acoustic wave device substrate 10 includes two functional electrodes 30 , a supporting member, the piezoelectric layer 2 , the first metal layer 35 , the second metal layer 14 and the dielectric film 19 .

The support member is a member provided with the support substrate 8 . The support substrate 8 is an example of a "first substrate". The support substrate 8 is, for example, a silicon substrate. In a first embodiment the support member further comprises an intermediate layer 7 . The intermediate layer 7 is laminated on the support substrate 8 . The intermediate layer 7 is, for example, a layer made of silicon oxide. Note that the intermediate layer 7 is not an essential component. In the following description, the line that is the outline of the support substrate 8 will be described as a line P1. Also, when viewed in plan in the Z direction, the region surrounded by the line P1, that is, the region overlapping the support substrate 8 may be described as the inside of the line P1. Also, a region that is not inside the line P1, that is, a region that does not overlap the support substrate 8 when viewed in plan in the Z direction may be described as being outside the line P1.

As shown in FIGS. 14 and 15, the support member is provided with a first space 91 and a drawer passage 9A. The first space 91 and the extraction passage 9A are spaces formed by etching the sacrificial layer. The first space 91 and the extraction passage 9A are provided at positions overlapping at least a portion of the functional electrode 30 when viewed in the Z direction. In the first embodiment, the first space 91 and the extraction passage 9A are formed in the intermediate layer 7. As shown in FIG. The first space 91 is a space corresponding to the space 9 shown in FIG. The drawer passage 9A is a space that communicates with a through hole 2H, which will be described later. Note that the first space 91 and the extraction passage 9A may be provided in the support substrate 8 .

The piezoelectric layer 2 is laminated on the supporting member. As shown in FIG. 14, in the first embodiment, the piezoelectric layer 2 is provided on the support substrate 8 with the intermediate layer 7 interposed therebetween. The piezoelectric layer 2 contains, for example, lithium niobate or lithium tantalate, and may further contain unavoidable impurities. It should be noted that the piezoelectric layer 2 is laminated on the support substrate 8 if the support member does not have the intermediate layer 7 . The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b. The first main surface 2 a is the main surface of the piezoelectric layer 2 on the second substrate 41 side. The second main surface 2b is a main surface opposite to the first main surface 2a, and is the main surface of the piezoelectric layer 2 on the support substrate 8 side.

At least a part of the end surface of the piezoelectric layer 2 is exposed when viewed in a direction parallel to the XY plane. In the first embodiment, the outer end faces of the piezoelectric layer 2 are all exposed. At this time, the outer shape of the piezoelectric layer 2 is the same as the outer shape of the support substrate 8 . That is, the outer shape of the piezoelectric layer 2 overlaps the line P1 when viewed from above in the Z direction. As a result, variations in chip size can be suppressed.

The piezoelectric layer 2 is provided with through holes 2H. As shown in FIG. 15, the through hole 2H is provided so as to overlap with the drawer passage 9A. The through hole 2H communicates with the drawer passage 9A, and can be said to penetrate the space 9 via the drawer passage 9A. This makes it difficult for the stress applied to the piezoelectric layer 2 to concentrate. As a result, cracks occurring in the piezoelectric layer 2 starting from the through holes 2H are suppressed.

The functional electrodes 30 are connected to the first busbar electrode 5 and the second busbar electrode 6 facing each other, the electrode fingers 3 connected to the first busbar electrode 5, and the second busbar electrode 6 shown in FIG. 1B. It is an IDT electrode having electrode fingers 4 that are connected to each other. The functional electrode 30 is provided on at least one of the first principal surface 2 a and the second principal surface 2 b of the piezoelectric layer 2 . In the first embodiment, the functional electrode 30 is provided on the first main surface 2a of the piezoelectric layer 2. As shown in FIG. That is, the functional electrode 30 is arranged inside the second space 92, which will be described later.

The first metal layer 35 and the second metal layer 14 are supporting portions that support the cover member 40 on the acoustic wave device substrate 10 . The first metal layer 35 is provided on the first main surface 2 a of the piezoelectric layer 2 . The second metal layer 14 is laminated on the first metal layer 35 . The first metal layer 35 and the second metal layer 14 are metal laminates of gold or gold alloys and other metals such as titanium. As shown in FIG. 15, the first metal layer 35 and the second metal layer 14 include those formed in a linear pattern so as to surround the functional electrode 30 in plan view in the Z direction. The second metal layer 14 includes wirings 12 electrically connected to the functional electrodes 30 . The wiring 12 is thicker than the

electrode fingers

3 and 4 . Although the first metal layer 35 and the second metal layer 14 are made of the same material in the first embodiment, they are not limited to this and may be made of different materials.

As shown in FIG. 14, in the first embodiment, the dielectric film 19 is provided on the functional electrode 30 and the first main surface 2a of the piezoelectric layer 2 on which the functional electrode 30 is provided. The dielectric film 19 is made of silicon oxide, for example.

FIG. 16 is a plan view of the cover member of the elastic wave device according to the first embodiment. FIG. 16 is a plan view of the cover member 40 from the side where the acoustic wave device substrate 10 is provided. The cover member 40 is a member including the second substrate 41 . As shown in FIGS. 14 and 16, in the first embodiment, the cover member 40 includes a second substrate 41, an insulating layer 42,

seal metal layers

43 and 44, and an insulating layer 45. As shown in FIGS. Further, the cover member 40 is provided with through vias that penetrate the second substrate 41 and the insulating

layers

42 and 45 .

The second substrate 41 is, for example, a silicon substrate. The second substrate 41 is positioned to face the first main surface 2 a of the piezoelectric layer 2 . The second substrate 41 is smaller than the support substrate 8, as shown in FIGS. Assuming that the line that is the outline of the second substrate 41 is a line P2, the line P2 is inside the line P1 that is the outline of the support substrate 8 . As a result, the size of the elastic wave device is limited by the line P1 instead of the line P2, so that variations in chip size can be suppressed. Two main surfaces of the second substrate 41 facing each other in the Z direction are covered with insulating

layers

42 and 45 made of silicon oxide. Here, in the following description, the area surrounded by the line P2, that is, the area overlapping with the second substrate 41 when viewed from above in the Z direction may be described as the inside of the line P2. Also, a region that is not inside the line P2, that is, a region that does not overlap the second substrate 41 when viewed in plan in the Z direction may be described as being outside the line P2.

The sealing

metal layers

43 and 44 are supporting portions that support the acoustic wave device substrate 10 on the cover member 40 . Seal metal layers 43 and 44 are formed on a portion of insulating layer 42, as shown in FIG. The

seal metal layers

43 and 44 are arranged inside a line P2 that is the outline of the second substrate 41 when viewed in the Z direction. The sealing

metal layers

43, 44 are metal laminates of gold or gold alloys and other metals such as titanium. The sealing

metal layers

43 , 44 are of the same material as the second metal layer 14 .

As shown in FIG. 16, the seal metal layer 43 is formed in a linear pattern so as to surround the functional electrode 30 when viewed from above in the Z direction. A seal metal layer 43 is adhered to the second metal layer 14 . As a result, the seal metal layer 43 can seal the second space 92 when viewed in the Z direction. Here, the second space portion 92 is a space between the acoustic wave device substrate 10 and the cover member 40 . Thereby, the functional electrode 30 can be protected.

The seal metal layer 44 is provided in a range surrounded by the seal metal layer 43, as shown in FIG. The seal metal layer 44 joins the cover member 40 and the acoustic wave element substrate 10 by being adhered to the wiring 12 of the second metal layer 14 . This suppresses bending of the acoustic wave device substrate 10 .

Further, as shown in FIG. 14, the through via of the cover member 40 is provided with a terminal electrode 57 and a BGA (ball grid array) bump 58 via a seed layer 56 . The seed layer 56 is a laminate in which a Cu layer is laminated on a Ti layer. The seed layer 56 includes, for example, a layer of silicon oxide interposed between the inner surface of the through via, a portion of the insulating layer 45, and the seal metal layer 44 overlapping the through via when viewed in plan in the Z direction. Laminated in parts. The terminal electrode 57 is a laminate in which a Cu layer and a Ni layer are plated with an Au layer. The terminal electrode 57 is a so-called bump metal. A terminal electrode 57 is provided inside the through via and on the seed layer 56 . The BGA bump 58 is an electrode laminated on the terminal electrode 57 . The BGA bump 58 is a so-called bump metal. Thereby, the BGA bumps 58 to the functional electrodes 30 are electrically connected.

As described above, the elastic wave device according to the first embodiment overlaps the first substrate (support substrate 8) and the first substrate when viewed in the first direction, and the first main surface 2a and the first main surface a piezoelectric layer 2 having a second main surface 2b opposite to 2a; a functional electrode 30 provided on at least one of the first main surface 2a and the second main surface 2b of the piezoelectric layer 2; a second substrate 41 facing the first main surface 2a in the first direction; The second substrate 41 is smaller than the first substrate when viewed in the first direction, and the outer shape (line P2) of the second substrate 41 is inside the outer shape (line P1) of the first substrate when viewed in the first direction, At least a part of the outer end face of the piezoelectric layer 2 on the second substrate 41 side of the first substrate is exposed when viewed in a plane direction perpendicular to the first direction. As a result, the chip size is limited by the line P1, which is the outline of the first substrate, rather than the line P2, which is the outline of the second substrate 41, so that variations in chip size can be suppressed.

As a desirable aspect, when viewed in the planar direction, all the end surfaces of the outer shape of the piezoelectric layer 2 on the second substrate 41 side of the first substrate are exposed, and when viewed in the first direction, the outer shape of the first substrate is the piezoelectric layer 2 . is the same as the external shape of As a result, variations in chip size can be further suppressed.

As a desirable aspect, the supporting portion seals between the first substrate and the second substrate 41 and is arranged inside the outline of the second substrate 41 when viewed in the first direction. As a result, it is possible to prevent moisture, dust, and the like from the outside air from entering the second space 92 between the first substrate and the second substrate 41 .

As a desirable aspect, the functional electrode 30 is arranged in a region surrounded by the support portion when viewed in the first direction. As a result, the functional electrode 30 can be protected from moisture, dust, and the like in the outside air.

The functional electrode 30 faces either one or more first electrode fingers 3 extending in a second direction intersecting the first direction or one or more first electrode fingers 3 extending in a third direction orthogonal to the second direction. and one or more second electrode fingers 4 extending in the second direction. As a result, it is possible to provide an elastic wave device capable of obtaining good resonance characteristics.

As a desirable aspect, the thickness of the piezoelectric layer 2 is the thickness between the adjacent first electrode fingers 3 and the second electrode fingers 4 among the one or more first electrode fingers 3 and the one or more second electrode fingers 4. It is 2p or less when the center-to-center distance is p. Thereby, the acoustic wave device 1 can be miniaturized and the Q value can be increased.

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 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, the thickness of the piezoelectric layer 2 is d, and the center between the adjacent first electrode fingers 3 and second electrode fingers 4 among the one or more first electrode fingers 3 and the one or more second electrode fingers 4 is d/p≦0.5, where p is the distance between them. Thereby, the acoustic wave device 1 can be miniaturized and the Q value can be increased.

A more desirable aspect is that d/p is 0.24 or less. Thereby, the acoustic wave device 1 can be miniaturized and the Q value can be increased.

Desirably, the functional electrode 30 has one or more first electrode fingers 3 extending in a second direction intersecting the first direction and one or more first electrode fingers 3 extending in a third direction orthogonal to the second direction. and one or more second electrode fingers 4 extending in the second direction, when viewed in the direction in which the adjacent first electrode fingers 3 and second electrode fingers 4 face each other. is the excitation region C, and when MR is the metallization ratio of the one or more first electrode fingers 3 and the one or more second electrode fingers 4 with respect to the excitation region C, MR≤1 .75(d/p)+0.075. In this case, the fractional bandwidth can be reliably set to 17% or less.

As a desirable aspect, it is configured so that plate waves can be used. As a result, it is possible to provide an elastic wave device capable of obtaining good resonance characteristics.

As a preferred embodiment, the piezoelectric layer 2 is made of lithium niobate or lithium tantalate, and the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate satisfy the following formula (1), formula (2) or It is in the range of formula (3). In this case, the fractional bandwidth can be widened sufficiently.

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

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.

FIG. 17 is a schematic cross-sectional view for explaining the bonding process for forming the supporting member of the acoustic wave device substrate. As shown in FIG. 17, in the bonding step, first, the sacrificial layer 7S is formed on the second main surface 2b of the piezoelectric layer 2, and then the second main surface 2b of the piezoelectric layer 2 and the sacrificial layer 7S are formed. A first portion 7A to be the intermediate layer 7 is formed so as to cover the . The surface of the first portion 7A is flattened so that unevenness due to the influence of the sacrificial layer 7S is eliminated. Next, the second portion 7B, which will be the intermediate layer 7, is formed on the support substrate 8. Next, as shown in FIG. Then, the piezoelectric layer 2 (piezoelectric substrate) is supported by the support substrate 8 by bonding the first portion 7A and the second portion 7B together. After bonding, the main surface of the piezoelectric layer 2 opposite to the second main surface 2b is polished to make the piezoelectric layer 2 thinner. This forms the first main surface 2a of the piezoelectric layer.

FIG. 18 is a schematic cross-sectional view for explaining the electrode forming process for forming the functional electrodes of the acoustic wave device substrate. As shown in FIG. 18, in the electrode forming step, the support portion 46 is formed on the piezoelectric layer 2 . Specifically, the first metal layer 35 is formed on the first main surface 2a of the piezoelectric layer 2, and the functional electrodes 30 are patterned. Then, the second metal layer 14 is formed on the first metal layer 35 . Here, a part of the second metal layer 14 becomes the wiring 12 that conducts to the functional electrode 30 . After that, a sealing metal layer 44a is laminated on the second metal layer 14 . Here, the seal metal layer 44a is an Au or Au alloy layer. Then, the periphery of the functional electrode 30 is masked with a resist, and the dielectric film 19 is formed. Thereby, the functional electrode 30 is covered with the dielectric film 19 .

FIG. 19 is a schematic cross-sectional view for explaining the first space portion forming step for forming the first space portion of the acoustic wave device substrate. As shown in FIG. 19, in the step of forming the first space, first, through holes 2H are formed in the piezoelectric layer 2 . The through hole 2H is formed at a position overlapping the sacrificial layer 7S of the piezoelectric layer 2 in plan view. At this time, the piezoelectric layer 2 is patterned in a grid pattern to remove the region outside the line P1, thereby exposing the support member in the region outside the line P1. Here, the area where the supporting member is exposed is the boundary where the acoustic wave device is singulated. Next, an etchant is injected from the through hole 2H to dissolve the sacrificial layer 7S. As a result, the space where the sacrificial layer 7S was located becomes the first space portion 91. Next, as shown in FIG. After that, a measuring instrument is connected to the wiring 12, and after confirming the frequency characteristics, the film thickness of the dielectric film 19 is adjusted by ion etching or the like. Adjustment of the film thickness of the dielectric film 19 is repeated until desired frequency characteristics are obtained.

FIG. 20 is a schematic cross-sectional view for explaining the cover member forming process for forming the cover member. As shown in FIG. 20 , in the cover member forming step, an insulating layer 42 is formed on one main surface of the second substrate 41 . Then, a seal metal layer 43 b and a seal metal layer 44 b are formed on the insulating layer 42 as the supporting portion 47 . Here, the seal metal layer 43b and the seal metal layer 44b are Au or Au alloy layers.

FIG. 21 is a schematic cross-sectional view for explaining a bonding step of bonding the acoustic wave element substrate and the cover member via the supporting portion. As shown in FIG. 21, in the joining step, the support portion 47 of the acoustic wave device substrate 10 and the support portion 46 of the cover member 40 facing each other are joined. Specifically, the seal metal layer 43a of the acoustic wave element substrate 10 and the seal metal layer 43b of the cover member 40 are Au--Au bonded, and the seal metal layer 43a and the seal metal layer 43b are integrated to form the seal metal layer. 43. Further, the sealing metal layer 44a of the acoustic wave element substrate 10 and the sealing metal layer 44b of the cover member 40 are Au—Au bonded, and the sealing metal layer 44a and the sealing metal layer 44b are integrated to form the sealing metal layer 44. .

FIG. 22 is a schematic cross-sectional view for explaining the thinning process for thinning the second substrate. As shown in FIG. 22 , in the thinning step, of the main surfaces of the second substrate 41 , the main surface opposite to the side on which the insulating layer 42 is provided is ground by a grinding tool DF, thereby thinning the second substrate 41 . Reduce thickness.

FIG. 23 is a schematic cross-sectional view for explaining a through-via forming step for forming through-vias in the second substrate. As shown in FIG. 23, in the through via forming step, the through via 57H is formed by dry etching or reactive ion etching.

FIG. 24 is a schematic cross-sectional view for explaining a terminal electrode forming process for forming terminal electrodes on the second substrate. As shown in FIG. 24, in the terminal electrode forming step, a seed layer 56 is formed so as to cover the through via 57H shown in FIG. The seed layer 56 is formed by forming a Ti layer and then laminating a Cu layer on the Ti layer. Thereafter, as shown in FIG. 24, after patterning a plating resist 57M on the seed layer 56 excluding the range where the terminal electrode 57 is formed, a Cu layer, a Ni layer, and an Au layer are formed on the seed layer 56 in this order. The terminal electrodes 57 are formed by stacking by plating.

FIG. 25 is a schematic cross-sectional view for explaining the insulating film forming process for insulating the periphery of the terminal electrode. As shown in FIG. 25, in the insulating film forming step, the plating resist 57M is removed and the seed layer 56 not in contact with the terminal electrode 57 is removed. Next, an insulating layer 45 is additionally formed so as to insulate the periphery of the terminal electrode 57 .

FIG. 26 is a schematic cross-sectional view for explaining a resist forming process for forming a resist on the second substrate. As shown in FIG. 26, in the resist forming step, a resist 40R is formed on the side of the cover member 40 where the terminal electrodes 57 are provided. At this time, the resist 40R is smaller than the area surrounded by the boundary where the acoustic wave device is singulated in plan view, and the outer shape of the resist 40R is the area surrounded by the boundary in plan view. It is inside a certain line P1. In other words, the resist 40R is patterned with a width wider than the patterning of the piezoelectric layer 2 along the boundary where the acoustic wave device is singulated, and the outside of the line P2 inside the line P1 is removed. As a result, the chip size can be limited by the size of the support substrate 8 as the first substrate, not by the size of the second substrate 41 .

FIG. 27 is a schematic cross-sectional view for explaining an etching step of dividing the second substrate into individual pieces and etching a part of the first substrate. As shown in FIG. 27, in the etching step, the second substrate 41 is separated into pieces, and part of the first substrate is etched. Etching is performed, for example, by wet etching. In the first embodiment, part of the intermediate layer 7 and the support substrate 8 is etched in the etching process. At this time, the end faces of the outer shape of the piezoelectric layer 2 are all exposed, and the piezoelectric layer 2 between the line P1 and the line P2 in plan view defines the outer shape (line P1) of the support substrate 8 against etching. It becomes a regulated mask. That is, the intermediate layer 7 and the support substrate 8 in the area surrounded by the line P1, which is the outline of the piezoelectric layer 2, are covered with the piezoelectric layer 2 even outside the line P2, which is the outline of the resist 40R. Therefore, it is not etched. On the other hand, since the intermediate layer 7 and the support substrate 8 in the area outside the line P1, which is the outline of the piezoelectric layer 2, are exposed, they are etched. As a result, the size of the support substrate 8, which is the first substrate, is limited by the line P1, which is the outer shape of the piezoelectric layer 2, so that variations in chip size can be suppressed.

FIG. 28 is a cross-sectional view for explaining a polishing step of polishing the main surface of the first substrate opposite to the second substrate to thin the first substrate and singulate it. As shown in FIG. 28, in the polishing step, after removing the resist 40R and providing the BGA bumps 58 on the terminal electrodes 57, the support substrate 8 is ground with a grinding tool to reduce the thickness of the support substrate 8. and individualized for each elastic wave device. At this time, the thickness of the support substrate 8 may be thinner than the thickness of the intermediate layer 7 . Also, the end face of the outer shape of the piezoelectric layer 2 may be processed into a tapered shape.

The method of manufacturing the elastic wave device according to the first embodiment described above is merely an example, and is not limited to this. For example, the electrode formation step may be performed after the first space portion formation step, and the functional electrode 30 may be provided on the second main surface 2b of the piezoelectric layer 2 .

As described above, the method for manufacturing an acoustic wave device according to the first embodiment includes the piezoelectric layer 2 having the first principal surface 2a and the second principal surface 2b opposite to the first principal surface 2a, and the piezoelectric layer 2 having the first principal surface 2a and the second principal surface 2b opposite to the first principal surface 2a a first substrate formed at a position where the functional electrode 30 provided on at least one of the first main surface 2a and the second main surface 2b of the layer 2 overlaps in the first direction; 2a and a second substrate 41 facing via a support portion; after the bonding step, a resist forming step of forming a resist 40R on the second substrate 41; after the resist forming step, the second substrate 41 is separated into pieces, an etching step of etching a part of the first substrate, and after the etching step, the main surface of the first substrate opposite to the second substrate 41 is polished to thin the first substrate, In the bonding step, patterning is performed so that a position of the first substrate on the side of the second substrate 41 where the piezoelectric layer 2 is absent serves as a boundary where the acoustic wave device is singulated. In the resist forming process, the resist 40R is smaller than the area surrounded by the boundary when viewed in the first direction, the outline of the resist 40R is inside the area surrounded by the boundary when viewed in the first direction, and the etching is performed. In the process, the piezoelectric layer 2 on the second substrate 41 side of the first substrate serves as a mask for regulating the outer shape of the singulated first substrate. As a result, the chip size is limited by the line P1, so that variations in chip size can be suppressed.

As a desirable mode, in the etching process, all the end surfaces of the outer shape of the piezoelectric layer 2 are exposed, and the piezoelectric layer 2 on the side of the second substrate 41 of the first substrate regulates the outer shape of the singulated first substrate. Become a mask. As a result, the outer shape of the first substrate is formed to be the same as the outer shape of the piezoelectric layer 2, so that variations in chip size can be further suppressed.

(Second embodiment)
FIG. 29 is a cross-sectional view showing an example of the elastic wave device according to the second embodiment. As shown in FIG. 29, the acoustic wave device according to the second embodiment differs from the first embodiment in that metal 31 is provided outside the piezoelectric layer 2 . In a second embodiment, metal 31 is provided on the support member between lines P1 and P2. Here, at least a part of the end surface of the metal 31 is exposed when viewed in a direction parallel to the XY plane. In the first embodiment, all the end surfaces of the metal 31 are exposed. At this time, the outer shape of the metal 31 is the same as the outer shape of the support substrate 8 . That is, the outer shape of the metal 31 overlaps the line P1 when viewed from above in the Z direction. Also, the metal 31 is made of the same metal as the functional electrode 30 . Accordingly, since the support substrate 8 is formed to have the same outer shape as the metal 31, variations in chip size can be suppressed.

Here, when the metal 31 is provided between the supporting portion and the first substrate, the bondability between the first substrate and the second substrate 41 deteriorates. Therefore, the metal 31 is provided so as not to overlap the supporting portion when viewed in the Z direction. As a result, it is possible to suppress deterioration in bondability between the first substrate and the second substrate 41 .

Note that the elastic wave device according to the second embodiment is not limited to that shown in FIG. For example, the metal 31 is not limited to being provided outside the piezoelectric layer 2, and may be provided on the piezoelectric layer 2 between the lines P1 and P2.

As described above, the elastic wave device according to the second embodiment includes the first substrate (support substrate 8), which overlaps the first substrate in plan view, and the first main surface 2a and the first main surface 2a. a piezoelectric layer 2 having an opposite second main surface 2b; a functional electrode 30 provided on at least one of the first main surface 2a and the second main surface 2b of the piezoelectric layer 2; a second substrate 41 facing the surface 2a in the first direction; 41 is smaller than the first substrate when viewed in the first direction, and the outer shape (line P2) of the second substrate 41 is inside the outer shape (line P1) of the first substrate when viewed in the first direction. At least a portion of the metal 31 outside the piezoelectric layer 2 is exposed when viewed in a plane direction perpendicular to the direction. As a result, the chip size is limited by the line P1, which is the outline of the first substrate, rather than the line P2, which is the outline of the second substrate 41, so that variations in chip size can be suppressed.

As a desirable aspect, the metal 31 on the outside of the piezoelectric layer 2 does not overlap the supporting portion when viewed in the first direction. As a result, it is possible to suppress deterioration in bondability between the first substrate and the second substrate 41 .

As a desirable mode, the end surface of the outer shape of the metal 31 outside the piezoelectric layer 2 is exposed when viewed in the planar direction, and the outer shape (line P1) of the first substrate is outside the piezoelectric layer 2 when viewed in the first direction. is the same as the outer shape of the metal 31 in . As a result, variations in chip size can be further suppressed.

As a preferred embodiment, the metal 31 outside the piezoelectric layer 2 is made of the same metal as the functional electrode 30. Even in this case, variations in chip size can be suppressed.

A method for manufacturing an elastic wave device according to the second embodiment will be described below. Note that steps similar to those in the first embodiment will not be explained one by one.

In the method of manufacturing the elastic wave device according to the second embodiment, the patterning of the piezoelectric layer 2 in the first space forming step removes the area outside the line P2 to expose the support member in this area. After that, a metal 31 is laminated on the portion near the outer shape of the piezoelectric layer 2 and the supporting member from which the piezoelectric layer 2 has been removed. At this time, the metal 31 is laminated so as not to overlap with the supporting portion when viewed in plan in the Z direction, so that the bondability between the first substrate and the second substrate 41 in the bonding process can be improved. The metal 31 in the areas outside the line P1 is then patterned away to re-expose the support members in those areas. Here, the area where the supporting member is exposed is the boundary where the acoustic wave device is singulated. As a result, in the etching step, the end faces of the outline of the metal 31 are all exposed, and in plan view, the metal 31 outside the line P2 that is the outline of the support substrate 8 is exposed to the line P1 that is the outline of the support substrate 8 with respect to the etching. becomes a mask that regulates That is, even outside the line P2, which is the outline of the resist 40R, the intermediate layer 7 and the support substrate 8 in the region surrounded by the line P1, which is the outline of the metal 31, are covered with the metal 31. Not etched. On the other hand, the intermediate layer 7 and the support substrate 8 in the area outside the line P1, which is the contour of the piezoelectric layer 2, are exposed and thus etched. Therefore, since the size of the support substrate 8, which is the first substrate, is limited by the line P1, which is the outline of the metal 31, variations in chip size can be suppressed.

The method for manufacturing the elastic wave device according to the second embodiment is not limited to the method described above. For example, if the metal 31 is provided on the piezoelectric layer 2 between the lines P1 and P2, the metal 31 may be patterned at the same time as the functional electrode 30 and the first metal layer 35 in the electrode formation process. good.

As described above, the method for manufacturing an acoustic wave device according to the second embodiment includes the piezoelectric layer 2 having the first principal surface 2a and the second principal surface 2b opposite to the first principal surface 2a, the piezoelectric a first substrate formed at a position where the functional electrode 30 provided on at least one of the first main surface 2a and the second main surface 2b of the layer 2 overlaps in the first direction; 2a and a second substrate 41 facing via a support portion; after the bonding step, a resist forming step of forming a resist 40R on the second substrate 41; after the resist forming step, the second substrate 41 is separated into pieces, an etching step of etching a part of the first substrate, and after the etching step, the main surface of the first substrate opposite to the second substrate 41 is polished to thin the first substrate, In the bonding step, patterning is performed so that a position outside the piezoelectric layer 2 where there is no metal 31 serves as a boundary where the elastic wave device is singulated, and a resist is formed. In the process, the resist 40R is smaller than the area surrounded by the boundary when viewed in the first direction, the outline of the resist 40R is inside the area surrounded by the boundary when viewed in the first direction, and the piezoelectric layer The metal 31 on the outside of 2 serves as a mask for regulating the outer shape (line P1) of the singulated first substrate. As a result, the chip size is limited by the line P1, so that variations in chip size can be suppressed.

As a desirable aspect, in the bonding process, the metal 31 outside the piezoelectric layer 2 is provided so as not to overlap the supporting portion when viewed in the first direction. Thereby, the first substrate and the second substrate 41 can be satisfactorily bonded in the bonding step.

As a desirable mode, in the etching process, all the end surfaces of the outer shape of the metal 31 on the outside of the piezoelectric layer 2 are exposed, and the metal 31 on the outer side of the piezoelectric layer 2 regulates the outer shape of the singulated first substrate. It becomes a mask to do. As a result, the outer shape of the first substrate is formed to be the same as the outer shape of the metal 31, so that variations in chip size can be further suppressed.

(Third embodiment)
FIG. 30 is a cross-sectional view showing an example of an elastic wave device according to the third embodiment. As shown in FIG. 30, the acoustic wave device according to the third embodiment is different from the first embodiment in that silicon nitride 32 is provided outside the piezoelectric layer 2 . In a second embodiment, silicon nitride 32 is provided on the support member between lines P1 and P2. Here, at least a part of the end surface of the silicon nitride 32 is exposed when viewed in a direction parallel to the XY plane. In the first embodiment, the end faces of the outer shape of the silicon nitride 32 are all exposed. At this time, the outer shape of the silicon nitride 32 is the same as the outer shape of the support substrate 8 . That is, the outer shape of the silicon nitride 32 overlaps the line P1 when viewed from above in the Z direction. Accordingly, since the support substrate 8 is formed to have the same outer shape as the silicon nitride 32, variations in chip size can be suppressed.

Here, when the silicon nitride 32 is provided between the supporting portion and the first substrate, the bondability between the first substrate and the second substrate 41 deteriorates. Therefore, the silicon nitride 32 is provided so as not to overlap the supporting portion when viewed in the Z direction. As a result, it is possible to suppress deterioration in bondability between the first substrate and the second substrate 41 .

Note that the elastic wave device according to the third embodiment is not limited to that shown in FIG. For example, the silicon nitride 32 is not limited to being provided outside the piezoelectric layer 2, and may be provided on the piezoelectric layer 2 between the lines P1 and P2.

As described above, the elastic wave device according to the third embodiment includes the first substrate (support substrate 8), which overlaps the first substrate in plan view, and the first main surface 2a and the first main surface 2a. a piezoelectric layer 2 having an opposite second main surface 2b; a functional electrode 30 provided on at least one of the first main surface 2a and the second main surface 2b of the piezoelectric layer 2; a second substrate 41 facing the surface 2a in the first direction; 41 is smaller than the first substrate when viewed in the first direction, the outer shape of the second substrate 41 is inside the outer shape of the first substrate when viewed in the first direction, and when viewed in a plane direction orthogonal to the first direction , the silicon nitride 32 outside the piezoelectric layer 2 is exposed on at least a part of the outer edge of the first substrate. As a result, the chip size is limited by the line P1, which is the outline of the first substrate, rather than the line P2, which is the outline of the second substrate 41, so that variations in chip size can be suppressed.

As a desirable aspect, the silicon nitride 32 outside the piezoelectric layer 2 does not overlap the support when viewed in the first direction. As a result, it is possible to suppress deterioration in bondability between the first substrate and the second substrate 41 .

As a desirable mode, the silicon nitride 32 outside the piezoelectric layer 2 is exposed on all end surfaces of the outer shape of the first substrate when viewed in the plane direction, and the outer shape of the first substrate when viewed in the first direction is: It has the same outline as the silicon nitride 32 outside the piezoelectric layer 2 . As a result, variations in chip size can be further suppressed.

A method for manufacturing an elastic wave device according to the third embodiment will be described below. In addition, the manufacturing method described below is an example, and is not limited to this. Note that steps similar to those in the first embodiment will not be explained one by one.

In the method of manufacturing the acoustic wave device according to the third embodiment, the patterning of the piezoelectric layer 2 in the first space forming step removes the area outside the line P2 to expose the support member in this area. After that, silicon nitride 32 is laminated on the portion near the outer shape of the piezoelectric layer 2 and the supporting member from which the piezoelectric layer 2 has been removed. At this time, the silicon nitride 32 is laminated so as not to overlap with the supporting portion when viewed in plan in the Z direction. The silicon nitride 32 in the areas outside the line P1 is then patterned away to re-expose the support members in those areas. Here, the area where the supporting member is exposed is the boundary where the acoustic wave device is singulated. As a result, in the etching process, the end faces of the outline of the silicon nitride 32 are all exposed, and in plan view, the silicon nitride 32 outside the outline line P2 is the outline of the support substrate 8 for etching. It becomes a mask for regulating the line P1. That is, the intermediate layer 7 and the support substrate 8 in the region surrounded by the line P1, which is the outline of the silicon nitride 32, are covered with the silicon nitride 32 even outside the line P2, which is the outline of the resist 40R. Therefore, it is not etched. On the other hand, the intermediate layer 7 and the support substrate 8 in the area outside the line P1, which is the contour of the piezoelectric layer 2, are exposed and thus etched. Therefore, since the size of the support substrate 8, which is the first substrate, is limited by the line P1, which is the outline of the silicon nitride 32, variations in chip size can be suppressed.

The method for manufacturing the elastic wave device according to the third embodiment is not limited to the method described above. For example, when the silicon nitride 32 is provided on the piezoelectric layer 2 between the lines P1 and P2, the silicon nitride 32 is formed simultaneously with the functional electrode 30 and the first metal layer 35 in the electrode formation process. good too.

As described above, the method for manufacturing an acoustic wave device according to the third embodiment includes the piezoelectric layer 2 having the first principal surface 2a and the second principal surface 2b opposite to the first principal surface 2a, the piezoelectric a first substrate formed at a position where the functional electrode 30 provided on at least one of the first main surface 2a and the second main surface 2b of the layer 2 overlaps in the first direction; 2a and a second substrate 41 facing via a support portion; after the bonding step, a resist forming step of forming a resist 40R on the second substrate 41; after the resist forming step, the second substrate 41 is separated into pieces, an etching step of etching a part of the first substrate, and after the etching step, the main surface of the first substrate opposite to the second substrate 41 is polished to thin the first substrate, In the bonding step, the patterning is performed so that the position where the silicon nitride 32 is absent becomes the boundary where the elastic wave device is singulated, and in the resist forming step, the resist 40R is , smaller than the area surrounded by the boundary when viewed in the first direction, the outer shape of the resist 40R is inside the area surrounded by the boundary when viewed in the first direction, and in the etching process, the nitride layer outside the piezoelectric layer 2 is formed. The silicon 32 serves as a mask for regulating the outer shape (line P1) of the first substrate separated into pieces. As a result, the chip size is limited by the line P1, so that variations in chip size can be suppressed.

As a desirable aspect, in the bonding process, the silicon nitride 32 outside the piezoelectric layer 2 is provided so as not to overlap the supporting portion when viewed in the first direction. Thereby, the first substrate and the second substrate 41 can be satisfactorily bonded in the bonding step.

As a desirable mode, in the etching process, all the end faces of the outer shape of the silicon nitride 32 outside the piezoelectric layer 2 are exposed, and the silicon nitride 32 outside the piezoelectric layer 2 is cut into pieces to form the outer shape of the first substrate. becomes a mask that regulates As a result, the outer shape of the first substrate is formed to be the same as the outer shape of the silicon nitride 32, so that variations in chip size can be further suppressed.

The above embodiments are for facilitating understanding of the present disclosure, and are not for limiting interpretation of the present disclosure. This disclosure may be modified/modified without departing from its spirit, and this disclosure also includes equivalents thereof.

For example, the acoustic wave device includes the piezoelectric layer 2 on the second substrate 41 side of the first substrate, the metal 31 on the outside of the piezoelectric layer 2, and the metal 31 on the outside of the piezoelectric layer 2 when viewed in a plane direction orthogonal to the first direction. At least one end surface of the outer shape of the silicon nitride 32 should be at least partially exposed. Even in this case, the chip size is limited by the line P1, which is the outline of the first substrate, rather than the line P2, which is the outline of the second substrate 41, so that variations in chip size can be suppressed.

For example, in the method of manufacturing an acoustic wave device, in the bonding step, the piezoelectric layer 2 on the second substrate 41 side of the first substrate, the metal 31 on the outside of the piezoelectric layer 2, and the silicon nitride 32 on the outside of the piezoelectric layer 2 are bonded together. The patterning is performed so that the position where neither of them exists becomes the boundary where the elastic wave device is singulated. The outline of 40R is inside the area surrounded by the boundary when viewed in the first direction, and the outline of the first substrate (line P1) where the silicon nitride 32 outside the piezoelectric layer 2 is singulated in the etching process. may be a mask that regulates the Even in this case, since the chip size is limited by the line P1, variations in chip size can be suppressed.

1, 101, 301 elastic wave device 2 piezoelectric layer 2H through hole 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 7A first portion 7B second portion 7S sacrificial layer 8 support substrate (first substrate)
8a opening 9 space 9A extraction passage 10 elastic wave element substrate 12 wiring 14 second metal layer 19 dielectric film 30 functional electrode 31 metal 32 silicon nitride 35 first metal layer 40 cover member 40R resist 41 second substrate 42 insulating

layer

43, 43a, 43b, 44, 44a, 44b Sealing metal layer 45

Insulating layers

46, 47 Supporting part 56 Seed layer 57 Terminal electrode 57H Through via 57M Plating resist 58 BGA bump 91 First space 92 Second space 201 Piezoelectric layer 201a first main surface 201b second main surface 251 first region 252

second regions

310, 311 reflector C excitation regions P1, P2 line VP1 virtual plane

Claims

a first substrate;
a piezoelectric layer overlapping the first substrate when viewed in a first direction and having a first main surface and a second main surface opposite to the first main surface;
a functional electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer;
a second substrate facing the first main surface of the piezoelectric layer in the first direction;
a support portion that supports the second substrate between the first main surface of the piezoelectric layer and the second substrate;
with
the second substrate is smaller than the first substrate when viewed in the first direction, and the outer shape of the second substrate is inside the outer shape of the first substrate when viewed in the first direction;
At least one of the piezoelectric layer on the second substrate side of the first substrate, the metal on the outside of the piezoelectric layer, and the silicon nitride on the outside of the piezoelectric layer when viewed in a plane direction orthogonal to the first direction An acoustic wave device, wherein an end face of one profile is at least partially exposed.
The elastic wave device according to claim 1, wherein the metal outside the piezoelectric layer and the silicon nitride outside the piezoelectric layer do not overlap the supporting portion when viewed in the first direction.
When viewed in the plane direction, all the end surfaces of the outer shape of the piezoelectric layer on the second substrate side of the first substrate are exposed,
The acoustic wave device according to claim 1, wherein the first substrate has the same outer shape as the piezoelectric layer when viewed in the first direction.
When viewed in the plane direction, all the end surfaces of the metal contour outside the piezoelectric layer are exposed,
3. The acoustic wave device according to claim 1, wherein the first substrate has the same outer shape as the metal outside the piezoelectric layer when viewed in the first direction.
When viewed in the plane direction, all end surfaces of the silicon nitride profile outside the piezoelectric layer are exposed,
3. The elastic wave device according to claim 1, wherein the outer shape of said first substrate when viewed in said first direction is the same as the outer shape of silicon nitride outside said piezoelectric layer.
2. From claim 1, wherein the supporting portion seals between the first substrate and the second substrate, and is arranged inside the outline of the second substrate when viewed in the first direction. 6. The elastic wave device according to any one of 5.
The elastic wave device according to claim 6, wherein the functional electrode is arranged in a region surrounded by the support portion when viewed in the first direction.
The elastic wave device according to any one of claims 1 to 7, wherein the metal outside the piezoelectric layer is made of the same metal as the functional electrode.
The functional electrode has one or more first electrode fingers extending in a second direction intersecting the first direction and one or more first electrode fingers extending in a third direction orthogonal to the second direction. The elastic wave device according to any one of claims 1 to 8, comprising one or more second electrode fingers facing each other and extending in the second direction.
The thickness of the piezoelectric layer is such that, of the one or more first electrode fingers and the one or more second electrode fingers, p is the center-to-center distance between adjacent first electrode fingers and second electrode fingers. 10. The elastic wave device according to claim 9, wherein the elastic wave device is 2p or less when
The elastic wave device according to claim 9 or 10, wherein the piezoelectric layer contains lithium niobate or lithium tantalate.
The acoustic wave device according to any one of claims 9 to 11, configured to be able to use thickness shear mode bulk waves.
Let d be the thickness of the piezoelectric layer, and p be the center-to-center distance between adjacent first and second electrode fingers among the one or more first electrode fingers and the one or more second electrode fingers. The elastic wave device according to any one of claims 9 to 11, wherein d/p ≤ 0.5.
The elastic wave device according to claim 13, wherein d/p is 0.24 or less.
The functional electrode has one or more first electrode fingers extending in a second direction intersecting the first direction and one or more first electrode fingers extending in a third direction orthogonal to the second direction. and one or more second electrode fingers facing each other and extending in the second direction, wherein the adjacent first electrode fingers and second electrode fingers overlap each other when viewed in the facing direction. is an excitation region, and MR≤1.75 (d/p )+0.075.
The elastic wave device according to any one of claims 9 to 11, configured to be able to use plate waves.
The piezoelectric layer is lithium niobate or lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate are given by the following formula (1), formula (2), or formula ( 17. The acoustic wave device according to any one of claims 1 to 16, which falls within the range of 3).
(0°±10°, 0° to 20°, arbitrary ψ) Equation (1)
(0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180 °-60° (1-(θ-50) 2 /900) 1/2 ] ~ 180°) Equation (2)
(0°±10°, [180°-30°(1-(ψ-90) 2 /8100) 1/2 ]~180°, arbitrary ψ) Equation (3)
A piezoelectric layer having a first principal surface and a second principal surface opposite to the first principal surface; and a functional electrode provided on at least one of the first principal surface and the second principal surface of the piezoelectric layer. and a first substrate formed at a position overlapping in a first direction, and a second substrate facing the first main surface of the piezoelectric layer, and a bonding step of bonding via a support portion;
a resist forming step of forming a resist on the second substrate after the bonding step;
an etching step of separating the second substrate into individual pieces and etching a part of the first substrate after the resist forming step;
a polishing step of, after the etching step, polishing the main surface of the first substrate opposite to the second substrate to thin the first substrate and singulate it;
including
In the bonding step, a position where none of the piezoelectric layer on the second substrate side of the first substrate, the metal on the outside of the piezoelectric layer, and the silicon nitride on the outside of the piezoelectric layer are present is the acoustic wave device. It is patterned so that it becomes a boundary to be singulated,
In the resist forming step, the resist is smaller than the area surrounded by the boundary when viewed in the first direction, and the outer shape of the resist is inside the area surrounded by the boundary when viewed in the first direction. ,
In the etching step, at least one of the piezoelectric layer on the second substrate side of the first substrate, the metal on the outside of the piezoelectric layer, and the silicon nitride on the outside of the piezoelectric layer is singulated. A method of manufacturing an acoustic wave device, which serves as a mask for regulating the outer shape of the first substrate.
A mask for regulating the outer shape of the first substrate in which the end face of the outer shape of the piezoelectric layer is entirely exposed in the etching step, and the piezoelectric layer on the side of the second substrate of the first substrate is separated into individual pieces. The method for manufacturing an elastic wave device according to claim 18, wherein:
In the etching step, all the end surfaces of the outer shape of the metal outside the piezoelectric layer are exposed, and the metal outside the piezoelectric layer serves as a mask for regulating the outer shape of the individualized first substrate. 19. The method of manufacturing an elastic wave device according to claim 18.
A mask for regulating the outer shape of the first substrate in which all the end surfaces of the outer shape of the silicon nitride outside the piezoelectric layer are exposed in the etching step, and the silicon nitride outside the piezoelectric layer is separated into individual pieces. The method for manufacturing an elastic wave device according to claim 18, wherein: