JP7373301B2 - Acoustic wave devices, filters and multiplexers - Google Patents

Description

The present invention relates to an acoustic wave device, a filter, and a multiplexer, and more particularly, to an acoustic wave device, a filter, and a multiplexer in which a plurality of substrates are bonded together.

BACKGROUND ART Acoustic wave devices are known in which a piezoelectric substrate having an acoustic wave element provided on the upper surface is bonded to a support substrate, and another substrate is mounted on the substrate (for example, Patent Documents 1 and 2).

JP2017-204827A JP2017-157922A

When a connection layer such as a bump is used to mount a substrate on a composite substrate to which substrates having different coefficients of linear expansion are bonded, thermal stress is applied to the connection layer due to thermal distortion of the composite substrate.

The present invention was made in view of the above problems, and an object of the present invention is to suppress thermal stress.

The present invention includes a first substrate having a first surface, a linear expansion coefficient of which is directly or indirectly bonded to a surface of the first substrate opposite to the first surface, and whose linear expansion coefficient is smaller than the linear expansion coefficient of the first substrate. a second substrate that is thicker than the first substrate and has a coefficient of linear expansion, and a second surface that is provided on the first surface and faces the first surface with a gap in between; a third substrate having a coefficient of linear expansion closer to that of the second substrate; and a third substrate directly or indirectly joined to a surface opposite to the second surface of the third substrate; a fourth substrate having a linear expansion coefficient larger than the linear expansion coefficient and closer to the linear expansion coefficient of the first substrate than the linear expansion coefficient of the third substrate and thinner than the third substrate; The present invention is an acoustic wave device including an acoustic wave element provided on at least one of two surfaces, and a connection layer connecting the first surface and the second surface.

In the above structure, the connection layer may be a bump .

In the above structure, the connection layer may be a sealing part that seals the gap .

In the above configuration, the first substrate and the fourth substrate are piezoelectric substrates, the acoustic wave element is provided on the first surface, and the acoustic wave element includes a pair of comb-shaped electrodes having a plurality of electrode fingers. , the coefficient of linear expansion of the second substrate in the direction in which the plurality of electrode fingers are arranged is smaller than the coefficient of linear expansion of the first substrate in the direction, and the coefficient of linear expansion of the third substrate in the direction is smaller than that of the first substrate in the direction. The linear expansion coefficient may be smaller than the coefficient of linear expansion in the direction of the fourth substrate .

The present invention provides a first substrate having a first surface, a linear expansion coefficient that is directly or indirectly bonded to a surface opposite to the first surface of the first substrate, and that has a linear expansion coefficient different from that of the first substrate. a second substrate having a linear expansion coefficient, and a second surface provided on the first surface and facing the first surface with a gap therebetween, the linear expansion coefficient of the second substrate is greater than the linear expansion coefficient of the first substrate. a third substrate having a coefficient of linear expansion close to that of the first substrate; A fourth substrate having a linear expansion coefficient close to a linear expansion coefficient of , an acoustic wave element provided on at least one of the first surface and the second surface, and the first surface and the second surface are connected. , and a connection layer that is a sealing portion that seals the gap .

In the above configuration, the first substrate and the fourth substrate are piezoelectric substrates, the acoustic wave element is provided on the first surface, and the acoustic wave element includes a pair of comb-shaped electrodes having a plurality of electrode fingers. , the coefficient of linear expansion of the second substrate in the direction in which the plurality of electrode fingers are arranged is smaller than the coefficient of linear expansion of the first substrate in the direction, and the coefficient of linear expansion of the third substrate in the direction is smaller than that of the first substrate in the direction. The linear expansion coefficient may be smaller than the coefficient of linear expansion in the direction of the fourth substrate .

In the above configuration, the first substrate may be thinner than the second substrate, and the fourth substrate may be thinner than the third substrate.

In the above structure, the first substrate and the fourth substrate may be a lithium tantalate substrate or a lithium niobate substrate .

In the above configuration , the acoustic wave element may include a piezoelectric thin film resonator provided on the second surface .

In the above configuration, the first substrate and the fourth substrate may have the same material as their main component, and the second substrate and the third substrate may have the same material as their main component.

In the above configuration, the thickness of the first substrate is T1, the thickness of the second substrate is T2, the thickness of the third substrate is T3, the thickness of the fourth substrate is T4, and T1/T2=R1. , T4/T3=R2, then |R1−R2|/|R1+R2| can be configured to be 0.1 or less .

The present invention is a filter including the above elastic wave device .

According to the present invention, thermal stress can be suppressed.

FIG. 1 is a cross-sectional view of an acoustic wave device according to Example 1. 2(a) is a plan view of the acoustic wave element 12 in Example 1, and FIG. 2(b) is a sectional view of the acoustic wave element 22. 3(a) to 3(c) are cross-sectional views (part 1) showing the method for manufacturing the acoustic wave device according to the first embodiment. FIGS. 4(a) to 4(c) are cross-sectional views (part 2) showing the method for manufacturing the acoustic wave device according to the first embodiment. FIGS. 5A and 5B are cross-sectional views (part 3) showing the method for manufacturing the acoustic wave device according to the first embodiment. FIG. 6 is a cross-sectional view of an acoustic wave device according to Comparative Example 1. FIG. 7 is a cross-sectional view of an acoustic wave device according to Modification 1 of Example 1. FIG. 8(a) is a sectional view of an acoustic wave device according to a second modification of the first embodiment, and FIG. 8(b) is a plan view. FIG. 9 is a cross-sectional view of an acoustic wave device according to Example 2. 10(a) is a circuit diagram of a filter according to a second embodiment, and FIG. 10(b) is a circuit diagram of a duplexer according to a first modification of the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of an acoustic wave device according to Example 1. The stacking direction of the substrates 10 and 20 is the Z direction, the propagation direction of the elastic wave of the acoustic wave element 12 is the X direction, and the direction orthogonal to the X direction is the Y direction.

As shown in FIG. 1, the substrate 10 includes a support substrate 10a and a piezoelectric substrate 10b. The support substrate 10a is, for example, a sapphire substrate, an alumina substrate, a spinel substrate, a quartz substrate, a crystal substrate, or a silicon substrate. The piezoelectric substrate 10b is, for example, a lithium tantalate substrate or a lithium niobate substrate. The piezoelectric substrate 10b is bonded to the upper surface of the support substrate 10a. The linear expansion coefficient α2 of the support substrate 10a is smaller than the linear expansion coefficient α1 of the piezoelectric substrate 10b. The thicknesses of the support substrate 10a and the piezoelectric substrate 10b are T2 and T1, respectively. The piezoelectric substrate 10b and the support substrate 10a may be directly bonded, or may be bonded indirectly through an insulating layer such as silicon oxide or aluminum nitride.

An acoustic wave element 12, wiring 14, and an annular metal layer 32 are provided on the upper surface of the substrate 10. The annular metal layer 32 is provided so as to surround the acoustic wave element 12 and the wiring 14 in plan view. Terminals 18 are provided on the lower surface of the substrate 10. The terminal 18 is a foot pad for connecting the acoustic wave elements 12 and 22 to the outside. A via wiring 16 is provided that penetrates the substrate 10. The via wiring 16 electrically connects the terminal 18 and the wiring 14. The wiring 14, the via wiring 16, and the terminal 18 are, for example, metal layers such as a copper layer, an aluminum layer, a platinum layer, or a gold layer. The annular metal layer 32 is, for example, a nickel layer.

A substrate 20 is mounted on the substrate 10. The substrate 20 includes a substrate 20a and a substrate 20b. The substrate 20a is, for example, a sapphire substrate, an alumina substrate, a spinel substrate, a quartz substrate, a crystal substrate, or a silicon substrate. The substrate 20b is, for example, a lithium tantalate substrate or a lithium niobate substrate. Substrate 20b is bonded to the upper surface of substrate 20a. The linear expansion coefficient α4 of the substrate 20b is larger than the linear expansion coefficient α3 of the substrate 20a. The thicknesses of substrate 20a and substrate 20b are T3 and T4, respectively.

An acoustic wave element 22 and wiring 24 are provided on the lower surface of the substrate 20. The wiring 24 is, for example, a metal layer such as a copper layer, an aluminum layer, a platinum layer, or a gold layer. The board 20 is flip-chip mounted (face-down mounted) on the board 10 via bumps 28. Bumps 28 are, for example, gold bumps, solder bumps, or copper bumps. Bump 28 connects to wirings 14 and 24.

A sealing section 30 is provided on the substrate 10 so as to surround the substrate 20. The sealing portion 30 is, for example, a metal layer such as solder (tin-silver, tin, or tin-silver-copper) or an insulating layer such as resin. The sealing part 30 is joined to the annular metal layer 32. A flat lid 36 is provided on the upper surface of the substrate 20 and the upper surface of the sealing section 30. The lid 36 is, for example, a metal plate such as a Kovar plate or an insulating plate. A protective film 38 is provided to cover the lid 36 and the sealing part 30. The protective film 38 is a metal film such as a nickel film or an insulating film.

The acoustic wave element 12 faces the substrate 20 with a gap 26 in between. The acoustic wave element 22 faces the piezoelectric substrate 10b with a gap 26 in between. Acoustic wave elements 12 and 22 are sealed by sealing section 30, substrate 10, substrate 20, and lid 36. Bump 28 is surrounded by void 26. The terminal 18 is electrically connected to the acoustic wave element 12 via the via wiring 16 and the wiring 14, and further electrically connected to the acoustic wave element 22 via the bump 28 and the wiring 24.

The thicknesses T2 and T3 of the support substrate 10a and the substrate 20a are, for example, 50 μm to 300 μm. The thicknesses T1 and T4 of the piezoelectric substrate 10b and the substrate 20b are, for example, from 0.5 μm to 30 μm, which is, for example, less than the wavelength of the elastic wave. The thickness of the bump 28 is, for example, 10 μm to 20 μm, and the diameter is, for example, 10 μm to 200 μm. The thickness of the wirings 14 and 24 to which the bumps 28 are bonded is, for example, 0.1 μm to 5 μm.

2(a) is a plan view of the acoustic wave element 12 in Example 1, and FIG. 2(b) is a sectional view of the acoustic wave element 22. As shown in FIG. 2(a), the acoustic wave element 12 is a surface acoustic wave resonator. An IDT (Interdigital Transducer) 40 and a reflector 42 are formed on the piezoelectric substrate 10b of the substrate 10. The IDT 40 has a pair of comb-shaped electrodes 40a facing each other. The comb-shaped electrode 40a has a plurality of electrode fingers 40b and a bus bar 40c connecting the plurality of electrode fingers 40b. Reflectors 42 are provided on both sides of the IDT 40.

The IDT 40 excites surface acoustic waves in the piezoelectric substrate 10b. The wavelength of the elastic wave is approximately equal to the pitch of the electrode fingers 40b of one of the pair of comb-shaped electrodes 40a. That is, the wavelength of the elastic wave is approximately equal to twice the pitch of the electrode fingers 40b of the pair of comb-shaped electrodes 40a. The IDT 40 and the reflector 42 are formed of, for example, an aluminum film, a copper film, or a molybdenum film. A protective film or a temperature compensation film may be provided on the piezoelectric substrate 10b so as to cover the IDT 40 and the reflector 42. The direction in which the electrode fingers 40b are arranged is the X direction, which is the propagation direction of elastic waves. The direction in which the electrode fingers 40b extend is the Y direction.

As shown in FIG. 2(b), the acoustic wave element 22 is a piezoelectric thin film resonator. A piezoelectric film 46 is provided on the substrate 20. A lower electrode 44 and an upper electrode 48 are provided so as to sandwich the piezoelectric film 46 therebetween. A gap 45 is formed between the lower electrode 44 and the substrate 20. A region where the lower electrode 44 and the upper electrode 48 face each other with at least a portion of the piezoelectric film 46 in between is a resonance region 47 . In the resonance region 47, the lower electrode 44 and the upper electrode 48 excite elastic waves in the thickness longitudinal vibration mode within the piezoelectric film 46. The substrate 20 is, for example, a sapphire substrate, a spinel substrate, an alumina substrate, a glass substrate, a crystal substrate, or a silicon substrate. The lower electrode 44 and the upper electrode 48 are, for example, metal films such as ruthenium films. The piezoelectric film 46 is, for example, an aluminum nitride film. Instead of the void 45, an acoustic reflection film that reflects elastic waves may be provided.

Acoustic wave elements 12 and 22 include electrodes that excite elastic waves. For this reason, the elastic wave elements 12 and 22 are covered with a void 26 so as not to limit the elastic waves.

[Production method of Example 1]
FIGS. 3(a) to 5(b) are cross-sectional views showing a method of manufacturing an acoustic wave device according to Example 1. FIG. As shown in FIG. 3A, a substrate 20a is bonded onto a substrate 20b using, for example, a surface activation method at room temperature. When the substrate 20b is a lithium tantalate substrate or a lithium niobate substrate, it is not necessary to perform a polarization process to align the polarization directions within the crystal.

As shown in FIG. 3(b), an acoustic wave element 22 and wiring 24 are formed on a substrate 20a. As shown in FIG. 3(c), bumps 28 are formed on the wiring 24. The substrate 20b is made to have a desired thickness using, for example, a CMP (Chemical Mechanical Polishing) method.

As shown in FIG. 4A, a piezoelectric substrate 10b is bonded to a support substrate 10a at room temperature using, for example, a surface activation method. When the piezoelectric substrate 10b is a lithium tantalate substrate or a lithium niobate substrate, polarization treatment is performed. The piezoelectric substrate 10b is made to have a desired thickness using, for example, a CMP method. Via wiring 16 is formed on piezoelectric substrate 10b and support substrate 10a. The via wiring 16 does not need to penetrate the support substrate 10a.

As shown in FIG. 4(b), an acoustic wave element 12 and wiring 14 are formed on a piezoelectric substrate 10b. As shown in FIG. 4(c), the support substrate 10a is made to have a desired thickness using, for example, the CMP method. As a result, the via wiring 16 is exposed on the lower surface of the support substrate 10a. Terminals 18 are formed on the lower surface of the support substrate 10a.

As shown in FIG. 5A, the substrate 20 is flip-chip mounted onto the substrate 10 via bumps 28. The substrates 10 and 20 are heated, for example, from 50° C. to 250° C., and while applying ultrasonic waves to the substrate 20, the substrates 10 and 20 are pressed in a direction toward each other. As a result, the bump 28 and the wiring 14 are bonded to each other. The acoustic wave elements 12 and 22 face each other with a gap 26 in between.

As shown in FIG. 5(b), a sealing portion 30 is formed to surround the substrate 20. The sealing portion 30 is joined to the annular metal layer 32 . A lid 36 is provided on the sealing part 30 and the substrate 20. The lid 36 may not be provided. When the sealing part 30 is made of solder or resin, the sealing part 30 is formed by heating from 200°C to 300°C. After that, the substrate 10 is cut. Thereby, the acoustic wave device is separated into pieces. A protective film 38 surrounding the sealing part 30 and the lid 36 is formed. In this way, the acoustic wave device shown in FIG. 1 is manufactured.

[Comparative example 1]
FIG. 6 is a cross-sectional view of an acoustic wave device according to Comparative Example 1. As shown in FIG. 6, in the acoustic wave device of Comparative Example 1, the substrate 20 is not provided with the substrate 20b. The other configurations are the same as in the first embodiment.

A sapphire substrate and a lithium tantalate substrate are used as the support substrate 10a and the piezoelectric substrate 10b, and a silicon substrate is used as the substrate 20. At this time, the linear expansion coefficient of the sapphire substrate is 7 ppm/°C, and the linear expansion coefficient of the lithium tantalate substrate in the X-axis direction is 16 ppm/°C. The coefficient of linear expansion of the silicon substrate is 2 ppm/°C.

When the temperature rises in the step of bonding the bumps 28 in FIG. 5(a) and in the step of forming the sealing part 30 in FIG. 5(b), the center of the substrate 10 warps toward the substrate 20 as shown by the broken line 60 compared to the periphery. . On the other hand, the substrate 20 hardly warps as indicated by the broken line 62. At this time, thermal stress is applied to the bump 28 in the vertical direction (Z direction). After that, when the temperature returns to room temperature, the warpage of the substrate 10 becomes smaller, and thermal stress is applied to the bumps 28 in the vertical direction in the opposite direction to that at high temperature. This may cause peeling of the bumps 28 or the like.

According to Example 1, the support substrate 10a (second substrate) is directly or indirectly joined to the lower surface (the surface opposite to the first surface) of the piezoelectric substrate 10b (first substrate). The substrate 20a (third substrate) is provided on the upper surface (first surface) of the piezoelectric substrate 10b, and has a lower surface (second surface) facing the upper surface of the piezoelectric substrate 10b with a gap 26 in between. The substrate 20b (fourth substrate) is directly or indirectly joined to the upper surface (the surface opposite to the second surface) of the substrate 20a. The acoustic wave elements 12 and 22 are provided on at least one of the upper surface of the piezoelectric substrate 10b and the lower surface of the substrate 20a. Bumps 28 (connection layer) connect the top surface of piezoelectric substrate 10b and the bottom surface of substrate 20a.

At this time, unlike the linear expansion coefficient α1 of the piezoelectric substrate 10b and the linear expansion coefficient α2 of the support substrate 10a, the linear expansion coefficient α3 of the substrate 20a is smaller than the linear expansion coefficient α1 of the piezoelectric substrate 10b than the linear expansion coefficient α2 of the support substrate 10a. The linear expansion coefficient α4 of the substrate 20b is closer to the linear expansion coefficient α1 of the piezoelectric substrate 10b than the linear expansion coefficient α3 of the substrate 20a. That is, |α3−α1|>|α3−α2| and |α4−α2|>|α4−α1|.

As a result, as shown by broken lines 60 and 62 in FIG. 1, the difference between the warpage of the substrate 10 and the warpage of the substrate 20 is smaller than the difference between the warpage of the substrate 10 and the warp of the substrate 20 in Comparative Example 1. Therefore, the stress applied to the bumps 28 is reduced, and deterioration such as peeling of the bumps 28 can be suppressed. |α3−α1|/2>|α3−α2| is preferable, |α3−α1|/5>|α3−α2| is more preferable, and it is even more preferable that α3 and α1 are substantially equal. |α4-α2|/2>|α4-α1| is preferable, |α4-α2|/5>|α4-α1| is more preferable, and it is even more preferable that α4 and α2 are substantially equal.

When the first substrate is the piezoelectric substrate 10b and the elastic wave element 12 is a surface acoustic wave element, the linear expansion coefficient α2 of the support substrate 10a in the X direction is made smaller than the linear expansion coefficient of the piezoelectric substrate 10b in the X direction. This reduces the frequency temperature coefficient of the acoustic wave element 12. However, as in Comparative Example 1, stress is applied to the bumps 28. Therefore, the linear expansion coefficient of the substrate 20a in the X direction is made smaller than the linear expansion coefficient of the substrate 20b in the X direction. This reduces the difference between the warpage of the substrate 10 and the warpage of the substrate 20, and the stress applied to the bumps 28 can be suppressed.

Piezoelectric substrate 10b is thinner than support substrate 10a, and substrate 20b is thinner than substrate 20a. This reduces the difference between the warpage of the substrate 10 and the warpage of the substrate 20, and the stress applied to the bumps 28 can be suppressed. The thickness T1 of the piezoelectric substrate 10b is preferably 1/2 or less, more preferably 1/5 or less, and even more preferably 1/10 or less of the thickness T2 of the support substrate 10a. If T1 is too small, there is no problem that the substrate 10 will warp. Therefore, T1 is preferably 1/100 or more of T2, more preferably 1/20 or more. T4 is preferably 1/2 or less of T3, more preferably 1/5 or less, and even more preferably 1/10 or less. T4 is preferably 1/100 or more of T3, more preferably 1/20 or more.

When T1/T2=R1 and T4/T3=R2, |R1−R2|/|R1+R| is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.1 or less.

It is preferable that the piezoelectric substrate 10b and the substrate 20b have the same material as their main component, and the support substrate 10a and the substrate 20a have the same material as their main component. This makes α1 and α4 substantially equal, and α2 and α3 substantially equal. The main component of the substrate means that the substrate may contain impurities intentionally or unintentionally other than the main component, for example, if the total concentration of one or more elements contained in the main component is 50 atoms. % or more.

When the acoustic wave element 22 is a piezoelectric thin film resonator, the substrate 20a can be appropriately selected from an insulating substrate or a semiconductor substrate. Therefore, the material of the substrate 20a can be appropriately selected so that the linear expansion coefficient of the substrate 20a is closer to that of the support substrate 10a than that of the substrate 20b.

[Modification 1 of Example 1]
FIG. 7 is a cross-sectional view of an acoustic wave device according to Modification 1 of Example 1. As shown in FIG. 7, the substrate 10 is mounted on the substrate 20. The substrate 20 includes a substrate 20a bonded onto a substrate 20b. An acoustic wave element 22, wiring 24, and annular metal layer 32 are provided on the substrate 20a. A via wiring 16 is provided that penetrates the substrate 20. Terminals 18 are provided on the lower surface of the substrate 20. A support substrate 10a is bonded onto the piezoelectric substrate 10b. An acoustic wave element 12 and wiring 14 are provided on the lower surface of the piezoelectric substrate 10b. Bump 28 is joined to interconnects 14 and 24. A sealing section 30 is provided to surround the substrate 10. The other configurations are the same as those in Example 1, and their explanation will be omitted.

The substrate 10 may be mounted on the substrate 20 as in the first modification of the first embodiment. As shown by broken lines 60 and 62, the difference between the warpage of the substrate 10 and the warpage of the substrate 20 is smaller than the difference between the warpage of the substrate 10 and the warp of the substrate 20 of Comparative Example 1. Therefore, the stress applied to the bumps 28 can be suppressed.

[Modification 2 of Example 1]
FIG. 8(a) is a sectional view of an acoustic wave device according to a second modification of the first embodiment, and FIG. 8(b) is a plan view. In FIG. 8(b), the sealing portion 30a is illustrated. As shown in FIGS. 8(a) and 8(b), the planar shapes of the substrates 10 and 20 are almost the same. A sealing portion 30a is provided between the substrates 10 and 20 at the periphery of the substrates 10 and 20. The sealing portion 30a is, for example, a metal layer such as a copper layer, and seals the acoustic wave elements 12 and 22 in the gap 26. The bump 28 and the sealing portion 30a function as a connection layer. The other configurations are the same as in Example 1, and their explanation will be omitted. As in the second modification of the first embodiment, the sealing portion 30a may function as a connection layer in addition to or instead of the bump 28. In the second modification of the first embodiment, deterioration such as peeling of the sealing portion 30a due to thermal stress can be suppressed.

FIG. 9 is a cross-sectional view of an acoustic wave device according to Example 2. As shown in FIG. 9, in the substrate 10, a support substrate 10a is bonded onto a piezoelectric substrate 10c, and a piezoelectric substrate 10b is bonded onto the support substrate 10a. An acoustic wave element 12 and wiring 14 are provided on the upper surface of the piezoelectric substrate 10b. Terminals 18 are provided on the lower surface of the piezoelectric substrate 10c. A via wiring 16 penetrating the substrate 10 electrically connects the wiring 14 and the terminal 18.

In the substrate 20, a support substrate 20a is bonded onto a piezoelectric substrate 20b, and a piezoelectric substrate 20c is bonded onto the support substrate 20a. An acoustic wave element 22 and wiring 24 are provided on the lower surface of the piezoelectric substrate 20b. Wirings 14 and 24 are electrically connected by bumps 28. A sealing portion 30b is provided to surround the substrate 20. The sealing portion 30b seals the acoustic wave elements 12 and 22 in the gap 26. The sealing portion 30b is made of resin such as epoxy resin, for example. The sealing portion 30b may be made of metal. The other configurations are the same as those of the first embodiment and its modification, and the description thereof will be omitted.

According to the second embodiment, the acoustic wave element 12 (first acoustic wave element) is provided on the upper surface (first surface) of the piezoelectric substrate 10b (first piezoelectric substrate), and has a plurality of electrode fingers 40b (first electrode fingers). ) is provided with a pair of comb-shaped electrodes 40a. The support substrate 10a (first substrate) is directly or indirectly bonded to the lower surface (the opposite surface to the first surface) of the piezoelectric substrate 10b, and is linearly expanded in the direction in which the electrode fingers 40b are arranged (first direction). The coefficient is smaller than the linear expansion coefficient of the piezoelectric substrate 10b in the first direction. The piezoelectric substrate 10c (second substrate) is directly or indirectly bonded to the surface of the supporting substrate 10a opposite to the piezoelectric substrate 10b, and has a linear expansion coefficient in the first direction of the supporting substrate 10a in the first direction. greater than the expansion coefficient.

The piezoelectric substrate 20b (second piezoelectric substrate) is mounted on the upper surface of the piezoelectric substrate 10b, and the lower surface (second surface) of the piezoelectric substrate 20b faces the upper surface of the piezoelectric substrate 10b with a gap 26 in between. The acoustic wave element 22 (second acoustic wave element) is provided on the lower surface of the piezoelectric substrate 20b, and includes a pair of comb-shaped electrodes 40a having a plurality of electrode fingers 40b (second electrode fingers). The supporting substrate 20a is directly or indirectly joined to the surface opposite to the lower surface of the piezoelectric substrate 20b, and the linear expansion coefficient in the second direction in which the electrode fingers 40b are arranged is the linear expansion coefficient of the piezoelectric substrate 20b in the second direction. smaller. The piezoelectric substrate 20c is directly or indirectly joined to the surface of the support substrate 20a opposite to the piezoelectric substrate 20b side, and has a linear expansion coefficient in the second direction larger than that of the support substrate 20a in the second direction.

Thereby, the piezoelectric substrate 10c compensates for the warpage of the substrate 10 caused by the difference in linear expansion coefficient between the support substrate 10a and the piezoelectric substrate 10b. The piezoelectric substrate 20c compensates for the warpage of the substrate 20 caused by the difference in linear expansion coefficient between the support substrate 20a and the piezoelectric substrate 20b. Therefore, stress applied to the bumps 28 (connection layer) can be suppressed.

It is preferable that the difference in linear expansion coefficients between the piezoelectric substrates 10b and 10c is smaller than the difference in linear expansion coefficients between the supporting substrate 10a and the piezoelectric substrate 10b. It is preferable that the difference in linear expansion coefficients between the piezoelectric substrates 12b and 12c is smaller than the difference in linear expansion coefficients between the supporting substrate 12a and the piezoelectric substrate 12b. Thereby, stress applied to the bumps 28 can be suppressed.

The difference in linear expansion coefficient between the support substrate 20a and the piezoelectric substrate 10b and the difference in the linear expansion coefficient between the support substrate 20a and the piezoelectric substrate 10c are both smaller than the difference in the linear expansion coefficient between the support substrates 20a and 10a. preferable. Difference in linear expansion coefficient between piezoelectric substrates 20b and 10b, difference in linear expansion coefficient between piezoelectric substrates 20b and 10c, difference in linear expansion coefficient between piezoelectric substrates 20c and 10b, and linear expansion coefficient between piezoelectric substrates 20c and 10c. Both of the differences are preferably smaller than the difference in linear expansion coefficient between the piezoelectric substrate 20b and the support substrate 10a, and the difference in the linear expansion coefficient between the piezoelectric substrate 20c and the support substrate 10a. Thereby, stress applied to the bumps 28 can be suppressed.

The piezoelectric substrates 10b and 10c preferably have the same material as their main component, and the piezoelectric substrates 20b and 20c preferably have the same material as their main component. It is preferable that the thickness of the piezoelectric substrate 10b and the thickness of the piezoelectric substrate 10c are approximately equal. It is preferable that the thickness of the piezoelectric substrate 20b and the thickness of the piezoelectric substrate 20c are approximately equal. It is preferable that the thickness of piezoelectric substrates 10b and 10c and the thickness of piezoelectric substrates 20b and 20c are approximately equal. It is preferable that the supporting substrates 10a and 20a have the same material as a main component. It is preferable that the thickness of the support substrate 10a and the thickness of the support substrate 20a are substantially equal to each other. With these, the stress applied to the bumps 28 can be suppressed.

It is preferable that the thickness of the piezoelectric substrate 10b and the thickness of the piezoelectric substrate 10c are each thinner than the support substrate 10a. It is preferable that the thickness of the piezoelectric substrate 20b and the thickness of the piezoelectric substrate 20c are each thinner than the support substrate 20a. This reduces the difference between the warpage of the substrate 10 and the warpage of the substrate 20, and the stress applied to the bumps 28 can be suppressed. The thickness of each of the piezoelectric substrates 10b and 10c is preferably 1/2 or less, more preferably 1/5 or less, and even more preferably 1/10 or less of the thickness of the support substrate 10a. If the piezoelectric substrate 10b is too thin, the substrate 10 will not warp. Therefore, the thickness of the piezoelectric substrates 10b and 10c is preferably 1/100 or more, more preferably 1/20 or more of the thickness of the support substrate 10a. Similarly, the thickness of the piezoelectric substrates 20b and 20c is preferably 1/2 or less, more preferably 1/5 or less, and even more preferably 1/10 or less of the thickness of the support substrate 20a. The thickness of each of the piezoelectric substrates 20b and 20c is preferably 1/100 or more, more preferably 1/20 or more of the thickness of the support substrate 20a.

It is preferable that the arrangement direction of the electrode fingers 40b of the acoustic wave element 12 and the arrangement direction of the electrode fingers 40b of the acoustic wave element 22 are substantially parallel. Thereby, the difference between the warpage of the substrate 10 and the warpage of the substrate 20 can be reduced. Therefore, the stress applied to the bumps 28 can be reduced. The angle between the arrangement direction of the electrode fingers 40b of the acoustic wave element 12 and the arrangement direction of the electrode fingers 40b of the acoustic wave element 22 is preferably 45° or less, more preferably 30° or less.

As in the second modification of the first embodiment, the substrates 10 and 20 may be connected by a sealing portion 30a.

In the first and second embodiments and their modifications, the piezoelectric thin film resonator is used as the acoustic wave element 22, but the acoustic wave element 22 may be a surface acoustic wave resonator. Although an example of the acoustic wave device 22 has been described as a functional device provided on the lower surface of the substrate 20, the functional device may be a passive device such as an inductor or a capacitor, an active device including a transistor, or a MEMS (Micro Electro Mechanical Systems) device. .

Example 3 is an example of a filter and a duplexer. FIG. 10(a) is a circuit diagram of a filter according to the second embodiment. As shown in FIG. 10(a), one or more series resonators S1 to S4 are connected in series between the input terminal T1 and the output terminal T2. One or more parallel resonators P1 to P4 are connected in parallel between the input terminal T1 and the output terminal T2. The filter of the second embodiment may be formed of the acoustic wave elements 12 and/or 22. The number of series resonators and parallel resonators can be set as appropriate. Although the filter has been described using a ladder filter as an example, the filter may be a multimode filter.

FIG. 10(b) is a circuit diagram of a duplexer according to a first modification of the second embodiment. As shown in FIG. 10(b), a transmission filter 50 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 52 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 50 passes a signal in the transmission band among the high frequency signals inputted from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies. The reception filter 52 passes a signal in the reception band among the high-frequency signals inputted from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals at other frequencies. At least one of the transmission filter 50 and the reception filter 52 can be the filter of the second embodiment. Alternatively, the transmission filter 50 may be formed of the elastic wave element 12 and the reception filter 52 may be formed of the elastic wave element 22.

Although a duplexer has been described as an example of a multiplexer, a triplexer or a quadplexer may also be used.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention as described in the claims. Changes are possible.

10a Support substrate 10b Piezoelectric substrate 12, 22 Acoustic wave element 14, 24 Wiring 16a, 16b Via wiring 17a-17c Metal layer 18 Terminal 20 Substrate 26 Gap 28a, 28c Bump 30 Sealing part 32 Annular metal layer 36 Lid 50 Transmission filter 52 Receive filter

Claims (12)

a first substrate having a first surface;
a second substrate that is directly or indirectly bonded to a surface opposite to the first surface of the first substrate, has a linear expansion coefficient smaller than that of the first substrate , and is thicker than the first substrate; and,
A second surface is provided on the first surface and faces the first surface with a gap in between, and has a linear expansion coefficient closer to that of the second substrate than that of the first substrate. a third substrate;
It is directly or indirectly bonded to the surface of the third substrate opposite to the second surface, and has a linear expansion coefficient greater than that of the third substrate and less than that of the first substrate. a fourth substrate having a linear expansion coefficient close to the expansion coefficient and being thinner than the third substrate ;
an acoustic wave element provided on at least one of the first surface and the second surface;
a connection layer connecting the first surface and the second surface;
An elastic wave device equipped with The acoustic wave device according to claim 1 , wherein the connection layer is a bump. The acoustic wave device according to claim 1 , wherein the connection layer is a sealing part that seals the gap. The first substrate and the fourth substrate are piezoelectric substrates,
the acoustic wave element is provided on the first surface,
The acoustic wave element includes a pair of comb-shaped electrodes having a plurality of electrode fingers,
The linear expansion coefficient of the second substrate in the direction in which the plurality of electrode fingers are arranged is smaller than the linear expansion coefficient of the first substrate in the direction,
The acoustic wave device according to any one of claims 1 to 3, wherein the linear expansion coefficient of the third substrate in the direction is smaller than the linear expansion coefficient of the fourth substrate in the direction. a first substrate having a first surface;
a second substrate that is directly or indirectly joined to a surface opposite to the first surface of the first substrate and has a linear expansion coefficient different from that of the first substrate;
A second surface is provided on the first surface and faces the first surface with a gap in between, and has a linear expansion coefficient closer to that of the second substrate than that of the first substrate. a third substrate;
A fourth substrate that is directly or indirectly bonded to a surface opposite to the second surface of the third substrate and has a linear expansion coefficient closer to that of the first substrate than that of the third substrate. A substrate and
an acoustic wave element provided on at least one of the first surface and the second surface;
a connection layer that is a sealing part that connects the first surface and the second surface and seals the gap;
An elastic wave device equipped with The first substrate and the fourth substrate are piezoelectric substrates,
the acoustic wave element is provided on the first surface,
The acoustic wave element includes a pair of comb-shaped electrodes having a plurality of electrode fingers,
The linear expansion coefficient of the second substrate in the direction in which the plurality of electrode fingers are arranged is smaller than the linear expansion coefficient of the first substrate in the direction,
The acoustic wave device according to claim 5 , wherein the linear expansion coefficient of the third substrate in the direction is smaller than the linear expansion coefficient of the fourth substrate in the direction. the first substrate is thinner than the second substrate;
The acoustic wave device according to claim 6 , wherein the fourth substrate is thinner than the third substrate. The acoustic wave device according to any one of claims 4, 6 and 7, wherein the first substrate and the fourth substrate are a lithium tantalate substrate or a lithium niobate substrate. The acoustic wave device according to any one of claims 4, 6, 7, and 8, wherein the acoustic wave element includes a piezoelectric thin film resonator provided on the second surface. The first substrate and the fourth substrate have the same material as a main component,
The acoustic wave device according to any one of claims 1 to 9 , wherein the second substrate and the third substrate are made of the same material as a main component. The thickness of the first substrate is T1, the thickness of the second substrate is T2, the thickness of the third substrate is T3, and the thickness of the fourth substrate is T4, T1/T2=R1, T4/T3. The elastic wave device according to any one of claims 1 to 10, wherein |R1-R2|/|R1+R2| is 0.1 or less when =R2. A filter comprising the elastic wave device according to any one of claims 1 to 11 .

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