JP2020184703A - Acoustic wave device, filter, and multiplexer - Google Patents

Abstract

To suppress thermal stress.SOLUTION: An acoustic wave device comprises: a first substrate having a first surface; a second substrate which is directly or indirectly bonded to a surface, of the first substrate, that is opposite to the first surface, and which has a linear expansion coefficient different from that of the first substrate; a third substrate which is provided above the first surface and has a second surface facing the first surface across a gap, and which has a linear expansion coefficient closer to that of the second substrate than that of the first substrate; a fourth substrate which is directly or indirectly bonded to a surface, of the third substrate, that is opposite to the second surface, and which has a linear expansion coefficient closer to that of the first substrate than that of the third substrate; an acoustic wave element which is provided on at least one of the first surface and the second surface; and a connection layer connecting the first surface to the second surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to elastic wave devices, filters and multiplexers, for example, elastic wave devices, filters and multiplexers in which a plurality of substrates are bonded.

There is known an elastic wave device in which another substrate is mounted on a substrate in which a piezoelectric substrate provided with an elastic wave element on the upper surface is bonded to a support substrate (for example, Patent Documents 1 and 2).

JP-A-2017-204827 JP-A-2017-157922

When a substrate is mounted using a connecting layer such as a bump on a composite substrate to which substrates having different linear expansion coefficients are joined, thermal stress is applied to the connecting layer due to thermal strain of the composite substrate.

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

In the present invention, a first substrate having a first surface is directly or indirectly joined to a surface of the first substrate opposite to the first surface, and linear expansion different from the coefficient of linear expansion of the first substrate. It has a second substrate having a coefficient and a second surface provided on the first surface and facing the first surface with a gap in between, and the linear expansion of the second substrate is based on the linear expansion coefficient of the first substrate. The third substrate having a coefficient of linear expansion close to the coefficient is directly or indirectly bonded to the surface of the third substrate opposite to the second surface, and the first substrate is based on the coefficient of linear expansion of the third substrate. A fourth substrate having a coefficient of linear expansion close to the coefficient of linear expansion of the above, an elastic 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 to each other. An elastic wave device comprising a connecting layer.

In the above configuration, the first substrate and the fourth substrate are piezoelectric substrates, the elastic wave element is provided on the first surface, and the elastic 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, and the linear expansion coefficient of the third substrate in the direction is in the direction. The configuration can be smaller than the linear expansion coefficient in the direction of the fourth substrate.

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

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

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

The present invention comprises a first piezoelectric substrate having a first surface, a first elastic wave element provided on the first surface and having a pair of comb-shaped electrodes having a plurality of first electrode fingers, and the first piezoelectric substrate. The linear expansion coefficient in the first direction in which the plurality of first electrode fingers are arranged is directly or indirectly joined to the surface opposite to the first surface of the first piezoelectric substrate. The first substrate, which is smaller than the linear expansion coefficient, is directly or indirectly bonded to the surface of the first substrate opposite to the first piezoelectric substrate side, and the linear expansion coefficient in the first direction is in the first direction. A second substrate having a linear expansion coefficient larger than that of the first substrate, a second piezoelectric substrate mounted on the first surface and having a second surface facing the first surface with a gap interposed therebetween, and a second piezoelectric substrate provided on the second surface. A second elastic wave element having a pair of comb-shaped electrodes having a plurality of second electrode fingers is directly or indirectly bonded to a surface of the second piezoelectric substrate opposite to the second surface. A third substrate whose linear expansion coefficient in the second direction in which a plurality of second electrode fingers are arranged is smaller than the linear expansion coefficient of the second piezoelectric substrate in the second direction, and the second piezoelectric substrate side of the third substrate. A fourth substrate which is directly or indirectly joined to a surface opposite to the above surface and whose linear expansion coefficient in the second direction is larger than the linear expansion coefficient of the third substrate in the second direction, and the first surface and the above. An elastic wave device including a connection layer that connects the second surface.

In the above configuration, the second substrate and the fourth substrate may be a piezoelectric substrate.

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

In the above configuration, the connecting layer may be a sealing portion that surrounds the elastic wave element and seals the elastic wave element in the void.

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

The present invention is a multiplexer including the above filter.

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

FIG. 1 is a cross-sectional view of the elastic wave device according to the first embodiment. FIG. 2A is a plan view of the elastic wave element 12 in the first embodiment, and FIG. 2B is a cross-sectional view of the elastic wave element 22. 3 (a) to 3 (c) are cross-sectional views (No. 1) showing a method of manufacturing an elastic wave device according to the first embodiment. 4 (a) to 4 (c) are cross-sectional views (No. 2) showing a method of manufacturing an elastic wave device according to the first embodiment. 5 (a) and 5 (b) are cross-sectional views (No. 3) showing a method of manufacturing an elastic wave device according to the first embodiment. FIG. 6 is a cross-sectional view of the elastic wave device according to Comparative Example 1. FIG. 7 is a cross-sectional view of the elastic wave device according to the first modification of the first embodiment. 8 (a) is a cross-sectional view of the elastic wave device according to the second modification of the first embodiment, and FIG. 8 (b) is a plan view. FIG. 9 is a cross-sectional view of the elastic wave device according to the second embodiment. FIG. 10A is a circuit diagram of the filter according to the second embodiment, and FIG. 10B is a circuit diagram of the duplexer according to the first modification of the second embodiment.

Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of the elastic wave device according to the first embodiment. The stacking direction of the substrates 10 and 20 is the Z direction, the propagation direction of the elastic wave of the elastic 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 has 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 joined to the upper surface of the support substrate 10a. The coefficient of linear expansion α2 of the support substrate 10a is smaller than the coefficient of linear expansion 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 to each other, or may be indirectly bonded to each other via an insulator layer such as silicon oxide or aluminum nitride.

An elastic wave element 12, a 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 elastic wave element 12 and the wiring 14 in a plan view. A terminal 18 is provided on the lower surface of the substrate 10. The terminal 18 is a foot pad for connecting the elastic wave elements 12 and 22 to the outside. A via wiring 16 penetrating the substrate 10 is provided. 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 metal layers such as a copper layer, an aluminum layer, a platinum layer, or a gold layer. The cyclic metal layer 32 is, for example, a nickel layer.

The substrate 20 is mounted on the substrate 10. The substrate 20 has 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. The substrate 20b is joined to the upper surface of the substrate 20a. The coefficient of linear expansion α4 of the substrate 20b is larger than the coefficient of linear expansion α3 of the substrate 20a. The thicknesses of the substrate 20a and the substrate 20b are T3 and T4, respectively.

An elastic wave element 22 and a 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 substrate 20 is flip-chip mounted (face-down mounted) on the substrate 10 via bumps 28. The bump 28 is, for example, a gold bump, a solder bump or a copper bump. The bump 28 joins the wires 14 and 24.

A sealing portion 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 portion 30 is joined to the annular metal layer 32. A flat plate-shaped lid 36 is provided on the upper surface of the substrate 20 and the upper surface of the sealing portion 30. The lid 36 is a metal plate such as a Kovar plate or an insulating plate. A protective film 38 is provided so as to cover the lid 36 and the sealing portion 30. The protective film 38 is a metal film such as a nickel film or an insulating film.

The elastic wave element 12 faces the substrate 20 via the gap 26. The elastic wave element 22 faces the piezoelectric substrate 10b via the gap 26. The elastic wave elements 12 and 22 are sealed by the sealing portion 30, the substrate 10, the substrate 20 and the lid 36. The bump 28 is surrounded by the void 26. The terminal 18 is electrically connected to the elastic wave element 12 via the via wiring 16 and the wiring 14, and is further electrically connected to the elastic 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, 0.5 μm to 30 μm, which are, for example, equal to or less than the wavelength of elastic waves. 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 joined is, for example, 0.1 μm to 5 μm.

FIG. 2A is a plan view of the elastic wave element 12 in the first embodiment, and FIG. 2B is a cross-sectional view of the elastic wave element 22. As shown in FIG. 2A, the elastic wave element 12 is an elastic surface 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 for connecting the plurality of electrode fingers 40b. Reflectors 42 are provided on both sides of the IDT 40.

IDT40 excites surface acoustic waves on the piezoelectric substrate 10b. The wavelength of the elastic wave is substantially equal to the pitch of the electrode fingers 40b of one comb-shaped electrode 40a of the pair of comb-shaped electrodes 40a. That is, the wavelength of the elastic wave is substantially 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 arrangement direction of the electrode fingers 40b is the X direction, which is the propagation direction of elastic waves. The stretching direction of the electrode finger 40b is the Y direction.

As shown in FIG. 2B, the elastic wave element 22 is a piezoelectric thin film resonator. A piezoelectric film 46 is provided on the substrate 20. The lower electrode 44 and the upper electrode 48 are provided so as to sandwich the piezoelectric film 46. A gap 45 is formed between the lower electrode 44 and the substrate 20. The region where the lower electrode 44 and the upper electrode 48 face each other with at least a part of the piezoelectric film 46 sandwiched is the 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 in 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 metal films such as a ruthenium film. The piezoelectric film 46 is, for example, an aluminum nitride film. An acoustic reflection film that reflects elastic waves may be provided instead of the gap 45.

The elastic wave elements 12 and 22 include electrodes that excite elastic waves. Therefore, the elastic wave elements 12 and 22 are covered with the voids 26 so as not to limit the elastic waves.

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

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

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

As shown in FIG. 4B, the elastic wave element 12 and the wiring 14 are formed on the piezoelectric substrate 10b. As shown in FIG. 4C, the support substrate 10a is made to a desired thickness by using, for example, the CMP method. As a result, the via wiring 16 is exposed on the lower surface of the support substrate 10a. The terminal 18 is formed on the lower surface of the support substrate 10a.

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

As shown in FIG. 5B, the sealing portion 30 is formed so as 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 portion 30 and the substrate 20. The lid 36 may not be provided. The sealing portion 30 is formed by heating from 200 ° C. to 300 ° C. when the sealing portion 30 is solder or resin. After that, the substrate 10 is cut. As a result, the elastic wave device is fragmented. A protective film 38 surrounding the sealing portion 30 and the lid 36 is formed. As a result, the elastic wave device of FIG. 1 is manufactured.

[Comparative Example 1]
FIG. 6 is a cross-sectional view of the elastic wave device according to Comparative Example 1. As shown in FIG. 6, in the elastic wave device of Comparative Example 1, the substrate 20b is not provided on the substrate 20. 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 coefficient of linear expansion of the sapphire substrate is 7 ppm / ° C., and the coefficient of linear expansion 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 becomes high in the step of joining the bump 28 in FIG. 5A and the step of forming the sealing portion 30 in FIG. 5B, the center of the substrate 10 warps toward the substrate 20 as compared with the periphery as shown by the broken line 60. .. On the other hand, the substrate 20 hardly warps as shown 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 warp of the substrate 10 becomes small, and thermal stress is applied to the bump 28 in the direction opposite to that at the time of high temperature in the vertical direction. As a result, the bump 28 may be peeled off or the like.

According to the first embodiment, the support substrate 10a (second substrate) is directly or indirectly bonded to the lower surface (opposite surface of 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 the gap 26 interposed therebetween. 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 elastic 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. The bump 28 (connection layer) connects the upper surface of the piezoelectric substrate 10b and the lower surface of the 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 changed from the linear expansion coefficient α1 of the piezoelectric substrate 10b to the linear expansion coefficient α2 of the support substrate 10a. Nearly, the coefficient of linear expansion α4 of the substrate 20b is closer to the coefficient of linear expansion α1 of the piezoelectric substrate 10b than the coefficient of linear expansion α3 of the substrate 20a. That is, | α3-α1 |> | α3-α2 | and | α4-α2 |> | α4-α1 |.

As a result, as shown by the broken lines 60 and 62 in FIG. 1, the difference between the warp of the substrate 10 and the warp of the substrate 20 is smaller than the difference between the warp of the substrate 10 and the warp of the substrate 20 of Comparative Example 1. Therefore, the stress applied to the bump 28 is reduced, and deterioration such as peeling of the bump 28 can be suppressed. | Α3-α1 | / 2> | α3-α2 | is preferable, | α3-α1 | / 5> | α3-α2 | is more preferable, and α3 and α1 are even more preferable. | Α4-α2 | / 2> | α4-α1 | is preferable, | α4-α2 | / 5> | α4-α1 | is more preferable, and α4 and α2 are even more preferable.

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

The piezoelectric substrate 10b is thinner than the support substrate 10a, and the substrate 20b is thinner than the substrate 20a. As a result, the difference between the warp of the substrate 10 and the warp of the substrate 20 becomes small, and the stress applied to the bump 28 can be suppressed. The thickness T1 of the piezoelectric substrate 10b is preferably 1/2 or less, more preferably 1/5 or less, still 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 warps. Therefore, T1 is preferably 1/100 or more of T2, and 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, and 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 further preferably 0.1 or less.

It is preferable that the piezoelectric substrate 10b and the substrate 20b contain the same material as the main component, and the support substrate 10a and the substrate 20a contain the same material as the main component. As a result, α1 and α4 can be made substantially equal, and α2 and α3 can be made substantially equal. The main component of the substrate allows impurities other than the main component to be intentionally or unintentionally contained in the substrate. For example, the total concentration of one or more elements contained in the main component is 50 atoms. % Or more.

When the elastic 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 the linear expansion coefficient of the support substrate 10a than the linear expansion coefficient of the substrate 20b.

[Modification 1 of Example 1]
FIG. 7 is a cross-sectional view of the elastic wave device according to the first modification of the first embodiment. As shown in FIG. 7, the substrate 10 is mounted on the substrate 20. In the substrate 20, the substrate 20a is bonded onto the substrate 20b. An elastic wave element 22, a wiring 24, and an annular metal layer 32 are provided on the substrate 20a. A via wiring 16 penetrating the substrate 20 is provided. A terminal 18 is provided on the lower surface of the substrate 20. The support substrate 10a is bonded onto the piezoelectric substrate 10b. An elastic wave element 12 and a wiring 14 are provided on the lower surface of the piezoelectric substrate 10b. The bump 28 is joined to the wires 14 and 24. A sealing portion 30 is provided so as to surround the substrate 10. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

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

[Modification 2 of Example 1]
8 (a) is a cross-sectional view of the elastic wave device according to the second modification of the first embodiment, and FIG. 8 (b) is a plan view. In FIG. 8B, the sealing portion 30a is shown. As shown in FIGS. 8 (a) and 8 (b), the planar shapes of the substrates 10 and 20 are substantially the same. A sealing portion 30a is provided between the substrates 10 and 20 on the periphery of the substrates 10 and 20. The sealing portion 30a is a metal layer such as a copper layer, and seals the elastic wave elements 12 and 22 in the gap 26. The bump 28 and the sealing portion 30a function as a connecting layer. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted. As in the second modification of the first embodiment, the sealing portion 30a may function as a connecting 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 the elastic wave device according to the second embodiment. As shown in FIG. 9, in the substrate 10, the support substrate 10a is bonded on the piezoelectric substrate 10c, and the piezoelectric substrate 10b is bonded on the support substrate 10a. An elastic wave element 12 and a wiring 14 are provided on the upper surface of the piezoelectric substrate 10b. A terminal 18 is provided on the lower surface of the piezoelectric substrate 10c. The via wiring 16 penetrating the substrate 10 electrically connects the wiring 14 and the terminal 18.

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

According to the second embodiment, the elastic wave element 12 (first elastic wave element) is provided on the upper surface (first surface) of the piezoelectric substrate 10b (first piezoelectric substrate), and a plurality of electrode fingers 40b (first electrode fingers) are provided. ) Is provided with a pair of comb-shaped electrodes 40a. The support substrate 10a (first substrate) is directly or indirectly joined to the lower surface (the surface opposite to the first surface) of the piezoelectric substrate 10b, and linear expansion 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 joined to the surface of the support substrate 10a opposite to the piezoelectric substrate 10b side, and the coefficient of linear expansion in the first direction is the line of the support substrate 10a in the first direction. Greater than the coefficient of expansion.

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 the gap 26 interposed therebetween. The elastic wave element 22 (second elastic 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 support substrate 20a is directly or indirectly bonded to the surface opposite to the lower surface of the piezoelectric substrate 20b, and the coefficient of linear expansion in the second direction in which the electrode fingers 40b are arranged is the coefficient of linear expansion of the piezoelectric substrate 20b in the second direction. Smaller. The piezoelectric substrate 20c is directly or indirectly bonded to the surface of the support substrate 20a opposite to the piezoelectric substrate 20b side, and the coefficient of linear expansion in the second direction is larger than the coefficient of linear expansion of the support substrate 20a in the second direction.

As a result, the piezoelectric substrate 10c compensates for the warp of the substrate 10 due to the difference in the coefficient of linear expansion between the support substrate 10a and the piezoelectric substrate 10b. The piezoelectric substrate 20c compensates for the warp of the substrate 20 due to the difference in the coefficient of linear expansion between the support substrate 20a and the piezoelectric substrate 20b. Therefore, the stress applied to the bump 28 (connecting layer) can be suppressed.

The difference in the coefficient of linear expansion between the piezoelectric substrates 10b and 10c is preferably smaller than the difference in the coefficient of linear expansion between the support substrate 10a and the piezoelectric substrate 10b. The difference in the coefficient of linear expansion between the piezoelectric substrates 12b and 12c is preferably smaller than the difference in the coefficient of linear expansion between the support substrate 12a and the piezoelectric substrate 12b. As a result, the stress applied to the bump 28 can be suppressed.

The difference in the coefficient of linear expansion between the support substrate 20a and the piezoelectric substrate 10b and the difference in the coefficient of linear expansion between the support substrate 20a and the piezoelectric substrate 10c may be smaller than the difference in the coefficient of linear expansion between the support substrates 20a and 10a. preferable. Difference in coefficient of linear expansion between piezoelectric substrates 20b and 10b, difference in coefficient of linear expansion between piezoelectric substrates 20b and 10c, difference in coefficient of linear expansion between piezoelectric substrates 20c and 10b, and coefficient of linear expansion between piezoelectric substrates 20c and 10c The difference is preferably smaller than either the difference in the coefficient of linear expansion between the piezoelectric substrate 20b and the support substrate 10a and the difference in the coefficient of linear expansion between the piezoelectric substrate 20c and the support substrate 10a. As a result, the stress applied to the bump 28 can be suppressed.

The piezoelectric substrates 10b and 10c preferably contain the same material as the main component, and the piezoelectric substrates 20b and 20c preferably contain the same material as the main component. It is preferable that the thickness of the piezoelectric substrate 10b and the thickness of the piezoelectric substrate 10c are substantially equal to each other. It is preferable that the thickness of the piezoelectric substrate 20b and the thickness of the piezoelectric substrate 20c are substantially equal to each other. It is preferable that the thickness of the piezoelectric substrates 10b and 10c is substantially equal to the thickness of the piezoelectric substrates 20b and 20c. It is preferable that the support substrates 10a and 20a contain the same material as the 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. As a result, the stress applied to the bump 28 can be suppressed.

It is preferable that the thickness of the piezoelectric substrate 10b and the thickness of the piezoelectric substrate 10c are thinner than those of the support substrate 10a, respectively. It is preferable that the thickness of the piezoelectric substrate 20b and the thickness of the piezoelectric substrate 20c are thinner than those of the support substrate 20a, respectively. As a result, the difference between the warp of the substrate 10 and the warp of the substrate 20 becomes small, and the stress applied to the bump 28 can be suppressed. The thickness 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, respectively. If the piezoelectric substrate 10b is too thin, the substrate 10 will not warp. Therefore, the thicknesses of the piezoelectric substrates 10b and 10c are preferably 1/100 or more, more preferably 1/20 or more of the thickness of the support substrate 10a, respectively. Similarly, the thicknesses of the piezoelectric substrates 20b and 20c are 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, respectively. The thickness 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, respectively.

It is preferable that the arrangement direction of the electrode fingers 40b of the elastic wave element 12 and the arrangement direction of the electrode fingers 40b of the elastic wave element 22 are substantially parallel. As a result, the difference between the warp of the substrate 10 and the warp of the substrate 20 can be reduced. Therefore, the stress applied to the bump 28 can be reduced. The angle formed by the arrangement direction of the electrode fingers 40b of the elastic wave element 12 and the arrangement direction of the electrode fingers 40b of the elastic wave element 22 is preferably 45 ° or less, more preferably 30 ° or less.

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

In Examples 1 and 2 and modified examples thereof, an example of a piezoelectric thin film resonator is described as the elastic wave element 22, but the elastic wave element 22 may be an elastic surface wave resonator. Although the example of the elastic wave element 22 has been described as the functional element provided on the lower surface of the substrate 20, the functional element may be a passive element such as an inductor or a capacitor, an active element including a transistor, or a MEMS (Micro Electro Mechanical Systems) element. ..

Example 3 is an example of a filter and a duplexer. FIG. 10A is a circuit diagram of the filter according to the second embodiment. As shown in FIG. 10A, 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 Example 2 may be formed of elastic wave elements 12 and / or 22. The number of series resonators and parallel resonators can be set as appropriate. Although the ladder type filter has been described as an example of the filter, the filter may be a multiple mode type filter.

FIG. 10B is a circuit diagram of the duplexer according to the first modification of the second embodiment. As shown in FIG. 10B, 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 input 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 input from the common terminal Ant as a reception signal to the reception terminal Rx, and suppresses signals of other frequencies. At least one of the transmission filter 50 and the reception filter 52 can be the filter of the second embodiment. Further, the transmission filter 50 may be formed by the elastic wave element 12, and the reception filter 52 may be formed by the elastic wave element 22.

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

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. It can be changed.

10a Support board 10b Piezoelectric board 12, 22 Elastic wave element 14, 24 Wiring 16a, 16b Via wiring 17a-17c Metal layer 18 terminals 20 Board 26 Void 28a, 28c Bump 30 Sealing part 32 Cyclic metal layer 36 lid 50 Transmission filter 52 Receive filter

Claims (12)

A first substrate having a first surface and
A second substrate that is directly or indirectly bonded to a surface of the first substrate opposite to the first surface and has a coefficient of linear expansion different from the coefficient of linear expansion of the first substrate.
It is provided on the first surface, has a second surface facing the first surface with a gap in between, and has a linear expansion coefficient closer to the linear expansion coefficient of the second substrate than the linear expansion coefficient of the first substrate. With the third board
A fourth substrate that is directly or indirectly joined to a surface of the third substrate opposite to the second surface and has a linear expansion coefficient closer to the linear expansion coefficient of the first substrate than the linear expansion coefficient of the third substrate. With the board
An elastic 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 first substrate and the fourth substrate are piezoelectric substrates, and are
The elastic wave element is provided on the first surface.
The elastic wave element includes a pair of comb-shaped electrodes having a plurality of electrode fingers.
The coefficient of linear expansion in the direction in which the plurality of electrode fingers of the second substrate are arranged is smaller than the coefficient of linear expansion of the first substrate in the direction.
The elastic wave device according to claim 1, wherein the coefficient of linear expansion of the third substrate in the direction is smaller than the coefficient of linear expansion of the fourth substrate in the direction. The elastic wave device according to claim 2, wherein the first substrate and the fourth substrate are a lithium tantalate substrate or a lithium niobate substrate. The elastic wave device according to claim 2 or 3, wherein the elastic wave element includes a piezoelectric thin film resonator provided on the second surface. The first substrate is thinner than the second substrate,
The elastic wave device according to any one of claims 2 to 4, wherein the fourth substrate is thinner than the third substrate. The first substrate and the fourth substrate contain the same material as the main component.
The elastic wave device according to any one of claims 1 to 5, wherein the second substrate and the third substrate contain the same material as a main component. A first piezoelectric substrate having a first surface and
A first elastic wave element provided on the first surface and having a pair of comb-shaped electrodes having a plurality of first electrode fingers.
The coefficient of linear expansion in the first direction, which is directly or indirectly bonded to the surface of the first piezoelectric substrate opposite to the first surface and in which the plurality of first electrode fingers are arranged, is the said in the first direction. The first substrate, which is smaller than the coefficient of linear expansion of the first piezoelectric substrate,
It is directly or indirectly bonded to the surface of the first substrate opposite to the first piezoelectric substrate side, and the coefficient of linear expansion in the first direction is larger than the coefficient of linear expansion of the first substrate in the first direction. With the second board
A second piezoelectric substrate mounted on the first surface and having a second surface facing the first surface with a gap interposed therebetween.
A second elastic wave element provided on the second surface and provided with a pair of comb-shaped electrodes having a plurality of second electrode fingers.
The coefficient of linear expansion in the second direction, which is directly or indirectly bonded to the surface of the second piezoelectric substrate opposite to the second surface and in which the plurality of second electrode fingers are arranged, is the said in the second direction. A third substrate that is smaller than the coefficient of linear expansion of the second piezoelectric substrate,
It is directly or indirectly bonded to the surface of the third substrate opposite to the second piezoelectric substrate side, and the coefficient of linear expansion in the second direction is larger than the coefficient of linear expansion of the third substrate in the second direction. 4th board and
A connection layer connecting the first surface and the second surface,
An elastic wave device equipped with. The elastic wave device according to claim 7, wherein the second substrate and the fourth substrate are piezoelectric substrates. The elastic wave device according to any one of claims 1 to 8, wherein the connecting layer is a bump. The elastic wave device according to any one of claims 1 to 9, wherein the connecting layer is a sealing portion that seals the void. A filter comprising the elastic wave device according to any one of claims 1 to 10. A multiplexer containing the filter according to claim 11.

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