WO2018186240A1

WO2018186240A1 - Acoustic wave device

Info

Publication number: WO2018186240A1
Application number: PCT/JP2018/012543
Authority: WO
Inventors: 康彦平野
Original assignee: 株式会社村田製作所
Priority date: 2017-04-07
Filing date: 2018-03-27
Publication date: 2018-10-11

Abstract

Provided is an acoustic wave device in which breakdown around a via electrode is unlikely to occur. An acoustic wave device 1 includes: a piezoelectric substrate 2; an IDT electrode 3 (functional electrode) provided on the piezoelectric substrate 2; a support layer 5 (first layer) provided on the piezoelectric substrate 2; a cover layer 6 (second layer) provided on the support layer 5; and a via electrode 7 which penetrates the support layer 5 and the cover layer 6 and has a first end face 7a located on the piezoelectric substrate 2 side, a second end face 7b located on the side opposite to the first end face 7a, and a side face 7c connecting the first end face 7a and the second end face 7b. In the via electrode 7, the area of the second end face 7b is larger than the area of the first end face 7a. When a direction in which the via electrode 7 penetrates the support layer 5 and the cover layer 6 is taken as a first direction Z, an arbitrary direction orthogonal to the first direction Z is taken as a second direction and the via electrode is projected in the second direction, the shape of the side face 7c of the via electrode 7 includes a shape curved inward in the via electrode 7.

Description

Elastic wave device

The present invention relates to an elastic wave device.

Conventionally, elastic wave devices have been widely used for filters of mobile phones.

For example, Patent Document 1 below discloses an example of an elastic wave device having a WLP (Wafer Level Package) structure. This elastic wave device has a space surrounded by a piezoelectric substrate, an insulator, and a lid. An IDT electrode is provided on the piezoelectric substrate so as to be located in the space. The acoustic wave device has a via electrode that is a connection electrode penetrating the insulator and the lid. The side surface of the via electrode is inclined with respect to the direction in which the via electrode passes through the insulator and the lid. An external terminal is connected to the end of the via electrode opposite to the piezoelectric substrate side. Bumps are bonded to the external terminals.

International Publication No. 2006/106831

¡By increasing the area of the end face of the via electrode on the external terminal side, heat dissipation can be improved. However, when the area of the end surface is increased as described above, the width of the insulator or the lid positioned between the side surface of the via electrode and the space is shortened. For this reason, a crack may occur in the insulator or the cover between the side surface of the via electrode and the space due to an impact when bonding the bumps.

Furthermore, when the side surface of the via electrode is inclined, a large force is easily applied to the insulator and the lid body from the side surface when the bump is bonded. Therefore, cracks were likely to occur.

An object of the present invention is to provide an elastic wave device that is less likely to be damaged around a via electrode.

An elastic wave device according to the present invention is provided on a piezoelectric substrate, a functional electrode provided on the piezoelectric substrate, a first layer provided on the piezoelectric substrate, and the first layer. A second end layer, a first end surface penetrating through the first layer and the second layer, and positioned on the piezoelectric substrate side, and positioned opposite to the first end surface And a via electrode having a side surface connecting the first end surface and the second end surface, wherein the area of the second end surface is the first end surface. A direction in which the via electrode passes through the first layer and the second layer is defined as a first direction, and an arbitrary direction orthogonal to the first direction is defined as a second direction. When the via electrode is projected in the second direction, the shape of the side surface of the via electrode is Including a curved shape inwardly of A electrodes.

In a specific aspect of the acoustic wave device according to the present invention, when the via electrode is projected in the second direction, the side surface of the via electrode is connected to the first end surface and the second end surface. And having one side surface portion and the other side surface portion facing each other, the one side surface portion being connected to the first end surface connected to the first end surface and the second end surface A second connecting point, and the one side surface portion has a first connecting point and an imaginary line connecting the first connecting point and the second connecting point by a straight line. The portion other than the second connection point is located inside the via electrode. In this case, damage is less likely to occur around the via electrode.

In another specific aspect of the acoustic wave device according to the present invention, when the via electrode is projected in the second direction, all of the side surfaces of the via electrode are curved inwardly in the via electrode. is there. In this case, damage is less likely to occur around the via electrode.

In still another specific aspect of the acoustic wave device according to the present invention, when the via electrode is projected in the second direction, the shape of the side surface of the via electrode includes a linear shape.

In another specific aspect of the acoustic wave device according to the present invention, when the via electrode is projected in the second direction, the second end surface side of the via electrode is located on the inner side of the via electrode. It is a curved shape, and the first end surface side is a linear shape.

In still another specific aspect of the acoustic wave device according to the present invention, the side surface of the via electrode has a projecting portion that projects outward from the via electrode, and the side surface includes the projecting portion and the side surface. No step portion is provided between the projecting portion and the portion on the first end face side. In this case, it is difficult for damage to occur around the via electrode, and the via electrode is difficult to come off.

In still another specific aspect of the acoustic wave device according to the present invention, the second layer includes an inner layer provided on the first layer and an outer layer provided on the inner layer.

In still another specific aspect of the acoustic wave device according to the present invention, the first layer has an opening that surrounds the functional electrode in plan view, and the second layer has the opening. A hollow space is provided on the first layer so as to be covered, and is surrounded by the piezoelectric substrate, the first layer, and the second layer, and the functional electrode is provided in the hollow space. Is placed inside.

In still another specific aspect of the acoustic wave device according to the present invention, the first layer is provided on the piezoelectric substrate so as to cover the functional electrode.

In yet another specific aspect of the elastic wave device according to the present invention, the functional electrode is an IDT electrode and uses a surface acoustic wave.

According to the present invention, it is possible to provide an acoustic wave device that is unlikely to break around the via electrode.

FIG. 1 is a front sectional view of an acoustic wave device according to a first embodiment of the present invention. FIG. 2 is a projection view in which the via electrode in the first embodiment of the present invention is projected in the second direction. FIG. 3 is an enlarged front sectional view of the vicinity of the via electrode of the elastic wave device of the first comparative example. FIG. 4 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device of the second comparative example. FIG. 5 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device according to the first embodiment of the present invention. FIG. 6 is an enlarged front cross-sectional view of the vicinity of the via electrode of the acoustic wave device according to the modification of the first embodiment of the present invention. FIG. 7 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device according to the second embodiment of the present invention. FIG. 8 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device according to the first modification of the second embodiment of the present invention. FIG. 9 is an enlarged front cross-sectional view of the vicinity of the via electrode of the acoustic wave device according to the second modification of the second embodiment of the present invention. FIG. 10 is a front sectional view of an acoustic wave device according to a third embodiment of the present invention.

Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

It should be pointed out that each embodiment described in this specification is an example, and a partial replacement or combination of configurations is possible between different embodiments.

FIG. 1 is a front sectional view of an acoustic wave device according to a first embodiment of the present invention.

The acoustic wave device 1 has a piezoelectric substrate 2. The piezoelectric substrate 2 may be made of a piezoelectric single crystal such as LiNbO ₃ or LiTaO ₃ , or may be made of an appropriate piezoelectric ceramic.

An IDT electrode 3 as a functional electrode is provided on the piezoelectric substrate 2. On the piezoelectric substrate 2, an electrode land 4 electrically connected to the IDT electrode 3 is also provided. When an AC voltage is applied to the IDT electrode 3, an elastic wave is excited. The surface acoustic wave device 1 of the present embodiment is a surface acoustic wave device that uses surface acoustic waves. The IDT electrode 3 may be made of a laminated metal film in which metal films are laminated, or may be made of a single-layer metal film. The electrode land 4 may also be made of the same material as the IDT electrode 3. The functional electrode is not limited to the IDT electrode. The elastic wave device 1 may be an elastic wave device that uses elastic waves other than surface acoustic waves.

A support layer 5 as a first layer is provided on the piezoelectric substrate 2. The support layer 5 has an opening 5a surrounding the IDT electrode 3 in plan view. The support layer 5 is made of an appropriate resin or the like.

A cover layer 6 as a second layer is provided on the support layer 5 so as to cover the opening 5a. A hollow space surrounded by the piezoelectric substrate 2, the support layer 5 and the cover layer 6 is provided. The IDT electrode 3 is disposed in the hollow space.

Note that the hollow space is not necessarily provided. In the present embodiment, the first layer is the support layer 5 having the opening 5a, but the first layer may not have the opening 5a. The first layer may be provided on the piezoelectric substrate 2 so as to cover the IDT electrode 3.

In the present embodiment, the cover layer 6 has an inner layer 6a provided on the support layer 5 and an outer layer 6b provided on the inner layer 6a. The inner layer 6a is made of, for example, an epoxy resin. The outer layer 6b is made of, for example, polyimide resin. In the present embodiment, the inner layer 6a is an adhesive layer, and the outer layer 6b is a protective layer. By having the inner layer 6a, the bonding force between the cover layer 6 and the support layer 5 can be increased. By having the outer layer 6b, the strength of the acoustic wave device 1 can be increased. The cover layer 6 may be a single layer.

As shown in FIG. 1, a via electrode 7 is provided so as to penetrate the support layer 5 and the cover layer 6. The via electrode 7 has a first end face 7a located on the piezoelectric substrate 2 side and a second end face 7b located on the opposite side to the first end face 7a. The area of the second end face 7b is larger than the area of the first end face 7a. The via electrode 7 has a side surface 7c that connects the first end surface 7a and the second end surface 7b. The first end face 7 a of the via electrode 7 is connected to the electrode land 4. On the other hand, bumps 8 are provided so as to be connected to the second end face 7 b of the via electrode 7.

Since the area of the second end face 7b is larger than the area of the first end face 7a, the contact area between the via electrode 7 and the bump 8 can be increased, and the bonding force can be increased. In addition, since the contact area between the via electrode 7 and the bump 8 is large, heat dissipation can be improved.

Here, a direction in which the via electrode 7 passes through the support layer 5 and the cover layer 6 is defined as a first direction Z, and an arbitrary direction orthogonal to the first direction Z is defined as a second direction. The planar shape of the via electrode 7 of the present embodiment is circular, and the shape of the via electrode 7 is the same regardless of the second direction. The shape of the via electrode 7 may be different when projected in a certain second direction and when projected in another second direction.

FIG. 2 is a projection view in which the via electrode in the first embodiment is projected in the second direction.

When the via electrode 7 is projected in the second direction, the side surface 7c of the via electrode 7 is connected to the first end surface 7a and the second end surface 7b and faces the first side surface portion 7d facing each other. And a second side surface portion 7e. The first side surface portion 7d and the second side surface portion 7e are the one side surface portion and the other side surface portion of the present invention. The first side surface portion 7d has a first connection point 17A connected to the first end surface 7a and a second connection point 17B connected to the second end surface 7b.

In the present embodiment, when the via electrode 7 is projected in the second direction, all the side surfaces 7c of the via electrode 7 are curved inwardly in the via electrode 7.

Here, a virtual line connecting the first connection point 17A and the second connection point 17B with a straight line is defined as a virtual line A. A feature of the present embodiment is that the first side surface portion 7d is located inside the via electrode 7 with respect to the imaginary line A except for the first connection point 17A and the second connection point 17B. Thereby, the support layer 5 and the cover layer 6 and the like are hardly damaged around the via electrode 7. This will be described below by comparing the present embodiment with the first comparative example and the second comparative example.

Note that, as described above, the second direction is an arbitrary direction orthogonal to the first direction. When the via electrode 7 is projected in any second direction, the first side surface portion 7d is located on the inner side of the via electrode 7 with respect to the imaginary line A, except for the first connection point 17A and the second connection point 17B. Is located. Therefore, the 2nd side part 7e also has the said characteristic similar to the 1st side part 7d. More specifically, the second side surface portion 7e includes a third connection point 17C connected to the first end surface 7a and a fourth connection point 17D connected to the second end surface 7b. Have. When a virtual line connecting the third connection point 17C and the fourth connection point 17D with a straight line is defined as a virtual line B, the second side surface portion 7e has the third connection point 17C and the fourth connection point. Other than 17D, it is located inside the via electrode 7 with respect to the virtual line B.

FIG. 3 is an enlarged front cross-sectional view of the vicinity of the via electrode of the elastic wave device of the first comparative example. Here, the second direction is the front direction. FIG. 3 is a cross-sectional view at a position where the via electrode has a shape similar to the shape projected in the second direction. The same applies to the front sectional views shown below.

The first comparative example is different from the first embodiment in that when the via electrode 207 is projected in the second direction, the side surface 207c does not have a curved portion. The first side surface portion 207d is linear and has a shape corresponding to the virtual line A in the first embodiment shown in FIG.

In the first comparative example, the distance between the side surface 207c of the via electrode 207 and the hollow space is short. Therefore, the strength of the support layer 5 and the cover layer 6 is low. Therefore, cracks are likely to occur in the support layer 5 and the cover layer 6 between the side surface 207c of the via electrode 207 and the hollow space due to an impact such as when the bumps 8 are joined. In addition, since the side surface 207c is inclined with respect to the first direction, a large force is easily applied to the support layer 5 and the cover layer 6 from the side surface 207c when the bumps 8 are joined. Therefore, cracks are more likely to occur.

FIG. 4 is an enlarged front sectional view of the vicinity of the via electrode of the elastic wave device of the second comparative example.

The second comparative example is different from the first embodiment in that when the via electrode 217 is projected in the second direction, the side surface 217c does not have a curved portion and has a stepped portion 217f. More specifically, the step portion 217f is provided on the second end surface 7b side rather than the first end surface 7a side. The step portion 217f has a corner portion 217g located outside the via electrode 217. When the dimension along the transverse direction of the via electrode 217 is defined as the width, the width of the portion closer to the second end face 7b than the stepped portion 217f is wider than the width of the portion closer to the first end face 7a than the stepped portion 217f.

The first side surface portion 217d extends in parallel with the first direction from the first end surface 7a to the stepped portion 217f. Therefore, in the second comparative example, the distance between the side surface 217c of the via electrode 217 and the hollow space is longer than in the first comparative example. However, stress is concentrated on the stepped portion 217f when the bump 8 is bonded. The stress is particularly concentrated at the corner portion 217g of the step portion 217f. When stress is locally concentrated on the stepped portion 217f or the corner portion 217g, cracks are likely to occur in the surrounding support layer 5 and cover layer 6 due to deformation and distortion due to the stress concentration.

FIG. 5 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device according to the first embodiment.

In the via electrode 7 in the present embodiment, the first side surface portion 7d is located inside the via electrode 7 with respect to the imaginary line A except for the first connection point 17A and the second connection point 17B. Thereby, the distance between the side surface 7c and the hollow space is long. Thereby, the strength of the support layer 5 and the cover layer 6 can be increased.

In addition, since the first side surface portion 7d has a curved shape, the contact area between the side surface 7c, the support layer 5 and the cover layer 6 is large. Further, the via electrode 7 does not have a stepped portion or a corner portion where stress is concentrated. Thereby, stress can be effectively dispersed when the bumps 8 are joined. Therefore, the support layer 5 and the cover layer 6 around the via electrode 7 are hardly damaged.

The distance between the outer surface of the elastic wave device 1 of the support layer 5 and the cover layer 6 and the side surface 7c of the via electrode 7 can also be increased. Therefore, damage is less likely to occur around the via electrode 7.

As described above, in the present embodiment, all of the side surface 7c of the via electrode 7 is curved when projected in the second direction. Note that the entire side surface 7c does not have to be curved. When projected in the second direction, the shape of the side surface 7c may include a linear shape.

FIG. 6 is an enlarged front cross-sectional view of the vicinity of the via electrode of the acoustic wave device according to the modified example of the first embodiment.

In this modification, the side surface 107c of the via electrode 107 has a shape curved inward in the via electrode 107 at a portion in contact with the outer layer 6b of the cover layer 6. On the other hand, the side surface 107 c has a linear shape in a portion in contact with the inner layer 6 a and the support layer 5.

Thus, in the side surface 107c, the linearly shaped portion is located closer to the first end surface 7a than the curved portion. Note that in the side surface 107c, the positional relationship between the curved portion and the linear portion is not limited to the above. For example, the curved portion may be positioned closer to the first end surface 7a than the portion having a linear shape.

FIG. 7 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device according to the second embodiment.

This embodiment is different from the first embodiment in that the via electrode 27 has an overhang portion 29. Except for the above points, the elastic wave device of the present embodiment has the same configuration as the elastic wave device 1 of the first embodiment.

The overhang portion 29 has one step portion. In the present embodiment, the protruding portion 29 is provided so that the stepped portion is located at the boundary between the inner layer 6 a and the outer layer 6 b of the cover layer 6. The position of the overhanging portion 29 is not limited to the above.

The via electrode 27 has a portion closer to the second end surface 7b than the stepped portion and a portion closer to the first end surface 7a than the stepped portion. The width of the end surface where the portion on the second end surface 7b side of the via electrode 27 is in contact with the stepped portion is narrower than the width of the end surface where the portion on the first end surface 7a side of the via electrode 27 is in contact with the stepped portion. ing. Further, the side surface 27 c does not have a step portion between the protruding portion 29 and the portion of the side surface 27 c closer to the first end surface 7 a than the protruding portion 29. For this reason, when the bumps 8 are joined, stress is unlikely to concentrate on the overhanging portion 29. Therefore, also in the present embodiment, damage is unlikely to occur around the via electrode 27 as in the first embodiment. In addition, since the via electrode 27 has the protruding portion 29, the via electrode 27 is difficult to come off.

FIG. 8 is an enlarged front sectional view of the vicinity of the via electrode of the acoustic wave device according to the first modification of the second embodiment.

This modification is different from the second embodiment in that it has a plurality of overhang portions. In addition to the overhang portion 29 arranged in the same manner as the second embodiment, the via electrode 117 includes an overhang portion 119 provided so that the stepped portion is located at the boundary between the cover layer 6 and the support layer 5. Have. Even in this case, the via electrode 117 is hard to come off and is not easily damaged around the via electrode 117.

FIG. 9 is an enlarged front cross-sectional view of the vicinity of the via electrode of the acoustic wave device according to the second modification of the second embodiment.

This modification is different from the second embodiment in that the protruding portion 129 of the via electrode 127 reaches the outside of the imaginary line A in the via electrode 127. Even in this case, when the via electrode 127 is projected in the second direction, the side surface 127c has a curved portion. Therefore, the stress can be effectively dispersed as in the second embodiment, and the damage around the via electrode 127 hardly occurs. In addition, the via electrode 127 is difficult to come off.

Thus, the configuration of the present invention is not limited to the configuration in which all of the first side surface portion of the via electrode is located inside the imaginary line in the via electrode. However, as in the second embodiment shown in FIG. 7, it is preferable that all of the first side surface portions 27 d are located on the inner side of the imaginary line A. Thereby, the distance between all the portions of the side surface 27c of the via electrode 27 and the hollow space can be increased. Therefore, damage is less likely to occur around the via electrode 27.

FIG. 10 is a front sectional view of the acoustic wave device according to the third embodiment.

This embodiment is different from the first embodiment in that the first layer 35 covers the IDT electrode 3. In addition, the 2nd layer 36 is provided on the 1st layer 35 similarly to the cover layer of 1st Embodiment. Except for the above points, the elastic wave device 31 has the same configuration as the elastic wave device 1 of the first embodiment.

Also in this embodiment, the via electrode 7 has the same configuration as that of the first embodiment. Therefore, the distance between the surface of the first layer 35 and the second layer 36 on the outside of the acoustic wave device 31 and the side surface 7c of the via electrode 7 is long. Therefore, damage is unlikely to occur around the via electrode 7.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 2 ... Piezoelectric substrate 3 ... IDT electrode 4 ... Electrode land 5 ... Support layer 5a ... Opening part 6 ... Cover layer 6a ... Inner layer 6b ... Outer layer 7 ... Via

electrode

7a, 7b ... 1st, 2nd end surface 7c ...

side surfaces

7d, 7e ... first and second side surface portions 8 ... bumps 17A to 17D ... first to fourth connection points 27 ... via electrodes 27c ... side surface 27d ... first side surface portion 29 ... projecting portion 31 ... Elastic wave device 35, 36 ... 1st, 2nd layer 107 ... Via electrode 107c ... Side surface 117 ... Via electrode 119 ... Overhang part 127 ... Via electrode 127c ... Side surface 129 ... Overhang part 207 ... Via electrode 207c ... Side surface 207d ... First 1 side surface portion 217... Via electrode 217 c... Side surface 217 d... First side surface portion 217 f.

Claims

A piezoelectric substrate;
A functional electrode provided on the piezoelectric substrate;
A first layer provided on the piezoelectric substrate;
A second layer provided on the first layer;
A first end face penetrating through the first layer and the second layer and located on the piezoelectric substrate side; a second end face located on the opposite side of the first end face; A via electrode having a side surface connecting the first end surface and the second end surface;
With
In the via electrode, the area of the second end face is larger than the area of the first end face,
A direction in which the via electrode passes through the first layer and the second layer is a first direction, an arbitrary direction orthogonal to the first direction is a second direction, and the via electrode is The elastic wave device, wherein the shape of the side surface of the via electrode includes a shape curved inward in the via electrode when projected in the second direction.
When the via electrode is projected in the second direction, the side surface of the via electrode is connected to the first end surface and the second end surface, and one side surface portion and the other surface that face each other Having side portions,
The one side surface portion has a first connection point connected to the first end surface, and a second connection point connected to the second end surface,
The one side surface portion is located at a portion other than the first connection point and the second connection point rather than the imaginary line connecting the first connection point and the second connection point by a straight line. The elastic wave device according to claim 1, which is located inside the electrode.
The elastic wave device according to claim 1 or 2, wherein when the via electrode is projected in the second direction, all of the side surfaces of the via electrode are curved inwardly in the via electrode.
The elastic wave device according to claim 1 or 2, wherein the shape of the side surface of the via electrode includes a linear shape when the via electrode is projected in the second direction.
When the via electrode is projected in the second direction, the side surface of the via electrode has a shape in which the second end surface is curved inward in the via electrode, and the first end surface is linear. The elastic wave device according to claim 4, which has a shape.
The side surface of the via electrode has an overhanging portion projecting to the outside of the via electrode;
The elastic wave according to any one of claims 1 to 5, wherein the side surface does not have a stepped portion between the protruding portion and a portion of the side surface closer to the first end surface than the protruding portion. apparatus.
The elastic wave according to any one of claims 1 to 6, wherein the second layer includes an inner layer provided on the first layer and an outer layer provided on the inner layer. apparatus.
The first layer has an opening surrounding the functional electrode in plan view;
The second layer is provided on the first layer so as to cover the opening;
A hollow space surrounded by the piezoelectric substrate, the first layer and the second layer is provided;
The elastic wave device according to any one of claims 1 to 7, wherein the functional electrode is disposed in the hollow space.
The elastic wave device according to any one of claims 1 to 7, wherein the first layer is provided on the piezoelectric substrate so as to cover the functional electrode.
10. The acoustic wave device according to claim 1, wherein the functional electrode is an IDT electrode and uses a surface acoustic wave.