JP7642971B2 - Electronic device and manufacturing method thereof, filter and multiplexer - Google Patents

Description

The present invention relates to an electronic device and its manufacturing method, a filter, and a multiplexer, for example, an electronic device having wiring penetrating a substrate and its manufacturing method, a filter, and a multiplexer.

Acoustic wave devices using a composite substrate in which a piezoelectric substrate is bonded to the upper surface of a support substrate are known (e.g., Patent Documents 1 to 3). It is known that a first through-hole is formed penetrating the piezoelectric substrate from the upper surface of the composite substrate, a first connection electrode is formed in the first through-hole, a second through-hole is formed penetrating the support substrate from the lower surface of the composite substrate, and a second connection electrode that connects to the first connection electrode is formed in the second through-hole (e.g., Patent Document 3).

JP 2017-157922 A JP 2017-169139 A JP 2011-130385 A

When a through hole is formed in a support substrate, the width of the through hole narrows toward the tip. Therefore, if the cross-section of the through hole on one side of the support substrate has a desired area, the cross-section of the through hole on the other side of the support substrate becomes larger. This results in an increase in the size of the acoustic wave device.

The present invention was developed in consideration of the above problems, and aims to reduce the size.

The present invention is an electronic device comprising: a single support substrate having a first surface and a second surface facing the first surface; a functional element provided on the first surface of the support substrate without a piezoelectric substrate ; a first metal layer electrically connected to the functional element, embedded in the support substrate and exposed on the first surface side, the first metal layer narrowing in width from the first surface to the second surface; a second metal layer overlapping the first metal layer in a planar view, contacting the first metal layer within the support substrate, embedded in the support substrate and exposed on the second surface, the second metal layer having a minimum cross-sectional area in a planar view greater than a cross-sectional area of the first metal layer at a contact surface in contact with the first metal layer; and a terminal overlapping the second metal layer in a planar view, contacting the second metal layer, and provided on the second surface, wherein the height of the first metal layer is smaller than the height of the second metal layer, and the second metal layer comprises an adhesion layer on the contact surface and a surface in contact with the support substrate, and does not comprise an adhesion layer on a surface in contact with the terminal.

In the above configuration , the semiconductor device may further include wiring that electrically connects the functional element and the first metal layer, and the functional element may be a piezoelectric element.

In the above configuration, the functional element can be a piezoelectric thin film resonator provided on the first surface.

In the above configuration, the surface of the second metal layer facing the terminal and the second surface can be flat .

In the above configuration, the second metal layer may be configured so that its width narrows from the second surface toward the first surface.

In the above configuration, the support substrate can be a sapphire substrate, a spinel substrate, a quartz substrate, or a crystal substrate.

The present invention is a filter including the above electronic device.

The present invention is a multiplexer including the above filter.

The present invention is a method for manufacturing an electronic device, comprising the steps of: forming a first hole in a single support substrate having a first surface and a second surface facing the first surface, the first surface being provided with a functional element; forming a first metal layer to be embedded in the first hole; polishing or grinding the second surface so as not to expose the first metal layer; forming a second hole from the second surface to the first metal layer after the polishing or grinding step; and forming a second metal layer that is embedded in the second hole and has a minimum cross-sectional area in a plan view that is greater than the cross-sectional area of the first metal layer at the contact surface that contacts the first metal layer.

The present invention allows for miniaturization.

1A and 1B are a cross-sectional view and a plan view of an acoustic wave device in accordance with a first embodiment. FIG. 2A is a plan view of the acoustic wave element in the first embodiment, and FIG. 2B is a cross-sectional view of a via wiring. FIG. 3 is a cross-sectional view of an acoustic wave device in accordance with a first modification of the first embodiment. 4A to 4D are cross-sectional views (part 1) illustrating a method for manufacturing an acoustic wave device in accordance with a first modified example of the first embodiment. 5A to 5D are cross-sectional views (part 2) illustrating a method for manufacturing an acoustic wave device in accordance with a first modification of the first embodiment. 6A to 6D are cross-sectional views (part 3) illustrating a method for manufacturing an acoustic wave device in accordance with a first modification of the first embodiment. 7A to 7C are cross-sectional views showing a manufacturing method in the vicinity of a via wiring in Comparative Example 1. 8A to 8D are cross-sectional views showing a manufacturing method in the vicinity of the via wiring in the first embodiment. 9A and 9B are cross-sectional views of acoustic wave devices according to second and third modifications of the first embodiment. FIG. 10A is a cross-sectional view of an acoustic wave device in accordance with a fourth modified example of the first embodiment, and FIG. 10B is a cross-sectional view of an acoustic wave element. FIG. 11 is a cross-sectional view of an acoustic wave device in accordance with a fifth modification of the first embodiment. FIG. 12A is a circuit diagram of a filter in accordance with the second embodiment, and FIG. 12B is a circuit diagram of a duplexer in accordance with a first modified example of the second embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings, using an acoustic wave device as an example of an electronic device.

1(a) and 1(b) are a cross-sectional view and a plan view of an acoustic wave device according to a first embodiment. FIG. 1(b) mainly shows a support substrate 10, a piezoelectric substrate 11, and an annular metal layer 30.

As shown in Fig. 1(a) and Fig. 1(b), a piezoelectric substrate 11 is bonded onto an upper surface 51 of a support substrate 10. The support substrate 10 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 11 is, for example, a lithium tantalate substrate or a lithium niobate substrate. The linear expansion coefficient of the support substrate 10 is smaller than that of the piezoelectric substrate 11.

The acoustic wave element 12 and the wiring 14 are provided on the upper surface 53 of the piezoelectric substrate 11. A hole 15c is provided penetrating the piezoelectric substrate 11. A metal layer 17 is embedded in the hole 15c. The upper surface of the metal layer 17 and the upper surface 53 of the piezoelectric substrate 11 are substantially flat. The wiring 14 is in contact with the upper surface of the metal layer 17. A through hole 15 is provided penetrating the support substrate 10. The through hole 15 includes holes 15a and 15b. A via wiring 16 is embedded in the through hole 15. The via wiring 16 includes a metal layer 16a embedded in the hole 15a and a metal layer 16b embedded in the hole 15b.

A terminal 18 is provided on the lower surface 52 of the support substrate 10. The terminal 18 is a foot pad for connecting the acoustic wave element 12 to the outside. The via wiring 16 and the metal layer 17 electrically connect the terminal 18 to the wiring 14. The wiring 14, the via wiring 16, the metal layer 17, and the terminal 18 are metal layers such as a copper layer, an aluminum layer, a platinum layer, a nickel layer, or a gold layer.

The piezoelectric substrate 11 is removed from the periphery of the support substrate 10. An annular metal layer 30 is provided on the support substrate 10 so as to surround the piezoelectric substrate 11. An annular bonding layer 32 is provided on the annular metal layer 30. A lid 34 is provided on the annular bonding layer 32. The annular bonding layer 32 bonds the annular metal layer 30 and the lid 34. The annular metal layer 30 is, for example, a nickel layer or a copper layer. The annular bonding layer 32 is, for example, a solder such as tin-silver or tin-silver-copper. The lid 34 is, for example, a metal plate such as Kovar or an insulating plate such as a sapphire substrate. The annular metal layer 30, the annular bonding layer 32, and the lid 34 seal the acoustic wave element 12 in the gap 26.

2(a) is a plan view of the acoustic wave element in the first embodiment, and FIG. 2(b) is a cross-sectional view of the via wiring. 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 a piezoelectric substrate 11. The IDT 40 has a pair of comb electrodes 40a facing each other. The comb electrode 40a has a plurality of electrode fingers 40b and a bus bar 40c connecting the plurality of electrode fingers 40b. The reflectors 42 are provided on both sides of the IDT 40. The IDT 40 excites a surface acoustic wave on the piezoelectric substrate 11. The wavelength of the acoustic wave is approximately equal to the pitch of the electrode fingers 40b of one of the pair of comb electrodes 40a. In other words, the wavelength of the acoustic wave is approximately equal to twice the pitch of the electrode fingers 40b of the pair of comb electrodes 40a. The IDT 40 and the reflector 42 are formed, for example, from 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 11 to cover the IDT 40 and the reflector 42.

As shown in FIG. 2(b), the side of the metal layer 17 is tapered, and the cross section of the metal layer 17 becomes smaller from the upper surface 53 of the piezoelectric substrate 11 toward the upper surface 51 of the support substrate 10. The interior angle θ3 between the upper surface and the side of the metal layer 17 is an acute angle. As a result, the width D6 at the lower surface of the metal layer 17 is smaller than the width D5 at the upper surface of the metal layer 17.

The metal layer 16a is tapered, and the cross section becomes smaller from the upper surface 51 to the lower surface 52 of the support substrate 10. The interior angle θ1 between the upper surface and the side of the metal layer 16a is an acute angle. The width D2 at the lower surface of the metal layer 16a is smaller than the width D1 at the upper surface of the metal layer 16a. The side of the metal layer 16b is tapered, and the cross section of the metal layer 16b becomes smaller from the lower surface 52 to the upper surface 51 of the support substrate 10. The interior angle θ2 between the lower surface and the side of the metal layer 16b is an acute angle. The width D4 at the upper surface of the metal layer 16b is smaller than the width D3 at the lower surface of the metal layer 16b. The width D6 is larger than D1, and the width D4 is larger than D2.

The support substrate 10 and the piezoelectric substrate 11 are, for example, a sapphire substrate and a 42° rotated Y-cut X-propagation lithium tantalate substrate, respectively. The thickness T0 of the support substrate 10 is greater than the thickness T1 of the piezoelectric substrate 11. The thicknesses T0 and T1 of the support substrate 10 and the piezoelectric substrate 11 are, for example, 50 μm to 120 μm and 0.1 μm to 20 μm, respectively.

The metal layers 16a, 16b and 17 are, for example, copper layers. The height H2 of the metal layer 16b is, for example, smaller than the height H1 of the metal layer 16a, and is, for example, 5 μm to 20 μm. The width D5 of the upper surface of the metal layer 17 is, for example, larger than the width D1 of the upper surface of the metal layer 16a. The width D3 of the lower surface of the metal layer 16b is, for example, larger than the width D2 of the lower surface of the metal layer 16a. For the sake of the bondability and contactability between the metal layers 16a and 16b, it is preferable that the width D2 be 10 μm or more. The widths D1, D2 and D5 are, for example, 30 μm, 15 μm and 74 μm, respectively. The angle θ1 is, for example, 88° to 80°. The angles θ2 and θ3 are, for example, 45° to 80°, respectively.

[Modification 1 of Example 1]
3 is a cross-sectional view of an acoustic wave device according to a first modification of the first embodiment. As shown in FIG. 3, in the first modification of the first embodiment, the metal layer 17 is not embedded in the hole 15c. The wiring 14 is provided on the side and bottom surface of the hole 15c, and contacts the metal layer 16a at the bottom surface. The other configurations are the same as those of the first embodiment, and therefore description thereof will be omitted.

[Manufacturing method of modified example 1 of embodiment 1]
4(a) to 6(d) are cross-sectional views showing a method for manufacturing an acoustic wave device according to Modification 1 of Example 1. As shown in Fig. 4(a), a laser beam is irradiated onto an upper surface 51 of a support substrate 10 to form a hole 15a. When the hole 15a is formed by irradiating the laser beam, the side surface of the hole 15a has a tapered shape.

As shown in FIG. 4B, a seed layer 16c is formed on the inner surface of the hole 15a and the upper surface of the support substrate 10, for example, by sputtering. A plating layer 16d is formed on the seed layer 16c, for example, by plating. The seed layer 16c and the plating layer 16d are made of the same metal material, for example, a copper layer. An adhesion layer such as a titanium layer may be provided between the seed layer 16c and the support substrate 10. The plating layer 16d and the seed layer 16c on the upper surface 51 are planarized, for example, by CMP (Chemical Mechanical Polishing) so that the upper surface 51 of the support substrate 10 is exposed. As a result, the seed layer 16c and the plating layer 16d form a metal layer 16a embedded in the hole 15a. In the following drawings, the seed layer 16c and the plating layer 16d are omitted from the illustration and are illustrated as the metal layer 16a.

As shown in FIG. 4(c), the upper surface 51 of the support substrate 10 and the lower surface of the piezoelectric substrate 11 are bonded at room temperature using, for example, a surface activation method. The support substrate 10 and the piezoelectric substrate 11 may be directly bonded via an amorphous layer of a few nm. Alternatively, they may be indirectly bonded via an insulating layer such as aluminum oxide, silicon oxide, or silicon oxide doped with fluorine. The upper surface 53 of the piezoelectric substrate 11 is flattened, for example, by a CMP method. This allows the piezoelectric substrate 11 to have the desired thickness. As shown in FIG. 4(d), the acoustic wave element 12 is formed on the upper surface 53 of the piezoelectric substrate 11 using, for example, a sputtering method or a vacuum deposition method.

As shown in FIG. 5(a), holes 15c and openings 15d penetrating the piezoelectric substrate 11 are formed using, for example, wet or dry etching. At this time, the support substrate 10 is hardly etched. Holes 15c are formed so as to overlap with the metal layer 16a, and the metal layer 16a is exposed from the holes 15c. Openings 15d are formed on the periphery of the support substrate 10 so as to surround the acoustic wave element 12. The sides of holes 15c and openings 15d are tapered.

As shown in FIG. 5(b), wiring 14 is formed on the inner surface of hole 15c and on top surface 53 of piezoelectric substrate 11 by, for example, sputtering or vacuum deposition. Wiring 14 electrically connects acoustic wave element 12 and metal layer 16a. Because the side surface of hole 15c is tapered, wiring 14 does not break at hole 15c.

As shown in FIG. 5(c), an annular metal layer 30 and an annular bonding layer 32 are formed on the upper surface 51 of the support substrate 10 in the opening 15d, for example, by plating. As shown in FIG. 5(d), a lid 34 is placed on the annular bonding layer 32 and heated, thereby bonding the annular bonding layer 32 and the lid 34. This seals the acoustic wave element 12 in the gap 26.

As shown in FIG. 6(a), the lower surface 52 of the support substrate 10 is polished or ground, for example. This makes the support substrate 10 thinner. The metal layer 16a is not exposed from the lower surface 52.

As shown in FIG. 6(b), a hole 15b is formed in the lower surface 52 of the support substrate 10 by, for example, wet or dry etching or using laser light. The hole 15b is formed so as to overlap the metal layer 16a, and the metal layer 16a is exposed from the hole 15b. The side surface of the hole 15b is tapered.

As shown in FIG. 6(c), a seed layer 16c is formed on the inner surface of the hole 15b and the lower surface of the support substrate 10, for example, by sputtering. A plating layer 16d is formed under the seed layer 16c, for example, by plating. The seed layer 16c and the plating layer 16d are made of the same metal material, for example, a copper layer. An adhesion layer such as a titanium layer may be provided between the seed layer 16c and the support substrate 10. The plating layer 16d and the seed layer 16c under the lower surface 52 are planarized, for example, by CMP, so that the lower surface 52 of the support substrate 10 is exposed. As a result, the seed layer 16c and the plating layer 16d form a metal layer 16b embedded in the hole 15b. In the following drawings, the seed layer 16c and the plating layer 16d are omitted and are illustrated as the metal layer 16b.

As shown in FIG. 6(d), the terminal 18 is formed on the lower surface 52 of the support substrate 10 by, for example, sputtering or vacuum deposition. The terminal 18 is, for example, a titanium layer, a copper layer, a nickel layer, and a gold layer from the support substrate 10 side. The support substrate 10 and the lid 34 are cut by, for example, dicing. In this manner, the acoustic wave device according to the first modification of the first embodiment is manufactured.

Figures 7(a) to 7(c) are cross-sectional views showing a manufacturing method near the via wiring in Comparative Example 1. As shown in Figure 7(a), the thickness T0' of the support substrate 10 is, for example, 400 μm to 500 μm. A metal layer 17 is formed in the hole 15c of the piezoelectric substrate 11, and a metal layer 16a is formed in the hole 15a of the support substrate 10. The metal layer 16a does not penetrate the support substrate 10. The height H1' of the metal layer 16a is, for example, 125 μm. The width of the upper surface of the metal layer 16a is D1.

As shown in FIG. 7(b), the lower surface 52 of the support substrate 10 is polished or ground. As a result, the thickness T0 of the support substrate 10 becomes approximately 75 μm. The metal layer 16a is exposed on the lower surface 52 of the support substrate 10. The width of the lower surface of the metal layer 16a is D2. As shown in FIG. 7(c), a terminal 18 that contacts the metal layer 16a is formed on the lower surface 52 of the support substrate 10.

The cross section of the hole 15a becomes smaller from the upper surface 51 to the lower surface 52. This is because the hole 15a is formed from the upper surface 51. For example, if the hole 15a is formed using a laser beam, the angle θ1 between the upper surface and the side of the metal layer 16a is 80° to 85°. If the hole 15a is formed using an etching method, the angle θ1 becomes smaller. If the width D2 of the lower surface of the metal layer 16a becomes smaller, the bond between the metal layer 16a and the terminal 18 decreases. Also, the contact resistance between the metal layer 16a and the terminal 18 decreases. Therefore, it is preferable that the width D2 is, for example, 10 μm or more.

The thickness T0 of the support substrate 10 is required to be equal to or greater than the desired thickness in order to suppress warping of the support substrate 10 and/or ensure its strength. For example, if the thickness T0 is 75 μm, the width D2 is 15 μm, and the angle θ1 is 84°, then the width D1 is 40 μm. The width D5 is larger than the width D2, for example, 84 μm. In this way, the acoustic wave device becomes larger.

In addition, in FIG. 7(b), cracks 64 may form in the support substrate 10 near the metal layer 16a. This is because the support substrate 10 is hard and the metal layer 16a is soft.

Figures 8(a) to 8(d) are cross-sectional views showing a manufacturing method near the via wiring in Example 1. As shown in Figure 8(a), the thickness T0' of the support substrate 10 is, for example, 400 μm to 500 μm. A metal layer 17 is formed in the hole 15c of the piezoelectric substrate 11, and a metal layer 16a is formed in the hole 15a of the support substrate 10. The height H1 of the metal layer 16a is, for example, 65 μm. The width of the lower surface of the metal layer 16a is D2.

As shown in FIG. 8(b), the lower surface 52 of the support substrate 10 is polished or ground. As a result, the thickness T0'' of the support substrate 10 becomes, for example, 76 μm. The metal layer 16a is not exposed on the lower surface 52 of the support substrate 10. As shown in FIG. 8(c), a hole 15b is formed from the lower surface 52 of the support substrate 10. The height H2' of the hole 15b is, for example, 11 μm. A metal layer 16b' is formed on the inner surface of the hole 15b and below the lower surface 52 of the support substrate 10, for example, by using a plating method.

As shown in FIG. 8(d), the metal layer 16b' on the lower surface 52 of the support substrate 10 is polished or ground. As a result, the lower surface 52 of the support substrate 10 is exposed, and the metal layer 16b is embedded in the hole 15b. At this time, the lower surface 52 of the support substrate 10 is polished or ground, and the thickness T0 of the support substrate 10 becomes, for example, 75 μm, and the height H2 of the metal layer 16b becomes 10 μm. At this time, the lower surface 52 of the support substrate 10 does not need to be polished or ground very much. The via wiring 16 is formed from the metal layers 16a and 16b. A terminal 18 that contacts the metal layer 16b is formed on the lower surface 52 of the support substrate 10.

In Example 1, if the width D2 at the contact surface where metal layers 16a and 16b come into contact is 15 μm, the height H1 is 65 μm, and the angle θ1 is 84°, then the width D1 is 30 μm. If the difference between widths D1 and D5 is approximately the same as in Comparative Example 1, then the width D5 is 74 μm. In this way, the width D5 can be made smaller than in Comparative Example 1, making it possible to miniaturize the acoustic wave device. Since the width D3 of metal layer 16b that contacts terminal 18 can be made larger than in Comparative Example 1, the bonding strength between metal layer 16b and terminal 18 can be increased, and the contact resistance between metal layer 16b and terminal 18 can be reduced.

In FIG. 8(b), a crack 64 may be formed in the support substrate 10 near the metal layer 16a. As shown in FIG. 8(c), the crack 64 in the support substrate 10 can be removed by forming the hole 15b larger than the width D2 of the metal layer 16a.

The shear stress caused by thermal stress is the greatest at the interface between the support substrate 10 and the piezoelectric substrate 11. For this reason, as in Patent Document 3, if the interface where the via wiring is thinnest and where the metal layer is bonded is located near the interface between the support substrate 10 and the piezoelectric substrate 11, the shear stress may cause the metal layer to peel off.

In Example 1, the thinnest part of the via wiring 16 and the contact surface where the metal layers 16a and 16b are joined are sufficiently separated from the interface between the support substrate 10 and the piezoelectric substrate 11. Therefore, peeling caused by shear stress can be suppressed. It is preferable that the height H1 of the metal layer 16a is equal to or greater than the height H2 of the metal layer 16b. This makes it possible to suppress peeling of the metal layers 16a and 16b caused by shear stress. It is preferable that the height H1 is equal to or greater than twice the height H2, and more preferably equal to or greater than three times the height H2.

[Modification 2 of Example 1]
FIG. 9A is a cross-sectional view of an acoustic wave device according to a second modification of the first embodiment. As shown in FIG. 9A, in the second modification of the first embodiment, the piezoelectric substrate 11 is indirectly bonded to the upper surface of the support substrate 10 via a bonding layer 13. The bonding layer 13 is, for example, an insulating film such as a silicon oxide film. The thickness of the bonding layer 13 is, for example, 1 μm. The piezoelectric substrate 11 is bonded at room temperature on the bonding layer 13. An aluminum oxide film having a thickness of several tens of nm may be provided between the bonding layer 13 and the piezoelectric substrate 11. A silicon nitride film may be provided between the bonding layer 13 and the support substrate 10. When the bonding layer 13 is an insulating film such as a silicon oxide film, a metal film such as a titanium film may be provided in the silicon oxide film. The titanium film bonds the silicon oxide films together. When a metal film such as a titanium film is provided, it is preferable that an insulating film such as a silicon oxide film is provided between the side surface of the hole 15c and the wiring 14. This makes it possible to suppress an electrical short circuit between the metal film and the wiring 14. The other configurations are the same as those of the first modification of the first embodiment, and a description thereof will be omitted.

[Modification 3 of Example 1]
9B is a cross-sectional view of an acoustic wave device according to a third modification of the first embodiment. As shown in FIG. 9B, in the third modification of the first embodiment, the metal layer 16b is not provided, and the terminal 18 is embedded in the hole 15b. The other configurations are the same as those in the first embodiment, and the description thereof will be omitted. In the first and second modifications of the first embodiment, the terminal 18 may be embedded in the hole 15b.

[Fourth Modification of the First Embodiment]
Fig. 10(a) is a cross-sectional view of an acoustic wave device according to Modification 4 of Example 1, and Fig. 10(b) is a cross-sectional view of an acoustic wave element. As shown in Fig. 10(a) , in Modification 4 of Example 1, piezoelectric substrate 11 is not bonded to upper surface 51 of support substrate 10. Acoustic wave element 12 and wiring 14 are provided on upper surface 51 of support substrate 10. The other configurations are the same as those of Example 1 and Modifications 1 and 2, and therefore description thereof will be omitted.

10B, the acoustic wave element 12 is a piezoelectric thin film resonator. A piezoelectric film 46 is provided on a support substrate 10. A lower electrode 44 and an upper electrode 48 are provided to sandwich the piezoelectric film 46. A gap 45 is formed between the lower electrode 44 and the support substrate 10. The region where the lower electrode 44 and the upper electrode 48 face each other, sandwiching at least a part of the piezoelectric film 46, is a resonance region 47. In the resonance region 47, the lower electrode 44 and the upper electrode 48 excite an acoustic wave in a thickness longitudinal vibration mode in the piezoelectric film 46. The support substrate 10 is, for example, a sapphire substrate, a spinel substrate, an alumina substrate, a glass substrate, a quartz 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. An acoustic reflection film that reflects the acoustic wave may be provided instead of the gap 45.

In the fourth modification of the first embodiment, the shear stress caused by the difference in the linear expansion coefficient between the piezoelectric substrate 11 and the support substrate 10 described in the first embodiment is small. Therefore, the height of the metal layer 16a may be smaller than the height of the metal layer 16b.

[Fifth Modification of the First Embodiment]
11 is a cross-sectional view of an acoustic wave device according to a fifth modification of the first embodiment. As shown in FIG. 11, in the fifth modification of the first embodiment, a substrate 20 is mounted on a support substrate 10. The substrate 20 is, for example, a sapphire substrate, an alumina substrate, a spinel substrate, a quartz substrate, a crystal substrate, or a silicon substrate. An acoustic 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 piezoelectric substrate 11 via bumps 28. The bumps 28 are, for example, gold bumps, solder bumps, or copper bumps. The bumps 28 are bonded to the wirings 14 and 24.

A circular metal layer 35 is embedded in the opening 15d at the periphery of the support substrate 10. A circular metal layer 36 is provided on the circular metal layer 35. The circular metal layers 35 and 36 are, for example, a copper layer and a nickel layer, respectively. A sealing portion 37 is provided on the circular metal layer 36 so as to surround the substrate 20. The sealing portion 37 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 37 is bonded to the circular metal layer 36. A flat lid 38 is provided on the upper surface of the substrate 20 and on the upper surface of the sealing portion 37. The lid 38 is, for example, a metal plate such as a Kovar plate or an insulating plate. A protective film 39 is provided so as to cover the lid 38 and the sealing portion 37. The protective film 39 is a metal film such as a nickel film or an insulating film.

Acoustic wave element 12 faces substrate 20 via gap 26. Acoustic wave element 22 faces piezoelectric substrate 11 via gap 26. Acoustic wave elements 12 and 22 are sealed by sealing portion 37, support substrate 10, substrate 20, and lid 38. Bump 28 is surrounded by gap 26. Terminal 18 is electrically connected to acoustic wave element 12 via via wiring 16 and wiring 14, and is further electrically connected to acoustic wave element 22 via bump 28 and wiring 24. The other configurations are the same as in Example 1, and a description thereof will be omitted.

As in Variation 5 of Example 1, the substrate 20 may be mounted on the support substrate 10 of Example 1 and Variations 1 to 4 thereof. Although an example of a piezoelectric thin film resonator has been described as the acoustic wave element 22, the acoustic wave element 22 may be a surface acoustic wave resonator. Although an example of an acoustic 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.

According to the first embodiment and its modified example, an elastic wave element 12 (functional element) is provided on the upper surface 51 (first surface) of a single support substrate 10. The metal layer 16a or the terminal 18 (first metal layer) is conductively connected to the elastic wave element 12, is embedded in the support substrate 10, is exposed on the upper surface 51 side, and is narrower (e.g., the cross section is gradually smaller) from the upper surface 51 toward the lower surface 52 (the second surface facing the first surface). The metal layer 16b (second metal layer) overlaps the metal layer 16a in a plan view, contacts the metal layer 16a in the support substrate 10, is embedded in the support substrate 10, and is exposed from the lower surface 52. The minimum cross-sectional area of the metal layer 16b in a plan view is larger than the cross-sectional area of the metal layer 16a at the contact surface where the metal layer 16a (or the terminal 18) and 16b contact each other.

As a manufacturing method, as shown in FIG. 4(a), a hole 15a (first hole) is formed that does not penetrate the support substrate 10 from the upper surface 51 (first surface) and narrows (e.g., the cross section becomes gradually smaller) from the upper surface 51 to the lower surface 52 (second surface). As shown in FIG. 4(b), a metal layer 16a (first metal layer) is formed to be embedded in the hole 15a. As shown in FIG. 6(a), the lower surface 52 is polished or ground so that the metal layer 16a is not exposed. As shown in FIG. 6(b), a hole 15b (second hole) is then formed that reaches the metal layer 16a from the lower surface 52. As shown in FIG. 6(c), a metal layer 16b (second metal layer) is formed that is embedded in the hole 15b and has a minimum cross-sectional area in a plan view that is greater than the cross-sectional area of the metal layer 16a at the contact surface in contact with the metal layer 16a.

In Comparative Example 1 in FIG. 7(c), the cross section of the metal layer 16a is smallest at the bottom surface 52. If the thickness T0 of the support substrate 10 is set to the desired thickness, the acoustic wave device will be large. In Example 1 and its modified example, as shown in FIG. 8(d), the smallest cross section of the via wiring 16 is the cross section of the metal layer 16a at the surface where the metal layers 16a and 16b contact each other. This allows the acoustic wave device to be miniaturized even if the thickness T0 of the support substrate 10 is the same as in Comparative Example 1. In addition, the cracks 64 and the like of the support substrate 10 formed near the metal layer 16a in FIG. 7(b) of Comparative Example 1 can be removed by the holes 15b.

As in Example 1 and its modified examples 1 to 3 and 5, the elastic wave element 12 is provided on the upper surface 53 (third surface) of the piezoelectric substrate 11, and the lower surface (fourth surface facing the third surface) of the piezoelectric substrate 11 is directly or indirectly bonded to the upper surface 51 of the support substrate 10. The wiring 14 and the metal layer 17 (or wiring 14) overlap the metal layer 16a in a plan view and connect the elastic wave element 12 to the metal layer 16a through a hole 15c that penetrates the piezoelectric substrate 11. When the piezoelectric substrate 11 is bonded on the support substrate 10, as in Patent Document 3, if the metal layer is bonded at the interface between the support substrate 10 and the piezoelectric substrate 11, the metal layer may peel off due to shear stress caused by thermal stress. In Example 1 and its modified examples 1 to 3 and 5, the metal layers 16a and 16b are bonded within a single support substrate 10. As a result, the shear stress caused by thermal stress of the support substrate 10 and the piezoelectric substrate 11 at the contact surface between the metal layers 16a and 16b is small. This prevents the metal layers 16a and 16b from peeling off.

The contact surface between the metal layers 16a and 16b is located below the center of the thickness of the support substrate 10. This allows the contact surface to be located away from the interface between the support substrate 10 and the piezoelectric substrate 11. This makes it possible to reduce the shear stress at the contact surface.

Metal layer 17 (third metal layer) is embedded in hole 15c and its surface is approximately flat with upper surface 53. Wiring 14 (fourth metal layer) is provided on the surface of metal layer 17 and upper surface 53, and connects to acoustic wave element 12 (piezoelectric element). In this structure, since metal layer 17 is embedded in hole 15c, the shear stress at the interface between metal layer 17 and 16a becomes large. Since the smallest cross section is located within support substrate 10, the shear stress at the contact surface between metal layers 16a and 16b, which have small cross sections, becomes small.

As in the fourth modification of the first embodiment, the piezoelectric substrate 11 is not provided, and the acoustic wave element 12 may be a piezoelectric thin film resonator provided on the upper surface 51 of the support substrate 10.

As in the first, second, fourth and fifth variations of the first embodiment, the terminal 18 overlaps the metal layer 16b in a plan view, contacts the metal layer 16b and is provided on the lower surface 52. This allows the cross section of the via wiring 16 at the interface between the via wiring 16 and the terminal 18 to be larger than that of the first comparative example. This increases the bonding strength between the via wiring 16 and the terminal 18 and reduces the contact resistance.

The width of the metal layer 16b narrows from the bottom surface 52 to the top surface 51. This increases the contact area between the metal layer 16b and the terminal 18. It also makes it easier to remove cracks 64, etc.

The support substrate is a sapphire substrate, a spinel substrate, a quartz substrate, or a quartz substrate. The sapphire substrate is a substrate mainly composed of single crystal Al ₂ O _3. The spinel substrate is a substrate mainly composed of single crystal or polycrystalline MgAl ₂ O _4. The quartz substrate is a substrate mainly composed of amorphous SiO _2. The quartz substrate is a substrate mainly composed of single crystal SiO _2. In this case, since the support substrate 10 is hard, there is a high possibility that a crack 64 will be formed on the lower surface 52 of the support substrate 10 in FIG. 8(b). Therefore, the crack 64 can be removed by providing a metal layer 16b.

In the first embodiment and its modified example, the acoustic wave element 12 is used as an example of the functional element, but the functional element may be a passive element such as an inductor or a capacitor, an active element including a transistor, or a MEMS element.

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

12B is a circuit diagram of a duplexer according to the first modified example of the second embodiment. As shown in FIG. 12B, a transmission filter 60 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 62 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 60 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 62 passes a signal in the reception band among the high-frequency signals input from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. At least one of the transmission filter 60 and the reception filter 62 can be the filter of the second embodiment. The transmission filter 60 may be formed of the acoustic wave element 12, and the reception filter 62 may be formed of the acoustic wave element 22.

Although a duplexer has been used as an example of a multiplexer, a triplexer or 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 are possible within the scope of the gist of the present invention as described in the claims.

REFERENCE SIGNS LIST 10 Support substrate 11 Piezoelectric substrate 12, 22 Acoustic wave element 14, 24 Wiring 15a, 15b Hole 15c Hole 16 Via wiring 16a, 16b, 17 Metal layer 18 Terminal 20 Substrate 26 Air gap 30 Annular metal layer 32 Annular bonding layer 34 Lid 60 Transmitting filter 62 Receiving filter 51, 53 Upper surface 52 Lower surface

Claims (9)

a single support substrate having a first surface and a second surface opposite to the first surface;
a functional element provided on the first surface of the support substrate without a piezoelectric substrate ;
a first metal layer that is conductively connected to the functional element, is embedded in the support substrate, is exposed on the first surface side, and has a width that narrows from the first surface toward the second surface;
a second metal layer that overlaps the first metal layer in a plan view, that contacts the first metal layer within the support substrate, that is embedded in the support substrate and exposed to the second surface, and that has a minimum cross-sectional area in a plan view that is larger than a cross-sectional area of the first metal layer at a contact surface that contacts the first metal layer;
a terminal provided on the second surface and overlapping the second metal layer in a plan view and in contact with the second metal layer;
Equipped with
the height of the first metal layer is smaller than the height of the second metal layer;
an electronic device in which the second metal layer has an adhesion layer on the contact surface and a surface in contact with the supporting substrate, and does not have an adhesion layer on a surface in contact with the terminal; a wiring electrically connecting the functional element and the first metal layer;
The electronic device according to claim 1 , wherein the functional element is a piezoelectric element. The electronic device according to claim 1, wherein the functional element is a piezoelectric thin film resonator provided on the first surface. The electronic device according to claim 1 , wherein a surface of the second metal layer on the terminal side and the second surface are flat. The electronic device according to claim 1 , wherein the second metal layer has a width that narrows from the second surface to the first surface. The electronic device according to claim 1 , wherein the support substrate is a sapphire substrate, a spinel substrate, a quartz substrate, or a quartz crystal substrate. A filter comprising an electronic device according to any one of claims 1 to 6 . A multiplexer including a filter according to claim 7 . forming a first hole in a single support substrate having a first surface and a second surface facing the first surface, the first surface being provided with a functional element, the first hole narrowing in width from the first surface to the second surface without penetrating the support substrate;
forming a first metal layer embedded in the first hole;
polishing or grinding the second surface so as not to expose the first metal layer;
forming a second hole extending from the second surface to the first metal layer after the polishing or grinding step;
forming a second metal layer embedded in the second hole and having a minimum cross-sectional area in a plan view larger than a cross-sectional area of the first metal layer at a contact surface in contact with the first metal layer;
A method for manufacturing an electronic device comprising the steps of:

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