JP2024179587A - Acoustic Wave Devices, Filters, Multiplexers, and Electronic Components - Google Patents

Abstract

An acoustic wave device capable of suppressing the occurrence of cracks is provided.
[Solution] The acoustic wave device 100 comprises a substrate 10 having an upper surface 11 and a lower surface 12, a via wiring 32 penetrating the substrate 10 from the upper surface 11 to the lower surface 12, a piezoelectric layer 20 provided on the upper surface 11 and having a hole 24 that overlaps the via wiring 32 in a planar view and whose outline is located inside the outline of the via wiring 32 on the upper surface 11, and an acoustic wave element 50 provided on the piezoelectric layer 20 and connected to the via wiring 32.
[Selected Figure] Figure 1

Description

The present invention relates to acoustic wave devices, filters, multiplexers, and electronic components.

A configuration is known in which an elastic wave element provided on a substrate is electrically connected to via wiring that penetrates the substrate (e.g., Patent Documents 1 and 2). Also known is a configuration in which an elastic wave element is sealed in a gap (e.g., Patent Documents 1-5).

JP2020-205500 Public Relations JP2022-44323Publication JP2016-152612Publication JP 2014-143640 A JP 2013-115664 A

In a configuration in which an insulating layer is provided on a substrate and an elastic wave element is provided on the insulating layer, the insulating layer on the via wiring is removed to enable electrical connection between the elastic wave element and the via wiring that penetrates the substrate. In this case, it is preferable to remove a small area of the insulating layer in order to ensure a large area for forming the elastic wave element, etc. However, when the area of the insulating layer to be removed is made small, cracks may occur in the insulating layer due to the difference in the linear expansion coefficient between the substrate and the via wiring.

The present invention was developed in consideration of the above problems, and aims to suppress the occurrence of cracks.

The present invention is an acoustic wave device comprising a substrate having a first surface and a second surface opposite to the first surface, a via wiring penetrating the substrate from the first surface to the second surface, an insulating layer provided on the first surface and having a hole that overlaps the via wiring in a plan view and has an outline located inside the outline of the via wiring on the first surface, and an acoustic wave element provided on the insulating layer and connected to the via wiring.

In the above configuration, the substrate can be made of silicon or sapphire.

In the above configuration, the via wiring can be made of copper, gold, or silver.

In the above configuration, the insulating layer may include a piezoelectric layer, and the acoustic wave element may include a comb electrode provided on the piezoelectric layer.

In the above configuration, the insulating layer can include an intermediate layer provided between the substrate and the piezoelectric layer.

In the above configuration, the intermediate layer may include at least one of an aluminum oxide layer, a silicon oxide layer, a silicon nitride layer, an aluminum nitride layer, an aluminum oxynitride layer, a silicon layer, a titanium oxide layer, and a polysilicon layer.

In the above configuration, the device may include a frame provided on the first surface surrounding the insulating layer, a lid provided on the frame, a sealing portion that seals the acoustic wave element between the insulating layer and the lid, and a terminal provided on the second surface and connected to the via wiring.

In the above configuration, the sealing portion can be configured to seal the acoustic wave element in the gap between the insulating layer and the lid.

In the above configuration, the diameter of the hole can be 0.9 times or less the diameter of the via wiring on the first surface.

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

The present invention is a multiplexer having the filter described above.

The present invention is an electronic component comprising a substrate having a first surface and a second surface opposite to the first surface, a via wiring penetrating the substrate from the first surface to the second surface, an insulating layer provided on the first surface and having a hole that overlaps the via wiring in a plan view and has an outline located inside the outline of the via wiring on the first surface, an element provided on the insulating layer and connected to the via wiring, and a sealing portion that seals the element in a gap on the insulating layer.

The present invention makes it possible to suppress the occurrence of cracks.

FIG. 1 is a cross-sectional view of an acoustic wave device in accordance with a first embodiment. FIG. 2 is a plan view of the acoustic wave device in accordance with the first embodiment. FIG. 3A is a plan view of the acoustic wave element in the first embodiment, and FIG. 3B is a cross-sectional view of another example of the acoustic wave element. FIG. 4A is a circuit diagram of a filter in the first embodiment, and FIG. 4B is a circuit diagram of a duplexer. FIG. 5A is a plan view showing the positional relationship between via wiring and holes in a piezoelectric layer in Example 1, and FIG. 5B is a cross-sectional view taken along line AA of FIG. 5A. 6A to 6C are cross-sectional views (part 1) illustrating a method for manufacturing the acoustic wave device in accordance with the first embodiment. 7A to 7C are cross-sectional views (part 2) illustrating a method for manufacturing the acoustic wave device in accordance with the first embodiment. FIG. 8( a ) is a cross-sectional view of an acoustic wave device according to comparative example 1, FIG. 8( b ) is a plan view showing the positional relationship between the via wiring and the piezoelectric layer in comparative example 1, and FIG. 8( c ) is an enlarged view of area A in FIG. 8( b ). 9(a) is a cross-sectional view of an acoustic wave device according to comparative example 2, FIG. 9(b) is a plan view showing the positional relationship between the via wiring and the piezoelectric layer in comparative example 2, and FIG. 9(c) is an enlarged view of area A in FIG. 9(b). FIG. 10A is a plan view showing the problem in Comparative Example 2, and FIG. 10B is a cross-sectional view taken along line AA in FIG. 10A. FIG. 11 is a cross-sectional view of an acoustic wave device in accordance with the second embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is a cross-sectional view of an acoustic wave device according to a first embodiment. Figure 2 is a plan view of the acoustic wave device according to the first embodiment. In Figure 2, the lid 44 is shown in perspective. For clarity, the cross-section of the acoustic wave device according to the first embodiment is shown in schematic form in Figure 1 (as in the following similar figures), and the frame 42 and wiring 34 are hatched in Figure 2.

As shown in FIG. 1 and FIG. 2, the acoustic wave device 100 according to the first embodiment has a piezoelectric layer 20 bonded to the upper surface 11 of a substrate 10. The substrate 10 is, for example, a sapphire substrate, and has a thickness of 50 μm to 300 μm. The piezoelectric layer 20 is, for example, a single crystal lithium tantalate layer or a single crystal lithium niobate layer, for example, a rotated Y-cut X-propagation lithium tantalate layer or a rotated Y-cut X-propagation lithium niobate layer. The piezoelectric layer 20 has a thickness of, for example, 0.5 μm to 30 μm. The piezoelectric layer 20 may be, for example, a 30° to 50° Y-cut X-propagation lithium tantalate layer. One or more acoustic wave elements 50 are provided on the upper surface of the piezoelectric layer 20.

3(a) is a plan view of the acoustic wave element in the first embodiment, and FIG. 3(b) is a cross-sectional view of another example of the acoustic wave element. As shown in FIG. 3(a), the acoustic wave element 50 is a surface acoustic wave resonator. An IDT (Interdigital Transducer) 51 and a reflector 52 are provided on the upper surface of the piezoelectric layer 20. The IDT 51 has a pair of opposing comb electrodes 53. The comb electrode 53 has a plurality of electrode fingers 54 and a bus bar 55 to which the plurality of electrode fingers 54 are connected. The reflectors 52 are provided on both sides of the IDT 51. The plurality of electrode fingers 54 excite the surface acoustic wave in the piezoelectric layer 20. The pitch of the electrode fingers 54 of one of the pair of comb electrodes 53 is approximately the wavelength λ of the acoustic wave. The pitch D of the plurality of electrode fingers 54 is approximately twice the wavelength λ of the acoustic wave. The IDT 51 and the reflector 52 are formed of a metal film such as aluminum, copper, or molybdenum. A protective film or a temperature compensation film covering the IDT 51 and the reflector 52 may be provided on the upper surface of the piezoelectric layer 20. The comb electrode 53 may have dummy electrode fingers.

3B, the acoustic wave element 50 may be a piezoelectric thin-film resonator. A piezoelectric layer 57 (insulating film) is provided on the substrate 10, and a lower electrode 56 and an upper electrode 58 are provided to sandwich the piezoelectric layer 57. A gap 59 is formed between the lower electrode 56 and the substrate 10. The region where the lower electrode 56 and the upper electrode 58 face each other, sandwiching at least a part of the piezoelectric layer 57, is a resonance region 61. In the resonance region 61, the lower electrode 56 and the upper electrode 58 excite an acoustic wave in the piezoelectric layer 57. The lower electrode 56 and the upper electrode 58 are metal films including, for example, a ruthenium film. The piezoelectric layer 57 is, for example, an aluminum nitride layer, a zinc oxide layer, a single-crystal lithium tantalate layer, or a single-crystal lithium niobate layer. An acoustic reflection film that reflects the acoustic wave may be provided instead of the gap 59.

As shown in Figs. 1 and 2, a terminal 30 is provided on the lower surface 12 of the substrate 10. The terminal 30 is a foot pad for electrically connecting the acoustic wave element 50 to the outside. The terminal 30 is a metal layer containing, for example, copper, aluminum, or gold, and has a thickness of about several µm. For example, the terminal 30 is a laminated film in which, from the substrate 10 side, a copper layer with a thickness of about 2 µm, a nickel layer with a thickness of about 5 µm, and a gold layer with a thickness of about 0.5 µm are laminated.

The substrate 10 is provided with via wiring 32 penetrating from the upper surface 11 to the lower surface 12. The piezoelectric layer 20 has a hole 24 penetrating the piezoelectric layer 20 on the via wiring 32. The hole 24 is provided overlapping the via wiring 32 and is surrounded by the piezoelectric layer 20. The piezoelectric layer 20 has a substantially rectangular shape in a plan view. Therefore, it can be said that the hole 24 is provided in the region of the substantially rectangular piezoelectric layer 20 that overlaps with the via wiring 32. The wiring 34 enters the hole 24 and contacts the via wiring 32. As a result, the acoustic wave element 50 is electrically connected to the terminal 30 via the wiring 34 and the via wiring 32. The via wiring 32 is formed of, for example, copper. The wiring 34 is a metal layer containing, for example, copper, aluminum, or gold, and has a thickness of about several μm. For example, the wiring 34 is a laminated film in which a titanium layer with a thickness of about 1 μm and a gold layer with a thickness of about 3 μm are laminated.

The piezoelectric layer 20 is not provided in the peripheral region of the substrate 10. In a plan view, a frame 42 is provided on the substrate 10 so as to surround the piezoelectric layer 20. The frame 42 is provided on the substrate 10 away from the piezoelectric layer 20. The frame 42 is a metal layer containing, for example, copper, kovar, gold, aluminum, or tungsten. The height of the frame 42 is, for example, about 10 μm to 40 μm, and the width is, for example, about 10 μm to 40 μm. For example, the frame 42 is a laminated film of a titanium layer with a thickness of about 1 μm, a gold layer with a thickness of about 3 μm, a copper layer with a thickness of about 20 μm, a nickel layer with a thickness of about 5 μm, and a gold layer with a thickness of about 1 μm.

The lid 44 is provided on the frame 42 so that a gap 22 is formed between the frame 42 and the substrate 10. The lid 44 is joined to the frame 42 by solder 46. The acoustic wave element 50 is sealed in the gap 22 by a sealing part 40 including the frame 42 and the lid 44. The lid 44 is formed to include a metal layer such as a Kovar layer or a copper layer, and has a thickness of about 10 μm to 20 μm. From the viewpoint of dissipating heat generated from the acoustic wave element 50, it is preferable that the lid 44 is formed to include a metal layer exposed in the gap 22. The lid 44 may be formed to include an insulating layer or a semiconductor layer, and may be formed to include, for example, a sapphire layer, an alumina layer, a silicon layer, a glass layer, or the like.

The frame 42 may be electrically connected to the ground terminal 30 through the via wiring 32. This allows a ground potential to be supplied to the frame 42, providing a shielding effect to the sealing portion 40. In addition, heat generated from the acoustic wave element 50 can be transferred from the sealing portion 40 to the terminal 30 through the via wiring 32, improving the heat dissipation effect. The frame 42 and the lid 44 are not electrically connected to the acoustic wave element 50 on the substrate 10.

The filter 60 is formed by a plurality of elastic wave elements 50 formed on the upper surface of the piezoelectric layer 20. That is, the series resonators S1 to S4 connected in series between the input terminal 30 and the output terminal 30, and the parallel resonators P1 to P3 connected in parallel are formed by the elastic wave elements 50. FIG. 4(a) is a circuit diagram of the filter in the first embodiment. As shown in FIG. 4(a), the filter 60 has one or more series resonators S1 to S4 connected in series between the input terminal Tin and the output terminal Tout, and one or more parallel resonators P1 to P3 connected in parallel. The series resonators S1 to S4 and the parallel resonators P1 to P3 may all be elastic wave elements 50, or at least one of them may be an elastic wave element 50. The number of series resonators and parallel resonators can be set appropriately. Although a ladder type filter has been described as an example of the filter, the filter may also be a multimode type filter.

A duplexer may also be formed by a filter including the acoustic wave element 50. FIG. 4B is a circuit diagram of a duplexer. As shown in FIG. 4B, in the duplexer 70, a transmission filter 72 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 74 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 72 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 74 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 72 and the reception filter 74 can be the filter 60. Although a duplexer is shown as an example of a multiplexer, a triplexer or a quadplexer may also be used.

Figure 5(a) is a plan view showing the positional relationship between the via wiring and the hole in the piezoelectric layer in Example 1, and Figure 5(b) is a cross-sectional view taken along the line A-A of Figure 5(a). As shown in Figures 5(a) and 5(b), the hole 24 in the piezoelectric layer 20 is provided so as to overlap the via wiring 32 in a plan view, and the contour 25 is located inside the contour 33 of the via wiring 32 on the upper surface 11 of the substrate 10. Therefore, the contour 25 of the hole 24 is located only on the via wiring 32. The diameter D1 of the via wiring 32 on the upper surface 11 of the substrate 10 is, for example, about 30 μm to 60 μm. The diameter D2 of the hole 24 is, for example, 20 μm to 50 μm. The distance L between the contour 33 of the via wiring 32 and the contour 25 of the hole 24 is, for example, 3 μm to 10 μm.

[Production method]
6(a) to 7(c) are cross-sectional views showing a method for manufacturing an acoustic wave device according to the first embodiment. As shown in FIG. 6(a), a via hole is formed by irradiating the upper surface 11 of the substrate 10 with, for example, laser light, and a metal layer such as copper is formed in the via hole by, for example, electrolytic plating. Then, the metal layer is planarized by, for example, CMP (Chemical Mechanical Polishing) so that the upper surface 11 of the substrate 10 is exposed. As a result, a via wiring 32 is formed in the substrate 10. For example, when the via wiring 32 is a copper layer, a laminated film in which a titanium layer and a copper layer are laminated from the substrate 10 side is used as a seed layer for the electrolytic plating method. Here, the via wiring 32 does not penetrate the substrate 10 from the upper surface 11 to the lower surface 12.

As shown in FIG. 6(b), the piezoelectric substrate is bonded to the upper surface 11 of the substrate 10 at room temperature using, for example, a surface activation method. The substrate 10 and the piezoelectric substrate may be directly bonded via an amorphous layer of a few nm, or may be indirectly bonded via an insulating layer. The upper surface of the piezoelectric substrate is then polished using, for example, a CMP method to form a piezoelectric layer 20 of the desired thickness. An acoustic wave element 50 is formed on the piezoelectric layer 20. The acoustic wave element 50 is formed by a commonly known method. The reason that the via wiring 32 is formed only on the substrate 10 and not on the piezoelectric layer 20 is that cracks may occur in the piezoelectric layer 20 if via wiring 32 is formed that also penetrates the piezoelectric layer 20.

As shown in FIG. 6(c), a resist film (not shown) that covers the acoustic wave element 50 is formed on the piezoelectric layer 20, and then the piezoelectric layer 20 is etched using the resist film as a mask. The piezoelectric layer 20 is etched by dry etching, for example, but wet etching may also be used. As a result, a hole 24 located above the via wiring 32 is formed in the piezoelectric layer 20. In addition, the piezoelectric layer 20 is removed from the area where the frame 42 is to be formed.

As shown in FIG. 7(a), wiring 34 electrically connecting the acoustic wave element 50 and the via wiring 32 is formed on the piezoelectric layer 20 by, for example, deposition and lift-off. A metal layer 48 is formed in the area where the frame 42 is to be formed at the same time as the wiring 34. The wiring 34 is electrically connected to the via wiring 32 by contacting the via wiring 32 in a hole 24 provided in the piezoelectric layer 20. The wiring 34 and the metal layer 48 are, for example, a laminated film in which a titanium layer and a gold layer are laminated from the substrate 10 side.

As shown in FIG. 7(b), a current is supplied to the metal layer 48, and a metal layer (e.g., a copper layer, a nickel layer, and a gold layer from the substrate 10 side) is deposited on the metal layer 48 using electrolytic plating to form the frame 42. After solder 46 is formed on the frame 42, the lid 44 is bonded onto the frame 42 by the solder 46. The acoustic wave element 50 is sealed in the gap 22 formed between the piezoelectric layer 20 and the lid 44 by the sealing part 40 including the frame 42 and the lid 44.

As shown in FIG. 7(c), the lower surface 12 of the substrate 10 is polished or ground. As a result, the via wiring 32 is exposed on the lower surface 12 of the substrate 10. A terminal 30 is formed on the lower surface 12 of the substrate 10 so as to contact the via wiring 32. For example, a seed layer is formed on the lower surface 12 of the substrate 10. A resist film having an opening is formed on the seed layer. A current is supplied to the seed layer and a plating layer is formed in the opening using an electrolytic plating method. Then, the seed layer other than the plating layer is removed. The seed layer can be, for example, a laminated film in which a titanium layer and a gold layer are laminated from the substrate 10 side. The plating layer can be, for example, a copper layer, a nickel layer, and a gold layer from the substrate 10 side. In this manner, the acoustic wave device of Example 1 is formed.

[Comparative Example]
8A is a cross-sectional view of an acoustic wave device according to Comparative Example 1, FIG. 8B is a plan view showing the positional relationship between the via wiring and the piezoelectric layer in Comparative Example 1, and FIG. 8C is an enlarged view of region A in FIG. 8B. As shown in FIGS. 8A to 8C, in the acoustic wave device 500 according to Comparative Example 1, the via wiring 32 is not covered by the piezoelectric layer 20, and a cutout 26 is provided in the piezoelectric layer 20 so that the wiring 34 can contact the via wiring 32. The cutout 26 is provided on the periphery of the piezoelectric layer 20. The end 28 of the piezoelectric layer 20 at the cutout 26 is separated from the via wiring 32. The other configurations are the same as those in Example 1, so a description thereof will be omitted.

In Comparative Example 1, a notch 26 is provided in the piezoelectric layer 20. The notch 26 is provided in a size such that the end 28 of the piezoelectric layer 20 is located away from the via wiring 32. In such a case, the area of the upper surface of the piezoelectric layer 20 is reduced, and the area for forming the elastic wave element 50, etc. is reduced.

Figure 9(a) is a cross-sectional view of an acoustic wave device according to Comparative Example 2, Figure 9(b) is a plan view showing the positional relationship between the via wiring and the piezoelectric layer in Comparative Example 2, and Figure 9(c) is an enlarged view of region A in Figure 9(b). As shown in Figures 9(a) to 9(c), in the acoustic wave device 600 according to Comparative Example 2, a notch 26a is provided in the piezoelectric layer 20 such that the end 28 of the piezoelectric layer 20 at the notch 26a is located on the via wiring 32. Therefore, the notch 26a in Comparative Example 2 is smaller than the notch 26 in Comparative Example 1. The rest of the configuration is the same as in Example 1, so a description thereof will be omitted.

In Comparative Example 2, the notch 26a provided in the piezoelectric layer 20 is smaller than the notch 26 in Comparative Example 1. Therefore, compared to Comparative Example 1, the area of the upper surface of the piezoelectric layer 20 is larger, and a larger area can be secured for forming the elastic wave element 50, etc. However, Comparative Example 2 has the following problems.

Fig. 10(a) is a plan view showing the problem in Comparative Example 2, and Fig. 10(b) is a cross-sectional view taken along line A-A in Fig. 10(a). As shown in Fig. 10(a) and Fig. 10(b), in Comparative Example 2, the end 28 of the piezoelectric layer 20 in the cutout 26a is provided from the via wiring 32 to the substrate 10. The substrate 10 and the via wiring 32 are made of different materials, and therefore have different linear expansion coefficients. For example, when the substrate 10 is made of sapphire and the via wiring 32 is made of copper, the linear expansion coefficient of sapphire is about 7 x ^10-6 /°C, and the linear expansion coefficient of copper is about 17 x ^10-6 /°C.

Since the linear expansion coefficients of the substrate 10 and the via wiring 32 are different, the substrate 10 and the via wiring 32 expand to different degrees as shown by the arrows, for example, when the piezoelectric layer 20 is etched and/or when the acoustic wave device is mounted on a circuit board or the like, due to the rise in temperature. As a result, a crack 90 may occur at the location located at the boundary between the via wiring 32 and the substrate 10 at the end 28 of the piezoelectric layer 20 due to stress caused by the difference in the linear expansion coefficients of the substrate 10 and the via wiring 32.

On the other hand, according to Example 1, as shown in Figures 5(a) and 5(b), a hole 24 is provided in the piezoelectric layer 20 (insulating layer) that overlaps with the via wiring 32 in a plan view and has a contour 25 located inside the contour 33 of the via wiring 32 on the upper surface 11 of the substrate 10. As a result, the end of the piezoelectric layer 20 at the hole 24 is located only on the via wiring 32, so that even if the linear expansion coefficients of the substrate 10 and the via wiring 32 are different, it is possible to suppress the application of stress to the end of the piezoelectric layer 20 at the hole 24. Therefore, it is possible to suppress the occurrence of cracks. In addition, since the hole 24 is provided inside the via wiring 32, the area of the upper surface of the piezoelectric layer 20 is large, and a large area for forming the elastic wave element 50, etc. can be secured.

In addition, in Example 1, the substrate 10 is made of sapphire, and the via wiring 32 is made of copper. The linear expansion coefficient of sapphire is about 7×10 ⁻⁶ /° C., and the linear expansion coefficient of copper is about 17×10 ⁻⁶ /° C., so the difference in the linear expansion coefficient between the substrate 10 and the via wiring 32 is large. In this case, as in Comparative Example 2, if the end 28 of the piezoelectric layer 20 is provided from the via wiring 32 to the substrate 10, cracks are likely to occur due to the stress applied to the piezoelectric layer 20 caused by the difference in the linear expansion coefficient. Therefore, when the substrate 10 is made of sapphire and the via wiring 32 is made of copper, it is preferable to provide the hole 24 in the piezoelectric layer 20 as in Example 1.

The substrate 10 may be made of silicon instead of sapphire. The via wiring 32 may be made of gold or silver instead of copper. The linear expansion coefficient of silicon is about 4×10 ⁻⁶ /° C. The linear expansion coefficient of gold is about 14×10 ⁻⁶ /° C., and the linear expansion coefficient of silver is about 19×10 ⁻⁶ /° C. Even when the substrate 10 and the via wiring 32 are made of these materials, the difference in the linear expansion coefficient between the substrate 10 and the via wiring 32 becomes large. Therefore, it is preferable to provide the holes 24 in the piezoelectric layer 20. For example, from the viewpoint of suppressing the occurrence of cracks, the configuration in which the holes 24 are provided in the piezoelectric layer 20 is preferably when the difference in the linear expansion coefficient between the substrate 10 and the via wiring 32 is 7 or more, more preferably 9 or more, and even more preferably 12 or more. Moreover, if the piezoelectric layer 20 is thin, cracks are more likely to occur. Therefore, it is preferable to provide holes 24 when the piezoelectric layer 20 is 15 μm or less, it is more preferable to provide holes 24 when the piezoelectric layer 20 is 10 μm or less, and it is even more preferable to provide holes 24 when the piezoelectric layer 20 is 5 μm or less.

From the viewpoint of suppressing the occurrence of cracks in the piezoelectric layer 20, the distance L (see FIG. 5(a)) between the contour 33 of the via wiring 32 and the contour 25 of the hole 24 is preferably, for example, 3 μm or more, more preferably 4 μm or more, and even more preferably 5 μm or more. The diameter D2 (see FIG. 5(a)) of the hole 24 is preferably 0.9 times or less, more preferably 0.8 times or less, and even more preferably 0.7 times or less, of the diameter D1 (see FIG. 5(a)) of the via wiring 32 on the upper surface 11 of the substrate 10. On the other hand, from the viewpoint of the contact area between the wiring 34 and the via wiring 32, the distance L is, for example, preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. The diameter D2 of the hole 24 is preferably 0.4 times or more, more preferably 0.5 times or more, and even more preferably 0.6 times or more of the diameter D1 of the via wiring 32.

In addition, in the first embodiment, a frame 42 is provided on the upper surface 11 of the substrate 10 to surround the piezoelectric layer 20, and a lid 44 is provided on the frame 42, and a sealing portion 40 is provided to seal the elastic wave element 50 in the gap 22 between the piezoelectric layer 20 and the lid 44. In this case, in order to ensure the airtightness of the elastic wave element 50, the terminal 30 provided on the lower surface 12 of the substrate 10 is connected to the via wiring 32. In such a configuration, it is preferable to provide a hole 24 in the piezoelectric layer 20 in order to suppress the occurrence of cracks and ensure an area for forming the elastic wave element 50, etc.

In addition, in Example 1, the contour 25 of the hole 24 in the piezoelectric layer 20 is formed by a curve. This prevents stress from concentrating on a portion of the end of the piezoelectric layer 20 at the hole 24, and further prevents cracks from occurring. In Example 1, the contour 25 of the hole 24 is circular, but it may be other shapes such as elliptical, and is preferably outwardly convex.

11 is a cross-sectional view of an acoustic wave device according to a second embodiment. As shown in FIG. 11, an acoustic wave device 200 according to a second embodiment has an intermediate layer 80, which is an insulating layer, between a substrate 10 and a piezoelectric layer 20. The intermediate layer 80 may be a single layer, or may be a laminate of multiple layers. The intermediate layer 80 may include at least one layer selected from the group consisting of an aluminum oxide layer, a silicon oxide layer, a silicon nitride layer, an aluminum nitride layer, an aluminum oxynitride layer, a silicon layer, a titanium oxide layer, and a polysilicon layer. A hole 24 is provided penetrating the piezoelectric layer 20 and the intermediate layer 80. The other configurations are the same as those of the first embodiment, and therefore will not be described.

The acoustic wave device 200 according to the second embodiment is formed by depositing an intermediate layer 80 on a substrate 10 and then bonding a piezoelectric substrate to the intermediate layer 80, as shown in FIG. 6(b). The intermediate layer 80 is deposited by, for example, a CVD method or a sputtering method.

According to Example 2, an intermediate layer 80 is provided between the piezoelectric layer 20 and the substrate 10. In other words, the insulating layer provided on the substrate 10 includes the piezoelectric layer 20 and the intermediate layer 80 between the piezoelectric layer 20 and the substrate 10. In this case, as in Comparative Example 2, if the end of the intermediate layer 80 is provided from the via wiring 32 to the substrate 10, cracks are likely to occur in the intermediate layer 80. Therefore, it is preferable to provide holes 24 in the piezoelectric layer 20 and the intermediate layer 80.

From the viewpoint of suppressing the occurrence of cracks, it is preferable to provide holes 24 when the thickness of the insulating layer including the piezoelectric layer 20 and the intermediate layer 80 is 15 μm or less, it is more preferable to provide holes 24 when the thickness is 10 μm or less, and it is even more preferable to provide holes 24 when the thickness is 5 μm or less.

In the first and second embodiments, an elastic wave device having an elastic wave element 50 is shown as an example, but the present invention is not limited to this. An electronic component having an element other than the elastic wave element 50 (e.g., a passive element such as an inductor or a capacitor, an active element including a transistor, or a MEMS (Micro Electro Mechanical Systems) element, etc.) provided on an insulating layer may also be used.

Although the embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

10...substrate, 11...upper surface (first surface), 12...lower surface (second surface), 20...piezoelectric layer, 22...gap, 24...hole, 25...contour, 26, 26a...notch, 28...edge, 30...terminal, 32...via wiring, 33...contour, 34...wiring, 40...sealing portion, 42...frame, 44...lid, 46...solder, 48...metal layer, 50...acoustic wave element, 51...IDT, 52...reflector, 53...comb-shaped electrode, 54...electrode finger, 55...bus bar, 56...lower electrode, 57...piezoelectric layer, 58...upper electrode, 59...gap, 60...filter, 61...resonance region, 70...duplexer, 72...transmitting filter, 74...receiving filter, 80...intermediate layer, 90...crack, 100, 200, 500, 600...acoustic wave device

Claims (12)

a substrate having a first surface and a second surface opposite the first surface;
a via wiring penetrating the substrate from the first surface to the second surface;
an insulating layer provided on the first surface, the insulating layer overlapping the via wiring in a plan view and having a hole whose outline is located inside the outline of the via wiring on the first surface;
an acoustic wave element provided on the insulating layer and connected to the via wiring. The acoustic wave device of claim 1, wherein the substrate is made of silicon or sapphire. The acoustic wave device according to claim 1 or 2, wherein the via wiring is formed of copper, gold, or silver. the insulating layer includes a piezoelectric layer;
The acoustic wave device according to claim 1 , wherein the acoustic wave element includes a comb-shaped electrode provided on the piezoelectric layer. The acoustic wave device of claim 4, wherein the insulating layer includes an intermediate layer provided between the substrate and the piezoelectric layer. The acoustic wave device of claim 5, wherein the intermediate layer includes at least one of an aluminum oxide layer, a silicon oxide layer, a silicon nitride layer, an aluminum nitride layer, an aluminum oxynitride layer, a silicon layer, a titanium oxide layer, and a polysilicon layer. a sealing portion including a frame provided on the first surface to surround the insulating layer and a lid provided on the frame, the sealing portion sealing the acoustic wave element between the insulating layer and the lid;
The acoustic wave device according to claim 1 , further comprising: a terminal provided on the second surface and connected to the via wiring. The acoustic wave device according to claim 7, wherein the sealing portion seals the acoustic wave element in the gap between the insulating layer and the lid. The acoustic wave device according to claim 1 or 2, wherein the diameter of the hole is 0.9 times or less the diameter of the via wiring on the first surface. A filter comprising an acoustic wave device according to claim 1 or 2. A multiplexer comprising the filter according to claim 10. a substrate having a first surface and a second surface opposite the first surface;
a via wiring penetrating the substrate from the first surface to the second surface;
an insulating layer provided on the first surface, the insulating layer overlapping the via wiring in a plan view and having a hole whose outline is located inside the outline of the via wiring on the first surface;
An element provided on the insulating layer and connected to the via wiring;
and a sealing portion that seals the element in the gap on the insulating layer.

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