Acoustic wave device, filter, and multiplexer

Abstract

To provide an acoustic wave device capable of suppressing deterioration in device characteristics.SOLUTION: An acoustic wave device 100 includes: a support substrate 10; an insulating layer 13 provided on the support substrate 10; a via wiring 22 provided on the support substrate 10 and the insulating layer 13; a piezoelectric layer 14 provided on the insulating layer 13 and spaced apart from the via wiring 22; an acoustic wave element 15 provided on the piezoelectric layer 14; and a wiring 20 provided from above the via wiring 22 to above the piezoelectric layer 14, and connecting the via wiring 22 and the acoustic wave element 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to acoustic wave devices, filters, and multiplexers. [Background technology]

[0002] As an acoustic wave device used in communication devices such as smartphones, a configuration in which a piezoelectric layer is provided on a support substrate is known (for example, Patent Documents 1 to 3).A configuration in which via wiring is provided on the support substrate and the acoustic wave element on the piezoelectric layer is connected to the via wiring by wiring is also known (for example, Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-161899 [Patent Document 2] Japanese Patent Publication No. 2022-176790 [Patent Document 3] Japanese Patent Publication No. 2022-137818 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration described in Patent Document 3, the wiring connecting the via wiring and the acoustic wave element is long, which increases the wiring resistance and may degrade the device characteristics.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to suppress the deterioration of device characteristics. [Means for solving the problem]

[0006] The present invention is an elastic wave device comprising a support substrate, an insulating layer provided on the support substrate, via wiring provided on the support substrate and the insulating layer, a piezoelectric layer provided on the insulating layer and spaced apart from the via wiring, an elastic wave element provided on the piezoelectric layer, and wiring provided from above the via wiring to above the piezoelectric layer, connecting the via wiring and the elastic wave element.

[0007] In the above configuration, the insulating layer includes a first layer provided on the support substrate and being an aluminum oxide film, a silicon film, an aluminum nitride film, a silicon nitride film, or a silicon carbide film, and a second layer provided between the first layer and the piezoelectric layer and being a silicon oxide film or a silicon oxide film doped with fluorine, phosphorus, or boron, and the via wiring can be provided on the support substrate and the first layer, and the second layer has an opening above the via wiring and is provided at a distance from the via wiring.

[0008] In the above configuration, the surface of the via wiring on the opening side may be flush with the interface between the first layer and the second layer.

[0009] In the above configuration, the surface of the support substrate facing the insulating layer may be a rough surface, and the surface of the via wiring facing the piezoelectric layer may be positioned closer to the piezoelectric layer than the upper end of the rough surface.

[0010] In the above configuration, the insulating layer may be provided so as to fill in recesses in the rough surface.

[0011] In the above configuration, the via wiring may be mainly composed of copper, silver, or gold, and the piezoelectric layer may be a lithium tantalate layer or a lithium niobate layer.

[0012] In the above configuration, the piezoelectric layer may have a thickness of 10 μm or less.

[0013] In the above configuration, the shortest distance between the via wiring and the piezoelectric layer when viewed from above the piezoelectric layer may be 10 μm or more.

[0014] The present invention is a filter including the acoustic wave device described above.

[0015] The present invention is a multiplexer including the filter described above. [Effects of the Invention]

[0016] According to the present invention, it is possible to suppress the deterioration of device characteristics. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1A is a cross-sectional view of an acoustic wave device in accordance with a first embodiment, and FIG. 1B is a plan view of the acoustic wave element in accordance with the first embodiment. [Figure 2] 2(a) to 2(d) are cross-sectional views (part 1) illustrating a method for manufacturing the acoustic wave device in accordance with the first embodiment. [Figure 3] 3(a) to 3(c) are cross-sectional views (part 2) illustrating a method for manufacturing the acoustic wave device in accordance with the first embodiment. [Figure 4] 4A and 4B are cross-sectional views of acoustic wave devices according to first and second modifications of the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view of an acoustic wave device in accordance with a first comparative example. [Figure 6] FIG. 6(a) is a cross-sectional view of an acoustic wave device according to Comparative Example 2, and FIG. 6(b) is a diagram illustrating a problem in Comparative Example 2. [Figure 7] FIG. 7 is a cross-sectional view of an acoustic wave device in accordance with a second embodiment. [Figure 8] 8A to 8D are cross-sectional views illustrating a method for manufacturing an acoustic wave device in accordance with the second embodiment. [Figure 9] FIG. 9 is a cross-sectional view of an acoustic wave device in accordance with Comparative Example 3. As shown in FIG. [Figure 10]10(a) to 10(d) are cross-sectional views illustrating a method for manufacturing an acoustic wave device in accordance with Comparative Example 3. FIG. [Figure 11] FIG. 11(a) is a circuit diagram of a filter according to the third embodiment, and FIG. 11(b) is a circuit diagram of a duplexer according to a modified example of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Example]

[0019] 1A is a cross-sectional view of an acoustic wave device 100 according to Example 1, and FIG. 1B is a plan view of an acoustic wave element 15 in Example 1. The X and Y directions are perpendicular to each other in the planar direction of the support substrate 10. The stacking direction of the support substrate 10 and the piezoelectric layer 14 is the Z direction.

[0020] 1(a), a piezoelectric layer 14 is provided on a support substrate 10. An insulating layer 13 is provided between the support substrate 10 and the piezoelectric layer 14. The insulating layer 13 has a first layer 11 provided on the support substrate 10 and a second layer 12 provided on the first layer 11. An acoustic wave element 15 is provided on the piezoelectric layer 14. The acoustic wave element 15 is formed of a metal film 16.

[0021] As shown in FIG. 1(b), the acoustic wave element 15 is, for example, a surface acoustic wave resonator, and is an IDT (Interdigital Transistor) provided on the piezoelectric layer 14. The IDT 40 includes a pair of opposing comb electrodes 42. The comb electrodes 42 include a plurality of electrode fingers 43 and a bus bar 44 to which the plurality of electrode fingers 43 are connected. The region where the electrode fingers 43 of the pair of comb electrodes 42 intersect is an intersection region 45. The pair of comb electrodes 42 have the electrode fingers 43 alternately arranged in at least a portion of the intersection region 45. An acoustic wave excited primarily by the plurality of electrode fingers 43 in the intersection region 45 propagates primarily in the arrangement direction of the plurality of electrode fingers 43. The pitch of the electrode fingers 43 of one of the pair of comb electrodes 42 (the pitch between the centers of the electrode fingers 43) is approximately the wavelength λ of the acoustic wave. If the pitch of the plurality of electrode fingers 43 is D, the pitch of the electrode fingers 43 of one of the comb electrodes 42 is D, which is the pitch of two of the electrode fingers 43. The reflector 41 reflects the acoustic waves (surface acoustic waves) excited by the electrode fingers 43. This confines the acoustic waves within the intersection region 45 of the IDT 40. An insulating film may be provided to cover the electrode fingers 43. The insulating film may function as a protective film or a temperature compensation film. The comb electrode 42 may have dummy electrode fingers.

[0022] As shown in FIG. 1( a), a via wiring 22 is provided in the support substrate 10 and the insulating layer 13. The via wiring 22 penetrates the support substrate 10. The piezoelectric layer 14 and the second layer 12 have openings 17 above the via wiring 22, and the via wiring 22 penetrates the first layer 11 at the openings 17, exposing its surface from the insulating layer 13. The openings 17 in the second layer 12 can also be considered as recesses provided in the upper surface of the insulating layer 13. Therefore, the via wiring 22 can also be considered to penetrate the insulating layer 13 at the recesses provided in the insulating layer 13. The via wiring 22 is embedded in through holes 21 that penetrate the support substrate 10 and the first layer 11. When viewed from above the piezoelectric layer 14 (viewed from the +Z direction), the openings 17 are larger than the via wiring 22, so the piezoelectric layer 14 and the second layer 12 are separated from each other and do not come into contact with each other. The shortest distance L between the via wiring 22 and the piezoelectric layer 14 is 10 μm or more. The top surface of the first layer 11 is substantially flat, and the top surface 23 of the via wiring 22 is flush with the interface 19 between the first layer 11 and the second layer 12 .

[0023] A metal layer 18 is provided on the via wiring 22 to cover an upper surface 23 of the via wiring 22. A wiring 20 is provided from on the metal layer 18 to on the piezoelectric layer 14. The wiring 20 electrically connects the acoustic wave element 15 and the via wiring 22. A terminal 24 electrically connected to the via wiring 22 is provided on the lower surface of the support substrate 10.

[0024] The support substrate 10 is, for example, a sapphire substrate, alumina substrate, spinel substrate, quartz substrate, or silicon substrate having a thickness of 50 μm to 500 μm. The insulating layer 13 is, for example, a single-layer or composite inorganic insulating film such as a silicon oxide film, a silicon nitride film, or an aluminum oxide film. The first layer 11 is, for example, a polycrystalline or amorphous insulating film having a thickness of 2 μm to 8 μm, such as an aluminum oxide film, a silicon film, an aluminum nitride film, a silicon nitride film, or a silicon carbide film. The acoustic velocity of the bulk wave propagating through the first layer 11 is faster than the acoustic velocity of the bulk wave propagating through the second layer 12 and the piezoelectric layer 14.

[0025] The second layer 12 is, for example, a temperature compensation film, an insulating film having a temperature coefficient of elastic constant with an opposite sign to that of the piezoelectric layer 14. For example, the temperature coefficient of the elastic constant of the piezoelectric layer 14 is negative, while the temperature coefficient of the elastic constant of the second layer 12 is positive. The second layer 12 is, for example, a polycrystalline or amorphous silicon oxide film with a thickness of 0.1 μm to 1 μm, either undoped or containing an additive element such as fluorine, phosphorus, or boron. The piezoelectric layer 14 is, for example, a single-crystal lithium tantalate layer or a single-crystal lithium niobate layer with a thickness of 0.1 μm to 10 μm. The piezoelectric layer 14 is, for example, a rotated Y-cut X-propagation lithium tantalate layer or a rotated Y-cut X-propagation lithium niobate layer, for example, a 42° rotated Y-cut X-propagation lithium tantalate layer or a 128° rotated Y-cut X-propagation lithium niobate layer.

[0026] The via wiring 22 is a metal film mainly composed of copper, silver, or gold. Being mainly composed of a certain element means that the certain element is contained at 50 atomic % or more (or, for example, 80 atomic % or more). The diameter of the upper surface 23 of the via wiring 22 is, for example, 40 μm to 50 μm. The metal layer 18 is, for example, a titanium layer with a thickness of 0.1 μm to 1 μm. The metal layer 18 is a barrier layer for preventing interdiffusion between the wiring 20 and the via wiring 22. The wiring 20 includes an adhesion layer and a low-resistance layer provided on the adhesion layer. The adhesion layer is, for example, a titanium layer with a thickness of 0.2 μm. The low-resistance layer is, for example, a gold layer with a thickness of 1 μm. The terminal 24 includes, for example, a copper film with a thickness of 2 μm, a nickel film with a thickness of 5 μm, and a gold film with a thickness of 0.3 μm from the support substrate 10 side. The metal film 16 is, for example, an aluminum film, an aluminum alloy film, or a molybdenum film.

[0027] [Manufacturing method] 2(a) to 3(c) are cross-sectional views illustrating a manufacturing method of the acoustic wave device 100 in accordance with Example 1. As shown in Fig. 2(a), a recess 25 is formed in the upper surface of the support substrate 10. The recess 25 is formed by, for example, irradiating with laser light.

[0028] As shown in FIG. 2(b), a layer is formed on the support substrate 10 by, for example, sputtering or CVD (Chemical Vapor Deposition). The first layer 11 is formed by vapor deposition. The first layer 11 is also formed on the side and bottom surfaces of the recesses 25, but is formed without filling the recesses 25. As a result, through holes 21 are formed in the support substrate 10 and the first layer 11. At this point, the through holes 21 do not penetrate the support substrate 10.

[0029] 2(c), via wiring 22 is formed by, for example, electrolytic plating so as to fill the through hole 21. A metal film of the via wiring 22 is also formed on the first layer 11.

[0030] As shown in FIG. 2(d), the metal film on the first layer 11 is removed by, for example, chemical mechanical polishing (CMP). Remove it using the Mechanical Polishing method.

[0031] As shown in FIG. 3(a), the second layer 12 is formed on the first layer 11 using, for example, sputtering or CVD. This forms an insulating layer 13 including the first layer 11 and the second layer 12. A piezoelectric substrate is bonded to the second layer 12. The piezoelectric substrate may be bonded to the second layer 12 with a bonding layer sandwiched therebetween. For example, a surface activation method is used to bond the piezoelectric substrate. The top surface of the piezoelectric substrate is polished using, for example, CMP to form a piezoelectric layer 14 of the desired thickness.

[0032] As shown in FIG. 3B, an acoustic wave element 15 is formed on the piezoelectric layer 14. The acoustic wave element 15 is formed using, for example, a vacuum deposition method and a lift-off method, or a sputtering method and an etching method. Then, the piezoelectric layer 14 and the second layer 12 are removed to expose the via wiring 22. This forms an opening 17 in the piezoelectric layer 14 and the second layer 12, exposing the via wiring 22. The piezoelectric layer 14 and the second layer 12 are removed using, for example, a dry etching method or a wet etching method. For example, if the piezoelectric layer 14 is primarily composed of lithium tantalate or lithium niobate and the second layer 12 is primarily composed of silicon oxide, the piezoelectric layer 14 and the second layer 12 may be dry-etched using a fluorine-based gas (e.g., SF6 or CF4). The via wiring 22 penetrates the first layer 11 at the opening 17, and an upper surface 23 is exposed from the first layer 11 to the opening 17. When viewed from above the piezoelectric layer 14, the opening 17 is made larger than the via wiring 22, so that the piezoelectric layer 14 and the second layer 12 are formed apart from the via wiring 22 and do not come into contact with each other.

[0033] As shown in FIG. 3(c), a metal layer 18 is formed on the via wiring 22 to cover the upper surface 23. The metal layer 18 is formed using, for example, a vacuum deposition method and a lift-off method, or a sputtering method and an etching method. A wiring 20 is formed from the metal layer 18 onto the piezoelectric layer 14, via the side surfaces of the second layer 12 and the piezoelectric layer 14. The wiring 20 is formed using, for example, an electrolytic plating method. As a result, the acoustic wave element 15 and the via wiring 22 are electrically connected by the wiring 20. Thereafter, as shown in FIG. 1(a), the lower surface of the support substrate 10 is polished or ground to expose the via wiring 22. A terminal 24 connected to the via wiring 22 is formed on the lower surface of the support substrate 10. In this manner, the acoustic wave device 100 is manufactured.

[0034] [Variations] FIG. 4(a) is a cross-sectional view of an acoustic wave device 110 according to a first modification of the first embodiment. As shown in FIG. 4(a), in the first modification of the first embodiment, the second layer 12 is divided into a lower layer 12a and an upper layer 12b. A bonding layer 29 is provided between the lower layer 12a and the upper layer 12b. The bonding layer 29 is, for example, a titanium layer. The other configurations are the same as those of the first embodiment, and therefore, description thereof will be omitted. In this way, the bonding layer 29 may be provided between the second layers 12.

[0035] FIG. 4(b) is a cross-sectional view of an acoustic wave device 120 according to Modification 2 of Example 1. As shown in FIG. 4(b), in Modification 2 of Example 1, the second layer 12 is divided into a lower layer 12a and an upper layer 12b, a bonding layer 29 is provided between them, and the via wiring 22a has a rectangular shape in cross section. The other configurations are the same as those of Example 1, and therefore description thereof will be omitted. As described above, in Example 1 and Modification 1, the via wiring 22 has a tapered shape in which the width decreases from the upper surface side of the insulating layer 13 toward the lower surface side of the support substrate 10. However, this is not limited to this case, and the via wiring 22 may have a rectangular shape with a substantially constant width, as in the via wiring 22a of Modification 2 of Example 1.

[0036] [Comparative Example 1] 5 is a cross-sectional view of an acoustic wave device 500 in accordance with Comparative Example 1. As shown in FIG. 5, in Comparative Example 1, via wiring 22 penetrates only the support substrate 10. The piezoelectric layer 14, the second layer 12, and the first layer 11 have openings 17a above the via wiring 22. The other configurations are the same as those in Example 1, and therefore will not be described further.

[0037] In Comparative Example 1, via wiring 22 is provided only in support substrate 10, and therefore wiring 20 connecting via wiring 22 and acoustic wave element 15 is long. This increases the electrical resistance of wiring 20, which may degrade device characteristics.

[0038] Comparative Example 2 6(a) is a cross-sectional view of an acoustic wave device 510 according to Comparative Example 2, and FIG. 6(b) is a diagram illustrating a problem in Comparative Example 2. As shown in FIG. 6(a), in Comparative Example 2, via wiring 22 penetrates through the support substrate 10, the first layer 11, the second layer 12, and the piezoelectric layer 14. Therefore, the piezoelectric layer 14 and the second layer 12 are in contact with the via wiring 22. The other configurations are the same as those in Example 1, and therefore will not be described again.

[0039] The numerical values ​​listed for each layer in FIG. 6(b) are examples of linear expansion coefficients. Here, the linear expansion coefficients are shown for a case where the first layer 11 is an aluminum oxide layer, the second layer 12 is a silicon oxide layer, the piezoelectric layer 14 is a lithium tantalate layer, the via wiring 22 is a copper layer, the metal layer 18 is a titanium layer, and the wiring 20 is a gold layer. As shown in FIG. 6(b), when the first layer 11 is an aluminum oxide layer, the linear expansion coefficient of aluminum oxide is 7.2 ppm / °C. When the second layer 12 is a silicon oxide layer, the linear expansion coefficient of silicon oxide is 2.3 ppm / °C. When the piezoelectric layer 14 is a lithium tantalate layer, the linear expansion coefficient of lithium tantalate varies depending on the crystal orientation. For example, the linear expansion coefficient in the direction perpendicular to the X-axis direction for 42° rotated Y-cut X-propagation lithium tantalate is 9.5 ppm / °C. When the via wiring 22 is a copper layer, the linear expansion coefficient of copper is 17.7 ppm / °C. When the metal layer 18 is a titanium layer, the linear expansion coefficient of titanium is 8.4 ppm / °C. When the wiring 20 is a gold layer, the linear expansion coefficient of gold is 14.2 ppm / °C.

[0040] As described above, there is a large difference in the linear expansion coefficient between the piezoelectric layer 14 and the via wiring 22. Therefore, when the piezoelectric layer 14 and the via wiring 22 are in contact with each other, the piezoelectric layer 14 is subjected to stress from the via wiring 22 due to temperature rises during device manufacturing and / or use. In this case, cracks or the like may occur in the piezoelectric layer 14 and / or between the piezoelectric layer 14 and the second layer 12, which may deteriorate the device characteristics.

[0041] On the other hand, according to Example 1 and its modified examples, the via wirings 22, 22a are provided in the support substrate 10 and the insulating layer 13. This prevents the wiring 20 provided from over the via wirings 22, 22a to over the piezoelectric layer 14 from becoming too long. In addition, the piezoelectric layer 14 is provided away from the via wirings 22, 22a. This prevents the piezoelectric layer 14 from receiving stress from the via wirings 22, 22a even if the temperature rises during device manufacturing and use. This prevents deterioration of the device characteristics.

[0042] In Example 1 and its modified examples, the insulating layer 13 includes a first layer 11 and a second layer 12. The first layer 11 is provided on the support substrate 10 and is an aluminum oxide film, a silicon film, an aluminum nitride film, a silicon nitride film, or a silicon carbide film. The second layer 12 is provided between the first layer 11 and the piezoelectric layer 14 and is a silicon oxide film or a silicon oxide film doped with fluorine, phosphorus, or boron. Via wirings 22, 22a are provided on the support substrate 10 and the first layer 11. The second layer 12 has an opening 17 above the via wiring 22 and is spaced apart from the via wiring 22. Since the second layer 12 is a film made of the above material, it has a temperature coefficient of the elastic constant with a sign opposite to that of the temperature coefficient of the elastic constant of the piezoelectric layer 14, thereby reducing the temperature coefficient of frequency of the acoustic wave device. When the first layer 11 is a film of the above material, the acoustic velocity of the bulk waves propagating through the first layer 11 is faster than the acoustic velocity of the bulk waves propagating through the second layer 12 and the piezoelectric layer 14. This allows the energy of the main response elastic wave to be confined within the piezoelectric layer 14 and the second layer 12, thereby suppressing a decrease in loss. Because the second layer 12 is separated from the via wiring 22, the second layer 12 is less likely to receive stress from the via wiring 22, even if the temperature rises during device manufacturing and use. This prevents deterioration of device characteristics.

[0043] To confine the acoustic waves within the piezoelectric layer 14 and the second layer 12, the thickness of the first layer 11 is preferably 0.3λ or greater, more preferably 1.0λ or greater. To improve characteristics, the thickness of the first layer 11 is preferably 10λ or less. To ensure the temperature compensation function of the second layer 12, the thickness of the second layer 12 is preferably 0.1λ or greater, more preferably 0.2λ or greater. For the second layer 12 to function as a temperature compensation layer, a certain amount of energy from the main response acoustic wave must be present within the second layer 12. Although the range in which the energy of the surface acoustic wave is concentrated depends on the type of surface acoustic wave, the energy of the surface acoustic wave is typically concentrated within a range of 2.0λ from the top surface of the piezoelectric layer 14, and particularly within a range of 1.0λ from the top surface of the piezoelectric layer 14. Therefore, the distance from the bottom surface of the second layer 12 to the top surface of the piezoelectric layer 14 is preferably 2.0λ or less, more preferably 1.0λ or less.

[0044] In addition, in the first embodiment and its modified example, the upper surfaces 23 of the via wirings 22, 22a are flush with the interface between the first layer 11 and the second layer 12. This makes it possible to prevent the wiring 20 from becoming long.

[0045] In Example 1 and its modifications, the via wiring 22 is a metal layer primarily composed of copper, silver, or gold. The piezoelectric layer 14 is a lithium tantalate layer or a lithium niobate layer. In this case, since the difference in linear expansion coefficient between the via wiring 22 and the piezoelectric layer 14 is large, it is preferable to provide the piezoelectric layer 14 away from the via wiring 22. The linear expansion coefficient of 42° rotated Y-cut X-propagation lithium tantalate is 16.1 ppm / °C in the direction of elastic wave propagation and 9.5 ppm / °C in the direction perpendicular to the direction of elastic wave propagation. The linear expansion coefficient of 128° rotated Y-cut X-propagation lithium niobate is 15.4 ppm / °C in the direction of elastic wave propagation and 12.4 ppm / °C in the direction perpendicular to the direction of elastic wave propagation. The linear expansion coefficient of copper is 17.7 ppm / °C, the linear expansion coefficient of silver is 19.7 ppm / °C, and the linear expansion coefficient of gold is 14.2 ppm / °C.

[0046] In Example 1 and its modified examples, the thickness of the piezoelectric layer 14 is 10 μm or less. By making the thickness of the piezoelectric layer 14 10 μm or less, the characteristics can be improved, but cracks and the like are more likely to occur when the piezoelectric layer 14 receives stress from the via wiring 22. Therefore, in this case, it is preferable to provide the piezoelectric layer 14 away from the via wiring 22.

[0047] Furthermore, in Example 1 and its modified examples, the shortest distance L between the via wiring 22 and the piezoelectric layer 14 when viewed from above the piezoelectric layer 14 (see FIG. 1(a)) is 10 μm or more. This makes it difficult for the piezoelectric layer 14 to receive stress from the via wiring 22 even if the temperature rises during device manufacturing and use. From the viewpoint of suppressing stress on the piezoelectric layer 14, the shortest distance L is preferably 15 μm or more, and more preferably 20 μm or more. From the viewpoint of suppressing an increase in the size of the device, the shortest distance L is preferably 30 μm or less, and more preferably 25 μm or less. [Example]

[0048] FIG. 7 is a cross-sectional view of an acoustic wave device 200 according to a second embodiment. As shown in FIG. 7 , in the second embodiment, the upper surface 26 of the support substrate 10 is a rough surface having irregularities. The arithmetic mean roughness Ra of the upper surface 26 is 100 nm or more. The rough upper surface 26 roughens the interface between the support substrate 10 and the insulating layer 13. As a result, unwanted waves (bulk waves) generated when the acoustic wave element 15 excites a surface acoustic wave in the main mode are scattered at the interface between the support substrate 10 and the insulating layer 13, thereby suppressing spurious signals. The irregularities on the rough surface may be arranged regularly or irregularly. The first layer 11 has a recess 27 below the opening 17 provided in the piezoelectric layer 14 and the second layer 12. The via wiring 22 penetrates the first layer 11 at the recess 27. The opening 17 in the second layer 12 and the recess 27 in the first layer 11 can be collectively referred to as a recess provided on the upper surface of the insulating layer 13. In this case, it can be said that the via wiring 22 penetrates the insulating layer 13 at a recess provided in the insulating layer 13. The via wiring 22 is embedded in a through hole 21 that penetrates the support substrate 10 and the first layer 11. The upper surface 23 of the via wiring 22 is located closer to the piezoelectric layer 14 than the upper end of the rough surface on the upper surface 26 of the support substrate 10, and is located closer to the support substrate 10 than the interface 19 between the first layer 11 and the second layer 12. The recess in the rough surface on the upper surface 26 of the support substrate 10 is embedded with the first layer 11. The other configurations are the same as those of Example 1, so a description thereof will be omitted.

[0049] [Manufacturing method] 8(a) to 8(d) are cross-sectional views illustrating a manufacturing method of an acoustic wave device 200 in accordance with the second embodiment. As shown in FIG. 8(a), after forming a recess on the upper surface 26 of the support substrate 10 by, for example, irradiating it with laser light, a lower portion 11a of the first layer 11 is formed on the support substrate 10 by, for example, sputtering or CVD. This forms a through hole 21 in the support substrate 10 and a portion of the first layer 11. The lower portion 11a of the first layer 11 is embedded in the recess in the rough surface of the upper surface 26 of the support substrate 10. At this point, the through hole 21 does not penetrate the support substrate 10.

[0050] 8(b), the via wiring 22 is formed by, for example, electrolytic plating so as to fill the through hole 21. The metal film of the via wiring 22 is also formed on the lower portion 11a of the first layer 11.

[0051] 8(c), the metal film on the lower portion 11a of the first layer 11 is removed by, for example, CMP. Then, the upper portion 11b of the first layer 11 is formed on the lower portion 11a by, for example, sputtering or CVD. In this way, the first layer 11 is formed.

[0052] As shown in FIG. 8(d), the second layer 12 is formed on the first layer 11 by, for example, sputtering or CVD, and then the piezoelectric layer 14 is formed on the second layer 12 by, for example, surface activation. An acoustic wave element 15 is formed on the piezoelectric layer 14. The acoustic wave element 15 is formed by, for example, vacuum deposition and lift-off, or sputtering and etching. The piezoelectric layer 14, the second layer 12, and the upper portion 11b of the first layer 11 are then removed to expose the via wiring 22. The piezoelectric layer 14, the second layer 12, and the upper portion 11b of the first layer 11 are removed by, for example, dry etching or wet etching. This forms an opening 17 in the piezoelectric layer 14 and the second layer 12, and a recess 27 in the first layer 11. Then, the same processes as those described in Example 1 from FIG. 3(c) onward are performed. This completes the manufacturing of the acoustic wave device 200.

[0053] Comparative Example 3 9 is a cross-sectional view of an acoustic wave device 520 in accordance with Comparative Example 3. As shown in FIG. 9, in Comparative Example 3, via wiring 22 penetrates only the support substrate 10. The piezoelectric layer 14, the second layer 12, and the first layer 11 have openings 17a above the via wiring 22. A metal film 28 that forms the via wiring 22 is formed in at least a portion of a recess in the rough surface of the upper surface 26 of the support substrate 10. The other configurations are the same as those in Example 2, and therefore will not be described again.

[0054] [Manufacturing method] 10(a) to 10(d) are cross-sectional views showing a manufacturing method of an acoustic wave device 520 in accordance with Comparative Example 3. As shown in Fig. 10(a), a recess is formed on the upper surface 26 of the support substrate 10 by, for example, irradiating it with laser light, and then the via wiring 22 is formed by, for example, electrolytic plating so as to fill the recess. A metal film of the via wiring 22 is also formed on the upper surface 26 of the support substrate 10.

[0055] 10(b), the metal film on the upper surface 26 of the support substrate 10 is removed by, for example, CMP. At this time, since the upper surface 26 of the support substrate 10 is roughened to suppress spurious emissions, the metal film on the upper surface 26 is removed while maintaining the roughened state of the upper surface 26. For this reason, it is difficult to remove all of the metal film on the upper surface 26, and the metal film 28 of the via wiring 22 remains in at least some of the recesses in the roughened surface of the upper surface 26.

[0056] 10(c), a first layer 11 and a second layer 12 are formed on a support substrate 10 by, for example, sputtering or CVD, thereby forming an insulating layer 13. Thereafter, a piezoelectric layer 14 is formed on the second layer 12 by, for example, surface activation.

[0057] As shown in FIG. 10(d), an acoustic wave element 15 is formed on the piezoelectric layer 14. The acoustic wave element 15 is formed using, for example, a vacuum deposition method and a lift-off method, or a sputtering method and an etching method. Then, the piezoelectric layer 14, the second layer 12, and the first layer 11 are removed so as to expose the via wiring 22. For example, a dry etching method or a wet etching method is used to remove the piezoelectric layer 14, the second layer 12, and the first layer 11. As a result, an opening 17a is formed in the piezoelectric layer 14, the second layer 12, and the first layer 11, exposing the via wiring 22. Then, the same steps as those described in FIG. 3(c) and subsequent figures of the first embodiment are performed. This completes the manufacture of an acoustic wave device 520.

[0058] In Comparative Example 3, as shown in Fig. 9, the upper surface 26 of the support substrate 10 is rough. The via wiring 22 is provided only on the support substrate 10. In this case, since the device is manufactured using the steps shown in Figs. 10(a) to 10(d), the metal film 28 of the via wiring 22 remains in at least a part of the recess in the rough surface of the upper surface 26 of the support substrate 10. In this case, the metal film 28 increases parasitic capacitance, which may deteriorate the device characteristics (for example, deterioration of pass characteristics).

[0059] 7, the upper surface 23 of the via wiring 22 is located closer to the piezoelectric layer 14 than the upper end of the rough surface of the upper surface 26 of the support substrate 10. In this case, since the manufacturing process is performed using the steps shown in FIGS. 8(a) to 8(d), the formation of a metal film in the recesses of the rough surface of the upper surface 26 of the support substrate 10 is suppressed. This makes it possible to suppress deterioration of the device characteristics.

[0060] In addition, in Example 2, the insulating layer 13 is provided so as to fill in the recesses in the rough surface of the upper surface 26 of the support substrate 10. This makes it possible to suppress an increase in parasitic capacitance and to suppress deterioration of device characteristics.

[0061] In Example 1 and its modifications, and Example 2, the case where the openings 17 located above the via wirings 22, 22a are provided in the second layer 12 of the insulating layer 13 has been described as an example, but the present invention is not limited to this. The via wirings 22, 22a may penetrate both the first layer 11 and the second layer 12 of the insulating layer 13. [Example]

[0062] FIG. 11(a) is a circuit diagram of a filter 300 according to a third embodiment. As shown in FIG. 11(a), one or more series resonators S1 to S4 are connected in series between an input terminal Tin and an output terminal Tout. One or more parallel resonators P1 to P3 are connected in parallel between the input terminal Tin and the output terminal Tout. The acoustic wave device according to the first embodiment, its modifications, and the second embodiment can be used for at least one of the one or more series resonators S1 to S4 and the one or more parallel resonators P1 to P3. The number of resonators in the ladder filter can be set as appropriate. The filter may be a multimode filter.

[0063] FIG. 11(b) is a circuit diagram of a duplexer 310 according to a modified example of the third embodiment. As shown in FIG. 11(b), a transmit filter 50 is connected between a common terminal Ant and a transmit terminal Tx. A receive filter 52 is connected between the common terminal Ant and a receive terminal Rx. The transmit filter 50 passes, to the common terminal Ant, signals in the transmit band among the high-frequency signals input from the transmit terminal Tx as transmit signals, and suppresses signals of other frequencies. The receive filter 52 passes, to the receive terminal Rx, signals in the receive band among the high-frequency signals input from the common terminal Ant as receive signals, and suppresses signals of other frequencies. At least one of the transmit filter 50 and the receive filter 52 can be the filter of the third embodiment. Although a duplexer has been described as an example of a multiplexer, a triplexer or a quadplexer may also be used.

[0064] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0065] 10...support substrate, 11...first layer, 11a...lower portion, 11b...upper portion, 12...second layer, 12a...lower layer, 12b...upper layer, 13...insulating layer, 14...piezoelectric layer, 15...acoustic wave element, 16...metal film, 17, 17a...opening, 18...metal layer, 19...interface, 20...wiring, 21...through hole, 22, 22a...via wiring, 24...terminal, 25...recess, 26...upper surface, 27...recess, 28...metal film, 29...bonding layer, 40...IDT, 41...reflector, 42...comb-shaped electrode, 43...electrode finger, 44...bus bar, 45...intersection region, 100, 110, 120, 200...acoustic wave device, 300...filter, 310...duplexer, 500, 510, 520...acoustic wave device

Claims

1. A support substrate; an insulating layer provided on the support substrate; via wiring provided in the support substrate and the insulating layer; a piezoelectric layer provided on the insulating layer and spaced apart from the via wiring; an acoustic wave element provided on the piezoelectric layer; an interconnection that is provided from above the via interconnection to above the piezoelectric layer and connects the via interconnection to the acoustic wave element;

2. the insulating layer includes: a first layer provided on the support substrate and being an aluminum oxide film, a silicon film, an aluminum nitride film, a silicon nitride film, or a silicon carbide film; and a second layer provided between the first layer and the piezoelectric layer and being a silicon oxide film or a silicon oxide film doped with fluorine, phosphorus, or boron; the via wiring is provided in the support substrate and the first layer, The acoustic wave device according to claim 1 , wherein the second layer has an opening above the via wiring and is spaced apart from the via wiring.

3. The acoustic wave device according to claim 2 , wherein a surface of the via wiring on the opening side is flush with an interface between the first layer and the second layer.

4. the surface of the support substrate facing the insulating layer is a rough surface; The acoustic wave device according to claim 1 , wherein a surface of the via wiring facing the piezoelectric layer is located closer to the piezoelectric layer than an upper end of the rough surface.

5. The acoustic wave device according to claim 4 , wherein the insulating layer is provided by filling recesses in the rough surface.

6. the via wiring is mainly composed of copper, silver, or gold, The acoustic wave device according to claim 1 , wherein the piezoelectric layer is a lithium tantalate layer or a lithium niobate layer.

7. The acoustic wave device according to claim 1 , wherein the piezoelectric layer has a thickness of 10 μm or less.

8. The acoustic wave device according to claim 1 , wherein the shortest distance between the via wiring and the piezoelectric layer when viewed from above the piezoelectric layer is 10 μm or more.

9. A filter comprising the acoustic wave device according to claim 1 or 2.

10. A multiplexer including the filter of claim 9.

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