JP2023141885A - Elastic wave device, filter, multiplexer, and method for manufacturing elastic wave device - Google Patents

Abstract

To provide an elastic wave device in which an increase in electrical resistance can be suppressed.SOLUTION: An elastic wave device 100 includes: a substrate 10 that has an upper face 30 and a lower face 32, the upper face 30 having a first region 40, a second region 42 located closer to the lower face 32 than the first region 40 and a step 44 having a side face 46 between the first region 40 and the second region 42, the step being tilted obliquely; an elastic wave element 18 provided in the first region 40; a metal layer 50 having a first portion 52 provided in the second region 42 and a second portion 54 continuing from the first portion 52, and provided to be raised higher than the first portion 52 along the side face 46 of the step 44, the tip 56 of the second portion being located on the side face 46 of the step 44; and a metal layer 60 provided, from the second region 42 to the first region 40, to overlap the first portion 52 and the second portion 54 of the metal layer 50 and electrically connected to the elastic wave element 18.SELECTED DRAWING: Figure 1

Description

The present invention relates to an acoustic wave device, a filter, a multiplexer, and a method for manufacturing an acoustic wave device.

It is known to use a substrate in which a piezoelectric substrate is bonded to a support substrate, and to form wiring extending from the support substrate onto the piezoelectric substrate via the inclined side surface of the piezoelectric substrate (for example, Patent Document 1). Furthermore, when wiring is formed, protrusions called burrs may be formed at the ends of the wiring. Therefore, a manufacturing method for suppressing the occurrence of burrs has been proposed (for example, Patent Document 2).

International Publication No. 2015/098678 Japanese Patent Application Publication No. 2005-166972

When a first region in which an acoustic wave element is formed and a second region located closer to the bottom surface of the substrate than the first region are formed on the upper surface of the substrate, the first region and the first region are connected from the second region to the lower surface of the substrate. A metal layer may be provided in the first region via the side surface of the step between the two regions. In this case, the metal layer may become thinner on the side surface of the step between the first region and the second region, resulting in higher electrical resistance.

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

The present invention has a first surface and a second surface opposite to the first surface, and the first surface is located closer to the second surface than the first region. a substrate having a second region; a step having an oblique side surface between the first region and the second region; an acoustic wave element provided in the first region; a first portion that is continuous from the first portion, is provided along the side surface of the step and is raised from the first portion, and has a tip located on the side surface of the step. a first metal layer having a second portion, a first metal layer overlapping the first portion and the second portion of the first metal layer and extending from the second region to the first region; and a second metal layer electrically connected to the element.

In the above configuration, the substrate includes a support substrate and a piezoelectric substrate bonded to the support substrate, the first region is an upper surface of the piezoelectric substrate, and the step is provided to penetrate the piezoelectric substrate. , the side surface of the step may include a side surface of the piezoelectric substrate.

In the above structure, the second metal layer may entirely overlap the second portion of the first metal layer on the side surface of the step when viewed in plan.

In the above configuration, in a cross-sectional view, the thickness of the first metal layer in the direction perpendicular to the side surface of the step at the first location located on the tip side of the second portion of the first metal layer is The thickness of the step in the vertical direction at a second location located below the step than the first location of the second portion may be less than or equal to the thickness of the step.

In the above configuration, the first portion of the first metal layer is provided in the substrate so as to penetrate from the first surface to the second surface, overlaps the first portion of the first metal layer in plan view, and The configuration may include a via wiring that contacts the portion.

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

The invention is a multiplexer including the filter described above.

The present invention has a first surface and a second surface opposite to the first surface, and the first surface includes a first region in which an acoustic wave element is formed, and a second surface that extends from the first region to the second surface. the second region on the first surface of the substrate, the substrate having a second region located near the second surface, and a step having an oblique side surface between the first region and the second region; a step of forming a mask layer having an opening exposing the step, the side surface of the opening being located on the side surface of the step; forming a first metal layer using the mask layer as a mask; After forming the metal layer, removing the mask layer, and after removing the mask layer, forming a first portion of the first metal layer provided in the second region and along a side surface of the step. a second portion of the first metal layer that is provided to be raised from the first portion, extends from the second region to the first region, and is electrically connected to the acoustic wave element; A method of manufacturing an acoustic wave device includes a step of forming a metal layer.

In the above structure, the step of removing the mask layer is performed so that the burrs formed on the first metal layer due to the film formation of the first metal layer fall down along the sides of the step after the mask layer is removed. The mask layer may be removed immediately.

In the above configuration, the step of forming the first metal layer includes forming the first metal layer from the second region exposed in the opening to the side surface of the opening using a sputtering method or a vapor deposition method, and In the step of removing the mask layer, the mask layer may be removed using a liquid so that the burrs fall down after the mask layer is removed.

In the above configuration, the step of removing the mask layer may include a step of drying the liquid so that the burr collapses after the mask layer is removed.

According to the present invention, it is possible to suppress an increase in electrical resistance.

FIG. 1(a) is a cross-sectional view of the acoustic wave device according to Example 1, and FIG. 1(b) is a plan view in the vicinity of FIG. 1(a). FIG. 2(a) is a plan view of the acoustic wave device according to Example 1, and FIG. 2(b) is an enlarged cross-sectional view of the vicinity of the step in FIG. 1(a). FIG. 3 is a plan view of the acoustic wave element in Example 1. FIGS. 4(a) to 4(c) are cross-sectional views (part 1) showing the method for manufacturing the acoustic wave device according to the first embodiment. FIGS. 5(a) to 5(c) are cross-sectional views (part 2) showing the method for manufacturing the acoustic wave device according to the first embodiment. FIGS. 6(a) to 6(c) are cross-sectional views (part 3) showing the method for manufacturing the acoustic wave device according to the first embodiment. 7(a) is a cross-sectional view of an acoustic wave device according to comparative example 1, and FIG. 7(b) is an enlarged cross-sectional view of the vicinity of the step in FIG. 7(a). FIG. 8(a) is a cross-sectional view of an acoustic wave device according to Comparative Example 2, and FIG. 8(b) is an enlarged cross-sectional view of the vicinity of the step in FIG. 8(a). 9(a) is a cross-sectional view of an acoustic wave device according to comparative example 3, and FIG. 9(b) is an enlarged cross-sectional view of the vicinity of the step in FIG. 9(a). 10(a) to 10(e) are cross-sectional views showing the process of forming burrs in Comparative Example 3. FIG. 11(a) to 11(e) are cross-sectional views showing the process of forming burrs in Example 1. FIG. FIG. 12 is a cross-sectional view showing an example of another shape of the second portion of the metal layer. 13(a) is a sectional view of an acoustic wave device according to Example 2, and FIG. 13(b) is a sectional view of an acoustic wave element in Example 2. FIG. 14 is a circuit diagram of a filter according to the third embodiment. FIG. 15 is a block diagram of a duplexer according to the fourth embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a cross-sectional view of an acoustic wave device 100 according to Example 1, and FIG. 1(b) is a plan view in the vicinity of FIG. 1(a). 2(a) is a plan view of the acoustic wave device 100 according to Example 1, and FIG. 2(b) is an enlarged cross-sectional view of the vicinity of the step 44 in FIG. 1(a). As shown in FIGS. 1A and 1B, the acoustic wave device 100 includes a substrate 10 having a piezoelectric substrate 14 bonded to the upper surface of a support substrate 12. As shown in FIGS. In the substrate 10, an insulating layer 16 may be provided between the support substrate 12 and the piezoelectric substrate 14. The support substrate 12 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 14 is, for example, a lithium tantalate substrate or a lithium niobate substrate. The linear expansion coefficient of the support substrate 12 is smaller than that of the piezoelectric substrate 14. The insulating layer 16 is, for example, a single layer film such as a silicon oxide layer, an aluminum oxide layer, or a silicon nitride layer, or a laminated film containing these.

The substrate 10 has a region on the support substrate 12 where the piezoelectric substrate 14 is provided and a region where the piezoelectric substrate 14 is not provided. Therefore, the upper surface 30 of the substrate 10 has a substantially flat first region 40 and a substantially flat second region 42 located closer to the lower surface 32 of the substrate 10 than the first region 40 . A first region 40 of the upper surface 30 of the substrate 10 is the upper surface of the piezoelectric substrate 14 , and a second region 42 is the upper surface of the support substrate 12 . A step 44 is formed between the first region 40 and the second region 42, and a side surface 46 of the step 44 is an obliquely inclined surface. The side surface 46 of the step 44 is the side surface of the piezoelectric substrate 14, and in the case where the insulating layer 16 is provided, the side surface 46 is the side surface of the piezoelectric substrate 14 and the insulating layer 16. The lower surface 32 of the substrate 10 is generally flat. In FIG. 1B, the side surface 46 of the step 44 between the first region 40 and the second region 42 is hatched for clarity.

An acoustic wave element 18 is provided on the upper surface of the piezoelectric substrate 14. That is, the acoustic wave element 18 is provided in the first region 40 of the upper surface 30 of the substrate 10. Via wiring 20 passing through the support substrate 12 is provided in a region where the piezoelectric substrate 14 is not provided. That is, below the second region 42 of the upper surface 30 of the substrate 10, the via wiring 20 is provided that penetrates from the upper surface 30 to the lower surface 32 of the substrate 10. A terminal 22 that contacts the via wiring 20 is provided on the lower surface 32 of the substrate 10 . The terminal 22 is a foot pad for connecting the acoustic wave element 18 to the outside. The via wiring 20 and the terminal 22 are, for example, a metal layer such as a copper layer, an aluminum layer, a platinum layer, a nickel layer, or a gold layer.

A metal layer 50 is provided from the second region 42 to the side surface 46 of the step 44 between the first region 40 and the second region 42 . The metal layer 50 includes a first portion 52 provided in the second region 42 and a second portion that is continuous from the first portion 52 and protrudes from the first portion 52 along the side surface 46 of the step 44. It has a portion 54. The first portion 52 overlaps and contacts the via wiring 20 in plan view. The first portion 52 is larger than the via wiring 20 in plan view and covers the entire via wiring 20. A tip 56 of the second portion 54 is located on the side surface 46 of the step 44 . The metal layer 50 serves as a pad.

The metal layer 50 has a protrusion 58 on the peripheral edge. The protrusions 58 are formed by burrs generated when forming the metal layer 50. The burr is formed not only at the periphery of the first portion 52 of the metal layer 50 but also at the periphery of the second portion 54 . However, the burrs formed on the second portion 54 are tilted down compared to the burrs formed on the first portion 52, and are provided along the side surface 46 of the step 44. Details of this point will be described later. The metal layer 50 is, for example, a titanium layer, a titanium nitride layer, a nickel layer, a tungsten layer, a chromium layer, a tin layer, or a platinum layer.

A metal layer 60 is provided that overlaps the first portion 52 and the second portion 54 of the metal layer 50 and extends from the second region 42 to the first region 40 via the side surface 46 of the step 44. Metal layer 60 is in contact with acoustic wave element 18 and metal layer 50 . Therefore, the acoustic wave element 18 is electrically connected to the terminal 22 via the metal layer 60, the metal layer 50, and the via wiring 20. The metal layer 60 plays a role as a wiring that electrically connects the acoustic wave element 18 and the via wiring 20. The metal layer 60 is formed of a material with relatively low electrical resistivity, such as a gold layer, a copper layer, a silver layer, an aluminum layer, or a magnesium layer.

As shown in FIGS. 1(a), 1(b), and 2(a), an annular metal layer 24 is provided at the periphery of the substrate 10, surrounding the piezoelectric substrate 14. An annular bonding layer 26 is provided on the annular metal layer 24 . A lid 28 is provided on the annular bonding layer 26. In FIG. 2(a), the lid 28 is hatched. In FIG. 1(b), the piezoelectric substrate 14 and the like are illustrated with the lid 28 seen through. The annular bonding layer 26 bonds the annular metal layer 24 and the lid 28 together. The annular metal layer 24 is, for example, a nickel layer or a copper layer. The annular bonding layer 26 is, for example, solder such as tin silver or tin silver copper. The lid 28 is, for example, a metal plate such as Kovar or an insulating plate such as a sapphire substrate. The acoustic wave element 18 is sealed in a gap 29 by the annular metal layer 24 , the annular bonding layer 26 , and the lid 28 .

As shown in FIG. 2(b), the thickness T1 of the metal layer 50 is, for example, 0.05 μm to 2 μm. The metal layer 60 is thicker than the metal layer 50, for example, and the thickness T2 is, for example, 0.2 μm to 10 μm. The width W of the step 44 between the first region 40 and the second region 42 is, for example, 2 μm to 18 μm. The inclination angle θ of the side surface 46 of the step 44, which corresponds to the inclination angle of the side surface of the piezoelectric substrate 14, is, for example, 40° to 70°. The height H1 of the step 44, which corresponds to the thickness of the piezoelectric substrate 14, is, for example, 2 μm to 15 μm. The height H1 of the step 44 is, for example, 1.5 times or more the sum of the thickness T1 of the metal layer 50 and the thickness T2 of the metal layer 60, and may be twice or more. The distance L between the tip 56 of the second portion 54 of the metal layer 50 and the lower end of the side surface 46 of the step 44 is, for example, 1/5 or more and 2/3 or less of the width W of the step 44, and 1/4 or more. It may be 1/2 or less, or it may be 1/3 or more and 1/2 or less. The height H2 from the bottom of the step 44 to the tip 56 of the second portion 54 of the metal layer 50 is, for example, 1/5 or more and 2/3 or less, and 1/4 or more and 1/2 of the height H1 of the step 44. It may be less than or equal to 1/3 or more and less than or equal to 1/2.

The second portion 54 of the metal layer 50 has a tapered shape that tapers toward a tip 56. That is, in the direction perpendicular to the side surface 46 of the step 44, the thickness at the point 55 located on the tip 56 side of the second portion 54 is the same as the thickness at the point 57 located below the step 44 than the point 55. It's smaller than that.

FIG. 3 is a plan view of the acoustic wave element 18 in Example 1. As shown in FIG. 3, the acoustic wave element 18 in Example 1 is a surface acoustic wave resonator. An IDT (Interdigital Transducer) 70 and a reflector 71 are formed on the piezoelectric substrate 14. The IDT 70 has a pair of comb-shaped electrodes 72 facing each other. The comb-shaped electrode 72 has a plurality of electrode fingers 73 and a bus bar 74 connecting the plurality of electrode fingers 73. Reflectors 71 are provided on both sides of the IDT 70. The IDT 70 excites surface acoustic waves in the piezoelectric substrate 14. The wavelength of the elastic wave is approximately equal to the pitch of the electrode fingers 73 of one of the pair of comb-shaped electrodes 72 . That is, the wavelength of the elastic wave is approximately equal to twice the pitch of the electrode fingers 73 of the pair of comb-shaped electrodes 72. The IDT 70 and the reflector 71 are formed of, for example, an aluminum film, a copper film, or a molybdenum film. A protective film or a temperature compensation film may be provided on the piezoelectric substrate 14 so as to cover the IDT 70 and the reflector 71.

[Production method]
FIGS. 4A to 6C are cross-sectional views showing a method of manufacturing the acoustic wave device 100 according to the first embodiment. As shown in FIG. 4A, a hole 90 is formed by irradiating the upper surface of the support substrate 12 with a laser beam. When the hole 90 is formed by irradiating the laser beam, the side surface of the hole 90 becomes tapered. A seed layer 91 is formed on the inner surface of the hole 90 and the upper surface of the support substrate 12 using, for example, a sputtering method. A plating layer 92 is formed on the seed layer 91 using, for example, a plating method. The seed layer 91 and the plating layer 92 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 91 and the support substrate 12. The plating layer 92 and seed layer 91 formed on the upper surface of the supporting substrate 12 are planarized using, for example, a CMP (Chemical Mechanical Polishing) method so that the upper surface of the supporting substrate 12 is exposed. As a result, a metal layer 93 consisting of a seed layer 91 and a plating layer 92 is formed in the hole 90. In the following drawings, the seed layer 91 and the plating layer 92 are not shown and are shown as a metal layer 93.

As shown in FIG. 4(b), the upper surface of the support substrate 12 and the lower surface of the piezoelectric substrate 14 are bonded by room-temperature bonding using, for example, a surface activation method. For example, the upper surface of the support substrate 12 and the lower surface of the piezoelectric substrate 14 are bonded with an insulating layer 16 interposed therebetween. The support substrate 12 and the piezoelectric substrate 14 may be directly bonded via an amorphous layer or the like of several nm. The upper surface of the piezoelectric substrate 14 is planarized by, for example, CMP. This allows the piezoelectric substrate 14 to have a desired thickness. A substrate 10 is formed by the support substrate 12, the insulating layer 16, and the piezoelectric substrate 14. Next, the acoustic wave element 18 is formed on the upper surface of the piezoelectric substrate 14 using, for example, a sputtering method or a vacuum evaporation method.

As shown in FIG. 4C, an opening 94 penetrating the piezoelectric substrate 14 and the insulating layer 16 is formed using, for example, a wet etching method or a dry etching method. At this time, the supporting substrate 12 is hardly etched. Opening 94 is formed so that metal layer 93 is exposed. The side surface of the opening 94 is tapered. Thereby, the upper surface 30 of the substrate 10 has a substantially flat first region 40 corresponding to the upper surface of the piezoelectric substrate 14 and a substantially flat second region 40 corresponding to the upper surface of the supporting substrate 12 and recessed with respect to the first region 40. It comes to have a region 42. A step 44 is formed between the first region 40 and the second region 42, and a side surface 46 of the step 44 has a tapered shape. The metal layer 93 is not exposed on the lower surface 32 of the substrate 10.

As shown in FIG. 5A, a mask layer 96 having an opening 95 in a region where the metal layer 50 is to be formed is formed on the substrate 10. The mask layer 96 is, for example, a resist film. Opening 95 in mask layer 96 exposes at least a portion of second region 42 on top surface 30 of substrate 10 . At least a portion of the side surface of the opening 95 in the mask layer 96 is provided on the side surface 46 of the step 44 between the first region 40 and the second region 42 .

As shown in FIG. 5B, using the mask layer 96 as a mask, the metal layer 50 is formed on the substrate 10 using, for example, a sputtering method or a vacuum evaporation method. A burr 97 is formed on the side surface of the opening 95 in the mask layer 96 .

As shown in FIG. 5C, the mask layer 96 is removed using an etching solution, washed with pure water, and then the pure water is removed by drying. After removing the mask layer 96, among the burrs 97 formed on the metal layer 50, the burrs 97 located on the side surface 46 of the step 44 fall down along the side surface 46 of the step 44, and at least a part of the burr 97 is located on the side surface 46 of the step 44. be in contact with The reason for this will be explained later. Thereby, the metal layer 50 extends from the first portion 52 formed in the second region 42 of the upper surface 30 of the substrate 10 and continues from the first portion 52 and extends along the side surface 46 of the step 44. 52 and a second portion 54 whose tip 56 is located on the side surface 46 of the step 44. A protrusion 58 made of a burr 97 is formed on at least a portion of the periphery of the metal layer 50 other than the second portion 54 . The first portion 52 of the metal layer 50 overlaps and contacts the metal layer 93.

As shown in FIG. 6A, a metal layer 60 is formed on the substrate 10, overlapping the first portion 52 and the second portion 54 of the metal layer 50 and extending from the second region 42 to the first region 40. For example, it is formed using a sputtering method or a vacuum evaporation method. Metal layer 60 electrically connects acoustic wave element 18 and metal layer 50 and metal layer 93.

As shown in FIG. 6B, an annular metal layer 24 and an annular bonding layer 26 are formed on the peripheral edge of the substrate 10 using, for example, a plating method. Next, the lid 28 is mounted on the annular bonding layer 26 and heated to bond the annular bonding layer 26 and the lid 28 together. Thereby, the acoustic wave element 18 is sealed in the air gap 29.

As shown in FIG. 6(c), the lower surface of the support substrate 12 is polished or ground. As a result, the support substrate 12 becomes thinner. A metal layer 93 is exposed from the lower surface 32 of the substrate 10, and the metal layer 93 becomes the via wiring 20 penetrating from the upper surface 30 of the substrate 10 to the lower surface 32. A terminal 22 that contacts the via wiring 20 is formed on the lower surface 32 of the substrate 10 using, for example, a sputtering method or a vacuum evaporation method. Through the above steps, the acoustic wave device 100 according to the first embodiment is formed.

[Comparative example 1]
7(a) is a cross-sectional view of the acoustic wave device 1000 according to Comparative Example 1, and FIG. 7(b) is an enlarged cross-sectional view of the vicinity of the step 44 in FIG. 7(a). As shown in FIG. 7A, in Comparative Example 1, the metal layer 50 was not provided. A metal layer 60 extending from the second region 42 of the upper surface 30 of the substrate 10 to the first region 40 via the side surface 46 of the step 44 is in contact with the via wiring 20 in the second region 42 . The other configurations are the same as those in the first embodiment, so the explanation will be omitted.

As shown in FIG. 7B, when the thickness of the metal layer 60 in the second region 42 is T3 and the inclination angle of the side surface 46 of the step 44 is θ, the thickness of the metal layer 60 on the side surface 46 of the step 44 is The thickness T4 is approximately T4=T3×cosθ. Since θ is, for example, 40° to 70°, the thickness T4 of the metal layer 60 on the side surface 46 of the step 44 is thinner than the thickness T3 of the metal layer 60 in the second region 42. Further, the thickness T4 of the metal layer 60 becomes thinner toward the lower side of the side surface 46 of the step 44. Therefore, in Comparative Example 1, the electrical resistance of the metal layer 60 on the side surface 46 of the step 44 becomes high, and the electrical resistance of the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20 increases. Resistance will become high.

[Comparative example 2]
8(a) is a cross-sectional view of an acoustic wave device 1100 according to comparative example 2, and FIG. 8(b) is an enlarged cross-sectional view of the vicinity of the step 44 in FIG. 8(a). As shown in FIGS. 8(a) and 8(b), in Comparative Example 2, the surface of the second portion 54 of the metal layer 50 is flush with the surface of the first portion 52, and The portion 54 is less raised than the first portion 52. The other configurations are the same as those in the first embodiment, so the explanation will be omitted.

In Comparative Example 2, since the surface of the second portion 54 of the metal layer 50 is flush with the surface of the first portion 52, the metal layer 60 on the side surface 46 of the step 44 is similar to Comparative Example 1. The thickness T4 becomes thinner toward the bottom of the side surface 46. Therefore, the electrical resistance of the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20 becomes high.

[Comparative example 3]
9(a) is a cross-sectional view of an acoustic wave device 1200 according to comparative example 3, and FIG. 9(b) is an enlarged cross-sectional view of the vicinity of the step 44 in FIG. 9(a). As shown in FIGS. 9A and 9B, in Comparative Example 3, the metal layer 50 is provided only in the second region 42, and the step 44 between the first region 40 and the second region 42 is It is not provided on the side surface 46. A protrusion 58 made of burr is formed on the periphery of the metal layer 50 . Therefore, the metal layer 60 is formed so as to overlap the protrusion 58 . The other configurations are the same as those in the first embodiment, so the explanation will be omitted.

In Comparative Example 3, since the metal layer 50 is provided only in the second region 42, similarly to Comparative Example 1, the thickness T4 of the metal layer 60 on the side surface 46 of the step 44 is thinner toward the bottom of the side surface 46. Become. Therefore, the electrical resistance of the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20 becomes high. Moreover, since the metal layer 60 is provided to overlap the protrusion 58 made of burr, the thickness of the metal layer 60 near the protrusion 58 becomes thinner, and in some cases, the metal layer 60 may be interrupted. This also increases the electrical resistance of the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20.

[About burrs formed on metal layer 50]
In Example 1 and Comparative Example 3, burrs formed on the periphery of the metal layer 50 will be described. The manner in which burrs are formed differs between Example 1 and Comparative Example 3. This will be explained using FIGS. 10(a) to 11(e).

FIGS. 10(a) to 10(e) are cross-sectional views showing the process of forming burrs 97 in Comparative Example 3. As shown in FIG. 10A, in Comparative Example 3, a mask layer 96 is formed which has an opening 95 in the second region 42 of the upper surface 30 of the substrate 10, and the side surface of the opening 95 is located on the second region 42. do. Thereafter, using the mask layer 96 as a mask, the metal layer 50 is formed using a sputtering method or a vacuum evaporation method. At this time, burrs 97 are formed on the side surfaces of the openings 95 in the mask layer 96.

As shown in FIG. 10B, after the mask layer 96 is removed using an etching solution, the etching solution is washed away with pure water 98.

As shown in FIGS. 10(c) to 10(e), the pure water 98 is removed by a drying process such as spin drying. At this time, the same amount of water droplets 99 adhere to both sides of the burr 97, and these water droplets 99 are gradually removed. Since the same amount of water droplets 99 adhere to both sides of the burr 97, in the process of removing the water droplets 99, the burr 97 is pulled by the same force from both sides. Therefore, it is considered that in Comparative Example 3, the burr 97 remains in a protruding shape.

Therefore, in Comparative Example 3, a protrusion 58 made of burr is formed at the periphery of the metal layer 50, as shown in FIG. 9(b). Therefore, the metal layer 60 becomes thinner at the portion where the protrusion 58 is formed, and the electrical resistance of the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20 increases. Furthermore, if the protrusion 58 is large, the metal layer 60 may be interrupted by the protrusion 58, causing disconnection in the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20. There is also.

11(a) to 11(e) are cross-sectional views showing the process of forming burrs 97 in Example 1. FIG. As shown in FIG. 11(a), in the first embodiment, an opening 95 is provided in the second region 42 of the upper surface 30 of the substrate 10, and the side surface of the opening 95 is located between the first region 40 and the second region 42. A mask layer 96 located on the side surface 46 of the step 44 is formed. Thereafter, using the mask layer 96 as a mask, the metal layer 50 is formed using a sputtering method or a vacuum evaporation method. At this time, burrs 97 are formed on the side surfaces of the openings 95 in the mask layer 96.

As shown in FIG. 11B, after removing the mask layer 96 using an etching solution, the etching solution is washed away with pure water 98.

As shown in FIGS. 11(c) to 11(e), the pure water 98 is removed by a drying process such as spin drying. At this time, since the burr 97 is formed on the side surface 46 of the step 44, the amount of water droplets 99 adhering to both sides of the burr 97 is reduced on the side surface 46 side of the step 44. As a result, in the process of removing the water droplets 99, the burr 97 is pulled toward the side surface 46 of the step 44 where the interval is narrow and the amount of water droplets 99 is small. Therefore, it is considered that the burr 97 on the side surface 46 of the step 44 falls down along the side surface 46.

Therefore, according to Example 1, as shown in FIGS. 1(a) and 2(b), the metal layer 50 (first metal layer) a second portion that is continuous from the first portion 52, is provided along the side surface 46 of the step 44 and is raised from the first portion 52, and has a tip 56 located on the side surface 46 of the step 44; 54. The metal layer 60 (second metal layer) is provided from the second region 42 to the first region 40, overlapping the first portion 52 and the second portion 54 of the metal layer 50. As the metal layer 60 overlaps the second portion 54 of the metal layer 50 provided on the side surface 46 of the step 44, the metal layer 60 becomes thinner below the side surface 46 of the step 44, as shown in FIG. 2(b). It is suppressed from becoming. Therefore, it is possible to suppress an increase in the electrical resistance of the metal layer 60 (wiring) that electrically connects the acoustic wave element 18 and the via wiring 20.

In order to prevent the metal layer 60 from becoming thinner, the distance L between the tip 56 of the second portion 54 of the metal layer 50 and the lower end of the side surface 46 of the step 44 in FIG. The width W is preferably 1/5 or more, more preferably 1/4 or more, and even more preferably 1/3 or more. If the distance L becomes too long, the effect of suppressing the thinning of the metal layer 60 will be weakened, so the distance L is preferably 2/3 or less, and more preferably 1/2 or less, of the width W of the step 44. In order to prevent the metal layer 60 from becoming thinner, the height H2 from the bottom of the step 44 to the tip 56 of the second portion 54 of the metal layer 50 in FIG. It is preferably 1/5 or more, more preferably 1/4 or more, and even more preferably 1/3 or more of H1. If the height H2 becomes too high, the effect of suppressing the thinning of the metal layer 60 will be weakened, so the height H2 is preferably 2/3 or less of the height H1 of the step 44, and more preferably 1/2 or less. preferable.

Further, according to the first embodiment, the entire metal layer 60 overlaps the second portion 54 of the metal layer 50 on the side surface 46 of the step 44, as shown in FIG. 1(b). This prevents the metal layer 60 from becoming thinner on the side surface 46 of the step 44, and prevents the electrical resistance of the metal layer 60 connecting the acoustic wave element 18 and the via wiring 20 from increasing.

Further, according to the first embodiment, as described in FIGS. 11(a) to 11(e), the second portion 54 of the metal layer 50 includes burrs 97 generated during the formation process of the metal layer 50. . In this case, since the burr 97 is formed to fall down along the side surface 46 of the step 44, thinning of the metal layer 60 due to the burr 97 is suppressed. Therefore, it is possible to suppress an increase in the electrical resistance of the metal layer 60 that connects the acoustic wave element 18 and the via wiring 20.

Further, according to the first embodiment, as shown in FIG. 2B, the second portion 54 of the metal layer 50 has a tapered shape that tapers toward the tip 56 in cross-sectional view. In this case, the metal layer 60 overlapping the second portion 54 of the metal layer 50 is less likely to become thin. Note that the second portion 54 of the metal layer 50 may have a shape other than this tapered shape. FIG. 12 is a cross-sectional view showing an example of another shape of the second portion 54 of the metal layer 50. As shown in FIG. 12, the second portion 54 of the metal layer 50 may vary little in thickness toward the tip 56. As shown in FIG. In this case, in the direction perpendicular to the side surface 46 of the step 44, the thickness of the second portion 54 at a portion located on the tip 56 side is lower than the portion located on the tip 56 side. The thickness will be approximately equal to the thickness at the point where the In this way, the thickness in the direction perpendicular to the side surface 46 of the step 44 at the first location located on the tip 56 side of the second portion 54 of the metal layer 50 is greater than that at the first location of the second portion 54. Since the thickness in the direction perpendicular to the side surface 46 of the step 44 at the second location located below the step 44 is less than or equal to the thickness, the metal layer 60 overlapping the second portion 54 of the metal layer 50 becomes difficult to become thin. .

Further, according to the first embodiment, as shown in FIG. 1(a), via wiring 20 is provided in the substrate 10, penetrating from the upper surface 30 to the lower surface 32. The via wiring 20 overlaps and contacts the first portion 52 of the metal layer 50 in a plan view. In this case, metal layer 50 serves as a pad. By making the metal layer 50 have a structure including the first portion 52 and the second portion 54, it is possible to prevent the metal layer 60 provided on the metal layer 50 and serving as a wiring from becoming thinner. Therefore, it is possible to suppress the electric resistance of the wiring connecting the acoustic wave element 18 and the via wiring 20 from increasing.

Further, according to the first embodiment, as shown in FIG. 1(a), the substrate 10 includes a support substrate 12 and a piezoelectric substrate 14 bonded onto the support substrate 12. The first region 40 of the upper surface 30 of the substrate 10 is the upper surface of the piezoelectric substrate 14 , the step 44 is provided through the piezoelectric substrate 14 , and the side surface 46 of the step 44 includes the side surface of the piezoelectric substrate 14 . For reasons such as characteristics, a substrate 10 having a piezoelectric substrate 14 bonded to a support substrate 12 may be used. In such a case, by using the metal layer 50 and the metal layer 60 shown in Example 1, it is possible to suppress the electrical resistance of the metal layer 60 (wiring) from increasing.

According to the manufacturing method of the first embodiment, as shown in FIG. A mask layer 96 is formed on the side surface 46 of the step 44 between the second region 42 and the second region 42 . As shown in FIG. 5B, the metal layer 50 is formed using the mask layer 96 as a mask. As shown in FIG. 5C, after forming the metal layer 50, the mask layer 96 is removed. As shown in FIG. 6A, after removing the mask layer 96, the first portion 52 of the metal layer 50 provided in the second region 42 and the side surface 46 of the step 44 are raised from the first portion 52. A metal layer 60 is formed so as to overlap with the second portion 54 of the metal layer 50 provided, extend from the second region 42 to the first region 40, and electrically connect to the acoustic wave element 18. Thereby, it is possible to suppress the metal layer 60 from becoming thinner on the side surface 46 of the step 44. Therefore, it is possible to suppress an increase in the electrical resistance of the metal layer 60 that connects the acoustic wave element 18 and the via wiring 20.

Further, according to the manufacturing method of Example 1, as shown in FIGS. 5(b) and 5(c), the burr 97 formed on the metal layer 50 due to the film formation of the metal layer 50 is The mask layer 96 is removed so that it falls down along the side surface 46 of the step 44. In this manner, the burr 97 falls down along the side surface 46 of the step 44, thereby suppressing the thinning of the metal layer 60 due to the burr 97. Therefore, it is possible to suppress an increase in the electrical resistance of the metal layer 60 that connects the acoustic wave element 18 and the via wiring 20.

Further, according to the manufacturing method of Example 1, as shown in FIG. 5B and FIG. A metal layer 50 is formed using a method. Thereafter, as shown in FIG. 5(c) and FIG. 11(b) to FIG. 11(e), the mask layer is coated with a liquid so that the burr 97 formed on the metal layer 50 falls down after the mask layer 96 is removed. Remove 96. When the metal layer 50 is formed by sputtering or vapor deposition using the mask layer 96 as a mask, burrs 97 are likely to be formed on the metal layer 50, but by removing the mask layer 96 using a liquid, the burrs 97 can be removed from the mask layer. After the removal of the step 96, the step 44 tends to fall down along the side surface 46.

Furthermore, according to the manufacturing method of Example 1, the liquid used to remove the mask layer 96 is dried so that the burrs 97 formed on the metal layer 50 collapse after the mask layer 96 is removed. This makes it easier for the burr 97 to fall down along the side surface 46 of the step 44.

In the first embodiment, at least a portion of the peripheral portion of the metal layer 50 that does not overlap with the metal layer 60 may be provided on the side surface 46 of the step 44. This reduces the number of protrusions 58 formed on the periphery of the metal layer 50. Furthermore, the metal layer 60 is not limited to being formed from the first region 40 to the second region 42 so that the acoustic wave element 18 is electrically connected to the via wiring 20; It may be formed extending from the first region 40 to the first region 40 via the second region 42 so as to electrically connect two acoustic wave elements 18 .

13(a) is a cross-sectional view of the acoustic wave device 200 according to the second embodiment, and FIG. 13(b) is a cross-sectional view of the acoustic wave element 18 in the second example. As shown in FIG. 13A, in the second embodiment, the piezoelectric substrate 14 is not bonded to the upper surface of the support substrate 12, and the substrate 10 is constituted by the support substrate 12. A recess 34 is formed in the upper surface 30 of the substrate 10, and a via wiring 20 is formed below the recess 34. By forming the recess 34, the upper surface 30 of the substrate 10 has a substantially flat first region 40 and a substantially flat second region 42 located closer to the lower surface 32 than the first region 40. The other configurations are the same as those in the first embodiment, so the explanation will be omitted.

As shown in FIG. 13(b), the acoustic wave element 18 in Example 2 is a piezoelectric thin film resonator. A piezoelectric film 76 is provided on the substrate 10. A lower electrode 75 and an upper electrode 77 are provided so as to sandwich the piezoelectric film 76 therebetween. A gap 78 is formed between the lower electrode 75 and the substrate 10. A region where the lower electrode 75 and the upper electrode 77 face each other with at least a portion of the piezoelectric film 76 in between is a resonance region 79. In the resonance region 79, the lower electrode 75 and the upper electrode 77 excite elastic waves in the thickness longitudinal vibration mode within the piezoelectric film 76. The substrate 10 is, for example, a sapphire substrate, a spinel substrate, an alumina substrate, a glass substrate, a crystal substrate, or a silicon substrate. The lower electrode 75 and the upper electrode 77 are, for example, metal films such as ruthenium films. The piezoelectric film 76 is, for example, an aluminum nitride film. An acoustic reflective film that reflects elastic waves may be provided instead of the void 78.

FIG. 14 is a circuit diagram of a filter 300 according to the third embodiment. As shown in FIG. 14, one or more series resonators S1 to S3 are connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 and P2 are connected in parallel between the input terminal Tin and the output terminal Tout. The acoustic wave devices of the first and second embodiments may be used in the filter 300 of the third embodiment. The number of series resonators and parallel resonators can be set as appropriate. Although a ladder type filter is shown as an example of the filter, the filter may be a multimode type filter.

FIG. 15 is a block diagram of a duplexer 400 according to the fourth embodiment. As shown in FIG. 15, a transmission filter 80 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 82 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 80 passes a signal in the transmission band among the high-frequency signals inputted from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies. The reception filter 82 passes a signal in the reception band among the high-frequency signals inputted from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals at other frequencies. At least one of the transmission filter 80 and the reception filter 82 can be the filter of the third embodiment. Although a duplexer is shown as an example of a multiplexer, a triplexer or a 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 such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention as described in the claims. Changes are possible.

10 Substrate 12 Support substrate 14 Piezoelectric substrate 16 Insulating layer 18 Acoustic wave element 20 Via wiring 22 Terminal 24 Annular metal layer 26 Annular bonding layer 28 Lid 29 Gap 30 Upper surface of substrate 32 Lower surface of substrate 34 Recess 40 First region 42 Second region 44 Step 46 Side face of step 50 Metal layer 52 First portion 54 Second portion 55 Location 56 Tip 57 Location 58 Projection 60 Metal layer 80 Transmission filter 82 Reception filter 95 Opening 96 Mask layer 97 Burr 98 Pure water 99 Water droplet 100 , 200, 1000, 1100, 1200 Acoustic wave device 300 Filter 400 Duplexer

Claims (11)

The first surface has a first surface and a second surface opposite to the first surface, and the first surface has a first region and a second region located closer to the second surface than the first region. , a step having an oblique side surface between the first region and the second region;
an acoustic wave element provided in the first region;
a first portion provided in the second region; a first portion that is continuous from the first portion, is provided along the side surface of the step and is raised from the first portion, and has a tip above the side surface of the step; a first metal layer having a second portion located at
a second metal layer that is provided from the second region to the first region so as to overlap the first portion and the second portion of the first metal layer, and is electrically connected to the acoustic wave element; An elastic wave device equipped with The substrate includes a support substrate and a piezoelectric substrate bonded to the support substrate, the first region is an upper surface of the piezoelectric substrate, the step is provided to penetrate the piezoelectric substrate, and the step is formed by penetrating the piezoelectric substrate. The acoustic wave device according to claim 1, wherein the side surface includes a side surface of the piezoelectric substrate. 3. The acoustic wave device according to claim 1, wherein the second metal layer entirely overlaps the second portion of the first metal layer on the side surface of the step in plan view. In a cross-sectional view, the thickness of the step in the direction perpendicular to the side surface at the first location located on the tip side of the second portion of the first metal layer is equal to the thickness of the second portion of the first metal layer. 4. The acoustic wave device according to claim 1, wherein the thickness of the step in the vertical direction is less than or equal to the thickness of the step at a second location located below the step than the first location. Provided in the substrate so as to penetrate from the first surface to the second surface, overlap with the first portion of the first metal layer in plan view, and contact the first portion of the first metal layer. The acoustic wave device according to any one of claims 1 to 4, comprising a via wiring. A filter comprising the elastic wave device according to any one of claims 1 to 5. A multiplexer comprising a filter according to claim 6. It has a first surface and a second surface opposite to the first surface, and the first surface has a first region in which an acoustic wave element is formed and a region closer to the second surface than the first region. an opening exposing the second region on the first surface of the substrate, the substrate having a second region located at the second region, and a step having an obliquely inclined side surface between the first region and the second region. forming a mask layer having a side surface of the opening located on the side surface of the step;
forming a first metal layer using the mask layer as a mask;
After forming the first metal layer, removing the mask layer;
After removing the mask layer, a first portion of the first metal layer provided in the second region and the first metal layer provided protruding from the first portion along the side surface of the step. forming a second metal layer that extends from the second region to the first region and electrically connects to the acoustic wave element, overlapping a second portion of the acoustic wave device. The step of removing the mask layer includes removing the mask layer so that the burrs formed on the first metal layer by forming the first metal layer fall down along the sides of the step after the mask layer is removed. 9. The method for manufacturing an acoustic wave device according to claim 8, wherein: In the step of forming the first metal layer, the first metal layer is formed from the second region exposed in the opening to the side surface of the opening using a sputtering method or a vapor deposition method,
10. The method of manufacturing an acoustic wave device according to claim 9, wherein in the step of removing the mask layer, the mask layer is removed using a liquid so that the burr falls down after the mask layer is removed. 11. The method of manufacturing an acoustic wave device according to claim 10, wherein the step of removing the mask layer includes the step of drying the liquid so that the burr collapses after the mask layer is removed.

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