Elastic wave device

Abstract

To prevent as much as possible a situation in which a device is touched by a cover layer forming the elastic wave device when cover layer forms a sealing resin layer in a module substrate.SOLUTION: The present invention includes: a device chip 2; a resonator 7 formed in one surface 2a of the device chip 2; a support layer 3 surrounding the resonator 7 in the surface; and a cover layer 4 formed on the support layer 3, the cover layer working with the device chip 2 and the support layer 3 to form a cavity 5 which airproofs the resonator 7. The cover layer 4 on at least one cavity 5 is bent so that the formation side of the resonator 7 is a bending inner side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an improvement in an acoustic wave device suitable for use as a frequency filter in mobile communication devices and the like. [Background technology]

[0002] An acoustic wave device D used as a frequency filter or the like in mobile communication devices or the like is shown in Fig. 9. In Fig. 9, reference numeral 100 denotes a device chip, reference numeral 101 denotes a resonator 101 formed on one surface of the device chip 100, reference numeral 102 denotes a support layer made of synthetic resin formed on the device chip 100, reference numeral 103 denotes a cover layer made of synthetic resin formed on the support layer 102 to form a cavity 104 (internal space, hollow structure) that hermetically seals the resonator 101, and reference numeral 105 denotes a bump electrically connected to a circuit formed on the device chip 100 including the resonator 101.

[0003] The acoustic wave device D is mounted on a module substrate Ma together with other electronic devices using the bumps 105 to form a module M. The bumps 105 are typically bonded to electrodes formed on the module substrate Ma by ultrasonic bonding or the like, and after this bonding, the acoustic wave device D is sealed by a sealing resin layer Mb formed on the module substrate Ma. Since a gap S is formed between the acoustic wave device D and the module substrate Ma by the bumps 105, the sealing resin layer Ma also penetrates between the cover layer 103 of the acoustic wave device D and the module substrate Ma. Therefore, when the sealing resin layer Mb is formed, a force in a direction narrowing the distance between the cover layer 103 and the device chip 100 is applied to the cover layer 103 in no small amount. If the cover layer 103 comes into contact with the device chip 100 in the cavity 104 due to the action of such a force, the function of the acoustic wave device D will be impaired. Summary of the Invention [Problem to be solved by the invention]

[0004] The main problem that this invention aims to solve is to provide an acoustic wave device of this type with a function of preventing, as much as possible, the cover layer constituting the acoustic wave device from coming into contact with one side of the device chip or the resonator due to the force applied when forming a sealing resin layer on a module substrate after mounting the acoustic wave device on the module substrate, without complicating the structure of the acoustic wave device or its manufacturing process. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides an acoustic wave device comprising: A device chip; a resonator formed on one surface of the device chip; a support layer formed on the one surface so as to surround the resonator; a cover layer formed on the support layer to form a cavity for hermetically sealing the resonator in cooperation with the device chip and the support layer; The cover layer on at least one of the cavities is curved so that the side on which the resonator is formed is the curved inner side.

[0006] In one aspect of the present invention, a plurality of the cavities are provided, and in each of the cavities, the cover layer is curved so that the one surface side of the device chip is the curved inner side.

[0007] Moreover, the cavity is provided in a plurality of portions, At least one of the plurality of cavities is a large-room cavity in which the distance between the opposing support layers constituting the cavity is 6 to 15 times or more the thickness of the support layer in a direction perpendicular to the one surface of the device chip, At least one of the multiple cavities is a small chamber cavity in which the distance between the opposing support layers constituting the cavity is less than six times the thickness of the support layers, In one aspect of the present invention, in the large-room cavity, the cover layer is curved so that the side on which the resonator is formed is the curved inner side.

[0008] In one embodiment of the present invention, the cover layer is made of a sheet material made of a thermosetting resin and having a thickness of 15 to 35 μm. Effect of the Invention

[0009] In the acoustic wave device according to the present invention, since the cover layer is curved in advance as described above, the cover layer can easily resist the force acting on the cover layer toward one side of the device chip when forming a sealing resin layer on the module substrate after mounting the acoustic wave device on the module substrate, and even if the cover layer is deformed, it is possible to prevent the cover layer from being displaced to the extent that it comes into contact with the one side of the device chip or the resonator. Moreover, the acoustic wave device can be provided with such a function without complicating its structure and manufacturing process. This also makes it possible to improve the yield of modules that include the acoustic wave device. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of an acoustic wave device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the acoustic wave device taken along line AA in FIG. [Diagram 3] FIG. 3 is a cross-sectional view of the acoustic wave device taken along line BB in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the acoustic wave device taken along line CC in FIG. [Diagram 5] FIG. 5 is a configuration diagram showing an example of a resonator formed on a device chip of the acoustic wave device. [Figure 6]FIG. 6 is a configuration diagram showing an example of a circuit formed on a device chip of the acoustic wave device. [Figure 7] FIG. 7 is a cross-sectional view showing the steps of a manufacturing process for the acoustic wave device, the steps proceeding in the order of a, b, c, d, e, f, g, and h. [Figure 8] FIG. 8 is a cross-sectional view showing a main part of a module including the acoustic wave device. [Figure 9] FIG. 9 is a cross-sectional view showing an example of a module including a conventional acoustic wave device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to Figures 1 to 8. An acoustic wave device 1 according to this embodiment is suitable for use as a frequency filter in a mobile communication device or the like.

[0012] The acoustic wave device 1 has: A device chip 2; A resonator 7 formed on one surface 2a of the device chip 2; A support layer 3 (wall) formed on the one surface 2a so as to surround the resonator 7; The device includes a cover layer 4 (roof) formed on the support layer 3 and cooperating with the device chip 2 and the support layer 3 to form a cavity 5 (internal space, hollow structure) that hermetically seals the resonator 7.

[0013] Typically, the device chip 2 is configured in the shape of a rectangular plate with a side measuring 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm. Furthermore, typically, the support layer 3 is configured to have a thickness 3c in a direction perpendicular to one surface 2a of the device chip 2 (the height of the support layer 3 based on one surface 2a of the device chip 2) of 10 to 30 μm. Typically, the cover layer 4 is configured to have a thickness 4f of 15 to 35 μm. The acoustic wave device 1 constructed from these components typically has a thickness of about 0.25 to 0.35 mm, including the bump height.

[0014] The planar structure of the acoustic wave device is shown in Fig. 1. In the figure, reference numeral 7 denotes a resonator, reference numeral 5 denotes a cavity, reference numeral 9 denotes a bump, reference numeral 4 denotes a cover layer, and reference numeral 6 denotes a through hole that penetrates the support layer 3 and the cover layer 4 outside the region where the cavity 5 is formed.

[0015] A plurality of resonators 7 are formed on one surface 2a of the device chip 2. The formation area of ​​each resonator 7 on one surface 2a of the device chip 2 is surrounded by a support layer 3 and is covered with a cover layer 4 formed on the support layer 3. This results in the acoustic wave device having a plurality of cavities 5.

[0016] The cross-sectional structure of the acoustic wave device is shown in Fig. 2. In the figure, reference symbol 2b denotes a bump pad (electrode pad). The bump pad 2b is connected to wiring of a circuit including the resonator 7 formed on the device chip 2. The bump pad 2b is located inside a through hole 6. This through hole 6 is used to form a bump 9 made of a conductive metal such as gold.

[0017] The device chip 2 has a function of propagating elastic waves. Typically, lithium tantalate or lithium niobate is used for the device chip 2, and the device chip 2 may be configured by laminating sapphire, silicon, alumina, spinel, quartz, glass, or the like on the device chip 2.

[0018] An example of the resonator 7 is shown in Fig. 5. The resonator 7 has an IDT electrode 7c and a reflector 7d formed so as to sandwich the IDT electrode 7c. The IDT electrode 7c is composed of an electrode pair, and each electrode pair is formed by connecting a plurality of electrode fingers 7e arranged in parallel so that their length direction crosses the propagation direction x of the elastic wave with one end side of the electrode fingers by a bus bar 7f. The reflector 7d is formed by connecting ends of a plurality of electrode fingers 7e arranged in parallel so that their length direction crosses the propagation direction x of the elastic wave with a bus bar 7f. Such a resonator 7 is typically made of a conductive metal film formed by photolithography.

[0019] Fig. 6 shows the concept of an example of a circuit provided on one device chip 2. Reference numeral 7a denotes a resonator connected in series between input and output ports, reference numeral 7b denotes a resonator connected in parallel between input and output ports, and reference numeral 8 denotes a ground. The number and arrangement of the resonators 7 can be changed as necessary. In other words, a ladder-type filter is configured by the circuit in Fig. 6.

[0020] In the acoustic wave device according to this embodiment, the cover layer 4 on at least one of the cavities 5 is curved so that the side on which the resonator 7 is formed is the curved inner side.

[0021] In the example shown, the cover layer 4 is curved to create an apex 4a on the central side 5a of the cavity 5 when the acoustic wave device 1 is broken in a direction parallel to any one side of the device chip 2 having a rectangular outline (for example, a state where it is broken along the left-right direction in Figure 1 / Figure 2), and at the same time, it is curved to create an apex 4a on the central side 5a of the cavity 5 even when the acoustic wave device 1 is broken in a direction perpendicular to the one side (for example, a state where it is broken along the up-down direction in Figure 1 / Figures 3 and 4).

[0022] More specifically, the cover layer 4, which serves as a lid of one cavity 5, is curved so that the distance between the cover layer 4 and one surface 2a of the device chip 2 gradually increases as the distance approaches the center 5a of the cavity 5 from a joint 4b between the end 3a of the support layer 3 protruding from the device chip 2, which serves as a wall of the cavity 5. That is, the cover layer 4 located on the resonator 7 bulges outward toward the outside of the cavity 5, that is, toward the outside of the acoustic wave device, and the outer surface of the cover layer 4 is a three-dimensional curved surface.

[0023] As shown in FIG. 8, in many cases, the acoustic wave device 1 is mounted on a module substrate 10a together with other electronic devices using the bumps 9 to form a module 10. The bumps 9 are typically bonded to electrodes 10c formed on the module substrate 10a by ultrasonic bonding or the like, and after this bonding, the acoustic wave device 1 is sealed by a sealing resin layer 10b formed on the module substrate 10a. Since a gap S (see FIG. 8) is formed between the acoustic wave device 1 and the module substrate 10a by the bumps 9, the sealing resin layer 10b also penetrates between the cover layer 4 of the acoustic wave device 1 and the module substrate 10a. For this reason, when the sealing resin layer 10b is formed, a force f (see FIG. 8) in a direction narrowing the distance between the cover layer 4 and the one surface 2a of the device chip 2 is applied to the cover layer 4 in no small amount. If the force f causes the cover layer 4 to come into contact with the one surface 2a of the device chip 2 or the resonator 7 in the cavity 5, the function of the acoustic wave device 1 will be impaired. In the acoustic wave device 1 according to this embodiment, since the cover layer 4 is curved in advance as described above, the cover layer 4 can easily resist the force f, and even if the cover layer 4 is deformed, it is possible to prevent the cover layer 4 from being displaced to the extent that it comes into contact with the surface 2a of the device chip 2 or the resonator 7. This makes it possible to improve the yield of the module 10 including the present acoustic wave device 1.

[0024] In the illustrated example, the acoustic wave device 1 includes a plurality of the cavities 5, and in each of the cavities 5, the cover layer 4 is curved so that the one surface 2a of the device chip 2 is on the inner side of the curve. In this way, it is possible to prevent the deformation of the cover layer 4 caused by the force f in each of the plurality of cavities 5.

[0025] In the illustrated example, the acoustic wave device 1 includes a plurality of the cavities 5, and at least one of the plurality of cavities 5 is a large-room cavity 5 in which the distance 3b between the opposing support layers 3 constituting the cavity 5 is 6 to 15 times or more the thickness 3c of the support layer 3 in a direction perpendicular to the surface 2a of the device chip 2 (see FIG. 3). At the same time, at least one of the plurality of cavities 5 is a small-room cavity 5 in which the distance 3b between the opposing support layers 3 constituting the cavity 5 is less than 6 times the thickness 3c of the support layer 3 (see FIG. 4). And, in at least the large-room cavity 5, the cover layer 4 is curved so that the side on which the resonator 7 is formed is the curved inner side.

[0026] In the illustrated example, each of the multiple cavities 5 has a resonator 7 located therein, and is configured such that the distance 3b between the supporting layers 3 facing each other in the propagation direction x of the acoustic wave is large and the distance 3b between the supporting layers 3 facing each other in a direction perpendicular to the propagation direction x is small, and each of the multiple cavities 5 has a length and a width when the acoustic wave device 1 is viewed in a plan view (see FIG. 1). Although not illustrated, two or more resonators 7 may be located in one cavity 5.

[0027] In the large-room cavity 5, the distance 3b between the opposing support layers 3 is large, so that the amount of displacement when the cover layer 4 is deformed by the force f is large. At least in the large-room cavity 5, the cover layer 4 is curved as described above, thereby achieving the object of the present invention of improving the yield of the module 10 including the present acoustic wave device 1. From another perspective, according to the present invention, it becomes easier to provide the acoustic wave device 1 with the large-room cavity 5 as described above. In the illustrated example, the cover layer 4 is also curved as described above in the small-room cavity 5, but depending on the magnitude of the force f, the cover layer 4 of the small-room cavity 5 may be flat, that is, formed so as to be parallel to one surface 2a of the device chip 2 (the outer shape of the cover layer 4 when flat is shown by the dotted line in FIG. 4).

[0028] The cover layer 4 is preferably made of a thermosetting resin sheet material 4c having a thickness 4f of 15 to 35 μm. If the thickness 4f of the cover layer 4 is less than 15 μm, the cover layer 4 becomes fragile. On the other hand, if the thickness 4f of the cover layer 4 exceeds 35 μm, the cover layer 4 becomes difficult to bend and deform in the baking process described below. It is preferable to use such a sheet material 4c that has a certain adhesive strength at room temperature and has a function of being able to remove unnecessary parts through exposure and development in photolithography technology.

[0029] On the other hand, the support layer 3 is preferably made of a synthetic resin which is easy to form on the one surface 2a of the device chip 2 and has good compatibility with the cover layer 4. The support layer 3 has a base 3d joined to the one surface 2a of the device chip 2 and a protruding end portion 3a joined to the cover layer 4, and is formed so as to protrude from the one surface 2a of the device chip 2 in a direction perpendicular to the one surface 2a of the device chip 2. The support layer 3 constitutes, so to speak, the side portion of the cavity 5.

[0030] In the illustrated example, the space between adjacent cavities 5 is solidified by the support layer 3. It is preferable that the distance 5d between adjacent cavities 5 is equal to or greater than the thickness 4f of the cover layer 4.

[0031] The acoustic wave device 1 described above can be appropriately and rationally manufactured as follows. The main steps of the manufacturing process of the acoustic wave device 1 according to this embodiment are shown in Fig. 7. For the sake of convenience, only a part of the wafer before dicing is shown as the device chip 2 in Fig. 7.

[0032] First, a resonator 7 (not shown) is formed on one surface 2a of the device chip 2 (step 1 / not shown). Typically, a plurality of resonators 7 are formed.

[0033] Next, a support layer 3 is formed on the surface 2a of the device chip 2 in an area other than the area in which the resonator 7 is formed (Step 2 / not shown).

[0034] Next, a cover layer 4 is formed on the support layer 3 (Step 3 / FIGS. 7(a) to (h)). Step 3 includes a laminating step (Steps 3-1 to 3-5), a baking step (Step 3-6), a developing step (Step 3-7), and a curing step (Step 3-8).

[0035] In the lamination process, a sheet member 4c made of a thermosetting resin is placed on the support layer 3 in an environment where the temperature is between 30 degrees Celsius and 60 degrees Celsius and the atmospheric pressure is 0.3 MPa or less. First, an original film is prepared, which has a base film 4d on the upper surface of a sheet material 4c that will become the cover layer 4, and a cover film 4e on the lower surface (Step 3-1 / FIG. 7(a)). The sheet material 4c is made of a thermosetting resin, has a certain adhesive strength at room temperature, and has the function of being able to remove unnecessary parts through exposure and development in photolithography technology. Next, the cover film 4e is peeled off from the original film (step 3-2 / FIG. 7(b)). Next, the bottom surface of the sheet-like material 4c is adhered to the protruding end 3a of the support layer 3 formed to surround the resonator 7 over the entire area thereof (step 3-3 / FIG. 7(c)). As a result, a temporary cavity 5e is formed on the resonator 7. If the distance 5d between adjacent cavities 5 is set to more than twice the thickness 4f of the cover layer 4, a large adhesion margin between the protruding end 3a of the support layer 3 that solidifies the space between adjacent cavities and the cover layer 4 can be secured, and the airtightness of the temporary cavity 5e can be maintained at a high level, including during the baking process. Next, the sheet-shaped member 4c is exposed to light (step 3-4 / FIG. 7(d)). Reference numeral 10 denotes a photomask. Next, the base film 4d is peeled off from the upper surface of the sheet member 4c (step 3-5 / FIG. 7(e)).

[0036] In the baking process, the workpiece w (intermediate product) that has been through the lamination process is heated at 100°C to 120°C for 7 to 12 minutes (step 3-6 / FIG. 7(f)). The sheet material 4c is configured to have high plasticity at such temperatures but not harden. Therefore, the cover layer 4, which is part of the sheet material 4c that constitutes the temporary cavity 5, can be curved as shown in FIG. 7(g) by the volume expansion of the gas in the temporary cavity 5. The deformation of the cover layer 4 is large in the large cavity 5, but small in the small cavity 5, or it may be considered that there is practically no deformation.

[0037] Next, unnecessary parts are removed from the sheet material 4c by development (step 3-7 / FIG. 7(g)).

[0038] In the curing process, the workpiece that has undergone the development is heated at 150°C to 200°C for 45 to 90 minutes (step 3-8 / FIG. 7(h)). The planar material 4c is configured to harden at such a temperature. As a result, the temporary cavity 5e becomes the cavity 5, and the curved shape of the cover layer 4 formed in the baking process is maintained.

[0039] After the curing step, a plurality of acoustic wave devices 1 are produced from the workpiece w by dicing.

[0040] Of course, the present invention is not limited to the above-described embodiments, but includes all embodiments that can achieve the object of the present invention. [Explanation of symbols]

[0041] 1. Acoustic Wave Devices 2. Device chip 2a one side 2b Bump Pad 3 Support layer 3a Protruding end 3b distance 3c Thickness 3d base 4 Cover Layer 4a Top 4b Joint 4c Planar material 4d base film 4e Cover film 4f Thickness 5 Cavity 5a Center side 5b Large room cavity 5c Small room cavity 5d distance 5e Temporary cavity 6 Through holes 7, 7a, 7b resonator 7c IDT electrode 7d reflector 7e electrode finger 7f Busbar 8 Grand 9. Bump 10 Modules 10a Module Board 10b Sealing resin layer 10c electrode 11 Photomask x Propagation direction f force w work

Claims

1. A device chip; a resonator formed on one surface of the device chip; a support layer formed on the one surface so as to surround the resonator; a cover layer formed on the support layer to form a cavity for hermetically sealing the resonator in cooperation with the device chip and the support layer; An acoustic wave device, comprising: the cover layer on at least one of the cavities, the cover layer being curved so that the side on which the resonator is formed is the curved inner side.

2. The acoustic wave device according to claim 1 , comprising a plurality of the cavities, and in each of the cavities, the cover layer is curved so that the one surface side of the device chip is on the inner side of the curve.

3. The cavity is provided in a plurality of portions, At least one of the plurality of cavities is a large-room cavity in which the distance between the opposing support layers constituting the cavity is 6 to 15 times or more the thickness of the support layer in a direction perpendicular to the one surface of the device chip, At least one of the multiple cavities is a small chamber cavity in which the distance between the opposing support layers constituting the cavity is less than six times the thickness of the support layers, The acoustic wave device according to claim 1 , wherein in the large cavity, the cover layer is curved so that a side on which the resonator is formed is the curved inner side.

4. 4. The acoustic wave device according to claim 1, wherein the cover layer is made of a sheet material made of a thermosetting resin and has a thickness of 15 to 35 μm.

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