Elastic wave devices

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 of an elastic wave device suitable for use as a frequency filter or the like in a mobile communication device or the like.

Background Art

[0002] There is an elastic wave device D shown in FIG. 9 that is used as a frequency filter or the like in a mobile communication device or the like. 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, and reference numeral 103 denotes a synthetic resin cover layer that forms a cavity 104 (internal space, hollow structure portion) formed on the support layer 102 to hermetically seal the resonator 101. Reference numeral 105 denotes a bump electrically connected to a circuit formed on the device chip 100 including the resonator 101.

[0003] [[ID=((16))]]Such an elastic wave device D is mounted on a module substrate Ma together with other electronic devices using the bump 105 to constitute a module M. The bump 105 is typically joined to an electrode formed on the module substrate Ma side by ultrasonic bonding or the like. After this joining, the elastic wave device D is sealed by a sealing resin layer Mb formed on the module substrate Ma. Since a gap S is formed by the bump 105 between the elastic wave device D and the module substrate Ma, this sealing resin layer Ma also enters between the cover layer 103 of the elastic wave device D and the module substrate Ma. Therefore, when forming such a sealing resin layer Mb, a force that narrows the distance between the cover layer 103 and the device chip 100 acts on the cover layer 103. If the cover layer 103 contacts the device chip 100 side within the cavity 104 due to the action of such a force, the function of the elastic wave device D will be inhibited.

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] In order to achieve the above objectives, in this invention, the elastic wave device is Device chip and A resonator formed on one surface of the device chip, A support layer formed on one surface so as to surround the resonator, Formed on the support layer and working in cooperation with the device chip and the support layer to hermetically seal the resonator. multiple It comprises a cover layer that forms a cavity, The support layer is designed so as not to have any portion that causes a difference in height relative to one surface of the device chip, The aforementioned cover layer is a surface material made of thermosetting resin with a thickness of 15 to 35 μm, which increases plasticity but does not harden at temperatures of 100 to 120 degrees Celsius, and hardens at temperatures of 150 to 200 degrees Celsius. The cover layer on at least one of the cavities is curved such that the side where the resonator is formed faces inward.

[0006] One embodiment of this invention is to provide a plurality of the aforementioned cavities, and in each of the cavities, the cover layer is curved such that the one side of the device chip is curved inward.

[0007] Furthermore, the device has multiple cavities, At least one of the multiple cavities is a large 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 one surface of the device chip. At least one of the multiple cavities is a small cavity in which the distance between the opposing support layers constituting the cavity is less than six times the thickness of the support layer. In the aforementioned large cavity, one embodiment of this invention is to curve the cover layer such that the side on which the resonator is formed is curved inward. [Effects of the Invention]

[0009] In the elastic wave device according to this invention, since the cover layer is pre-curved as described above, the cover layer can easily resist the force directed toward one side of the device chip that is applied to the module substrate when a sealing resin layer is formed on the module substrate after the elastic wave device has been mounted on the module substrate. Furthermore, even if deformation occurs, it is possible to prevent displacement that would cause contact with one side of the device chip or the resonator. Moreover, such functions can be provided to the elastic wave device without complicating its structure or manufacturing process. In addition, this can improve the yield of modules composed of this elastic wave device. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a plan view of an elastic wave device according to one embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of the elastic wave device, shown as a cross-section at the position of line AA in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the elastic wave device, shown in cross-section at the position of line BB in Figure 1. [Figure 4] Figure 4 is a cross-sectional view of the elastic wave device, shown in cross-section at the CC line position in Figure 1. [Figure 5] Figure 5 is a diagram showing an example of a resonator formed on the device chip of the elastic wave device. [Figure 6]Figure 6 is a diagram showing an example of a circuit formed on the device chip of the elastic wave device. [Figure 7] Figure 7 is a cross-sectional diagram of the main components showing each step in the manufacturing process of the elastic wave device, progressing in the order of Figures a, b, c, d, e, f, g, and h. [Figure 8] Figure 8 is a cross-sectional view of the main components of the module, which includes the elastic wave device. [Figure 9] Figure 9 is a cross-sectional diagram showing an example of a module that includes a conventional elastic wave device. [Modes for carrying out the invention]

[0011] A typical embodiment of this invention will be described below with reference to Figures 1 to 8. The elastic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication equipment and the like.

[0012] Such elastic wave device 1 is Device chip 2, A resonator 7 formed on one surface 2a of the device chip 2, A support layer 3 (wall) is formed on the aforementioned surface 2a so as to surround the resonator 7, The device comprises a cover layer 4 (roof) formed on the support layer 3, which works in cooperation 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 to be a rectangular plate with sides of 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm. Typically, the support layer 3 is configured to have a thickness 3c (height of the support layer 3 relative to one surface 2a of the device chip 2) of 10 to 30 μm in the direction perpendicular to one surface 2a of the device chip 2. Typically, the cover layer 4 is configured to have a thickness 4f of 15 to 35 μm. The surface acoustic wave device 1 composed of these typically has a thickness of about 0.25 to 0.35 mm including the bump height.

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

[0015] A plurality of resonators 7 are formed on one surface 2a of the device chip 2. The formation region of each resonator 7 on the one surface 2a of the device chip 2 is surrounded by the support layer 3 and covered with a cover layer 4 formed on the support layer 3, whereby the surface acoustic wave device 1 is provided with a plurality of the cavities 5.

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

[0017] The device chip 2 has a function of propagating surface acoustic 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 or glass thereon. <0000​​Figure 5 shows an example of a resonator 7. 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 consists of electrode pairs, and each electrode pair is formed by connecting multiple electrode fingers 7e, which are arranged in parallel so that their length intersects the propagation direction x of the elastic wave, with a busbar 7f at one end of each pair. The reflector 7d is formed by connecting the ends of multiple electrode fingers 7e, which are arranged in parallel so that their length intersects the propagation direction x of the elastic wave, with a busbar 7f. Such a resonator 7 is typically composed of a conductive metal film formed by photolithography.

[0019] Figure 6 shows a conceptual example of a circuit that can be provided on a single device chip 2. Reference numeral 7a indicates a resonator connected in series between the input / output ports, reference numeral 7b indicates a resonator connected in parallel between the input / output ports, and reference numeral 8 indicates ground. The number and arrangement of resonators 7 can be changed as needed. In other words, the circuit in Figure 6 constitutes a ladder-type filter.

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

[0021] In the illustrated example, the cover layer 4 is curved to create a vertex 4a on the central side 5a of the cavity 5 when the elastic wave device 1 is fractured in a direction parallel to any one side of the device chip 2 which has a rectangular outline (for example, fractured along the left-right direction in Figure 1 / Figure 2), and at the same time, it is also curved to create a vertex 4a on the central side 5a of the cavity 5 when the elastic wave device 1 is fractured in a direction perpendicular to the aforementioned side (for example, fractured along the up-down direction in Figure 1 / Figures 3 and 4).

[0022] More specifically, the cover layer 4, which acts as a lid for one cavity 5, is curved such that the distance between it and one surface 2a of the device chip 2 gradually increases as it approaches the center 5a of the cavity 5, starting from the junction 4b with the protruding end 3a of the support layer 3, which acts as a wall for one cavity 5. In other words, the cover layer 4 located on the resonator 7 bulges outward from the cavity 5, that is, outward from the elastic wave device, and the outer surface of the cover layer 4 is a three-dimensional curved surface.

[0023] As shown in Figure 8, in many cases, the elastic 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 side by ultrasonic bonding or the like, and after this bonding, the elastic wave device 1 is sealed by a sealing resin layer 10b formed on the module substrate 10a. Since a gap S (see Figure 8) is formed between the elastic wave device 1 and the module substrate 10a by the bumps 9, this sealing resin layer 10b also penetrates between the cover layer 4 of the elastic wave device 1 and the module substrate 10a. For this reason, when this sealing resin layer 10b is formed, a force f (see Figure 8) is applied to the cover layer 4 in a direction that narrows the distance between the cover layer 4 and one surface 2a of the device chip 2. If the cover layer 4 comes into contact with one surface 2a of the device chip 2 or the resonator 7 within the cavity 5 due to the action of this force f, the function of the elastic wave device 1 will be impaired. In the elastic wave device 1 according to this embodiment, since the cover layer 4 is pre-curved as described above, the cover layer 4 can easily resist the force f, and even if it deforms, it can prevent displacement that would cause it to come into contact with one surface 2a of the device chip 2 or the resonator 7. This makes it possible to improve the yield of the module 10 which includes this elastic wave device 1.

[0024] In the illustrated example, the elastic wave device 1 comprises a plurality of cavities 5, and in each cavity 5, the cover layer 4 is curved such that the side of the device chip 2a facing inward is the curved side. This makes it possible to suppress deformation of the cover layer 4 caused by the force f in each of the plurality of cavities 5.

[0025] Furthermore, in the illustrated example, the elastic wave device 1 comprises a plurality of cavities 5, and at least one of the plurality of cavities 5 is a large 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 the direction perpendicular to the one surface 2a of the device chip 2 (see Figure 3). At the same time, at least one of the plurality of cavities 5 is a small 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 Figure 4). And, at least in the large cavity 5, the cover layer 4 is curved so that the side on which the resonator 7 is formed is on the curved side.

[0026] In the illustrated example, each of the multiple cavities 5 is configured to have one resonator 7 within it, and the distance 3b between opposing support layers 3 in the direction of elastic wave propagation x is increased, while the distance 3b between opposing support layers 3 in the direction perpendicular to this propagation direction x is decreased. In a plan view of the elastic wave device 1, each of the multiple cavities 5 has a length and width (see Figure 1). Although not shown in the illustration, there are also cases where two or more resonators 7 are located within a single cavity 5.

[0027] In the large cavity 5, the distance 3b between the opposing support layers 3 is large, so the amount of displacement when the cover layer 4 deforms due to the force f is large. At least in the large cavity 5, by curving the cover layer 4 as described above, the objective of the present invention, which is to improve the yield of the module 10 comprising the acoustic wave device 1, can be achieved. From another point of view, the present invention makes it easier to provide the acoustic wave device 1 with the large cavity 5 as described above. In the illustrated example, the cover layer 4 is also curved as described above in the small cavity 5, but depending on the magnitude of the force f, the cover layer 4 of the small cavity 5 may be flat, that is, formed parallel to one surface 2a of the device chip 2 (the outer shape of the cover layer 4 when it is flat is shown by a dotted line in Figure 4).

[0028] The cover layer 4 is preferably composed of a thermosetting resin planar material 4c with a thickness 4f of 15 to 35 μm. This is because 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 is greater than 35 μm, it becomes difficult to bend and deform the cover layer 4 during the baking process described later. It is preferable to use a planar material 4c that has a certain adhesive strength at room temperature and has the function of being able to remove unwanted parts through exposure and development in photolithography technology.

[0029] On the other hand, it is preferable that the support layer 3 be made of a synthetic resin that is easy to form on one surface 2a of the device chip 2 and that has good compatibility with the cover layer 4. The support layer 3 has a base portion 3d that is joined to one surface 2a of the device chip 2 and a protruding end portion 3a that is joined to the cover layer 4, and is formed to protrude from one surface 2a of the device chip 2 in a direction perpendicular to that surface 2a. 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 be equal to or greater than the thickness 4f of the cover layer 4.

[0031] The elastic wave device 1 described above can be manufactured appropriately and rationally as follows. Figure 7 shows the main parts of the manufacturing steps for the elastic wave device 1 according to this embodiment. Note that in Figure 7, for convenience, only a portion of the wafer before dicing is shown as the device chip 2.

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

[0033] Next, a support layer 3 is formed on one surface 2a of the device chip 2, in a region other than the region where the resonator 7 is formed (Step 2 / Figure omitted).

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

[0035] In the lamination process, a surface material 4c made of 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, a base film is prepared, which has a base film 4d on the upper surface and a cover film 4e on the lower surface of a planar material 4c that will become the cover layer 4 (Step 3-1 / Figure 7(a)). The planar material 4c is made of a thermosetting resin that has a certain adhesive strength at room temperature and has the function of being able to remove unwanted parts through exposure and development in photolithography technology. Next, peel off the cover film 4e from the original film (Step 3-2 / Figure 7(b)). Next, the lower surface of the planar material 4c is adhered to the protruding end 3a of the support layer 3, which is formed to surround the resonator 7 (Step 3-3 / Figure 7(c)). This forms a temporary cavity 5e 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, then adjacent cavities 5 By ensuring a large adhesive surface area between the protruding end 3a of the support layer 3, which solidifies the space between the layers, and the cover layer 4, the airtightness of the temporary cavity 5e can be maintained at a high level, including during the baking process. Next, the planar material 4c is exposed (Step 3-4 / Figure 7(d)). 11 This is a photomask. Next, peel off the base film 4d from the top surface of the planar material 4c (Step 3-5 / Figure 7(e)).

[0036] In the baking process, the workpiece w (intermediate product) that has undergone the lamination process is heated at 100°C to 120°C for 7 to 12 minutes (Step 3-6 / Figure 7(f)). The planar material 4c is configured to increase its plasticity at this temperature and not harden. For this reason, the temporary cavity 5 e Due to the volume expansion of the gas inside, the temporary cavity 5 e The cover layer 4, which is part of the planar body 4c that constitutes the large chamber cavity 5, can be curved as shown in Figure 7(g). b Then the deformation of the cover layer 4 is large, and the small room cavity 5 c In some cases, the deformation may be so small that it can be considered equivalent to having virtually no deformation at all.

[0037] Next, the unwanted portion is removed from the planar material 4c by developing (Step 3-7 / Figure 7(g)).

[0038] The curing process involves heating the developed workpiece at 150°C to 200°C for 45 to 90 minutes (Step 3-8 / Figure 7(h)). The planar material 4c is configured to harden at this temperature. As a result, the temporary cavity 5e becomes the cavity 5, and the curved shape of the cover layer 4 formed by the baking process is maintained.

[0039] Multiple elastic wave devices 1 are generated from the workpiece w by dicing after the curing process.

[0040] Naturally, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the objectives of the present invention. [Explanation of Symbols]

[0041] 1. Elastic wave device 2 device chips 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 Cavity Room 5d distance 5e Temporary Cavity 6 through holes 7, 7a, 7b resonator 7c IDT electrode 7d reflector 7e electrode finger 7F Bus Bar 8 Grand 9 Bump 10 modules 10a Module board 10b Sealing resin layer 10c electrode 11 Photomasks x propagation direction f force w work

Claims

1. Device chip and A resonator formed on one surface of the device chip, A support layer formed on one surface so as to surround the resonator, The device chip and the support layer are formed on the support layer and a cover layer is formed to form a plurality of cavities that hermetically seal the resonator, The support layer is designed so as not to have any portion that causes a difference in height relative to one surface of the device chip, The cover layer is a surface material made of thermosetting resin with a thickness of 15 to 35 μm, which increases plasticity but does not harden at temperatures of 100 to 120 degrees Celsius, and hardens at temperatures of 150 to 200 degrees Celsius. An elastic wave device comprising a cover layer on at least one of the cavities, curved such that the side where the resonator is formed faces inward.

2. The acoustic wave device according to claim 1, wherein in each cavity, the cover layer is curved such that the one side of the device chip is curved inward.

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