Elastic wave device, and method for manufacturing an elastic wave device

Abstract

To mount an elastic wave device on a module substrate without using a bump and without forming a gap.SOLUTION: An elastic wave device includes a device chip 2 having one surface 2a on which a functional element 6 is formed, a support layer 3 formed so as to surround the formation area of the functional element 6, and a cover layer 4 formed on the support layer 3 to form a cavity 5 that hermetically seals the formation area. An external connection terminal 9 connected to the functional element 6 is located on a side surface 2c of the device chip 2. In a state where an external surface 4a of the cover layer 4 is brought into closed contact with a mounting surface 11a of a module substrate 11, the external connection terminal 9 and a connection terminal 11c, on a module substrate 11 side, formed outside an adhesion area 11b of the external surface 4a of the cover layer 4 on the mounting surface 11a can be connected using a conductive material 12.SELECTED DRAWING: Figure 5

Description

Technical Field

[0005]

[0001] This invention relates to an improvement of an elastic wave device suitable for use as a frequency filter or the like in mobile communication devices or the like.

Background Art

[0002] There is an elastic wave device D shown in FIG. 13 which is used as a frequency filter or the like in mobile communication devices or the like. In FIG. 13, 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 portion) for hermetically sealing 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] Such an elastic wave device D is mounted on a module substrate Ma together with other electronic devices by 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, and after this joining, the elastic wave device D is sealed by a sealing resin layer Mb formed on the module substrate Ma.

[0004] In the conventional elastic wave device shown in FIG. 13, a formation region of a bump pad 106 to which the bump 105 is joined on one surface of the device chip 100 is required. Further, since the conventional elastic wave device shown in FIG. 13 is joined to the module substrate Ma by the bump 105, it is mounted on the module substrate Ma in a state where a gap G of usually 30 to 80 μm is formed between the module substrate Ma.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The main problem that this invention aims to solve is to enable this type of elastic wave device to be mounted on a module substrate without the need to form bumps as described above, thereby eliminating the need to form bump pads on the device chip, and to enable this type of elastic wave device to be mounted on a module substrate without forming gaps as described above. [Means for solving the problem]

[0006] In order to achieve the above objectives, in this invention, from a first viewpoint, the elastic wave device is a device chip having a functional element with an IDT electrode formed on one surface, A support layer formed on one surface so as to surround the region where the functional element is formed, An elastic wave device comprising a cover layer formed on the support layer and cooperating with the device chip and the support layer to form a cavity that hermetically seals the formed region, The external connection terminals connected to the functional element are located on the side surface between the one surface of the device chip and the other surface located back-to-back with respect to the one surface. The external connection terminal and the connection terminal on the module board side, formed outside the contact area of ​​the outer surface of the cover layer on the mounting surface, can be connected by a conductive material while the outer surface of the cover layer is in close contact with the mounting surface of the module board.

[0007] One embodiment of the present invention is that the external connection terminal is formed of a metal film formed in a blank region located between the outer edge where the one surface and the side surface of the device chip are in contact and the support layer, and extending across the blank region and the side surface.

[0008] Furthermore, one embodiment of this invention is that the device chip has a rectangular plate shape, and blank regions are formed in all or part of its four corners.

[0009] Furthermore, in order to achieve the above objectives, in this invention, from a second viewpoint, the method for manufacturing an elastic wave device is described as follows: From a state in which the functional elements are formed in a plurality of rectangular regions on a wafer, each of which forms one side of the device chip, the support layer and the cover layer are formed such that the blank region is formed between the boundary line of the rectangular region and the support layer at a predetermined position, A bottomed groove is formed between adjacent rectangular regions. Next, a metal film that will serve as the external connection terminal is formed so as to extend across the blank region and the bottomed groove. Subsequently, the bottom of the groove is diced to generate elastic wave devices equal to the number of rectangular regions. [Effects of the Invention]

[0010] In the elastic wave device according to this invention, the outer surface of the cover layer is in close contact with the mounting surface of the module substrate, and the external connection terminals located on the side of the device chip and the connection terminals on the module substrate side can be connected by a conductive material. Firstly, this has the advantage of not requiring bump electrodes (bump pads) on one surface of the device chip, unlike conventional elastic wave devices. This contributes to miniaturization of the device chip. Secondly, the elastic wave device according to this invention has the advantage that, when mounted on a module substrate, it does not require bumps like conventional elastic wave devices, and the cover layer can be mounted on the module substrate in close contact with the mounting surface of the module substrate. After mounting the elastic wave device and other components to the mounting surface of the module substrate, molding (formation of a sealing resin layer) with synthetic resin is performed, but since the cover layer is in close contact with the mounting surface, even if the cover layer is made thin, deformation of the cover layer due to the injection pressure of the resin during molding does not occur. Therefore, the cover layer can be made as thin as possible. This contributes to the reduction in height of the elastic wave device, and consequently, to the reduction in height of the communication module and other components. Thirdly, since the elastic wave device according to this invention is mounted on a module substrate with the cover layer in close contact with the mounting surface, it is possible to effectively dissipate the heat generated by the operation of the elastic wave device from the area of ​​close contact to the module substrate. [Brief explanation of the drawing]

[0011] [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 diagram showing an example of a resonator formed on the device chip of the elastic wave device. [Figure 4] Figure 4 is a diagram showing an example of a circuit formed on the device chip of the elastic wave device. [Figure 5] Figure 5 is a cross-sectional view showing the elastic wave device mounted on a module substrate. [Figure 6] Figure 6 is a plan view showing one step in the manufacturing process of the elastic wave device. [Figure 7] Figure 7 is a plan view showing one step in the manufacturing process of the elastic wave device, following the process shown in Figure 6. [Figure 8] Figure 8 is an enlarged view of the main components of Figure 7. [Figure 9] Figure 9 is an enlarged plan view of a key part showing one step in the manufacturing process of the elastic wave device, following the process shown in Figure 7. [Figure 10] Figure 10 is a cross-sectional diagram showing one step in the manufacturing process of the elastic wave device, following the process shown in Figure 9. [Figure 11] Figure 11 is a cross-sectional diagram showing one step in the manufacturing process of the elastic wave device, following the process shown in Figure 10. [Figure 12] Figure 12 is a cross-sectional view showing one step in the manufacturing process of the elastic wave device, following the process shown in Figure 11. [Figure 13] FIG. 13 is a cross-sectional configuration diagram showing an example of a module including a conventional elastic wave device.

Mode for Carrying Out the Invention

[0012] Hereinafter, based on FIGS. 1 to 12, typical embodiments of this invention will be described. The elastic wave device 1 according to this embodiment is suitable for use as a frequency filter or the like in mobile communication devices or the like.

[0013] Such an elastic wave device 1 includes a device chip 2, function elements 6 such as an IDT electrode 6b formed on one surface 2a of the device chip 2, a support layer 3 (wall / Wall) formed so as to surround the function elements 6 on the one surface 2a, and a cover layer 4 (roof / Roof) formed on the support layer 3 and forming a cavity 5 (internal space, hollow structure portion) that cooperates with the device chip 2 and the support layer 3 to hermetically seal the function elements 6.

[0014] Typically, the device chip 2 is configured to have a rectangular (rectangular in the illustrated example) plate shape with one side being 0.5 to 1 mm and a thickness being 0.15 to 0.2 mm. Also, typically, the support layer 3 is configured such that the thickness in a direction orthogonal to the one surface 2a of the device chip 2 (the height of the support layer 3 with respect to the one surface 2a of the device chip 2) is 10 to 30 μm. Also, typically, the cover layer 4 is configured to have a thickness of 15 to 35 μm. The elastic wave device 1 composed of these typically has a thickness of about 0.25 to 0.35 mm.

[0015] Figure 2 shows the cross-sectional structure of the elastic wave device. In the figure, reference numeral 6 denotes the functional element, reference numeral 5 denotes the cavity, reference numeral 3 denotes the support layer, reference numeral 4 denotes the cover layer, and reference numeral 7 denotes the wiring connected to the functional element and which together with the functional element constitutes the circuit described later.

[0016] Multiple functional elements 6 are formed on one surface 2a of the device chip 2. Each formation region of the functional element 6 on one surface 2a of the device chip 2 is surrounded by a support layer 3 and covered by a cover layer 4 formed on the support layer 3, so that the elastic wave device 1 has multiple cavities 5. The support layer 3 and the cover layer 4 are composed of an insulating material, typically a synthetic resin.

[0017] Device chip 2 has the function of propagating elastic waves. Typically, lithium tantalate or lithium niobate is used for device chip 2, and it may also be constructed by layering these materials with sapphire, silicon, alumina, spinel, quartz, or glass.

[0018] Figure 3 shows a resonator 6a as an example of a functional element 6. The resonator 6a has an IDT electrode 6b and a reflector 6e formed so as to sandwich the IDT electrode 6b. The IDT electrode 6b consists of electrode pairs, and each electrode pair is formed by connecting multiple electrode fingers 6c, which are arranged in parallel so that their length direction intersects the propagation direction x of the elastic wave, with a busbar 6d at one end of each pair. The reflector 6e is formed by connecting the ends of multiple electrode fingers 6f, which are arranged in parallel so that their length direction intersects the propagation direction x of the elastic wave, with a busbar 6g. Such a functional element 6 is typically composed of a conductive metal film formed by photolithography.

[0019] Figure 4 shows a conceptual example of a circuit that can be provided on a single device chip 2. Reference numeral 6aa indicates a resonator 6a connected in series between input / output ports (e.g., the external output terminal 9 described later), reference numeral 6ab indicates a resonator 6a connected in parallel between input / output ports, and reference numeral 8 indicates ground. The number and arrangement of functional elements 6 can be changed as needed. In other words, the circuit in Figure 4 constitutes a ladder-type filter. The wiring 7 that constitutes such a circuit is also typically made of a conductive metal film formed by photolithography.

[0020] In the elastic wave device 1 according to this embodiment, an external connection terminal 9, which is electrically connected to the functional element 6 via the wiring 7, is located on the side surface 2c between the one surface 2a of the device chip 2 and the other surface 2b which is back-to-back with respect to the one surface 2a.

[0021] In this embodiment, the external connection terminal 9 is formed by a metal film 9a that extends across the one surface 2a and the side surface 2c of the blank region 10 (an area on one surface 2a of the device chip 2 where the support layer 3 and the cover layer 4 are not formed) located between the outer edge 2d where the one surface 2a and the side surface 2c of the device chip 2 are in contact and the support layer 3.

[0022] In the illustrated example, one surface 2a of the device chip 2 is generally covered by the support layer 3, except for the area where the functional element 6 is formed. In addition, in the illustrated example, four blank areas 10 are formed on the outer edge 2d side of one surface 2a of the device chip 2, where one surface 2a of the device chip 2 is not covered by the support layer 3. The cover layer 4 is also not formed in these blank areas 10.

[0023] In the illustrated example, the device chip 2 has a rectangular plate shape, and the blank regions 10 are formed in parts of its four corners 2e. Although not shown in the illustration, the blank regions 10 may be formed in all four corners 2e. In the illustrated example, blank regions 10 are formed in three of the four corners 2e of the device chip 2.

[0024] In the blank region 10, the first outer surface 3a, which is substantially parallel to the outer edge 2d of the device chip 2 in the blank region 10 and is aligned with the thickness direction of the support layer 3, is located closer to the center 2f (see Figure 1) of the device chip 2 than the outer edge 2d of the device chip 2, and a gap is formed between the first outer surface 3a and the outer edge 2d. In addition, at two terminals 10a of the blank region 10 in a direction circumferential to the center 2f of the device chip 2, a second outer surface 3b is formed, which is substantially perpendicular to the first outer surface 3a and is aligned with the thickness direction of the support layer 3. The area enclosed by this first outer surface 3a, the two second outer surfaces 3b, and the outer edge 2d of the device chip 2 constitutes the blank region 10.

[0025] In a view of the elastic wave device 1 from a direction perpendicular to the one surface 2a of the device chip 2 (Figure 1), the blank region 10 formed at the corner 2e of the device chip 2 is bent at a right angle at the corner 2g of the device chip 2, and is L-shaped, with the space between this corner 2g and the two second outer surfaces 3b aligned with the side 2h of the device chip 2. In the illustrated example, a linear blank region 10 is formed along the edge 2h of the device chip 2 near the corner 2e of the device chip 2 where no blank region 10 is formed (the lower left blank region 10 in Figure 1).

[0026] In the blank region 10, the wiring 7 extends to the area between the first outer surface 3a of the support layer 3 and the outer edge 2d of the device chip 2. In other words, a portion 7a of the wiring 7 is located in the blank region 10.

[0027] The external connection terminal 9 is formed to extend across the blank region 10 and the side surface 2c, covering a portion 7a of the wiring 7 located in the blank region 10. In the illustrated example, the external connection terminal 9 covers the entire blank region 10 and also covers the side surface 2c of the device chip 2 in a range slightly closer to the side surface 2a than the middle of the thickness direction 2i (see Figure 2) of the device chip 2 directly below the blank region 10.

[0028] In the illustrated example, there are four blank areas 10. So In each of these, an external connection terminal 9 is formed as described above.

[0029] In this embodiment, with the outer surface 4a of the cover layer 4 in close contact with the mounting surface 11a of the module substrate 11, the external connection terminal 9 and the connection terminal 11c on the module substrate 11 side, which is formed outside the contact area 11b of the outer surface 4a of the cover layer 4 on the mounting surface 11a, can be connected by the conductive material 12 (Figure 5).

[0030] Specifically, the elastic wave device 1 described above, along with one or more other devices, is mounted on a module substrate 11 that forms a communication module such as a mobile communication device. The elastic wave device 1 is electrically connected to the module substrate 11 by connecting the external connection terminal 9 to the connection terminal 11c on the module substrate 11 side via a conductive material 12 such as solder, while the outer surface 4a of the cover layer 4 is in close contact with the mounting surface 11a. By providing the outer surface 4a of the cover layer 4 with an adhesive function to the mounting surface 11a of the module substrate 11, stable adhesion between the two can be ensured. This adhesive function can be achieved by surface processing that gives the outer surface 4a of the cover layer 4 weak adhesiveness, or by constructing the cover layer 4 from an adhesive material so that the outer surface 4a of the cover layer 4 has weak adhesiveness.

[0031] In the blank region 10, the wiring 7 is connected to the external connection terminal 9 located on the side surface 2c of the device chip 2, which covers the side surface 2c. The elastic wave device 1 is electrically connected to the module substrate 11 side by a conductive material 12 formed on the outside of this side surface 2c. In other words, the elastic wave device 1 and module substrate 11 according to this embodiment can be mounted on the module substrate 11 with the cover layer 4 in close contact with the mounting surface 11a by utilizing the external connection terminal 9 located on the side surface 2c of the device chip 2. The external connection terminal 9 only needs to be connected to the wiring 7 in the blank area 10, and the width of the blank area 10, that is, the distance between the first outer surface 3a of the support layer 3 and the outer edge 2d of the device chip 2, can be made as small as possible. As a result, the elastic wave device 1 according to this embodiment has the advantage, firstly, that it does not require an electrode for bumps (bump pad) on one surface 2a of the device chip 2, unlike the conventional elastic wave device 1 (Figure 13). This contributes to miniaturization of the device chip 2. Secondly, when mounting to the module substrate 11, it has the advantage of being able to be mounted to the module substrate 11 with the cover layer 4 in close contact with the mounting surface 11a, without requiring bumps like those of the conventional elastic wave device 1 (Figure 13). Although the mounting surface 11a of the module substrate 11 is molded with synthetic resin after mounting the elastic wave device 1, the cover layer 4 is in close contact with the mounting surface 11a, so even if the cover layer 4 is made thin, deformation of the cover layer 4 due to the injection pressure of the resin during this molding does not occur. Therefore, the cover layer 4 can be made as thin as possible. This contributes to the reduction in height of the elastic wave device 1, and consequently, to the reduction in height of the communication module, etc. Thirdly, since the elastic wave device 1 according to this embodiment is mounted on the module substrate 11 with the cover layer 4 in close contact with the mounting surface 11a, it is possible to effectively dissipate the heat generated by the operation of the elastic wave device 1 from the area of ​​close contact towards the module substrate 11.

[0032] The elastic wave device 11 described above can be manufactured appropriately and rationally as follows. The main parts of the manufacturing steps for the elastic wave device 11 according to this embodiment are shown in Figures 6 to 12.

[0033] First, the functional elements 6 and wiring 7 are formed in multiple rectangular regions 14 (see Figure 6) on the wafer 13, each of which will become the device chip 2 (Step 1 / Figures 7 and 8). Typically, multiple functional elements 6 are formed in one rectangular region 14. In Figure 7, only a portion of the wiring 7 is schematically shown. The size of the rectangular region 14 is set as needed. The dashed lines in Figure 6 are hypothetical boundaries shown to make it easier to understand the boundaries of the set rectangular region 14. Gaps 15 are formed between adjacent rectangular regions 14, where the bottomed grooves 16 described later are formed. These gaps 15 are conceived as a grid.

[0034] Next, the support layer 3 and the cover layer 4 are formed in the rectangular region 14, and the blank region 10 is formed between the boundary line and the support layer 3 at a predetermined position (Step 2 / Figure 9). In the illustrated example, four blank regions 10 are formed in one rectangular region 14. Wiring 7 extends into the blank regions 10 as described above (in Figure 9, the cover layer 4 is not shown. Also, hatching is applied to a part 7a of the wiring 7 located in the blank region 10).

[0035] Next, closed-bottom trenches 16 are formed between adjacent rectangular regions 14 (Step 3 / Figure 10). The closed-bottom trenches 16 are formed within the gaps 15 and form a grid. The closed-bottom trenches 16 are typically formed by laser processing or etching.

[0036] Next, a conductive metal film 9a, which will become the external connection terminal 9, is formed extending across the blank region 10 and the bottomed groove 16 (Step 4 / Figure 11). The metal film 9a is typically formed by vapor deposition, sputtering, or plating.

[0037] Next, the bottom of the closed groove 16 is diced to generate a number of elastic wave devices 1 equal to a fraction of the rectangular region 14 (Step 5 / Figure 12). Dicing is performed along the bottomed groove 16, leaving a gap between the bottomed groove 16 and the left and right groove walls. The diced portion is indicated by reference numeral 17 in Figure 12. This dicing separates the elastic wave device 1 from the wafer 13 in increments of the rectangular region 14. The side surface 2c of the elastic wave device 1 generated in this way consists of a stepped surface 2ca, which was the bottom of the bottomed groove 16, an upper vertical surface 2cb located between this stepped surface 2ca and the one surface 2a, and a lower vertical surface 2cc located between this stepped surface 2ca and the other surface 2b, at any point around the center 2f of the elastic wave device 1. The metal film 9a is formed over the portion in the blank region 10 of the one surface 2a, the upper vertical surface 2cb, and the stepped surface 2ca.

[0038] 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]

[0039] 1. Elastic wave device 2 device chips 2a one side 2b Other side 2c side 2ca step surface 2cb upper vertical plane 2cc lower vertical surface 2d outer edge 2e corner 2f center 2g square 2h side 2i Thickness direction 3 Support layer 3a First outer surface 3b Second outer surface 4. Cover layer 4a Exterior 5 Cavity 6 Functional elements 6a, 6aa, 6ab resonator 6b IDT electrode 6c electrode finger 6d busbar 6e reflector 6f electrode finger 6g Bus Bar 7 Wiring 7a Part of the wiring 8 Grand 9. External connection terminals 9a Metal film 10 Blank areas 10a terminal 11 Module board 11a Implementation side 11b Close contact area 11c connector 12 Conductive materials 13 wafers 14 Rectangular area 15 gaps 16 Bottomed groove x propagation direction

Claims

1. A device chip having a functional element including an IDT electrode formed on one surface, A support layer formed on one surface so as to surround the region where the functional element is formed, An elastic wave device comprising a cover layer formed on the support layer and cooperating with the device chip and the support layer to form a cavity that hermetically seals the formed region, An elastic wave device wherein an external connection terminal connected to the functional element is positioned on the side surface between one surface of the device chip and another surface located back-to-back with respect to the first surface, and the external connection terminal and a connection terminal on the module substrate side formed outside the contact area of ​​the outer surface of the cover layer on the mounting surface can be connected by a conductive material while the outer surface of the cover layer is in close contact with the mounting surface of the module substrate.

2. The elastic wave device according to claim 1, wherein the external connection terminal is formed of a metal film formed to extend between the blank region and the side surface, in a blank region located between the outer edge where the one surface and the side surface are in contact and the support layer on one surface of the device chip.

3. The elastic wave device according to claim 2, wherein the device chip has a rectangular plate shape and blank regions are formed on all or part of its four corners.

4. From a state in which the functional elements are formed in a plurality of rectangular regions on a wafer, each of which forms one side of the device chip, the support layer and the cover layer are formed such that the blank region is formed between the boundary line of the rectangular region and the support layer at a predetermined position, A bottomed groove is formed between adjacent rectangular regions. Next, a metal film that will serve as the external connection terminal is formed so as to extend across the blank region and the bottomed groove. The method for manufacturing an elastic wave device according to claim 2 or 3, wherein the bottom of the closed groove is subsequently diced to generate the elastic wave device for a number of the rectangular regions.

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