Elastic wave device

Abstract

This elastic wave device is provided with: a plurality of functional elements; the thickness of the thick film wiring is greater than the thickness of the functional element; the thickness of the surrounding metal layer is equal to that of the thick film wiring; the top cover substrate is positioned on the thick film wiring and the surrounding metal layer and is supported by the thick film wiring and the surrounding metal layer, and the top cover substrate cooperates with the device chip and the surrounding metal layer to form a sealed space for hermetically sealing the functional element; a connection bump which is formed in a through hole penetrating through the device chip, and which has an inner end fixed to the thick film wiring and an outer end located on the outside of the other surface of the device chip; a heat dissipation layer; a heat dissipation bump; in a device chip, heat generated in a region where a functional element is formed can be transferred to a support substrate side by forming a shortest heat dissipation path through a heat dissipation layer and heat dissipation bumps formed thereon.

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] As shown in Patent Document 1 (JPWO2017098809A1, see FIG. 5), there is an elastic wave (Surface Acoustic Wave / SAW) device having a WLP (Wafer Level Package) structure.

[0003] In the device of Patent Document 1, a functional element, a support portion surrounding the formation region of the functional element, and a cover portion that cooperates with the support portion to form a sealed space for the functional element are provided on one surface of a piezoelectric substrate (device chip). The functional element is connected to the outside via a through electrode that penetrates the piezoelectric substrate.

[0004] Here, in such an elastic wave device, it is strongly required to improve heat dissipation. Summary of the Invention

[0005] The main problem to be solved by the present invention is how to provide an elastic wave device with a new structure that can reasonably improve the heat dissipation of the elastic wave device in such a WLP structure.

[0006] The present invention discloses an elastic wave device, comprising: a device chip having: a plurality of functional elements, the plurality of functional elements including at least IDT electrodes on one surface of the device chip; thick film wirings, the thickness of the thick film wirings being greater than the thickness of the functional elements; and a surrounding metal layer that surrounds the formation regions of the functional elements and the thick film wirings and has the same thickness as the thick film wirings; a top cover substrate that is located on and supported by the thick film wirings and the surrounding metal layer and cooperates with the device chip and the surrounding metal layer to form a sealed space for hermetically sealing the functional elements; connection bumps formed in through holes that penetrate the device chip and fixed to the inner ends of the thick film wirings and the outer ends located outside the other surface of the device chip; a heat dissipation layer formed on the other surface of the device chip; and heat dissipation bumps formed on the heat dissipation layer.

[0007] Further, the top cover substrate is made of high-resistance silicon, ceramic, or glass.

[0008] Further, the thickness of the device chip is less than the thickness of the top cover substrate.

[0009] Further, in a state where the elastic wave device is observed from a direction orthogonal to one surface and the other surface of the device chip, at least a part of the formation region of the heat dissipation layer is located directly above or directly below the formation region of the functional element.

[0010] Further, a part of the thick film wiring is integrated with the surrounding metal layer.

[0011] Further, bump pads are formed at four corners of the device chip through thick film wiring respectively.

[0012] Further, the lid substrate is joined to the thick film wiring and the surrounding metal layer by sandwiching a thin film layer made of an insulating material or a high-resistance material therebetween.

[0013] Further, the surface roughness of the surface of the thin film layer in contact with the lid substrate and the inner surface of the lid substrate in contact with the thin film layer is set to be 0.0001 nm or more and 0.5 nm or less.

[0014] Further, the through hole is configured such that the aperture diameter is the largest on the other surface side of the device chip, and gradually decreases toward the one surface side of the device chip.

[0015] Further, the heat dissipation layer is made of metal or a high heat dissipation resin; the high heat dissipation resin is an epoxy resin containing a filler or a phenolic resin containing a filler; the filler is silica, alumina or aluminum nitride.

[0016] According to the present invention, the elastic wave device can be mounted on the support substrate by using the connection bumps, and the other surface of the device chip faces the mounting surface of the support substrate. The heat generated in the formation region of the functional element in the device chip can be transferred to the support substrate side through the heat dissipation layer and the heat dissipation bumps formed thereon along the shortest heat dissipation path. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional structure diagram of an elastic wave device according to an embodiment of the present invention, showing a first embodiment in cross-section at the position of line A-A in Figure 2 is a cut end face structure diagram at the position of line B-B in

[0018] Figure 2 is Figure 1 is a cut end face structure diagram at the position of line B-B in

[0019] Figure 3 is a structure diagram showing an example of a resonator formed on a device chip constituting the first embodiment.

[0020] Figure 4 is a structure diagram showing an example of a circuit formed on the device chip of the first embodiment.

[0021] The main reference numerals are as follows: 1 - Elastic wave device, 1a - face, 1b - side face, 2 - device chip, 2a - one face, 2b - the other face, 2c - side face, 2d - outer edge, 2e - main face, 2f - through hole, 3 - functional element, 3a, 3aa, 3ab - resonator, 3b - IDT electrode, 3c - reflector, 3d - electrode finger, 3e - bus bar, 3f - electrode finger, 3g - bus bar, 4 - thick film wiring, 5 - surrounding metal layer, 6 - top cover substrate, 6a - inner surface, 6b - outer surface, 7 - connecting bump, 7a - inner end, 7b - outer end, 8 - heat dissipation layer, 9 - heat dissipation bump, 9a - base, 9b - protruding end, 10 - sealed space, 11 - circuit, 11a - signal input / output terminal, 12 - wiring, 13 - ground terminal, 14 - bump pad, 15 - thin film layer, P - support substrate, Pa - terminal, Pb - heat dissipation terminal, Pc - mounting surface, x - orthogonal direction, y - propagation direction, z - heat dissipation path. Specific embodiments Hereinafter, based on Figures 1 to 4 , typical embodiments of the present invention will be described. The elastic wave device 1 in this embodiment is suitable for use as a frequency filter or the like in a mobile communication device or the like.

[0023] The elastic wave device 1 includes: a device chip 2, a functional element 3, a thick film wiring 4, a surrounding metal layer 5, a top cover substrate 6, a connecting bump 7, a heat dissipation layer 8, and a heat dissipation bump 9.

[0024] The functional element 3 is formed on one face 2a of the device chip 2. In addition, the thick film wiring 4 and the surrounding metal layer 5 are formed on one face 2a of the device chip 2, and in the direction x orthogonal to one face 2a and the other face 2b of the device chip 2, the thickness of the thick film wiring 4 and the surrounding metal layer 5 is greater than the thickness of the functional element 3. The thicknesses of the thick film wiring 4 and the surrounding metal layer 5 are equal.

[0025] The surrounding metal layer 5 is formed at a position slightly inside the outer edge 2d of the device chip 2 where one face 2a of the device chip 2 is in contact with the side face 2c. The surrounding metal layer 5 is in a quadrilateral frame shape when observed in the direction x orthogonal to one face 2a and the other face 2b of the device chip 2. In one face 2a of the device chip 2, the inner region of the surrounding metal layer 5 serves as the main face 2e of the device chip 2 (the face that functions as the elastic wave device 1).

[0026] A plurality of functional elements 3 are formed on the main face 2e of the device chip 2.

[0027] The thick film wiring 4 is formed at a desired position such as between adjacent functional elements 3 in the main face 2e of the device chip 2. The thick film wiring 4 is connected to the functional element 3 via a thin film wiring (not shown) or the like.

[0028] The thick film wiring 4 is formed at a desired position of the main face 2e of the device chip 2, for example, between adjacent functional elements 3.

[0029] The top cover substrate 6 is located on the thick film wiring 4 and the surrounding metal layer 5, and is supported by the thick film wiring 4 and the surrounding metal layer 5 in such a manner that its inner surface 6a faces one face 2a of the device chip 2.

[0030] On one face 2a of the device chip 2, a sealed space 10 (cavity, hollow structure portion) is formed by the main face 2e of the device chip 2, the surrounding metal layer 5, and the top cover substrate 6, and a resonator 3a (described later) constituting the functional element 3 is disposed in the sealed space 10.

[0031] The thick film wiring 4 also functions as a spacer for supporting the top cover substrate 6 in the sealed space 10.

[0032] The heat dissipation layer 8 is formed on the other face 2b opposite to one face 2a of the device chip 2. The heat dissipation layer 8 is formed to cover at least a part of the other face 2b.

[0033] Typically, the device chip 2 is configured in a plate shape, and the plate shape is a quadrilateral (a rectangle in the illustrated example) with one side being 0.5 mm to 1 mm and a thickness of 0.02 mm (20 μm) or more and 0.1 mm (100 μm) or less.

[0034] In addition, typically, the functional element 3 is configured such that the thickness in the direction x orthogonal to one face 2a and the other face 2b of the device chip 2 (the height of the functional element 3 based on one face 2a of the device chip 2) is 0.1 μm to 0.5 μm.

[0035] In addition, typically, the thick film wiring 4 and the surrounding metal layer 5 are configured such that the thickness in the direction x orthogonal to one face 2a and the other face 2b of the device chip 2 is 3 μm to 6 μm.

[0036] In addition, typically, the top cover substrate 6 is configured to have a thickness of 100 μm to 150 μm.

[0037] In addition, typically, the heat dissipation layer 8 is configured to have a thickness of 1 μm to 30 μm.

[0038] Typically, the surface acoustic wave device 1 composed of these parts has a thickness of about 150 μm to 250 μm.

[0039] The elastic wave device 1 has a square or rectangular quadrilateral outline when viewed from the direction x orthogonal to one surface 2a and the other surface 2b of the device chip 2 above.

[0040] That is, the elastic wave device 1 is a flat hexahedron, having two surfaces 1a with a quadrilateral shape and four side surfaces 1b connecting between the two surfaces 1a.

[0041] In addition, in each figure, in order to easily understand the structure of the elastic wave device 1, the thicknesses of its constituent elements are exaggeratedly shown.

[0042] The device chip 2 has a function of propagating elastic waves. Typically, the device chip 2 uses lithium tantalate or lithium niobate as a piezoelectric body. Additionally, in other embodiments, the device chip 2 can be formed by laminating lithium tantalate or lithium niobate with sapphire, silicon, alumina, spinel, quartz, or glass, etc.

[0043] Figure 3 An example of the structure of the resonator 3a as the functional element 3 is shown. The resonator 3a has an IDT electrode 3b and a reflector 3c, and the reflector 3c is formed so as to sandwich the IDT electrode 3b. The IDT electrode 3b is composed of electrode pairs, and each electrode pair connects one end side of a plurality of electrode fingers 3d through a bus bar 3e. The plurality of electrode fingers 3d are arranged in parallel so that the length direction of the electrode fingers 3d intersects the propagation direction y of the elastic wave. The reflector 3c connects between the ends of a plurality of electrode fingers 3f through a bus bar 3g. The plurality of electrode fingers 3f are arranged in parallel so that the length direction of the electrode fingers 3f intersects the propagation direction y of the elastic wave.

[0044] Typically, the functional element 3 is composed of a conductive metal film formed by photolithography and etching.

[0045] As Figure 1 and Figure 2 shown, the thick film wiring 4 and the surrounding metal layer 5 are formed on one surface 2a of the device chip 2 above, and have a specified thickness that is larger than the functional element 3 at any position.

[0046] In the illustrated example, a part of the thick film wiring 4 is integrated with the surrounding metal layer 5, and the surrounding metal layer 5 functions as a part of the wiring 12 connected to the ground terminal 13. In the illustrated example, bump pads 14 are respectively formed at the four corners of the device chip 2 through the thick film wiring 4.

[0047] Typically, the thick film wiring 4 and the surrounding metal layer 5 are also composed of a conductive metal film formed by photolithography and etching.

[0048] Figure 4A conceptual example of a circuit 11 on a device chip 2 composed of a functional element 3, a thin-film wiring (not shown), and a thick-film wiring 4 is shown.

[0049] Reference numeral 3aa denotes a resonator 3a connected in series between signal input / output terminals 11a, reference numeral 3ab denotes a resonator 3a connected in parallel between signal input / output terminals 11a, and reference numeral 13 denotes a ground terminal. The number and arrangement of the resonators 3a are changed as needed. That is, the circuit 11 of Figure 4 constitutes a ladder filter.

[0050] The top cover substrate 6 has an inner surface 6a and an outer surface 6b that are substantially parallel to one surface 2a of the device chip 2. In the illustrated example, the top cover substrate 6 is plate-shaped and has substantially the same shape and size as the device chip 2. A gap corresponding to the thickness of the thick-film wiring 4 and the surrounding metal layer 5 is formed between the inner surface 6a of the top cover substrate 6 and one surface 2a of the device chip 2, and this gap is hermetically sealed by the top cover substrate 6 to form the sealed space 10.

[0051] The top cover substrate 6 is preferably made of high-resistance silicon, ceramic, or glass.

[0052] The top cover substrate 6 is fixed to the thick-film wiring 4 and the surrounding metal layer 5 by a known fixing method.

[0053] As described above, when the top cover substrate 6 is made of high-resistance silicon, ceramic, or glass, the top cover substrate 6 can be joined to the thick-film wiring 4 and the surrounding metal layer 5 by sandwiching a thin film layer 15 made of an insulating material or a high-resistance material therebetween.

[0054] Typically, the thin film layer 15 is formed on the thick-film wiring 4 and the surrounding metal layer 5 by sputtering.

[0055] Specifically, the surface roughness of the surface of the thin film layer 15 that contacts the top cover substrate 6 and the inner surface 6a of the top cover substrate 6 that contacts the thin film layer 15 is set to be not less than 0.0001 nm and not more than 0.5 nm in Ra. Thus, in the manufacturing process of the surface acoustic wave device 1, by pressing with a prescribed force in a state where an assembly substrate (not shown) serving as the top cover substrate 6 is laminated on one surface of a wafer (not shown) serving as the device chip 2, the thin film layer 15 can be directly joined to the assembly substrate serving as the top cover substrate 6.

[0056] The connection bump 7 is formed in a through hole 2f that penetrates the device chip 2, and in a direction x orthogonal to one surface 2a and the other surface 2b of the device chip 2, it has an inner end 7a fixed to the thick-film wiring 4 and an outer end 7b located outside the other surface 2b of the device chip 2 at the same time.

[0057] In the illustrated example, vias 2f are formed at the four corners of the device chip 2. The vias 2f place the above bump pads 14 at the bottom of the holes, and connection bumps 7 made of a conductive material are formed within the vias 2f. Typically, the above vias 2f are formed by dry etching. In the illustrated example, the vias 2f are configured such that the aperture is the largest on the other surface 2b side of the device chip 2 and gradually decreases toward the one surface 2a side of the device chip 2, so that the orifice on the one surface 2a side of the device chip 2 is blocked by the above bump pads 14. The connection bumps 7 fill the vias 2f with the conductive material without gaps and form hemispherical heads on the other surface 2b of the device chip 2.

[0058] The surface acoustic wave device 1 is mounted on a support substrate P such as a module substrate by using the outer ends 7b of the connection bumps 7. That is, the surface acoustic wave device 1 is mounted on the support substrate P by fixing the outer ends 7b of the connection bumps 7 to the terminals Pa formed on the support substrate P by ultrasonic welding or the like.

[0059] The heat dissipation layer 8 is made of a material having a high thermal conductivity and is made of a material capable of forming heat dissipation bumps 9.

[0060] Typically, the heat dissipation layer 8 is made of a metal or a high heat dissipation resin (high thermal conductivity resin). As the high heat dissipation resin, typically, a filler made of a material having a high thermal conductivity is used, and its content in the resin as the base material is controlled within the range of 70 wt% to 90 wt%. Typically, the filler is composed of granular bodies having a diameter of about 10 μm.

[0061] Specifically, as the high heat dissipation resin, an epoxy resin containing a filler or a phenolic resin containing a filler can be used. Typically, silica, alumina, or aluminum nitride can be used as the filler.

[0062] In addition, in a state where the surface acoustic wave device 1 is observed in the direction x orthogonal to the one surface 2a and the other surface 2b of the device chip 2, at least a part of the formation region of the heat dissipation layer 8 is located directly above or directly below the formation region of the functional element 3.

[0063] Typically, the heat dissipation layer 8 is formed by coating a resin as the heat dissipation layer 8 on the surface of the wafer (not shown) of the device chip 2 opposite to the surface on which the functional element 3 is formed during the manufacturing process of the surface acoustic wave device 1. Alternatively, during the manufacturing process of the surface acoustic wave device 1, a thin film made of a resin as the heat dissipation layer 8 is laminated on the surface of the wafer 13 of the chip 2 opposite to the surface on which the functional element 3 is formed, and the heat dissipation layer 8 is formed by patterning the thin film by etching or the like.

[0064] The bump 9 for heat dissipation is made of a material with a relatively high thermal conductivity. Typically, the bump 9 for heat dissipation is made of materials such as solder, Cu, Ni, etc. When the surface acoustic wave device 1 is mounted on the support substrate P using the connecting bump 7, the bump 9 for heat dissipation is formed to have a height that abuts against the support substrate P (refer to Figure 1 ).

[0065] In the illustrated example, the bump 9 for heat dissipation has a substantially circular cross-section along the direction of one surface 2a and the other surface 2b of the device chip 2 at any position in its protruding direction. In addition, the bump 9 for heat dissipation is formed to have a gradually decreasing cross-sectional area in the cross-section from the base 9a fixed to the heat dissipation layer 8 toward its protruding end 9b, presenting a dome shape.

[0066] In the illustrated example, the surface acoustic wave device 1 is mounted on the support substrate P by fixing the protruding end 9b of the bump 9 for heat dissipation to the heat dissipation terminal Pb formed on the support substrate P by ultrasonic welding or the like.

[0067] A heat dissipation layer 8 is provided between the bump 9 for heat dissipation and the other surface 2b of the device chip 2. In the illustrated example, the heat dissipation layer 8 covers the entire area directly below the formation area of the functional element 3 in the other surface 2b of the device chip 2 (refer to Figure 1 , Figure 2 ).

[0068] The surface acoustic wave device 1 having the above structure can be mounted on the support substrate P with the other surface of the device chip 2 facing the mounting surface Pc of the support substrate P using the connecting bump 7. The heat generated in the formation area of the functional element 3 in the device chip 2 can form the shortest heat dissipation path z (refer to Figure 1 ) through the heat dissipation layer 8 and the bump 9 for heat dissipation formed thereon and be transferred to the support substrate P side.

[0069] When the top cover substrate 6 is made of high-resistance silicon, ceramic, or glass, the rigidity of the surface acoustic wave device 1 can be effectively improved. As a result, the thickness of the device chip 2 can be reduced as much as possible, that is, it can be made thinner. That is, even if the thickness of the device chip 2 is reduced as much as possible, when the surface acoustic wave device 1 as a whole is mounted on the support substrate P together with other devices to form a module, it can have a certain tolerance to the molding pressure of the sealing resin formed on the support substrate P.

[0070] Specifically, in the manufacturing process of the surface acoustic wave device 1, from the state where a collective substrate (not shown) serving as the top cover substrate 6 is laminated on one surface of a wafer (not shown) serving as the device chip 2, the other surface side of the wafer can be ground without hindrance using the rigidity of the collective substrate, so that the wafer, that is, the device chip 2 of the finally produced surface acoustic wave device 1, can be appropriately thinned.

[0071] Specifically, it is one of the preferred ways to make the thickness of the above-mentioned device chip 2 smaller than the thickness of the above-mentioned top cover substrate 6.

[0072] As a result, it is possible to minimize the thickness of the device chip 2, which is part of the above-mentioned heat dissipation path z, thereby shortening the above-mentioned heat dissipation path z. Through this shortened heat dissipation path z, the heat dissipation efficiency can be reasonably improved. In addition, the formation of the through hole 2f of the above-mentioned connection bump 7 with respect to the device chip 2 also becomes easier.

[0073] In addition, of course, the present invention is not limited to the embodiments described above, and also includes all embodiments that can achieve the object of the present invention.

Claims

1. An elastic wave device, characterized in that: have: A device chip, the device chip having: a plurality of functional elements, the plurality of functional elements including at least an IDT electrode on one side of the device chip; Thick film wiring, the thickness of the thick film wiring is greater than the thickness of the functional element; and a surrounding metal layer, the surrounding metal layer surrounding the functional element and the formation area of ​​the thick film wiring and having a thickness equal to that of the thick film wiring; a top cover substrate, the top cover substrate being located on and supported by the thick film wiring and the surrounding metal layer, and cooperating with the device chip and the surrounding metal layer to form a sealed space for hermetically sealing the functional element; a connection bump formed in a through hole penetrating the device chip and fixed to an inner end of the thick film wiring and an outer end located outside the other surface of the device chip; A heat dissipation layer, the heat dissipation layer is formed on the other side of the device chip; A heat dissipation bump is formed on the heat dissipation layer.

2. The elastic wave device according to claim 1, characterized in that: The top cover substrate is made of high-resistance silicon, ceramic or glass.

3. The elastic wave device according to claim 2, characterized in that: The thickness of the device chip is smaller than the thickness of the top cover substrate.

4. The elastic wave device according to claim 1, characterized in that: When the elastic wave device is viewed from a direction perpendicular to one surface and the other surface of the device chip, at least a portion of a formation region of the heat dissipation layer is located directly above or directly below a formation region of the functional element.

5. The elastic wave device according to claim 1, characterized in that: A portion of the thick film wiring is integrated with a surrounding metal layer.

6. The elastic wave device according to claim 1, characterized in that: Bump pads are formed at the four corners of the device chip through thick film wiring.

7. The elastic wave device according to claim 1, characterized in that: The top cover substrate is bonded to the thick film wiring and the surrounding metal layer by sandwiching a thin film layer made of an insulating material or a high resistance material therebetween.

8. The elastic wave device according to claim 7, characterized in that: The surface roughness of the surface of the thin film layer in contact with the top cover substrate and the inner surface of the top cover substrate in contact with the thin film layer are both set to be 0.0001 nm or more and 0.5 nm or less.

9. The elastic wave device according to claim 1, characterized in that: The through hole is configured such that the aperture is the largest on the other side of the device chip and the aperture gradually decreases toward the one side close to the device chip.

10. The elastic wave device according to claim 1, wherein: The heat dissipation layer is made of metal or high heat dissipation resin; The high heat dissipation resin is an epoxy resin containing fillers or a phenolic resin containing fillers; the fillers are silicon dioxide, aluminum oxide or aluminum nitride.

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