Elastic wave device

Abstract

To provide a novel structure capable of minimizing the hole width of a penetration hole for bump formation with a support layer without deteriorating the sealability of a functional element while securing a roof layer widely.SOLUTION: An elastic wave device includes a support layer 4 formed in a region excluding a formation region of a functional element 3 on one surface 2a of a device chip 2, a first roof layer 8 that forms an internal space 10 to hermetically seal the functional element 3 by working together with the device chip 2 and the support layer 4, a second roof layer 9 formed on the first roof layer 8, penetration holes 11 including a first hole part 12 that penetrates the support layer 4, a second hole part 13 that penetrates the first roof layer 8, and a third hole part 14 that penetrates the second roof layer 9, and a bump 6 formed inside the penetration holes 11. A formation region of the second hole part 13 does not overlap with a formation region of the internal space 10, and a formation region of the third hole part 14 overlaps with a formation region of the internal space 10.SELECTED DRAWING: Figure 4

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] There is a surface acoustic wave (SAW) device having a wafer level package (WLP) structure (see Patent Document 1).

[0003] 7 and 8 show the main part of an acoustic wave device having a WLP structure. In the figures, reference numeral 100 denotes a device chip, reference numeral 101 denotes a functional element including an IDT electrode, reference numeral 102 denotes a support layer (wall), reference numeral 103 denotes a roof layer (cover), and reference numeral 104 denotes a bump. The WLP structure acoustic wave device has an internal space 105 (cavity) formed on one side of the device chip 100 by the support layer 102 and the roof layer 103 made of synthetic resin, and the functional element 101 is positioned within this internal space 105. The bump 104 is formed by utilizing a through hole 106 penetrating the support layer 102 and the roof layer 103. The through hole 106 is formed so that a part of the wiring 107 connected to the functional element 101 is positioned at the bottom of the hole, thereby connecting the functional element 101 to the outside through the bump 104.

[0004] Here, in the roof layer 103, the hole width 106a (hole size) of the through hole 106 on a virtual straight line perpendicular to the hole axis of the through hole 106 needs to be at least 100 μm even at the location where the hole width 106a is smallest. If the hole width 106a is less than 100 μm, the filling of the bump constituent material, such as cream solder, into the through hole 106 is hindered. On the other hand, so long as the hole width 106a of the through-hole 106 in the roof layer 103 is ensured to be 100 μm or more, there is no particular problem even if the hole width 106b of the through-hole 106 in the support layer 102 is less than 100 μm. If the hole width 106b of the through hole 106 in the support layer 102 can be reduced without any problems, it becomes possible to increase the formation area of ​​the functional element 101 in the device chip 100. However, if the hole width 106b of the through hole 106 in the support layer 102 is simply reduced and the formation area of ​​the functional element 101 is increased accordingly, the through hole 106 in the roof layer 103 will communicate with the internal space 105, as shown in Fig. 9, and the sealing property of the functional element 101 will be impaired. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-217673 A Summary of the Invention [Problem to be solved by the invention]

[0006] The main problem that this invention aims to solve is to provide a new structure in this type of acoustic wave device that enables the hole width of the through hole for forming a bump to be kept wide in the roof layer while being as small as possible in the support layer without compromising the sealing property of the functional element. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an acoustic wave device comprising: a device chip having a functional element and wiring, the functional element including at least an IDT electrode on one surface; a support layer formed on the one surface in a region other than a region in which the functional element is formed; a first roof layer formed on the support layer and cooperating with the device chip and the support layer to form an internal space that hermetically seals the functional element; a second roof layer formed on the first roof layer; a through hole including a first hole portion penetrating the support layer, a second hole portion penetrating the first roof layer, and a third hole portion penetrating the second roof layer, the through hole having a bottom at which a part of the wiring is positioned; a bump formed in the through hole, Furthermore, when viewed from a direction perpendicular to the one surface of the device chip, the formation area of ​​the second hole does not overlap with the formation area of ​​the internal space, and the formation area of ​​the third hole overlaps with the formation area of ​​the internal space.

[0008] In one aspect of the present invention, an area of ​​a region where the third hole portion is formed is made larger than an area of ​​a region where the second hole portion is formed.

[0009] In one aspect of the present invention, a part of the internal space is located below a portion of the bump that is located within the third hole portion. Effect of the Invention

[0010] The acoustic wave device according to the present invention includes the first roof layer and the second roof layer, the first roof layer forms an internal space, the second roof layer forms a third hole portion constituting a through hole, and the formation area of ​​the third hole portion overlaps the formation area of ​​the internal space, so that the third hole portion can have a wide hole width so as not to impair the filling of the material constituting the bump into the through hole, while the first hole portion penetrating the support layer can have a hole width as small as possible without impairing the sealing of the functional element. This makes it possible to rationally increase the formation area of ​​the functional element on one surface of the device chip, thereby increasing the degree of freedom in designing the acoustic wave device. [Brief description of the drawings]

[0011] [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 taken along line AA in FIG. [Diagram 3] FIG. 3 is an enlarged view of the main part of FIG. [Figure 4] FIG. 4 is an enlarged view of the main part of FIG. [Diagram 5] FIG. 5 is a configuration diagram showing an example of a resonator formed on a device chip constituting the acoustic wave device. [Figure 6] FIG. 6 is a configuration diagram showing an example of a circuit formed on the device chip. [Figure 7] FIG. 7 is an enlarged plan view showing a configuration of a main portion of a conventional acoustic wave device. [Figure 8] FIG. 8 is an enlarged cross-sectional view showing a main portion of a conventional acoustic wave device. [Figure 9] FIG. 9 is an enlarged cross-sectional view of a main part of the study example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, exemplary embodiments of the present invention will be described with reference to Figures 1 to 6. An acoustic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication devices and the like.

[0013] The acoustic wave device 1 includes a device chip 2, a functional element 3, a support layer 4, a roof layer 5, and bumps 6 for external connection.

[0014] The device chip 2 has a function of propagating elastic waves. Typically, lithium tantalate or lithium niobate is used as a piezoelectric material in the device chip 2, and the device chip 2 may be configured by laminating sapphire, silicon, alumina, spinel, quartz crystal, glass, or the like on the piezoelectric material.

[0015] A functional element 3 and wiring 7 are formed on one surface 2a of the device chip 2, which has the function of propagating the elastic wave. At least one of the functional elements 3 is a resonator 3a. In the illustrated example, a plurality of resonators 3a are formed on one surface of the device chip 2. The functional element 3 and wiring 7 are made of a conductive metal film, and are typically formed on a wafer that will become the device chip 2 by using photolithography technology.

[0016] The support layer 4 is formed in a region of the one surface 2a of the device chip 2 excluding the region where the functional element 3 is formed. The support layer 4 is typically made of an insulating synthetic resin. Typically, the support layer 4 has an outer wall 4a formed along the edge 2c near the edge 2c where the one surface 2a of the device chip 2 and the side surface 2b on the thickness side come into contact with each other, and a partition wall 4b formed between the adjacent functional elements 3 inside the outer wall 4a. The outer wall 4a has a frame shape surrounding the region where the functional element 3 is formed, and the region where the functional element 3 is formed is surrounded by the outer wall 4a. The surface portion located inside the outer wall 4a on the one surface 2a of the device chip 2 is the surface portion that functions as the acoustic wave device 1. The thickness of the support layer 4 in the direction perpendicular to the one surface 2a of the device chip 2 is larger than the film thickness of the functional element 3. The support layer 4 is typically formed by laminating a film (not shown) that will become the support layer 4 on a wafer (not shown) that will become the device chip 2, and then patterning the film using photolithography technology.

[0017] The roof layer 5 is composed of a first roof layer 8 and a second roof layer 9 .

[0018] The first roof layer 8 is formed on the support layer 4 and cooperates with the device chip 2 and the support layer 4 to form an internal space 10 that hermetically seals the functional element 3. The first roof layer 8 is typically made of an insulating synthetic resin. An inner surface 8a of the first roof layer 8 facing the one surface 2a of the device chip 2 is fixed to the support layer 4 at the position where the support layer 4 is formed, and the internal space 10 is formed between the first roof layer 8 and the one surface 2a of the device chip 2 in the region where the functional element 3 is formed. The first roof layer 8 is typically formed by forming the support layer 4 on the wafer that will become the device chip 2, and then laminating a film (not shown) that will become the first roof layer 8 on this wafer and patterning it.

[0019] The second roof layer 9 is formed on the first roof layer 8. The second roof layer 9 is also typically made of an insulating synthetic resin. An inner surface 9a of the second roof layer 9 facing one surface 2a of the device chip 2 is fixed to the outer surface 8b of the first roof layer 8. The second roof layer 9 is typically formed by laminating the film that will become the first roof layer 8 on the wafer that will become the device chip 2, and then laminating and patterning a film (not shown) that will become the second roof layer 9 on this film.

[0020] The bumps 6 are formed in through holes 11 formed to penetrate the support layer 4 and the first and second roof layers 8 and 9 in an area other than the area where the functional element 3 is formed. In the illustrated example, the through holes 11 are formed in the four corners of the device chip 2, and the bumps 6 are formed in each of the through holes 11. The number and positions of the bumps 6, that is, the number and positions of the through holes 11, may be changed as necessary. As described below, the through hole 11 has a first hole portion 12, a second hole portion 13, and a third hole portion 14. A part of the wiring 7 is positioned at a hole bottom 11a of the through hole 11, and this part functions as a bump pad. The bumps 6 are formed by forming the through holes 11 in the support layer 4 and roof layer 5 formed as described above, typically by the patterning, filling the through holes 11 with a conductive material for the bumps 6, such as cream solder, and subjecting them to a heat treatment. One end of the bumps 6 is fixed to the wiring 7 located at the bottom 11a of the through holes 11, and the other end of the bumps 6 is located outside the outer surface 9b of the second roof layer 9. The functional element 3 can be connected to the outside through the bumps 6.

[0021] Typically, the device chip 2 is configured in the shape of a quadrangular (rectangular in the illustrated example) plate with a side measuring 0.5 to 1 mm and a thickness of 0.1 mm (100 μm) to 0.2 mm (200 μm). Typically, the functional element 3 is configured to have a film thickness of 0.1 to 0.5 μm. Typically, the support layer 4 is configured so that its thickness in the direction perpendicular to the surface 2a of the device chip 2 is 15 to 30 μm. Typically, the roof layer 5 is configured to have a thickness of 20 to 40 μm. The acoustic wave device 1 constructed from these components typically has a thickness of about 0.2 to 0.3 mm.

[0022] The acoustic wave device 1 has a square or rectangular outline when viewed from a direction perpendicular to the surface 2a of the device chip 2. That is, the acoustic wave device 1 has a flat hexahedral shape having two rectangular faces 1a and four side faces 1b extending between the two faces 1a. In each drawing, the thickness of each component of the acoustic wave device 1 is exaggerated to make the configuration of the device easier to understand.

[0023] 5 shows an example of the configuration of a resonator 3a as a functional element 3. The resonator 3a has an IDT electrode 3b and a reflector 3c formed to sandwich the IDT electrode 3b. The IDT electrode 3b is composed of an electrode pair, and each electrode pair is formed by connecting a plurality of electrode fingers 3d 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 3e. The reflector 3c is formed by connecting ends of a plurality of electrode fingers 3f arranged in parallel so that their length direction crosses the propagation direction x of the elastic wave with a bus bar 3g.

[0024] Fig. 6 shows the concept of an example of a circuit provided on one device chip 2 by the functional elements 3 and wiring 7. Reference numeral 3aa denotes resonators 3a connected in series between signal input / output terminals 15, reference numeral 3ab denotes resonators 3a connected in parallel between signal input / output terminals 15, and reference numeral 16 denotes ground. The number and arrangement of the resonators 3a can be changed as necessary. In other words, a ladder-type filter is configured by the circuit in Fig. 6.

[0025] The through hole 11 comprises a first hole portion 12 that penetrates the support layer 4, a second hole portion 13 that penetrates the first roof layer 8, and a third hole portion 14 that penetrates the second roof layer 9. A part of the wiring 7 is positioned at a hole bottom 11a of the through hole 11. The first hole portion 12 is connected to the second hole portion 13, and the second hole portion 13 is connected to the third hole portion 14. The third hole portion 14 serves as an entrance when filling the material constituting the bump 6. Since the third hole portion 14 and the first hole portion 12 are connected via the second hole portion 13, the material constituting the bump 6 filled in the through hole 11 using the third hole portion 14 as an entrance enters the first hole portion 12 through the second hole portion 13 and spreads throughout the entire through hole 11.

[0026] In the illustrated example, the hole widths (hole area) on imaginary straight lines L1, L2, L3 perpendicular to the hole axes 12a, 13a, 14a (see Figure 3) of the first to third hole portions 12, 13, 14 are configured so that the third hole portion 14 has the largest hole width, the first hole portion 12 has the smallest hole width, and the second hole portion 13 has a larger hole width than the first hole portion 12 but a smaller hole width than the third hole portion 14.

[0027] In addition, in the illustrated example, when the surface 2a of the device chip 2 is viewed from a direction perpendicular to the surface 2a, the third hole portion 14 and the second hole portion 13 have a rectangular hole shape, and the first hole portion 12 has a circular hole shape. One corner 14ba (the upper right corner in FIG. 3) of the four corners 14b of the third hole portion 14 is in the same position as one corner 13ba (the upper right corner in FIG. 3) of the four corners 13b of the second hole portion 13, and two adjacent sides 14c sandwiching the corner 13ba of the third hole portion 14 are aligned with two adjacent sides 13c sandwiching the corner 13ba of the second hole portion 13. The hole wall 14d of the third hole portion 14 and the hole wall 13d of the second hole portion 13 are located on the same plane at the corners 13ba, 14ba and the two sides 13c, 14c (see FIG. 3 and FIG. 4). An L-shaped support surface 17 consisting of the outer surface 8b of the first roof layer 8 is formed between a corner 14bb (the lower left corner in Figure 3) located opposite the corner 14ba of the third hole portion 14 across the hole axis 14a of the third hole portion 14, and two adjacent sides 14c sandwiching this corner 14bb, and a corner 13bb (the lower left corner in Figure 3) located opposite the corner 13ba of the second hole portion 13 across the hole axis 13a of the second hole portion 13, and two adjacent sides 13c sandwiching this corner 13bb. The first hole portion 12 is formed so as to leave a gap between it and the hole wall 13d of the second hole portion 13 at any position around its hole axis 12a, and an annular support surface 18 made of the support layer 4 is formed between the hole wall 13d of the second hole portion 13 and the first hole portion 12. In addition, in the illustrated example, the L-shaped support surface 17 formed between the third hole portion 14 and the second hole portion 13 is positioned on the central side of the device chip 2 in the through hole 11 (the side of the arrow y in Figure 3).

[0028] At the same time, when the acoustic wave device 1 is viewed in a direction perpendicular to the surface 2a of the device chip 2, the formation area of ​​the second hole portion 13 does not overlap with the formation area of ​​the internal space 10, and the formation area of ​​the third hole portion 14 overlaps with the formation area of ​​the internal space 10. In the illustrated example, a part of the formation area of ​​the internal space 10 is below the L-shaped support surface 17, but is not below the annular support surface 18 (see FIGS. 3 and 4).

[0029] That is, in the acoustic wave device 1 according to this embodiment, the first roof layer 8 forms the internal space 10, and the second roof layer 9 is formed with the third hole 14 constituting the through hole 11, and the formation area of ​​the third hole 14 is made to overlap the formation area of ​​the internal space 10. As a result, the hole width of the third hole 14 can be secured to be wide so as not to impair the filling ability of the material constituting the bump 6 into the through hole 11, while the hole width of the first hole 12 penetrating the support layer 4 can be made as small as possible without impairing the sealing ability of the functional element 3. As a result, the formation area of ​​the functional element 3 on the one surface 2a of the device chip 2 can be rationally increased, and the design freedom of the acoustic wave device 1 can be increased.

[0030] Specifically, the area of ​​the region where the third hole portion 14 is formed is larger than the area of ​​the region where the second hole portion 13 is formed.

[0031] Further, a part of the internal space 10 is positioned below the portion of the bump 6 that is positioned within the third hole portion 14 , that is, below the L-shaped support surface 17 .

[0032] Typically, the third hole 14 is formed so that the distance between a pair of sides 14c or hole walls 14d facing each other across the hole axis 14a is 100 μm or more. When the diameter of the first hole 12 is set to 50 μm, the second hole 13 is formed so that the distance between a pair of sides 13c or hole walls 13d facing each other across the hole axis 13a is less than 100 μm and more than 50 μm, for example, about 70 μm.

[0033] 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]

[0034] x Propagation direction L1, L2, L3 straight line 1. Acoustic Wave Devices 1a side 1b side 2. Device chip 2a one side 2b side 2c Edge 3. Functional elements 3a, 3aa, 3ab resonators 3b IDT electrode 3c reflector 3d electrode fingers 3e Busbar 3f electrode finger 3g busbar 4 Support layer 4a Exterior wall 4b Partition wall 5 Roof layer 6. Bump 7 Wiring 8 First roof layer 8a Inner surface 8b External surface 9 Second roof layer 9a Inner surface 9b External surface 10. Interior Space 11 Through hole 11a Hole bottom 12 1st hole 12a hole shaft 13 2nd hole 13a Hole shaft 13b, 13ba 13c side 13d hole wall 14 3rd hole 14a hole shaft 14b, 14ba, 14bb corner 14c side 14d hole wall 15 Input / output terminal 16 Grand 17, 18 Support surface

Claims

1. a device chip having a functional element including at least an IDT electrode and wiring on one surface thereof; a support layer formed on the one surface in a region other than a region in which the functional element is formed; a first roof layer formed on the support layer and cooperating with the device chip and the support layer to form an internal space that hermetically seals the functional element; a second roof layer formed on the first roof layer; a through hole including a first hole portion penetrating the support layer, a second hole portion penetrating the first roof layer, and a third hole portion penetrating the second roof layer, the through hole having a bottom at which a part of the wiring is positioned; a bump formed in the through hole, Furthermore, when viewed from a direction perpendicular to the one surface of the device chip, the formation area of ​​the second hole does not overlap with the formation area of ​​the internal space, and the formation area of ​​the third hole overlaps with the formation area of ​​the internal space.

2. The acoustic wave device according to claim 1 , wherein an area of ​​a region in which the third hole is formed is larger than an area of ​​a region in which the second hole is formed.

3. The acoustic wave device according to claim 1 , wherein a part of the internal space is positioned below a part of the bump that is positioned within the third hole portion.

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