Elastic wave device

Abstract

To make an elastic wave device with a wafer level package (WLP) structure have a configuration in which separation at a fastening interface between a device chip and a wall body due to heat is suppressed, for example.SOLUTION: A sealing body 5 is a group of two or more sealing parts 5a that are split in a length direction x of a functional surface 2a of a device chip 2, following a virtual line L extending between two sides 2ca along the length direction x. Each sealing part 5a is formed of three elements: a wall body 5b, a roof body 5c that is supported by the wall part 5b, and the functional surface 2a for surrounding a formation region of a resonator 3, and the inside thereof is a sealing space 8 for the resonator 3. A groove-shaped gap 7 is formed between the wall bodies 5b of the adjacent sealing parts 5a, making the wall bodies 5b of the adjacent sealing parts 5a not in contact with each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] An acoustic wave device with a WLP (Wafer Level Package) structure has the structure shown in Figures 10 to 12. In the figures, reference numeral 100 denotes a device chip having at least one surface made of a piezoelectric material, reference numeral 101 denotes a resonator made of a metal film formed on the surface of the device chip 100, reference numeral 102 denotes a resin wall body surrounding the formation region of the resonator 101, reference numeral 103 denotes a resin roof body formed on the wall body 102, reference numeral 104 denotes wiring within a via, and reference numeral 105 denotes a bump.

[0003] The device chip 100, the wall body 102, and the roof body 103 form a sealed space 106 for the resonator 101 within the acoustic wave device. In the manufacturing process of an acoustic wave device, heat treatment is often performed in the steps of forming the wall body 102, the roof body 103, the bumps 105, and the like. Additionally, acoustic wave devices generate heat during operation. On the other hand, the inorganic material that constitutes the device chip 100 and the organic material that constitutes the wall body 102 have significantly different thermal expansion coefficients.

[0004] Therefore, during the manufacturing process and in the operating state, heat tends to cause peeling (partial separation of the two) at the bonding interface 107 (see FIG. 11) between the device chip 100 and the wall body 102. Heat also tends to cause warping of the acoustic wave device. In recent years, it has become common for a single device chip 100 to have multiple functions, and the size of the device chip 100 has increased. However, this increase in size increases the tendency for peeling and warping due to the heat. Summary of the Invention [Problem to be solved by the invention]

[0005] The main problem that this invention aims to solve is to rationally provide an elastic wave device with such a WLP structure with a structure that minimizes peeling at the bonding interface between the device chip and the wall body and warping of the elastic wave device due to heat. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides an acoustic wave device configured such that a region of a functional surface of a device chip other than a region near an edge where the functional surface and a side surface of the device chip are in contact is covered with a sealing body, the device chip has a rectangular contour of the functional surface when viewed in a direction perpendicular to the functional surface; The sealing body is an assembly of two or more sealing portions divided in the longitudinal direction based on a virtual line segment extending between two sides along the longitudinal direction of the functional surface, and each of the sealing portions is composed of three elements: a wall body formed so as to surround a region where a resonator including an IDT electrode is formed on the functional surface; a roof body supported on the wall body with a gap between the wall body and the functional surface; and the functional surface, and the interior of the sealing portion is a sealing space for the resonator; A groove-like gap following the imaginary line segment is formed between the wall bodies of the sealing parts adjacent to each other across the imaginary line segment, so that the wall bodies of the adjacent sealing parts are not in contact with each other.

[0007] In one aspect of the present invention, the groove-like gap is formed so as to follow a straight line, which is an imaginary line segment, extending between two sides along the length direction of the functional surface.

[0008] Furthermore, one aspect of the present invention is to form the groove-like gap so as to follow the imaginary line segment that spans between two sides along the length direction of the functional surface and has a bent portion.

[0009] Furthermore, one aspect of the present invention is to form via wiring in each of the sealing portions, the via penetrating the roof body and the wall body, with one end connected to wiring formed on the functional surface and the other end connected to a bump formed on the roof body.

[0010] Further, a communication wiring is positioned on the functional surface of the groove-shaped gap, connecting a wiring formed in the sealed space of one of the sealing portions adjacent to each other across the groove-shaped gap with a wiring formed in the sealed space of the other sealing portion, and In one aspect of the present invention, the cross-sectional contour shape of the interconnection along the direction in which the groove-like gaps continue is made trapezoidal, with the width of the interconnection gradually increasing as it approaches the functional surface. [Effects of the Invention]

[0011] According to this invention, the sealing body, which covers substantially the entire functional surface of the device chip, is divided into two or more parts via the groove-like gap in the longitudinal direction of the rectangular functional surface, where large dimensional differences occur during thermal expansion. This minimizes peeling at the bonding interface between the device chip and the wall body and warping of the acoustic wave device due to heat. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view showing the configuration of an acoustic wave device (first example) according to an embodiment of the present invention. [Figure 2]FIG. 2 is a side view of the first example. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a diagram showing an example of a configuration of a resonator formed on the functional surface of the device chip constituting the first example. [Figure 5] FIG. 5 is a configuration diagram showing an example of a circuit formed on the functional surface of the device chip constituting the first example. [Figure 6] FIG. 6 is a perspective view of the main part of the first example. [Figure 7] FIG. 7 is a plan view of an acoustic wave device (second example) according to an embodiment of the present invention. [Figure 8] FIG. 8 is a side view of the second example. [Figure 9] FIG. 9 is a cross-sectional view taken along line BB in FIG. [Figure 10] FIG. 10 is a plan view showing the configuration of a conventional acoustic wave device. [Figure 11] FIG. 11 is a side view of a conventional acoustic wave device. [Figure 12] FIG. 12 is a cross-sectional view taken along line CC in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Exemplary embodiments of the present invention will now be described with reference to Figures 1 to 9. An acoustic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication devices and the like.

[0014] The acoustic wave device 1 includes a device chip 2, a resonator 3 and wiring 4 (see FIG. 5) including an IDT electrode 3a formed on a functional surface 2a of the device chip 2, and a sealing body 5 formed on the functional surface 2a. Although not shown, the wiring 4 is formed so as to connect the resonators 3 to each other and to connect the resonators 3 to via wiring 11, which will be described later.

[0015] As shown in Figure 1, the sealing body 5 substantially covers the area of ​​the functional surface 2a of one device chip 2 other than the vicinity of the edge 2c where the functional surface 2a and the side surface 2b (the surface on the thickness side of the device chip 2) of the device chip 2 meet, except for the location where the groove-like gap 7 described below is formed.

[0016] Typically, the device chip 2 is configured to have a rectangular plate shape with a side of 1 to 2 mm and a thickness of 0.15 to 0.2 mm. Therefore, when the device chip 2 is viewed from a direction perpendicular to the functional surface 2 a, the outline of the functional surface 2 a is rectangular.

[0017] A margin 6 of typically 10 to 40 μm is formed between the sealing body 5 and an edge 2c where the functional surface 2a and the side surface 2b of the device chip 2 meet. This margin 6 is required when, after forming the resonators 3 and wiring 4 and forming the sealing body 5 on a wafer (not shown) that becomes the device chip 2 in each region that becomes each acoustic wave device 1, the wafer is diced into each of the regions to produce a plurality of acoustic wave devices 1 from the wafer. Such margins 6 are formed along each of the four sides 2c of the functional surface 2a.

[0018] As shown in Figures 1 and 2, the sealing body 5 is an assembly of two or more sealing portions divided in the longitudinal direction x based on a virtual line segment L extending between two sides 2ca along the longitudinal direction x of the functional surface 2a. In the illustrated example, the sealing body 5 is an assembly of two sealing portions 5a. A groove-like gap 7, which will be described later, is formed between the two sealing portions 5a. The functional surface 2a is covered by the sealing body 5 except for the area where the groove-like gap 7 is formed and the margin 6. The acoustic wave device 1 is configured such that the sealing body 5 covers 70 to 90% of the area of ​​the functional surface 2a. Although not shown in the drawings, the sealing body 5 may be an assembly of any number of sealing portions 5a, such as three or more. For example, if the sealing body 5 is made up of three sealing portions 5a, the groove-like gap 7 will be formed in two places.

[0019] 1 to 3, each of the sealing portions 5a is composed of three elements: a wall body 5b formed so as to surround the formation region of the resonator 3, which is configured to include the IDT electrode 3a on the functional surface 2a; a roof body 5c supported on the wall body 5b with a gap between it and the functional surface 2a; and the functional surface 2a. The interior of the sealing portion 5a forms a sealing space 8 for the resonator 3.

[0020] Typically, the resonator 3 and the wiring 4 are made of a metal film having a thickness of 0.1 to 5 μm in the direction perpendicular to the functional surface 2 a of the device chip 2 . Furthermore, the wall body 5b is typically made of an insulating synthetic resin and is configured to have a thickness in a direction perpendicular to the functional surface 2a of the device chip 2 (the height of the wall body 5b based on the functional surface 2a) of 10 to 30 μm. The roof body 5c is typically made of insulating synthetic resin and has a thickness of 15 to 35 μm. The acoustic wave device 1 configured in this manner typically has a thickness of about 0.25 to 0.35 mm. In each drawing, the thickness of the components of the acoustic wave device 1 is exaggerated to make it easier to understand the configuration of the device.

[0021] A plurality of resonators 3 are formed on the functional surface 2a. The formation area of ​​each resonator 3 on the functional surface 2a is surrounded by a wall body 5b and is covered with a roof body 5c formed on the wall body 5b, so that the acoustic wave device 1 has a plurality of sealed spaces 8.

[0022] The device chip 2 has the function of propagating elastic waves. The surface of the device chip 2 that has the function of propagating elastic waves is the functional surface 2a. The device chip 2 typically uses lithium tantalate or lithium niobate as a piezoelectric material, and the device chip 2 may also be configured by laminating sapphire, silicon, alumina, spinel, quartz, glass, or the like on top of these.

[0023] An example of a resonator 3 is shown in Figure 4. The resonator 3 has an IDT electrode 3a and a reflector 3b formed on either side of the IDT electrode 3a. The IDT electrode 3a consists of an electrode pair, and each electrode pair has multiple electrode fingers 3c arranged in parallel so that their length direction intersects the propagation direction y of the acoustic wave, and each electrode pair has one end connected to the other by a busbar 3d. The reflector 3b has multiple electrode fingers 3e arranged in parallel so that their length direction intersects the propagation direction y of the acoustic wave, and each electrode finger 3c has one end connected to the other by a busbar 3f.

[0024] Figure 5 shows the concept of an example of a circuit 9 provided on one device chip 2. Reference numeral 30 denotes resonators 3 connected in series between input and output ports 9a, reference numeral 31 denotes resonators 3 connected in parallel, and reference numeral 9b denotes a port connected to ground. The number and arrangement of resonators 3 can be changed as needed. In the example shown in Figure 5, a ladder-type filter is configured. 5, one circuit 9 is formed on the functional surface 2a of the device chip 2, and a part of this circuit 9 (the right side in FIG. 5) is covered by one of the two sealing portions 5a, and the remaining part of this circuit 9 (the left side in FIG. 5) is covered by the other of the two sealing portions 5a. A connecting wiring 4a, which will be described later, is located between the two sealing portions 5a.

[0025] The resonators 3, wiring 4, and interconnecting wiring 4a are typically formed on the functional surface 2a by a conductive metal film formed on a wafer that will become the device chip 2 by photolithography and etching.

[0026] Furthermore, a groove-shaped gap 7 is formed between the wall bodies 5b of the adjacent sealing portions 5a on either side of the imaginary line segment L, following the imaginary line segment L. The groove-shaped gap 7 prevents the wall bodies 5b of the adjacent sealing portions 5a from contacting each other. As shown in Figures 1 to 3, the groove-shaped gap 7 has a groove bottom that is the functional surface 2a, one groove wall that is the outer surface 5ba opposite to the inner surface facing the sealed space 8 of one wall body 5b of the adjacent sealed portion 5a across the imaginary line L, and the other groove wall that is the outer surface 5ba of the other wall body 5b of the adjacent sealed portion 5a across the imaginary line L, with one groove end open on one side of two sides 2ca along the longitudinal direction x of the functional surface 2a, and the other groove end open on the other side of two sides 2ca along the longitudinal direction x of the functional surface 2a. The width of the groove-like gap 7 is typically set to 30 to 60 μm.

[0027] The wall body 5b is typically formed by photolithography and etching after the resonators 3, wiring 4, and interconnecting wiring 4a are formed on a wafer that will become the device chip 2. Furthermore, the roof body 5c is typically formed by overlaying a film that will become the roof body 5c on the wall body 5b and then adhering or welding the film to the wall body 5b after the wall body 5b is formed on the wafer that will become the device chip 2. After adhering or welding the film to the wall body 5b in this manner, the film is typically trimmed by photolithography and etching to form the groove opening 7d of the groove-like gap 7.

[0028] In the manufacturing process of the acoustic wave device 1, heat treatment is often performed in the steps of forming the wall body 5b, forming the roof body 5c, and forming the bumps 12 (described later). Additionally, the acoustic wave device 1 generates heat in an operating state. On the other hand, the inorganic material constituting the device chip 2 and the organic material constituting the wall body 5b have significantly different thermal expansion coefficients. Therefore, during the manufacturing process and in the operating state, peeling (partial separation between the device chip 2 and the wall body 5b) due to heat tends to occur at the bonding interface between the device chip 2 and the wall body 5b (where the wall body 5b contacts the functional surface 2a).Furthermore, warping due to heat applied to the acoustic wave device 1 tends to occur. In the acoustic wave device 1 according to this embodiment, the sealing body 5, which covers substantially the entire functional surface 2a of the device chip 2, is divided into two or more parts via the groove-like gaps 7 in the length direction x of the rectangular functional surface 2a, where a large dimensional difference occurs during thermal expansion (the difference between the dimensions of the device chip 2 and the sealing body 5 during thermal expansion), and therefore peeling and warping as described above are minimized. In other words, the difference between the dimensions of the device chip 2 during thermal expansion and the dimensions of each sealing portion 5a during thermal expansion is smaller than when a single sealing body 5 is formed over the entire length direction x of the functional surface 2a.

[0029] In the first example shown in Figures 1 to 3, the groove-like gap 7 is formed to follow the straight line La, which is the virtual line segment L that extends between two sides along the longitudinal direction x of the functional surface 2a.

[0030] As shown in Figures 7 to 9, such groove-like gap 7 may be formed to follow the line segment Lb, which is the virtual line segment L that extends between two sides along the longitudinal direction x of the functional surface 2a and has a bending point Lc. For reasons of arrangement of the resonator 3, there are quite a few cases where it is preferable not to form the groove-like gap 7 linearly.

[0031] In addition, in this embodiment, in each of the sealing portions 5a, via wiring 11 is formed within a via 10 that penetrates the roof body 5c and the wall body 5b, and one end of the via wiring 11 is connected to wiring 4 formed on the functional surface 2a, and the other end is connected to a bump 12 formed on the roof body 5c. In this embodiment, the bumps 12 can be used to mount the acoustic wave device 1 on a package substrate or a module substrate.

[0032] 6, in this embodiment, a connecting wire 4a is positioned on the functional surface 2a in the groove gap 7, connecting the wiring 4 formed in the sealed space 8 of one of the sealing portions 5a adjacent to each other across the groove gap 7 with the wiring 4 formed in the sealed space 8 of the other sealing portion 5a. In addition, as shown in FIG. 6, the cross-sectional contour shape of this connecting wire 4a along the continuous direction of the groove gap 7 is trapezoidal, with the width of the connecting wire 4a gradually increasing as it approaches the functional surface 2a. Specifically, the cross-sectional contour shape of the interconnection 4a is a trapezoid having a lower base 4b, an upper base 4c that is shorter than the lower base 4b, and sloping left and right sides 4d. By configuring the interconnection 4a in this way, when forming the wall body 5b after forming the interconnection 4a, the constituent material of the wall body 5b can be easily distributed without creating gaps outside the corner portion 4e where the lower base 4b and the side edge 4d meet. The angle formed between the lower base 4b and the side edge 4d is preferably 60 degrees or more and 80 degrees or less.

[0033] It should be noted that 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] 1. Acoustic wave devices 2. Device chip 2a Functional aspect 2b Thickness side 2c, 2ca side 3, 30, 31 resonators 3a IDT electrode 3b reflector 3c electrode finger 3D Busbar 3e electrode finger 3F bus bar 4 Wiring 4a Connecting wiring 4b Bottom bottom 4c upper base 4d sides 4e Corner part 5 Sealing body 5a Sealing part 5b Wall Body 5ba exterior 5c Roof body 6 Margin 7 Groove-shaped gap 7a Groove bottom 7b Groove wall 7c Groove end 7d Mizonokuchi 8 Sealed space 9 circuits 9a Input / Output Port 9b Grand 10 Via 11 Via in wiring 12 Bump x length direction y propagation direction L imaginary line segment La straight line Lb line segment Lc bending point

Claims

1. An acoustic wave device configured such that a region of a functional surface of one device chip other than a vicinity of an edge where the functional surface and a side surface of the device chip are in contact is covered with a sealing body, the device chip has a rectangular contour of the functional surface when viewed in a direction perpendicular to the functional surface; The sealing body is an assembly of two or more sealing portions divided in the length direction based on a virtual line segment extending between two sides along the length direction of the functional surface, and each of the sealing portions is composed of three components: a wall body formed so as to surround a formation region of a resonator configured to include an IDT electrode on the functional surface; a roof body supported on the wall body with a gap between the wall body and the functional surface; and the functional surface, and the interior of the sealing portion is a sealing space for the resonator; An acoustic wave device in which a groove-shaped gap is formed between the wall bodies of the sealing portions adjacent to each other on either side of the imaginary line segment, the groove-shaped gap following the imaginary line segment, so that the wall bodies of the adjacent sealing portions are not in contact with each other.

2. The acoustic wave device according to claim 1 , wherein the groove-like gap is formed so as to follow a straight line as the imaginary line segment extending between two sides along the length direction of the functional surface.

3. The acoustic wave device according to claim 1, wherein the groove-like gap is formed to follow a virtual line segment that spans two sides along the length direction of the functional surface and has a bent portion.

4. 2. The acoustic wave device of claim 1, wherein a via wiring is formed in each of the sealing portions, the via wiring having one end connected to a wiring formed on the functional surface within a via penetrating the roof body and the wall body, and the other end connected to a bump formed on the roof body.

5. A communication wiring is positioned on the functional surface of the groove-shaped gap, connecting a wiring formed in the sealed space of one of the sealing portions adjacent to each other across the groove-shaped gap with a wiring formed in the sealed space of the other sealing portion, and 2. The acoustic wave device according to claim 1, wherein the cross-sectional contour of the interconnection along the direction in which the groove-like gap continues is trapezoidal, with the width of the interconnection gradually increasing as it approaches the functional surface.

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