Elastic wave device
A three-layer structure with a thermally conductive insulating layer between conductive layers in elastic wave devices enhances heat dissipation, addressing inefficiencies in existing devices without additional manufacturing steps.
Patent Information
- Application Number
- JP2023221745
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-12-27
- Publication Date
- 2025-07-09
AI Technical Summary
Existing elastic wave devices face challenges in efficiently releasing heat generated in the signal wiring regions to the outside without increasing the number of manufacturing process steps.
A three-layer structure is implemented in the device chip, where the second layer is made of an insulating material with high thermal conductivity, positioned between the first and third conductive layers, forming a heat transfer line to efficiently dissipate heat without additional process steps.
The structure effectively dissipates heat generated in the device chip, improving thermal management without increasing the manufacturing complexity.
Smart Images
Figure 2025103968000001_ABST
Abstract
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 mobile communication devices and the like.
Background Art
[0002] An elastic wave device having a CSP (Chip Size Package) structure, an elastic wave device having a WLP (Wafer Level Package) structure, and an elastic wave device mounted on a module substrate together with other electronic devices as a bare chip all include a device chip in which at least one surface is constituted by a piezoelectric body as a component. On the one surface, i.e., the functional surface, of this device chip, a resonator and wiring are formed of a conductive material by photolithography technology and etching.
[0003] FIG. 10 shows an example of a circuit composed of such a resonator and wiring, and FIG. 11 shows an example of a pattern realizing the circuit provided on the functional surface of the device chip. In FIG. 11, reference numeral 100 denotes a device chip, 101 denotes a resonator, 102 denotes wiring, 103 denotes an input pad, 104 denotes an output pad, 105 denotes a ground pad, and 106 denotes an antenna pad. In FIG. 11, in the portion indicated by reference numeral 107, as shown in FIG. 12, a ground wiring 102b connecting a part of the resonator 100 and the ground pad 105 passes over a signal wiring 102a connecting two resonators 100 to each other. The layout is such that. Hereinafter, such a portion is referred to as a wiring crossing portion 107. In such a wiring crossing portion 107, after forming the signal wiring 102a as the first layer M1, a second layer D2 made of an insulating material is formed, and it is necessary to form the ground wiring 102b as the third layer M3 on this second layer D2. Therefore, in the manufacturing process of the elastic wave device, a step of forming the first layer M1, a step of forming the second layer D2, and a step of forming the third layer M3 are required.
[0004] On the other hand, in FIG. 11, in the portion indicated by reference sign S, the layout is such that a gap is formed between the signal wiring 102a and the ground wiring 102b, and the portions indicated by reference signs N1 to N4 in FIG. 11 on the signal wiring 102a are not connected to any of the ground wirings 102b. Summary of the Invention Problems to be Solved by the Invention
[0005] When a signal is input to the surface acoustic wave device, heat is generated in the formation region of the resonator 101. The heat in the formation region of the resonator 101 connected to the ground wiring 102b can be efficiently released to the outside through this ground wiring 102b as a heat transfer path. On the other hand, such heat is difficult to be efficiently released to the outside in the formation region of the signal wiring 102a. The main problem to be solved by the present invention is to provide a new structure capable of efficiently releasing the heat generated in the device chip to the outside by inputting a signal to the surface acoustic wave device without increasing the number of steps (process steps) in the manufacturing process in a surface acoustic wave device provided with a circuit (multilayer wiring) composed of such multiple layers. Means for Solving the Problems
[0006] In order to achieve the above object, in the present invention, a surface acoustic wave device is provided with a pattern having at least a first layer made of a conductive material, a second layer made of an insulating material, and a third layer made of a conductive material on a functional surface composed of a piezoelectric body in a device chip. In a three-layer region where all of the three layers overlap, the second layer is positioned on the first layer, and the third layer is positioned on the second layer. In a two-layer region where any two of the three layers overlap, the second layer is positioned on the first layer, the third layer is positioned on the first layer, or the third layer is positioned on the second layer, and is formed accordingly. Two or more resonators, signal wiring for connecting the resonators to each other, ground wiring for grounding a part of the resonators to a ground electrode, and a heat transfer line for connecting the signal wiring and the ground wiring. The resonator is constituted by the first layer. The signal wiring and the ground wiring are constituted by both the first layer and the third layer, or either one of them. The heat transfer line is constituted by the second layer. Moreover, a first connection end portion of the heat transfer line to the signal wiring and a second connection end portion of the heat transfer line to the ground wiring are each in the three-layer region, and a single-layer region composed only of the second layer is formed between the first connection end portion and the second connection end portion.
[0007] In the three-layer region, making the second layer electrically insulate the first layer and the third layer is one aspect of the embodiment of this invention.
[0008] Also, making the second layer be constituted of a resin having a thermal conductivity of 1 W / mK or more is one aspect of the embodiment of this invention.
[0009] Also, on at least one side sandwiching the single-layer region composed only of the second layer in the heat transfer line, making the overlapping area between the second layer and the third layer smaller than the overlapping area between the first layer and the second layer is one aspect of the embodiment of this invention.
[0010] Also, on at least one side sandwiching the single-layer region composed only of the second layer in the heat transfer line, making the overlapping area between the first layer and the second layer smaller than the overlapping area between the second layer and the third layer is one aspect of the embodiment of this invention.
Effect of the Invention
[0011] According to the elastic wave device of the present invention, the heat transfer line composed of the second layer can rationally provide a structure capable of efficiently discharging the heat generated in the device chip to the outside without increasing the number of steps (number of processes) in the manufacturing process for the elastic wave device provided with multilayer wiring.
Brief Description of Drawings
[0012]
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[0013] Hereinafter, typical embodiments of the present invention will be described with reference to FIGS. 1 to 9. The elastic wave device 1 according to this embodiment is suitable for use as a frequency filter or the like in a mobile communication device or the like.
[0014] In the illustrated example, the elastic wave device 1 has a CSP structure. However, the structure of the device chip 3 constituting the elastic wave device 1 described below is also applicable to an elastic wave device having a WLP structure or an elastic wave device mounted on a module substrate together with other electronic devices as a bare chip.
[0015] In the illustrated example, the elastic wave device 1 includes a device chip 3 mounted on one surface 2a of the package substrate 2 with the functional surface 3a facing. On the functional surface 3a of the device chip 3, a resonator 7a as a functional element 7 including an IDT electrode 7b (see FIG. 6) is formed.
[0016] Typically, the device chip 3 is configured to have a rectangular plate shape with a side length of 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm. Further, the package substrate 2 is configured to have a rectangular plate shape with a side length of 0.7 to 3 mm and a thickness of 0.15 to 0.2 mm. The elastic wave device 1 has a thickness of about 0.4 to 0.6 mm. Typically, the elastic wave device 1 has a hexahedron shape having two rectangular surfaces and four side surfaces on the thickness side.
[0017] The cross-sectional structure thereof is shown in FIG. 2. In the figure, reference numeral 3 denotes the device chip, reference numeral 3a denotes its functional surface, and reference numeral 7a denotes the resonator. Between the device chip 3 and the package substrate 2, there are protruding electrodes 10 (bumps) that electrically connect the wiring 8a formed on the device chip 3 and the wiring formed on the package substrate 2 side, and a gap 5 is formed between these protruding electrodes 10. Reference numeral 9 in the figure is a pad that is part of the wiring 8a of the device chip 3, and reference numeral 2b is a pad formed on one surface 2a of the package substrate 2 on the mounting side of the device chip 3. The circuit 8 of the device chip 3 is electrically connected to the package substrate 2 by the protruding electrodes 10 interposed between both pads 2b and 9. External connection terminals 2d for connecting the surface acoustic wave device 1 to a mother board (not shown) are formed on the other surface 2c of the package substrate 2 opposite to the one surface 2a.
[0018] From the state where the device chip 3 is mounted on the one surface 2a of the package substrate 2, a sealing portion 4 is formed on the one surface 2a of the package substrate 2. Such a sealing portion 4 is composed of a resin having insulation properties. The sealing portion 4 formed in this way includes a first portion 4a that covers the non-functional surface 3b of the device chip 3 facing the functional surface 3a of the device chip 3, and a second portion 4b that follows the first portion 4a and covers the side surface 3c having the thickness of the device chip 3 between the functional surface 3a and the non-functional surface 3b and reaches the one surface 2a of the package substrate 2. And, by the sealing portion 4 formed in this way, an internal space 6 (also referred to as a hollow structure portion or an air cavity, etc.) is formed between the functional surface 3a of the device chip 3 and the one surface 2a of the package substrate 2. That is, the sealing portion 4 hermetically seals the gap 5 over the entire circumference of the device chip 3, and thereby, the internal space 6 is formed between the functional surface 3a of the device chip 3 and the one surface 2a of the package substrate 2.
[0019] The device chip 3 includes a functional element 7 including an IDT electrode 7b (see FIG. 6) and a resonator 7a in an example shown in the figure at a portion of the functional surface 3a facing the internal space 6. The device chip 3 has a function of propagating elastic waves. Typically, a piezoelectric material such as lithium tantalate or lithium niobate is used for the device chip 3. Further, the device chip 3 may be configured by laminating these piezoelectric materials on a support such as sapphire, silicon, alumina, spinel, quartz or glass.
[0020] Fig. 6 shows an example of the resonator 7a that becomes a SAW filter. The resonator 7a has an IDT electrode 7b and a reflector 7c formed so as to sandwich the IDT electrode 7b. The IDT electrode 7b is composed of electrode pairs, and each electrode pair is formed by connecting a plurality of electrode fingers 7d arranged in parallel so that the length direction intersects the propagation direction x of the elastic wave at one end side thereof with a bus bar 7e. The reflector 7c is formed by connecting between the ends of a plurality of electrode fingers 7f arranged in parallel so that the length direction intersects the propagation direction x of the elastic wave with a bus bar 7g. Such a resonator 7a is typically composed of a conductive metal film formed by photolithography technology and etching. In the illustrated example, a plurality of such resonators 7a are formed on one device chip 3.
[0021] Fig. 5 shows the concept of an example of the circuit 8 provided on one device chip 3. In Fig. 5, reference numeral 9a indicates an input pad, reference numeral 9b indicates an output pad, reference numeral 9c indicates a ground pad, and reference numeral 9d indicates an antenna pad.
[0022] In this embodiment, the elastic wave device 1 includes at least a pattern having a first layer M1 made of a conductive material, a second layer D2 made of an insulating material, and a third layer M3 made of a conductive material on a functional surface 3a composed of a piezoelectric material in the device chip 3 constituting the elastic wave device 1. Fig. 1 shows an example of the pattern. The pattern shown in Fig. 1 is the same as the pattern shown in Fig. 11 except for the heat transfer line 14 described later.
[0023] In the three-layer region 11 where all of the three layers overlap, the second layer D2 is positioned on the first layer M1, and the third layer M3 is positioned on the second layer D2. In the two-layer region 12 where any two of the three layers overlap, the second layer D2 is positioned on the first layer M1, the third layer M3 is positioned on the first layer M1, or the third layer M3 is positioned on the second layer D2.
[0024] Also, in the pattern, a single-layer region 13 where only any one of the three layers exists on the functional surface 3a is formed as needed.
[0025] At the same time, the surface acoustic wave device 1 according to this embodiment includes two or more resonators 7a, a signal wiring 8aa connecting the resonators 7a to each other, a ground wiring 8ab grounding a part of the resonator 7a to a ground electrode, and a heat transfer line 14 connecting the signal wiring 8aa and the ground wiring 8ab.
[0026] The resonator 7a is constituted by the first layer M1. The signal wiring 8aa and the ground wiring 8ab are constituted by both or either one of the first layer M1 and the third layer M3. The heat transfer line 14 is constituted by the second layer D2.
[0027] Also, a first connection end portion 14a of the heat transfer line 14 to the signal wiring 8aa and a second connection end portion 14b of the heat transfer line 14 to the ground wiring 8ab are each in the three-layer region 11, and a single-layer region 13 composed only of the second layer D2 is formed between the first connection end portion 14a and the second connection end portion 14b. By making the first connection end portion 14a and the second connection end portion 14b the three-layer regions 11 respectively, the cross-sectional area of the heat dissipation path y (see FIGS. 3 and 4) formed by the heat transfer line 14 can be increased at the first connection end portion 14a and the second connection end portion 14b, and the heat dissipation efficiency can be improved. On the heat dissipation path y, a single-layer region 13 is always located between two three-layer regions 11, and the signal wiring 8aa and the ground wiring 8ab are electrically insulated by this single-layer region 13.
[0028] In the illustrated example, eight heat transfer lines 14 are formed in the pattern shown in FIG. 1. Also, in the illustrated example, in FIG. 1, in the portion indicated by reference numeral 15, as shown in FIG. 7, a ground wiring 8ab that connects one of the plurality of resonators 7a and the ground pad 9c passes over the signal wiring 8aa that connects two resonators 7a to each other (see FIG. 7). Hereinafter, such a portion is referred to as a wiring crossing portion 15. This wiring crossing portion 15 is the three-layer region 11. After forming the signal wiring 8aa as the first layer M1, a second layer D2 made of an insulating material is formed, and the ground wiring 8ab is formed as the third layer M3 on this second layer D2. Therefore, the manufacturing process of the surface acoustic wave device 1 requires a step of forming the first layer M1, a step of forming the second layer D2, and a step of forming the third layer M3. Also, in the illustrated example, in FIG. 1, in the portion indicated by reference numeral S, a layout is formed in which a gap is formed between the signal wiring 8aa and the ground wiring 8ab.
[0029] FIG. 3 shows an enlarged view of the heat transfer line 14 shown in the C portion surrounded by a dashed-dotted line in FIG. 1 among the eight heat transfer lines 14. Through such a heat transfer line 14, the signal wiring 8aa located on the right side of FIG. 3 is physically connected to the ground wiring 8ab located on the left side of FIG. 3 via the heat transfer line 14, but is not electrically connected. As a result, without short-circuiting the signal wiring 8aa and the ground wiring 8ab, the heat near the signal wiring 8aa can be transferred to the ground wiring 8ab and efficiently dissipated to the outside. Since both this heat transfer line 14 and the insulating layer formed between the first layer M1 and the third layer M3 in the wiring crossing portion 15 are made of the second layer D2, such a heat transfer line 14 can be provided in the elastic wave device 1 without increasing the number of steps (number of processes) in the manufacturing process.
[0030] More specifically, as represented by a dotted line in FIG. 5, the heat transfer line 14 is formed so as to connect the signal wiring 8aa between the resonators 7a arranged in series in FIG. 5 and the ground wiring 8ab that connects the resonators 7a arranged in parallel in FIG. 5 and the ground. Thereby, the heat generated in the formation region of the resonators 7a arranged in series, which are prone to heat, is diffused throughout the device chip 3 by the heat transfer line 14, and while preventing a part of the device chip 3 from reaching a locally high temperature, such heat can be radiated to the outside.
[0031] The second layer D2 is preferably made of a resin having a thermal conductivity of 1 W / mK or more. Such a resin includes polyimide with enhanced thermal conductivity. Since polyimide also has good heat resistance, it is optimal as the resin constituting the second layer D2.
[0032] Also, in at least one side sandwiching the single-layer region 13 consisting only of the second layer D2 in the heat transfer line 14, it is preferable that the overlapping area a2 between the second layer D2 and the third layer M3 is smaller than the overlapping area a1 between the first layer M1 and the second layer D2. This is regarded as one of the preferred embodiments. In the first example shown in FIGS. 1 to 7, on both sides sandwiching the single-layer region 13, the overlapping area a2 between the second layer D2 and the third layer M3 is smaller than the overlapping area a1 between the first layer M1 and the second layer D2 (see FIG. 4).
[0033] Further, on at least one side sandwiching the single-layer region 13 composed only of the second layer D2 in the heat transfer line 14, the overlapping area a1 between the first layer M1 and the second layer D2 is made smaller than the overlapping area a2 between the second layer D2 and the third layer M3, which is one of the preferred embodiments. In the second example shown in FIG. 8, on both sides sandwiching the single-layer region 13, the overlapping area a1 between the first layer M1 and the second layer D2 is made smaller than the overlapping area a2 between the second layer D2 and the third layer M3.
[0034] In the third example shown in FIG. 9, on the left side in FIG. 9 sandwiching the single-layer region 13, the overlapping area a2 between the second layer D2 and the third layer M3 is smaller than the overlapping area a1 between the first layer M1 and the second layer D2. At the same time, on the right side in FIG. 9 sandwiching the single-layer region 13, the overlapping area a1 between the first layer M1 and the second layer D2 is made smaller than the overlapping area a2 between the second layer D2 and the third layer M3.
[0035] The surface acoustic wave device 1 described above can be formed reasonably and appropriately by the following process. Step 1: For each region of the wafer that will become the device chip 3 and will become one surface acoustic wave device 1, the first layer M1 is formed on one surface thereof by photolithography technology and etching. The first layer M1 is a conductive metal film and is typically set to a thickness in the range of 0.2 to 0.4 μm. Step 2: For each region of the wafer that will become one surface acoustic wave device 1, the second layer D2 is formed on one surface thereof by photolithography technology and etching. The second layer D2 is made of an insulating material and is typically set to a thickness in the range of 1 to 2 μm. Step 3: For each region that will become one elastic wave device 1 on the wafer, form the third layer M3 on one surface thereof by photolithography technology and etching. The third layer M3 is made of a conductive material and is typically set to a thickness in the range of 3 to 4 μm. Step 4: When constructing the elastic wave device 1 with a CSP structure, form the sealing portion 4 for each region that will become one elastic wave device 1. Step 5: Cut the wafer on which the sealing portion 4 is formed into pieces for each region by dicing.
[0036] Of course, the present invention is not limited to the embodiments described above, and includes all embodiments capable of achieving the object of the present invention.
Explanation of Reference Numerals
[0037] 1 Elastic wave device 2 Package substrate 2a One surface 2b Pad 2c The other surface 2d External connection terminal 3 Device chip 3a Functional surface 3b Non-functional surface 3c Side surface 4 Sealing portion 4a First part 4b Second part 5 Gap 6 Internal space 7 Functional element 7a Resonator 7b IDT electrode 7c Reflector 7d Electrode finger 7e Bus bar 7f Electrode finger 7g Bus bar 8 Circuit 8a Wiring 8aa Signal wiring 8ab Ground wiring 9 Pad 9a Input pad 9b Output Pad 9c Ground Pad 9d Antenna Pad 10 Protruding Electrode 11 Three-Layer Region 12 Two-Layer Region 13 Single-Layer Region 14 Heat Transfer Line 14a First Connection End 14b Second Connection End 15 Wiring Crossing M1 First Layer D2 Second Layer M3 Third Layer x Propagation Direction y Heat Dissipation Path S Gap
Claims
1. On a functional surface composed of a piezoelectric body in a device chip, there is at least a pattern having a first layer made of a conductive material, a second layer made of an insulating material, and a third layer made of a conductive material, In a three-layer region where all of the three layers overlap, the second layer is positioned on the first layer, and the third layer is positioned on the second layer, In a two-layer region where any two of the three layers overlap, the second layer is positioned on the first layer, the third layer is positioned on the first layer, or the third layer is positioned on the second layer, and it is formed, It includes two or more resonators, a signal wiring connecting the resonators to each other, a ground wiring grounding a part of the resonator to a ground electrode, and a heat transfer line connecting the signal wiring and the ground wiring, The resonator is constituted by the first layer, The signal wiring and the ground wiring are constituted by both or either one of the first layer and the third layer, The heat transfer line is constituted by the second layer, Moreover, a first connection end portion of the heat transfer line to the signal wiring and a second connection end portion of the heat transfer line to the ground wiring are respectively in the three-layer region, and a single-layer region composed only of the second layer is formed between the first connection end portion and the second connection end portion, an elastic wave device.
2. In the three-layer region, the second layer electrically insulates the first layer and the third layer, the elastic wave device according to claim 1.
3. The elastic wave device according to claim 1, wherein the second layer is made of a resin having a thermal conductivity of 1 W / mK or more.
4. On at least one side sandwiching the single-layer region composed only of the second layer in the heat transfer line, the overlapping area of the second layer and the third layer is made smaller than the overlapping area of the first layer and the second layer, the elastic wave device according to claim 1.
5. On at least one side sandwiching the single-layer region composed only of the second layer in the heat transfer line, the overlapping area of the first layer and the second layer is made smaller than the overlapping area of the second layer and the third layer, the elastic wave device according to claim 1.