Acoustic wave device and module including the same

Abstract

To provide an acoustic wave device with improved power resistance and a module including the acoustic wave device.SOLUTION: An elastic wave device includes a piezoelectric substrate, and an IDT electrode formed on the piezoelectric substrate, and the IDT electrode includes a first metal layer made of a first metal having a concentration of 99 wt.% or more, and a second metal layer made of an alloy of the first metal and a second metal having a concentration of 95 wt.% or more and less than 99 wt.%, the first metal layer and the second metal layer are each formed in three or more layers, the first metal layer and the second metal layer are alternately stacked, and the total thickness of the second metal layers is greater than the total thickness of the first metal layers.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an acoustic wave device and a module including the acoustic wave device, and more particularly to a surface acoustic wave device using SH waves, such as a filter, a duplexer, or a multiplexer. [Background technology]

[0002] 2. Description of the Related Art In high-frequency communication systems for mobile communication terminals, such as smartphones, high-frequency filters and the like are used to remove unnecessary signals outside the frequency band used for communication.

[0003] Acoustic wave devices having surface acoustic wave (SAW) elements are used in high frequency filters, etc. A SAW element is an element in which an IDT (Interdigital Transducer) having a pair of comb-shaped electrodes is formed on a piezoelectric substrate.

[0004] Patent Document 1 discloses a surface acoustic wave device and a method for manufacturing the same. It is possible to provide a SAW device and a method for manufacturing the same that can improve the power durability when the device is miniaturized and operates at higher frequencies. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-78384 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the SAW device disclosed in Patent Document 1 cannot ensure the power resistance of the IDT electrodes that meets the recent demands for higher frequencies and smaller sizes.

[0007] For this reason, it is not possible to provide an acoustic wave device with sufficient power resistance.

[0008] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide an acoustic wave device with improved power durability and a module including the acoustic wave device. [Means for solving the problem]

[0009] The acoustic wave device according to the present disclosure includes: a piezoelectric substrate; an IDT electrode formed on the piezoelectric substrate; Equipped with The IDT electrode is Aluminum a first metal layer made of a first metal having a concentration of 99% by weight or more; Aluminum The concentration is 95% by weight or more but less than 99% by weight Aluminum and Copper a second metal layer comprising an alloy of the first metal layer and the second metal layer are each formed of three or more layers, the first metal layer and the second metal layer are alternately stacked, The total thickness of the second metal layers is greater than the total thickness of the first metal layers in the acoustic wave device.

[0011] titanium The bottom layer consists of moreover The inclusion of the above is considered to be an aspect of the present disclosure.

[0012] In one aspect of the present invention, the total thickness of the first metal layer and the second metal layer is between one half and three-quarters of the thickness of the IDT electrode.

[0015] The second metal layer is aluminum In one embodiment of the present disclosure, the concentration of is 95% by weight or more and 97.5% by weight or less.

[0017] In one aspect of the present disclosure, the piezoelectric substrate is a substrate made of a single crystal of lithium niobate or lithium tantalate.

[0018] In one embodiment of the present disclosure, the piezoelectric substrate has a support substrate on a main surface opposite to a main surface on which the IDT electrode is formed, and the support substrate is a substrate made of sapphire, silicon, alumina, spinel, quartz, or glass.

[0019] A module including the acoustic wave device is one aspect of the present invention. [Effects of the Invention]

[0020] According to the present disclosure, it is possible to provide an acoustic wave device with improved mechanical strength and a module including the acoustic wave device. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a longitudinal sectional view of an acoustic wave device according to a first embodiment. [Figure 2] 3A and 3B are diagrams illustrating an example of an acoustic wave element of the acoustic wave device according to the first embodiment. [Figure 3] FIG. 1 is a diagram schematically illustrating a prototype according to the first embodiment. [Figure 4] FIG. 10 is a diagram showing conditions for prototypes 1 to 4 of the acoustic wave device 1 according to the first embodiment. [Figure 5] The results of fuse tests on prototypes 1 to 4 and the comparative example are shown. [Figure 6] FIG. 10 is a diagram showing the results of a stress life test for Prototype 4 and a comparative example. [Figure 7] FIG. 10 is a longitudinal sectional view of a module to which the acoustic wave device of the second embodiment is applied. DETAILED DESCRIPTION OF THE INVENTION

[0022] The embodiments will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals. Duplicate descriptions of these parts will be appropriately simplified or omitted.

[0023] Embodiment 1 FIG. 1 is a longitudinal sectional view of an acoustic wave device according to a first embodiment.

[0024] As shown in FIG. 1, the acoustic wave device 1 includes a wiring substrate 3, external connection terminals 31, a device chip 5, electrode pads 9, bumps 15, and a sealing portion 17.

[0025] For example, the wiring board 3 is a multi-layer board made of resin, or a low temperature co-fired ceramics (LTCC) multi-layer board made of a plurality of dielectric layers.

[0026] A plurality of external connection terminals 31 are formed on the lower surface of the wiring board 3.

[0027] A plurality of electrode pads 9 are formed on the main surface of the wiring substrate 3. For example, the electrode pads 9 are made of copper or an alloy containing copper. For example, the thickness of the electrode pads 9 is 10 μm to 20 μm.

[0028] The bumps 15 are formed on the upper surface of each of the electrode pads 9. For example, the bumps 15 are gold bumps. For example, the height of the bumps 15 is 10 μm to 50 μm.

[0029] A gap 16 is formed between the wiring substrate 3 and the device chip 5 .

[0030] The device chip 5 is mounted on the wiring substrate 3 by flip-chip bonding via the bumps 15. The device chip 5 is electrically connected to the plurality of electrode pads 9 via the plurality of bumps 15.

[0031] The device chip 5 is a substrate on which the acoustic wave elements 52 are formed. For example, on the main surface of the device chip 5, a transmission filter and a reception filter including a plurality of acoustic wave elements 52 are formed.

[0032] The transmit filter is formed so as to allow passage of electrical signals in a desired frequency band, and is, for example, a ladder-type filter made up of a plurality of series resonators and a plurality of parallel resonators.

[0033] The receive filter is configured to allow electrical signals in a desired frequency band to pass through, and is, for example, a ladder filter.

[0034] The device chip 5 includes a piezoelectric substrate 11. The device chip 5 may also include a support substrate .

[0035] The piezoelectric substrate 11 is a substrate made of, for example, a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz. In another example, the piezoelectric substrate 11 is a substrate made of a piezoelectric ceramic.

[0036] An acoustic wave element 52 is formed on the main surface of piezoelectric substrate 11. Acoustic wave element 52 is, for example, a resonator including an IDT electrode.

[0037] A support substrate 21 is bonded to the other main surface of the piezoelectric substrate 11. The support substrate 21 is bonded by, for example, van der Waals force. Alternatively, the support substrate 21 may be bonded via an adhesive layer (not shown).

[0038] The support substrate 21 is a substrate made of, for example, sapphire, silicon, alumina, spinel, quartz, or glass.

[0039] The sealing portion 17 is formed so as to cover the device chip 5. For example, the sealing portion 17 is made of an insulating material such as a synthetic resin. For example, the sealing portion 17 is made of a metal.

[0040] When the sealing portion 17 is made of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, etc. Preferably, the sealing portion 17 is made of an epoxy resin and is formed of the epoxy resin using a low-temperature curing process.

[0041] Next, an example of acoustic wave element 52 formed on device chip 5 will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of an acoustic wave element of the acoustic wave device according to the first embodiment.

[0042] 2, an IDT (Interdigital Transducer) 52a and a pair of reflectors 52b are formed on the main surface of the device chip 5. The IDT 52a and the pair of reflectors 52b are provided so as to be able to excite acoustic waves (mainly SH waves).

[0043] For example, the IDT 52a and the pair of reflectors 52b may be formed of an alloy of aluminum and copper, or may be formed of a suitable metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, or silver, or an alloy thereof.

[0044] For example, the IDT 52a and the pair of reflectors 52b are formed of a laminated metal film in which a plurality of metal layers are stacked. For example, the thickness of the IDT 52a and the pair of reflectors 52b is 150 nm to 450 nm.

[0045] The IDT 52a includes a pair of comb-shaped electrodes 52c that face each other and include a plurality of electrode fingers 52d and a bus bar 52e.

[0046] The electrode fingers 52d are arranged with their longitudinal directions aligned. The bus bar 52e connects the electrode fingers 52d.

[0047] One of the pair of reflectors 52b is adjacent to one side of the IDT 52a, and the other of the pair of reflectors 52b is adjacent to the other side of the IDT 52a.

[0048] Next, a description will be given of a prototype of acoustic wave device 1 according to this embodiment and the results of short-term power measurement. The inventors measured the power handling capability of IDT 52a of acoustic wave device 1 according to this embodiment under the following conditions.

[0049] Fig. 3 is a diagram schematically illustrating the prototype according to the embodiment 1. Fig. 3 is a schematic cross-sectional view of an electrode finger 52d of an IDT 52a.

[0050] As shown in FIG. 3, first to eleventh metal layers constituting the IDT are stacked on a piezoelectric substrate 11.

[0051] As shown in FIG. 3, a bottom titanium layer 1BTi is formed as a first layer. An aluminum layer 2Al is formed as a second layer. An aluminum copper layer 3AlCu is formed as a third layer. An aluminum layer 4Al is formed as a fourth layer. An aluminum copper layer 5AlCu is formed as a fifth layer. An aluminum layer 6Al is formed as a sixth layer. An aluminum copper layer 7AlCu is formed as a seventh layer. An aluminum layer 8Al is formed as an eighth layer. An aluminum copper layer 9AlCu is formed as a ninth layer. An aluminum layer 10Al is formed as a tenth layer. Furthermore, a top titanium layer 11TTi is formed as an eleventh layer.

[0052] Here, the second, fourth, sixth, eighth and tenth aluminum layers have an aluminum concentration of 99% by weight or more.

[0053] The aluminum copper layers of the third, fifth, seventh, and ninth layers have an aluminum concentration of 95% by weight or more. The aluminum copper layers of the third, fifth, seventh, and ninth layers may have a copper concentration of, for example, 1% by weight or more. The aluminum copper layers of the third, fifth, seventh, and ninth layers may have a copper concentration of, for example, 1.5% by weight or more, 2.0% by weight or more, or 2.5% by weight or more but less than 5.0% by weight.

[0054] FIG. 4 is a diagram showing conditions for prototypes 1 to 4 of the acoustic wave device 1 according to the first embodiment.

[0055] As shown in Figure 4, in all of Prototypes 1 to 4, the bottom titanium of the first layer was 101 nm thick, and the top titanium of the 11th layer was 15 nm thick. In all of Prototypes 1 to 4, the total thickness of the second to tenth layers was 301 nm.

[0056] As shown in Figure 4, the thicknesses of the second, fourth, sixth, eighth, and tenth aluminum layers of Prototype 1 are 48 nm, 48 nm, 48 nm, 48 nm, and 49 nm, respectively. The thicknesses of the third, fifth, seventh, and ninth aluminum-copper layers of Prototype 1 are all 15 nm.

[0057] In Prototype 1, the total thickness of the aluminum layers 2, 4, 6, 8, and 10 is 241 nm, and the total thickness of the aluminum-copper layers 3, 5, 7, and 9 is 60 nm.

[0058] As shown in Figure 4, the thicknesses of the aluminum layers 2, 4, 6, 8, and 10 of Prototype 2 are 44 nm, 44 nm, 44 nm, 44 nm, and 45 nm, respectively. The thicknesses of the aluminum-copper layers 3, 5, 7, and 9 of Prototype 2 are all 20 nm.

[0059] In Prototype 2, the total thickness of the aluminum layers 2, 4, 6, 8, and 10 is 221 nm, and the total thickness of the aluminum-copper layers 3, 5, 7, and 9 is 80 nm.

[0060] As shown in Figure 4, in Prototype 3, the thicknesses of the second, fourth, sixth, eighth, and tenth aluminum layers are 36 nm, 36 nm, 36 nm, 36 nm, and 37 nm, respectively. In addition, the thicknesses of the third, fifth, seventh, and ninth aluminum-copper layers in Prototype 3 are all 30 nm.

[0061] In Prototype 3, the total thickness of the aluminum layers 2, 4, 6, 8, and 10 is 181 nm. The total thickness of the aluminum-copper layers 3, 5, 7, and 9 is 120 nm. In other words, the ratio of the total thickness of the aluminum layers 2, 4, 6, 8, and 10 to the total thickness of the aluminum-copper layers 3, 5, 7, and 9 is 3:2 or more.

[0062] As shown in Figure 4, in Prototype 4, the aluminum layers 2, 4, 6, 8, and 10 have thicknesses of 28 nm, 28 nm, 28 nm, 28 nm, and 29 nm, respectively. In addition, the aluminum-copper layers 3, 5, 7, and 9 of Prototype 4 all have thicknesses of 40 nm.

[0063] In Prototype 4, the total thickness of the aluminum layers 2, 4, 6, 8, and 10 is 141 nm. In Prototype 2, the total thickness of the aluminum-copper layers 3, 5, 7, and 9 is 160 nm. In other words, the ratio of the total thickness of the aluminum layers 2, 4, 6, 8, and 10 to the total thickness of the aluminum-copper layers 3, 5, 7, and 9 is 29:32 or less.

[0064] Figure 5 shows the results of fuse tests on prototypes 1 to 4 and a comparative example. Both the prototypes and the comparative example were Band-5 duplexers. In addition, instead of the metal layers from layer 2 to layer 10 in the first embodiment, the comparative example used a single layer of aluminum-copper alloy with an aluminum concentration of 98.5 wt % and a copper concentration of 1.5 wt % and a thickness of 301 nm, the same as the total thickness of the metal layers. Other conditions were the same as those in the first embodiment.

[0065] As shown in Figure 5, the required specification for the prototype Band-5 duplexer was 30 dB, and both the prototype and the comparative example passed the fuse test. The higher the copper content in the IDT, the better the power handling capability, but the greater the insertion loss. The increase in insertion loss becomes more pronounced as the frequency increases.

[0066] Although prototypes 1 and 2 were unable to achieve the same level of power resistance as the comparative example, because they contained less copper than the comparative example, they had lower insertion loss and were able to achieve power resistance that met the required specifications.

[0067] Prototype 3 was able to achieve a power resistance close to that of the comparative example, and because it contained less copper than the comparative example, it had a smaller insertion loss and was able to achieve a power resistance that met the required specifications.

[0068] Prototype 4 was able to achieve higher power handling than the comparative example, and because it contained less copper than the comparative example, it had lower insertion loss and was able to achieve power handling that met the required specifications.

[0069] FIG. 6 shows the results of the stress life test of prototype 4 in the first embodiment and the comparative example.

[0070] As shown in Figure 6, both Prototype 4 and the comparative example achieved power durability that met the required specifications. Furthermore, Prototype 4 achieved a life that was approximately 10 times longer than that of the comparative example at an applied power of around 32 dBm.

[0071] According to the first embodiment described above, it is possible to provide an acoustic wave device with improved power durability.

[0072] Embodiment 2 7 is a longitudinal sectional view of a module to which the acoustic wave device according to Embodiment 2 is applied. Note that the same reference numerals are used to designate parts that are the same as or correspond to parts in Embodiment 1, and a description of these parts will be omitted.

[0073] 7, the module 100 includes a wiring board 130, a plurality of external connection terminals 131, an integrated circuit component IC, an acoustic wave device 1, an inductor 111, and a sealing portion 117.

[0074] The plurality of external connection terminals 31 are formed on the lower surface of the wiring board 130. The plurality of external connection terminals 131 are mounted on a motherboard of a preset mobile communication terminal.

[0075] For example, the integrated circuit component IC is mounted inside the wiring board 130. The integrated circuit component IC includes a switching circuit and a low-noise amplifier.

[0076] The acoustic wave device 1 is mounted on the main surface of the wiring substrate 130.

[0077] The inductor 111 is mounted on the main surface of the wiring board 130. The inductor 111 is mounted for impedance matching. For example, the inductor 111 is an integrated passive device (IPD).

[0078] The sealing portion 117 seals a plurality of electronic components including the acoustic wave device 1.

[0079] According to the second embodiment described above, the module 100 includes the acoustic wave device 1. Therefore, it is possible to provide a module including an acoustic wave device with improved power handling capability.

[0080] Having described several aspects of at least one embodiment, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of this disclosure.

[0081] It is to be understood that the embodiments of the methods and apparatus described herein are not limited in their application to the details of construction and the arrangement of components set forth in the above description or illustrated in the accompanying drawings, and that the methods and apparatus may be implemented in other embodiments and practiced or carried out in various ways.

[0082] The specific implementation examples are provided here for illustrative purposes only and are not intended to be limiting.

[0083] The phraseology and terminology used in this disclosure are for the purpose of description and should not be regarded as limiting. The use herein of "including," "comprising," "having," "including" and variations thereof means the inclusion of the items listed thereafter and equivalents thereof and additional items.

[0084] References to "or" may be construed as meaning that any term described using "or" refers to one, more than one, and all of the described terms.

[0085] All references to front, back, left, right, top, bottom, top, bottom, width, length, and front and back are intended for convenience of description and are not intended to limit the components of this disclosure to any one positional or spatial orientation. Accordingly, the foregoing description and drawings are by way of example only. [Explanation of symbols]

[0086] 1. Acoustic wave devices 3. Wiring board 5 device chips, 11 Piezoelectric substrate 21 Support substrate 9 Electrode Pads 15 Bump 16 void 17 Sealing part 31 External connection terminal 52 acoustic wave element, 52a IDT, 52b reflector, 52c interdigital electrode, 52d electrode finger 100 module, 111 inductor, 117 sealing portion, 130 wiring board, 131 external connection terminal, IC integrated circuit component

Claims

1. a piezoelectric substrate; an IDT electrode formed on the piezoelectric substrate; Equipped with The IDT electrode is a first metal layer made of a first metal having an aluminum concentration of 99% by weight or more; a second metal layer made of an aluminum-copper alloy having an aluminum concentration of 95% by weight or more but less than 99% by weight; the first metal layer and the second metal layer are each formed of three or more layers, the first metal layer and the second metal layer are alternately stacked, An acoustic wave device in which the total thickness of the second metal layers is greater than the total thickness of the first metal layers.

2. An acoustic wave device as described in claim 1, further comprising a bottom layer made of titanium.

3. The acoustic wave device according to claim 1 , wherein the total thickness of the first metal layer and the second metal layer is between half and three-quarters of the thickness of the IDT electrode.

4. The acoustic wave device according to claim 1 , wherein the second metal layer has an aluminum concentration of 95% by weight or more and 97.5% by weight or less.

5. 5. The acoustic wave device according to claim 1, wherein the piezoelectric substrate is a substrate made of a single crystal of lithium niobate or lithium tantalate.

6. 6. The acoustic wave device according to claim 1, further comprising a support substrate on a main surface of the piezoelectric substrate opposite to a main surface on which the IDT electrode is formed, the support substrate being made of sapphire, silicon, alumina, spinel, quartz, or glass.

7. A module comprising an acoustic wave device described in any one of claims 1 to 6.

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