JP2023112408A - Acoustic wave device and module with acoustic wave device - Google Patents

Abstract

To provide an acoustic wave device of which power resistance is improved, and provide a module having the acoustic wave device.SOLUTION: An acoustic wave device comprises a piezoelectric substrate, and an IDT electrode that is formed on the piezoelectric substrate. The IDT electrode contains: a first metal layer that is formed of a first metal of which concentration is 99% or more; and a second metal layer that is formed of an alloy which is composed of the first metal and a second metal and of which concentration is 95% or more and 99% or less. The plurality of first metal layers and the plurality of second metal layers are formed. The first metal layers and the second metal layers are alternately laminated.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to an acoustic wave device and a module comprising the acoustic wave device. More specifically, it relates to surface acoustic wave devices using SH waves, such as filters, duplexers or multiplexers.

2. Description of the Related Art In high-frequency communication systems for mobile communication terminals typified by smart phones, high-frequency filters and the like are used to remove unnecessary signals outside the frequency band used for communication.

Acoustic wave devices having surface acoustic wave (SAW) elements and the like are used for high-frequency filters and the like. 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.

Patent Literature 1 discloses a surface acoustic wave device and a manufacturing method thereof. It is possible to provide a SAW device and a method of manufacturing the SAW device that can improve the power durability when the device is miniaturized and the frequency is increased.

JP 2003-78384 A

However, in the SAW device disclosed in Patent Document 1, it is not possible to ensure the power resistance of the IDT electrode that meets the recent demands for higher frequencies and smaller sizes.

Therefore, it is not possible to provide an acoustic wave device with sufficient power resistance.

The present disclosure has been made to solve the above problems. 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.

The acoustic wave device according to the present disclosure is
a piezoelectric substrate;
and an IDT electrode formed on the piezoelectric substrate,
The IDT electrode is
a first metal layer made of a first metal having a concentration of 99% or higher;
A second metal layer made of an alloy of the first metal and the second metal having a concentration of 95% or more and less than 99%,
The first metal layer and the second metal layer are each formed in a plurality of layers,
The first metal layer and the second metal layer are alternately laminated in the acoustic wave device.

An aspect of the present disclosure is that the first metal has a higher electrical resistivity than the second metal.

It is an aspect of the present disclosure that the total thickness of the second metal layers is thicker than the total thickness of the first metal layers.

It is an aspect of the present disclosure to include a bottom layer of a third metal having a higher electrical resistivity than the first and second metals.

One aspect of the present invention is that the total thickness of the first metal layer and the second metal layer is half or more and three quarters or less of the thickness of the IDT electrode.

It is an aspect of the present invention that the first metal is aluminum, molybdenum, iridium, tungsten, cobalt, nickel, or ruthenium.

It is an aspect of the present disclosure that the third metal is chromium, strontium, or titanium.

It is an aspect of the present disclosure that the thickness ratio between the first metal layer and the second metal layer is 3:2 to 29:32.

An aspect of the present disclosure is that the second metal layer has a concentration of the first metal of 95% or more and 97.5% or less.

In one aspect of the present disclosure, the second metal layer is such that the first metal is aluminum and the second metal is copper.

An aspect of the present disclosure is that the piezoelectric substrate is a substrate made of a single crystal of lithium niobate or lithium tantalate.

A support substrate is provided on the main surface of the piezoelectric substrate opposite to the main surface on which the IDT electrodes are formed, and the support substrate is a substrate made of sapphire, silicon, alumina, spinel, crystal, or glass. It is considered a form of disclosure.

A module including the acoustic wave device is one aspect of the present invention.

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.

1 is a longitudinal sectional view of an acoustic wave device according to Embodiment 1; FIG. 4A and 4B are diagrams illustrating an example of an acoustic wave element of the acoustic wave device according to Embodiment 1; FIG. FIG. 4 is a diagram schematically showing contents of a trial production in Embodiment 1; FIG. 4 is a diagram showing conditions of prototypes 1 to 4 of the acoustic wave device 1 according to the first embodiment; It is the result of the fuse test of Prototype 1 to Prototype 4 and the comparative example. FIG. 10 is a diagram showing the results of a stress life test of Prototype 4 and Comparative Example. FIG. 10 is a vertical cross-sectional view of a module to which the acoustic wave device of Embodiment 2 is applied;

Embodiments will be described with reference to the accompanying drawings. In addition, the same code|symbol is attached|subjected to the part which is the same or corresponds in each figure. Redundant description of the relevant part will be simplified or omitted as appropriate.

Embodiment 1.
FIG. 1 is a longitudinal sectional view of an acoustic wave device according to Embodiment 1. FIG.

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

For example, the wiring board 3 is a multilayer board made of resin. For example, the wiring board 3 is a Low Temperature Co-fired Ceramics (LTCC) multilayer board consisting of a plurality of dielectric layers.

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

A plurality of electrode pads 9 are formed on the main surface of the wiring board 3 . For example, the electrode pads 9 are made of copper or an alloy containing copper. For example, the electrode pad 9 has a thickness of 10 μm to 20 μm.

A bump 15 is formed on the upper surface of each electrode pad 9 . For example, bump 15 is a gold bump. For example, the bump 15 has a height of 10 μm to 50 μm.

A gap 16 is formed between the wiring board 3 and the device chip 5 .

The device chip 5 is mounted on the wiring board 3 through bumps 15 by flip chip bonding. The device chip 5 is electrically connected to multiple electrode pads 9 via multiple bumps 15 .

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

The transmission filter is formed so that an electrical signal in a desired frequency band can pass. For example, the transmission filter is a ladder-type filter composed of a plurality of series resonators and a plurality of parallel resonators.

The reception filter is formed so that an electrical signal in a desired frequency band can pass. For example, the reception filter is a ladder filter.

The device chip 5 has a piezoelectric substrate 11 . Also, the device chip 5 may include a support substrate 21 .

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

An elastic wave element 52 is formed on the main surface of the piezoelectric substrate 11 . The acoustic wave device 52 is, for example, a resonator including IDT electrodes.

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

The support substrate 21 is, for example, a substrate made of sapphire, silicon, alumina, spinel, crystal, or glass.

The sealing portion 17 is formed so as to cover the device chip 5 . For example, the sealing portion 17 is made of an insulator such as synthetic resin. For example, the sealing portion 17 is made of metal.

When the sealing portion 17 is made of synthetic resin, the synthetic resin is epoxy resin, polyimide, or the like. Preferably, the encapsulant 17 is made of epoxy using a low temperature curing process.

Next, an example of the acoustic wave element 52 formed on the device chip 5 will be described with reference to FIG. FIG. 2 is a diagram showing an example of an acoustic wave element of the acoustic wave device according to Embodiment 1. FIG.

As shown in FIG. 2 , an IDT (Interdigital Transducer) 52 a and a pair of reflectors 52 b 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 excite elastic waves (mainly SH waves).

For example, the IDT 52a and the pair of reflectors 52b are made of an alloy of aluminum and copper. For example, the IDT 52a and the pair of reflectors 52b are made of suitable metals such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver, or alloys thereof.

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 laminated. For example, the thickness of the IDT 52a and the pair of reflectors 52b is 150 nm to 450 nm.

The IDT 52a includes a pair of comb electrodes 52c. The pair of comb electrodes 52c are opposed to each other. The comb-shaped electrode 52c includes a plurality of electrode fingers 52d and busbars 52e.

The plurality of electrode fingers 52d are arranged with their longitudinal directions aligned. Bus bar 52e connects a plurality of electrode fingers 52d.

One of the pair of reflectors 52b is adjacent to one side of the IDT 52a. The other of the pair of reflectors 52b is adjacent to the other side of the IDT 52a.

Next, a prototype of the acoustic wave device 1 according to the present embodiment and the results of short-power measurement will be described. The inventors measured the withstand power of the IDT 52a of the acoustic wave device 1 according to the present embodiment under the following conditions.

3A and 3B are diagrams schematically showing contents of a trial production according to Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view of the electrode fingers 52d of the IDT 52a.

As shown in FIG. 3, on the piezoelectric substrate 11, metal layers from the first layer to the eleventh layer forming the IDT are laminated.

As shown in FIG. 3, a bottom titanium layer 1BTi is formed as the 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 the ninth layer. An aluminum layer 10Al is formed as a tenth layer. A top titanium layer 11TTi is formed as the eleventh layer.

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

The aluminum-copper layers of the third, fifth, seventh and ninth layers have an aluminum concentration of 95% or more. Further, the third, fifth, seventh and ninth aluminum-copper layers may have a copper concentration of, for example, 1% or more. In addition, the third, fifth, seventh and ninth aluminum-copper layers have a copper concentration of, for example, 1.5% or more, 2.0% or more, or 2.5% or more. It can be less than 0%.

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

As shown in FIG. 4, in all of Prototypes 1 to 4, the thickness of the bottom titanium of the first layer was 101 nm, and the thickness of the top titanium of the 11th layer was 15 nm. Also, in any of Prototypes 1 to 4, the total thickness of the second to tenth layers was set to 301 nm.

As shown in FIG. 4, in Prototype 1, the aluminum layers of the second, fourth, sixth, eighth and tenth layers have thicknesses of 48 nm, 48 nm, 48 nm, 48 nm and 49 nm, respectively. The third, fifth, seventh and ninth aluminum-copper layers of Prototype 1 all have a thickness of 15 nm.

In Prototype 1, the total thickness of the aluminum layers of the second, fourth, sixth, eighth and tenth layers is 241 nm. The total thickness of the third, fifth, seventh and ninth aluminum-copper layers of Prototype 1 is 60 nm.

As shown in FIG. 4, in Prototype 2, the aluminum layers of the second, fourth, sixth, eighth and tenth layers have thicknesses of 44 nm, 44 nm, 44 nm, 44 nm and 45 nm, respectively. The third, fifth, seventh and ninth aluminum-copper layers of Prototype 2 all have a thickness of 20 nm.

In Prototype 2, the total thickness of the aluminum layers of the second, fourth, sixth, eighth and tenth layers is 221 nm. The total thickness of the third, fifth, seventh and ninth aluminum-copper layers of Prototype 2 is 80 nm.

As shown in FIG. 4, in Prototype 3, the second, fourth, sixth, eighth and tenth aluminum layers have thicknesses of 36 nm, 36 nm, 36 nm, 36 nm and 37 nm, respectively. The third, fifth, seventh and ninth aluminum-copper layers of Prototype 3 all have a thickness of 30 nm.

In Prototype 3, the total thickness of the aluminum layers of the second, fourth, sixth, eighth and tenth layers is 181 nm. The total thickness of the third, fifth, seventh and ninth aluminum-copper layers of Prototype 3 is 120 nm. That is, the total thickness of the second, fourth, sixth, eighth and tenth aluminum layers and the total thickness of the third, fifth, seventh and ninth aluminum-copper layers thickness ratio is 3:2 or more.

As shown in FIG. 4, in Prototype 4, the second, fourth, sixth, eighth and tenth aluminum layers have thicknesses of 28 nm, 28 nm, 28 nm, 28 nm and 29 nm, respectively. The third, fifth, seventh and ninth aluminum-copper layers of Prototype 4 all have a thickness of 40 nm.

In Prototype 4, the total thickness of the aluminum layers of the second, fourth, sixth, eighth and tenth layers is 141 nm. The total thickness of the third, fifth, seventh and ninth aluminum-copper layers of Prototype 2 is 160 nm. That is, the total thickness of the second, fourth, sixth, eighth and tenth aluminum layers and the total thickness of the third, fifth, seventh and ninth aluminum-copper layers thickness ratio is 29:32 or less.

FIG. 5 shows the results of the fuse test of prototypes 1 to 4 and a comparative example. A Band-5 duplexer was manufactured for both the prototype and the comparative example. In addition, in the comparative example, instead of the metal layers from the second layer to the tenth layer in Embodiment 1, a thickness of 301 nm, which is the same as the total thickness, has an aluminum concentration of 98.5% and a copper concentration of 1.5%. A single layer of aluminum-copper alloy was used. Other conditions are the same as in the first embodiment.

As shown in FIG. 5, the required specification of the Band-5 duplexer at the time of trial production is 30 DB, and all trial productions and comparative examples have passed the fuse test. Here, as the content of copper in the IDT increases, the power durability improves, but the insertion loss increases. The increase in insertion loss becomes more pronounced as the frequency increases.

Prototype 1 and Prototype 2 were not able to obtain as much power resistance as the comparative example, but because the copper content is less than the comparative example, the insertion loss is small and the power resistance that satisfies the required specifications can be obtained. was made.

Prototype 3 was able to obtain a withstand power close to that of the comparative example, and since the copper content was smaller than that of the comparative example, the insertion loss was small and a withstand power satisfying the required specifications could be obtained.

Prototype 4 was able to obtain a higher withstand power than the comparative example, and because it contained less copper than the comparative example, it had a small insertion loss and a withstand power that satisfied the required specifications. .

FIG. 6 is a diagram showing the results of the stress life test of Prototype 4 in Embodiment 1 and Comparative Example.

As shown in FIG. 6, both Prototype 4 and the comparative example have a power handling capability that satisfies the required specifications. In addition, prototype 4 could achieve a life that was about 10 times longer than that of the comparative example when the applied power was around 32 dBm.

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

Embodiment 2.
FIG. 7 is a longitudinal sectional view of a module to which the acoustic wave device of Embodiment 2 is applied. The same reference numerals are given to the same or corresponding parts as those of the first embodiment. Description of this part is omitted.

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. As shown in FIG.

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

For example, the integrated circuit component IC is mounted inside the wiring board 130 . An integrated circuit component IC includes a switching circuit and a low noise amplifier.

Acoustic wave device 1 is mounted on the main surface of wiring board 130 .

Inductor 111 is mounted on the main surface of wiring board 130 . Inductor 111 is implemented for impedance matching. For example, inductor 111 is an Integrated Passive Device (IPD).

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

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

Having described several aspects of at least one embodiment, it is to be appreciated 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.

It is to be understood that the method and apparatus embodiments described herein are not limited in application to the details of construction and arrangement of components set forth in the foregoing description or illustrated in the accompanying drawings. The methods and apparatus can be implemented in other embodiments and practiced or carried out in various ways.

Specific implementations are provided here for illustrative purposes only and are not intended to be limiting.

The phraseology and terminology used in this disclosure is for the purpose of description and should not be regarded as limiting. The use of "including", "comprising", "having", "including" and variations thereof herein is intended to be inclusive of the items listed below and equivalents thereof as well as additional items.

References to “or (or)” shall be construed such that any term stated using “or (or)” refers to one, more than one, and all of the terms of the statement. can be

All references to front, rear, left, right, top, bottom, top, bottom, width, length, and front and back are intended for convenience of description. Such references are not limited to any one positional or spatial orientation of the components of this disclosure. Accordingly, the above description and drawings are exemplary only.

1 Elastic wave device
3 Wiring board
5 device chip,
11 piezoelectric substrate
21 support substrate 9 electrode pad
15 Bump
16 air gap 17 sealing part
31 External connection terminal
52 elastic wave element, 52a IDT, 52b reflector, 52c comb electrode, 52d electrode finger
REFERENCE SIGNS LIST 100 module 111 inductor 117 sealing portion 130 wiring board 131 external connection terminal IC integrated circuit component

Claims (13)

a piezoelectric substrate;
and an IDT electrode formed on the piezoelectric substrate,
The IDT electrode is
a first metal layer made of a first metal having a concentration of 99% or higher;
A second metal layer made of an alloy of the first metal and the second metal having a concentration of 95% or more and less than 99%,
The first metal layer and the second metal layer are each formed in a plurality of layers,
The acoustic wave device, wherein the first metal layers and the second metal layers are alternately laminated. The acoustic wave device according to claim 1, wherein the first metal has a higher electrical resistivity than the second metal. 3. The acoustic wave device according to claim 1, wherein the total thickness of the second metal layers is thicker than the total thickness of the first metal layers. 4. The acoustic wave device according to claim 1, further comprising a bottom layer made of a third metal having higher electrical resistivity than said first metal and said second metal. The acoustic wave device according to any one of claims 1 to 4, wherein the total thickness of the first metal layer and the second metal layer is half or more and three quarters or less of the thickness of the IDT electrode. The acoustic wave device according to any one of claims 1 to 5, wherein the first metal is aluminum, molybdenum, iridium, tungsten, cobalt, nickel, or ruthenium. The acoustic wave device according to any one of claims 1 to 6, wherein the third metal is chromium, strontium or titanium. The acoustic wave device according to any one of claims 1 to 7, wherein a thickness ratio between the first metal layer and the second metal layer is 3:2 to 29:32. The acoustic wave device according to any one of claims 1 to 8, wherein the second metal layer has a concentration of the first metal of 95% or more and 97.5% or less. The acoustic wave device according to any one of claims 1 to 9, wherein the second metal layer has aluminum as the first metal and copper as the second metal. The acoustic wave device according to any one of claims 1 to 10, wherein the piezoelectric substrate is a substrate made of a single crystal of lithium niobate or lithium tantalate. A support substrate is provided on the main surface opposite to the main surface on which the IDT electrodes of the piezoelectric substrate are formed, and the support substrate is a substrate made of sapphire, silicon, alumina, spinel, crystal, or glass. 12. The acoustic wave device according to any one of 11. A module comprising the acoustic wave device according to any one of claims 1 to 12.