Elastic wave resonator, filter, and multiplexer

Abstract

To improve power durability.SOLUTION: An elastic wave resonator includes a piezoelectric substrate 10, and a plurality of electrode fingers 34 including a metal film 50 that is a titanium film or a titanium alloy film that is provided on the piezoelectric substrate 10 and is thicker than 10 nm, a metal film 54 which is an aluminum film or an aluminum alloy film provided on the metal film 50, and a barrier film 52 provided between the metal film 50 and the metal film 54 and suppressing the interdiffusion of titanium and aluminum. As a result, stress due to deformation of the piezoelectric substrate 10 is less likely to be applied to the metal film 54, and a region made of an intermetallic compound or alloy of titanium and aluminum is less likely to be formed between the metal films 50 and 54, and therefore, power durability is improved.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an elastic wave resonator, a filter, and a multiplexer.

Background Art

[0002] In a high-frequency communication system typified by a mobile phone, a high-frequency filter is used to remove unnecessary signals outside the frequency band used for communication. For example, a surface acoustic wave (SAW) resonator is used in the high-frequency filter. In the surface acoustic wave resonator, an interdigital transducer (IDT) having a plurality of electrode fingers is provided on a piezoelectric substrate such as a lithium tantalate substrate or a lithium niobate substrate. As the electrode fingers, a structure in which a titanium layer for enhancing the adhesion to the piezoelectric substrate, a mechanically stable titanium nitride layer, and an aluminum layer or an aluminum alloy layer are sequentially laminated is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a high-frequency signal is input to the IDT, deformation occurs due to the excitation of surface acoustic waves in the piezoelectric substrate, and the stress accompanying this deformation is applied to the electrode fingers. As a result, the breakdown voltage performance of the elastic wave resonator may deteriorate. In Patent Document 1, the breakdown voltage resistance is improved by providing a mechanically stable titanium nitride layer between the aluminum layer or aluminum alloy layer and the piezoelectric substrate. However, there is still room for improvement in terms of improving the breakdown voltage resistance.

[0005] The present invention has been made in view of the above problems, and an object thereof is to improve the electric power resistance.

Means for Solving the Problems

[0006] The present invention includes a plurality of electrode fingers having a piezoelectric substrate, a first metal film provided on the piezoelectric substrate and being a titanium film or a titanium alloy film thicker than 10 nm, a second metal film provided on the first metal film and being an aluminum film or an aluminum alloy film, and a barrier film provided between the first metal film and the second metal film for suppressing the mutual diffusion of titanium and aluminum, and is an elastic wave resonator provided with the same.

[0007] In the above configuration, the barrier film can be configured to be thinner than the first metal film.

[0008] In the above configuration, the thickness of the first metal film can be configured to be 1 / 3 or less of the thickness of the plurality of electrode fingers.

[0009] In the above configuration, the barrier film can be configured to have a melting point higher than the melting point of titanium.

[0010] In the above configuration, the barrier film can be configured to be a single-layer film or a laminated film of a titanium nitride film, an aluminum nitride film, a tungsten film, a molybdenum film, a silicon oxide film, a silicon nitride film, an aluminum oxide film, a tantalum film, a tantalum oxide film, or a niobium film.

[0011] In the above configuration, the barrier film can be configured to have conductivity.

[0012] In the above configuration, the barrier film can be configured to be a single-layer film or a laminated film of a tungsten oxide film, a molybdenum nitride film, a silicon film, a nickel film, a nickel alloy film, or a niobium oxide film.

[0013] In the above configuration, the piezoelectric substrate can be configured as a lithium tantalate substrate or a lithium niobate substrate.

[0014] The present invention is a filter including the elastic wave resonator described above.

[0015] The present invention is a multiplexer including the filter described above.

Advantages of the Invention

[0016] According to the present invention, the power resistance can be improved.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment

[0019] FIG. 1(a) is a plan view of the surface acoustic wave resonator 100 according to Embodiment 1, and FIG. 1(b) is a cross-sectional view taken along line A-A of FIG. 1(a). As shown in FIGS. 1(a) and 1(b), the surface acoustic wave resonator 100 is a surface acoustic wave resonator in which an IDT 30 and reflectors 40 are provided on a piezoelectric substrate 10. The reflectors 40 are provided on both sides of the IDT 30. The piezoelectric substrate 10 is bonded, for example, on a support substrate 20.

[0020] The IDT 30 includes a pair of opposing comb-shaped electrodes 32. The comb-shaped electrodes 32 include a plurality of electrode fingers 34 and a bus bar 36 to which the plurality of electrode fingers 34 are connected. The pair of comb-shaped electrodes 32 are provided to face each other such that the electrode fingers 34 are substantially staggered.

[0021] The surface acoustic wave excited by the IDT 30 mainly propagates in the arrangement direction of the electrode fingers 34. The pitch of the electrode fingers 34 is approximately equal to the wavelength λ of the surface acoustic wave. The reflectors 40 reflect the surface acoustic wave. Let the propagation direction of the surface acoustic wave be the X direction and the direction perpendicular to the propagation direction be the Y direction. The X direction and the Y direction do not necessarily correspond to the X-axis direction and the Y-axis direction of the crystal orientation of the piezoelectric substrate 10. The piezoelectric substrate 10 is, for example, a lithium tantalate substrate or a lithium niobate substrate. The support substrate 20 is, for example, a sapphire substrate, a silicon substrate, a spinel substrate, a quartz substrate, a quartz crystal substrate, an alumina substrate, or a silicon carbide substrate. Note that a protective film made of an insulating film may be provided on the piezoelectric substrate 10 so as to cover the IDT 30 and the reflectors 40.

[0022] FIG. 2 is a cross-sectional view near the electrode finger 34 in Example 1. As shown in FIG. 2, the electrode finger 34 includes a metal film 50 provided on the piezoelectric substrate 10, a barrier film 52 provided on the metal film 50, and a metal film 54 provided on the barrier film 52. The metal film 50 is a titanium film or a titanium alloy film and has a thickness greater than 10 nm. The titanium alloy film has materials such as copper and aluminum added to titanium, but the addition amount is less than 10 wt% (weight percentage concentration) (for example, 3 wt% or less). The metal film 54 is an aluminum film or an aluminum alloy film. The aluminum alloy film has materials such as copper and silicon added to aluminum, but the addition amount is less than 10 wt% (for example, 3 wt% or less). By providing the metal film 50, which is a titanium film or a titanium alloy film, between the piezoelectric substrate 10 and the barrier film 52, the adhesion between the piezoelectric substrate 10 and the electrode finger 34 is improved. Since the metal film 54 is mainly a layer through which current flows, it preferably has a low electrical resistivity. By using an aluminum film or an aluminum alloy film for the metal film 54, the electrical resistivity is reduced.

[0023] The barrier film 52 is a film that suppresses the interdiffusion between titanium contained in the metal film 50 and aluminum contained in the metal film 54. The barrier film 52 is formed of, for example, titanium nitride (TiN), aluminum nitride (AlN), tungsten (W), tungsten oxide (WO3), molybdenum (Mo), molybdenum nitride (Mo2N), silicon (Si), silicon oxide (SiO2), silicon nitride (SiN), nickel (Ni), nickel alloy (for example, nichrome), aluminum oxide (Al2O3), tantalum (Ta), tantalum oxide (Ta2O5), niobium (Nb), or niobium oxide (Nb2O5).

[0024] The barrier film 52 is thinner than the metal film 50 and the metal film 54, and is, for example, 2 nm or more and 20 nm or less. For example, the thickness of the barrier film 52 is 1 / 3 or less of the thickness of the metal film 50, and may be 1 / 4 or less. The metal film 54 is thicker than the metal film 50. For example, the thickness of the metal film 54 is 1.3 times or more of the thickness of the metal film 50, and may be 1.5 times or more.

[0025] [Manufacturing Method] The surface acoustic wave resonator 100 according to Example 1 is manufactured by the following method. First, a support substrate 20 with a flat surface is prepared. The arithmetic mean roughness Ra of the surface of the support substrate 20 is, for example, 1 nm or less. The piezoelectric substrate 10 is bonded to the upper surface of the support substrate 20 using, for example, the surface activation method. Then, the upper surface of the piezoelectric substrate 10 is polished using, for example, the CMP (Chemical Mechanical Polishing) method to thin the piezoelectric substrate 10 to a desired thickness. Next, the IDT 30 and the reflector 40 are formed on the piezoelectric substrate 10 using, for example, the sputtering method and the etching method. The IDT 30 and the reflector 40 may be formed by the lift-off method. Thereby, the surface acoustic wave resonator 100 according to Example 1 is formed.

[0026] [Comparative Example] FIG. 3(a) is a cross-sectional view near the electrode finger 34 in Comparative Example 1, and FIG. 3(b) is a cross-sectional view near the electrode finger 34 in Comparative Example 2. As shown in FIG. 3(a), the electrode finger 34 in Comparative Example 1 is composed of only a metal film 54 which is an aluminum film or an aluminum alloy film. As shown in FIG. 3(b), the electrode finger 34 in Comparative Example 2 is composed of a metal film 50 which is a titanium film or a titanium alloy film and a metal film 54 which is an aluminum film or an aluminum alloy film. The metal film 50 functions as an adhesion film.

[0027] [Experiment] Filters were fabricated using the surface acoustic wave resonators according to Comparative Example 1 and Comparative Example 2, and a power resistance test was conducted. The test was performed on a ladder-type filter (Sample A) fabricated using the surface acoustic wave resonator according to Comparative Example 1 and ladder-type filters (Samples B and C) fabricated using the surface acoustic wave resonator according to Comparative Example 2. Sample A Support substrate 20: Sapphire substrate Piezoelectric substrate 10: Lithium tantalate substrate Metal film 54: Aluminum alloy (1.0 wt% copper added to aluminum) film Sample B Support substrate 20: Sapphire substrate Piezoelectric substrate 10: Lithium tantalate substrate Metal film 50: Titanium film with a thickness of 10 nm Metal film 54: Aluminum alloy (1.0 wt% copper added to aluminum) film Sample C Support substrate 20: Sapphire substrate Piezoelectric substrate 10: Lithium tantalate substrate Metal film 50: Titanium film with a thickness of 60 nm Metal film 54: Aluminum alloy (1.0 wt% copper added to aluminum) film

[0028] Figure 4(a) is a diagram showing the output power with respect to the input power for Samples A, B, and C, and Figure 4(b) is a diagram showing the change amount of the output power with respect to time. Figure 4(a) is the result of a linearity test in which the input power is gradually increased and the input power when the output power stops being output is measured. Figure 4(b) is the result of a life test in which the input power is fixed and the degradation time is measured based on the change amount of the output power. In Figure 4(a) and Figure 4(b), the test results of Sample A are shown by a dotted line, the test results of Sample B are shown by a dashed-dotted line, and the test results of Sample C are shown by a broken line. Also, in Figure 4(a), two samples of Sample A and Sample B are fabricated respectively, and six samples of Sample C are fabricated, and the respective test results are shown.

[0029] As shown in Figure 4(a), in Sample A, the electrode finger 34 was damaged when the input power was not very large, and the output power stopped being output. In Sample B, the input power when the output power stopped being output was larger than that in Sample A. In Sample C, within the range of the input power of this test, the output of the output power was maintained without the electrode finger 34 being damaged.

[0030] As shown in Figure 4(b), in Sample A, the output power changed significantly after a certain period of time from the start of the test, while in Samples B and C, the output power did not change significantly within the time of this test.

[0031] As shown in FIGS. 4(a) and 4(b), the power resistance of sample B was higher than that of sample A, and the power resistance of sample C was higher than that of sample B. The reason can be considered as follows. When a high-frequency signal with a large power is input to IDT30, an elastic surface wave is excited in the piezoelectric substrate 10. As a result, deformation due to vibration occurs in the piezoelectric substrate 10, and the stress associated with this deformation is applied to the electrode fingers 34. The metal film 54, which is an aluminum film or an aluminum alloy film, is considered to be not very resistant to the stress associated with the deformation of the piezoelectric substrate 10. In sample A, since the electrode fingers 34 are composed only of the metal film 54, it is considered that the power resistance is low. On the other hand, in sample B, a metal film 50, which is a titanium film with a thickness of 10 nm, is provided between the piezoelectric substrate 10 and the metal film 54. In sample C, a metal film 50, which is a titanium film with a thickness of 60 nm, is provided between the piezoelectric substrate 10 and the metal film 54. Since titanium is harder than aluminum (Young's modulus of titanium: 120 GPa, Young's modulus of aluminum: 70 GPa), the metal film 50 is considered to be more resistant to the stress associated with the deformation of the piezoelectric substrate 10 than the metal film 54. The thicker the metal film 50 is, the more difficult it is for the stress associated with the deformation of the piezoelectric substrate 10 to be applied to the metal film 54. Therefore, it is considered that the power resistance of sample B is improved compared to sample A, and the power resistance of sample C is improved compared to sample B. From the results of FIG. 4(a), it can be said that in order to improve the power resistance, the thickness of the metal film 50 is preferably greater than 10 nm.

[0032] However, it was found that when the metal film 50 is a titanium film or a titanium alloy film thicker than 10 nm, a large diffusion region is formed in which titanium contained in the metal film 50 and aluminum contained in the metal film 54 diffuse into each other. This will be explained with reference to the drawings. FIGS. 5(a) and 5(b) are cross-sectional views schematically showing a cross-sectional SEM (Scanning Electron Microscope) image of the electrode fingers 34 of sample C. FIG. 5(a) shows the electrode fingers 34 before the power resistance test, and FIG. 5(b) shows the state immediately before the electrode fingers 34 are damaged after the power resistance test.

[0033] As shown in FIG. 5(a), before the power resistance test, the electrode finger 34 had a clear two-layer structure with the interface between the metal film 50 and the metal film 54. As shown in FIG. 5(b), just before the breakdown occurred in the electrode finger 34 after the power resistance test, the interface between the metal film 50 and the metal film 54 became unclear, and a region 56 was formed between the metal film 50 and the metal film 54. It is considered that the region 56 is a region composed of an intermetallic compound or alloy of titanium and aluminum formed by the mutual thermal diffusion of titanium contained in the metal film 50 and aluminum contained in the metal film 54 due to the input of a high-power high-frequency signal to the IDT 30 and the resulting heat generation of the electrode finger 34. The thickness of the region 56 was, for example, about 10 nm to 15 nm.

[0034] When a region 56 composed of an intermetallic compound or alloy of titanium and aluminum is formed between the metal film 50 and the metal film 54, the electrical resistance of the electrode finger 34 increases. For example, the electrical resistivity of titanium is 420 nΩ·m, the electrical resistivity of aluminum is 28.2 nΩ·m, and the electrical resistivity of the intermetallic compound or alloy of titanium and aluminum is about 58 nΩ·m. Therefore, when a high-power high-frequency signal is input to the IDT 30, the temperature rise of the electrode finger 34 becomes large, and the electrode finger 34 may be deformed and / or broken such as blown, and sufficient power resistance cannot be ensured. In recent years, with the increase in the frequency of the surface acoustic wave resonator, the width of the electrode finger 34 has become narrower. Therefore, when a region 56 composed of an intermetallic compound or alloy of titanium and aluminum is formed, the temperature rise of the electrode finger 34 becomes even larger. Thus, it has been found that it is difficult to sufficiently ensure the power resistance of the electrode finger 34 only by providing the metal film 50 thicker than 10 nm between the piezoelectric substrate 10 and the metal film 54.

[0035] Therefore, in Example 1, a barrier film 52 that suppresses the mutual diffusion of titanium and aluminum is provided between the metal film 50 and the metal film 54.

[0036] [Experiment] Filters were fabricated using the surface acoustic wave resonators according to Example 1 and Comparative Example 2, and a power resistance test was performed. The tests were conducted on a ladder filter (Sample D) fabricated using the surface acoustic wave resonator according to Example 1 and a ladder filter (Sample E) fabricated using the surface acoustic wave resonator according to Comparative Example 2. Sample D Support substrate 20: Sapphire substrate Piezoelectric substrate 10: Lithium tantalate substrate Metal film 50: Titanium film with a thickness of 50 nm Barrier film 52: Titanium nitride film with a thickness of 10 nm Metal film 54: Aluminum alloy (1.0 wt% copper added to aluminum) film Sample E Support substrate 20: Sapphire substrate Piezoelectric substrate 10: Lithium tantalate substrate Metal film 50: Titanium film with a thickness of 60 nm Metal film 54: Aluminum alloy (1.0 wt% copper added to aluminum) film

[0037] FIG. 6(a) is a diagram showing the output power with respect to the input power in Samples D and E, and FIG. 6(b) is a diagram showing the change amount of the output power with respect to time. FIG. 6(a) is the result of a linearity test in which the input power is gradually increased and the input power when the output power stops being output is measured. FIG. 6(b) is the result of a life test in which the input power is left fixed and the degradation time is measured based on the change amount of the output power. In FIGS. 6(a) and 6(b), the test results of Sample D are shown by solid lines, and the test results of Sample E are shown by broken lines. Also, in FIG. 6(a), two each of Samples D and E were fabricated, and the respective test results are shown. Note that FIGS. 6(a) and 6(b) have different scales on the horizontal and vertical axes compared to FIGS. 4(a) and 4(b).

[0038] As shown in Fig. 6(a), for sample D, the input power when the output power stopped being output was higher than that of sample E. As shown in Fig. 6(b), for sample D, the time until the output power changed significantly was longer than that of sample E.

[0039] From the test results of Fig. 6(a) and Fig. 6(b), it can be seen that sample D has higher power resistance than sample E. The reason for the improved power resistance of sample D can be considered as follows. In sample D, a barrier film 52 is provided between the metal film 50 and the metal film 54. Therefore, it is considered that the mutual thermal diffusion between the titanium contained in the metal film 50 and the aluminum contained in the metal film 54 is suppressed, and the formation of a region composed of an intermetallic compound or alloy of titanium and aluminum between the metal film 50 and the metal film 54 is suppressed. As a result, the increase in the electrical resistance of the electrode finger 34 is suppressed, and even when a high-power high-frequency signal is input to the IDT 30, the temperature rise of the electrode finger 34 is suppressed, so the power resistance is improved.

[0040] As described above, according to Example 1, the electrode finger 34 includes a metal film 50 (first metal film), which is a titanium film or a titanium alloy film thicker than 10 nm, between the piezoelectric substrate 10 and a metal film 54 (second metal film), which is an aluminum film or an aluminum alloy film. Thereby, it becomes difficult for the stress accompanying the deformation of the piezoelectric substrate 10 to be applied to the metal film 54, so that the power resistance can be improved. Further, the electrode finger 34 includes a barrier film 52 that suppresses the mutual diffusion of titanium and aluminum between the metal film 50 and the metal film 54. Thereby, the formation of a region composed of an intermetallic compound or alloy of titanium and aluminum between the metal film 50 and the metal film 54 is suppressed, so that the breakage accompanying the increase in the electrical resistance of the electrode finger 34 is suppressed. Therefore, the power resistance can be improved.

[0041] The thickness of the metal film 50 is preferably 20 nm or more, more preferably 30 nm or more, and still more preferably 40 nm or more, so that the stress accompanying the deformation of the piezoelectric substrate 10 is less likely to be applied to the metal film 54.

[0042] The metal film 54, which is an aluminum film or an aluminum alloy film, is thicker than the metal film 50, which is a titanium film or a titanium alloy film. Since the metal film 54 is mainly the layer through which current flows, increasing the thickness of the metal film 54 can suppress an increase in the electrical resistance of the electrode finger 34. From the perspective of suppressing an increase in the electrical resistance of the electrode finger 34, the metal film 54 preferably has a thickness that is 1.5 times or more that of the metal film 50, more preferably 2.0 times or more, and even more preferably 2.5 times or more.

[0043] The barrier film 52 is thinner than the metal film 50. This also enables the metal film 54 to be made thicker, thereby suppressing an increase in the electrical resistance of the electrode finger 34. Also, since the barrier film 52 is thinner than the metal film 50, conversely, an effect of reducing the resistance of the electrode finger 34 can be obtained as compared with the case where the metal film 50 is thinner than the barrier film 52. From the perspective of suppressing an increase in the electrical resistance of the electrode finger 34, the barrier film 52 preferably has a thickness that is 1 / 3 or less that of the metal film 50, more preferably 1 / 4 or less, and even more preferably 1 / 5 or less. From the perspective of suppressing the mutual diffusion of titanium and aluminum, the barrier film 52 preferably has a thickness of 2 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more.

[0044] The thicker the metal film 50, which is a titanium film or a titanium alloy film, the less likely the metal film 54, which is an aluminum film or an aluminum alloy film, is to be affected by the stress accompanying the deformation of the piezoelectric substrate 10. However, as the metal film 50 becomes thicker, the metal film 54 becomes relatively thinner, so that the electrical resistance of the electrode finger 34 increases and the characteristics deteriorate. Therefore, the thickness of the metal film 50 is preferably 1 / 3 or less, more preferably 1 / 4 or less, and even more preferably 1 / 5 or less of the thickness of the electrode finger 34. For example, the thickness of the metal film 50 is preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 60 nm or less.

[0045] The barrier film 52 preferably has a melting point higher than the melting point of titanium (1668 °C). It is considered that a material with a high melting point has a high binding energy between atoms, is thermodynamically stable, and has a high barrier property against mutual diffusion. Therefore, by having a melting point higher than that of titanium, the mutual diffusion between the titanium of the metal film 50 and the aluminum of the metal film 54 can be effectively suppressed. Examples of materials that have a melting point higher than that of titanium and can be used as the barrier film 52 include titanium nitride (melting point: 2930 °C), aluminum nitride (melting point: 2200 °C), tungsten (melting point: 3422 °C), molybdenum (melting point: 2623 °C), silicon oxide (melting point: 1710 °C), silicon nitride (melting point: 1900 °C), aluminum oxide (melting point: 2072 °C), tantalum (melting point: 3017 °C), tantalum oxide (melting point: 1872 °C), and niobium (melting point: 2477 °C). Therefore, the barrier film 52 may be a single-layer film or a laminated film of these. These films may contain impurities on the order of several wt%. Note that the melting point of aluminum is 660.3 °C.

[0046] Further, the barrier film 52 may have insulating properties, but preferably has conductive properties. Thereby, an increase in the electrical resistance of the electrode finger 34 can be suppressed, and deterioration of characteristics can be suppressed. Examples of materials that have conductive properties and can be used as the barrier film 52 include nickel (melting point: 1455 °C) in addition to the above-mentioned titanium nitride, tungsten, molybdenum, tantalum, and niobium. Therefore, the barrier film 52 may be a single-layer film or a laminated film of these. These films may contain impurities on the order of several wt%.

[0047] Since the barrier film 52 only needs to have the property of suppressing the mutual diffusion between titanium and aluminum, in addition to the above, for example, a tungsten oxide film, a molybdenum nitride film, a silicon film, a niobium oxide film, or a nickel alloy film such as nichrome may be used. These films may contain impurities on the order of several wt%.

[0048] In Example 1, the case where the piezoelectric substrate 10 is bonded to the support substrate 20 was shown. However, it may be the case where the piezoelectric substrate 10 is not bonded to the support substrate 20 and is a single piezoelectric substrate 10. Also, an insulating layer such as silicon oxide, aluminum oxide, and / or aluminum nitride may be provided between the piezoelectric substrate 10 and the support substrate 20.

Example

[0049] FIG. 7 is a circuit diagram of the filter 200 according to Example 2. As shown in FIG. 7, in the filter 200, one or more series resonators S1 to S4 are connected in series between the input terminal Tin and the output terminal Tout, and one or more parallel resonators P1 to P3 are connected in parallel. The elastic wave resonator 100 according to Example 1 can be used for at least one resonator of one or more series resonators S1 to S4 and one or more parallel resonators P1 to P3. The number of resonators of the ladder-type filter and the like can be set as appropriate.

Example

[0050] FIG. 8 is a block diagram of the duplexer 300 according to Example 3. As shown in FIG. 8, in the duplexer 300, a transmission filter 60 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 62 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 60 passes a signal in the transmission band among the signals input from the transmission terminal Tx as a transmission signal to the common terminal Ant and suppresses signals of other frequencies. The reception filter 62 passes a signal in the reception band among the signals input from the common terminal Ant as a reception signal to the reception terminal Rx and suppresses signals of other frequencies. At least one of the transmission filter 60 and the reception filter 62 can be the filter 200 according to Example 2.

[0051] In Example 3, a duplexer was shown as an example of the multiplexer, but it may be a triplexer or a quadplexer.

[0052] As described in detail above regarding the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0053] 10 Piezoelectric substrate 20 Support substrate 30 IDT 32 Comb-shaped electrode 34 Electrode finger 36 Bus bar 40 Reflector 50 Metal film 52 Barrier film 54 Metal film 56 Region 60 Transmitting filter 62 Receiving filter 100 Surface acoustic wave resonator 200 Filter 300 Duplexer

Claims

1. A piezoelectric substrate, a first metal film provided on the piezoelectric substrate and being a titanium film or a titanium alloy film with a thickness greater than 10 nm, a second metal film provided on the first metal film and being an aluminum film or an aluminum alloy film, and a barrier film provided between the first metal film and the second metal film for suppressing the mutual diffusion of titanium and aluminum, and a plurality of electrode fingers having the same; an elastic wave resonator.

2. The elastic wave resonator according to claim 1, wherein the barrier film is thinner than the first metal film.

3. The elastic wave resonator according to claim 1 or 2, wherein the thickness of the first metal film is 1 / 3 or less of the thickness of the plurality of electrode fingers.

4. The elastic wave resonator according to any one of claims 1 to 3, wherein the barrier film has a melting point higher than the melting point of titanium.

5. The elastic wave resonator according to any one of claims 1 to 4, wherein the barrier film is a single-layer film or a laminated film of a titanium nitride film, an aluminum nitride film, a tungsten film, a molybdenum film, a silicon oxide film, a silicon nitride film, an aluminum oxide film, a tantalum film, a tantalum oxide film, or a niobium film.

6. The elastic wave resonator according to any one of claims 1 to 4, wherein the barrier film has conductivity.

7. The elastic wave resonator according to any one of claims 1 to 3, wherein the barrier film is a single-layer film or a laminated film of a tungsten oxide film, a molybdenum nitride film, a silicon film, a nickel film, a nickel alloy film, or a niobium oxide film.

8. The elastic wave resonator according to any one of claims 1 to 7, wherein the piezoelectric substrate is a lithium tantalate substrate or a lithium niobate substrate.

9. A filter including the elastic wave resonator according to any one of claims 1 to 8.

10. A multiplexer including the filter according to claim 9.

Images