JP7033010B2 - Elastic wave devices, filters and multiplexers - Google Patents

Description

The present invention relates to elastic wave devices, filters and multiplexers, for example elastic wave devices having comb-shaped electrodes, filters and multiplexers.

In a high frequency communication system represented by a mobile phone, a high frequency filter or the like is used to remove unnecessary signals other than the frequency band used for communication. A surface acoustic wave device having a surface acoustic wave (SAW) element or the like is used for a high frequency filter or the like. The SAW element is an element in which an IDT (Interdigital Transducer) having a pair of comb-shaped electrodes is formed on a piezoelectric substrate (for example, Patent Documents 1 to 5). It is known that the speed of sound of a surface acoustic wave excited by IDT is made slower than the speed of sound of a bulk wave propagating in a piezoelectric substrate to reduce the loss (for example, Patent Document 6).

JP-A-2015-89069 Japanese Unexamined Patent Publication No. 2001-267868 JP-A-2017-157944 Japanese Unexamined Patent Publication No. 9-46168 Japanese Patent Application Laid-Open No. 2003-78384 Japanese Unexamined Patent Publication No. 2016-136712

When a refractory metal is used for the comb-shaped electrode in order to slow down the sound velocity of the surface acoustic wave as in Patent Document 6, the comb-shaped electrode is formed by the stress during film formation of the metal film and / or the thermal stress due to heat generation during operation. The electrodes may come off the piezoelectric substrate.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress stress applied to a comb-shaped electrode.

The present invention comprises a piezoelectric substrate and a plurality of electrode fingers provided on the piezoelectric substrate and having a melting point equal to or higher than the melting point of platinum as a main component, and the plurality of electrode fingers are formed by a single layer of a metal film. The plurality of electrode fingers are provided with a pair of comb-shaped electrodes having a hem portion provided outside the side surface in the arrangement direction of the plurality of electrode fingers, and the hem portion is the plurality of electrodes . The piezoelectric substrate is provided outside the first position where the flat surface in contact with the steepest portion of the side surface of the electrode finger and the surfaces of the plurality of electrode fingers on the piezoelectric substrate intersect with each other, and passes through the first position. The height of the piezoelectric substrate from the surface at the second position where the straight line perpendicular to the surface of the electrode intersects the side surface of the electrode finger is 0.2 times or less the maximum height of the plurality of electrode fingers. It is a wave device.

In the above configuration, the surface of the plurality of electrode fingers opposite to the piezoelectric substrate may be configured to include a flat surface .

In the above configuration, the width of the hem portion in the arrangement direction may be 0.05 times or more the width of the plurality of electrode fingers in the arrangement direction.

In the above configuration, the height may be 0.1 times or less the height of the plurality of electrode fingers.

In the above configuration, the plurality of electrode fingers may be configured to contain any one of molybdenum, iridium, platinum, rhenium, rhodium, ruthenium, tantalum and tungsten as a main component.

In the above configuration, the plurality of electrode fingers and the hem portion may be configured to be in contact with the piezoelectric substrate.

In the above configuration, a metal film provided on the plurality of electrode fingers and having a metal as a main component different from that of the main components of the plurality of electrode fingers can be provided.

In the above configuration, the plurality of electrode fingers have a first region provided on the piezoelectric substrate and including the hem portion, and a second region provided on the first region, and the first region is , Amorphous or can be configured to have crystal grains smaller than the crystal grains in the second region.

The present invention is a filter including the above elastic wave device.

In the above configuration, a plurality of series resonators connected between the input terminal and the output terminal, one end connected to the path between the input terminal and the output terminal, and the other end connected to the ground. The plurality of series resonators and the plurality of parallel resonators are a plurality of elastic wave resonators each having the pair of comb-shaped electrodes , and among the plurality of series resonators. The ratio of the width of the hem to the width of the plurality of electrode fingers in the array direction in the series resonator closest to the input terminal is other than the closest series resonator among the plurality of series resonators. The ratio in the parallel resonator larger than the ratio in the series resonator and / or the parallel resonator closest to the input terminal among the plurality of parallel resonators is other than the closest parallel resonator among the plurality of parallel resonators. The configuration can be larger than the above ratio in the parallel resonator of .

The present invention is a multiplexer including the above filter.

According to the present invention, the stress applied to the comb-shaped electrode can be suppressed.

1 (a) is a plan view showing an elastic wave resonator in Example 1, and FIG. 1 (b) is a sectional view taken along the line AA of FIG. 1 (a). FIG. 2 is an enlarged plan view of the elastic wave resonator according to the first embodiment. 3 (a) to 3 (d) are cross-sectional views of the electrode fingers in the first embodiment. 4 (a) to 4 (d) are cross-sectional views showing a method of manufacturing an elastic wave resonator according to the first embodiment. 5 (a) and 5 (b) are cross-sectional views of the electrode fingers of the samples A and B used in the simulation. 6 (a) and 6 (b) are simulation results of samples A and B, respectively. 7 (a) and 7 (b) are cross-sectional views showing the electrode fingers in Comparative Examples 1 and 2, respectively. 8 (a) and 8 (b) are cross-sectional views of the electrode fingers in the modified examples 1 and 2 of the first embodiment, respectively. 9 (a) is a circuit diagram of the filter according to the second embodiment, and FIG. 9 (b) is a circuit diagram of the duplexer according to the first modification of the second embodiment. 10 (a) and 10 (b) are cross-sectional views of the electrode fingers of the filter according to the second modification of the second embodiment.

Hereinafter, examples of the present invention will be described with reference to the drawings.

An elastic wave resonator will be described as an example as an elastic wave device. 1 (a) is a plan view showing an elastic wave resonator in Example 1, and FIG. 1 (b) is a sectional view taken along the line AA of FIG. 1 (a). The arrangement direction of the electrode fingers 14 is the X direction, the stretching direction of the electrode fingers 14 is the Y direction, and the normal direction of the piezoelectric substrate 10 is the Z direction. The X, Y and Z directions do not always match the crystal orientation of the piezoelectric substrate 10.

As shown in FIGS. 1 (a) and 1 (b), the elastic wave resonator 24 has an IDT 20 and a reflector 22. The IDT 20 and the reflector 22 are provided on the piezoelectric substrate 10. The piezoelectric substrate 10 is, for example, a lithium tantalate substrate, a lithium niobate substrate, or a quartz substrate. The IDT 20 and the reflector 22 are formed of a metal film 12. The metal film 12 is, for example, a molybdenum (Mo) film. The IDT 20 has a pair of comb-shaped electrodes 18. Each of the pair of comb-shaped electrodes 18 has a plurality of electrode fingers 14 and a bus bar 16 to which the plurality of electrode fingers 14 are connected. The electrode fingers 14 of one comb-shaped electrode 18 and the electrode fingers 14 of the other comb-shaped electrode 18 are provided alternately at least in part. Reflectors 22 are formed on both sides of the IDT 20 in the X direction. The elastic wave excited by the IDT 20 propagates mainly in the X direction, and the reflector 22 reflects the elastic wave. Let λ be the pitch of the electrode fingers 14 in the same comb-shaped electrode 18. λ corresponds to the wavelength of the surface acoustic wave excited by the IDT 20.

The piezoelectric substrate 10 may be bonded on a support substrate such as a silicon substrate, a sapphire substrate, an alumina substrate, a spinel substrate, a glass substrate, or a crystal substrate. Further, an insulating film such as a silicon oxide film or a silicon nitride film may be provided so as to cover the metal film 12. The film thickness of the insulating film may be thicker or thinner than the film thickness of the metal film 12.

FIG. 2 is an enlarged plan view of the elastic wave resonator according to the first embodiment. As shown in FIG. 2, a hem portion 15 is provided around the electrode finger 14 and the bus bar 16.

3 (a) to 3 (d) are cross-sectional views of the electrode fingers in the first embodiment. As shown in FIG. 3A, the electrode fingers 14 have hem portions 15 in contact with the piezoelectric substrate 10 at both ends in the X direction. The cross-sectional shape of the electrode finger 14 is rectangular, and the shape of the hem 15 is rectangular. The angle θ1 between the side surface 30 of the electrode finger 14 and the upper surface of the piezoelectric substrate 10 is about 90 °, and the angle θ2 between the side surface 31 of the hem 15 and the upper surface of the piezoelectric substrate 10 is about 90 °. The hem portion 15 is an outer portion of the line L1 in which the side surface 30 of the electrode finger 14 is in contact with the upper surface of the piezoelectric substrate 10.

In FIGS. 3 (b) and 3 (c), the cross-sectional shape of the electrode finger 14 is trapezoidal. The angle θ1 is an acute angle. In FIGS. 3 (b) and 3 (c), the angle θ2 is about 90 ° and an acute angle, respectively.

In FIG. 3D, the side surface 30 of the electrode finger 14 is not a flat surface. The angle θ1 formed by the flat surface 32 including the portion of the side surface 30 of the electrode finger 14 that is most inclined with respect to the upper surface of the piezoelectric substrate 10 and the piezoelectric substrate 10 is an acute angle. The hem portion 15 is an outer portion of the line L1 in which the flat surface 32 is in contact with the upper surface of the piezoelectric substrate 10.

As shown in FIGS. 3A to 3D, the width of the electrode finger 14 including the hem 15 in the X direction is W4. The highest height of the electrode finger 14 is H1. The width W5 of the hem portion 15 is between the line L1 and the end portion of the hem portion 15. The height of the line passing through the wire L1 and perpendicular to the upper surface of the piezoelectric substrate 10 and intersecting the side surface 30 of the electrode finger 14 from the upper surface of the piezoelectric substrate 10 is the height H2 of the hem portion 15.

4 (a) to 4 (d) are cross-sectional views showing a method of manufacturing an elastic wave resonator according to the first embodiment. As shown in FIG. 4A, the additional film 34 is formed on the piezoelectric substrate 10. The additional film 34 is, for example, a silicon oxide film, a silicon nitride film, a silicon carbide film, an insulating film such as a tantalum oxide film or a niobium oxide film, a metal film such as an aluminum film, or a conductor film such as a silicon film. The additional film 34 is formed by using, for example, a vacuum deposition method, a sputtering method, or a CVD (Chemical Vapor Deposition) method.

As shown in FIG. 4B, a mask layer 36 having an opening 35 is formed on the additional film 34. The mask layer 36 is, for example, a photoresist, and is formed by coating, exposing, and developing.

As shown in FIG. 4 (c), the additional film 34 is removed by using the mask layer 36 as a mask. For the removal of the additional film 34, for example, a wet etching method or a dry etching method is used. At this time, the additional film 34 is side-etched. The side surface of the additional film 34 is provided inside the side surface of the mask layer 36. Overhangs 37 without an additional film 34 are formed between the mask layer 36 and the piezoelectric substrate 10 at both ends of the mask layer 36.

As shown in FIG. 4D, the metal film 12 is formed on the piezoelectric substrate 10 in the opening 35 and on the mask layer 36. For the formation of the metal film 12, for example, a vacuum vapor deposition method is used. A thick metal film 12 is formed in the opening 35 to serve as an electrode finger 14. The upper surface of the piezoelectric substrate 10 in the overhang 37 is behind the mask layer 36, but a thin metal film 12 is formed due to the metal atoms wrapping around to form the hem portion 15. By removing the mask layer 36, the metal film 12 on the mask layer 36 is lifted off, and the electrode finger 14 having the hem portion 15 is formed.

When the speed of sound of the surface acoustic wave excited by the IDT 20 is faster than the speed of sound of the bulk wave (for example, the slowest transverse wave bulk wave) propagating in the piezoelectric substrate 10, the surface acoustic wave radiates the bulk wave on the surface of the piezoelectric substrate 10. Propagate. Therefore, a loss occurs. In particular, the speed of sound of SH (Shear Horizontal) waves, which are a type of surface acoustic waves, is faster than the speed of sound of bulk waves. Therefore, the loss becomes large in the elastic wave resonator whose main mode is SH wave. For example, in a Y-cut X-propagated lithium tantalate substrate having a cut angle of 20 ° or more and 48 ° or less, the SH wave is the main mode.

In order to slow down the speed of sound of surface acoustic waves, a metal having a large acoustic impedance is used for the metal film 12. The acoustic impedance Z is expressed by the following equation, where ρ is the density, E is the Young's modulus, and Pr is the Poisson's ratio.

Since the Poisson's ratio does not differ greatly between metal materials, a metal with a large acoustic impedance is a metal with a large density x Young's modulus. The density is large for metals with a large atomic number, and the Young's modulus is large for hard metals. Such a metal is a high melting point metal having a high melting point. As described above, when the refractory metal is used for the metal film 12, the speed of sound of the surface acoustic wave becomes slow and the loss becomes small.

Further, since the refractory metal has a large number of electrons and a small atomic radius, the metal bond becomes strong. Electromigration and stress migration are phenomena in which metal atoms move due to electric fields and stress, respectively. Therefore, these migrations are unlikely to occur in refractory metals with strong metal bonds. Therefore, when a refractory metal is used for the metal film 12, migration becomes small.

For example, Al (aluminum), which is generally used as a metal film 12, has a melting point of 660 ° C., and has a density, Young's modulus, Poisson's ratio, and acoustic impedance of 2.7 g / cm ³ , 68 GPa, 0.34, and 8. It is 3 GPa · s / m. Mo (molybdenum), which is a refractory metal, has a melting point of 2622 ° C. and has a density, Young's modulus, Poisson's ratio and acoustic impedance of 10.2 g / cm ³ , 329 GPa, 0.31 and 35.9 GPa · s / m, respectively. Is. As described above, Mo has a melting point 2000 ° C. higher than Al, a density of about 4 times, a Young's modulus of about 5 times, and an acoustic impedance of about 4 times.

Table 1 is a table showing the density and melting point of the refractory metal.

As shown in Table 1, the melting points of Ir (iridium), Mo, Os (osmium), Pt, Re (renium), Rh (rodium), Ru (ruthenium) and W (tungsten) are Pt melting points of 1774 ° C or higher. be. The density is more than 4 times that of Al.

As described above, the high melting point metal having a melting point of Pt or higher has a high density and a high acoustic impedance. Therefore, by using these metals as the metal film 12, the speed of sound of surface acoustic waves becomes slower, and loss can be suppressed. Moreover, since the melting point is high, migration is less likely to occur.

However, the high melting point metal tends to have a large stress. Further, the adhesion between the piezoelectric substrate 10 and the metal film 12 tends to be low. Therefore, the metal film 12 is peeled off due to the stress at the time of film formation and / or the thermal stress due to the heat generated during the operation of the elastic wave device.

[simulation]
The stress due to the cross-sectional shape of the electrode finger 14 was simulated. 5 (a) and 5 (b) are cross-sectional views of the electrode fingers of the samples A and B used in the simulation. As shown in FIGS. 5A and 5B, in the simulation, the electrode finger 14 was virtually divided into a portion 14b of the pedestal and a portion 14a on the portion 14b. In reality, the portions 14a and 14b are integrated and are made of the same metal film.

As shown in FIG. 5A, in the sample A, the cross-sectional shape of the portion 14a is trapezoidal, and the cross-sectional shape of the portion 14b is rectangular. The width of the upper surface of the portion 14a is W1, the width of the lower surface is W2, and the angle formed by the measuring surface and the lower surface is θ1. The portion 14b extends outward from the portion 14a, and the width of the extension is W3. That is, the width of the portion 14b is W4 = W2 + 2 × W3. The hem portion 15 is outside the portion 14a of the portion 14b. The height of the portion 14b is H2, and the height of the electrode finger 14 is H1.

As shown in FIG. 5B, in sample B, the cross-sectional shape of the portion 14b is trapezoidal. The width of the upper surface of the portion 14b is W2, and the width of the lower surface is W4 = W2 + 2 × W3. The angle formed by the measuring surface and the lower surface is θ2. Other configurations are the same as in sample A.

The simulation conditions are shown below.
Piezoelectric substrate 10: 42 ° rotation Y cut X propagation Lithium tantalate substrate Metal film 12: Mo
Sample A
Width W2: 1000 nm
Height H1: 500 nm
Height H2: 100 nm
Angle θ1: 70 °
Sample B
Width W2: 1000 nm
Height H1: 500 nm
Height H2: 100 nm
Angle θ1: 70 ° or 90 °

The change in stress in the X direction when the temperature rose from 20 ° C to 85 ° C was calculated using the finite element method. 6 (a) and 6 (b) are simulation results of samples A and B, respectively. The maximum stresses in FIGS. 6 (a) and 6 (b) indicate the highest stress on the top surface of the piezoelectric substrate 10 and are in the region 50 (end of portion 14b) of FIGS. 5 (a) and 5 (b). It is stress.

As shown in FIG. 6A, in sample A, the absolute value of the maximum stress decreases as the width W3 increases. As shown in FIG. 6B, in sample B, the absolute value of the maximum stress decreases as the angle θ2 decreases. A smaller θ2 corresponds to a larger width W3. Since the electrode finger 14 has the hem portion 15 as in the samples A and B, the stress applied to the piezoelectric substrate 10 from the electrode finger 14 can be reduced.

7 (a) and 7 (b) are cross-sectional views showing the electrode fingers in Comparative Examples 1 and 2, respectively. As shown in FIG. 7A, in Comparative Example 1, the electrode finger 14 does not have the hem portion 15, and the width W2'is the width W2 + 2 × W3 of Example 1. As a result, the area of contact between the piezoelectric substrate 10 and the electrode finger 14 increases. However, since the thickness of the entire electrode finger 14 is large, the stress applied to the region 50 becomes large. Further, the width W2 of the electrode finger 14 affects the characteristics of the elastic wave resonator. Therefore, it may not be possible to obtain desired characteristics.

As shown in FIG. 7B, in Comparative Example 2, the metal film 12 forming the electrode finger 14 includes the metal films 12a and 12b. The metal film 12a forms the hem 15. The metal film 12b forms a portion of the electrode finger 14 on the hem 15. The materials of the metal film 12a and the metal film 12b are different. For example, the metal film 12a is an adhesive film. In Comparative Example 2, the metal films 12a and 12b may be peeled off at the interface between the metal films 12a and 12b. Further, if the metal film 12b is a metal having a low density and a low melting point, the effect of suppressing loss and / or suppressing migration is reduced.

According to the first embodiment, the electrode finger 14 is mainly composed of a metal having a melting point equal to or higher than the melting point of platinum. As a result, the speed of sound of surface acoustic waves becomes slower, and loss can be suppressed. In addition, migration is less likely to occur. However, the electrode finger 14 is easily peeled off from the piezoelectric substrate 10. Therefore, the electrode finger 14 is formed of one layer of the metal film 12 and has a hem portion 15 provided outside the side surface 30 in the X direction. As a result, the maximum stress applied to the piezoelectric substrate 10 and the electrode finger 14 can be reduced. Therefore, the peeling of the electrode finger 14 can be suppressed.

In a plan view, the entire periphery of the plurality of electrode fingers 14 may have a hem portion 15, or at least a part of the plurality of electrode fingers 14 may have a hem portion 15. It is preferable that the hem portions 15 are provided on both sides of the plurality of electrode fingers 14 in the X direction in the crossing region where the electrode fingers 14 of the pair of comb-shaped electrodes 18 intersect with each other.

The hem portion 15 is provided outside the position where the flat surface 32 in contact with the steepest portion of the side surface 30 of the plurality of electrode fingers 14 and the surface of the piezoelectric substrate 10 on the side of the plurality of electrode fingers 14 intersect. As a result, the maximum stress applied to the piezoelectric substrate 10 and the electrode finger 14 can be reduced.

In FIGS. 3A to 3D, the width W5 of the hem portion 15 in the X direction is 0.05 times or more the width W4 of the electrode finger 14 in the X direction. As a result, the maximum stress can be made smaller. The width W5 of the hem portion 15 is preferably 0.1 times or more, more preferably 0.2 times or more the width W4 of the electrode finger 14. The width W5 of the hem portion 15 is preferably 1 time or less, more preferably 0.5 times or less the width W4 of the electrode finger 14.

The maximum height H2 of the hem portion 15 is 0.5 times or less the height H1 of the plurality of electrode fingers 14. As a result, the maximum stress can be made smaller. The height H2 is preferably 0.2 times or less, more preferably 0.1 times or less the height H1. The height H2 is preferably 0.05 times or more, more preferably 0.1 times or more the height H1.

The plurality of electrode fingers 14 and the hem portion 15 are in contact with the piezoelectric substrate 10. This can further reduce loss and / or migration.

The plurality of electrode fingers 14 contain any one of molybdenum, iridium, platinum, rhenium, rhodium, ruthenium, tantalum and tungsten as a main component. This can reduce loss and / or migration.

The inclusion of a metal having a metal film 12 as a main component means that, for example, the atomic concentration of a certain metal in the metal film 12 is 50% or more, preferably 80% or more, and more preferably 90% or more. ..

[Modification 1 of Example 1]
FIG. 8A is a cross-sectional view of the electrode finger in the modified example 1 of the first embodiment. As shown in FIG. 8A, a metal film 17 is provided on the electrode finger 14. The metal film 17 is, for example, a chromium (Cr) film, a Ni (nickel) film, and a Ti (titanium) film, and contains a metal different from the main component of the electrode finger 14 as a main component. The metal film 17 functions as an etching stop layer in the manufacturing process and / or a layer that suppresses migration. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

As in the modified example 1 of the first embodiment, a metal film 17 provided on the electrode finger 14 and having a metal as a main component different from the main component of the electrode finger 14 may be provided. If the metal film 17 is thick, the function of the electrode finger 14 is impaired. Therefore, the metal film 17 is preferably thinner than the electrode finger 14, the film thickness of the metal film 17 is preferably 1/2 or less, and more preferably 1/5 or less of the film thickness of the electrode finger 14.

[Modification 2 of Example 1]
It is sectional drawing of the electrode finger in the modification 2 of Example 1. FIG. As shown in FIG. 8B, the metal film 12 has a first region 13a provided in contact with the piezoelectric substrate 10 and a second region 13b provided in contact with the first region 13a. The first region 13a includes the hem 15. The first region 13a has a uniform structure 54 without observing grain boundaries, and the first region 13a is in an amorphous state. In the second region 13b, the crystal grains 56 are columnar columns extending in the stacking direction, and the grain boundaries 52 are stretched in the stacking direction.

When a refractory metal having a melting point of Pt or higher is used as the electrode finger 14 on the piezoelectric substrate 10, columnar crystals are likely to be formed by either the vapor deposition method or the sputtering method. Grain boundaries are clear in columnar crystals. This is because the bonds between the grains are weak and / or there are gaps between the grains. Further, the crystal grains have the same size and are continuous in the stacking direction of the metal film 12. When a high-frequency signal of a large power is applied to the elastic wave resonator 24, the electrode finger 14 vibrates greatly due to the elastic surface wave, and stress is applied to the electrode finger 14. When the electrode finger 14 is a columnar crystal, it is considered that the electrode finger 14 is torn along the grain boundary. In order to improve the power resistance, it is conceivable that the entire metal film 12 has a structure that is not a columnar crystal. However, if the refractory metal is thickened to the extent that it functions as the electrode finger 14, the second region 13b of the columnar crystal is formed.

Therefore, according to the modified example 2 of the first embodiment, the first region 13a has an amorphous or a crystal grain smaller than the crystal grain of the second region 13b. As a result, the grain boundaries of the second region 13b are not continuous up to the first region 13a. Therefore, it is possible to prevent the electrode finger 14 from being damaged even when a high-frequency signal with high power is input. The crystal grains in the first region 13a and the second region 13b can be confirmed by observing using a TEM (Transmission Electron Microscope) method or an SEM (Scanning Electron Microscope) method.

When the metal film 12 having a function as an IDT 20 (about 0.1λ) is formed, the thickness of the second region 13b in the stacking direction becomes larger than the thickness of the first region 13a in the stacking direction. For example, the thickness of the second region 13b in the stacking direction is more than twice the thickness of the first region 13a in the stacking direction. In order to suppress the breakage of the electrode finger 14, the thickness of the first region 13a in the stacking direction is preferably 1/10 or more, more preferably 1/5 or more of the thickness of the second region 13b in the stacking direction.

In order to form the first region 13a, first, the upper surface of the piezoelectric substrate 10 is irradiated with Ar ions to make the upper surface uneven. After that, the metal film 12 is formed. As a result, the amorphous first region 13a and the columnar crystal second region 13b are formed.

Example 2 is an example of a filter and a duplexer using an elastic wave resonator of Example 1 and its modifications. FIG. 9A is a circuit diagram of the filter according to the second embodiment. As shown in FIG. 9A, one or a plurality of series resonators S1 to S4 are connected in series between the input terminal T1 and the output terminal T2. One or more parallel resonators P1 to P4 are connected in parallel between the input terminal T1 and the output terminal T2. The elastic wave resonators of Example 1 and its modifications 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 P4. A ladder type filter has been described as an example as a filter, but the filter may be a multiple mode type filter.

FIG. 9B is a circuit diagram of the duplexer according to the first modification of the second embodiment. As shown in FIG. 9B, a transmission filter 40 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 42 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 40 passes a signal in the transmission band among the high frequency signals input from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies. The reception filter 42 passes a signal in the reception band among the high frequency signals input from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. At least one of the transmission filter 40 and the reception filter 42 can be the filter of the second embodiment.

Although the duplexer has been described as an example as the multiplexer, a triplexer or a quadplexer may be used.

[Modification 2 of Example 2]
10 (a) and 10 (b) are cross-sectional views of the electrode fingers of the filter according to the second modification of the second embodiment. 10 (a) and 10 (b) show one elastic wave resonator R1 and another elastic wave resonator R1 among the series resonators S1 to S4 and the parallel resonators P1 to P4 in FIG. 9 (a). It is sectional drawing of the electrode finger in R2. As shown in FIGS. 10A and 10B, the elastic wave resonator R1 has a ratio of the width W5 of the hem 15 to the width W4 in which the electrode finger 14 is in contact with the piezoelectric substrate 10 as compared with the elastic wave resonator R2. big. Further, the elastic wave resonator R1 has a width W5 larger than that of the elastic wave resonator R2.

As in the second modification of the second embodiment, the W5 / W4 of at least one elastic wave resonator R1 among the plurality of elastic wave resonators included in the filter is made different from the W5 / W4 of the other elastic wave resonator R2. May be good. For example, the W5 of the elastic wave resonator R1 may be different from the W5 of the other elastic wave resonator R2. For example, at least one of the plurality of elastic wave resonators has W5 = 0 and does not have to have a hem 15. For example, a large amount of power is applied to the parallel resonator P1 and / or the series resonator S1 closest to the input terminal T1. Therefore, the W5 / W4 of the parallel resonator P1 and / or the series resonator S1 is made larger than the W5 / W4 of the other resonators. As a result, the power resistance of the filter can be improved, and deterioration of characteristics due to the provision of the hem portion 15 can be suppressed.

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Piezoelectric substrate 12, 17 Metal film 13a 1st region 13b 2nd region 14 Electrode finger 15 Hem 18 Comb electrode 20 IDT
22 Reflector 24 Elastic wave resonator 40 Transmit filter 42 Receive filter

Claims (11)

Piezoelectric substrate and
Each of the plurality of electrode fingers provided on the piezoelectric substrate and having a metal having a melting point equal to or higher than the melting point of platinum as a main component is provided. A pair of comb-shaped electrodes having a hem provided outside the side surface in the arrangement direction of the plurality of electrode fingers at least in part.
Equipped with
The hem portion is provided outside the first position where the plane in contact with the steepest portion of the side surface of the plurality of electrode fingers intersects with the surface of the piezoelectric substrate on the side of the plurality of electrode fingers.
The height of the piezoelectric substrate from the surface at the second position where a straight line passing through the first position and perpendicular to the surface of the piezoelectric substrate intersects the side surface of the electrode finger is the maximum height of the plurality of electrode fingers. An elastic wave device that is 0.2 times or less of . The elastic wave device according to claim 1 , wherein the surface of the plurality of electrode fingers opposite to the piezoelectric substrate includes a flat surface . The elastic wave device according to claim 1 or 2, wherein the width of the hem portion in the arrangement direction is 0.05 times or more the width of the plurality of electrode fingers in the arrangement direction. The elastic wave device according to any one of claims 1 to 3, wherein the height is 0.1 times or less the height of the plurality of electrode fingers. The elastic wave device according to any one of claims 1 to 4, wherein the plurality of electrode fingers are mainly composed of any one of molybdenum, iridium, platinum, rhenium, rhodium, ruthenium, tantalum and tungsten. The elastic wave device according to any one of claims 1 to 5, wherein the plurality of electrode fingers and the hem portion are in contact with the piezoelectric substrate. The elastic wave device according to any one of claims 1 to 6, further comprising a metal film provided on the plurality of electrode fingers and having a metal as a main component different from that of the main components of the plurality of electrode fingers. The plurality of electrode fingers have a first region provided on the piezoelectric substrate and including the hem portion, and a second region provided on the first region.
The elastic wave device according to any one of claims 1 to 7, wherein the first region is amorphous or has crystal grains smaller than the crystal grains of the second region. A filter comprising the elastic wave device according to any one of claims 1 to 8. Multiple series resonators connected between the input terminal and the output terminal,
A plurality of parallel resonators having one end connected to the path between the input terminal and the output terminal and the other end connected to the ground.
Equipped with
The plurality of series resonators and the plurality of parallel resonators are a plurality of elastic wave resonators each having the pair of comb-shaped electrodes .
The ratio of the width of the hem to the width of the plurality of electrode fingers in the array direction in the series resonator closest to the input terminal among the plurality of series resonators is the ratio of the width of the plurality of series resonators in the array direction. Of these, the ratio is larger than that of the series resonators other than the nearest series resonator.
And / or
The ratio of the parallel resonator closest to the input terminal among the plurality of parallel resonators is larger than the ratio of the parallel resonators other than the nearest parallel resonator among the plurality of parallel resonators according to claim 9. Described filter. A multiplexer including the filter according to claim 9 or 10.

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