JP2019029866A - Acoustic wave device - Google Patents

Abstract

To suppress temperature dependence of frequency in an acoustic wave device.SOLUTION: The acoustic wave device includes: a piezoelectric substrate 10; a pair of interdigital electrodes 18 provided on the piezoelectric substrate 10 and each having a plurality of electrode fingers 14 and a bus bar 16 to which the plurality of electrode fingers 14 are connected; and a pair of metal layers 26 at least partially embedded in the piezoelectric substrate 10 and provided so as to sandwich the pair of interdigital transducers 18 in a direction in which the plurality of electrode fingers 14 extends.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an acoustic wave device, for example, an acoustic wave device having a piezoelectric substrate.

  An elastic wave device using an elastic wave resonator is used in, for example, a filter and a multiplexer for mobile multi-communication. In the surface acoustic resonator, an IDT (Interdigital Transducer) that excites surface acoustic waves is formed on a piezoelectric substrate. (Patent Document 1).

JP 2007-184690 A

  A piezoelectric substrate has a large linear thermal expansion coefficient. For this reason, when the temperature changes, the frequency in the acoustic wave device changes.

  This invention is made | formed in view of the said subject, and it aims at suppressing the temperature dependence of the frequency in an elastic wave device.

  The present invention includes a piezoelectric substrate, a pair of comb electrodes provided on the piezoelectric substrate, each having a plurality of electrode fingers and a bus bar connected to the plurality of electrode fingers, and at least a part of the piezoelectric substrate. And a pair of metal layers provided so as to sandwich the pair of comb-shaped electrodes in a direction in which the plurality of electrode fingers extend.

  The said structure WHEREIN: A pair of said metal layer can be set as the structure which has a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the sequence direction of the said several electrode finger of the said piezoelectric substrate.

  The above-described configuration may include a pair of reflectors provided so as to sandwich the pair of comb-shaped electrodes in a direction in which the plurality of electrode fingers are arranged.

  In the above configuration, the pair of metal layers may be provided so as to sandwich the pair of reflectors.

  The said structure WHEREIN: The length of the said metal layer can be set as the structure larger than the length of the said bus bar in the direction where these electrode fingers are arranged.

  In the above-described configuration, the piezoelectric substrate includes a support substrate that is bonded to a surface opposite to the surface on which the pair of comb-shaped electrodes are provided and has a linear thermal expansion coefficient smaller than that of the piezoelectric substrate. can do.

  In the above configuration, the linear thermal expansion coefficient of the pair of metal layers may be smaller than the linear thermal expansion coefficient of the support substrate.

  In the above structure, no other metal layer may be provided between the pair of comb electrodes and the pair of metal layers.

  In the above configuration, one or more series resonators provided on the piezoelectric substrate and connected in series between an input terminal and an output terminal, and provided on the piezoelectric substrate, the input terminal and the output terminal 1 or a plurality of parallel resonators connected in parallel with each other, and a series type resonator having the highest antiresonance frequency among the one or more series resonators, Alternatively, at least one of the parallel resonators having the lowest resonance frequency among the plurality of parallel resonators includes the pair of comb electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend. It can be configured.

  In the above-described configuration, at least one of the resonators other than the series resonator having the highest antiresonance frequency among the one or more series resonators and the parallel resonator having the lowest resonance frequency among the one or more parallel resonators. One resonator may be configured not to include the pair of comb-shaped electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend.

  The said structure WHEREIN: It can be set as the structure which comprises the filter containing a pair of said comb-shaped electrode in the direction where these electrode fingers extend | stretch.

  In the above configuration, a multiplexer including the filter can be provided.

  In the above configuration, the one or more first series resonators and one or more first parallel resonators are connected between the common terminal and the first terminal, and the one or more first series resonances are provided. At least one of the vessels includes a first ladder filter including the pair of comb-shaped electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend, and a higher passband than the first ladder filter Connected between the common terminal and the second terminal, and having one or more second series resonators and one or more second parallel resonators, the one or more second parallel resonators At least one of the resonators includes a multiplexer including a second ladder filter including the pair of comb-shaped electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend. Can do.

  ADVANTAGE OF THE INVENTION According to this invention, the temperature dependence of the frequency in an elastic wave device can be suppressed.

FIG. 1A is a plan view of the acoustic wave device according to the first embodiment, and FIGS. 1B and 1C are an AA cross section and a BB cross section of FIG. 2A and 2B are cross-sectional views of the acoustic wave device according to the first modification of the first embodiment. FIG. 3A is a diagram showing the thicknesses T10, T11 and T26 and the material of the metal layer in each sample, and FIG. 3B is the Young's modulus, Poisson's ratio and linear thermal expansion coefficient of each material used in the simulation. FIG. FIG. 4 is a diagram showing a thermal expansion coefficient with respect to the thickness T26 of the metal layer showing the simulation result. FIG. 5 is a plan view of the acoustic wave device according to the second embodiment. FIG. 6 is a diagram illustrating the attenuation characteristics of the resonators according to the second embodiment. FIGS. 7A to 7C are cross-sectional views of the acoustic wave device according to the third embodiment and the first and second modifications thereof. FIG. 8A is a cross-sectional view of the acoustic wave element 52 in the third embodiment and its modification, and FIG. 8B is a circuit diagram of a duplexer according to the third modification of the third embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

  The temperature coefficient of frequency (TCF) is determined by the sum of the coefficient of linear thermal expansion (TEC) and the temperature coefficient of phase velocity (TCV: Temperature Coefficient of Velocity). Therefore, in Example 1, attention was paid to the linear thermal expansion coefficient. By embedding a metal layer in the piezoelectric substrate, it was examined that the temperature coefficient of frequency approaches 0 (that is, the absolute value is reduced).

  FIG. 1A is a plan view of the acoustic wave device according to the first embodiment, and FIGS. 1B and 1C are an AA cross section and a BB cross section of FIG. As shown in FIGS. 1A to 1C, in the 1-port resonator, an IDT 20 and a reflector 22 are provided on the piezoelectric substrate 10. The piezoelectric substrate 10 is, for example, a lithium niobate substrate or a lithium tantalate substrate. The IDT 20 and the reflector 22 are formed by the metal film 12 formed on the piezoelectric substrate 10. The metal film 12 is, for example, a Cu (copper) film or an Al (aluminum) film. The IDT 20 includes a pair of opposing comb electrodes 18.

  The comb-shaped electrode 18 includes a plurality of electrode fingers 14 and a bus bar 16 to which the plurality of electrode fingers 14 are connected. The pair of comb-shaped electrodes 18 are provided to face each other so that the electrode fingers 14 are staggered at least in part. The IDT 20 mainly excites an elastic wave propagating in the arrangement direction of the electrode fingers 14. The elastic wave is reflected by the reflector 22. The pitch of the electrode fingers 14 in the same comb electrode 18 substantially corresponds to the wavelength λ of the elastic wave. The arrangement direction of the electrode fingers 14 (that is, the propagation direction of the elastic wave) is the X direction, the extending direction of the electrode fingers 14 is the Y direction, and the normal direction of the piezoelectric substrate 10 is the Z direction.

  A wiring 24 is provided on the piezoelectric substrate 10. The pair of wirings 24 are connected to the bus bars 16 of the pair of comb electrodes 18 respectively. The wiring 24 is formed of, for example, the metal film 12. The wiring 24 may be a metal film made of a material different from that of the metal film 12. A metal layer 26 is provided so as to sandwich the pair of comb-shaped electrodes 18 in the Y direction. The metal layer 26 is embedded in the piezoelectric substrate 10. The metal layer 26 has a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the X direction of the piezoelectric substrate 10. The metal layer 26 is, for example, a Cu layer or a W (tungsten) layer.

  The lengths of the piezoelectric substrate 10 in the X direction and the Y direction are Lx and Ly. The length in the X direction and the width in the Y direction of the metal layer 26 are L26 and W26, respectively. The interval between the metal layers 26 is W20. The thicknesses of the piezoelectric substrate 10 and the metal layer 26 are T10 and T26, respectively.

[Modification 1 of Example 1]
2A and 2B are cross-sectional views of the acoustic wave device according to the first modification of the first embodiment, and correspond to the AA cross section and the BB cross section of FIG. As shown in FIGS. 2A and 2B, the support substrate 11 is bonded to the surface of the piezoelectric substrate 10 opposite to the surface on which the IDT 20 is provided. The support substrate 11 has a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the X direction of the piezoelectric substrate 10 and is, for example, a sapphire substrate, a spinel substrate, a silicon substrate, or a quartz substrate. The piezoelectric substrate 10 may be directly bonded to the support substrate 11 or may be bonded via an adhesive or the like. The thickness of the support substrate 11 is T11. The thickness T26 of the metal layer 26 and the thickness T10 of the piezoelectric substrate 10 are substantially the same. The thicknesses T26 and T10 may be different.

[simulation]
The thermal expansion coefficient in Example 1 and its modification example 1 was simulated. In the simulation, the temperature was changed, and the expansion of the distance between the locations 28 located at the ends of the metal layer 26 in the X direction and the center in the Y direction between the metal layers 26 in FIG. The rate of change of the distance between the locations 28 per 1 ° C. was defined as the thermal expansion coefficient (unit: / ° C.). In addition, in order to distinguish with the linear thermal expansion coefficient of material, it is called a thermal expansion coefficient below.

The simulation conditions are shown below.
Piezoelectric substrate 10: 42 ° rotation Y-cut X-propagation lithium tantalate substrate Support substrate 11: Sapphire substrate Metal layer 26: Cu or W
Chip size: Lx = 0.71 mm, Ly = 0.84 mm
Size of metal layer 26: L26 = 0.7 mm, W26 = 0.05 mm, W20 = 0.1 mm
Since the metal film 12 and the wiring 24 are sufficiently thinner than the metal layer 26, the metal film 12 and the wiring 24 are not considered.

  Fig.3 (a) is a figure which shows the thickness T10, T11, and T26 and the material of a metal layer in each sample. As shown in FIG. 3A, samples A1 to A3 correspond to Example 1. The thickness T10 of the piezoelectric substrate 10 is 150 μm, and the metal layer 26 is W. Samples B1 to B3 and C1 to C3 correspond to the first modification of the first embodiment. The metal layer 26 of samples B1 to B3 is W, and the metal layer 26 of samples C1 to C3 is Cu. The thickness T26 of the metal layer 26 and the thickness T10 of the piezoelectric substrate 10 are the same. The total of the thickness T10 of the piezoelectric substrate 10 and the thickness T11 of the support substrate 11 is 150 μm. The piezoelectric substrate 10 and the support substrate 11 are directly bonded. Sample D0 corresponds to Comparative Example 1 and is the same as Samples A1 to A3 except that the metal layer 26 is not provided. Samples D1 to D3 correspond to Comparative Example 2. Samples D1 to D3 are the same as Samples B1 and C1, Samples B2 and C2, and Samples B3 and C3, respectively, except that the metal layer 26 is not provided.

  FIG. 3B is a diagram showing Young's modulus, Poisson's ratio, and linear thermal expansion coefficient of each material used in the simulation. As shown in FIG. 3B, the linear thermal expansion coefficient of the lithium tantalate substrate (LT) varies depending on the crystal orientation. X, Y, and Z are linear thermal expansion coefficients of which the crystal orientation is X-axis orientation, Y-axis orientation, and Z-axis orientation, respectively. The linear thermal expansion coefficient in the X-axis direction is the largest, and the linear thermal expansion coefficient in the Y-axis direction is the smallest. The linear thermal expansion coefficient of W and sapphire is smaller than the linear thermal expansion coefficient of the X axis of the lithium tantalate substrate. The linear thermal expansion coefficient of Cu is larger than the linear thermal expansion coefficient of the X axis of the lithium tantalate substrate. The linear thermal expansion coefficient of W is smaller than that of sapphire. The Young's modulus of W and sapphire is greater than the Young's modulus of the lithium tantalate substrate. The Young's modulus of Cu is smaller than that of the lithium tantalate substrate.

  FIG. 4 is a diagram showing the thermal expansion coefficient with respect to the thickness T26 of the metal layer 26 showing the simulation result. As shown in FIG. 4, in the sample D0 of Comparative Example 1, the thermal expansion coefficient is 16.1 ppm / ° C., which is the same as the linear thermal expansion coefficient of the X axis of the lithium tantalate substrate. In samples A1 to A3 of Example 1, the thermal expansion coefficients are 13.9 ppm / ° C., 14.5 ppm / ° C., and 15.2 ppm / ° C., respectively. Samples A1 to A3 have a smaller coefficient of thermal expansion than sample D0. As the thickness T26 of the metal layer 26 increases, the thermal expansion coefficient decreases.

  In samples D1 to D3 of Comparative Example 2, the coefficient of thermal expansion decreases as the thickness T26 of the metal layer 26 and the thickness T10 of the piezoelectric substrate 10 decrease. In samples B1 to B3 of Modification 1 of Example 1, the thermal expansion coefficients are smaller than those of samples D1 to D3. In samples C1 to C3, the thermal expansion coefficient is slightly smaller than samples D1 to D3.

  According to Example 1 and Modification 1 thereof, as shown in FIGS. 1A to 2B, the pair of metal layers 26 are embedded in the piezoelectric substrate 10, and the pair of comb electrodes 18 in the Y direction. It is provided so that it may be inserted. Thereby, the thermal expansion coefficient of the location 28 of Fig.1 (a) can be suppressed. Therefore, the temperature change of the frequency of the elastic wave device can be suppressed.

  The metal layer 26 only needs to be at least partially embedded in the piezoelectric substrate 10. Thereby, the metal layer 26 can support the stress caused by the expansion or contraction of the piezoelectric substrate 10 in the X direction. All or part of the side surfaces of the metal layer 26 are preferably in contact with the piezoelectric substrate 10. Like the samples A1 to A3 and B1 to B3, the linear thermal expansion coefficient of the metal layer 26 is smaller than the linear thermal expansion coefficient in the X direction of the piezoelectric substrate 10. Thereby, the thermal expansion coefficient of the location 28 of Fig.1 (a) can be suppressed more. Therefore, the temperature change of the frequency of an elastic wave device can be suppressed more. The linear thermal expansion coefficient of the metal layer 26 is preferably 2/3 or less of the linear thermal expansion coefficient of the piezoelectric substrate 10 and more preferably 1/2 or less. The metal layer 26 may be a metal layer other than the Cu layer or the W layer.

  The pair of metal layers 26 may overlap with a part of the pair of comb-shaped electrodes 18 when viewed from the Y direction. When the pair of reflectors 22 are provided so as to sandwich the pair of comb-shaped electrodes 18 in the X direction, the pair of metal layers 26 are preferably provided so as to sandwich the pair of reflectors 22. Thereby, the temperature change of the frequency of an elastic wave device can be suppressed more.

  In the X direction, the length of the pair of metal layers 26 is larger than the length of the bus bar 16. Thereby, the temperature change of the frequency of an elastic wave device can be suppressed more.

  In order to reduce the thermal expansion coefficient, the width of the metal layer 26 in the Y direction is preferably 0.1 times or more, more preferably 0.2 times or more, the width of the pair of comb electrodes 18 in the Y direction. In order to reduce the chip area, the width of the metal layer 26 in the Y direction is preferably not more than 1 time and more preferably not more than 0.7 times the width of the pair of comb electrodes 18 in the Y direction. In order to reduce the thermal expansion coefficient, the gap width between the metal layer 26 and the pair of comb electrodes 18 is preferably 0.5 times or less, and 0.2 times the width of the pair of comb electrodes 18 in the Y direction. The following is more preferable.

  In order to reduce the thermal expansion coefficient, it is preferable that no other metal layer is provided between the pair of comb-shaped electrodes 18 and the pair of metal layers 26. In order to reduce the chip area, the pair of metal layers 26 are preferably not provided in the X direction of the pair of comb electrodes 18.

  The thickness of the metal film 12 and the wiring 24 is 1 μm or less. In order to reduce the thermal expansion coefficient, the thickness T26 of the metal layer 26 is preferably thicker than the metal film 12 and the wiring 24. The thickness T26 of the metal layer 26 is preferably at least twice the thickness of the metal film 12 and the wiring 24, more preferably at least 5 times, and even more preferably at least 10 times. From the viewpoint of simplifying the manufacturing process, the thickness of the metal layer 26 is preferably 1/3 or less of the total thickness of the piezoelectric substrate 10 and the support substrate 11, and more preferably 1/5 or less. The depth at which the metal layer 26 is embedded in the piezoelectric substrate 10 is preferably 1 or more times the thickness of the metal film 12 and the wiring 24, more preferably 5 times or more, and even more preferably 10 times or more. From the viewpoint of simplifying the manufacturing process, the depth at which the metal layer 26 is embedded in the piezoelectric substrate 10 is preferably 1/3 or less of the total thickness of the piezoelectric substrate 10 and the support substrate 11, and more preferably 1/5 or less. .

  The pair of metal layers 26 may be electrically connected to the pair of wirings 24, respectively. The pair of metal layers 26 may be electrically separated from the pair of wirings 24. An insulating film may be provided between the pair of metal layers 26 and the pair of wirings 24.

  When the piezoelectric substrate 10 is a rotating Y-cut X-propagating lithium tantalate substrate or a rotating Y-cut X-propagating lithium niobate substrate, the linear thermal expansion coefficient in the X direction of the piezoelectric substrate 10 increases. Therefore, it is preferable to provide the metal layer 26.

  As in the first modification of the first embodiment, the support substrate 11 is bonded to the lower surface of the piezoelectric substrate 10. The linear thermal expansion coefficient of the support substrate 11 is smaller than the linear thermal expansion coefficient of the piezoelectric substrate 10. Thereby, the temperature change of the frequency of an elastic wave device can be suppressed more.

  Like samples B1 to B3, the linear thermal expansion coefficient of the pair of metal layers 26 is preferably smaller than the linear thermal expansion coefficient of the support substrate 11. Thereby, a thermal expansion coefficient can be made smaller.

  When the support substrate 11 is provided, the metal layer 26 preferably penetrates the piezoelectric substrate 10 in the Z direction. Thereby, a thermal expansion coefficient can be made small. The metal layer 26 may not penetrate the piezoelectric substrate 10 in the Z direction.

  FIG. 5 is a plan view of the acoustic wave device according to the second embodiment. As shown in FIG. 5, one or more series resonators S <b> 1 to S <b> 4, one or more parallel resonators P <b> 1 to P <b> 3, wirings 24, and bumps 25 are provided on the piezoelectric substrate 10. Each resonator includes a reflector 22 provided on both sides of the IDT 20 and the IDT 20 in the X direction. The bump 25 includes an input bump T1, an output bump T2, and a ground bump Tg. The wiring 24 electrically connects each resonator and between each resonator and the bump 25. The bumps 25 are, for example, stud Au bumps, Cu pillars formed by plating, or solder balls such as AuSn, SnAgCu, or SnAg.

  The series resonators S1 to S4 are connected in series via the wiring 24 between the input bump T1 (ie, input terminal) and the output bump T2 (ie, output terminal). The parallel resonators P1 to P3 are connected in parallel via the wiring 24 between the input bump T1 and the output bump T2. Thus, the series resonators S1 to S4 and the parallel resonators P1 to P3 function as a ladder type filter. Metal layers 26 are provided on both sides of the series resonator S3 and the parallel resonator P2 in the Y direction.

  FIG. 6 is a diagram illustrating the attenuation characteristics of the resonators according to the second embodiment. As shown in FIG. 6, the attenuation pole on the high frequency side of the passband of the ladder filter is formed by the antiresonance points of the series resonators S1 to S4. The attenuation pole on the low frequency side of the pass band is formed by the resonance points of the parallel resonators P1 to P3. The series resonator S3 having the highest antiresonance frequency among the series resonators (the antiresonance frequency is fsa3) has the greatest influence on the skirt characteristics on the high frequency side of the pass band. The parallel resonator P2 (resonance frequency is fpr2) having the lowest resonance frequency among the parallel resonators has the most influence on the skirt characteristic on the low frequency side of the pass band. In order to suppress the temperature dependence of the passband, it is effective to reduce the temperature dependence of the series resonator S3 and the parallel resonator P2.

  Therefore, as shown in FIG. 5, the metal layers 26 are provided on both sides in the Y direction of the series resonator S3 and the parallel resonator P2. Thereby, the linear thermal expansion coefficient in series resonator S3 and parallel resonator P2 becomes small. The frequency temperature coefficient of the series resonator S3 and the parallel resonator P2 is suppressed. Therefore, the temperature dependence of the skirt characteristic of the passage characteristic is reduced, and the temperature dependence of the passage area is reduced.

  The interval between the antiresonance frequency and the resonance frequency does not change depending on the resonator. Therefore, the series resonator S3 can be said to be the series resonator having the highest resonance frequency among the series resonators S1 to S4. The parallel resonator P2 can be said to be the parallel resonator having the lowest antiresonance frequency among the parallel resonators P1 to P3.

  According to the second embodiment, the series resonator S3 having the highest anti-resonance frequency among the one or more series resonators S1 to S4 and the parallel resonance having the lowest resonance frequency among the one or more parallel resonators P1 to P3. Metal layers 26 are provided on both sides in the Y direction of the container P2. Thereby, the temperature characteristic of a pass band can be suppressed. The metal layer 26 may be provided on at least one of the series resonator S3 and the parallel resonator P2.

  The antiresonance frequencies of the series resonators S1 to S4 may all be the same. In this case, the metal layer 26 may be provided in at least one Y direction of the series resonators S1 to S4. Further, the resonance frequencies of the parallel resonators P1 to P3 may all be the same. In this case, the metal layer 26 may be provided in at least one Y direction of the parallel resonators P1 to P3.

  At least one of the series resonators S1 to S4 may have a different antiresonance frequency from the other series resonators. In this case, the metal layer 26 may be provided in the Y direction of the series resonator S3 having the highest antiresonance frequency. At least one of the parallel resonators P1 to P3 may have a resonance frequency different from that of the other parallel resonators. In this case, the metal layer 26 may be provided in the Y direction of the parallel resonator P2 having the lowest resonance frequency.

  Of the series resonators S1 to S4 and the parallel resonators P1 to P3, at least one resonator other than the series resonator S3 and the parallel resonator P2 may not be provided with the metal layer 26 in the Y direction. That is, the metal layer 26 may not be provided in the Y direction of some of the series resonators S1, S2, or S4 among the series resonators S1 to S4. The metal layer 26 may not be provided in the Y direction of some of the parallel resonators P1 and P2 among the parallel resonators P1 to P3. As a result, the number of metal layers 26 can be reduced. Therefore, the chip area can be reduced.

  The metal layer 26 is preferably closer to the series resonator S3 than the series resonators S2 and S4 adjacent in the Y direction of the series resonator S3. The metal layer 26 is preferably closer to the parallel resonator P2 than the parallel resonators P1 and P3 adjacent to the parallel resonator P2 in the Y direction. Thereby, the frequency temperature characteristics of the series resonator S3 and the parallel resonator P2 can be further suppressed.

  FIG. 7A is a cross-sectional view of the acoustic wave device according to the third embodiment. As shown in FIG. 7A, the acoustic wave element 21 and the wiring 24 are provided on the upper surface of the piezoelectric substrate 10. The wiring 24 is electrically connected to the acoustic wave element 21. Terminals 40 are provided on the lower surface of the piezoelectric substrate 10. The terminal 40 is a foot pad for connecting the acoustic wave element 21 to the outside via the wiring 24. A via wiring 42 penetrating the piezoelectric substrate 10 is provided. The via wiring 42 electrically connects the wiring 24 and the terminal 40. The wiring 24, the via wiring 42, and the terminal 40 are metal layers such as a copper layer, an aluminum layer, or a gold layer, for example. A metal layer 26 and an annular metal layer 44 are embedded on the upper surface of the piezoelectric substrate 10. The annular metal layer 44 is provided on the outer edge of the piezoelectric substrate 10 so as to surround the acoustic wave element 21. The annular metal layer 44 is a copper layer or a tungsten layer.

  The acoustic wave element 52 and the wiring 54 are provided on the lower surface of the substrate 50. The substrate 50 is, for example, a silicon substrate, a sapphire substrate, a spinel substrate, or an alumina substrate. The wiring 54 is a metal layer such as a copper layer, an aluminum layer, or a gold layer. The substrate 50 is flip-chip mounted (face-down mounted) on the piezoelectric substrate 10 via the bumps 25. The bump 25 joins the wirings 24 and 54 together.

  A sealing portion 58 is provided on the piezoelectric substrate 10 so as to surround the substrate 50. The sealing part 58 is a resin layer such as an epoxy resin. The acoustic wave elements 21 and 52 are opposed to each other with the gap 56 interposed therebetween. The bump 25 is surrounded by the gap 56.

[Modification 1 of Example 3]
FIG. 7B is a cross-sectional view of the acoustic wave device according to the first modification of the third embodiment. As shown in FIG. 7B, the piezoelectric substrate 10 is bonded to the upper surface of the support substrate 11. Other configurations are the same as those of the third embodiment, and the description thereof is omitted.

[Modification 2 of Example 3]
FIG. 7C is a cross-sectional view of the acoustic wave device according to the second modification of the third embodiment. As shown in FIG. 7C, a lid 55 is provided on the upper surface of the sealing portion 58 and the substrate 50. A sealing portion 58 may be provided between the upper surface of the substrate 50 and the lid 55. A protective film 57 is provided so as to cover the lid 55 and the sealing portion 58. The sealing portion 58 is a metal layer such as SnAg solder. The lid 55 is a metal plate such as a Kovar plate or an insulator plate. The protective film 57 is a metal film such as a nickel film or an insulator film. Other configurations are the same as those of the first modification of the third embodiment, and a description thereof will be omitted.

  The elastic wave element 21 in the third embodiment and its modification is the surface acoustic wave resonator shown in FIGS. 1 (a) to 2 (b). FIG. 8A is a cross-sectional view of the acoustic wave device 52 according to the third embodiment and its modification. As shown in FIG. 8A, the acoustic wave element 52 is a piezoelectric thin film resonator. A piezoelectric film 66 is provided on the substrate 50. A lower electrode 64 and an upper electrode 68 are provided so as to sandwich the piezoelectric film 66. A gap 65 is formed between the lower electrode 64 and the substrate 50. The lower electrode 64 and the upper electrode 68 excite elastic waves in the thickness longitudinal vibration mode in the piezoelectric film 66. The lower electrode 64 and the upper electrode 68 are metal films such as a ruthenium film, for example. The piezoelectric film 66 is an aluminum nitride film, for example.

  Although the example in which the acoustic wave element 52 is provided on the lower surface of the substrate 50 has been described, the acoustic wave element 52 may not be provided on the lower surface of the substrate 50. For example, active elements such as amplifiers and / or switches may be provided on the lower surface of the substrate 50. Further, passive elements such as inductors and / or capacitors may be provided on the lower surface of the substrate 50. A MEMS (Micro Electro Mechanical Systems) element may be provided on the lower surface of the substrate 50.

  The piezoelectric substrate 10 may be mounted on an insulating substrate such as a resin substrate or a ceramic substrate.

[Modification 3 of Example 3]
FIG. 8B is a circuit diagram of a duplexer according to the third modification of the third embodiment. As shown in FIG. 8B, a transmission filter 60 (first ladder filter) is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 62 (second ladder filter) is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 60 passes a signal in the transmission band among 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 to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. At least one of the transmission filter 60 and the reception filter 62 may be the filter of the second embodiment.

  For example, the pass band of the reception filter 62 (second ladder type filter) has a higher frequency than the pass band of the transmission filter 60 (first ladder type filter). A band between the pass band of the reception filter 62 and the pass band of the transmission filter 60 is a guard band. It is preferable that the temperature change of the skirt characteristic on the guard band side in the pass band is small. Therefore, when the transmission filter 60 includes one or more series resonators (first series resonators) and one or more parallel resonators (first parallel resonators), at least one resonator of the series resonators. A metal layer 26 is provided in the Y direction. Thereby, the temperature change of the skirt characteristic by the side of the guard band of the transmission filter 60 can be made small.

  Further, when the reception filter 62 includes one or more series resonators (second series resonators) and one or more parallel resonators (second parallel resonators), at least one resonator of the parallel resonators A metal layer 26 is provided in the Y direction. Thereby, the temperature change of the skirt characteristic on the guard band side of the reception filter 62 can be reduced.

  Furthermore, in the transmission filter 60, it is preferable to provide the metal layer 26 in the Y direction of the series resonator having the highest antiresonance frequency. In the reception filter 62, it is preferable to provide the metal layer 26 in the Y direction of the parallel resonator having the lowest resonance frequency. Thereby, the temperature change of the skirt characteristic by the side of a guard band can be made smaller.

  The transmission filter 60 and the reception filter 62 have been described as examples. However, both of the two filters in FIG. 8B may be transmission filters, or both may be reception filters. Although the duplexer has been described as an example of the multiplexer, a triplexer or a quadplexer may be used.

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

DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate 11 Support substrate 12 Metal film 14 Electrode finger 16 Bus bar 18 Comb electrode 20 IDT
22 Reflector 24 Wiring 26 Metal layer 60 Transmission filter 62 Reception filter

Claims (13)

A piezoelectric substrate;
A pair of comb-shaped electrodes provided on the piezoelectric substrate, each having a plurality of electrode fingers and a bus bar connected to the plurality of electrode fingers;
A pair of metal layers embedded in at least a part of the piezoelectric substrate and sandwiching the pair of comb electrodes in a direction in which the plurality of electrode fingers extend;
An elastic wave device comprising:   2. The acoustic wave device according to claim 1, wherein the pair of metal layers has a linear thermal expansion coefficient smaller than a linear thermal expansion coefficient in a direction in which the plurality of electrode fingers of the piezoelectric substrate are arranged.   3. The acoustic wave device according to claim 1, further comprising a pair of reflectors provided so as to sandwich the pair of comb-shaped electrodes in a direction in which the plurality of electrode fingers are arranged.   The acoustic wave device according to claim 3, wherein the pair of metal layers are provided so as to sandwich the pair of reflectors.   The elastic wave device according to any one of claims 1 to 4, wherein a length of the metal layer is larger than a length of the bus bar in a direction in which the plurality of electrode fingers are arranged.   6. The support substrate according to claim 1, further comprising a support substrate that is bonded to a surface opposite to the surface on which the pair of comb-shaped electrodes of the piezoelectric substrate is provided and has a linear thermal expansion coefficient smaller than that of the piezoelectric substrate. The elastic wave device according to any one of claims.   The acoustic wave device according to claim 6, wherein a linear thermal expansion coefficient of the pair of metal layers is smaller than a linear thermal expansion coefficient of the support substrate.   The elastic wave device according to claim 1, wherein no other metal layer is provided between the pair of comb-shaped electrodes and the pair of metal layers. One or more series resonators provided on the piezoelectric substrate and connected in series between an input terminal and an output terminal;
One or more parallel resonators provided on the piezoelectric substrate and connected in parallel between the input terminal and the output terminal;
Comprising a ladder type filter comprising:
At least one of the series resonator having the highest anti-resonance frequency among the one or more series resonators and the parallel resonator having the lowest resonance frequency among the one or more parallel resonators is the plurality of electrodes. The acoustic wave device according to any one of claims 1 to 8, comprising the pair of comb electrodes provided with the pair of metal layers in a direction in which a finger extends.   At least one resonator of a resonator other than the series resonator having the highest anti-resonance frequency among the one or more series resonators and the parallel resonator having the lowest resonance frequency among the one or more parallel resonators is The acoustic wave device according to claim 9, wherein the acoustic wave device does not include the pair of comb-shaped electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend.   The acoustic wave device according to any one of claims 1 to 10, further comprising a filter including the pair of comb-shaped electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend.   The acoustic wave device according to claim 11, further comprising a multiplexer including the filter. Connected between the common terminal and the first terminal, and having one or more first series resonators and one or more first parallel resonators, at least one of the one or more first series resonators One is a first ladder type filter including the pair of comb-shaped electrodes provided with the pair of metal layers in a direction in which the plurality of electrode fingers extend.
It has a higher passband than the first ladder filter, and is connected between the common terminal and the second terminal, and has one or more second series resonators and one or more second parallel resonators. And at least one of the one or more second parallel resonators includes the second ladder filter including the pair of comb electrodes provided with the pair of metal layers in a direction in which the electrode fingers extend;
The acoustic wave device according to any one of claims 1 to 10, further comprising a multiplexer including:

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