JP2019201345A - Acoustic wave resonator, filter and multiplexer - Google Patents

Abstract

To improve frequency temperature characteristics and suppress a loss.SOLUTION: An acoustic wave resonator is provided that comprises: a support substrate; a piezoelectric substrate provided in the support substrate, and having a phase velocity smaller than a phase velocity of the support substrate; a temperature compensation film provided between the support substrate and the piezoelectric substrate, and having a phase velocity smaller than a phase velocity of the support substrate and a phase velocity temperature coefficient of the opposite sign to a sign of a phase velocity temperature coefficient of the piezoelectric substrate; and a pair of comb-like electrodes provided in the piezoelectric substrate, each having a plurality of electrode fingers, wherein an average pitch of the electrode fingers of one of the comb-like electrodes is one half or more of a total thickness of the temperature compensation film and the piezoelectric substrate.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an acoustic wave resonator, a filter, and a multiplexer, for example, an acoustic wave resonator, a filter, and a multiplexer that have a pair of comb-shaped electrodes.

  A surface acoustic wave resonator is known as an acoustic wave resonator used in communication devices such as smartphones. It is known to attach a piezoelectric substrate forming a surface acoustic wave resonator to a support substrate. It is known that the thickness of the piezoelectric substrate is made equal to or less than the wavelength of the surface acoustic wave (for example, Patent Document 1).

JP 2017-034363 A

  By bonding the piezoelectric substrate to the support substrate, the frequency temperature coefficient (TCF) of the acoustic wave resonator can be reduced. By setting the thickness of the piezoelectric substrate to be equal to or less than the wavelength of the surface acoustic wave, spurious and loss can be suppressed. However, suppression of the temperature temperature coefficient (TCF) and loss is not sufficient.

  The present invention has been made in view of the above problems, and has an object to improve frequency temperature characteristics and suppress loss.

  The present invention is provided between a support substrate, a piezoelectric substrate provided on the support substrate and having a phase velocity smaller than a phase velocity of the support substrate, and between the support substrate and the piezoelectric substrate. A temperature compensation film having a phase velocity smaller than the phase velocity and a temperature coefficient of a phase velocity having a sign opposite to the sign of the temperature coefficient of the phase velocity of the piezoelectric substrate; and a plurality of electrodes each provided on the piezoelectric substrate. An acoustic wave resonator comprising a pair of comb-shaped electrodes, each having a finger and an average pitch of electrode fingers of one of the comb-shaped electrodes being ½ or more of a total thickness of the temperature compensation film and the piezoelectric substrate is there.

  In the above configuration, the average pitch may be larger than the thickness of the piezoelectric substrate.

  In the above configuration, the linear thermal expansion coefficient of the support substrate in the arrangement direction of the plurality of electrode fingers may be smaller than the linear thermal expansion coefficient of the piezoelectric substrate in the arrangement direction.

  In the above configuration, the thickness of the piezoelectric substrate and the thickness of the temperature compensation film may be substantially equal.

  In the above configuration, the piezoelectric substrate is a lithium tantalate substrate or a lithium niobate substrate, and the support substrate is a sapphire substrate, a spinel substrate, a silicon substrate, a quartz substrate, a quartz substrate, or an alumina substrate, and a single crystal substrate Alternatively, it may be a polycrystalline substrate, and the temperature compensation film may be a silicon oxide film.

  In the above configuration, the pair of comb electrodes may be configured to excite surface acoustic waves.

  The said structure WHEREIN: The average pitch of the electrode finger of said one comb-shaped electrode can be set as the structure which is 1 / 1.5 or more of the total thickness of the said temperature compensation film and the said piezoelectric substrate.

  The present invention is a filter including the elastic wave resonator.

  The present invention is a multiplexer including the filter.

  According to the present invention, frequency temperature characteristics can be improved and loss can be suppressed.

1 is a perspective view of an acoustic wave resonator according to a first embodiment. FIG. 2A is a plan view of the acoustic wave resonator according to the first embodiment, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. FIG. 3 is a cross-sectional view of the acoustic wave resonator according to the first embodiment. 4A and 4B are cross-sectional views of the acoustic wave resonator in simulations A and B. FIG. FIGS. 5A and 5B are diagrams showing the total displacement distribution with respect to the position Z in the simulations A and B. FIG. FIG. 6A to FIG. 6C are cross-sectional views illustrating bulk waves. FIG. 7 is a diagram illustrating the admittance with respect to the frequency of the acoustic wave resonator according to the first embodiment. FIG. 8A to FIG. 8E are cross-sectional views (part 1) illustrating the method for manufacturing the acoustic wave resonator according to the first embodiment. FIG. 9A to FIG. 9D are cross-sectional views (part 2) illustrating the method for manufacturing the acoustic wave resonator according to the first embodiment. FIG. 10A and FIG. 10B are cross-sectional views (part 3) illustrating the method for manufacturing the acoustic wave resonator according to the first embodiment. FIG. 11A and FIG. 11B are circuit diagrams of a filter according to the second embodiment and the first modification thereof, and FIG. 11C is a circuit diagram of a duplexer according to the second modification of the second embodiment. .

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of an elastic wave resonator according to the first embodiment, FIG. 2A is a plan view of the elastic wave resonator according to the first embodiment, and FIG. 2B is A in FIG. It is -A sectional drawing. The arrangement direction of the electrode fingers is the X direction, the extending direction of the electrode fingers is the Y direction, and the stacking direction of the support substrate and the piezoelectric substrate is the Z direction. The X direction, the Y direction, and the Z direction do not necessarily correspond to the X axis direction and the Y axis direction of the crystal orientation of the piezoelectric substrate.

  As shown in FIGS. 1, 2 (a), and 2 (b), a temperature compensation film 14 is bonded to the support substrate 10 via a bonding film 11. A piezoelectric substrate 12 is bonded on the temperature compensation film 14. The thicknesses of the piezoelectric substrate 12 and the temperature compensation film 14 are T1 and T2, respectively.

  An acoustic wave resonator 20 is provided on the piezoelectric substrate 12. The acoustic wave resonator 20 includes an IDT 22 and a reflector 24. The reflectors 24 are provided on both sides of the IDT 22 in the X direction. The IDT 22 and the reflector 24 are formed by the metal film 13 on the piezoelectric substrate 12.

  The IDT 22 includes a pair of opposing comb electrodes 18. The comb electrode 18 includes a plurality of electrode fingers 15 and a bus bar 16 to which the plurality of electrode fingers 15 are connected. A region where the electrode fingers 15 of the pair of comb electrodes 18 intersect is an intersecting region 25. The length of the intersecting region 25 is the opening length. The pair of comb-shaped electrodes 18 are provided so as to face each other so that the electrode fingers 15 are substantially staggered in at least a part of the intersecting region 25. The elastic wave excited by the plurality of electrode fingers 15 in the intersecting region 25 propagates mainly in the X direction. The pitch of the two electrode fingers 15 of the comb electrode 18 is substantially the wavelength λ of the elastic wave. The reflector 24 reflects the elastic wave (surface acoustic wave) excited by the electrode finger 15 of the IDT 22. As a result, the elastic wave is confined in the intersecting region 25 of the IDT 22.

The piezoelectric substrate 12 is, for example, a single crystal lithium tantalate (TaLiO ₃ ) substrate or a single crystal lithium niobate (NbLiO ₃ ) substrate, for example, a rotating Y-cut X-propagating lithium tantalate substrate or a rotating Y-cut X-propagating niobic acid. Lithium substrate.

The temperature compensation film 14 has a phase velocity temperature coefficient with a sign opposite to the sign of the temperature coefficient of the phase velocity of the piezoelectric substrate 12 (that is, the temperature coefficient of the elastic modulus). For example, the temperature coefficient of the phase velocity of the piezoelectric substrate 12 is negative, and the temperature coefficient of the phase velocity of the temperature compensation film 14 is positive. The temperature compensation film 14 is, for example, a silicon oxide (SiO ₂ ) film containing no additive or an additive element, and is amorphous.

The support substrate 10 is, for example, a sapphire substrate, a spinel substrate, a silicon substrate, a quartz substrate, a quartz substrate, or an alumina substrate. The sapphire substrate is a single crystal Al ₂ O ₃ substrate, the spinel substrate is a single crystal or polycrystalline MgAl ₂ O ₄ substrate, the silicon substrate is a single crystal Si substrate, and the crystal substrate is a single crystal SiO ₂ substrate, The quartz substrate is a polycrystalline SiO ₂ substrate, and the alumina substrate is a polycrystalline Al ₂ O ₃ substrate. The linear thermal expansion coefficient in the X direction of the support substrate 10 is smaller than the linear thermal expansion coefficient in the X direction of the piezoelectric substrate 12.

  The bonding film 11 is a layer for bonding the support substrate 10 and the temperature compensation film 14. For example, as described in Patent Document 1, the upper surface of the support substrate 10 and the lower surface of the temperature compensation film 14 are activated by an ion beam, a neutral beam, or plasma. At this time, an amorphous layer is formed on each of the upper surface of the support substrate 10 and the lower surface of the temperature compensation film 14. By bonding the amorphous layer, the lower surface of the temperature compensation film 14 is bonded to the upper surface of the support substrate 10. In this case, the thickness of the bonding film 11 is 1 nm to 8 nm. The bonding film 11 may be an insulating film having a thickness of 1 nm to 100 nm. The bonding film 11 may not be provided. A bonding film 11 may be provided between the temperature compensation film 14 and the piezoelectric substrate 12.

  The metal film 13 is a film containing, for example, Al (aluminum) or Cu (copper) as a main component, for example, an Al film or a Cu film. An adhesion film such as a Ti (titanium) film or a Cr (chromium) film may be provided between the electrode finger 15 and the piezoelectric substrate 12. The adhesion film is thinner than the electrode finger 15. An insulating film may be provided so as to cover the electrode fingers 15. The insulating film functions as a protective film or a temperature compensation film.

[Description of the reason for providing a temperature compensation film]
Hereinafter, the reason why the frequency temperature coefficient is close to 0 in the first embodiment will be described. The frequency temperature coefficient TCF is expressed by the following equation.
TCF = TCV-CTE
TCV (Temperature Coefficient of Velocity) is a temperature coefficient of sound velocity (phase velocity). CTE (Coefficient of Thermal Expansion) is a thermal expansion coefficient. The linear thermal expansion coefficient in the X-axis direction of the X-propagating lithium tantalate substrate used as the piezoelectric substrate 12 is about 16 ppm / K. The linear thermal expansion coefficient of the C-axis (axis parallel to the X-axis) of the sapphire substrate used as the support substrate 10 is about 7.7 ppm / K. Therefore, when the thickness of the piezoelectric substrate 12 is reduced, the CTE as the acoustic wave resonator 20 approaches the CTE of the support substrate 10. However, it cannot be smaller than the CTE of the support substrate 10.

  Generally, the linear thermal expansion coefficient is positive regardless of the material. Moreover, TCV is negative in the material used as the general piezoelectric substrate 12. For this reason, TCF becomes negative. Therefore, a material having a positive TCV is used as the temperature compensation film 14. Thereby, the positive TCV of the temperature compensation film 14 compensates for the negative TCV of the piezoelectric substrate 12 and the -CTE of the support substrate 10. Therefore, the TCF can be made near zero.

[Description of thickness range of piezoelectric substrate 12 and temperature compensation film 14]
Next, preferable thicknesses of the piezoelectric substrate 12 and the temperature compensation film 14 will be described. FIG. 3 is a cross-sectional view of the acoustic wave resonator according to the first embodiment. As shown in FIG. 3, the electrode finger 15 of the IDT 22 excites an elastic wave 50. In addition, the elastic wave 50 in the figure shows an image of displacement, and is different from the actual displacement of the elastic wave. For example, when the piezoelectric substrate 12 is a rotating Y-cut X-propagating lithium tantalate substrate, the IDT 22 mainly excites SH (Shear Horizontal) waves. The SH wave is a wave parallel to the surface of the piezoelectric substrate 12 and displaced in a direction orthogonal to the propagation direction of the SH wave. In order for the TCV of the temperature compensation film 14 to compensate for the negative TCV of the piezoelectric substrate 12 and the −CTE of the support substrate 10, it is required that the surface acoustic wave displacement is distributed in the temperature compensation film 14.

  Therefore, the total displacement distribution at the resonance frequency in the substrate was simulated. 4A and 4B are cross-sectional views of the acoustic wave resonator in simulations A and B. FIG. As shown in FIG. 4A, in the simulation A, the substrate is only the 42 ° rotated Y-cut X-propagating lithium tantalate substrate that is the piezoelectric substrate 12, and the support substrate 10 and the temperature compensation film 14 are not provided. As shown in FIG. 4B, in simulation B, the substrate is a sapphire substrate that is the support substrate 10 and a 42 ° rotation Y-cut X-propagation lithium tantalate substrate that is the piezoelectric substrate 12, and the temperature compensation film 14 is not provided. . The thickness T1 of the piezoelectric substrate 12 was about 0.7λ. In both simulations A and B, the surface of the piezoelectric substrate 12 in contact with the electrode finger 15 was set to 0, and the depth direction of the substrate was set to the position Z.

  FIGS. 5A and 5B are diagrams showing the total displacement distribution with respect to the position Z in the simulations A and B. FIG. The double-headed arrows indicating the ranges of the piezoelectric substrate 12 and the support substrate 10 are shown on FIGS. 5 (a) and 5 (b). As shown in FIG. 5A, in the simulation A, most of the displacement falls within Z / λ of 2 or less. In particular, most of the displacement distribution falls within Z / λ of 1.5 or less. This indicates that the surface acoustic wave propagates in a range from the surface of the piezoelectric substrate 12 to about 2λ (especially 1.5λ). As shown in FIG. 5B, in the simulation B, most of the displacement falls within Z / λ of 1 or less. In particular, almost no displacement is distributed in the support substrate 10. This is because the phase velocity of the support substrate 10 is large.

  As in the above simulation, the surface acoustic wave propagates within 2λ (especially 1.5λ) from the substrate surface. Therefore, in the first embodiment, in order for the temperature compensation film 14 to function, the temperature compensation film 14 is required to exist within 2λ (particularly 1.5λ) from the substrate surface.

Next, the bulk wave will be described. FIG. 6A to FIG. 6C are cross-sectional views illustrating bulk waves. As shown in FIG. 6A, when the substrate is only the piezoelectric substrate 12, the IDT 22 excites a surface acoustic wave 52 such as an SH wave on the surface of the piezoelectric substrate 12. The thickness T4 where the surface acoustic wave 52 is displaced is about 2λ. When the IDT 22 excites the surface acoustic wave 52, the IDT 22 emits a bulk wave 54 into the piezoelectric substrate 12. The bulk wave 54 is 1/10 the size of the surface acoustic wave 52 in the main mode. The thickness T5 where the bulk wave 54 exists is about 10λ. When the bulk wave 54 propagates in the piezoelectric substrate 12, the energy of the surface acoustic wave 52 is lost as the bulk wave 54. Therefore, the loss of the acoustic wave resonator is increased.

  As shown in FIG. 6B, a temperature compensation film 14 is provided under the piezoelectric substrate 12, and a support substrate 10 is provided under the temperature compensation film 14. The thickness T1 of the piezoelectric substrate 12 is smaller than the thickness T4. Thereby, the displacement of the surface acoustic wave 52 is distributed to both the piezoelectric substrate 12 and the temperature compensation film 14. Therefore, TCF can be suppressed. When the thickness T2 of the temperature compensation film 14 is large, the bulk wave 54 propagates through the temperature compensation film 14. Thereby, the energy of the surface acoustic wave 52 is lost as the bulk wave 54. Therefore, the loss of the acoustic wave resonator is increased. As indicated by the arrow 56, the bulk wave does not propagate in the support substrate 10.

  As shown in FIG. 6C, in Example 1, the temperature compensation film 14 is thinned, and the total thickness of the thicknesses T1 and T2 is made smaller than the thickness T4. The support substrate 10 has a phase velocity greater than the phase velocity of the piezoelectric substrate 12 and the temperature compensation film 14. For example, the phase velocity of fast transverse waves for lithium tantalate, silicon oxide and sapphire are about 4211 m / sec, about 5840 m / sec and 6761 m / sec. For this reason, the bulk wave does not propagate in the support substrate 10 as indicated by the arrow 56. Both the surface acoustic wave 52 and the bulk wave 54 are confined in the piezoelectric substrate 12 and the temperature compensation film 14. Therefore, the loss of the acoustic wave resonator can be suppressed. Further, spurious due to the bulk wave can be suppressed.

[Experiment]
The acoustic wave resonators of Example 1 and Comparative Example 1 were produced. The production conditions are as follows.
Example 1
Support substrate 10: Single crystal sapphire substrate having an R surface of 500 μm as the upper surface Temperature compensation film 14: Silicon oxide (SiO ₂ ) film having a thickness T2 of 1 μm Piezoelectric substrate 12: 42 ° rotation with a thickness T1 of 1 μm Y-cut X-propagating lithium tantalate substrate Wavelength of elastic wave λ: 4 μm
Comparative Example 1
Support substrate 10: Single crystal sapphire substrate having an R surface of 500 μm as the upper surface Temperature compensation film 14: None Piezoelectric substrate 12: 42 ° rotated Y-cut X-propagation lithium tantalate substrate with a thickness of 3 μm Wavelength λ of elastic wave : 4μm

  The resonance frequency TCFs of Example 1 and Comparative Example 1 were measured. In Example 1, TCF = 6 ppm / K, and in Comparative Example 1, TCF = −13.4 ppm / K.

  FIG. 7 is a diagram illustrating the admittance with respect to the frequency of the acoustic wave resonator according to the first embodiment. As shown in FIG. 7, the admittance characteristics hardly change at 25 ° C. and 85 ° C. There is almost no temperature dependence of the resonance frequency fr and the antiresonance frequency fa. Thus, by providing the temperature compensation film 14, the TCF can be brought close to zero.

[Production Method of Example 1]
A method for manufacturing the acoustic wave resonator according to the first embodiment will be described. FIGS. 8A to 10B are cross-sectional views illustrating the method for manufacturing the acoustic wave resonator according to the first embodiment. As shown in FIG. 8A, the piezoelectric substrate 12 is prepared. As shown in FIG. 8B, the temperature compensation film 14 is formed on the piezoelectric substrate 12 by using a sputtering method, a vacuum deposition method, or a CVD (Chemical Vapor Deposition) method. As shown in FIG. 8C, the bonding film 11 is formed on the temperature compensation film 14 using a sputtering method, a vacuum evaporation method, or a CVD method. The bonding film 11 is, for example, a silicon film, an aluminum oxide film, or an aluminum nitride film. As shown in FIG. 8D, the upper surface of the support substrate 10 and the lower surface of the bonding film 11 are activated. The activation method is the same as that of Patent Document 1, for example. As shown in FIG. 8E, the support substrate 10 and the bonding film 11 are bonded at room temperature.

  As shown in FIG. 9A, the upper surface of the piezoelectric substrate 12 is thinned by using, for example, a CMP (Chemical Mechanical Polishing) method. As shown in FIG. 9B, a metal film 13 is formed on the upper surface of the piezoelectric substrate 12. An elastic wave resonator 20 is formed by the metal film 13. As shown in FIG. 9C, a protective film 26 is formed so as to cover the acoustic wave resonator 20. The protective film 26 is an insulating film such as a silicon nitride film or a silicon oxide film. As shown in FIG. 9D, a wiring layer 28 is formed on the metal film 13. The wiring layer 28 is, for example, a copper layer or a gold layer. A chip is formed by dividing into individual pieces.

  As shown in FIG. 10A, in the chip 45, the acoustic wave resonator 20 and the pad 32 are provided below the piezoelectric substrate 12, and the bump 30 is provided below the pad 32. The pad 32 is, for example, a part of the wiring layer in FIG. The bump 30 is, for example, a gold bump or a solder bump. Illustration of the protective film 26 is omitted. Pads 42 are provided on the package substrate 40, and terminals 44 are provided below the package substrate 40. The bump 30 is bonded to the pad 42. As shown in FIG. 10B, a sealing portion 48 is formed on the package substrate 40 so as to cover the chip 45. The sealing part 48 is, for example, an insulator such as resin or a metal such as solder. The sealing unit 48 seals the acoustic wave resonator 20 in the gap 43. Thereby, an elastic wave device can be manufactured.

  According to the first embodiment, the piezoelectric substrate 12 is provided on the support substrate 10 and has a phase velocity smaller than the phase velocity of the support substrate 10. The temperature compensation film 14 is provided between the support substrate 10 and the piezoelectric substrate 12, and has a phase speed smaller than the phase speed of the support substrate 10 and a sign opposite to the sign of the temperature coefficient (TCV) of the phase speed of the piezoelectric substrate 12. Temperature coefficient (TCV) of the phase velocity of The pair of comb-shaped electrodes 18 are provided on the piezoelectric substrate 12, each having a plurality of electrode fingers 15, and the average pitch of the electrode fingers 15 of one comb-shaped electrode is the total thickness of the temperature compensation film 14 and the piezoelectric substrate 12. It is 1/2 or more of (T1 + T2).

  The sign of TCV of the temperature compensation film 14 is opposite to the sign of TCV of the piezoelectric substrate 12. Thereby, TCF can be suppressed as demonstrated in FIG. The average pitch of the electrode fingers 15 (which substantially corresponds to the wavelength λ of the elastic wave) is set to ½ or more of the thickness T1 + T2. Thereby, as shown in FIG. 5A and FIG. 5B, the elastic wave propagates through the piezoelectric substrate 12 and the temperature compensation film 14, and thus TCF can be suppressed. Therefore, frequency temperature characteristics can be improved. Furthermore, as described with reference to FIGS. 6A to 6C, loss due to the bulk wave can be suppressed.

  The average pitch of the electrode fingers 15 can be calculated by dividing the length of the elastic wave resonator 20 in the X direction by the logarithm of the electrode fingers 15 (1/2 of the number of electrode fingers 15). The average pitch of the electrode fingers 15 is preferably at least 1 / 1.5 times the total thickness (T1 + T2) of the temperature compensation film 14 and the piezoelectric substrate 12, more preferably at least 1 / 1.2 times, and more preferably at least 1. preferable. In order to propagate the surface acoustic wave through the piezoelectric substrate 12 and the temperature compensation film 14, the average pitch of the electrode fingers 15 is preferably 1 / 0.1 times or less of the thickness (T1 + T2), and preferably 1 / 0.2 times or less. More preferably, 1 times or less is more preferable.

  The average pitch of the electrode fingers 15 is larger than the thickness T1 of the piezoelectric substrate 12. Thereby, as shown in FIGS. 5A and 5B, the surface acoustic wave displacement distribution can be present in the temperature compensation film 14. The average pitch of the electrode fingers 15 is preferably at least 1 / 0.8 times the thickness T1 of the piezoelectric substrate 12, more preferably at least 1 / 0.6 times, and even more preferably at least 1 / 0.5 times. In order to propagate the surface acoustic wave through the piezoelectric substrate 12, the average pitch of the electrode fingers 15 is preferably 1 / 0.1 times or less, more preferably 1 / 0.2 times or less of the thickness T1 of the piezoelectric substrate 12. /0.3 times or less is more preferable.

  The linear thermal expansion coefficient of the support substrate 10 in the arrangement direction of the plurality of electrode fingers 15 is smaller than the linear thermal expansion coefficient of the piezoelectric substrate 12 in the arrangement direction. Thereby, CTE can be made small.

  In order to suppress TCF, the ratio of the thickness T1 of the piezoelectric substrate 12 to T1 + T2 is preferably 0.1 or more and 0.9 or less, more preferably 0.2 or more and 0.8 or less, and 0.3 or more and 0 .7 or less is more preferable. As in the experiment of FIG. 7, it is preferable that the thicknesses T1 and T2 are substantially equal to the extent that T1 / (T1 + T2) is 0.4 or more and 0.6 or less.

  The piezoelectric substrate 12 is a lithium tantalate substrate or a lithium niobate substrate. The support substrate 10 is a sapphire substrate, a spinel substrate, a silicon substrate, a quartz substrate, a quartz substrate, or an alumina substrate, and is a single crystal substrate or a polycrystalline substrate. The temperature compensation film 14 is a silicon oxide film. Thereby, frequency temperature characteristics can be improved and loss can be suppressed.

  As described in FIG. 3, when the pair of comb-shaped electrodes 18 excites surface acoustic waves (especially SH waves), bulk waves are likely to be generated. Therefore, when the surface acoustic wave is an SH wave, T1 + T2 is preferably set to 1.5λ or less. In order to make the surface acoustic wave into an SH wave, the piezoelectric substrate 12 is preferably a 20 ° to 48 ° rotated Y-cut X-propagating lithium tantalate substrate.

  FIG. 11A is a circuit diagram of a filter according to the second embodiment. As shown in FIG. 11A, one or more series resonators S1 to S3 are connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 and P2 are connected in parallel between the input terminal Tin and the output terminal Tout. The elastic wave resonator of the first embodiment can be used for at least one of the one or more series resonators S1 to S3 and the one or more parallel resonators P1 and P2. The number of resonators of the ladder type filter can be set as appropriate.

[Modification 1 of Embodiment 2]
FIG. 11B is a plan view illustrating a filter according to the first modification of the second embodiment. As shown in FIG. 11B, the multimode filter DMS includes IDTs 22a to 22c and a reflector 24. The IDTs 22 a to 22 c and the reflector 24 are provided on the piezoelectric substrate 12. IDTs 22a to 22c are arranged in the propagation direction of the surface acoustic wave. A reflector 24 is provided outside the IDTs 22a to 22c. One end of the IDT 22b is connected to the input terminal Tin, and the other end is connected to the ground terminal. One end of the IDT 22a and one end of the IDT 22c are commonly connected to the output terminal Tout. The other end of the IDT 22a and the other end of the IDT 22c are connected to a ground terminal. The structure of the elastic wave resonator of the first embodiment can be used for the multimode filter DMS.

[Modification 2 of Embodiment 2]
FIG. 11C is a circuit diagram of a duplexer according to the second modification of the second embodiment. As shown in FIG. 11C, a transmission filter 46 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 47 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 46 passes a signal in the transmission band among the high-frequency 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 47 passes signals in the reception band among the high-frequency signals input from the common terminal Ant to the reception terminal Rx as reception signals, and suppresses signals of other frequencies. At least one of the transmission filter 46 and the reception filter 47 can be the filter of the second embodiment and the first modification thereof.

  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 Support substrate 11 Bonding film 12 Piezoelectric substrate 14 Temperature compensation film 15 Electrode finger 18 Comb-shaped electrode 20 Elastic wave resonator 22 IDT

Claims (9)

A support substrate;
A piezoelectric substrate provided on the support substrate and having a phase velocity smaller than the phase velocity of the support substrate;
A phase velocity that is provided between the support substrate and the piezoelectric substrate and that is smaller than the phase velocity of the support substrate, and a temperature coefficient of a phase velocity that is opposite to the sign of the temperature coefficient of the phase velocity of the piezoelectric substrate; A temperature compensation film having,
A pair of electrode fingers provided on the piezoelectric substrate, each having a plurality of electrode fingers, wherein an average pitch of the electrode fingers of one comb-shaped electrode is ½ or more of a total thickness of the temperature compensation film and the piezoelectric substrate A comb electrode;
An elastic wave resonator comprising:   The acoustic wave resonator according to claim 1, wherein the average pitch is larger than a thickness of the piezoelectric substrate.   3. The acoustic wave resonator according to claim 1, wherein a linear thermal expansion coefficient of the support substrate in the arrangement direction of the plurality of electrode fingers is smaller than a linear thermal expansion coefficient of the piezoelectric substrate in the arrangement direction.   The elastic wave resonator according to any one of claims 1 to 3, wherein a thickness of the piezoelectric substrate and a thickness of the temperature compensation film are substantially equal. The piezoelectric substrate is a lithium tantalate substrate or a lithium niobate substrate,
The support substrate is a sapphire substrate, a spinel substrate, a silicon substrate, a quartz substrate, a quartz substrate, or an alumina substrate, and is a single crystal substrate or a polycrystalline substrate,
The acoustic wave resonator according to claim 1, wherein the temperature compensation film is a silicon oxide film.   The acoustic wave resonator according to claim 1, wherein the pair of comb-shaped electrodes excites a surface acoustic wave.   The elastic wave according to any one of claims 1 to 6, wherein an average pitch of the electrode fingers of the one comb-shaped electrode is 1 / 1.5 or more of a total thickness of the temperature compensation film and the piezoelectric substrate. Resonator.   The filter containing the elastic wave resonator as described in any one of Claim 1 to 7.   A multiplexer including the filter according to claim 8.

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