JP2019186655A - Elastic wave device, multiplexer, and composite substrate - Google Patents

Abstract

To provide an elastic wave resonator having a different resonance frequency.SOLUTION: A elastic wave device includes a support substrate, a piezoelectric substrate bonded onto the support substrate and having a first region having a first thickness and a second region having a second thickness greater than the first thickness, a first acoustic wave resonator including a pair of first comb electrodes provided on the first region of the piezoelectric substrate, each having a plurality of first electrode fingers and in which an average pitch of one first electrode finger of the pair of first comb electrodes is larger than the first thickness, and a second acoustic wave resonator provided on the second region of the piezoelectric substrate and including a pair of second comb electrodes each having a plurality of second electrode fingers.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an acoustic wave device, a multiplexer, and a composite substrate. For example, the present invention relates to an acoustic wave device, a multiplexer, and a composite substrate having a piezoelectric substrate bonded on a support substrate.

  It is known to join a piezoelectric substrate on a support substrate in order to improve frequency temperature characteristics of an acoustic wave device using surface acoustic waves of the piezoelectric substrate. It is known that spurious can be suppressed by setting the thickness of the piezoelectric substrate to be equal to or less than the wavelength of the surface acoustic wave (for example, Patent Document 1). It is known to provide a low sound velocity film whose bulk sound velocity is lower than that of a piezoelectric substrate between a support substrate and a piezoelectric substrate (for example, Patent Document 2). It is known to vary the thickness of the piezoelectric substrate (for example, Patent Documents 3 to 5).

JP 2017-34363 A International Publication No. 2012/086639 JP 2013-1557839 A JP 2005-223610 A JP-A-5-304436 Special table 2018-506930 gazette

  In order to provide surface acoustic wave resonators with different resonance frequencies on the same substrate, the pitch of the electrode fingers is varied, the thickness of the electrode fingers is varied, and / or the thickness of the insulating film covering the electrode fingers is varied. , Etc. However, if the resonance frequencies are greatly varied, the manufacturing method is complicated and / or the manufacturing method is restricted.

  The present invention has been made in view of the above problems, and an object thereof is to provide an acoustic wave resonator having different resonance frequencies.

  The present invention relates to a piezoelectric substrate having a support substrate, a first region having a first thickness bonded to the support substrate, and a second region having a second thickness greater than the first thickness. A pair of first comb electrodes provided on the first region of the piezoelectric substrate, each having a plurality of first electrode fingers, and an average of one first electrode finger of the pair of first comb electrodes A second acoustic wave resonator having a pitch greater than the first thickness, and a second comb-shaped electrode provided on the second region of the piezoelectric substrate and having a plurality of second electrode fingers, respectively. An elastic wave device comprising: an elastic wave resonator.

  The said structure WHEREIN: The average pitch of one 2nd electrode finger of a pair of said 2nd comb-shaped electrode can be set as a structure larger than a said 2nd thickness.

  In the above configuration, an average pitch of one second electrode finger of the pair of second comb electrodes may be smaller than the second thickness.

  In the above configuration, the piezoelectric substrate may be directly bonded to the support substrate through an amorphous layer.

  The said structure WHEREIN: It can be set as the structure provided with the intermediate | middle layer pinched | interposed into the said piezoelectric substrate and the said support substrate.

  In the above configuration, the third thickness of the intermediate layer between the first region of the piezoelectric substrate and the support substrate is the same as that of the intermediate layer between the second region of the piezoelectric substrate and the support substrate. A configuration greater than the fourth thickness may be employed.

  The said structure WHEREIN: The surface on the opposite side of the said intermediate | middle layer of the said 1st area | region and the said 2nd area | region of the said piezoelectric substrate can be set as a substantially flat structure.

  In the above configuration, the pair of first comb electrodes and the pair of second comb electrodes may be configured to excite SH waves.

  The said structure WHEREIN: The said piezoelectric substrate can be set as the structure which is a Y cut X propagation lithium tantalate board | substrate which has a cut angle of 20 degrees or more and 48 degrees or less.

  The present invention includes the above acoustic wave device, a first filter including one or more first acoustic wave resonators, and a pass band that does not overlap with a pass band of the first filter. And a second filter including a second acoustic wave resonator.

  The present invention includes a support substrate, a first region having a first thickness bonded to the support substrate through an amorphous layer, and a second region having a second thickness greater than the first thickness. And a third thickness between the first region of the piezoelectric substrate and the support substrate is between the second region of the piezoelectric substrate and the support. An intermediate layer having a thickness greater than a fourth thickness between the substrate and the substrate.

  According to the present invention, it is possible to provide elastic wave resonators having different resonance frequencies.

FIG. 1A is a plan view of an acoustic wave resonator, and FIG. 1B is a cross-sectional view taken along line AA of FIG. 2A and 2B are cross-sectional views of the acoustic wave resonator according to the first comparative example. FIG. 3 is a cross-sectional view of an acoustic wave device according to Comparative Example 2. FIG. 4A and FIG. 4B are diagrams showing the resonance frequency fr with respect to the thickness T / pitch L of the piezoelectric substrate. FIG. 5A and FIG. 5B are cross-sectional views of the acoustic wave device according to the first embodiment. FIG. 6 is a circuit diagram of a duplexer using the first embodiment. FIG. 7 is a plan view of the substrate 10 according to the first embodiment. 8A to 8E are cross-sectional views (part 1) illustrating the method for manufacturing the acoustic wave device according to the first embodiment. FIG. 9A to FIG. 9D are cross-sectional views (part 2) illustrating the method for manufacturing the acoustic wave device according to the first embodiment. FIG. 10A and FIG. 10B are cross-sectional views of the acoustic wave device according to the second embodiment. FIG. 11A and FIG. 11B are cross-sectional views of the acoustic wave device according to the first modification of the second embodiment. 12A to 12D are cross-sectional views (part 1) illustrating the method for manufacturing the acoustic wave device according to the first modification of the second embodiment. 13A to 13C are cross-sectional views (part 2) illustrating the method for manufacturing the acoustic wave device according to the first modification of the second embodiment. 14A and 14B are cross-sectional views (part 3) illustrating the method for manufacturing the acoustic wave device according to the first modification of the second embodiment.

[Description of elastic wave resonator]
FIG. 1A is a plan view of an acoustic wave resonator, and FIG. 1B is a cross-sectional view taken along line AA of FIG. The arrangement direction of the electrode fingers 14 is the X direction, the extending direction of the electrode fingers 14 is the Y direction, and the normal direction of the upper surface of the piezoelectric substrate 10a is the Z direction. The X direction, the Y direction, and the Z direction do not necessarily correspond to the X axis direction, the Y axis direction, and the Z axis direction of the crystal orientation of the piezoelectric substrate 10a.

  As shown in FIGS. 1A and 1B, in the acoustic wave resonator 20, the substrate 10 includes a support substrate 10b and a piezoelectric substrate 10a bonded to the support substrate 10b. An IDT 18 and a reflector 19 are formed on the piezoelectric substrate 10a. The IDT 18 and the reflector 19 are formed by the metal film 12 formed on the substrate 10. The IDT 18 includes a pair of opposing comb electrodes 16. Each of the pair of comb-shaped electrodes 16 includes a plurality of electrode fingers 14 and a bus bar 15 to which the plurality of electrode fingers 14 are connected. A region where the electrode fingers 14 of the pair of comb electrodes 16 overlap is an intersecting region 56. In at least a part of the intersecting region 56, the electrode fingers of one comb electrode and the electrode fingers of the other comb electrode of the pair of comb electrodes 16 are provided to face each other in an almost alternate manner. .

  The elastic wave excited by the electrode finger 14 in the intersecting region 56 propagates mainly in the X direction. The pitch L of the electrode fingers 14 of the one comb-shaped electrode 16 is substantially the wavelength λ of the elastic wave. The piezoelectric substrate 10a is, for example, a lithium tantalate substrate or a lithium niobate substrate, such as a rotating Y-cut X-propagating lithium tantalate substrate or a rotating Y-cut X-propagating lithium niobate substrate. The support substrate 10b is, for example, a sapphire substrate, a spinel substrate, an alumina substrate, a glass substrate, a crystal substrate, or a silicon substrate. The linear thermal expansion coefficient of the support substrate 10b is smaller than the linear thermal expansion coefficient of the piezoelectric substrate 10a. Thereby, the frequency temperature coefficient (TCF: Temperature Coefficient of Frequency) of an elastic wave resonator can be suppressed. The metal film 12 is, for example, an aluminum film or a copper film. An insulating film functioning as a protective film or a temperature compensation film may be provided on the substrate 10 so as to cover the electrode fingers 14.

[Comparative Example 1]
2A and 2B are cross-sectional views of the acoustic wave resonator according to the first comparative example. As shown in FIG. 2A, the acoustic wave resonator 20a and the wiring 22a are provided on the piezoelectric substrate 10a. As shown in FIG. 2B, the acoustic wave resonator 20b and the wiring 22b are provided on the piezoelectric substrate 10a. The acoustic wave resonators 20a and 20b are used for a reception filter and a transmission filter of a duplexer, for example. The pass bands do not overlap between the transmission filter and the reception filter. For this reason, the resonant frequencies of the acoustic wave resonators 20a and 20b are greatly different. The acoustic wave resonator 20b has a resonance frequency lower than that of 20a.

  In order to make the resonance frequency of the elastic wave resonator 20b lower than the resonance frequency of the elastic wave resonator 20a, the pitch L2 of the electrode fingers 14 of the elastic wave resonator 20b is larger than the pitch L1 of the electrode fingers 14 of the elastic wave resonator 20a. . The film thickness H2 of the electrode finger 14 of the acoustic wave resonator 20b is larger than the film thickness H1 of the electrode finger 14 of the acoustic wave resonator 20a. For example, a duplexer can be formed by mounting the chip on which the acoustic wave resonator 20a is formed and the chip on which the acoustic wave resonator 20b is formed on a package. However, when a plurality of chips are mounted on a package, an elastic wave device such as a duplexer becomes large.

[Comparative Example 2]
FIG. 3 is a cross-sectional view of an acoustic wave device according to Comparative Example 2. As shown in FIG. 3, the acoustic wave resonators 20 a and 20 b are provided on a single substrate 10. An insulating film 24 is provided so as to cover the electrode fingers 14. The insulating film 24 is, for example, a silicon oxide film or a silicon nitride film, and functions as a protective film or a temperature compensation film. In order to make the resonance frequencies of the acoustic wave resonators 20a and 20b different, the film thicknesses H1 ′ and H2 ′ of the insulating film 24 on the electrode fingers 14 may be made different.

  When the acoustic wave resonators 20a and 20b are formed on the single substrate 10 as in Comparative Example 2, the acoustic wave device can be reduced in size. In order to make the resonance frequencies of the acoustic wave resonators 20a and 20b greatly different, the pitch of the electrode fingers, the film thickness of the electrode fingers 14 and / or the film of the insulating film 24 covering the electrode fingers 14 are different. There are methods such as varying the thickness. However, if the pitches L1 and L2 are made to differ greatly, the machining accuracy is lowered. Further, if the film thicknesses H1 and H2 and / or the film thicknesses H1 ′ and H2 ′ are made to differ greatly, the manufacturing process becomes complicated. Therefore, a method of making the resonance frequency greatly different by a method other than the above was examined.

[simulation]
The resonance frequency of the acoustic wave resonator 20 with respect to the thickness T of the piezoelectric substrate 10a was simulated using a three-dimensional finite element method. The simulation conditions are as follows.
Support substrate 10b: Sapphire substrate having a thickness of 500 μm Piezoelectric substrate 10a: 42 ° rotated Y-cut X-propagating lithium tantalate substrate having a thickness T Metal film 12: Aluminum film having a thickness of 400 nm
Number of pairs of electrode fingers 14: 100 pairs Opening length (length of crossing region 56): 25λ

  FIG. 4A and FIG. 4B are diagrams showing the resonance frequency fr with respect to the thickness T / pitch L of the piezoelectric substrate. FIG. 4B is an enlarged view of a range A in FIG. The dots indicate simulation results, and the curve connecting the dots is an approximate curve. The thickness T of the piezoelectric substrate 10a is normalized by the pitch L. As shown in FIGS. 4A and 4B, when the thickness T of the piezoelectric substrate 10a is equal to or greater than the pitch L, the resonance frequency fr is substantially constant. At this time, the wavelength of the surface acoustic wave excited by the electrode finger 14 is substantially the pitch L. When the thickness T of the piezoelectric substrate 10a is equal to or less than the pitch L, the resonance frequency fr increases.

  When the thickness T is equal to or greater than the pitch L, the electrode finger 14 excites a bulk wave when exciting a surface acoustic wave (for example, SH (Shear Horizontal) wave). When this bulk wave is reflected at the interface between the piezoelectric substrate 10a and the support substrate 10b, it becomes spurious. Further, since the bulk wave is excited, the loss of the acoustic wave resonator increases. On the other hand, when the thickness T is equal to or less than the pitch L, spurious and loss due to the bulk wave are suppressed. As shown in FIGS. 4A and 4B, the reason why the resonance frequency fr greatly depends on the thickness T when the thickness T is equal to or less than the pitch L is not clear, but is due to suppression of bulk waves. It is thought that.

  Examples will be described based on simulation results. FIG. 5A and FIG. 5B are cross-sectional views of the acoustic wave device according to the first embodiment. As shown in FIGS. 5A and 5B, the piezoelectric substrate 10a has a region 30 having a thickness T1 and a region 32 having a thickness T2. An elastic wave resonator 20 a and a wiring 22 a are provided on the region 30, and an elastic wave resonator 20 b and a wiring 22 b are provided on the region 32. The pitches L1 and L2 of the electrode fingers 14 of the acoustic wave resonators 20a and 20b are approximately the same. An insulating film 24 is provided so as to cover the electrode fingers 14 of the acoustic wave resonators 20a and 20b. In the acoustic wave resonators 20a and 20b, the film thickness of the electrode finger 14 is approximately the same as the manufacturing error, and the film thickness of the insulating film 24 is approximately the same as the manufacturing error. Of the thicknesses T1 and T2, at least the thickness T1 is smaller than the pitch L1. Thereby, even if the film thickness of the electrode finger 14 and the insulating film 24 is substantially the same, the resonant frequencies of the acoustic wave resonators 20a and 20b can be greatly different. The insulating film 24 may be thinner or thicker than the electrode finger 14. Further, the insulating film 24 may not be provided.

  FIG. 6 is a circuit diagram of a duplexer using the first embodiment. As shown in FIG. 6, a transmission filter 50 is connected between the common terminal Ant and the transmission terminal Tx, and a reception filter 52 is connected between the common terminal Ant and the reception terminal Rx. In the transmission filter 50, one or more series resonators S1 to S4 are connected in series between the common terminal Ant and the transmission terminal Tx, and one or parallel resonators P1 to P3 are connected in parallel.

  In the reception filter 52, series resonators S5, DMS1, and DMS2 are connected in series between the common terminal Ant and the reception terminal Rx. DMS1 and DMS2 are multimode filters such as a double mode surface acoustic wave filter. DMS1 and DMS2 each have three IDTs 18a to 18c. IDTs 18a to 18c are arranged in the propagation direction of the elastic wave. One end of the IDT 18b of the DMS1 is electrically connected to the series resonator S5, and the other end is grounded. One ends of IDTs 18a and 18c of DMS1 are electrically connected to one ends of IDTs 18a and 18c of DMS2, respectively. The other ends of IDTs 18a and 18c of DMS1 and DMS2 are grounded. One end of the IDT 18b of the DMS 2 is electrically connected to the receiving terminal Rx, and the other end is grounded.

  The transmission filter 50 passes signals in the transmission band among the high-frequency signals input to the transmission terminal Tx to the common terminal Ant, and suppresses signals in other frequency bands. The reception filter 52 passes signals in the reception band among the high-frequency signals input to the common terminal Ant to the reception terminal Rx, and suppresses signals in other frequency bands. Although the transmission filter 50 includes a ladder type filter and the reception filter 52 includes a multimode filter, the transmission filter 50 includes a multimode filter and may include the reception filter 52. Both the transmission filter 50 and the reception filter 52 may include ladder type filters. The number of resonators in the transmission filter 50 and the reception filter 52 can be set as appropriate.

  FIG. 7 is a plan view of the substrate 10 according to the first embodiment. As shown in FIG. 7, the acoustic wave resonator 20a and the wiring 22a are provided on the region 30 of the piezoelectric substrate 10a. The acoustic wave resonator 20a includes a series resonator S5, DMS1, and DMS2. The wiring 22a is connected to the acoustic wave resonator 20a. The wiring 22c crosses the wiring 22a. The wiring 22a includes a common pad Pant, a reception pad Prx, and a ground pad Pgnd. Bumps 26 are provided on the pads.

  The acoustic wave resonator 20b and the wiring 22b are provided on the region 32 of the piezoelectric substrate 10a. The acoustic wave resonator 20b includes series resonators S1 to S4 and parallel resonators P1 to P3. The wiring 22b is connected to the acoustic wave resonator 20b. The wiring 22b includes a common pad Pant, a transmission pad Ptx, and a ground pad Pgnd. Bumps 26 are provided on the pads. The common pad Pant, the transmission pad Ptx, the reception pad Prx, and the ground pad Pgnd are electrically connected to the common terminal Ant, the transmission terminal Tx, the reception terminal Rx, and the ground terminal via the bump 26.

  The pass bands of the transmission filter 50 and the reception filter 52 do not overlap, and the pass band of the transmission filter 50 is lower than the pass band of the reception filter 52. The thickness T1 of the piezoelectric substrate 10a in the region 30 is smaller than the thickness T2 of the piezoelectric substrate 10a in the region 32. Therefore, even if the acoustic wave resonators 20a and 20b have substantially the same film thickness of the electrode finger 14 and the insulating film 24, the resonance frequency of the elastic wave resonator 20a is changed to the elastic wave resonator. It can be greater than the resonance frequency of 20b. Since the difference in resonance frequency between the acoustic wave resonators 20b (and 20a) in the transmission filter 50 (and the reception filter 52) is small, it can be dealt with by making the pitch L2 (or L1) of the electrode fingers 14 different. Therefore, it is possible to form the acoustic wave resonators 20a and 20b having greatly different resonance frequencies on the single substrate 10 with a simple manufacturing process. Therefore, the transmission filter 50 and the reception filter 52 that do not overlap in the pass band can be formed on the single substrate 10.

  As shown in FIG. 5A, when the pass band of the transmission filter 50 is lower than the pass band of the reception filter 52, the transmission filter 50 and the reception filter 52 are formed in the regions 32 and 30, respectively. As shown in FIG. 5B, when the pass band of the transmission filter 50 is higher than the pass band of the reception filter 52, the transmission filter 50 and the reception filter 52 are formed in the regions 30 and 32, respectively. 5A and 5B, the thickness of the support substrate 10b is, for example, 50 μm to 500 μm, and at least one of the thicknesses T1 and T2 is equal to or less than the pitches L1 and L2.

[Production Method of Example 1]
FIG. 8A to FIG. 9D are cross-sectional views illustrating the method for manufacturing the acoustic wave device according to the first embodiment. As shown in FIG. 8A, the lower surface of the piezoelectric substrate 10a is directly bonded to the upper surface of the support substrate 10b at room temperature. The joining method is the same as that of Patent Document 1, for example. That is, the upper surface of the support substrate 10b and the lower surface of the piezoelectric substrate 10a are activated by an inert element ion beam, neutral beam, or plasma. Thereafter, the support substrate 10b and the piezoelectric substrate 10a are bonded at room temperature. At this time, an amorphous layer 10d having a thickness of 1 nm to 8 nm, for example, is formed between the support substrate 10b and the piezoelectric substrate 10a. As described above, when the support substrate 10b and the piezoelectric substrate 10a are bonded at room temperature, an amorphous layer 10d is formed. Since the amorphous layer 10d is much thinner than the piezoelectric substrate 10a, the support substrate 10b and the piezoelectric substrate 10a are directly bonded. Since the amorphous layer 10d is very thin, the illustration is omitted in the drawings other than FIGS. 8A and 13B.

  As shown in FIG. 8B, the upper surface of the piezoelectric substrate 10a is planarized by polishing, for example, using a CMP (Chemical Mechanical Polishing) method. As shown in FIG. 8C, the piezoelectric substrate 10a in the region 30 is thinned. For example, the upper surface of the piezoelectric substrate 10a is irradiated with a laser beam 54 and ablated. Thereby, the piezoelectric substrate 10a in the region 30 is thinned. As shown in FIG. 8D, the metal film 12 is formed on the regions 30 and 32 of the piezoelectric substrate 10a by using, for example, a vacuum evaporation method or a sputtering method. As shown in FIG. 8E, the metal film 12 is patterned into a desired shape using, for example, a photolithography method and an etching method. As a result, the acoustic wave resonator 20a and the wiring 22a are formed on the region 30 of the piezoelectric substrate 10a, and the acoustic wave resonator 20b and the wiring 22b are formed on the region 32.

  As shown in FIG. 9A, the insulating film 24 is formed by using, for example, a vacuum deposition method, a sputtering method, or a CVD (Chemical Vapor Deposition) method so as to cover the acoustic wave resonators 20a and 20b. As shown in FIG. 9B, the insulating film 24 is patterned into a desired shape using, for example, a photolithography method and an etching method. As a result, the insulating film 24 on the electrode fingers 14 of the acoustic wave resonators 20a and 20b remains, and the insulating film 24 on the wirings 22a and 22b is removed. As shown in FIG. 9C, a metal film 27 is formed on the wirings 22a and 22b and the insulating film 24 by using, for example, a vacuum evaporation method, a sputtering method, or a plating method. The metal film 27 is, for example, a gold film. As shown in FIG. 9D, the metal film 27 is patterned into a desired shape using, for example, a photolithography method and an etching method. As a result, a low resistance metal film 28 is formed on the wirings 22a and 22b, and the metal film 27 on the acoustic wave resonators 20a and 20b is removed.

  As shown in FIGS. 8A to 9D, the manufacturing steps other than thinning the piezoelectric substrate 10a in the region 30 in FIG. 8C can be made common to the acoustic wave resonators 20a and 20b. Therefore, the acoustic wave resonators 20a and 20b having different resonance frequencies can be easily manufactured.

  FIG. 10A and FIG. 10B are cross-sectional views of the acoustic wave device according to the second embodiment. As shown in FIGS. 10A and 10B, the intermediate layer 10c is sandwiched between the support substrate 10b and the piezoelectric substrate 10a. The temperature coefficient of the elastic modulus of the intermediate layer 10c is opposite to the temperature coefficient of the elastic modulus of the piezoelectric substrate 10a. Thereby, the frequency temperature coefficient (TCF) of the acoustic wave resonators 20a and 20b can be further suppressed. As the intermediate layer 10c, for example, a silicon oxide film, a silicon film, an aluminum nitride film, or a silicon nitride film can be used. The thickness of the intermediate layer 10c is, for example, the pitches L1 and L2 or less. Other configurations are the same as those of the first embodiment, and the description thereof is omitted.

[Modification 1 of Embodiment 2]
FIG. 11A and FIG. 11B are cross-sectional views of the acoustic wave device according to the first modification of the second embodiment. As shown in FIGS. 11A and 11B, the thickness T3 of the intermediate layer 10c in the region 30 is larger than the thickness T4 of the intermediate layer 10c in the region 32. Thickness T1 + T3 is approximately equal to thickness T2 + T4. Thereby, the upper surface of the boundary between the regions 30 and 32 of the piezoelectric substrate 10a is substantially flat.

[Production Method of Modification 1 of Embodiment 2]
FIG. 12A to FIG. 14B are cross-sectional views illustrating a method for manufacturing an acoustic wave device according to the first modification of the second embodiment. A piezoelectric substrate 10a is prepared as shown in FIG. As shown in FIG. 12B, the piezoelectric substrate 10a in the region 30 is thinned. For example, the surface of the piezoelectric substrate 10a in the region 30 is irradiated with laser light 54 and ablated. Thereby, the regions 30 and 32 are formed in the piezoelectric substrate 10a. As shown in FIG. 12C, the intermediate layer 10c is formed on the surface of the piezoelectric substrate 10a having a step by using, for example, a vacuum deposition method, a sputtering method, or a CVD method. As shown in FIG. 12D, the surface of the intermediate layer 10c is planarized using, for example, a CMP method.

  As shown in FIG. 13A, the upper and lower sides are shown upside down. As shown in FIG. 13B, the upper surface of the support substrate 10b and the surface of the flattened intermediate layer 10c are directly bonded at room temperature. At this time, similarly to FIG. 8A, an amorphous layer 10d is formed between the support substrate 10b and the intermediate layer 10c. When the intermediate layer 10c is a silicon oxide film, room temperature bonding between the silicon oxide film and the support substrate 10b may be difficult. When the support substrate 10b and the intermediate layer 10c are bonded at room temperature, the intermediate layer 10c is preferably an insulating film other than a silicon oxide film such as a silicon film, an aluminum nitride film, or a silicon nitride film. As shown in FIG. 13C, the upper surface of the piezoelectric substrate 10a is planarized using, for example, a CMP method. Thereby, the substrate 10 which is a composite substrate having the intermediate layer 10c between the support substrate 10b and the piezoelectric substrate 10a is formed.

  As shown in FIG. 14A, as in FIGS. 8D and 8E, the acoustic wave resonator 20a and the wiring 22a are formed on the region 30 of the piezoelectric substrate 10a and elastic on the region 32. A wave resonator 20b and a wiring 22b are formed. As shown in FIG. 14B, the insulating film 24 and the metal film 28 are formed in the same manner as in FIGS. 9A to 9D.

  In the first modification of the second embodiment, the upper surfaces of the regions 30 and 32 of the piezoelectric substrate 10a are flat. This facilitates formation of the acoustic wave resonators 20a and 20b, the wirings 22a and 22b, etc. on the piezoelectric substrate 10a. Further, when the piezoelectric substrate 10a is mounted using bumps, the bump height is uniform and the bump connectivity is stabilized.

  According to the first and second embodiments and the modifications thereof, the piezoelectric substrate 10a includes a region 30 (first region) having a thickness T1 (first thickness) and a thickness T2 (second larger than the first thickness). ) Having a region 32 (second region). The acoustic wave resonator 20a (first acoustic wave resonator) provided on the region 30 includes a pair of comb electrodes 16 (first comb electrodes) each having a plurality of electrode fingers 14 (first electrode fingers). The average pitch L1 of one electrode finger 14 of the comb-shaped electrode 16 is larger than the thickness T1. An elastic wave resonator 20b (second elastic wave resonator) provided on the region 32 and a pair of comb electrodes 16 (second comb electrodes) each having a plurality of electrode fingers 14 (second electrode fingers) are provided. .

  Thereby, as shown in FIGS. 4A and 4B, the resonance frequency of the elastic wave resonator 20a can be made higher than the resonance frequency of the elastic wave resonator 20b. Therefore, the acoustic wave resonators 20a and 20b having different resonance frequencies can be easily formed. Further, spurious and loss in the acoustic wave resonator 20a can be suppressed.

  By making the average pitch L2 of one electrode finger 14 of the comb electrode 16 of the acoustic wave resonator 20b larger than the thickness T2, spurious and loss in the acoustic wave resonator 20b can be suppressed. By making the average pitch L2 smaller than the thickness T2, the difference in resonance frequency between the acoustic wave resonators 20a and 20b can be increased.

  As in Example 1 and its modifications, the piezoelectric substrate 10a may be bonded to the support substrate 10b via the amorphous layer 10d. As in Example 2 and its modifications, an intermediate layer 10c sandwiched between the piezoelectric substrate 10a and the support substrate 10b may be provided. The temperature coefficient of the elastic modulus of the intermediate layer 10c is opposite to the temperature coefficient of the elastic modulus of the piezoelectric substrate 10a. Thereby, the frequency temperature coefficient of the acoustic wave resonators 20a and 20b can be suppressed.

  As in the first modification of the second embodiment, the thickness T3 (third thickness) of the intermediate layer 10c between the region 30 of the piezoelectric substrate 10a and the support substrate 10b is equal to the region 32 of the piezoelectric substrate 10a and the support substrate 10b. The thickness of the intermediate layer 10c between the two is larger than the thickness T4 (fourth thickness). Thus, the step between the regions 30 and 32 on the upper surface of the piezoelectric substrate 10a (the surface opposite to the intermediate layer 10c) is made smaller than the difference between the thicknesses T1 and T2. Thereby, formation of the acoustic wave resonators 20a and 20b on the piezoelectric substrate 10a is facilitated. The upper surfaces of the piezoelectric substrates 10a in the regions 30 and 32 are preferably substantially flat to the extent of manufacturing error.

  The elastic wave excited by the comb electrodes 16 of the elastic wave resonators 20a and 20b is preferably an SH wave. When the electrode finger 14 excites SH waves, bulk waves are likely to be excited. Therefore, when the thickness T1 of the piezoelectric substrate 10a is made smaller than the pitch L1, the resonance frequency of the acoustic wave resonator 20a becomes higher.

  Since the comb-shaped electrode 16 excites SH waves, the piezoelectric substrate 10a is preferably a Y-cut X-propagating lithium tantalate substrate having a cut angle of 20 ° to 48 °. The cut angle is preferably 30 ° or more, and more preferably 38 ° or more. The cut angle is preferably 46 ° or less, and more preferably 44 ° or less.

  6 and 7, in the multiplexer, the reception filter 52 (first filter) includes one or more elastic wave resonators 20a, and the transmission filter 50 (second filter) includes one or more elastic waves. A resonator 20b is included. When the pass band of the transmission filter 50 and the pass band of the reception filter 52 do not overlap, the resonance frequencies of the acoustic wave resonators 20a and 20b are greatly different. For this reason, the resonance frequency is varied by varying the thicknesses T1 and T2 of the piezoelectric substrate 10a. Thereby, it is possible to easily form the transmission filter 50 and the reception filter 52 whose pass bands do not overlap with each other on the same piezoelectric substrate 10a.

  Although an example of a duplexer has been described as a multiplexer, a triplexer or a quadplexer may be used. By providing three or more regions having different thicknesses on the piezoelectric substrate 10a, three or more filters having different pass bands can be formed on the piezoelectric substrate 10a.

  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 Substrate 10a Piezoelectric substrate 10b Support substrate 10c Intermediate layer 12 Metal film 14 Electrode finger 16 Comb-shaped electrode 20, 20a, 20b Elastic wave resonator 30, 32 Region 50 Transmission filter 52 Reception filter

Claims (11)

A support substrate;
A piezoelectric substrate bonded onto the support substrate and having a first region having a first thickness and a second region having a second thickness greater than the first thickness;
An average pitch of one first electrode finger of the pair of first comb electrodes is provided on the first region of the piezoelectric substrate, and includes a pair of first comb electrodes each having a plurality of first electrode fingers. Is a first acoustic wave resonator larger than the first thickness;
A second acoustic wave resonator provided on the second region of the piezoelectric substrate and including a pair of second comb electrodes each having a plurality of second electrode fingers;
An elastic wave device comprising:   2. The acoustic wave device according to claim 1, wherein an average pitch of one second electrode finger of the pair of second comb electrodes is larger than the second thickness.   2. The acoustic wave device according to claim 1, wherein an average pitch of one second electrode finger of the pair of second comb electrodes is smaller than the second thickness.   The acoustic wave device according to any one of claims 1 to 3, wherein the piezoelectric substrate is bonded to the support substrate via an amorphous layer.   The acoustic wave device according to claim 1, further comprising an intermediate layer sandwiched between the piezoelectric substrate and the support substrate.   The third thickness of the intermediate layer between the first region of the piezoelectric substrate and the support substrate is the fourth thickness of the intermediate layer between the second region of the piezoelectric substrate and the support substrate. The acoustic wave device according to claim 5, wherein the acoustic wave device is larger than the thickness.   The acoustic wave device according to claim 6, wherein surfaces of the piezoelectric substrate opposite to the intermediate layer in the first region and the second region are substantially flat.   The acoustic wave device according to any one of claims 1 to 7, wherein the pair of first comb electrodes and the pair of second comb electrodes excite SH waves.   The acoustic wave device according to any one of claims 1 to 8, wherein the piezoelectric substrate is a Y-cut X-propagating lithium tantalate substrate having a cut angle of 20 ° or more and 48 ° or less. Including the acoustic wave device according to any one of claims 1 to 9,
A first filter including one or more first acoustic wave resonators;
A second filter having a passband that does not overlap with a passband of the first filter and including one or more second acoustic wave resonators;
A multiplexer comprising: A support substrate;
A piezoelectric substrate bonded to the support substrate via an amorphous layer and having a first region having a first thickness and a second region having a second thickness greater than the first thickness;
A third thickness between the first region of the piezoelectric substrate and the support substrate is sandwiched between the support substrate and the piezoelectric substrate, and a third thickness between the second region of the piezoelectric substrate and the support substrate is An intermediate layer greater than a fourth thickness;
A composite substrate comprising:

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