JP6886264B2 - Elastic wave devices and composite substrates and their manufacturing methods - Google Patents

Description

The present invention relates to an elastic wave device and a composite substrate and a method for manufacturing the same, and the present invention relates to an elastic wave device and a composite substrate having a piezoelectric substrate having a stoichiometric composition and a method for manufacturing the same.

In elastic wave devices, IDTs (Interdigital Transducers) that excite elastic waves are formed on a piezoelectric substrate. As the piezoelectric substrate, for example, a lithium tantalate (LiTaO ₃ ) substrate or a lithium niobate (LiNbO ₃ ) substrate is used. When the composition of Li in lithium tantalate and lithium niobate is a stoichiometric composition, it is called a stoichiometric composition. When the composition of lithium is slightly smaller than the stoichiometric composition, it is called the congluent composition.

It is known to use a piezoelectric substrate having a stoichiometric composition for a surface acoustic wave device (for example, Patent Document 1). It is known to use a substrate in which a lithium tantalate substrate is bonded to a sapphire substrate for a surface acoustic wave device (for example, Patent Document 2). It is known that ions are implanted into a piezoelectric substrate, the piezoelectric substrate and the support substrate are joined, and then the piezoelectric substrate is peeled off from the implantation region (for example, Patent Document 3). It is known that lithium is diffused on the surface of a substrate having a congluent composition to form a region having a stoichiometric composition on the surface of the substrate (for example, Patent Document 4). It is known that a series resonator of one filter of a duplexer having two ladder type filters and a parallel resonator of the other filter are provided on the same substrate (for example, Patent Document 5).

Japanese Unexamined Patent Publication No. 2015-23474 Japanese Unexamined Patent Publication No. 2004-186868 International Publication No. 2009/081651 Japanese Unexamined Patent Publication No. 2013-66032. Japanese Unexamined Patent Publication No. 2013-10655

By joining the piezoelectric substrate on a support substrate such as a sapphire substrate or a silicon substrate as in Patent Documents 2 and 3, the temperature dependence of the frequency of the elastic wave device can be reduced. However, the temperature-dependent suppression of frequency is not sufficient.

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

In the present invention, the support substrate is joined to the support substrate, and the linear thermal expansion coefficient in the propagation direction of the elastic wave is larger than the linear thermal expansion coefficient of the support substrate in the propagation direction, and the thickness is larger than 1 μm. A piezoelectric substrate made of lithium tantalate or lithium niobate, which has a metric composition, and an IDT provided on the upper surface of the piezoelectric substrate are provided, and the lithium composition ratio of the lower surface of the piezoelectric substrate is the upper surface of the piezoelectric substrate. It is an elastic wave device with a larger lithium composition ratio.

In the above configuration, an amorphous layer may be provided between the support substrate and the piezoelectric substrate.

The present invention is connected to a first series resonator connected in series between the common terminal and the first terminal, and a parallel arm between the node and the ground between the common terminal and the first terminal. A first ladder type filter having a first parallel resonator, a second series resonator connected in series between the common terminal and the second terminal, and the common terminal and the second terminal. It comprises a second parallel resonator connected to a parallel arm between a node in between and a ground, and a second ladder type filter having a higher passage band than the first ladder type filter. The 1-series resonator and the second parallel resonator are a silicon substrate, a lithium tantalate substrate bonded onto the silicon substrate and having a stoichiometric composition having a thickness of more than 1 μm, and the stoichiometric composition. The IDT provided on the upper surface of the lithium tantalate substrate is provided, and the first parallel resonator and the second series resonator include a lithium tantalate substrate having a congluent composition and a lithium tantalate composition. An elastic wave device including an IDT provided on the upper surface of a substrate.

In the above configuration, the support substrate may be a silicon substrate, and the piezoelectric substrate may be a rotating Y-cut X-propagated lithium tantalate substrate.

In the above configuration, the first series resonator connected in series between the common terminal and the first terminal is connected to the parallel arm between the node and the ground between the common terminal and the first terminal. A first ladder type filter having a first parallel resonator, a second series resonator connected in series between the common terminal and the second terminal, and the common terminal and the second terminal. It comprises a second parallel resonator connected to a parallel arm between a node in between and a ground, and a second ladder type filter having a higher passage band than the first ladder type filter. The 1-series resonator and the second parallel resonator may be configured to include the IDT.

In the above configuration, the first parallel resonator and the second series resonator may be a resonator containing an IDT formed on a piezoelectric substrate having a congluent composition, or a piezoelectric thin film resonator.

The present invention is a rotating Y-cut X propagation substrate joined to the support substrate and the support substrate, and the linear thermal expansion coefficient in the X-axis direction is larger than the linear thermal expansion coefficient of the support substrate in the X-axis direction. A piezoelectric substrate composed of lithium tantalate or lithium niobate having a stoichiometric composition having a thickness of more than 1 μm is provided, and the lithium composition ratio of the lower surface of the piezoelectric substrate is larger than the lithium composition ratio of the upper surface of the piezoelectric substrate. The lower surface of the piezoelectric substrate is a composite substrate that is a surface on the support substrate side.

In the present invention, by introducing lithium on both sides of a piezoelectric substrate made of lithium tantalate or lithium niobate having a congluent composition, the first region and the second region of the stoichiometric composition, the first region and the second region are introduced. A step of forming a third region of the congluent composition provided between the two, a step of joining the first region side of the piezoelectric substrate to the support substrate, and the support substrate so that the first region is exposed. This is a method for manufacturing a composite substrate, which comprises a step of removing the second region and the third region of the piezoelectric substrate bonded to the above.

In the above configuration, the steps of removing the second region and the third region include a step of removing the second region by a method other than the CMP method so that the third region is exposed, and a step of removing the first region. The removal rate of the first region and the second region by a method other than the CMP method includes a step of removing the third region by the CMP method so as to be exposed, and the removal speed of the first region by the CMP method is determined. And it can be configured to be higher than the removal rate of the second region.

According to the present invention, the temperature dependence of frequency can be suppressed.

1 (a) is a plan view of the elastic wave resonator according to the first embodiment, and FIG. 1 (b) is a cross-sectional view taken along the line AA of FIG. 1 (a). 2 (a) to 2 (e) are cross-sectional views showing a method of manufacturing an elastic wave device according to the first embodiment. FIG. 3A is a diagram showing the temperature dependence of the resonance frequency and the antiresonance frequency in Example 1 and Comparative Example 1, and FIG. 3B is a diagram showing the frequency temperature coefficient of the resonance frequency and the antiresonance frequency. is there. FIG. 4A is a diagram showing the temperature dependence of the resonance frequency and the antiresonance frequency in Comparative Examples 2 and 3, and FIG. 4B is a diagram showing the frequency temperature coefficient of the resonance frequency and the antiresonance frequency. FIG. 5 is a circuit diagram of the duplexer according to the second embodiment. FIG. 6 is a schematic plan view of the duplexer according to the second embodiment.

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

An elastic wave resonator will be described as an elastic wave device. 1 (a) is a plan view of the elastic wave resonator according to the first embodiment, and FIG. 1 (b) is a cross-sectional view taken along the line AA of FIG. 1 (a). As shown in FIGS. 1A and 1B, the piezoelectric substrate 10 is bonded onto the support substrate 12. An amorphous layer 14 is provided between the support substrate 12 and the piezoelectric substrate 10. The IDT 21 and the reflector 22 are formed on the piezoelectric substrate 10. The IDT 21 and the reflector 22 are formed by a metal film 15 formed on the piezoelectric substrate 10. The IDT 21 includes a pair of opposing comb-shaped electrodes 20. The comb-shaped electrode 20 includes a plurality of electrode fingers 16 and a bus bar 18 to which the plurality of electrode fingers 16 are connected. The pair of comb-shaped electrodes 20 are provided so as to face each other so that the electrode fingers 16 are substantially staggered. The elastic wave excited by the IDT 21 propagates mainly in the arrangement direction of the electrode fingers 16. The pitch of the electrode fingers 16 is approximately the wavelength λ of the elastic wave. In the rotating Y-cut X propagation substrate, the propagation direction of elastic waves is the X-axis direction of the crystal orientation. A protective film 24 is provided so as to cover the metal film 15.

The piezoelectric substrate 10 is a lithium tantalate substrate or a lithium niobate substrate having a stoichiometric composition. In the stoichiometric composition, the composition ratio of lithium to lithium and tantalum (or niobium) (hereinafter referred to as lithium composition ratio) is 49.5% or more and 50.5% or less. The support substrate 12 is, for example, a sapphire substrate, a silicon substrate, a spinel substrate, or an alumina substrate. The metal film 15 is, for example, an aluminum film, a copper film, a titanium film, a chromium film, a tungsten film or a molybdenum film, or a composite film thereof. The film thickness of the metal film 15 is, for example, 100 nm to 800 nm. The protective film 24 is, for example, a silicon oxide film or a silicon nitride film. The film thickness of the protective film 24 is smaller than that of the metal film 15. Instead of the protective film 24, a temperature compensation film thicker than the metal film 15 may be provided.

2 (a) to 2 (e) are cross-sectional views showing a method of manufacturing an elastic wave device according to the first embodiment. As shown in FIG. 2A, a piezoelectric substrate 10 having a congluent composition is prepared. Lithium tantalate substrates and lithium niobate substrates with a stoichiometric composition are expensive and scarcely available. Therefore, a substrate having a congluent composition is prepared. In the congluent composition, the lithium composition ratio is 49.5% or less. The lithium composition ratio is, for example, 48% or more. The thickness of the piezoelectric substrate 10 is, for example, 200 μm to 600 μm.

In the congluent composition, the lithium sites are vacant. Therefore, the curie temperature of the congluent composition is different from that of the stoichiometric composition. On the lithium tantalate substrate, the Curie temperature of the stoichiometric composition is 660 ° C to 700 ° C. The Curie temperature of the congluent composition is 590 ° C to 650 ° C. On the lithium niobate substrate, the Curie temperature of the stoichiometric composition is 1180 ° C to 1200 ° C. The Curie temperature of the congluent composition is 1100 ° C to 1180 ° C. The Curie temperature can be measured by differential thermal analysis or differential scanning calorimetry.

As shown in FIG. 2 (b), the first region 10a and the second region 10c of the strikiometric composition are formed by diffusing lithium on the upper surface and the lower surface of the piezoelectric substrate 10. As a method for diffusing lithium, for example, the method of Patent Document 4 is used. The region between the first region 10a and the second region 10c is the third region 10b of the congluent composition. A granular region in which the lithium composition gradually changes is formed between the first region 10a, the second region 10c, and the third region 10b. The thickness of the first region 10a and the second region 10c is, for example, 10 μm to 50 μm, respectively.

As shown in FIG. 2C, the first region 10a of the piezoelectric substrate 10 is bonded to the support substrate 12 at room temperature. A method of room temperature bonding between the support substrate 12 and the piezoelectric substrate 10 will be described. First, the upper surface of the support substrate 12 and the lower surface of the piezoelectric substrate 10 are irradiated with an ion beam, a neutral beam, or plasma of an inert gas. As a result, an amorphous layer of several nm or less is formed on the upper surface of the support substrate 12 and the lower surface of the piezoelectric substrate 10. Unbonded bonds are generated on the surface of the amorphous layer. Due to the presence of unbonded bonds, the upper surface of the support substrate 12 and the lower surface of the piezoelectric substrate 10 are in an activated state. The unbonded hands of the upper surface of the support substrate 12 and the lower surface of the piezoelectric substrate 10 are bonded to each other. As a result, the support substrate 12 and the piezoelectric substrate 10 are joined at room temperature. The amorphous layer 14 is integrally arranged between the bonded support substrate 12 and the piezoelectric substrate 10. The amorphous layer 14 has a thickness of, for example, 1 nm to 8 nm. Here, the normal temperature is 100 ° C. or lower and −20 ° C. or higher, preferably 80 ° C. or lower and 0 ° C. or higher. The support substrate 12 and the piezoelectric substrate 10 may be joined with, for example, an adhesive.

As shown in FIG. 2D, the second region 10c is removed so that at least a part of the third region 10b of the piezoelectric substrate 10 remains. For removing the second region 10c, for example, a grinding method, a sandblasting method, an ion milling method, or the like is used.

As shown in FIG. 2 (e), the third region 10b is removed. A CMP (Chemical Mechanical Polishing) method is used to remove the third region 10b. At this time, the upper part of the first region 10a may be removed. Regions of stoichiometric composition are more difficult to remove than regions of congluent composition. For example, it is known from the findings of the inventors that when the CMP method is used, the polishing rate of the lithium tantalate substrate having a congluent composition is about three times that of the stoichiometry composition. Therefore, as shown in FIG. 2D, the second region 10c is removed by a method having a high removal speed (for example, a method other than CMP). Then, as shown in FIG. 2E, the third region 10b is removed by a method having a slow removal rate (for example, the CMP method). As a result, the first region 10a functions as a stopper for removing the third region 10b. Therefore, the thickness of the first region 10a can be set accurately. As a result, a composite substrate in which the lower surface of the piezoelectric substrate 10 is bonded to the upper surface of the support substrate 12 is produced.

Then, as shown in FIGS. 1A and 1B, the IDT 21 and the reflector 22 are formed on the first region 10a of the piezoelectric substrate 10.

An elastic wave resonator according to Example 1 was produced. The production conditions of Example 1 are as follows.
Material of piezoelectric substrate 10: 42 ° Y-cut X propagation lithium tantalate substrate with stoichiometric composition Thickness of piezoelectric substrate 10: 20 μm
Material of support substrate 12: Silicon Thickness of support substrate 12: 550 μm
Substrate bonding method: Room temperature bonding with an amorphous layer Method for removing the piezoelectric substrate 10: FIG. 2 (d) is a grinding method, and FIG. 2 (e) is a CMP method.
Pitch of electrode fingers 16: 4 μm
Aperture length: 120 μm
Logarithm of electrode finger 16: 100 Duty ratio of electrode finger: 50%
Material of protective film 24: Silicon oxide film Film thickness of protective film 24: 15 nm
Resonance frequency fr: 976 MHz
Antiresonance frequency fa: 1020MHz

For comparison, Comparative Example 1 in which a piezoelectric substrate having a congluent composition was bonded onto the support substrate 12 was produced.
The production conditions of Comparative Example 1 are as follows.
Material of piezoelectric substrate 10: 42 ° Y-cut X propagation of congluent composition Material of lithium tantalate substrate Support substrate 12: Sapphire resonance frequency fr: 965 MHz
Antiresonance frequency fa: 1001MHz
Other conditions are the same as in Example 1.

Further, Comparative Examples 2 and 3 in which the piezoelectric substrate 10 was not bonded to the support substrate 12 were produced. Comparative Examples 2 and 3 are piezoelectric substrates having a stoichiometric composition and a congluent composition, respectively.
The production conditions of Comparative Example 2 are as follows.
Material of piezoelectric substrate 10: 42 ° Y-cut X-propagated lithium tantalate substrate with a region of stoichiometric composition provided on the region of congluent composition Thickness of piezoelectric substrate 10: region of congluent composition: 330 μm, of stoichiometric composition Region: 20 μm

The production conditions of Comparative Example 3 are as follows.
Material of piezoelectric substrate 10: 42 ° Y-cut X propagation lithium tantalate substrate in the region of congluent composition Thickness of piezoelectric substrate 10: 150 μm

For Example 1 and Comparative Examples 1 to 3, the resonance frequency fr and the anti-resonance frequency fa were measured at 25 ° C., 50 ° C. and 85 ° C. The amount of change of the resonance frequency fr (or antiresonance frequency fa) at 50 ° C. and 85 ° C. from the resonance frequency fr (or antiresonance frequency fa) at 25 ° C. is defined as the amount of change ΔF of the resonance frequency fr (or antiresonance frequency fa). did. The frequency temperature coefficient TCF was calculated from the slope of the amount of change ΔF with respect to temperature.

FIG. 3A is a diagram showing the temperature dependence of the resonance frequency and the antiresonance frequency in Example 1 and Comparative Example 1, and FIG. 3B is a diagram showing the frequency temperature coefficient of the resonance frequency and the antiresonance frequency. is there. FIG. 4A is a diagram showing the temperature dependence of the resonance frequency and the antiresonance frequency in Comparative Examples 2 and 3, and FIG. 4B is a diagram showing the frequency temperature coefficient of the resonance frequency and the antiresonance frequency.

As shown in FIGS. 3 (a) and 3 (b), the absolute value of the amount of change ΔF and the absolute value of TCF in Example 1 are smaller than those in Comparative Example 1. In particular, the absolute values of ΔF and TCF of the resonance frequency fr are small. As shown in FIGS. 4A and 4B, Comparative Example 2 and Comparative Example 3 have larger absolute values of ΔF and TCF than those of Example 1 and Comparative Example 1.

When the piezoelectric substrate 10 having a congluent composition is used, the absolute values of ΔF and TCF are smaller in Comparative Example 1 than in Comparative Example 3 for the following reasons. When an elastic wave device is formed using a piezoelectric substrate 10 such as a lithium tantalate substrate as in Comparative Example 3, the piezoelectric substrate 10 expands and contracts depending on temperature. As a result, the frequency temperature dependence such as the resonance frequency of the elastic wave device becomes large. Therefore, as in Comparative Example 1, the piezoelectric substrate is mounted on the support substrate 12 whose linear thermal expansion coefficient is smaller than the linear thermal expansion coefficient of the elastic wave propagation direction of the piezoelectric substrate 10 (in the X-axis direction in the rotational Y-cut X propagation substrate). 10 are joined. For example, the linear thermal expansion coefficient of the rotating Y-cut X-propagated lithium tantalate substrate in the X-axis direction is 16.1 ppm / ° C., and the linear thermal expansion coefficients of the sapphire substrate and the silicon substrate are 7.7 ppm / ° C. and 3.9 ppm / ° C., respectively. Is. As a result, the support substrate 12 suppresses the expansion and contraction of the piezoelectric substrate 10. Therefore, in Comparative Example 1, the frequency temperature dependence of the elastic wave device can be suppressed as compared with Comparative Example 3. However, since the linear thermal expansion coefficients of the piezoelectric substrate 10 and the support substrate 12 have the same sign, the frequency temperature coefficient does not become zero.

From the comparison between Comparative Examples 2 and 3, when the support substrate 12 is not bonded, the TCF is about the same between the case where the piezoelectric substrate 10 has a stoichiometric composition and the case where the piezoelectric substrate 10 has a congruent composition. On the other hand, when the piezoelectric substrate 10 bonded to the support substrate 12 is used as a stoichiometric composition from the comparison between Example 1 and Comparative Example 1, the absolute value of TCF is smaller than that of the congluent composition. In particular, the absolute value of TCF of the resonance frequency fr becomes small. Although the material of the support substrate 12 is different between Example 1 and Comparative Example 1, in the piezoelectric substrate having a congluent composition, the TCF is about the same when the support substrate 12 is a sapphire substrate and when it is a silicon substrate. Therefore, the reason why the TCF of the resonance frequency fr became almost 0 in Example 1 is due to the synergistic effect of the piezoelectric substrate 10 having a stoichiometric composition and the piezoelectric substrate 10 being bonded to the support substrate 12. is there.

According to the first embodiment, the piezoelectric substrate 10 bonded on the support substrate 12 has a coefficient of linear thermal expansion in the propagation direction of elastic waves larger than the coefficient of linear thermal expansion of the support substrate 12 in the propagation direction, and has a stoichiometric composition. Consists of certain lithium tantalate or lithium niobate. Thereby, the frequency temperature dependence can be suppressed. In order to suppress spurious, the thickness of the piezoelectric substrate 10 is preferably larger than 1 μm, more preferably 10 μm or more. The thickness of the piezoelectric substrate 10 is preferably the wavelength λ or more of the elastic wave, and more preferably 3λ or more. In order to reduce the absolute value of TCF, the thickness of the piezoelectric substrate 10 is preferably 50 μm or less.

When the support substrate 12 and the piezoelectric substrate 10 are joined as shown in FIG. 2C, an amorphous layer 14 is formed between the support substrate 12 and the piezoelectric substrate 10. When the support substrate 12 and the piezoelectric substrate 10 are joined with an adhesive, an adhesive layer is formed between the support substrate 12 and the piezoelectric substrate 10.

The support substrate 12 has a smaller linear thermal expansion coefficient than the piezoelectric substrate 10, and the piezoelectric substrate 10 may be a lithium tantalate substrate or a lithium niobate substrate, but the support substrate 12 is a silicon substrate and the piezoelectric substrate 10 is a rotary Y-cut. It is preferably an X-propagated lithium tantalate substrate. Thereby, the frequency temperature dependence can be further suppressed.

When joining the piezoelectric substrate 10 to the support substrate 12, it is difficult to join the thin piezoelectric substrate 10 to the support substrate 12. Therefore, the thick piezoelectric substrate 10 is joined to the support substrate 12 and the piezoelectric substrate 10 is polished. The piezoelectric substrate 10 having a stoichiometric composition is difficult to process, for example, the speed of grinding and polishing is slow. Therefore, as shown in FIG. 2B, by introducing lithium on both sides of the piezoelectric substrate 10 having a congluent composition, the first region 10a and the second region 10c of the stoichiometric composition and the third region 10b of the congluent composition can be formed. Form. As shown in FIG. 2C, the first region 10a side of the piezoelectric substrate 10 is joined to the support substrate 12. As shown in FIGS. 2D and 2E, the second region 10c and the third region 10b of the piezoelectric substrate 10 bonded to the support substrate 12 are removed so that the first region 10a is exposed. As a result, most of the piezoelectric substrate 10 to be removed becomes a region of congluent composition. Therefore, the piezoelectric substrate 10 having a stoichiometric composition bonded onto the support substrate 12 can be easily manufactured.

As shown in FIG. 2D, the second region 10c is removed by a method other than CMP so that the third region 10b is exposed. As shown in FIG. 2E, the third region 10b is removed by the CMP method so that the first region 10a is exposed. The removal rate of the first region 10a and the second region 10c by a method other than the CMP method is higher than the removal rate of the first region 10a and the second region 10c by the CMP method. As a result, the first region 10a functions as a stopper for removing the third region 10b. Therefore, the thickness of the first region 10a can be set accurately.

When the third region 10b is removed by using the first region 10a as a stopper, the polishing of the piezoelectric substrate 10 is stopped in the region where the lithium composition ratio is gradually changing. In this case, the lithium composition ratio of the lower surface of the piezoelectric substrate 10 (the surface to be joined to the support substrate 12) is larger than the lithium composition ratio of the upper surface of the piezoelectric substrate 10. When the piezoelectric substrate 10 having a stoichiometric composition is formed by a method other than the method of FIG. 2B, the lithium composition ratio of the lower surface of the piezoelectric substrate 10 may be smaller than or the same as the lithium composition ratio of the upper surface of the piezoelectric substrate 10. Good.

The second embodiment is an example of a duplexer using the elastic wave resonator according to the first embodiment. FIG. 5 is a circuit diagram of the duplexer according to the second embodiment. As shown in FIG. 5, a transmission filter 40 (first ladder type filter) is electrically connected between the common terminal Ant and the transmission terminal Tx (first terminal). The reception filter 42 (second ladder type filter) between the common terminal Ant and the reception terminal Rx (second terminal) is electrically connected. The inductor L1 is electrically connected between the common terminal Ant and the ground. The pass band of the reception filter 42 is higher than the communication band of the transmission filter 40. The transmission filter 40 outputs a signal in the transmission band among the high frequency signals input to the transmission terminal Tx to the common terminal Ant, and suppresses signals of other frequencies. The reception filter 42 outputs a signal in the reception band among the high frequency signals input to the common terminal Ant to the reception terminal Rx, and suppresses signals of other frequencies. The inductor L1 functions as a matching circuit.

The transmission filter 40 is a ladder type filter and has series resonators S1 to S4 (first series resonator), parallel resonators P1 to P3 (first parallel resonator), and inductors L2 and L3. The series resonators S1 to S4 are connected in series between the common terminal Ant and the transmission terminal Tx. The parallel resonators P1 to P3 are connected in parallel between the common terminal Ant and the transmission terminal Tx. The inductor L2 is commonly connected between the parallel resonators P1 to P3 and the ground. The inductor L3 is connected between the transmission terminal Tx and the ground. The inductor L2 is an inductor for forming an attenuation pole in the reception band. The inductor L3 is an inductor for impedance matching of the transmission terminal Tx.

The receiving filter 42 is a ladder type filter and has series resonators S5 to S8 (second series resonator), parallel resonators P4 to P6 (second parallel resonator), and inductors L4 to L7. The series resonators S5 to S8 are connected in series between the common terminal Ant and the receiving terminal Rx. The parallel resonators P4 to P6 are connected in parallel between the common terminal Ant and the receiving terminal Rx. The inductors L4 to L6 are individually connected between the parallel resonators P4 to P6 and the ground. The inductor L7 is connected between the receiving terminal Rx and the ground. The inductors L4 to L6 are inductors for forming an attenuation pole in the transmission band. The inductor L7 is an inductor for impedance matching of the receiving terminal Rx.

FIG. 6 is a schematic plan view of the duplexer according to the second embodiment. As shown in FIG. 6, the series resonators S5 to S8 and the parallel resonators P1 to P3 are piezoelectric thin film resonators and are formed on the chip 60. The wiring 61 formed on the chip 60 is connected to the series resonators S5 to S8 and the parallel resonators P1 to P3. The series resonators S1 to S4 and the parallel resonators P4 to P6 are surface acoustic wave resonators and are formed on the chip 62. The wiring 63 formed on the chip 62 is connected to the series resonators S1 to S4 and the parallel resonators P4 to P6.

The chips 60 and 62 are mounted on, for example, a package (not shown) and are electrically connected by a wiring 66 formed in the package. The series resonators S5 to S8 and the parallel resonators P4 to P6 are electrically connected via the wiring 66a included in the wiring 66. The parallel resonators P1 to P3 and the series resonators S1 to S4 are electrically connected via the wiring 66b included in the wiring 66. The inductors L1 to L7 are formed by, for example, the wiring formed in the package.

In the ladder type filter, the series resonator mainly contributes to the shoulder and skirt characteristics on the high frequency side of the passband, and the parallel resonator mainly contributes to the shoulder and skirt characteristics on the low frequency side of the passband. When the reception band is higher than the transmission band, it is preferable that the temperature dependence of the shoulder and skirt characteristics on the high frequency side of the passage characteristics of the transmission filter 40 is small. Further, it is preferable that the temperature dependence of the shoulder and skirt characteristics on the high frequency side of the passing characteristics of the receiving filter 42 is small. Therefore, it is preferable that the TCFs of the series resonators S1 to S4 of the transmission filter 40 and the parallel resonators P4 to P6 of the reception filter 42 are close to 0. Therefore, the elastic wave resonator of Example 1 is used for the series resonators S1 to S4 and the parallel resonators P4 to P6. As a result, the temperature dependence of the passing characteristic near the guard bunt between the transmission band and the reception band can be suppressed.

The temperature dependence of the shoulder and skirt characteristics on the side of the pass band opposite to the guard band (that is, the low frequency side of the pass characteristic of the transmission filter 40 and the high frequency side of the pass characteristic of the reception filter 42) may be large. That is, as the parallel resonators P1 to P3 and the series resonators S5 to S8, a resonator having a larger absolute value of TCF than the series resonators S1 to S4 and the parallel resonators P4 to P6 may be used. Therefore, the parallel resonators P1 to P3 and the series resonators S5 to S8 can be selected with priority given to characteristics other than temperature dependence. For example, as the parallel resonators P1 to P3 and the series resonators S5 to S8, a piezoelectric thin film resonator is used as shown in FIG. Alternatively, as in Comparative Examples 1 and 3, a resonator containing an IDT formed on the piezoelectric substrate 10 having a congluent composition is used. Thereby, the characteristics of the duplexer can be further improved.

Although the duplexer has been described as an example in the second embodiment, the first ladder type filter and the second ladder type filter may be filters having adjacent pass bands in the multiplexer such as a triplexer or a quadplexer. The number of series resonators and parallel resonators of the first ladder type filter and the second ladder type filter can be arbitrarily selected by 1 or more.

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

10 Piezoelectric substrate 10a 1st region 10b 3rd region 10c 2nd region 12 Support substrate 14 Amorphous layer 16 Electrode finger 21 IDT
22 Reflector 40 Transmit filter 42 Receive filter

Claims (9)

Support board and
Lithium tantalate or lithium tantalate, which is bonded onto the support substrate and has a stoichiometric composition having a coefficient of linear thermal expansion in the propagation direction of elastic waves larger than the coefficient of linear thermal expansion of the support substrate in the propagation direction and a thickness of more than 1 μm. Piezoelectric substrate made of lithium niobate and
IDT provided on the upper surface of the piezoelectric substrate and
Equipped with
An elastic wave device in which the lithium composition ratio of the lower surface of the piezoelectric substrate is larger than the lithium composition ratio of the upper surface of the piezoelectric substrate. The elastic wave device according to claim 1, wherein an amorphous layer is provided between the support substrate and the piezoelectric substrate. The elastic wave device according to claim 1 or 2, wherein the support substrate is a silicon substrate, and the piezoelectric substrate is a rotating Y-cut X-propagated lithium tantalate substrate. A first series resonator connected in series between the common terminal and the first terminal, and a first parallel connected to a parallel arm between the node and the ground between the common terminal and the first terminal. A first ladder type filter having a resonator, and
A second series resonator connected in series between the common terminal and the second terminal, and a second connected to a parallel arm between the node and the ground between the common terminal and the second terminal. A second ladder type filter having a parallel resonator and having a higher pass band than the first ladder type filter.
Equipped with
The elastic wave device according to any one of claims 1 to 3, wherein the first series resonator and the second parallel resonator include the IDT. The elastic wave device according to claim 4, wherein the first parallel resonator and the second series resonator are a resonator containing an IDT formed on a piezoelectric substrate having a congluent composition, or a piezoelectric thin film resonator. A first series resonator connected in series between the common terminal and the first terminal, and a first parallel connected to a parallel arm between the node and the ground between the common terminal and the first terminal. A first ladder type filter having a resonator, and
A second series resonator connected in series between the common terminal and the second terminal, and a second connected to a parallel arm between the node and the ground between the common terminal and the second terminal. A second ladder type filter having a parallel resonator and having a higher pass band than the first ladder type filter.
Equipped with
The first series resonator and the second parallel resonator are bonded to a silicon substrate, a lithium tantalate substrate having a stoichiometric composition having a thickness of more than 1 μm, and the stoichiometric composition. IDT provided on the upper surface of the lithium tantalate substrate, which is
The first parallel resonator and the second series resonator are elastic wave devices including a lithium tantalate substrate having a congluent composition and an IDT provided on the upper surface of the lithium tantalate substrate having a congluent composition. Support board and
A rotating Y-cut X propagation substrate bonded onto the support substrate, the linear thermal expansion coefficient in the X-axis direction is larger than the linear thermal expansion coefficient of the support substrate in the X-axis direction, and the thickness is larger than 1 μm. A piezoelectric substrate made of lithium tantalate or lithium niobate, which has a metric composition,
Equipped with
The lithium composition ratio of the lower surface of the piezoelectric substrate is rather larger than the lithium composition ratio of the upper surface of the piezoelectric substrate,
The lower surface of the piezoelectric substrate is a composite substrate that is a surface on the support substrate side. By introducing lithium on both sides of a piezoelectric substrate made of lithium tantalate or lithium niobate having a congluent composition, between the first and second regions of the stoichiometric composition and the first and second regions. The step of forming the third region of the provided congluent composition and
A step of joining the first region side of the piezoelectric substrate to the support substrate, and
A step of removing the second region and the third region of the piezoelectric substrate bonded to the support substrate so that the first region is exposed.
A method for manufacturing a composite substrate including. The step of removing the second region and the third region is
A step of removing the second region by a method other than the CMP method so that the third region is exposed, and
A step of removing the third region by the CMP method so that the first region is exposed, and
Including
The method for producing a composite substrate according to claim 8, wherein the removal rate of the first region and the second region by a method other than the CMP method is higher than the removal speed of the first region and the second region by the CMP method.

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