JP6949607B2 - Elastic wave device - Google Patents

Description

The present invention relates to elastic wave devices, for example, elastic wave devices having a piezoelectric substrate.

Elastic wave devices using elastic wave resonators are used, for example, in filters and multiplexers for mobile multi-communication. In the elastic surface resonator, an IDT (Interdigital Transducer) that excites a surface acoustic wave is formed on a piezoelectric substrate. (Patent Document 1).

JP-A-2007-184690

The piezoelectric substrate has a large coefficient of linear thermal expansion. Therefore, when the temperature changes, the frequency in the elastic wave device changes.

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 an elastic wave device.

The present invention includes a piezoelectric substrate and a pair of comb-shaped electrodes each provided on the piezoelectric substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected, and an input terminal and an output terminal. A plurality of series resonators connected in series between the two, and one or a plurality of parallel resonators provided on the piezoelectric substrate and connected in parallel between the input terminal and the output terminal. a ladder filter, the pair of comb-shaped electrodes in the highest antiresonant frequency first resonator of the plurality of electrode fingers provided therebetween in the extending direction of stretching of the plurality of serial resonators, the plurality The pair of comb-shaped electrodes in at least one resonator of the second resonator whose anti-resonance frequency is lower than the anti-resonance frequency of the first resonator among the series resonators of the above are provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction. An elastic wave comprising at least a part of the piezoelectric substrate and a pair of metal layers having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers are arranged on the piezoelectric substrate. It is a device.
In the above configuration, the one or more parallel resonators are a plurality of parallel resonators, and a pair provided on the piezoelectric substrate and each having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected. The elastic wave device comprises the comb-shaped electrodes of the above, and the elastic wave device extends the pair of comb-shaped electrodes in the third resonator having the lowest resonance frequency among the plurality of parallel resonators in the stretching direction in which the plurality of electrode fingers extend. The pair of comb-shaped electrodes in at least one resonator of the fourth resonator, which is provided so as to be sandwiched and has a resonance frequency higher than the resonance frequency of the third resonator among the plurality of parallel resonators, is sandwiched in the stretching direction. A pair of other metals that are not provided in such a manner, are at least partially embedded in the piezoelectric substrate, and have a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers of the piezoelectric substrate are arranged. It can be configured to include layers.

The present invention includes a piezoelectric substrate, one or more series resonators provided on the piezoelectric substrate and connected in series between an input terminal and an output terminal, and a plurality of electrodes provided on the piezoelectric substrate. Each includes a pair of comb-shaped electrodes each having a finger and a bus bar to which the plurality of electrode fingers are connected, and a plurality of parallel resonators connected in parallel between the input terminal and the output terminal. The rudder type filter and the pair of comb-shaped electrodes in the first resonator having the lowest resonance frequency among the plurality of parallel resonators are provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction in which the plurality of electrode fingers extend. The pair of comb-shaped electrodes in at least one resonator of the second resonator having a resonance frequency higher than the resonance frequency of the first resonator among the parallel resonators is not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction. An elastic wave device comprising at least a part embedded in a piezoelectric substrate and a pair of metal layers having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers of the piezoelectric substrate are arranged. ..

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

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

In the above configuration, the length of the metal layer may be larger than the length of the bus bar in the first resonator in the direction in which the plurality of electrode fingers are arranged.

In the above configuration, a support substrate having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient of the piezoelectric substrate is provided by being joined to a surface of the piezoelectric substrate opposite to the surface on which the pair of comb-shaped electrodes are provided. can do.

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

In the above configuration, no other metal layer may be provided between the pair of comb-shaped electrodes and the pair of metal layers in the first resonator.

In the above configuration, the Young's modulus of the pair of metal layers can be larger than the Young's modulus of the piezoelectric substrate.

In the above configuration, a pair of electrodes provided on the piezoelectric substrate, connected to the pair of comb-shaped electrodes, intersect with the pair of metal layers in a plan view, and electrically connected to the pair of metal layers, respectively. It can be configured to include wiring.

In the above configuration, the configuration may include a multiplexer including the ladder type filter.

The present invention includes a piezoelectric substrate and a pair of comb-shaped electrodes each provided on the piezoelectric substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected, and a common terminal and a first terminal. A plurality of first series resonators connected in series between the two, and one or a plurality of first parallel resonators provided on the piezoelectric substrate and connected in parallel between the common terminal and the first terminal. A first ladder type filter including a resonator, one or more second series resonators provided on the piezoelectric substrate and connected in series between the common terminal and the second terminal, and the piezoelectric Each of the pair of comb-shaped electrodes provided on the substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected is provided, and is connected in parallel between the common terminal and the second terminal. a plurality of second parallel resonator, was a second ladder-type filter which have a high pass band than the first ladder-type filter, the highest antiresonant frequency among the plurality of first series resonator first The pair of comb-shaped electrodes in one resonator are provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction in which the plurality of electrode fingers extend, and anti-resonance is performed from the anti-resonance frequency of the first resonator among the plurality of first series resonators. The pair of comb-shaped electrodes in at least one resonator of the second resonator having a low frequency are not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction, and at least a part thereof is embedded in the piezoelectric substrate. The pair of first metal layers having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers are arranged, and the third resonator having the lowest resonance frequency among the plurality of second parallel resonators. A fourth resonator having a pair of comb-shaped electrodes sandwiched in a stretching direction in which the plurality of electrode fingers are stretched and having a resonance frequency higher than the resonance frequency of the third resonator among the plurality of second parallel resonators. The pair of comb-shaped electrodes in at least one resonator of the above are not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction, and at least a part thereof is embedded in the piezoelectric substrate, and the plurality of electrode fingers of the piezoelectric substrate are arranged. A multiplexer comprising a pair of second metal layers having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction .

According to the present invention, it is possible to suppress the temperature dependence of the frequency in the elastic wave device.

1 (a) is a plan view of the elastic wave device according to the first embodiment, and FIGS. 1 (b) and 1 (c) are a cross section taken along the line AA and a cross section taken along the line BB of FIG. 1 (a). 2 (a) and 2 (b) are cross-sectional views of the elastic wave device according to the first modification of the first embodiment. FIG. 3 (a) shows the thicknesses T10, T11 and T26 and the material of the metal layer in each sample, and FIG. 3 (b) shows Young's modulus, Poisson's ratio and linear thermal expansion coefficient of each material used in the simulation. It is a figure which shows. FIG. 4 is a diagram showing the coefficient of thermal expansion with respect to the thickness T26 of the metal layer showing the simulation result. FIG. 5 is a plan view of the elastic wave device according to the second embodiment. FIG. 6 is a diagram showing the attenuation characteristics of each resonator in the second embodiment. 7 (a) to 7 (c) are cross-sectional views of the elastic wave device according to the third embodiment and the first and second modifications thereof. FIG. 8A is a cross-sectional view of the elastic wave element 52 in Example 3 and its modified example, and FIG. 8B is a circuit diagram of a duplexer according to Modified Example 3 of Example 3.

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

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

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

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

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

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

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

[simulation]
The coefficient of thermal expansion in Example 1 and its modified example 1 was simulated. In the simulation, the temperature was changed, and the expansion of the distance between the portions 28 located at the center of the metal layers 26 in the Y direction and at the end of the metal layers 26 in the X direction in FIG. 1A was simulated. The rate of change in the distance between the locations 28 per 1 ° C. was defined as the coefficient of thermal expansion (unit: / ° C.). In order to distinguish it from the coefficient of linear thermal expansion of the material, it will be referred to as the coefficient of thermal expansion below.

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

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

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

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

In the samples D1 to D3 of Comparative Example 2, the coefficient of thermal expansion becomes smaller as the thickness T26 of the metal layer 26 and the thickness T10 of the piezoelectric substrate 10 become smaller. In the samples B1 to B3 of the modification 1 of the first embodiment, the coefficient of thermal expansion is smaller than the samples D1 to D3. In the samples C1 to C3, the coefficient of thermal expansion is slightly smaller than that of the samples D1 to D3.

According to the first embodiment and the first modification thereof, as shown in FIGS. 1A to 2B, the pair of metal layers 26 are embedded in the piezoelectric substrate 10 and the pair of comb-shaped electrodes 18 in the Y direction. It is provided so as to sandwich. As a result, the coefficient of thermal expansion of the portion 28 in FIG. 1A can be suppressed. Therefore, it is possible to suppress the temperature change of the frequency of the elastic wave device.

At least a part of the metal layer 26 may be embedded in the piezoelectric substrate 10. As a result, the metal layer 26 can support the stress due to the expansion or contraction of the piezoelectric substrate 10 in the X direction. It is preferable that all or a part of the side surface of the metal layer 26 is in contact with the piezoelectric substrate 10. Like the samples A1 to A3 and B1 to B3, the coefficient of linear thermal expansion of the metal layer 26 is smaller than the coefficient of linear thermal expansion of the piezoelectric substrate 10 in the X direction. As a result, the coefficient of thermal expansion of the portion 28 in FIG. 1A can be further suppressed. Therefore, the temperature change of the frequency of the elastic wave device can be further suppressed. The coefficient of linear thermal expansion of the metal layer 26 is preferably 2/3 or less, more preferably 1/2 or less of the coefficient of linear thermal expansion of the piezoelectric substrate 10. The metal layer 26 may be a metal layer other than the Cu layer or the W layer.

The pair of metal layers 26 may overlap a part of the pair of comb-shaped electrodes 18 when viewed from the Y direction. When the pair of reflectors 22 are provided so as to sandwich the pair of comb-shaped electrodes 18 in the X direction, it is preferable that the pair of metal layers 26 are provided so as to sandwich the pair of reflectors 22. As a result, the temperature change of the frequency of the elastic wave device can be further suppressed.

In the X direction, the length of the pair of metal layers 26 is greater than the length of the bus bar 16. As a result, the temperature change of the frequency of the elastic wave device can be further suppressed.

In order to reduce the coefficient of thermal expansion, the width of the metal layer 26 in the Y direction is preferably 0.1 times or more, more preferably 0.2 times or more the width of the pair of comb-shaped electrodes 18 in the Y direction. In order to reduce the chip area, the width of the metal layer 26 in the Y direction is preferably 1 times or less, more preferably 0.7 times or less the width of the pair of comb-shaped electrodes 18 in the Y direction. In order to reduce the coefficient of thermal expansion, the gap width between the metal layer 26 and the pair of comb-shaped electrodes 18 is preferably 0.5 times or less, preferably 0.2 times or less the width of the pair of comb-shaped electrodes 18 in the Y direction. The following is more preferable.

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

The thickness of the metal film 12 and the wiring 24 is 1 μm or less. In order to reduce the coefficient of thermal expansion, the thickness T26 of the metal layer 26 is preferably thicker than that of the metal film 12 and the wiring 24. The thickness T26 of the metal layer 26 is preferably 2 times or more, more preferably 5 times or more, still more preferably 10 times or more the thickness of the metal film 12 and the wiring 24. From the viewpoint of simplifying the manufacturing process, the thickness of the metal layer 26 is preferably 1/3 or less, more preferably 1/5 or less of the total thickness of the piezoelectric substrate 10 and the support substrate 11. The depth at which the metal layer 26 is embedded in the piezoelectric substrate 10 is preferably 1 times or more, more preferably 5 times or more, still more preferably 10 times or more the thickness of the metal film 12 and the wiring 24. From the viewpoint of simplifying the manufacturing process, the depth at which the metal layer 26 is embedded in the piezoelectric substrate 10 is preferably 1/3 or less, more preferably 1/5 or less of the total thickness of the piezoelectric substrate 10 and the support substrate 11. ..

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

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

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

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

When the support substrate 11 is provided, the metal layer 26 preferably penetrates the piezoelectric substrate 10 in the Z direction. As a result, the coefficient of thermal expansion can be reduced. The metal layer 26 does not have to penetrate the piezoelectric substrate 10 in the Z direction.

FIG. 5 is a plan view of the elastic wave device according to the second embodiment. As shown in FIG. 5, one or a plurality of series resonators S1 to S4, one or a plurality of parallel resonators P1 to P3, a wiring 24, and a bump 25 are provided on the piezoelectric substrate 10. Each resonator includes a reflector 22 provided on both sides of the IDT 20 and the IDT 20 in the X direction. The bump 25 includes an input bump T1, an output bump T2 and a ground bump Tg. The wiring 24 electrically connects between the resonators and between each resonator and the bump 25. The bump 25 is, for example, a stud Au bump, a Cu pillar formed by a plating method, or a solder ball such as AuSn, SnAgCu or SnAg.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The elastic wave element 21 in the third embodiment and its modified example is the elastic surface wave resonator shown in FIGS. 1 (a) to 2 (b). FIG. 8A is a cross-sectional view of the elastic wave element 52 in Example 3 and its modified example. As shown in FIG. 8A, the elastic wave element 52 is a piezoelectric thin film resonator. A piezoelectric film 66 is provided on the substrate 50. The lower electrode 64 and the upper electrode 68 are provided so as to sandwich the piezoelectric film 66. A gap 65 is formed between the lower electrode 64 and the substrate 50. The lower electrode 64 and the upper electrode 68 excite elastic waves in the thickness longitudinal vibration mode in the piezoelectric film 66. The lower electrode 64 and the upper electrode 68 are metal films such as a ruthenium film. The piezoelectric film 66 is, for example, an aluminum nitride film.

Although the example in which the elastic wave element 52 is provided on the lower surface of the substrate 50 has been described, the elastic wave element 52 may not be provided on the lower surface of the substrate 50. For example, an active element such as an amplifier and / or a switch may be provided on the lower surface of the substrate 50. Further, a passive element such as an inductor and / or a capacitor may be provided on the lower surface of the substrate 50. A MEMS (Micro Electro Mechanical Systems) element may be provided on the lower surface of the substrate 50.

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

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

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

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

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

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

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 board 11 Support board 12 Metal film 14 Electrode finger 16 Busbar 18 Comb type electrode 20 IDT
22 Reflector 24 Wiring 26 Metal layer 60 Transmit filter 62 Receive filter

Claims (13)

Piezoelectric board and
Each of the pair of comb-shaped electrodes provided on the piezoelectric substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected is provided, and is connected in series between the input terminal and the output terminal. With multiple series resonators,
One or more parallel resonators provided on the piezoelectric substrate and connected in parallel between the input terminal and the output terminal.
Ladder type filter with
The pair of comb-shaped electrodes in the first resonator having the highest anti-resonance frequency among the plurality of series resonators are provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction in which the plurality of electrode fingers extend , and the plurality of series resonators. Of these, the pair of comb-shaped electrodes in at least one resonator of the second resonator whose anti-resonance frequency is lower than the anti-resonance frequency of the first resonator is not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction, and the piezoelectric substrate. A pair of metal layers having at least a part embedded in the piezoelectric substrate and having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers are arranged on the piezoelectric substrate.
An elastic wave device equipped with. Piezoelectric board and
One or more series resonators provided on the piezoelectric substrate and connected in series between the input terminal and the output terminal.
Each of the pair of comb-shaped electrodes provided on the piezoelectric substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected is provided, and is connected in parallel between the input terminal and the output terminal. A ladder type filter with a plurality of parallel resonators, and
The pair of comb-shaped electrodes in the first resonator having the lowest resonance frequency among the plurality of parallel resonators is provided so as to be sandwiched in the stretching direction in which the plurality of electrode fingers extend, and among the plurality of parallel resonators. The pair of comb-shaped electrodes in at least one resonator of the second resonator having a resonance frequency higher than the resonance frequency of the first resonator is not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction, and at least one is provided on the piezoelectric substrate. A pair of metal layers in which the portions are embedded and have a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers are arranged on the piezoelectric substrate.
An elastic wave device equipped with. The one or a plurality of parallel resonators is a plurality of parallel resonators, and is a pair of comb-shaped electrodes provided on the piezoelectric substrate and each having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected. With each
The elastic wave device is provided so as to sandwich the pair of comb-shaped electrodes in the third resonator having the lowest resonance frequency among the plurality of parallel resonators in the stretching direction in which the plurality of electrode fingers extend. The pair of comb-shaped electrodes in at least one resonator of the fourth resonator having a resonance frequency higher than the resonance frequency of the third resonator is not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction. The first aspect of the present invention includes a pair of other metal layers having at least a part embedded in the piezoelectric substrate and having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers of the piezoelectric substrate are arranged. The described elastic wave device. The elasticity according to any one of claims 1 to 3, wherein the first resonator includes a pair of reflectors provided so as to sandwich the pair of comb-shaped electrodes in a direction in which the plurality of electrode fingers are arranged. Wave device. The elastic wave device according to claim 4, wherein the pair of metal layers are provided so as to sandwich the pair of reflectors. The elastic wave device according to any one of claims 1 to 5 , wherein the length of the metal layer is larger than the length of the bus bar in the first resonator in the direction in which the plurality of electrode fingers are arranged. The piezoelectric substrate of the pair comb electrodes is bonded to a surface opposite to the surface provided, of claims 1 to 6 having a supporting substrate having a linear thermal expansion coefficient smaller linear thermal expansion coefficient of said piezoelectric substrate The elastic wave device according to any one of the above. The elastic wave device according to claim 7, wherein the coefficient of linear thermal expansion of the pair of metal layers is smaller than the coefficient of linear thermal expansion of the support substrate. The elastic wave device according to any one of claims 1 to 8 , wherein no other metal layer is provided between the pair of comb-shaped electrodes and the pair of metal layers in the first resonator. The elastic wave device according to any one of claims 1 to 9, wherein the Young's modulus of the pair of metal layers is larger than the Young's modulus of the piezoelectric substrate. A claim comprising a pair of wires provided on the piezoelectric substrate, connected to the pair of comb-shaped electrodes, intersecting the pair of metal layers in a plan view, and electrically connected to the pair of metal layers. Item 2. The elastic wave device according to any one of Items 1 to 10. The elastic wave device according to any one of claims 1 to 11, further comprising a multiplexer including the ladder type filter. Piezoelectric board and
Each of the pair of comb-shaped electrodes provided on the piezoelectric substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected is provided, and is connected in series between the common terminal and the first terminal. a plurality of first series resonator,
One or more first parallel resonators provided on the piezoelectric substrate and connected in parallel between the common terminal and the first terminal .
1st ladder type filter equipped with
A second series resonator provided on the piezoelectric substrate and connected in series between the common terminal and the second terminal, and a plurality of second series resonators.
Each of the pair of comb-shaped electrodes provided on the piezoelectric substrate and having a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected is provided in parallel between the common terminal and the second terminal. and a plurality of second parallel resonator connected, a second ladder-type filter which have a high pass band than the first ladder-type filter,
The pair of comb-shaped electrodes in the first resonator having the highest anti-resonance frequency among the plurality of first series resonators are provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction in which the plurality of electrode fingers extend. Of the series resonators, the pair of comb-shaped electrodes in at least one resonator of the second resonator whose anti-resonance frequency is lower than the anti-resonance frequency of the first resonator is not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction. A pair of first metal layers having at least a part embedded in the piezoelectric substrate and having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers of the piezoelectric substrate are arranged.
The pair of comb-shaped electrodes in the third resonator having the lowest resonance frequency among the plurality of second parallel resonators are provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction in which the plurality of electrode fingers extend, and the plurality of second parallel resonators are provided. Of the resonators, the pair of comb-shaped electrodes in at least one resonator of the fourth resonator having a resonance frequency higher than the resonance frequency of the third resonator is not provided so as to sandwich the pair of comb-shaped electrodes in the stretching direction, and the piezoelectric is provided. A pair of second metal layers, at least partially embedded in the substrate, having a linear thermal expansion coefficient smaller than the linear thermal expansion coefficient in the direction in which the plurality of electrode fingers of the piezoelectric substrate are arranged.
A multiplexer equipped with.

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