Acoustic wave device and communication device

Abstract

The present invention makes it possible to achieve both a wide width between a resonant frequency and an anti-resonant frequency and low spurious. An elastic wave device according to the present invention has a conductor layer and excites plate waves in the SH1 mode. The Euler angles of a piezoelectric body of the elastic wave device are (α) or (β).　(α) (84°–96°, 84°–96°, 21°–45°) or a crystallographic equivalent. (β) (84°–96°, -96°–-84°, -45°–-21°) or a crystallographic equivalent.

Description

Acoustic wave devices and communication devices

[0001] The present disclosure relates to an acoustic wave device and a communication device.

[0002] Patent Document 1 discloses an elastic wave device that excites plate waves.

[0003] International Publication No. 2021 / 079830

[0004] An elastic wave device according to one aspect of the present disclosure includes a piezoelectric layer having a first surface and a second surface opposite to the first surface, an IDT electrode located on the first surface side, and a conductor layer located on the second surface side, wherein the piezoelectric layer is made of LiTaO ３ or LiNbO ３ and an Euler angle of the piezoelectric body is any one of the following (A) to (D): (A) (84° or more and 96° or less, 84° or more and 96° or less, 21° or more and 45° or less) (B) (84° or more and 96° or less, -96° or more and -84° or less, -45° or more and -21° or less) (C) Euler angle that is crystallographically equivalent to (A) above (D) Euler angle that is crystallographically equivalent to (B) above.

[0005] FIG. 1 is a cross-sectional view illustrating a configuration of an elastic wave device according to a first embodiment of the present disclosure; FIG. 2 is a cross-sectional view illustrating a first specific example of an IDT electrode; FIG. 3 is a cross-sectional view illustrating a second specific example of an IDT electrode; FIG. 4 is a view illustrating four distributions explaining the SH1 mode; FIG. 5 is a view illustrating the magnitude of spurious signals occurring within the pass band of an elastic wave device; FIG. 6 is a view illustrating the magnitude of spurious signals occurring within the pass band of an elastic wave device; FIG. 7 is a cross-sectional view illustrating a configuration of an elastic wave device according to a second embodiment of the present disclosure; and FIG. 8 is a schematic diagram of a communication device according to a third embodiment of the present disclosure.

[0006] An acoustic wave device that can achieve both a wide range between the resonant frequency and the anti-resonant frequency and small spurious emissions is desired.

[0007] According to one aspect of the present disclosure, it is possible to achieve both a wide range between the resonant frequency and the anti-resonant frequency and small spurious emissions.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are used to designate components having the same functions as those previously described, and the description thereof may not be repeated.

[0009] 1 is a cross-sectional view showing the configuration of an elastic wave device 101 according to a first embodiment of the present disclosure. The elastic wave device 101 has a piezoelectric layer 1, an IDT electrode 2, and a conductor layer 3. The piezoelectric layer 1 has a first surface 4 and a second surface 5 located on the opposite side of the first surface 4. The IDT electrode 2 is located on the first surface 4 side. The conductor layer 3 is located on the second surface 5 side. The elastic wave device 101 is an elastic wave device that excites plate waves in the SH1 mode. IDT is an abbreviation for interdigital transducer.

[0010] The piezoelectric layer 1 is LiTaO ３ or LiNbO ３ The piezoelectric material is made of LiTaO ３ is sometimes called lithium tantalate. ３ The IDT electrode 2 includes a plurality of electrode fingers 6.

[0011] The Euler angles of the piezoelectric material of the piezoelectric layer 1 are any of the following (A) to (D).

[0012] (A) (84° or more and 96° or less, 84° or more and 96° or less, 21° or more and 45° or less) (B) (84° or more and 96° or less, -96° or more and -84° or less, -45° or more and -21° or less) (C) Euler angles that are crystallographically equivalent to (A) (D) Euler angles that are crystallographically equivalent to (B) Crystallographically equivalent means that the crystal structure is common regardless of the crystal orientation, such as Euler angles (φ±120°, θ, ψ) relative to Euler angles (φ, θ, ψ).

[0013] The acoustic wave device 101 may include a functional section 7. The functional section 7 is an acoustic reflection film 8 or a gap. The conductor layer 3 may be located between the piezoelectric layer 1 and the functional section 7.

[0014] The acoustic reflection film 8 may include a low acoustic impedance layer 9 and a high acoustic impedance layer 10. The acoustic impedance of the low acoustic impedance layer 9 is lower than the acoustic impedance of the high acoustic impedance layer 10. The low acoustic impedance layer 9 is made of SiO ２ The high acoustic impedance layer 10 may include HfO ２ , Ta ２ O ５ , and ZrO ２ The high acoustic impedance layer 10 may include at least one of W, Mo, Ru, Hf, and Ta.

[0015] The number of layers included in the acoustic reflection film 8 is eight in total, consisting of four low acoustic impedance layers 9 and four high acoustic impedance layers 10, but is not limited to this. The acoustic reflection film 8 may include one, two, three, or five or more low acoustic impedance layers 9 and high acoustic impedance layers 10, respectively.

[0016] The IDT electrode 2 may contain an alloy of Cu and Al. FIG. 2 is a cross-sectional view showing a first specific example of the IDT electrode 2. FIG. 3 is a cross-sectional view showing a second specific example of the IDT electrode 2. FIGS. 2 and 3 are diagrams for explaining the layered structure of the IDT electrode 2. For simplicity of illustration, the cross-sectional shape of the IDT electrode 2 is ignored in FIGS. 2 and 3. The IDT electrode 2a is the first specific example of the IDT electrode 2, and has a layered structure of, in order from the piezoelectric layer 1 side, an underlayer 11 and an AlCu layer 12. The IDT electrode 2b is the second specific example of the IDT electrode 2, and has, in order from the piezoelectric layer 1 side, an underlayer 11, a CuAl ２ The base layer 11 has a laminated structure of a AlCu layer 13, a diffusion reduction layer 14, and an AlCu layer 12. Examples of the main components of the base layer 11 include Cr and Ti. Examples of the main components of the diffusion reduction layer 14 include Cr and Ti. The main component of a member may be defined as the component (atom) that accounts for the largest weight in the total weight of the member.

[0017] The IDT electrode 2 may include an aluminum portion whose main component is Al. In the AlCu layer 12, for example, when the weight of Cu relative to the sum of the weight of Al and the weight of Cu is approximately 1% or more and 3% or less, the AlCu layer 12 can be regarded as an aluminum portion.

[0018] The IDT electrode 2 may include a copper portion, the main component of which may be Cu. For example, CuAl ２ When the layer 13 is composed of Cu atoms and Al atoms, CuAl ２ The weight of Cu and CuAl in the total weight of the layer 13 ２ The ratio of the weight of Al to the total weight of the layer 13 is 64:54. ２ Layer 13 can be regarded as a copper portion. If the main component of the entire IDT electrode 2 is Cu, then the IDT electrode 2 can be regarded as a copper portion.

[0019] The conductor layer 3 may contain an alloy of Cu and Al. The material of the conductor layer 3 may be the material of the AlCu layer 12 or CuAl ２ It may be made of the same material as that of layer 13 .

[0020] Figure 4 shows four distributions that explain the SH1 mode. Distributions 51 to 54 are shown in Figure 4. The SH1 mode is a type of plate wave, an SH wave that vibrates parallel to the ground surface, and is its first shear horizontal mode. The vibration distribution in the SH1 mode is dominated by the uy component. In the SH1 mode, there is one node in the piezoelectric body of the piezoelectric layer 1.

[0021] Distributions 51 to 53 show displacements in the X, Y, and Z directions, respectively. The X, Y, and Z directions are perpendicular to one another. The X direction is the arrangement direction of the electrode fingers 6. The Y direction is the extension direction of the electrode fingers 6. The Z direction is the thickness direction of the piezoelectric layer 1.

[0022] The distribution 51 shows the displacement in the X direction. The horizontal axis represents the X direction, and the vertical axis represents the Z direction. The unit of the color bar is m (meters). The units of the horizontal and vertical axes are μm (micrometers).

[0023] The distribution 52 shows the displacement in the Y direction. The horizontal axis is the Y direction and the vertical axis is the Z direction. The units are the same as those of the distribution 51.

[0024] The distribution 53 shows the displacement in the Y direction. The horizontal axis represents the X direction, and the vertical axis represents the Z direction. The units are the same as those of the distribution 51.

[0025] The distribution 54 shows the electric potential. The horizontal axis is the X direction and the vertical axis is the Z direction. The unit of the color bar is V (volts). The units of the horizontal and vertical axes are μm (micrometers).

[0026] Elastic wave device 101 can achieve both a wide range between the resonant frequency and the anti-resonant frequency and small spurious emissions. The effects of elastic wave device 101 will now be described.

[0027] Elastic wave device 101 is a type of elastic wave device that excites elastic waves using a so-called X-cut piezoelectric material. Conventional elastic wave devices that excite elastic waves using an X-cut piezoelectric material have a wide range between the resonant frequency and the anti-resonant frequency, but tend to have large spurious emissions. Elastic wave device 101 can be interpreted as an elastic wave device that achieves small spurious emissions among elastic wave devices that excite elastic waves using an X-cut piezoelectric material.

[0028] The thickness of the piezoelectric layer 1 is defined as P. The line width of the electrode fingers 6 of the IDT electrode 2 is defined as L. The distance between two adjacent electrode fingers 6 of the IDT electrode 2 is defined as S. Hereinafter, for convenience of explanation, P, L, and S may be referred to as the thickness P, line width L, and distance S, respectively.

[0029] 5 and 6 are diagrams showing the magnitude of spurious signals occurring within the pass band of elastic wave device 101. The pass band of elastic wave device 101 may refer to a frequency band through which signals in elastic wave device 101 pass.

[0030] Fig. 5 shows a case where the main component of the IDT electrode 2 is Al, and Fig. 6 shows a case where the main component of the IDT electrode 2 is Cu.

[0031] 5 and 6, the horizontal axis represents the ratio of line width L to thickness P. The ratio of line width L to thickness P has no unit. In each of FIGS. 5 and 6, the vertical axis represents the ratio of distance S to thickness P. The ratio of distance S to thickness P has no unit. The real value of thickness P is 0.345083904 μm, which corresponds to 0.5 times the wavelength λ of the elastic wave excited by elastic wave device 101.

[0032] 5 and 6, the relative magnitude of spurious signals for combinations of line width L / thickness P and distance S / thickness P is shown as an evaluation value ranging from −90 to 90. The evaluation value is unitless, and the closer to 90 the value, the smaller the spurious signals.

[0033] It was found that spurious emissions were small within range 55. The magnitude of line width L / thickness P corresponding to range 55 was 0.34 or more and 3.43 or less. That is, when the thickness of piezoelectric layer 1 is P and the line width of electrode fingers 6 of IDT electrode 2 is L, L / P may be 0.34 or more and 3.43 or less. The magnitude of distance S / thickness P corresponding to range 55 was 0.42 or more and 4.30 or less. That is, when the thickness of piezoelectric layer 1 is P and the distance between two adjacent electrode fingers 6 of IDT electrode 2 is S, S / P may be 0.42 or more and 4.30 or less.

[0034] The straight lines 56 to 59 are each expressed by the following formula, where X is the ratio of line width L to thickness P, and Y is the ratio of distance S to thickness P.

[0035] Line 56: Y = -1.2516X + 0.20 Line 57: Y = -1.2516X + 2.20 Line 58: Y = -1.2516X + 3.07 Line 59: Y = -1.2516X + 4.29 It was found that spurious responses were small between line 56 and line 59. That is, when the thickness of piezoelectric layer 1 is P, the line width of electrode fingers 6 of IDT electrode 2 is L, the distance between two adjacent electrode fingers 6 of IDT electrode 2 is S, L / P is X, and S / P is Y, Y may be greater than or equal to -1.2516X + 0.20 and less than or equal to -1.2516X + 4.29.

[0036] It has been found that the spurious signals are smaller between lines 56 and 57 and between lines 58 and 59 than between lines 57 and 58. That is, Y may be greater than or equal to −1.2516X+0.20 and less than or equal to −1.2516X+2.20, or greater than or equal to −1.2516X+3.07 and less than or equal to −1.2516X+4.29.

[0037] 7 is a cross-sectional view illustrating a configuration of an elastic wave device 101 according to a second embodiment of the present disclosure. The functional portion 7 may be a gap 15.

[0038] An elastic wave device 101 according to a second embodiment of the present disclosure is a so-called membrane-structure elastic wave device. In the membrane-structure elastic wave device 101, a void 15 is formed on the second surface 5 side of the support substrate 16, and the piezoelectric layer 1 is positioned to cover the void 15. The membrane-structure elastic wave device 101 does not necessarily have to include the acoustic reflection film 8.

[0039] 8 is a schematic diagram of a communication device 201 according to a third embodiment of the present disclosure. The communication device 201 is an application example of the acoustic wave device 101 and performs wireless communication using radio waves. The communication device 201 may include a transmit filter 111 and a receive filter 112. Each of the transmit filter 111 and the receive filter 112 may include the acoustic wave device 101.

[0040] In the communication device 201, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised by an RF-IC 113 and converted into a transmission signal TS. RF-IC is an abbreviation for radio frequency-integrated circuit. In other words, frequency-raising is conversion into a high-frequency signal having a carrier frequency. A band-pass filter 114 may remove unnecessary components from the transmission signal TS outside the transmission passband. Next, the transmission signal TS after removing the unnecessary components may be amplified by an amplifier 115 and input to the transmission filter 111.

[0041] The transmission filter 111 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 111 may output the transmission signal TS after removing the unnecessary components to the antenna 116 via the antenna terminal. The antenna 116 may convert the transmission signal TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio signals to the outside of the communication device 201.

[0042] The antenna 116 may convert a received external radio wave into a received signal RS, which is an electrical signal, and input the received signal RS to the receive filter 112 via the antenna terminal. The receive filter 112 may remove unnecessary components outside the receive passband from the input received signal RS. The receive filter 112 may output the received signal RS after the unnecessary components have been removed to the amplifier 117. The output received signal RS may be amplified by the amplifier 117. The bandpass filter 118 may remove unnecessary components outside the receive passband from the amplified received signal RS. The received signal RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 113, and converted into a received information signal RIS.

[0043] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals containing appropriate information. The low-frequency signals may be baseband signals. For example, the transmit information signal TIS and the receive information signal RIS may be analog audio signals or digitized audio signals. The passband of the radio signals may be set appropriately and may comply with various known standards.

[0044] [Summary] An elastic wave device according to a first aspect of the present disclosure includes a piezoelectric layer having a first surface and a second surface opposite to the first surface, an IDT electrode located on the first surface side, and a conductor layer located on the second surface side, wherein the piezoelectric layer is made of LiTaO ３ or LiNbO ３and an Euler angle of the piezoelectric body is any one of the following (A) to (D): (A) (84° or more and 96° or less, 84° or more and 96° or less, 21° or more and 45° or less) (B) (84° or more and 96° or less, -96° or more and -84° or less, -45° or more and -21° or less) (C) Euler angle that is crystallographically equivalent to (A) above (D) Euler angle that is crystallographically equivalent to (B) above.

[0045] In the elastic wave device according to aspect 2 of the present disclosure, in the first aspect, when the thickness of the piezoelectric layer is P and the line width of the electrode fingers of the IDT electrode is L, L / P is 0.34 or more and 3.43 or less.

[0046] In the elastic wave device according to aspect 3 of the present disclosure, in the first aspect, when the thickness of the piezoelectric layer is P and the distance between two adjacent electrode fingers of the IDT electrode is S, S / P is greater than or equal to 0.42 and less than or equal to 4.30.

[0047] An elastic wave device according to aspect 4 of the present disclosure is the same as that of aspect 1, wherein P is the thickness of the piezoelectric layer, L is the line width of the electrode fingers of the IDT electrode, S is the distance between two adjacent electrode fingers of the IDT electrode, L / P is X, and S / P is Y, where Y is greater than or equal to −1.2516X+0.20 and less than or equal to −1.2516X+4.29.

[0048] An elastic wave device according to a fifth aspect of the present disclosure is related to the fourth aspect, wherein Y is greater than or equal to −1.2516X+0.20 and less than or equal to −1.2516X+2.20, or greater than or equal to −1.2516X+3.07 and less than or equal to −1.2516X+4.29.

[0049] An elastic wave device according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, further comprising a functional portion that is an acoustic reflection film or a void, and the conductor layer is positioned between the piezoelectric layer and the functional portion.

[0050] According to a seventh aspect of the present disclosure, in the acoustic wave device of any one of the first to sixth aspects, the IDT electrode includes an alloy of Cu and Al.

[0051] An elastic wave device according to an eighth aspect of the present disclosure is the elastic wave device of any one of the first to seventh aspects, wherein the IDT electrode includes an aluminum portion, and the aluminum portion is mainly composed of Al.

[0052] According to a ninth aspect of the present disclosure, in the elastic wave device of any one of the first to seventh aspects, the IDT electrode includes a copper portion, and the copper portion is mainly composed of Cu.

[0053] According to a tenth aspect of the present disclosure, in the elastic wave device of any one of the first to ninth aspects, the conductor layer includes an alloy of Cu and Al.

[0054] A communication device according to an eleventh aspect of the present disclosure includes the acoustic wave device according to any one of the first to tenth aspects.

[0055] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0056] REFERENCE SIGNS LIST 1 Piezoelectric layer 2, 2a, 2b IDT electrode 3 Conductor layer 4 First surface 5 Second surface 6 Electrode finger 7 Functional portion 8 Acoustic reflection film 9 Low acoustic impedance layer 10 High acoustic impedance layer 11 Underlayer 12 AlCu layer 13 CuAl ２ Layer 14 Diffusion reduction layer 15 Air gap 16 Support substrate 101 Acoustic wave device 201 Communication device L Line width of electrode fingers of IDT electrode P Thickness of piezoelectric layer S Distance between two adjacent electrode fingers of IDT electrode

Claims

1. A piezoelectric element comprising: a piezoelectric layer having a first surface and a second surface located on the opposite side of the first surface; an IDT electrode located on the first surface side; and a conductor layer located on the second surface side, wherein the piezoelectric layer is made of LiTaO ３ or LiNbO ３ an Euler angle of the piezoelectric body is any one of the following (A) to (D): (A) (84° or more and 96° or less, 84° or more and 96° or less, 21° or more and 45° or less); (B) (84° or more and 96° or less, -96° or more and -84° or less, -45° or more and -21° or less); (C) an Euler angle that is crystallographically equivalent to (A); or (D) an Euler angle that is crystallographically equivalent to (B).

2. The acoustic wave device according to claim 1, wherein, when the thickness of the piezoelectric layer is P and the line width of the electrode fingers of the IDT electrode is L, L / P is equal to or greater than 0.34 and equal to or less than 3.

43.

3. The elastic wave device according to claim 1, wherein, when the thickness of the piezoelectric layer is P and the distance between two adjacent electrode fingers of the IDT electrode is S, S / P is equal to or greater than 0.42 and equal to or less than 4.

30.

4. The acoustic wave device of claim 1, wherein P is the thickness of the piezoelectric layer, L is the line width of the electrode fingers of the IDT electrode, S is the distance between two adjacent electrode fingers of the IDT electrode, L / P is X, and S / P is Y, and Y is not less than -1.2516X+0.20 and not more than -1.2516X+4.

29.

5. The acoustic wave device according to claim 4, wherein Y is equal to or greater than −1.2516X+0.20 and equal to or less than −1.2516X+2.20, or equal to or greater than −1.2516X+3.07 and equal to or less than −1.2516X+4.

29.

6. An elastic wave device according to any one of claims 1 to 5, further comprising a functional section which is an acoustic reflection film or a void, and wherein the conductor layer is positioned between the piezoelectric layer and the functional section.

7. The acoustic wave device according to claim 1, wherein the IDT electrode contains an alloy of Cu and Al.

8. The acoustic wave device according to claim 1, wherein the IDT electrode includes an aluminum portion, and the aluminum portion is mainly composed of Al.

9. The acoustic wave device according to claim 1, wherein the IDT electrode includes a copper portion, and the copper portion is mainly composed of Cu.

10. The acoustic wave device according to claim 1, wherein the conductor layer contains an alloy of Cu and Al.

11. A communication device comprising the acoustic wave device according to any one of claims 1 to 10.

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