Elastic wave devices and modules

Abstract

The present application provides an elastic wave device and module, the elastic wave device includes a support layer, a piezoelectric layer, a functional layer and an IDT electrode structure, the IDT electrode structure is arranged on the upper surface of the piezoelectric layer; the piezoelectric layer is stacked on the upper part of the functional layer; the functional layer is stacked on the upper part of the support layer; wherein the IDT electrode structure and the piezoelectric layer are used to excite elastic waves with a sound velocity higher than 6000m / s, the wavelength of the main mode elastic wave is λ; the distance between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer is 550MHz~1000MHz. The above elastic wave device solves the problem of large high-order spurious in high-frequency elastic wave devices in the prior art, and while suppressing the high-order spurious of high-frequency elastic wave devices, the electromechanical coupling coefficient and quality factor of the elastic wave device are improved.

Description

Technical Field

[0001] The present application relates to the field of radio frequency technology, and in particular to elastic wave devices and modules with an elastic wave speed higher than 6000 m / s. Background Art

[0002] A surface acoustic wave (SAW) resonator is an elastic wave device that uses the propagation characteristics of surface acoustic waves on the surface of a piezoelectric layer. Its working principle is to convert electrical signals into acoustic wave signals and then back to electrical signals through two sets of alternating IDT electrode structures (Interdigital Transducer) on a piezoelectric substrate. The above-mentioned SAW resonators are usually used in filters and other radio frequency (RF) applications.

[0003] In radio frequency communication systems, since common interference sources (such as household appliances, automobile ignition systems, etc.) usually generate low-frequency noise, high-frequency signals can avoid electromagnetic interference (EMI) from the environment better than low-frequency signals; high-frequency bands allow higher data transmission rates, which is crucial for applications that require high-speed transmission (such as 5G communications, satellite communications, etc.); high-frequency band signals have less reflection and diffraction effects in the physical environment, which helps to reduce the negative impact of multipath propagation.

[0004] For SAW resonators that use traditional surface acoustic waves (such as Rayleigh waves or shear waves) as the main mode, due to their low sound velocity (about 4000m / s) and the limitations of existing processes in actual production, such as the selection of device materials, device manufacturing processes, and the design of IDT spacing, it is difficult to meet high-frequency applications (usually above 3GHz).

[0005] In the prior art, the problem that the traditional SAW resonator is difficult to meet high-frequency application requirements can be solved by manufacturing an elastic wave device with an elastic wave speed higher than that of a surface acoustic wave. For example, by specially designing the piezoelectric layer and the IDT electrode structure, the main mode of the acoustic wave excited by the elastic wave device can be a symmetrical S0 Lamb wave, and the sound speed of the symmetrical S0 Lamb wave (greater than 6000m / s) excited by the above structure is higher than that of the traditional surface acoustic wave mode. Therefore, an elastic wave device with a symmetrical S0 Lamb wave as the main mode can meet the high-frequency requirements. However, when the main mode elastic wave of the elastic wave device is a symmetrical S0 Lamb wave, due to its obvious dispersion characteristics, it will cause the energy difference of the acoustic waves of other high-order spurious modes to increase, thereby increasing the spurious level of the elastic wave device.

[0006] The high-frequency elastic wave devices mentioned above have large high-order stray problems, and there is currently no suitable solution. Summary of the invention

[0007] In this embodiment, an elastic wave device and a module are provided to solve the problem of large high-order stray signals in high-frequency elastic wave devices.

[0008] In the first aspect, the present application provides an elastic wave device, which includes, from bottom to top, a supporting layer, a functional layer, a piezoelectric layer and an IDT electrode structure, wherein the IDT electrode structure is arranged on the upper surface of the piezoelectric layer; the piezoelectric layer is stacked on the upper part of the functional layer; the functional layer is stacked on the upper part of the supporting layer; wherein the IDT electrode structure and the piezoelectric layer are used to excite elastic waves with a sound velocity higher than 6000m / s, and the wavelength of the elastic wave is λ; the interval between the anti-resonance frequency of the elastic wave and the cut-off frequency of the supporting layer is 550MHz~1000MHz.

[0009] In some embodiments, the piezoelectric layer is made of lithium niobate or lithium tantalate.

[0010] The thickness of the piezoelectric layer ranges from 0.1λ to 0.25λ.

[0011] The piezoelectric layer has a crystal cutting direction of Euler angles of (40°±15°, 90°±15°, -90°±15°), and the mode of the elastic wave used for excitation is a symmetrical S0 Lamb wave.

[0012] In some embodiments, the acoustic impedance of the material constituting the functional layer is greater than 3.1 kg / .

[0013] In some embodiments, when the constituent material of the functional layer is silicon carbide, the thickness of the functional layer is in the range of 0.4λ to 1.4λ.

[0014] When the constituent material of the functional layer is diamond, the thickness of the functional layer ranges from 0.3λ to 1.2λ.

[0015] In some of the embodiments, the thickness of the IDT electrode structure ranges from 0.02λ to 0.1λ.

[0016] In some of the embodiments, the metallization ratio of the electrode structure is in the range of 0.2-0.7.

[0017] In some of the embodiments, the elastic wave device further includes a low acoustic velocity layer; the low acoustic velocity layer is stacked on the upper part or the lower part of the functional layer.

[0018] In some of the embodiments, the low acoustic velocity layer is made of a material including silicon oxide, gallium arsenide or tantalum oxide.

[0019] In some of the embodiments, the supporting layer is made of a material including spinel, sapphire, silicon or quartz.

[0020] In some embodiments, the thickness of the low acoustic velocity layer ranges from 0.01λ to 0.4λ.

[0021] In a second aspect, the present application provides a module comprising a plurality of elastic wave devices as described in the first aspect.

[0022] Compared with the related art, an elastic wave device and a module are provided in this embodiment. The elastic wave device includes a support layer, a piezoelectric layer, a functional layer and an IDT electrode structure. The IDT electrode structure is arranged on the upper surface of the piezoelectric layer; the piezoelectric layer is stacked on the upper part of the functional layer; the functional layer is stacked on the upper part of the support layer, and is used to suppress the stray formed by the longitudinal electric field, improve the electromechanical coupling coefficient, and improve the quality factor; wherein the IDT electrode structure and the piezoelectric layer are used to excite elastic waves with a speed higher than 6000m / s, and the wavelength of the elastic wave is λ. The above elastic wave device solves the problem of large high-order strays in high-frequency elastic wave devices with elastic wave speed higher than surface acoustic waves in the prior art, and while suppressing the high-order strays of the elastic wave device, the electromechanical coupling coefficient and quality factor of the elastic wave device are improved.

[0023] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0025] Figure 1 is a cross-sectional view of an elastic wave device according to an embodiment of the present application;

[0026] Figure 2 A characteristic curve diagram of the change of the Euler angle of the piezoelectric layer of the elastic wave device of one embodiment of the present application, the constituent material of which is lithium niobate;

[0027] Figure 3 and Figure 4 The thickness of the piezoelectric layer of the elastic wave device of one embodiment of the present application is about the thickness of the piezoelectric layer of the material of lithium niobate. Characteristic curve diagram of changes;

[0028] Figure 5 The thickness of the functional layer of the elastic wave device of one embodiment of the present application is about the thickness of the functional layer ... elastic wave device of one embodiment of the present application. Characteristic curve diagram of changes;

[0029] Figure 6 and Figure 7 A characteristic curve diagram of the elastic wave device according to an embodiment of the present application with respect to the change of the metallization ratio MR of the IDT electrode structure;

[0030] Figure 8 is a cross-sectional view of an elastic wave device having a low acoustic velocity layer of the present application;

[0031] Fig. 9 is a characteristic curve diagram of admittance and real part of the elastic wave device of the preferred embodiment;

[0032] Fig.10 It is a cross-sectional view of a module of an elastic wave device according to an embodiment of the present application.

[0033] In the figure: 10, IDT electrode structure; 20, piezoelectric layer; 30, functional layer; 40, support layer; 50, low acoustic velocity layer; 600, elastic wave device; 700, inductor; 800, wiring substrate; 900, sealing part; 801, IC integrated circuit component; 802, connecting terminal. DETAILED DESCRIPTION

[0034] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0035] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with general skills in the technical field to which this application belongs. The words "one", "a", "the", "these" and the like in this application do not indicate a quantitative limitation, and they may be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone. Generally, the character " / " indicates that the objects associated with each other are in an "or" relationship. The terms "first", "second", "third", etc. in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0036] The following is based on Figures 1 to 10 , the elastic wave device and module of the present application are described.

[0037] Figure 1 is a cross-sectional view of an elastic wave device according to an embodiment of the present application, Figure 1 As shown, the elastic wave device includes a support layer 40, a functional layer 30, a piezoelectric layer 20 and an IDT electrode structure 10 from bottom to top, wherein the IDT electrode structure 10 is arranged on the upper surface of the piezoelectric layer 20; the piezoelectric layer 20 is stacked on the upper part of the functional layer; the functional layer 30 is stacked on the upper part of the support layer 40; wherein the IDT electrode structure 10 and the piezoelectric layer 20 are used to excite elastic waves with a speed higher than 6000m / s, and the wavelength of the elastic waves is λ; the interval between the anti-resonance frequency of the elastic wave and the cut-off frequency of the support layer is 550MHz~1000MHz.

[0038] Specifically, the support layer 40 is preferably a rectangular plate-shaped structure with a flat surface, and its constituent materials include sapphire, silicon, aluminum oxide, spinel, silicon nitride, aluminum nitride, silicon carbide, silicon oxynitride, diamond, crystal or glass; and the thermal expansion coefficient (CTE) of the support layer 40 is preferably a material that matches the piezoelectric layer 20 and the IDT electrode structure 10 to avoid frequency drift caused by temperature changes and ensure the stability of the elastic device. The constituent materials of the piezoelectric layer 20 include lithium niobate or lithium tantalate, and its positive / reverse piezoelectric effect can realize the conversion between electrical energy and mechanical energy (sound waves). By selecting appropriate piezoelectric materials, the quality factor Q value and electromechanical coupling coefficient of the elastic wave device can be guaranteed. , to ensure the frequency response performance of the elastic wave device. The functional layer 30 is used to limit the leakage of the main mode energy to improve the electromechanical coupling coefficient and quality factor of the resonator. The IDT electrode structure 10 is composed of two groups of staggered interdigitated electrodes, and its constituent material includes at least one of aluminum, copper, silver, titanium, platinum or gold. The IDT electrode structure 10 applies a transverse electric field on the surface of the piezoelectric layer 20 to excite and receive sound waves.

[0039] It should be noted that the acoustic velocity of the elastic wave excited by the piezoelectric layer and the IDT electrode structure 20 of the elastic wave device of this embodiment is higher than 6000m / s, so that the elastic wave device can be applied to the high frequency band; by adjusting the thickness of the functional layer, the spacing between the anti-resonance frequency of the elastic wave and the cut-off frequency of the support layer is 550MHz~1000MHz, which suppresses the spurious of the elastic wave device near the passband. Among them, the above-mentioned main mode elastic wave is preferably a symmetrical S0 Lamb wave.

[0040] The speed of the main mode elastic wave excited by the elastic wave device of this embodiment is higher than the speed of sound of the surface acoustic wave formed by the traditional surface acoustic wave resonator, such as Rayleigh wave and shear wave. Therefore, compared with the traditional surface acoustic wave resonator, the elastic wave device of this embodiment has a higher operating frequency and a larger bandwidth, thereby solving the problem that the SAW resonator of the prior art is difficult to meet high-frequency applications, and improving the high-frequency characteristics and bandwidth performance of the elastic wave device. Furthermore, the elastic wave device of this embodiment solves the problem of large stray in the high-frequency elastic wave device in the prior art where the main mode elastic wave speed is higher than the surface acoustic wave through the functional layer, and while suppressing the high-order stray of the elastic wave device, it improves the electromechanical coupling coefficient and quality factor of the elastic wave device.

[0041] In some of the embodiments, the constituent material of the piezoelectric layer 20 is lithium niobate or lithium tantalate; the thickness range of the piezoelectric layer 20 is 0.1λ~0.25λ; the piezoelectric layer 20 has a crystal cutting direction of Euler angles of (40°±15°, 90°±15°, -90°±15°), and the elastic wave mode used to excite is an elastic wave of a symmetric S0 Lamb wave.

[0042] Specifically, the material, thickness and cutting direction of the piezoelectric layer 10 determine the piezoelectric properties of the piezoelectric layer 10. The main mode of the acoustic wave excited by the piezoelectric layer and the IDT electrode structure 20 of the elastic wave device of this embodiment is specifically a symmetric S0 Lamb wave mode (SymmetricLambwavemode, S0) mode. Specifically, the above-mentioned symmetric S0 Lamb wave is formed by the transverse electric field applied by the IDT electrode structure 10 on the surface of the piezoelectric layer 20. For the elastic wave device of this embodiment, the clutter mode is an antisymmetric Lamb wave (Antisymmetric modes, A-mode) formed by the longitudinal electric field, and high-order clutter.

[0043] Figure 2 The characteristic curve diagram of the change of the Euler angle of the piezoelectric layer of the elastic wave device of one embodiment of the present application is as follows: Figure 2 As shown, the abscissa is the angle of cutting the piezoelectric layer X, the ordinate is the electromechanical coupling coefficient, the red solid line is the characteristic curve of the elastic wave device whose main mode elastic wave is the symmetric S0 Lamb wave, and the black solid line is the characteristic curve of the elastic wave device whose main mode is the transverse shear wave. When the angle range of cutting the piezoelectric layer X is between 25° and 55°, the electromechanical coupling coefficient of the elastic wave device whose main mode elastic wave is the symmetric S0 Lamb wave is above 18%, and is much larger than the electromechanical coupling coefficient of the elastic wave device whose main mode is the transverse shear wave. Figure 3 and Figure 4 The thickness of the piezoelectric layer of the elastic wave device of one embodiment of the present application is about the thickness of the piezoelectric layer of the material of lithium niobate. The characteristic curve of the change, such as Figure 3As shown, the blue dotted line is the thickness of the piezoelectric layer 20 The characteristic curve when λ is 0.1λ; the black dotted line is the thickness of the piezoelectric layer 20 Characteristic curve when λ is 0.15λ; the red solid line is the thickness of the piezoelectric layer 20 Characteristic curve when λ is 0.2λ; the blue solid line is the thickness of the piezoelectric layer 20 Characteristic curve when λ is 0.25λ; the green solid line is the thickness of the piezoelectric layer 20 The characteristic curve when the value is 0.3λ, Figure 3 Medium thickness The spurious frequency bands of elastic wave devices in the range of 0.1λ~0.3λ are all outside the passband of the main mode elastic wave, and the thickness Elastic wave devices in the range of 0.1λ~0.25λ have smaller stray and better thickness The range is between 0.1λ and 0.2λ. Figure 4 As shown, the red solid line is the thickness of the piezoelectric layer 20 Electromechanical coupling coefficient Function curve of thickness The electromechanical coupling coefficient is between 0.1λ and 0.25λ. is proportional to, and both are above 18%. When the electromechanical coupling coefficient is between 0.125λ and 0.25λ, are all above 20%; the blue solid line is the thickness of the piezoelectric layer 20 The function curve of the velocity of the main mode elastic wave is When the range is between 0.1λ and 0.25λ, the speed of elastic waves All above 6400m / s.

[0044] In summary, the main mode elastic wave excited by the elastic wave device of this embodiment is a symmetrical S0 Lamb wave, and it is necessary to select an elastic wave device whose constituent material is lithium niobate, whose thickness range is 0.1λ~0.25λ (preferably, whose thickness range is 0.125λ~0.2λ), and whose Euler angle range is (40°±15°, 90°±15°, -90°±15°). By setting the piezoelectric layer 10 within the above structural parameter range, the elastic wave device can excite a larger electromechanical coupling coefficient and a symmetrical S0 Lamb wave mode with a speed greater than 6000m / s, while suppressing the clutter near the passband of the elastic wave device.

[0045] In some embodiments, the acoustic impedance of the material constituting the functional layer 30 is greater than 3.1 kg / .

[0046] Specifically, the acoustic impedance value is selected to be greater than 3.1 kg / The material is used as the constituent material, so that the elastic wave energy decays slowly in the functional layer 30, and the energy loss of the elastic wave is small when propagating in the functional layer 30, thereby improving the electromechanical coupling coefficient and quality factor of the elastic wave device. According to the above acoustic impedance value range, silicon carbide and diamond can be selected as the constituent material of the functional layer 30; in addition, the high acoustic impedance characteristics of the functional layer 30 can limit the downward leakage of the main mode energy. Therefore, the functional layer 30 can improve the electromechanical coupling coefficient and power capacity of the elastic wave device.

[0047] In some embodiments, when the functional layer 30 is made of silicon carbide, the thickness of the functional layer 30 is in the range of 0.4λ to 1.4λ.

[0048] When the constituent material of the functional layer 30 is diamond, the thickness of the functional layer is in the range of 0.3λ to 1.2λ.

[0049] Specifically, Figure 5 The thickness of the functional layer of the elastic wave device of one embodiment of the present application is about the thickness of the functional layer ... elastic wave device of one embodiment of the present application. The characteristic diagram of the change, Figure 5 In the upper half of the figure, there are two groups of lines, dark and light. The dark lines are the characteristic curves of the absolute value of the admittance of the elastic wave device changing with the frequency; the light lines are the characteristic curves of the real part of the admittance of the elastic wave device changing with the frequency. Figure 5 As shown, the constituent material of the functional layer 30 is silicon carbide, wherein the blue dotted line is the characteristic curve of the functional layer 30 with a thickness of 0.2λ; the green dotted line is the characteristic curve of the functional layer 30 with a thickness of 0.4λ; the dark yellow dotted line is the characteristic curve of the functional layer 30 with a thickness of 0.8λ; the red solid line is the characteristic curve of the functional layer 30 with a thickness of 1λ; the light blue dotted line is the characteristic curve of the functional layer 30 with a thickness of 1.4λ; the black dotted line is the characteristic curve of the functional layer 30 with a thickness of 3λ; when the thickness of the functional layer 30 is 0.2λ, that is, when the thickness of the functional layer 30 is less than 0.4λ, the anti-resonance frequency of the elastic wave device is about 3400MHz, the cutoff frequency of the support layer 40 is about 3900MHz, and the distance between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer 40 is about 500MHz. When the distance between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer is small, the energy of the main mode and the high-order strays leaks toward the support layer, resulting in the quality factor of the elastic wave device ( Figure 5 The BodeQ value is low.

[0050] As the thickness of the functional layer 30 increases, when the thickness of the functional layer is in the range of 0.4λ to 1.4λ, the anti-resonance frequency of the passband of the elastic wave device is about 3400MHz, the cutoff frequency of the support layer 40 moves to the right and gradually moves away from the anti-resonance frequency of the passband of the main mode, and the energy leakage of the main mode and high-order spurious toward the support layer is gradually suppressed, so the Q value of the main mode and high-order spurious gradually increases. Specifically, when the thickness of the functional layer 30 is 0.4λ, the cutoff frequency of the support layer 40 is about 4050MHz, and the distance between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer 40 is about 550MHz; .... When the thickness of the functional layer 30 is 0.8λ, the cutoff frequency of the support layer 40 is about 4200MHz, and the distance between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer 40 is about 700MHz; when the thickness of the functional layer 30 is 1λ and 1.4λ, the cutoff frequency of the support layer 40 is about 4300MHz, and the distance between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer 40 is 900MHz. At this time, the quality factor of the elastic wave of the main mode of the elastic wave device is large, and the quality factor of the high-order spurious of the elastic wave device is small relative to the quality factor of the main mode of the elastic wave, achieving a high quality factor of the elastic wave device while suppressing the high-order spurious. When the thickness of the functional layer 30 is 3λ, the cutoff frequency of the support layer 40 is on the right side of the high-order spurious. Although the quality factor of the elastic wave of the main mode of the elastic wave device increases slightly, the quality factor of its high-order spurious is also higher than that of the main mode of the elastic wave. At this time, the high-order spurious has a greater impact on the performance of the elastic wave device.

[0051] In summary, when all structures except the functional layer are the same, the elastic wave device of the present application adjusts the thickness of the functional layer 30 to 0.4λ~1.4λ according to the constituent material of the functional layer 30, so as to adjust the cutoff frequency of the support layer 40 accordingly, so that the spacing between the anti-resonance frequency of the elastic wave and the cutoff frequency of the support layer 40 is 550MHz~1000MHz, so that the high-order clutter leaks toward the substrate direction to suppress the high-order clutter. It should be noted that the spacing between the anti-resonance frequency and the cutoff frequency of the elastic wave excited by the elastic wave device of the present application is more preferably 550MHz~900MHz. And because the hardness of silicon carbide and diamond is relatively high, it is easier to cut when the thickness of the functional layer 30 is adjusted to the above target thickness range.

[0052] In some of the embodiments, when the thickness of the IDT electrode structure 10 is in the range of 0.02λ to 0.1λ, mass load and transverse electric field excitation can be provided, and the symmetric S0 Lamb wave mode mentioned above can be excited by applying a transverse electric field on the surface of the piezoelectric layer 20 .

[0053] In some embodiments, the metallization ratio of the IDT electrode structure 10 is in a range of 0.2-0.7.

[0054] Specifically, the above-mentioned metallization ratio is specifically the ratio of the electrode finger width in the IDT electrode structure 10 to the length of an electrode period (pitch), wherein the above-mentioned electrode period is the sum of the width of a single electrode finger and the spacing between adjacent electrode fingers. The metallization ratio affects the input impedance of the elastic wave device. By adjusting the metallization ratio of the elastic wave device, the optimal impedance matching can be achieved, thereby improving the efficiency of signal transmission; and because the metallization ratio is related to the physical size of the electrode, the metallization ratio will also affect the operating frequency of the device. A narrower electrode width and gap between electrodes can support a higher operating frequency. Figure 6 and Figure 7 This is a simulation diagram of the change in the metallization ratio MR of the IDT electrode structure of the elastic wave device according to one embodiment of the present application. Figure 6 As shown, the light blue dotted line is when the metallization ratio of the IDT electrode structure is 0.1, its electromechanical coupling coefficient is 18.4%, and the passband of the main mode is 3250MHz~3520MHz; the black dotted line is when the metallization ratio of the IDT electrode structure is 0.2, its electromechanical coupling coefficient is 20.06%, and the passband of the main mode is 3250MHz~3475MHz; the red solid line is when the metallization ratio of the IDT electrode structure is 0.4, its electromechanical coupling coefficient is 22.9%, and the passband of the main mode is 3050MHz~33 70MHz; the yellow dotted line is when the metallization ratio of the IDT electrode structure is 0.7, its electromechanical coupling coefficient is 20.95%, and the passband of the main mode is 3250MHz~3325MHz; the blue dotted line is when the metallization ratio of the IDT electrode structure is 0.8, its electromechanical coupling coefficient is 18.4%, and the passband of the main mode is 3000MHz~3260MHz. Therefore, when the metallization ratio is 0.2~0.7, its electromechanical coupling coefficient and passband are higher than those of elastic wave devices with metallization ratios of 0.1 and 0.8. Figure 7 As shown in the figure, the red solid line is the function curve of the metallization ratio MR of the IDT electrode structure and the electromechanical coupling coefficient. When the metallization ratio ranges from 0.2 to 0.7, the electromechanical coupling coefficient of the elastic wave device is above 20%; the blue solid line is the metallization ratio of the IDT electrode structure and the main mode sound velocity Function curve, when the metallization ratio is in the range of 0.1~0.9, the sound velocity All above 6200m / s.

[0055] In summary, when the elastic wave device has the same structure except the metallization ratio of the IDT electrode structure 10 , and the metallization ratio of the IDT electrode structure 10 is in the range of 0.2 to 0.7, the elastic wave device has a higher electromechanical coupling coefficient and a higher acoustic velocity.

[0056] In some of the embodiments, the elastic wave device further includes a low acoustic velocity layer; the low acoustic velocity layer is stacked on the upper part or the lower part of the functional layer 30 .

[0057] Specifically, for elastic waves in the direction perpendicular to the horizontal plane, the sound velocity in the low sound velocity layer is lower than the sound velocity in the piezoelectric layer and the support layer. Figure 8 is a cross-sectional view of an elastic wave device having a low acoustic velocity layer of the present application, such as Figure 8 As shown, by stacking the low acoustic velocity layer 50 and the functional layer 30 , the acoustic wave energy leakage of the main mode can be further limited to improve the electromechanical coupling coefficient and the quality factor of the resonator.

[0058] In some embodiments, the low acoustic velocity layer is made of a material including silicon oxide, gallium arsenide or tantalum oxide; and the thickness of the low acoustic velocity layer is in the range of 0.01λ to 0.4λ.

[0059] Specifically, controlling the thickness of the low acoustic velocity layer to 0.01λ~0.4λ can further limit the energy leakage of the main mode to improve the electromechanical coupling coefficient and quality factor of the resonator; and when the constituent materials of the low acoustic velocity layer include silicon oxide, gallium arsenide or tantalum oxide, since the above materials are positive temperature coefficient materials, they can provide temperature compensation, thereby improving the temperature stability of the elastic wave device.

[0060] In some embodiments, the support layer 40 is made of a material including spinel, sapphire, silicon or quartz.

[0061] Specifically, the above can be used as a low-acoustic-velocity substrate, and by combining the functional layer 20, the cutoff frequency of the support layer 40 can be adjusted so that the cutoff frequency is between the main mode acoustic wave frequency and the high-order clutter frequency, so that the high-order clutter leaks toward the support layer 40, thereby achieving the suppression of the high-order clutter. And when the constituent material of the support layer 40 includes spinel, sapphire or quartz, since the above materials are positive temperature coefficient materials, using the above material substrate as the support layer 40 can provide temperature compensation for the elastic wave device, thereby improving the temperature stability of the resonator; it should be noted that in other embodiments, the support layer can be made by stacking a polycrystalline material on a single crystal material with a positive temperature coefficient.

[0062] The elastic wave device of the present application is described below through preferred embodiments.

[0063] The elastic wave device of this preferred embodiment includes a supporting layer 40, a low acoustic velocity layer 50, a functional layer 30, a piezoelectric layer 20 and an IDT electrode structure 10, wherein the IDT electrode structure 10 is arranged on the upper surface of the piezoelectric layer 20; the piezoelectric layer 20 is stacked on the upper part of the functional layer; the functional layer 30 is stacked on the upper part of the low acoustic velocity layer 50, and the low acoustic velocity layer 50 is stacked on the upper part of the supporting layer 40; the mode of the elastic wave excited by the IDT electrode structure 10 and the piezoelectric layer 20 is a symmetrical S0 Lamb wave, wherein the wavelength of the symmetrical S0 Lamb wave is λ; the interval between the antiresonance frequency and the cutoff frequency of the above-mentioned elastic wave is 550MHz~900MHz.

[0064] Among them, the constituent material of the piezoelectric layer 20 is lithium niobate, the thickness range of the piezoelectric layer 20 is 0.1λ~0.25λ, and the piezoelectric layer 20 has a crystal cutting direction of the Euler angle of (40°±15°, 90°±15°, -90°±15°); the constituent material of the functional layer 30 is silicon carbide, and its thickness range is 0.4λ~1.4λ; the thickness range of the IDT electrode structure 10 is 0.02λ~0.1λ; the metallization ratio of the IDT electrode structure 10 ranges from 0.2~0.7; the constituent material of the low acoustic velocity layer 50 is silicon oxide, and its thickness range is 0.01λ~0.4λ; the constituent material of the above-mentioned support layer 40 is spinel.

[0065] Fig. 9 FIG. 2 is a graph showing the admittance and real part characteristics of the elastic wave device of the preferred embodiment. Fig. 9 As shown, the black solid line is the characteristic curve of the absolute value of the admittance of the elastic wave device of this preferred embodiment changing with the frequency; the red dotted line is the characteristic curve of the real part of the admittance of the elastic wave device of this preferred embodiment changing with the frequency. Fig. 9 It can be seen from the figure that the stray electric field excitation in the elastic wave device of the preferred embodiment is suppressed, and the electromechanical coupling coefficient of the elastic wave device is The elastic wave device of this preferred embodiment is excited by both the transverse electric field and the longitudinal electric field to form a symmetrical S0 Lamb wave. Since the piezoelectric coefficient component related to the transverse electric field is much larger than the piezoelectric coefficient component related to the longitudinal electric field, the electromechanical coupling coefficient There is no significant drop due to the interference of the longitudinal electric field, and the purpose of suppressing spurious modes is achieved.

[0066] The elastic wave device of this preferred embodiment solves the problem that when the main mode elastic wave is a symmetrical S0 Lamb wave, the high-order stray waves of the elastic wave device are large due to its obvious dispersion characteristics. While suppressing the high-order stray waves, the electromechanical coupling coefficient and quality factor of the elastic wave device are improved.

[0067] Fig.10is a cross-sectional view of a module of an elastic wave device according to an embodiment of the present application, Fig.10 As shown, the module of the elastic wave device includes an elastic wave device 600, an inductor 700, a sealing part 900, a wiring substrate 800, an IC integrated circuit component 801 and a connecting terminal 802. The connecting terminal 802 is formed on the lower surface of the wiring substrate 800 and is connected to the external circuit main board; the IC integrated circuit component 801 is installed inside the wiring substrate 800, and the IC integrated circuit component 801 includes a switching circuit and a low-noise amplifier. The inductor 700 is installed on the main surface of the wiring substrate 800 to achieve impedance matching of the signal transmission circuit. It should be noted that in other embodiments, the inductor 700 can also be other passive components. The above-mentioned sealing part 900 is used to seal the elastic wave device 600 and the inductor 700 and other devices.

[0068] The expressions and terms used in the present invention are for illustrative purposes only and should not be considered as limiting. The use of "include", "have", "have", "include" and their variations as used herein means including the following listed items and their equivalents and additional items.

[0069] The term "embodiment" in this application refers to a specific feature, structure or characteristic described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. It is clearly or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.

[0070] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations, corrections and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. An elastic wave device, comprising, from bottom to top, a support layer, a functional layer, a piezoelectric layer and an IDT electrode structure, characterized in that: The IDT electrode structure is arranged on the upper surface of the piezoelectric layer; the piezoelectric layer is stacked on the upper part of the functional layer; the functional layer is stacked on the upper part of the supporting layer; The IDT electrode structure and the piezoelectric layer are used to excite elastic waves with a sound velocity higher than 6000 m / s, and the wavelength of the elastic wave is λ; the acoustic impedance value of the constituent material of the functional layer is greater than 3.1×10 7 kg / m 2 ·s; when the constituent material of the functional layer is silicon carbide, the thickness of the functional layer ranges from 0.4λ to 1.4λ; when the constituent material of the functional layer is diamond, the thickness of the functional layer ranges from 0.3λ to 1.2λ.

2. The elastic wave device according to claim 1, characterized in that: The constituent material of the piezoelectric layer is lithium niobate or lithium tantalate; The thickness of the piezoelectric layer ranges from 0.1λ to 0.25λ; The piezoelectric layer has a crystal cutting direction of Euler angles of (40°±15°, 90°±15°, -90°±15°), and the mode of the elastic wave used for excitation is a symmetrical S0 Lamb wave.

3. The elastic wave device according to claim 1, characterized in that: The thickness of the IDT electrode structure ranges from 0.02λ to 0.1λ.

4. The elastic wave device according to claim 1, characterized in that: The metallization ratio of the IDT electrode structure is in the range of 0.2-0.

7.

5. The elastic wave device according to claim 1, characterized in that: The elastic wave device further includes a low acoustic velocity layer; the low acoustic velocity layer is stacked on the upper part or the lower part of the functional layer.

6. The elastic wave device according to claim 5, characterized in that The low acoustic velocity layer is made of a material including silicon oxide, gallium arsenide or tantalum oxide; The thickness of the low sound velocity layer ranges from 0.01λ to 0.4λ.

7. The elastic wave device according to claim 1, characterized in that: The supporting layer is made of spinel, sapphire, silicon or quartz.

8. A module comprising a plurality of elastic wave devices according to any one of claims 1 to 7.

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