Surface acoustic wave device, radio frequency front-end module and electronic equipment

Abstract

The invention relates to the technical field of resonators, in particular to a surface acoustic wave device, a radio frequency front-end module and electronic equipment, the surface acoustic wave device comprises a piezoelectric substrate, and the piezoelectric substrate comprises a dielectric layer and a piezoelectric layer arranged on one side of the dielectric layer; the IDT electrode is arranged on one side, far away from the dielectric layer, of the piezoelectric layer; by selecting the proper dielectric layer and piezoelectric layer, the ratio of the speed of the body wave propagating in the dielectric layer to the speed of the body wave propagating in the piezoelectric layer is less than 0.95, and the body wave is easier to transmit to the lower part of the piezoelectric layer, so that the formation of a high-order mode is inhibited to a certain extent, the adverse effect of the high-order mode on the propagation of the surface acoustic wave is favorably reduced, and the transmission efficiency of the surface acoustic wave is improved. And the performance of the surface acoustic wave device can be improved.

Description

Technical Field

[0001] The present application relates to the field of resonator technology, and in particular to a surface acoustic wave device, a radio frequency front-end module and an electronic device. Background Art

[0002] At present, surface acoustic wave devices use the piezoelectric effect to achieve electric-acoustic-electric transduction. The IDT electrode located on the piezoelectric layer excites the electrical signal to form a surface acoustic wave (SAW) that propagates on the surface of the piezoelectric layer. Surface acoustic wave devices have advantages such as small structural size. Through the series and parallel connection of surface acoustic wave devices, RF filters with low insertion loss and high rectangular coefficient can be realized, which are widely used in communication devices such as smart phones.

[0003] In a surface acoustic wave device, within the main mode frequency range, the acoustic wave propagates in the form of a surface acoustic wave; within the high frequency range outside the main mode frequency range, the acoustic wave propagates in the form of a body wave. The surface acoustic wave in the main mode propagates in the width direction of the electrode finger in the IDT electrode; the body wave in the high frequency mode propagates downward along the thickness direction of the piezoelectric layer, and the body wave is reflected back to the piezoelectric layer on the lower surface of the piezoelectric layer. When the body wave and the reflected wave of the body wave have the same phase and meet the standing wave condition, a high-order mode is formed. The high-order mode has an adverse effect on the propagation of the surface acoustic wave, which is not conducive to improving the performance of the surface acoustic wave device. Therefore, how to suppress the high-order mode has become a technical problem that needs to be solved urgently in the prior art. Summary of the invention

[0004] In view of the above problems, the embodiments of the present application provide a surface acoustic wave device, a radio frequency front-end module and an electronic device to solve the above-mentioned technical problem of how to suppress high-order modes.

[0005] In a first aspect, an embodiment of the present application provides a surface acoustic wave device, comprising:

[0006] A piezoelectric substrate, the piezoelectric substrate comprising a dielectric layer and a piezoelectric layer arranged on one side of the dielectric layer;

[0007] An IDT electrode is arranged on a side of the piezoelectric layer away from the dielectric layer;

[0008] The dielectric layer and the piezoelectric layer are configured such that a ratio of a velocity of a body wave propagating in the dielectric layer to a velocity of a body wave propagating in the piezoelectric layer is less than 0.95.

[0009] In a second aspect, an embodiment of the present application provides a surface acoustic wave device, including:

[0010] A piezoelectric substrate, the piezoelectric substrate comprising a substrate and a piezoelectric layer disposed on one side of the substrate;

[0011] An IDT electrode is arranged on a side of the piezoelectric layer away from the substrate;

[0012] The substrate and the piezoelectric layer are configured as follows:

[0013] The ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is less than 0.933; and / or the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer is less than 1.6;

[0014] A first angle between a propagation direction of a body wave propagating in the piezoelectric layer and a normal to a direction in which a surface of the piezoelectric layer is located is less than 15°.

[0015] In a third aspect, an embodiment of the present application provides a surface acoustic wave device, including:

[0016] A piezoelectric substrate, the piezoelectric substrate comprising a substrate, a dielectric layer disposed on one side of the substrate, and a piezoelectric layer disposed on a side of the dielectric layer away from the substrate;

[0017] An IDT electrode is arranged on a side of the piezoelectric layer away from the substrate;

[0018] The dielectric layer and the piezoelectric layer are configured such that a ratio of a velocity of a longitudinal wave component of a body wave propagating in the dielectric layer to a velocity of a longitudinal wave component of a body wave propagating in the piezoelectric layer is less than 0.95;

[0019] The dielectric layer and the substrate are configured such that a ratio of a velocity of a longitudinal wave component of a body wave propagating in the dielectric layer to a velocity of a longitudinal wave component of a body wave propagating in the substrate is less than 0.615;

[0020] A first angle between a propagation direction of a body wave propagating in the piezoelectric layer and a normal to a surface of the piezoelectric layer is less than 15°, and a second angle between a propagation direction of a body wave propagating in the dielectric layer and a normal to a surface of the dielectric layer is less than 20°.

[0021] In a fourth aspect, an embodiment of the present application provides a radio frequency front-end module, wherein the radio frequency front-end module includes the above-mentioned surface acoustic wave device.

[0022] In a fifth aspect, an embodiment of the present application provides an electronic device, which includes the above-mentioned radio frequency front-end module.

[0023] The surface acoustic wave device, radio frequency front-end module and electronic device provided in the embodiments of the present application include a piezoelectric substrate, wherein the piezoelectric substrate includes a dielectric layer and a piezoelectric layer arranged on one side of the dielectric layer; an IDT electrode is arranged on the side of the piezoelectric layer away from the dielectric layer; by selecting a suitable dielectric layer and piezoelectric layer, the ratio of the speed of the body wave propagating in the dielectric layer to the speed of the body wave propagating in the piezoelectric layer is less than 0.95, so that the body wave is more easily transmitted to the bottom of the piezoelectric layer, thereby suppressing the formation of high-order modes to a certain extent, which is beneficial to reducing the adverse effects of high-order modes on the propagation of surface acoustic waves and is beneficial to improving the performance of surface acoustic wave devices.

[0024] These and other aspects of the present application will become more clearly understood in the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic structural diagram of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0026] Figure 2 A schematic diagram of body wave reflection of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0027] Figure 3 Shows Figure 1 An example diagram of a frequency curve of a surface acoustic wave device shown;

[0028] Figure 4 A diagram showing the bulk wave transmission relationship between the piezoelectric layer and the dielectric layer in a surface acoustic wave device provided by an embodiment of the present application is shown;

[0029] Figure 5 A schematic structural diagram of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0030] Figure 6 A schematic structural diagram of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0031] Figure 7 A schematic structural diagram of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0032] Figure 8 A frequency curve comparison diagram of different body wave velocities of the piezoelectric layer and the dielectric layer in the surface acoustic wave device provided by an embodiment of the present application is shown;

[0033] Fig. 9 A schematic structural diagram of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0034] Fig.10 A schematic structural diagram of a surface acoustic wave device provided by an embodiment of the present application is shown;

[0035] Fig.11 A schematic diagram of the structure of a radio frequency front-end module provided in an embodiment of the present application is shown;

[0036] Fig.12 A schematic structural diagram of an electronic device provided in one embodiment of the present application is shown. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0038] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0039] In the embodiments of the present application, it should be noted that, in this article, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0040] Moreover, the terms "comprises," "comprising," or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0041] In the description of the embodiments of the present application, words such as "example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "example" or "for example" in the embodiments of the present application is not to be interpreted as being more preferred or having more advantages than another embodiment or design. The use of words such as "example" or "for example" is intended to present relative concepts in a clear manner.

[0042] In addition, the "plurality" in the embodiments of the present application refers to two or more than two. In view of this, in the embodiments of the present application, "plurality" can also be understood as "at least two". "At least one" can be understood as one or more, for example, one, two or more. For example, including at least one means including one, two or more, and there is no limit on which ones are included. For example, including at least one of A, B and C, then A, B, C, A and B, A and C, B and C, or A, B and C can be included.

[0043] It should be noted that in the embodiments of the present application, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0044] An embodiment of the present application provides a surface acoustic wave device. Figure 1 As shown, the surface acoustic wave device 100 includes a piezoelectric substrate 10 and an IDT (Inter Digital Transducer) electrode 20. The piezoelectric substrate includes a piezoelectric layer 11 and a dielectric layer 12. The piezoelectric layer 11 is arranged on one side of the dielectric layer 12, and the IDT electrode 20 is arranged on the side of the piezoelectric layer 11 away from the dielectric layer 12.

[0045] When the surface acoustic wave device excites an electrical signal through the IDT electrode 20 located on the piezoelectric layer 11, a surface acoustic wave and a bulk wave are simultaneously formed. The dielectric layer 12 and the piezoelectric layer 11 are configured such that the ratio of the velocity of the bulk wave propagating in the dielectric layer 12 to the velocity of the bulk wave propagating in the piezoelectric layer 11 is less than 0.95.

[0046] In this embodiment, by selecting a suitable dielectric layer and piezoelectric layer, the ratio of the velocity of the body wave propagating in the dielectric layer to the velocity of the body wave propagating in the piezoelectric layer is made less than 0.95, so that the body wave can be more easily transmitted to the bottom of the piezoelectric layer, thereby suppressing the formation of high-order modes to a certain extent, which is beneficial to reducing the adverse effects of high-order modes on the propagation of surface acoustic waves and improving the performance of surface acoustic wave devices.

[0047] Please continue reading Figure 2 As shown, the body wave propagating in the piezoelectric layer 11 is reflected back to the piezoelectric layer 11 at the interface between the piezoelectric layer 11 and the dielectric layer 12. If the body wave and the reflected wave of the body wave are in phase, a high-order mode resonance can be formed when the standing wave condition is met.

[0048] Assume that the thickness of the piezoelectric layer 11 is T1 and the wavelength of the body wave in the piezoelectric layer 11 is λ g , considering the half-wave loss during reflection, the incident angle of the body wave in the piezoelectric layer 11 is θ1, and the velocity of the body wave in the piezoelectric layer 11 is v1, then the condition for forming a high-order mode is:

[0049]

[0050] The high-order mode at this time corresponds to a high-order mode frequency, assuming that the high-order mode frequency is f g , then λ g *f g =v1. In order to ensure sufficient acoustic wave excitation efficiency and reduce energy dissipation, the thickness of the piezoelectric layer 11 is often not too large; and in order to make the frequency of the higher-order mode as far away as possible from the resonant frequency of the main mode formed by the surface acoustic wave, and greater than the downward transmission frequency of the body wave (the cut-off frequency of the body wave), according to the above formula, the thickness of the piezoelectric layer 11 cannot be too small. As an embodiment, the thickness of the piezoelectric layer 11 is 0.2λ~0.5λ, where λ is the wavelength of the surface acoustic wave excited by the IDT electrode 20. The electrical signal within the fundamental frequency range excites the formation of the surface acoustic wave, and the high-frequency electrical signal with a frequency greater than the fundamental frequency excites the formation of the body wave. Therefore, the frequency of the higher-order mode is greater than the frequency of the main mode. For example, Figure 1 For example, the frequency curve of the surface acoustic wave device shown in FIG. 1 is shown in FIG. 1 , if the ratio of the velocity of the body wave propagating in the dielectric layer 12 to the velocity of the body wave propagating in the piezoelectric layer 11 is not controlled. Figure 3 The curve L shown 01 , i.e. at 1.3f r ~1.5f r A high-order mode is formed at the position, and the frequency of the high-order mode is recorded as f g , where f r By selecting appropriate dielectric layers and piezoelectric layers, the ratio of the velocity of the body wave propagating in the dielectric layer to the velocity of the body wave propagating in the piezoelectric layer is less than 0.95, which can suppress the frequency at 1.3f to a certain extent. r ~1.5f r The formation of higher-order modes within, such as Figure 3 The curve L shown 02 .

[0051] As an implementation, please continue to see Figure 1 As shown, the first angle θ1 between the propagation direction S11a of the body wave propagating in the piezoelectric layer 11 and the normal line S11b in the direction of the surface of the piezoelectric layer 11 is less than 15°. The normal line S11b is parallel to the stacking direction of the piezoelectric layer 11 and the dielectric layer 12. For example, the first angle θ1 is 14°, 10°, 8°, 5°, 1°, etc., which is not specifically limited in this application.

[0052] In this embodiment, the body wave whose first angle θ1 between the propagation direction S11a and the normal line S11b is less than 15° occupies most of the energy in the piezoelectric layer 11. By selecting the piezoelectric layer 11 and the dielectric layer 12, the body wave that occupies most of the energy is transmitted to the bottom of the piezoelectric layer 11, which is beneficial to further improve the suppression effect of high-order modes.

[0053] The body wave (with a speed of v1) propagating in the piezoelectric layer 11 includes a longitudinal wave component and two transverse wave components. The two transverse wave components are a fast transverse wave component and a slow transverse wave component. The propagation speed of the longitudinal wave component is greater than that of the fast transverse wave component, and the propagation speed of the fast transverse wave component is greater than that of the slow transverse wave component.

[0054] The body wave (with a velocity of v2) propagating in the dielectric layer 12 formed of the anisotropic material includes a longitudinal wave component and two transverse wave components. The two transverse wave components are a fast transverse wave component and a slow transverse wave component. The propagation velocity of the longitudinal wave component is greater than the propagation velocity of the fast transverse wave component, and the propagation velocity of the fast transverse wave component is greater than the propagation velocity of the slow transverse wave component.

[0055] The body wave (with a velocity of v2) propagating in the dielectric layer 12 formed of the isotropic material includes a longitudinal wave component and a transverse wave component, and the propagation velocity of the longitudinal wave component is greater than the propagation velocity of the transverse wave component.

[0056] The body wave propagating in the dielectric layer 12 is formed by the transmission conversion of the body wave in the piezoelectric layer 11. The first angle θ1 between the propagation direction S11a of the body wave propagating in the piezoelectric layer 11 and the normal line S11b in the direction of the surface of the piezoelectric layer 11 is the incident angle, and the second angle θ2 between the propagation direction S12a of the body wave propagating in the dielectric layer 12 and the normal line S12b in the direction of the surface of the dielectric layer 12 is the transmission angle. The speed of the body wave propagating in the piezoelectric layer 11 is v1, and the speed of the body wave propagating in the dielectric layer 12 is v2. Therefore, the acoustic wave transmission model at the interface between the piezoelectric layer 11 and the dielectric layer 12 is:

[0057]

[0058] For example, the material of the piezoelectric layer 11 is lithium tantalate (LiTaO3) with a YX cut of 42° and the material of the dielectric layer 12 is silicon carbide (SiN). Figure 4As shown, according to the above-mentioned sound wave transmission model, curves L1 to L4 are obtained, wherein the horizontal axis is the incident angle θ1 of the body wave in the piezoelectric layer 11, curve L1 is the change curve of the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11, curve L2 is the change curve of the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the fast transverse wave component of the body wave propagating in the piezoelectric layer 11, curve L3 is the change curve of the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the slow transverse wave component of the body wave propagating in the piezoelectric layer 11, and curve L4 is the total reflection line. Figure 4 It can be seen that among the curves L1 to L3, the portion located above the curve L4 is totally reflected, and the portion located below the curve L4 is not totally reflected. According to the curve L1, it can be seen that the higher the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11, the more the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is totally reflected, and the less it is transmitted; according to the curve L2, it can be seen that the higher the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the fast shear wave component of the body wave propagating in the piezoelectric layer 11, the more the fast shear wave component of the body wave propagating in the piezoelectric layer 11 is totally reflected, and the less it is transmitted; according to the curve L3, it can be seen that the higher the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the slow shear wave component of the body wave propagating in the piezoelectric layer 11, the more the slow shear wave component of the body wave propagating in the piezoelectric layer 11 is totally reflected, and the less it is transmitted.

[0059] As an embodiment, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is less than 0.95.

[0060] In this embodiment, since the longitudinal wave component occupies most of the energy of the body wave, by controlling the speed ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the piezoelectric layer within the above-mentioned range, the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer is increased, which is beneficial to further improve the suppression effect of high-order modes.

[0061] In some embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is less than 0.933.

[0062] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the piezoelectric layer within the above range, the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer can be further increased, which is beneficial to further improve the suppression effect of high-order modes.

[0063] In some preferred embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.73.

[0064] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the dielectric layer and the longitudinal wave component of the piezoelectric layer within the above-mentioned range, while increasing the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer, it is beneficial to increase the body wave velocity in the dielectric layer, without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thereby avoiding the problem of poor proximal out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0065] In some embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the shear wave component of the body wave propagating in the piezoelectric layer 11 is less than 1.6. Exemplarily, the shear wave component of the body wave propagating in the piezoelectric layer 11 may be a fast shear wave component or a slow shear wave component, and preferably, the shear wave component of the body wave propagating in the piezoelectric layer 11 is a slow shear wave component.

[0066] In this embodiment, by controlling the speed ratio of the longitudinal wave component of the dielectric layer to the transverse wave component of the piezoelectric layer within the above-mentioned range, while increasing the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer, it is beneficial to increase the proportion of the transverse wave component of the piezoelectric layer transmitted into the dielectric layer, which is beneficial to further improve the suppression effect of high-order modes.

[0067] In some preferred embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the shear wave component of the body wave propagating in the piezoelectric layer 11 is greater than 1.27. Exemplarily, the shear wave component of the body wave propagating in the piezoelectric layer 11 is a slow shear wave component.

[0068] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the dielectric layer to the transverse wave component of the piezoelectric layer within the above-mentioned range, while increasing the proportion of the transverse wave component of the piezoelectric layer transmitted into the dielectric layer, it is beneficial to increase the body wave velocity in the dielectric layer, without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thereby avoiding the problem of poor proximal out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0069] As an implementation, see Figure 5 As shown, the dielectric layer 12 may be a substrate, and the thickness of the substrate is greater than the thickness of the piezoelectric layer 11 .

[0070] In this embodiment, the bulk wave transmission in the piezoelectric layer is converted to the substrate, which is beneficial to improving the suppression effect of high-order modes.

[0071] In some embodiments, when the dielectric layer 12 is a substrate, the material used for the substrate includes sapphire, single crystal silicon, silicon carbide, gallium nitride, aluminum nitride, silicon nitride or gallium arsenide.

[0072] As an implementation, see Figure 5 As shown, the piezoelectric substrate 10 further includes a substrate 13 , which is disposed on a side of the dielectric layer 12 away from the piezoelectric layer 11 , and a thickness of the substrate 13 is greater than a thickness of the dielectric layer 12 and a thickness of the piezoelectric layer 11 .

[0073] In this embodiment, the bulk wave in the piezoelectric layer is transmitted and converted to the dielectric layer, and then the bulk wave in the dielectric layer is transmitted and converted to the substrate, which is beneficial to improving the suppression effect of high-order modes.

[0074] In some embodiments, the substrate 13 includes single crystal silicon, silicon carbide, gallium nitride, or gallium arsenide, and the dielectric layer includes silicon nitride or aluminum oxide.

[0075] In some embodiments, the dielectric layer 12 may be a high acoustic velocity layer. For example, the high acoustic velocity layer may include silicon nitride or aluminum oxide.

[0076] In some embodiments, see Figure 6 As shown, the second angle θ2 between the propagation direction S12a of the body wave propagating in the dielectric layer 12 and the normal S12b of the surface of the dielectric layer 12 is less than 20°. For example, the second angle θ2 is 19°, 15°, 12°, 10°, 6°, 3°, 1°, etc., which is not specifically limited in this application.

[0077] In this embodiment, the body wave whose second angle θ2 between the propagation direction S12a and the normal line S12b is less than 20° occupies most of the energy in the dielectric layer 12. By selecting the dielectric layer 12 and the substrate 13, the body wave that occupies most of the energy in the dielectric layer 12 is transmitted to the middle and lower part of the dielectric layer 12, which is beneficial to further improve the suppression effect of high-order modes.

[0078] The body wave (with a velocity of v2) propagating in the dielectric layer 12 formed of the anisotropic material includes a longitudinal wave component and two transverse wave components. The two transverse wave components are a fast transverse wave component and a slow transverse wave component. The propagation velocity of the longitudinal wave component is greater than the propagation velocity of the fast transverse wave component, and the propagation velocity of the fast transverse wave component is greater than the propagation velocity of the slow transverse wave component.

[0079] The body wave (with a velocity of v2) propagating in the dielectric layer 12 formed of the isotropic material includes a longitudinal wave component and a transverse wave component, and the propagation velocity of the longitudinal wave component is greater than the propagation velocity of the transverse wave component.

[0080] The body wave (with a speed of v3) propagating in the substrate 13 formed of anisotropic material includes a longitudinal wave component and two transverse wave components. The two transverse wave components are a fast transverse wave component and a slow transverse wave component. The propagation speed of the longitudinal wave component is greater than that of the fast transverse wave component, and the propagation speed of the fast transverse wave component is greater than that of the slow transverse wave component.

[0081] The body wave (with a velocity of v3) propagating in the substrate 13 formed of the isotropic material includes a longitudinal wave component and a transverse wave component, and the propagation velocity of the longitudinal wave component is greater than the propagation velocity of the transverse wave component.

[0082] The body wave propagating in the substrate 13 is formed by the body wave transmission conversion in the dielectric layer 12. The second angle θ2 between the propagation direction S12a of the body wave propagating in the dielectric layer 12 and the normal line S12b in the direction of the surface of the dielectric layer 12 is the incident angle. The third angle θ3 between the propagation direction S13a of the body wave propagating in the substrate 13 and the normal line S13b in the direction of the surface of the substrate 13 is the transmission angle. The speed of the body wave propagating in the dielectric layer 12 is v2, and the speed of the body wave propagating in the substrate 13 is v3. Therefore, the acoustic wave transmission model at the interface between the dielectric layer 12 and the substrate 13 is:

[0083]

[0084] and Figure 4 The curves L1 to L3 shown in the figure are similar. The higher the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 13 to the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12, the more the longitudinal wave component of the body wave propagating in the dielectric layer 12 is totally reflected, and the less it is transmitted. When the dielectric layer 12 is made of anisotropic material, the higher the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 13 to the velocity of the fast shear wave component of the body wave propagating in the dielectric layer 12, the more the fast shear ... When the dielectric layer 12 is made of anisotropic material, the higher the ratio of the speed of the longitudinal wave component of the body wave propagating in the substrate 13 to the speed of the slow transverse wave component of the body wave propagating in the dielectric layer 12, the more the slow transverse wave component of the body wave propagating in the dielectric layer 12 is totally reflected, and the less it is transmitted; when the dielectric layer 12 is made of isotropic material, the higher the ratio of the speed of the longitudinal wave component of the body wave propagating in the substrate 13 to the speed of the transverse wave component of the body wave propagating in the dielectric layer 12, the more the transverse wave component of the body wave propagating in the dielectric layer 12 is totally reflected, and the less it is transmitted.

[0085] In some embodiments, the ratio of the velocity of the longitudinal wave component of the bulk wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the bulk wave propagating in the substrate 13 is less than 0.615.

[0086] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the substrate within the above-mentioned range, it is beneficial to increase the body wave velocity in the substrate without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thereby avoiding the problem of poor near-end out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0087] In some embodiments, the ratio of the velocity of the longitudinal wave component of the bulk wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the bulk wave propagating in the substrate 13 is greater than 0.41.

[0088] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the substrate within the above range, the proportion of the longitudinal wave component of the dielectric layer transmitted into the substrate can be further increased, which is beneficial to further improve the suppression effect of high-order modes.

[0089] In some preferred embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.75.

[0090] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the dielectric layer and the longitudinal wave component of the piezoelectric layer within the above-mentioned range, while increasing the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer, it is beneficial to increase the body wave velocity in the dielectric layer, without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thereby avoiding the problem of poor proximal out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0091] In some preferred embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.73 and less than 0.933; the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer 11 is greater than 1.27 and less than 1.6.

[0092] In this embodiment, by controlling the speed ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the piezoelectric layer and the speed ratio of the longitudinal wave component of the dielectric layer to the transverse wave component of the piezoelectric layer within corresponding ranges, while increasing the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer, it is beneficial to increase the body wave velocity in the dielectric layer, without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thereby avoiding the problem of poor proximal out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0093] As an embodiment, the speed of the body wave propagating in the piezoelectric layer 11 is related to the parameters of the piezoelectric layer 11, and the speed of the longitudinal wave component, the speed of the fast shear wave component and the speed of the slow shear wave component of the body wave propagating in the piezoelectric layer 11 are determined based on the elastic stiffness coefficient of the piezoelectric layer 11, the piezoelectric coefficient of the piezoelectric layer 11, the dielectric constant of the piezoelectric layer 11, the density of the piezoelectric layer 11 and the Euler angle of the piezoelectric layer 11.

[0094] Among them, when the density, elastic stiffness coefficient, piezoelectric coefficient and dielectric constant of the piezoelectric layer 11 are respectively related to the material forming the piezoelectric layer, when the material of the piezoelectric layer 11 is determined, its density, elastic stiffness coefficient, piezoelectric coefficient and dielectric constant are all determined.

[0095] In this embodiment, the speed of the bulk wave propagating in the piezoelectric layer 11 can be controlled by configuring the material of the piezoelectric layer and the Euler angle of the piezoelectric layer.

[0096] In some embodiments, the velocity of the body wave in the piezoelectric layer 11 can be solved according to the matrix form of the Christopher equation. The velocity value of the longitudinal wave component and the velocity value of the transverse wave component of the body wave propagating in the piezoelectric layer 11 are solutions of the following formula (I). There are multiple solutions to formula (I). The longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is the maximum value among the multiple solutions, and the transverse wave component of the body wave propagating in the piezoelectric layer is the minimum value among the multiple solutions.

[0097]

[0098] Among them, Γ jk =c ijkl *l i *l l , Γ j4 =Γ 4j =e kij *l i *l k , Γ 44 =-l i *ε ik *l k , c ijkl is the elastic stiffness coefficient of the piezoelectric layer 11, e kij is the piezoelectric coefficient of the piezoelectric layer 11, ε ik is the dielectric constant of the piezoelectric layer 11, i,j,k,l∈(1,3), l1, l2, l3 are the direction cosines of the tangent angle in the thickness direction of the piezoelectric layer 11, ρ1 is the density of the piezoelectric layer 11, v1 is the velocity of the body wave propagating in the piezoelectric layer 11, the direction cosines l1, l2, l3 of the tangent angle in the thickness direction of the piezoelectric layer 11 can be determined by the Euler angle of the piezoelectric layer 11, l1 is cos(θ 11 ), l2 is cos(θ 12 ), l3 is cos(θ13 ), (θ 11 ,θ 12 ,θ 13 ) is the Euler angle of the piezoelectric layer 11. det is a square matrix function used to find the determinant of a square matrix.

[0099] Specifically, when v1 is solved according to formula (I), three solutions are obtained, among which the maximum value among the three solutions is the longitudinal wave component of the body wave propagating in the piezoelectric layer 11, the second largest value among the three solutions is the fast transverse wave component of the body wave propagating in the piezoelectric layer 11, and the maximum value among the three solutions is the slow transverse wave component of the body wave propagating in the piezoelectric layer 11.

[0100] As an implementation method, the dielectric layer 12 is made of an anisotropic material or an isotropic material.

[0101] As an implementation mode, the substrate 13 is made of an anisotropic material or made of an isotropic material.

[0102] In some embodiments, when the dielectric layer 12 and / or the substrate 13 are made of anisotropic materials, the dielectric layer 12 and / or the substrate 13 are anisotropic material layers, and the velocity of the longitudinal wave component of the body wave propagating in the anisotropic material layer is determined based on the elastic stiffness coefficient of the anisotropic material layer, the density of the anisotropic material layer, and the Euler angle of the anisotropic material layer.

[0103] Among them, when the elastic stiffness coefficient and density of the anisotropic material layer are respectively related to the material forming the anisotropic material layer, when the material of the anisotropic material layer is determined, the elastic stiffness coefficient and density thereof are also determined.

[0104] In this embodiment, the speed of the body wave propagating in the anisotropic material layer can be controlled by configuring the material of the anisotropic material layer and the Euler angle of the anisotropic material layer.

[0105] In some embodiments, the velocity of the body wave in the anisotropic material layer can be solved according to the matrix form of the Christopher equation. The velocity of the longitudinal wave component of the body wave propagating in the anisotropic material layer is the maximum value of the solution of the following formula (II):

[0106]

[0107] Among them, Γ′ j′k′ =c i′j′k′l′ *l′ i′ *l′ l′ , c i′j′k′l′is the elastic stiffness coefficient of the anisotropic material layer, i′, j′, k′, l′∈(1,3), l′1, l′2, l′3 are the direction cosines of the tangent angle in the thickness direction of the anisotropic material layer, ρ2 is the density of the anisotropic material layer, and v is the velocity of the body wave propagating in the anisotropic material layer. The direction cosines of the tangent angle in the thickness direction of the anisotropic material layer l′1, l′2, l′3 can be determined by the Euler angle of the anisotropic material layer, l′1 is l′2 is l′3 is is the Euler angle of the anisotropic material layer. det is a square matrix function used to find the determinant of a square matrix.

[0108] Specifically, when the dielectric layer 12 is an anisotropic material layer, when v is solved according to formula (II), three solutions are obtained, among which the maximum value among the three solutions is the longitudinal wave component of the body wave propagating in the dielectric layer 12, the second largest value among the three solutions is the fast transverse wave component of the body wave propagating in the dielectric layer 12, and the maximum value among the three solutions is the slow transverse wave component of the body wave propagating in the dielectric layer 12.

[0109] When the substrate 13 is an anisotropic material layer, when v is solved according to formula (II), three solutions are obtained, among which the maximum value among the three solutions is the longitudinal wave component of the body wave propagating in the substrate 13, the second largest value among the three solutions is the fast transverse wave component of the body wave propagating in the substrate 13, and the maximum value among the three solutions is the slow transverse wave component of the body wave propagating in the substrate 13.

[0110] In some embodiments, when the dielectric layer 12 and / or the substrate 13 are made of isotropic material, the dielectric layer 12 and / or the substrate 13 are isotropic material layers, and the velocity of the longitudinal wave component of the body wave propagating in the isotropic material layer is determined based on the Young's modulus of the isotropic material layer, the Poisson's ratio of the isotropic material layer, and the density of the isotropic material layer, and the isotropic material layer is a layer structure made of isotropic material.

[0111] Among them, when the Young's modulus, Poisson's ratio and density of the isotropic material layer are respectively related to the material forming the isotropic material layer, when the material of the isotropic material layer is determined, its Young's modulus, Poisson's ratio and density are all determined.

[0112] In this embodiment, the speed of the bulk wave propagating in the isotropic material layer can be controlled by configuring the material of the isotropic material layer.

[0113] In some embodiments, the velocity of the longitudinal wave component of a body wave propagating in an isotropic material layer satisfies the following formula (III),

[0114]

[0115] Among them, vl is the longitudinal wave component of the body wave propagating in the isotropic material layer, E is the Young's modulus of the isotropic material layer, u is the Poisson's ratio of the isotropic material layer, and ρ3 is the density of the isotropic material layer.

[0116] Specifically, when the dielectric layer 12 is an isotropic material layer, the v calculated according to formula (III) is: l is the longitudinal wave component of the body wave propagating in the dielectric layer 12.

[0117] When the substrate 13 is an isotropic material layer, v calculated according to formula (III) is l It is the longitudinal wave component of the body wave propagating in the substrate 13.

[0118] As an embodiment, the piezoelectric layer 11 includes lithium tantalate (LiTaO 3 ) or lithium niobate (LiNbO 3 ).

[0119] In some embodiments, the piezoelectric layer 11 is 30-50° YX-cut lithium tantalate.

[0120] As an implementation, see Figure 7 As shown, the surface acoustic wave device 100 further includes a temperature compensation layer 14 disposed between the piezoelectric layer 11 and the dielectric layer 12 .

[0121] In this embodiment, the temperature coefficient of the resonance frequency of the surface acoustic wave device 100 can be reduced by providing the temperature compensation layer 14 .

[0122] In some embodiments, the thickness of the temperature compensation layer 14 is 0.2λ to 0.3λ, where λ is the wavelength of the surface acoustic wave excited by the IDT electrode 20 .

[0123] In this embodiment, the temperature compensation layer 14 should not be too thick, as such a thick temperature compensation layer 14 will affect the proportional relationship between the body wave velocity in the piezoelectric layer 11 and the body wave velocity in the dielectric layer 12; the temperature compensation layer 14 should not be too thin, as such a thin temperature compensation layer 14 will affect the effect of reducing the temperature coefficient of the resonant frequency.

[0124] In some embodiments, see Figure 7 As shown, the surface acoustic wave device 100 further includes a charge trapping layer 15 disposed between the dielectric layer 12 and the substrate 13 .

[0125] In this embodiment, by providing the charge trapping layer 15 , the electrons enriched at the interface between the substrate 13 and the charge trapping layer 15 can be reduced.

[0126] In some embodiments, the thickness of the charge trap layer 15 is in the range of 0.3λ to 1.0λ, where λ is the wavelength of the surface acoustic wave excited by the IDT electrode 20 .

[0127] In some embodiments, the charge trap layer 15 includes polysilicon. For example, the charge trap layer 15 includes N-type polysilicon.

[0128] See also Figure 8 As shown, the ratio of the velocity of the body wave propagating in the dielectric layer 12 to the velocity of the body wave propagating in the piezoelectric layer 11 corresponding to curve La is less than 0.95, and the ratio of the velocity of the body wave propagating in the dielectric layer 12 to the velocity of the body wave propagating in the piezoelectric layer 11 corresponding to curve Lb is greater than 0.95. The intensity of the high-order mode in curve La is much smaller than the intensity of the high-order mode in curve Lb.

[0129] An embodiment of the present application provides a surface acoustic wave device. Fig. 9 As shown, the surface acoustic wave device 200 includes a piezoelectric substrate 10 and an IDT electrode 20. The piezoelectric substrate includes a piezoelectric layer 11 and a substrate 12. The piezoelectric layer 11 is arranged on one side of the substrate 12, and the IDT electrode 20 is arranged on the side of the piezoelectric layer 11 away from the substrate 12.

[0130] The first angle θ1 between the propagation direction S11a of the bulk wave propagating in the piezoelectric layer 11 and the normal line S11b of the surface direction of the piezoelectric layer 11 is the incident angle of the bulk wave in the piezoelectric layer 11. The normal line S11b is parallel to the stacking direction of the piezoelectric layer 11 and the substrate 12.

[0131] In which, the substrate 12 and the piezoelectric layer 11 are configured as follows: the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is less than 0.933; and / or the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer 11 is less than 1.6.

[0132] The first angle θ1 between the propagation direction S11a of the body wave propagating in the piezoelectric layer 11 and the normal line S11b of the surface of the piezoelectric layer 11 is less than 15°.

[0133] In this embodiment, since the longitudinal wave component occupies most of the energy of the body wave, by controlling the velocity ratio of the longitudinal wave component of the substrate to the longitudinal wave component of the piezoelectric layer and / or the velocity ratio of the longitudinal wave component of the substrate to the transverse wave component of the piezoelectric layer within the above range, the ratio of the longitudinal wave component and / or the transverse wave component of the piezoelectric layer transmitted into the substrate is increased, which is conducive to further improving the suppression effect of the high-order mode. In addition, the body wave whose first angle between the propagation direction and the normal is less than 15° occupies most of the energy in the piezoelectric layer. By selecting the piezoelectric layer and the substrate, the body wave that occupies most of the energy is transmitted to the bottom of the piezoelectric layer, which is conducive to further improving the suppression effect of the high-order mode.

[0134] As an implementation method, the thickness of the substrate 12 is greater than the thickness of the piezoelectric layer 11 .

[0135] As an implementation, the substrate 12 includes single crystal silicon, silicon carbide, gallium nitride or gallium arsenide.

[0136] As an embodiment, the piezoelectric layer 11 includes lithium tantalate or lithium niobate.

[0137] As an embodiment, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.73.

[0138] As an embodiment, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer 11 is greater than 1.27.

[0139] As an embodiment, the velocities of the longitudinal wave component and the transverse wave component of the body wave propagating in the piezoelectric layer 11 are determined based on the elastic stiffness coefficient of the piezoelectric layer 11, the piezoelectric coefficient of the piezoelectric layer 11, the dielectric constant of the piezoelectric layer 11, the density of the piezoelectric layer 11 and the Euler angle of the piezoelectric layer 11. The body wave propagating in the piezoelectric layer 11 includes a first transverse wave and a second transverse wave. The velocity of the first transverse wave is greater than that of the second transverse wave. The transverse wave component of the body wave propagating in the piezoelectric layer 11 is the second transverse wave.

[0140] As an embodiment, the substrate 12 is made of anisotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the substrate is obtained based on the elastic stiffness coefficient of the substrate 12, the density of the substrate 12 and the Euler angle of the substrate 12.

[0141] As an implementation mode, the substrate 12 is made of an isotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 is obtained based on the Young's modulus of the substrate 12 , the Poisson's ratio of the substrate 12 , and the density of the substrate 12 .

[0142] In some preferred embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.73 and less than 0.933; the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate 12 to the velocity of the shear wave component of the body wave propagating in the piezoelectric layer 11 is greater than 1.27 and less than 1.6. Exemplarily, the shear wave component of the body wave propagating in the piezoelectric layer 11 is a slow shear wave component.

[0143] In this embodiment, by controlling the velocity ratio of the longitudinal wave component of the substrate to the longitudinal wave component of the piezoelectric layer and the velocity ratio of the longitudinal wave component of the substrate to the transverse wave component of the piezoelectric layer within corresponding ranges, while increasing the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the substrate, it is beneficial to increase the body wave velocity in the substrate without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thereby avoiding the problem of poor proximal out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0144] For other features of the piezoelectric layer 11 and the substrate 12 in the surface acoustic wave device 200 of this embodiment, reference may be made to the description of the surface acoustic wave device 100 in the above embodiment, and they will not be described in detail here.

[0145] An embodiment of the present application provides a surface acoustic wave device. Fig.10 As shown, the surface acoustic wave device 300 includes a piezoelectric substrate 10 and an IDT electrode 20, wherein the piezoelectric substrate 10 includes a piezoelectric layer 11, a dielectric layer 12 and a substrate 13, the dielectric layer 12 is arranged on one side of the substrate 13, and the piezoelectric layer 11 is arranged on a side of the dielectric layer 12 away from the substrate 13. The IDT electrode 20 is arranged on a side of the piezoelectric layer 11 away from the substrate 12.

[0146] The first angle θ1 between the propagation direction S11a of the bulk wave propagating in the piezoelectric layer 11 and the normal line S11b of the surface direction of the piezoelectric layer 11 is the incident angle of the bulk wave in the piezoelectric layer 11. The normal line S11b is parallel to the stacking direction of the piezoelectric layer 11 and the dielectric layer 12.

[0147] The second angle θ2 between the propagation direction S12a of the body wave propagating in the dielectric layer 12 and the normal line S12b of the surface of the dielectric layer 12 is the transmission angle. The normal line S12b is parallel to the stacking direction of the piezoelectric layer 11 and the dielectric layer 12.

[0148] The dielectric layer 12 and the piezoelectric layer 11 are configured such that the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is less than 0.95.

[0149] The dielectric layer 12 and the substrate 13 are configured such that the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the substrate 13 is less than 0.615.

[0150] Among them, the first angle θ1 between the propagation direction of the body wave propagating in the piezoelectric layer 11 and the normal to the surface of the piezoelectric layer 11 is less than 15°, and the second angle θ2 between the propagation direction of the body wave propagating in the dielectric layer 12 and the normal to the surface of the dielectric layer 12 is less than 20°.

[0151] In this embodiment, since the longitudinal wave component occupies most of the energy of the body wave, by controlling the speed ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the piezoelectric layer within the above-mentioned range, the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer is increased, which is beneficial to further improve the suppression effect of high-order modes; by controlling the speed ratio of the longitudinal wave component in the dielectric layer to the longitudinal wave component of the substrate within the above-mentioned range, it is beneficial to increase the body wave velocity in the substrate, will not lead to a decrease in the resonant frequency of the main mode of the acoustic surface wave, will not lead to a decrease in the cutoff frequency of the body wave, and will avoid the problem of poor proximal out-of-band suppression caused by the cutoff frequency of the body wave being close to the anti-resonance frequency.

[0152] As an embodiment, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the substrate 13 is greater than 0.41.

[0153] As an embodiment, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.75.

[0154] As an implementation mode, the piezoelectric layer 11 includes lithium tantalate or lithium niobate, the dielectric layer 12 includes silicon nitride or aluminum oxide, and the substrate 13 includes silicon material, silicon carbide, gallium nitride or gallium arsenide.

[0155] As an embodiment, the velocities of the longitudinal wave component and the transverse wave component of the body wave propagating in the piezoelectric layer 11 are determined based on the elastic stiffness coefficient of the piezoelectric layer 11, the piezoelectric coefficient of the piezoelectric layer 11, the dielectric constant of the piezoelectric layer 11, the density of the piezoelectric layer 11 and the Euler angle of the piezoelectric layer 11. The body wave propagating in the piezoelectric layer 11 includes a first transverse wave and a second transverse wave. The velocity of the first transverse wave is greater than that of the second transverse wave. The transverse wave component of the body wave propagating in the piezoelectric layer 11 is the second transverse wave.

[0156] As an embodiment, at least one of the substrate 13 and the dielectric layer 12 is made of anisotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the anisotropic material layer is determined based on the elastic stiffness coefficient of the anisotropic material layer, the density of the anisotropic material layer and the Euler angle of the anisotropic material layer.

[0157] As an embodiment, at least one layer among the substrate 13 and the dielectric layer 12 is made of isotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the isotropic material layer is determined based on the Young's modulus of the isotropic material layer, the Poisson's ratio of the isotropic material layer and the density of the isotropic material layer.

[0158] In some preferred embodiments, the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the substrate 13 is greater than 0.41 and less than 0.615; the ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer 12 to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer 11 is greater than 0.75 and less than 0.95.

[0159] In this embodiment, by controlling the speed ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the substrate and the speed ratio of the longitudinal wave component of the dielectric layer to the longitudinal wave component of the piezoelectric layer within corresponding ranges, it is beneficial to increase the proportion of the longitudinal wave component of the piezoelectric layer transmitted into the dielectric layer and the proportion of the longitudinal wave component of the dielectric layer projected into the substrate, respectively, and at the same time it is beneficial to increase the body wave velocity in the dielectric layer and the body wave velocity in the substrate, respectively, without causing a decrease in the resonant frequency of the main mode of the acoustic surface wave or the cutoff frequency of the body wave, thus avoiding the problem of poor proximal out-of-band suppression due to the close proximity of the cutoff frequency of the body wave to the anti-resonance frequency.

[0160] For other features of the piezoelectric layer 11 , the dielectric layer 12 and the substrate 13 in the surface acoustic wave device 300 of this embodiment, reference may be made to the description of the surface acoustic wave device 100 of the above embodiment, and will not be described in detail here.

[0161] An embodiment of the present application provides a radio frequency front-end module 400, see Fig.11 As shown, the RF front-end module 400 includes a surface acoustic wave device, which is the above-mentioned surface acoustic wave device 100, surface acoustic wave device 200 or surface acoustic wave device 300. The RF front-end module 400 may also include at least one of a RF power amplifier, a low noise amplifier, an antenna unit, a switch unit, etc., which is not specifically limited in this application.

[0162] The RF front-end module of this embodiment selects a suitable dielectric layer and a piezoelectric layer so that the ratio of the speed of the body wave propagating in the dielectric layer to the speed of the body wave propagating in the piezoelectric layer is controlled within the above-mentioned range, making it easier for the body wave to be transmitted to the bottom of the piezoelectric layer, thereby suppressing the formation of higher-order modes to a certain extent, which is beneficial to reducing the adverse effects of higher-order modes on the propagation of surface acoustic waves and improving the performance of surface acoustic wave devices.

[0163] The present application also provides an electronic device 500. Fig.12As shown, the electronic device 500 includes the above-mentioned RF front-end module 400. The electronic device can be, but is not limited to, a smart wearable device or a mobile terminal. Smart wearable devices include, but are not limited to, smart watches, smart bracelets, and cervical massagers. Mobile terminals include, but are not limited to, smart phones, laptops, tablet computers, and POS (point of sales terminal).

[0164] The electronic device of this embodiment, by selecting a suitable dielectric layer and piezoelectric layer, controls the ratio of the speed of the body wave propagating in the dielectric layer to the speed of the body wave propagating in the piezoelectric layer within the above range, making it easier for the body wave to be transmitted to the bottom of the piezoelectric layer, thereby suppressing the formation of higher-order modes to a certain extent, which is beneficial to reducing the adverse effects of higher-order modes on the propagation of surface acoustic waves and improving the performance of surface acoustic wave devices.

[0165] The above is only an implementation method of the present application. It should be pointed out that a person skilled in the art can make improvements without departing from the inventive concept of the present application, but these improvements are within the scope of protection of the present application.

Claims

1. A surface acoustic wave device, characterized in that: include: A piezoelectric substrate, the piezoelectric substrate comprising a dielectric layer and a piezoelectric layer arranged on one side of the dielectric layer; An IDT electrode is arranged on a side of the piezoelectric layer away from the dielectric layer; The dielectric layer and the piezoelectric layer are configured such that a ratio of a velocity of a body wave propagating in the dielectric layer to a velocity of a body wave propagating in the piezoelectric layer is less than 0.

95.

2. The surface acoustic wave device according to claim 1, characterized in that: A first angle between a propagation direction of a body wave propagating in the piezoelectric layer and a normal to a direction in which a surface of the piezoelectric layer is located is less than 15°.

3. The surface acoustic wave device according to claim 1, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is less than 0.

95.

4. The surface acoustic wave device according to claim 3, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is less than 0.

933.

5. The surface acoustic wave device according to claim 4, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is greater than 0.

73.

6. The surface acoustic wave device according to claim 4, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer is less than 1.

6.

7. The surface acoustic wave device according to claim 6, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer is greater than 1.

27.

8. The surface acoustic wave device according to claim 1, characterized in that: The dielectric layer is a substrate, and the thickness of the substrate is greater than the thickness of the piezoelectric layer; the substrate includes sapphire, single crystal silicon, silicon carbide, gallium nitride, aluminum nitride, silicon nitride or gallium arsenide.

9. The surface acoustic wave device according to claim 1, characterized in that: The piezoelectric substrate also includes a substrate, which is arranged on a side of the dielectric layer away from the piezoelectric layer, and the thickness of the substrate is greater than the thickness of the dielectric layer and the thickness of the piezoelectric layer; the substrate includes single crystal silicon, silicon carbide, gallium nitride or gallium arsenide, and the dielectric layer includes silicon nitride or aluminum oxide.

10. The surface acoustic wave device according to claim 9, characterized in that: A second angle between a propagation direction of a body wave propagating in the dielectric layer and a normal to a direction in which a surface of the dielectric layer is located is less than 20°.

11. The surface acoustic wave device according to claim 9, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the substrate is less than 0.

615.

12. The surface acoustic wave device according to claim 11, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the substrate is greater than 0.

41.

13. The surface acoustic wave device according to claim 9, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is greater than 0.

75.

14. The surface acoustic wave device according to any one of claims 1 to 13, characterized in that: The velocities of the longitudinal wave component and the transverse wave component of the body wave propagating in the piezoelectric layer are determined based on the elastic stiffness coefficient of the piezoelectric layer, the piezoelectric coefficient of the piezoelectric layer, the dielectric constant of the piezoelectric layer, the density of the piezoelectric layer and the Euler angle of the piezoelectric layer. The body wave propagating in the piezoelectric layer includes a first transverse wave and a second transverse wave. The velocity of the first transverse wave is greater than the velocity of the second transverse wave. The transverse wave component of the body wave propagating in the piezoelectric layer is the second transverse wave.

15. The surface acoustic wave device according to claim 14, characterized in that: The velocity values ​​of the longitudinal wave component and the transverse wave component of the body wave propagating in the piezoelectric layer are solutions of the following formula (I), and there are multiple solutions of formula (I). The longitudinal wave component of the body wave propagating in the piezoelectric layer is the maximum value among the multiple solutions, and the transverse wave component of the body wave propagating in the piezoelectric layer is the minimum value among the multiple solutions. Among them, Γ jk =c ijkl *l i *l l , Γ j4 =Γ 4j =e kij *l i *l k , Γ 44 =-l i *ε ik *l k , c ijkl is the elastic stiffness coefficient of the piezoelectric layer, e kij is the piezoelectric coefficient of the piezoelectric layer, ε ik is the dielectric constant of the piezoelectric layer, i, j, k, l∈(1, 3), l1, l2, l3 are the direction cosines of the cutting angle in the thickness direction of the piezoelectric layer, ρ1 is the density of the piezoelectric layer, and v1 is the velocity of the body wave propagating in the piezoelectric layer.

16. The surface acoustic wave device according to any one of claims 1 to 13, characterized in that: The dielectric layer is made of anisotropic material or isotropic material; and / or the substrate is made of anisotropic material or isotropic material.

17. The surface acoustic wave device according to claim 16, characterized in that: In the case where the dielectric layer and / or the substrate are made of anisotropic material, the velocity of the longitudinal wave component of the body wave propagating in the anisotropic material layer is determined based on the elastic stiffness coefficient of the anisotropic material layer, the density of the anisotropic material layer and the Euler angle of the anisotropic material layer, wherein the anisotropic material layer is a layer structure made of anisotropic material.

18. The surface acoustic wave device according to claim 17, characterized in that: The velocity of the longitudinal wave component of the body wave propagating in the anisotropic material layer is the maximum value of the solution of the following formula (II): Among them, Γ′ j′k′ =c i′j′k′l′ *l′ i′ *l′ l′ , c i′j′k′l′ is the elastic stiffness coefficient of the anisotropic material layer, i′, j′, k′, l′∈(1, 3), l′1, l′2, l′3 are the direction cosines of the cutting angle in the thickness direction of the anisotropic material layer, ρ2 is the density of the anisotropic material layer, and c is the velocity of the body wave propagating in the anisotropic material layer.

19. The surface acoustic wave device according to claim 16, characterized in that: In the case where the dielectric layer and / or the substrate are made of isotropic material, the velocity of the longitudinal wave component of the body wave propagating in the isotropic material layer is determined based on the Young's modulus of the isotropic material layer, the Poisson's ratio of the isotropic material layer and the density of the isotropic material layer, and the isotropic material layer is a layer structure made of isotropic material.

20. The surface acoustic wave device according to claim 19, characterized in that: The velocity of the longitudinal wave component of the body wave propagating in the isotropic material layer satisfies the following formula (III): Among them, v l is the longitudinal wave component of the body wave propagating in the isotropic material layer, E is the Young's modulus of the isotropic material layer, u is the Poisson's ratio of the isotropic material layer, and ρ3 is the density of the isotropic material layer.

21. The surface acoustic wave device according to claim 1, characterized in that: The piezoelectric layer includes lithium tantalate or lithium niobate.

22. The surface acoustic wave device according to claim 21, characterized in that: The piezoelectric layer is 30-50° YX-cut lithium tantalate.

23. The surface acoustic wave device according to claim 1, characterized in that: The thickness of the piezoelectric layer is 0.2λ to 0.5λ, wherein λ is the wavelength of the surface acoustic wave excited by the IDT electrode.

24. The surface acoustic wave device according to any one of claims 1 to 13, characterized in that: The surface acoustic wave device further comprises a temperature compensation layer disposed between the piezoelectric layer and the dielectric layer; and / or, The device also includes a charge trapping layer disposed between the dielectric layer and the substrate.

25. A surface acoustic wave device, characterized in that: include: A piezoelectric substrate, comprising a substrate and a piezoelectric layer disposed on one side of a dielectric layer; An IDT electrode is arranged on a side of the piezoelectric layer away from the dielectric layer; The substrate and the piezoelectric layer are configured as follows: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is less than 0.933; and / or the ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer is less than 1.6; A first angle between a propagation direction of a body wave propagating in the piezoelectric layer and a normal to a direction in which a surface of the piezoelectric layer is located is less than 15°.

26. The surface acoustic wave device according to claim 25, characterized in that: The thickness of the substrate is greater than that of the piezoelectric layer. The substrate includes single crystal silicon, silicon carbide, gallium nitride or gallium arsenide. The piezoelectric layer includes lithium tantalate or lithium niobate.

27. The surface acoustic wave device according to claim 25, characterized in that: The ratio of the velocity of the longitudinal wave component of the bulk wave propagating in the substrate to the velocity of the longitudinal wave component of the bulk wave propagating in the piezoelectric layer is greater than 0.

73.

28. The surface acoustic wave device according to claim 25, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the substrate to the velocity of the transverse wave component of the body wave propagating in the piezoelectric layer is greater than 1.

27.

29. The surface acoustic wave device according to claim 25, characterized in that: The velocities of the longitudinal wave component and the transverse wave component of the body wave propagating in the piezoelectric layer are determined based on the elastic stiffness coefficient of the piezoelectric layer, the piezoelectric coefficient of the piezoelectric layer, the dielectric constant of the piezoelectric layer, the density of the piezoelectric layer and the Euler angle of the piezoelectric layer. The body wave propagating in the piezoelectric layer includes a first transverse wave and a second transverse wave. The velocity of the first transverse wave is greater than the velocity of the second transverse wave. The transverse wave component of the body wave propagating in the piezoelectric layer is the second transverse wave.

30. The acoustic wave resonator according to claim 25, characterized in that The substrate is made of anisotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the substrate is obtained according to the elastic stiffness coefficient of the substrate, the density of the substrate and the Euler angle of the substrate.

31. The acoustic wave resonator according to claim 25, characterized in that The substrate is made of isotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the substrate is obtained according to the Young's modulus of the substrate, the Poisson's ratio of the substrate, and the density of the substrate.

32. A surface acoustic wave device, characterized in that: include: A piezoelectric substrate, the piezoelectric substrate comprising a substrate, a dielectric layer disposed on one side of the substrate, and a piezoelectric layer disposed on a side of the dielectric layer away from the substrate; An IDT electrode is arranged on a side of the piezoelectric layer away from the substrate; The dielectric layer and the piezoelectric layer are configured such that a ratio of a velocity of a longitudinal wave component of a body wave propagating in the dielectric layer to a velocity of a longitudinal wave component of a body wave propagating in the piezoelectric layer is less than 0.95; The dielectric layer and the substrate are configured such that a ratio of a velocity of a longitudinal wave component of a body wave propagating in the dielectric layer to a velocity of a longitudinal wave component of a body wave propagating in the substrate is less than 0.615; A first angle between a propagation direction of a body wave propagating in the piezoelectric layer and a normal to a surface of the piezoelectric layer is less than 15°, and a second angle between a propagation direction of a body wave propagating in the dielectric layer and a normal to a surface of the dielectric layer is less than 20°.

33. The surface acoustic wave device according to claim 32, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the substrate is greater than 0.

41.

34. The surface acoustic wave device according to claim 32, characterized in that: The ratio of the velocity of the longitudinal wave component of the body wave propagating in the dielectric layer to the velocity of the longitudinal wave component of the body wave propagating in the piezoelectric layer is greater than 0.

75.

35. The surface acoustic wave device according to claim 32, characterized in that: The piezoelectric layer includes lithium tantalate or lithium niobate, the dielectric layer includes silicon nitride or aluminum oxide, and the substrate includes silicon material, silicon carbide, gallium nitride or gallium arsenide.

36. The surface acoustic wave device according to claim 32, characterized in that: The velocities of the longitudinal wave component and the transverse wave component of the body wave propagating in the piezoelectric layer are determined based on the elastic stiffness coefficient of the piezoelectric layer, the piezoelectric coefficient of the piezoelectric layer, the dielectric constant of the piezoelectric layer, the density of the piezoelectric layer and the Euler angle of the piezoelectric layer. The body wave propagating in the piezoelectric layer includes a first transverse wave and a second transverse wave. The velocity of the first transverse wave is greater than the velocity of the second transverse wave. The transverse wave component of the body wave propagating in the piezoelectric layer is the second transverse wave.

37. The surface acoustic wave device according to claim 32, characterized in that: At least one of the substrate and the dielectric layer is made of anisotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the anisotropic material layer is determined based on the elastic stiffness coefficient of the anisotropic material layer, the density of the anisotropic material layer and the Euler angle of the anisotropic material layer.

38. The surface acoustic wave device according to claim 32, characterized in that: At least one of the substrate and the dielectric layer is made of isotropic material, and the velocity of the longitudinal wave component of the body wave propagating in the isotropic material layer is determined based on the Young's modulus of the isotropic material layer, the Poisson's ratio of the isotropic material layer and the density of the isotropic material layer.

39. A radio frequency front-end module, characterized in that: Comprising the surface acoustic wave device as claimed in any one of claims 1 to 38.

40. An electronic device, characterized in that: Comprising the RF front-end module as described in claim 39.

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