Surface acoustic wave resonator, surface acoustic wave filter, and electronic device

Abstract

The invention discloses a surface acoustic wave resonator, a surface acoustic wave filter and an electronic device, and belongs to the technical field of semiconductors. The surface acoustic wave resonator includes: a substrate; the Bragg reflection structure is located on one side of the substrate in the thickness direction, the Bragg reflection structure comprises a first high-impedance layer and a first low-impedance layer which are alternately stacked in the thickness direction, and the thickness of the first high-impedance layer and the thickness of the first low-impedance layer are respectively 1 / 4 wavelength; the first high-impedance layer and the first low-impedance layer respectively comprise at least one of an isotropic material and an anisotropic material; the first piezoelectric layer is located on the side, away from the substrate, of the Bragg reflection structure; the first electrode layer is located on the side, away from the Bragg reflection structure, of the first piezoelectric layer. According to the invention, out-of-band spurious signals and high-frequency spurious signals can be suppressed or attenuated, and the performance of the surface acoustic wave resonator is improved.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor technology, and in particular relates to a surface acoustic wave resonator, a surface acoustic wave filter and an electronic device. Background Art

[0002] Surface acoustic wave resonators are widely used in various acoustic devices, with advantages such as low insertion loss, wide bandwidth, small size, low cost, and mass production. However, when the main mode is excited, the surface acoustic wave resonator will also generate out-of-band spurious and high-frequency spurious. The out-of-band spurious and high-frequency spurious are useless acoustic modes with different propagation characteristics from the main mode, which affect the performance of the resonator. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a surface acoustic wave resonator, a surface acoustic wave filter and an electronic device, which can suppress or attenuate out-of-band stray signals and high-frequency stray signals, and improve the performance of the surface acoustic wave resonator.

[0004] In a first aspect, the present application provides a surface acoustic wave resonator, comprising:

[0005] substrate;

[0006] A Bragg reflection structure, located on one side of the substrate in a thickness direction, the Bragg reflection structure comprising a first high-impedance layer and a first low-impedance layer alternately stacked along the thickness direction, the thickness of the first high-impedance layer and the first low-impedance layer are respectively one-quarter wavelength, and the first high-impedance layer and the first low-impedance layer respectively comprise at least one of an isotropic material and an anisotropic material;

[0007] A first piezoelectric layer is located on a side of the Bragg reflection structure away from the substrate;

[0008] The first electrode layer is located at a side of the first piezoelectric layer away from the Bragg reflection structure.

[0009] According to one embodiment of the present application, the first high-impedance layer includes a rotatable anisotropic material; the first low-impedance layer includes an isotropic material or a rotatable anisotropic material, or the first low-impedance layer includes a first low-impedance sublayer and a second low-impedance sublayer stacked along the thickness direction, the first low-impedance sublayer includes an isotropic material or an anisotropic material, and the second low-impedance sublayer includes a rotatable anisotropic material.

[0010] According to an embodiment of the present application, the Bragg reflection structure further includes a binding layer; the binding layer is located on a side of the Bragg reflection structure close to the substrate.

[0011] According to one embodiment of the present application, the binding layer includes a second high-impedance layer or a second low-impedance layer, and the second high-impedance layer or the second low-impedance layer includes an isotropic material or an anisotropic material.

[0012] According to one embodiment of the present application, the first high-impedance layer includes a plurality of high-impedance sub-layers stacked along the thickness direction, and the impedances of the plurality of high-impedance sub-layers are different.

[0013] According to one embodiment of the present application, the multiple high impedance sublayers include a first high impedance sublayer and a second high impedance sublayer, the impedance of the first high impedance sublayer is smaller than the impedance of the second high impedance sublayer, and the thickness ratio of the first high impedance sublayer to the second high impedance sublayer is 5%-30%.

[0014] According to an embodiment of the present application, the high-resistance sub-layer includes a soft metal, and the soft metal includes Mg, Al or Ti.

[0015] According to one embodiment of the present application, the first low-impedance layer is a single-layer structure or a stacked-layer structure.

[0016] According to one embodiment of the present application, the substrate includes a support layer, and the support layer includes an isotropic material or an anisotropic material.

[0017] According to an embodiment of the present application, the support layer includes HTCC ceramics.

[0018] According to one embodiment of the present application, the first piezoelectric layer is a single-layer structure or a stacked-layer structure.

[0019] According to one embodiment of the present application, the substrate includes a second piezoelectric layer and a second electrode layer; the second piezoelectric layer is located on a side of the Bragg reflection structure away from the first piezoelectric layer, and the second electrode layer is located on a side of the second piezoelectric layer away from the Bragg reflection structure.

[0020] In a second aspect, the present application provides a surface acoustic wave filter, comprising the surface acoustic wave resonator as described in the first aspect above.

[0021] In a third aspect, the present application provides an electronic device comprising the surface acoustic wave filter as described in the second aspect above.

[0022] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0023] A Bragg reflection structure is arranged in the surface acoustic wave resonator, wherein the Bragg reflection structure comprises a first high-impedance layer and a first low-impedance layer which are alternately stacked, wherein the thickness of the first high-impedance layer and the first low-impedance layer are respectively one-quarter of the wavelength of the surface acoustic wave, and the first high-impedance layer and the first low-impedance layer respectively comprise at least one of an isotropic material and an anisotropic material, so as to optimize the high-frequency transmission band and the forbidden band of the surface acoustic wave resonator by optimizing the material and structure of the Bragg reflection structure, thereby suppressing or attenuating out-of-band stray signals and high-frequency stray signals of the surface acoustic wave resonator, and further optimizing the performance of the surface acoustic wave resonator;

[0024] Furthermore, by setting the first high-impedance layer as a plurality of high-impedance sub-layers with different impedances, the high-frequency transmission band and the forbidden band are controlled while maintaining the main forbidden band, so as to further suppress or attenuate the high-frequency stray signal of the surface acoustic wave resonator;

[0025] Further, the support layer includes an isotropic material or an anisotropic material, such as HTCC ceramic, to suppress or attenuate in-band stray signals of the surface acoustic wave resonator.

[0026] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0028] Figure 1 It is one of the structural schematic diagrams of the surface acoustic wave resonator provided in the embodiment of the present application;

[0029] Figure 2 This is the second structural schematic diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0030] Figure 3 This is the third structural schematic diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0031] Figure 4 is one of the amplitude variation curves of the transmission coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0032] Figure 5 This is the second curve diagram of the amplitude variation of the transmission coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0033] Figure 6 This is the fourth structural schematic diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0034] Figure 7This is the fifth structural diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0035] Figure 8 This is the sixth structural schematic diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0036] Fig. 9 This is the seventh structural schematic diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0037] Fig.10 This is the eighth structural schematic diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0038] Fig.11 This is the third curve diagram of the amplitude variation of the transmission coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0039] Fig.12 This is the fourth curve diagram of the amplitude variation of the transmission coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0040] Fig.13 This is the fifth curve diagram of the amplitude variation of the transmission coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0041] Fig.14 This is the sixth curve diagram of the amplitude variation of the transmission coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0042] Fig.15 This is the ninth structural diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0043] Fig.16 This is the tenth structural diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0044] Fig.17 This is the eleventh structural diagram of the surface acoustic wave resonator provided in the embodiment of the present application;

[0045] Fig.18 is one of the amplitude variation curves of the reflection coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0046] Fig.19 This is the second graph of the amplitude variation of the reflection coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0047] Fig. 20 This is the third graph of the amplitude variation of the reflection coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0048] Fig.21 This is the fourth graph of the amplitude variation of the reflection coefficient of the surface acoustic wave resonator provided in the embodiment of the present application;

[0049] Fig. 22 This is the twelfth structural diagram of the surface acoustic wave resonator provided in the embodiment of the present application. DETAILED DESCRIPTION

[0050] 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.

[0051] The surface acoustic wave resonator, the surface acoustic wave filter and the electronic device provided by the embodiments of the present application are described below with reference to the accompanying drawings.

[0052] Figure 1 A schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of the present application.

[0053] like Figure 1 As shown, the surface acoustic wave resonator provided in the embodiment of the present application includes a substrate 1, a Bragg reflection structure 2, a first piezoelectric layer 31 and a first electrode layer 51. The Bragg reflection structure 2 is located on one side of the substrate 1 along the thickness direction. The Bragg reflection structure 2 includes a first high-impedance layer 22 and a first low-impedance layer 21 alternately stacked along the thickness direction, the thickness of the first high-impedance layer 22 and the first low-impedance layer 21 are respectively one-quarter wavelength, and the first high-impedance layer 22 and the first low-impedance layer 21 respectively include at least one of an isotropic material and an anisotropic material.

[0054] The stacking order of the first high-impedance layer 22 and the first low-impedance layer 21 is not specifically limited. Figure 2 As shown, the first high impedance layer 22 may be stacked first and then the first low impedance layer 21 may be stacked. The bottom layer of the Bragg reflection structure 2 (i.e., the film layer closest to the substrate 1 in the Bragg reflection structure 2) may be the first high impedance layer 22, and the top layer of the Bragg reflection structure 2 (i.e., the film layer farthest from the substrate 1 in the Bragg reflection structure 2) may be the first low impedance layer 21. Figure 3 As shown, the first low impedance layer 21 may be stacked first, then the first high impedance layer 22, and finally the first low impedance layer 21, that is, there is a first high impedance layer 22 between any two first low impedance layers 21. Both the bottom layer and the top layer of the Bragg reflection structure 2 may be the first low impedance layer 21.

[0055] The number of stacked layers of the first high impedance layer 22 and the first low impedance layer 21 in the Bragg reflection structure 2 can be set according to actual needs. By increasing the number of stacked layers of the first high impedance layer 22 and the first low impedance layer 21, the reflection efficiency of the Bragg reflection structure 2 can be improved, the reflection effect on clutter can be improved, and thus the spurious suppression effect can be improved.

[0056] According to the formula and formula It can be seen that in order to achieve maximum reflection of clutter in the Bragg reflection structure 2, the phase of the reflected wave in the Bragg reflection structure 2 should be changed by 180 degrees, and the thickness of the first high impedance layer 22 and the first low impedance layer 21 should be set to one quarter of the wavelength of the surface acoustic wave. Wherein, n is the refractive index, d is the thickness of the film layer in the Bragg reflection structure 2, λ is the wavelength of the surface acoustic wave, and k is an integer. When k is 1, it means that the surface acoustic wave propagates in the main mode; when k is an integer greater than 1, it means that the surface acoustic wave propagates in the high-frequency mode. i is the thickness of the film layer in the Bragg reflection structure 2, v i is the propagation speed of the surface acoustic wave in the Bragg reflection structure 2, and f0 is the resonance frequency at which the material of the film layer in the Bragg reflection structure 2 resonates under certain conditions.

[0057] When the thickness of the first high-impedance layer 22 and the first low-impedance layer 21 are respectively one-fourth of the wavelength of the surface acoustic wave, the film layer in the Bragg reflection structure 2 reaches the optimal thickness condition, thereby enhancing the reflection intensity of the reflected wave at the interface between the two film layers and optimizing the suppression or attenuation of out-of-band stray signals and high-frequency stray signals.

[0058] The first low-impedance layer 21 may include one or more combinations of isotropic materials and anisotropic materials, and the first high-impedance layer 22 may also include one or more combinations of isotropic materials and anisotropic materials. Isotropic materials have the same mechanical and thermal properties in all directions, while anisotropic materials have different mechanical and thermal properties in different directions. The material types of the first low-impedance layer 21 and the first high-impedance layer 22 may be the same or different, and the material type may include one or more combinations of isotropic materials and anisotropic materials.

[0059] Every two adjacent film layers (including a first high-impedance layer 22 and a first low-impedance layer 21) can form a Bragg reflection unit, and the Bragg reflection structure 2 can include one or more stacked Bragg reflection units. The stacking order, material type, and number of the first low-impedance layer 21 and the first high-impedance layer 22 in the Bragg reflection unit can be set according to the main mode propagating in the surface acoustic wave resonator in actual applications.

[0060] The material and structure of the Bragg reflection structure 2 have a significant influence on the high-frequency transmission band and the forbidden band. By selecting appropriate materials and accurately optimizing the Bragg reflection structure 2, the out-of-band stray signals and high-frequency stray signals of the surface acoustic wave resonator can be effectively suppressed or attenuated.

[0061] The surface acoustic wave resonator further includes a first piezoelectric layer 31, which is located on a side of the Bragg reflection structure 2 that is away from the substrate 1. Figures 1 to 3 As shown, the first piezoelectric layer 31 is located above the Bragg reflection structure 2 .

[0062] The surface acoustic wave resonator also includes a first electrode layer 51, which is located on a side of the first piezoelectric layer 31 away from the Bragg reflection structure 2. In some embodiments, the first electrode layer 51 may include a plurality of electrode fingers, a first bus bar, and a second bus bar. The plurality of electrode fingers include first electrode fingers and second electrode fingers that are alternately and spaced apart along a first direction. The first electrode fingers and the second electrode fingers both extend along a second direction. The first direction, the second direction, and the thickness direction are perpendicular to each other. The first bus bar and the second bus bar are respectively located on opposite sides of the plurality of electrode fingers along the first direction, and the first bus bar and the second bus bar both extend along the first direction. The first electrode finger is connected to the first bus bar, and the second electrode finger is connected to the second bus bar.

[0063] The number of the first electrode finger and the second electrode finger may be the same. The size (including length and width, etc.) of the first electrode finger and the second electrode finger may be the same. The materials of the first electrode finger and the second electrode finger may both include metal materials such as copper and aluminum. The first busbar and the second busbar may be used as connecting wires connecting adjacent resonators or connecting wires connecting the package side. The materials of the first busbar and the second busbar may both include metal materials such as copper and aluminum.

[0064] The surface acoustic wave resonator includes a transmission band and a forbidden band, and the transmission band and forbidden band include a main mode and a high-frequency mode. By optimizing the material and structure of the Bragg reflection structure 2, the transmission band and forbidden band of the surface acoustic wave resonator are optimized, thereby suppressing or attenuating the out-of-band stray signals and high-frequency stray signals of the surface acoustic wave resonator, and then optimizing the performance of the surface acoustic wave resonator. The Bragg reflection structure 2 has multiple forbidden bands and transmission bands, which can be used to limit the acoustic energy of resonators with different acoustic modes, different resonance frequencies, or multi-mode resonators (with multiple resonance frequencies) on the same Bragg reflection structure 2. Different acoustic modes propagating in the first piezoelectric layer 31 have different corresponding forbidden bands. The main forbidden band of the Bragg reflection structure 2 is usually used for acoustic isolation between the main mode of the surface acoustic wave and the substrate 1. Many acoustic modes will be generated in the Bragg reflection structure 2, accompanied by a large amount of radiated stray signals. The high-frequency transmission band of the Bragg reflection structure 2 can be used to suppress or attenuate the out-of-band or high-frequency acoustic mode generated in the first piezoelectric layer 31. The transmission band of the Bragg reflection structure 2 can also be used to attenuate high-frequency stray signals generated by the leakage of the surface acoustic wave to the substrate 1. By optimizing the material and structure of the Bragg reflection structure 2, these stray modes can be suppressed or attenuated.

[0065] For example, the Bragg reflection structure 2 includes three stacked Bragg reflection units. When the materials of the first high impedance layer 22 in the Bragg reflection unit are tungsten and platinum, respectively, the amplitude of the transmission coefficient of the surface acoustic wave resonator in a wide frequency range in TE (thickness tension) and SV (vertical shear) modes is detected. The acoustic impedance of tungsten is higher than that of platinum. When the first high impedance layer 22 in the Bragg reflection unit is tungsten, the Bragg reflection structure 2 is optimized for low-frequency band applications. The curve of the amplitude of the transmission coefficient of the surface acoustic wave resonator in a wide frequency range changing with frequency is shown in FIG. Figure 4 When the first high impedance layer 22 in the Bragg reflection unit is platinum, the Bragg reflection structure 2 is optimized for low-frequency band applications, and the curve of the amplitude of the transmission coefficient of the surface acoustic wave resonator in a wide frequency range varies with the frequency is shown in FIG. Figure 5 As shown in Figure 2, the sound velocities of the SV mode and the TE mode are different, so the SV mode and the TE mode have different resonant frequencies and high-frequency spectra. Figure 4 and Figure 5 It can be seen that the high-frequency transmission band and the high-frequency forbidden band are different, and the acoustic isolation performance of the SV mode is different. In the TE mode, Figure 4 The magnitude of the transmission coefficient of the SAW resonator is compared to Figure 5 Increase by 5 dB; in SV mode, Figure 4 The magnitude of the transmission coefficient of the SAW resonator is compared to Figure 5 The improvement is 13 decibels. Therefore, by optimizing the material of the first high impedance layer 22, the high-frequency stray signal of the surface acoustic wave resonator can be suppressed or attenuated.

[0066] In some embodiments, Figure 6 , Figure 7 and Figure 8 As shown, the first high-impedance layer 22 includes a rotatable anisotropic material. The first low-impedance layer 21 includes an isotropic material or a rotatable anisotropic material, or the first low-impedance layer 21 includes a first low-impedance sublayer 211 and a second low-impedance sublayer 212 stacked in a thickness direction, the first low-impedance sublayer 211 includes an isotropic material or an anisotropic material, and the second low-impedance sublayer 212 includes a rotatable anisotropic material.

[0067] The Bragg reflection structure 2 may include a plurality of stacked Bragg reflection units, the film layer materials and film layer structures in different Bragg reflection units are the same, and the material type (such as isotropic material and / or anisotropic material) and film layer structure (such as a single-layer structure or a stacked structure) of the first low-impedance layer 21 and the first high-impedance layer 22 in each Bragg reflection unit may be the same or different.

[0068] like Figure 6As shown, the first low-impedance layer 21 and the first high-impedance layer 22 in each Bragg reflection unit are both single-layer structures, and the first low-impedance layer 21 includes an isotropic material, and the first high-impedance layer 22 includes a rotatable anisotropic material. Figure 7 As shown, the first low-impedance layer 21 and the first high-impedance layer 22 in each Bragg reflection unit are both single-layer structures, and the first low-impedance layer 21 and the first high-impedance layer 22 both include rotatable anisotropic materials. Figure 8 As shown, the first high-impedance layer 22 in each Bragg reflection unit is a single-layer structure, the first low-impedance layer 21 is a stacked structure, and the first low-impedance layer 21 includes a first low-impedance sublayer 211 and a second low-impedance sublayer 212 stacked. The first high-impedance layer 22 includes a rotatable anisotropic material, the first low-impedance sublayer 211 includes an isotropic material or an anisotropic material, and the second low-impedance sublayer 212 includes a rotatable anisotropic material.

[0069] In some embodiments, Figures 6 to 9 As shown, the Bragg reflection structure 2 further includes a binding layer 4 , and the binding layer 4 is located on a side of the Bragg reflection structure 2 close to the substrate 1 .

[0070] The thickness of the binding layer 4 can be at the atomic level (e.g., 1-5 nm). The binding layer 4 can serve as a connection interface between the Bragg reflection structure 2 and other film layers (e.g., substrate 1) of the surface acoustic wave resonator. The binding layer 4 does not affect the performance of other film layers (e.g., the first low-impedance layer 21 and the first high-impedance layer 22) of the Bragg reflection structure 2, making the performance of the surface acoustic wave resonator more stable and reliable.

[0071] In some embodiments, the binding layer 4 includes a second high-impedance layer or a second low-impedance layer, and the second high-impedance layer or the second low-impedance layer includes an isotropic material or an anisotropic material.

[0072] like Figures 6 to 9 As shown, when the bottom layer of the Bragg reflection unit is the first high impedance layer 22 and the top layer is the first low impedance layer 21, the binding layer 4 may include a second low impedance layer. The material of the second low impedance layer and the first low impedance layer 21 may be the same or different. When the bottom layer of the Bragg reflection unit is the first low impedance layer 21 and the top layer is the first high impedance layer 22, the binding layer 4 may include a second high impedance layer. The material of the second high impedance layer and the first high impedance layer 22 may be the same or different.

[0073] In this embodiment, the interface between the binding layer 4 and the adjacent first low-impedance layer 21 or first high-impedance layer 22 can be used as a reflection surface to reflect the clutter in the surface acoustic wave resonator.

[0074] In some embodiments, the first high-impedance layer 22 includes a plurality of high-impedance sub-layers stacked along the thickness direction, and the impedances of the plurality of high-impedance sub-layers are different.

[0075] The acoustic impedance of each high-impedance sublayer in the first high-impedance layer 22 is greater than the acoustic impedance of the low-impedance sublayer. The acoustic impedances of different high-impedance sublayers are different. For example, the acoustic impedances of the multiple high-impedance sublayers in the first high-impedance layer 22 may gradually decrease or increase from top to bottom.

[0076] In this embodiment, by setting a plurality of high impedance sub-layers with different impedances in the Bragg reflection structure 2, the high-frequency transmission band and the bandgap can be modulated while maintaining the transmission of the zero-order bandgap (i.e., the main bandgap) to suppress or attenuate the high-frequency stray signals of the surface acoustic wave resonator. The first high impedance layer 22 of the Bragg reflection structure 2 can be provided with a plurality of high impedance sub-layers, which expands the structural design of the Bragg reflection structure 2, thereby expanding the application of the Bragg reflection structure 2 in the surface acoustic wave resonator.

[0077] In some embodiments, Fig.10 As shown, the multiple high impedance sublayers include a first high impedance sublayer 221 and a second high impedance sublayer 222, the impedance of the first high impedance sublayer 221 is smaller than the impedance of the second high impedance sublayer 222, and the thickness ratio of the first high impedance sublayer 221 to the second high impedance sublayer 222 is 5%-30%.

[0078] The first high impedance layer 22 includes a first high impedance sublayer 221 and a second high impedance sublayer 222 having different acoustic impedances, and the acoustic impedance of the first high impedance sublayer 221 is less than that of the second high impedance sublayer 222. The acoustic impedance of the first low impedance layer 21 is less than that of the first high impedance sublayer 221 and the second high impedance sublayer 222. For example, the material of the first high impedance sublayer 221 may include aluminum, and the material of the second high impedance sublayer 222 may include tungsten, which has a higher acoustic impedance than aluminum. The material of the first low impedance layer 21 may include silicon dioxide.

[0079] The thickness of the first high impedance layer 22 and the first low impedance layer 21 directly affect the resonance frequency of the Bragg reflection structure 2. The first high impedance layer 22 includes two high impedance sub-layers. If the thickness of the two high impedance sub-layers is set to one-quarter of the wavelength of the surface acoustic wave, the total thickness of the first high impedance layer 22 will be mismatched. The first high impedance layer 22 does not meet the optimal thickness condition (that is, the total thickness of the first high impedance layer 22 is not one-quarter of the wavelength of the surface acoustic wave), so that the acoustic characteristics of the first high impedance layer 22 change in space, generating an acoustic effect, thereby affecting the acoustic isolation performance of the Bragg reflection structure 2. Therefore, in this embodiment, the total thickness of the first high impedance sub-layer 221 and the second high impedance sub-layer 222 is one-quarter of the wavelength, and the thickness ratio of the first high impedance sub-layer 221 to the second high impedance sub-layer 222 is adjusted to 5%-30%, so that the thickness of the first high impedance sub-layer 221 is less than that of the second high impedance sub-layer 222, which can avoid the reduction of the acoustic isolation performance of the main mode of the Bragg reflection structure 2, and can effectively control the high frequency band. For example, when the thickness of the first high-resistance sub-layer 221 is 10% of the total thickness of the first high-resistance layer 22 , the thickness of the second high-resistance sub-layer 222 is 90% of the total thickness of the first high-resistance layer 22 .

[0080] It should be noted that the stacking order of the first high impedance sublayer 221 and the second high impedance sublayer 222 is not specifically limited. For example, the first high impedance sublayer 221 can be used as the upper layer of the first high impedance layer 22, and the second high impedance sublayer 222 can be used as the lower layer of the first high impedance layer 22. The acoustic impedance of the upper high impedance sublayer in the first high impedance layer 22 is smaller than that of the lower high impedance sublayer. The amplitude variation curves of the transmission coefficient of the surface acoustic wave resonator in the wide frequency range in the TE and SV modes are shown as follows: Fig.11 and Fig.12 shown. Fig.11 The curve showing the amplitude of the transmission coefficient of the surface acoustic wave resonator in the TE mode varies with frequency over a wide frequency range. Fig.12 The curves showing the amplitude of the transmission coefficient of the surface acoustic wave resonator in the SV mode varies with frequency over a wide frequency range. Fig.11 and Fig.12 As shown, all bands have relatively high acoustic effects and low dispersion. The material of the first high impedance sublayer 221 is aluminum, which has a greater impact on the performance of the first high impedance layer 22. The step impedance at the interface between the first low impedance layer 21 and the second high impedance sublayer 222 is reduced, and the acoustic isolation performance is reduced. The main resonant mode and all high frequency modes of the Bragg reflection structure 2 produce the above-mentioned trade-off phenomenon.

[0081] For another example, the first high impedance sublayer 221 can be used as the lower layer of the first high impedance layer 22, and the second high impedance sublayer 222 can be used as the upper layer of the first high impedance layer 22. The acoustic impedance of the upper high impedance sublayer in the first high impedance layer 22 is greater than that of the lower high impedance sublayer. The amplitude variation curves of the transmission coefficient of the surface acoustic wave resonator in the TE and SV modes over a wide frequency range are shown as follows: Fig.13 and Fig.14 shown. Fig.13 The curve showing the amplitude of the transmission coefficient of the surface acoustic wave resonator in the TE mode varies with frequency over a wide frequency range. Fig.14 The curve of the amplitude of the transmission coefficient of the surface acoustic wave resonator in a wide frequency range in the SV mode is shown. In the case of tuning opportunities in the high frequency band, the acoustic effect generated in the main band gap is low. The high frequency mode of the Bragg reflection structure 2 is highly sensitive to the structure and material of the first high impedance layer 22. Fig.13 and Fig.14 As shown, at the main resonance frequency, the acoustic isolation performance of the transmission mode of the Bragg reflection structure 2 is almost the same.

[0082] In this embodiment, the total thickness of the first high impedance sublayer 221 and the second high impedance sublayer 222 is one quarter of a wavelength, and by adjusting the thickness ratio of the first high impedance sublayer 221 and the second high impedance sublayer 222, the transmission characteristics of the Bragg reflection structure 2 in the high frequency band are enhanced to further suppress or attenuate high frequency stray signals and improve the performance of the surface acoustic wave resonator.

[0083] In some embodiments, the high resistance sub-layer includes a soft metal, such as Mg (magnesium), Al (aluminum), or Ti (titanium).

[0084] In the Bragg reflection structure 2, soft metal is used as the material of the high impedance sublayer, so that the material hardness in the stacked structure of the high impedance sublayer in the first high impedance layer 22 is low, thereby releasing the constrained strain and residual stress in the stacked structure and reducing TCE (Thermal expansion coefficient) mismatch.

[0085] In some embodiments, Figures 15 to 17 As shown, the first low-impedance layer 21 is a single-layer structure or a stacked-layer structure.

[0086] The first low-impedance layer 21 and the first high-impedance layer 22 in the Bragg reflection structure 2 may both be a single layer or a stacked layer structure. The first low-impedance layer 21 may include one or more low-impedance sub-layers, and the first high-impedance layer 22 may include one or more high-impedance sub-layers. Fig.15As shown, the first low-impedance layer 21 and the first high-impedance layer 22 in the Bragg reflection structure 2 are both stacked structures. The first low-impedance layer 21 in the Bragg reflection structure 2 includes a plurality of low-impedance sub-layers stacked. The first high-impedance layer 22 includes a plurality of high-impedance sub-layers stacked. Fig.16 As shown, the first low-impedance layer 21 in the Bragg reflection structure 2 is a single-layer structure, and the first high-impedance layer 22 is a stacked structure. The first high-impedance layer 22 in the Bragg reflection structure 2 includes a plurality of high-impedance sub-layers stacked. Fig.17 As shown, the first low-impedance layer 21 in the Bragg reflection structure 2 is a stacked structure, and the first high-impedance layer 22 is a single-layer structure. The first low-impedance layer 21 in the Bragg reflection structure 2 includes a plurality of low-impedance sub-layers stacked together.

[0087] In some embodiments, Figure 2 , Figure 3 , Figures 6 to 8 , Fig.10 , Figures 15 to 17 and Fig. 22 As shown, the substrate 1 comprises a support layer, and the support layer comprises an isotropic material or an anisotropic material.

[0088] The support layer is located below the Bragg reflection structure 2, and the support layer provides physical support for the Bragg reflection structure 2, the first piezoelectric layer 31 and the first electrode layer 51. The acoustic impedance of the support layer is different depending on the material of the support layer. The material of the support layer is optimized so that the support layer has reliable thermal conductivity and the impedance mismatch between the support layer and the bottom layer of the Bragg reflection structure 2 is low.

[0089] Due to the body wave radiation and the propagation of the surface acoustic wave in the Bragg reflection structure 2, in-band spurious signals are generated in the surface acoustic wave resonator. There is a step impedance between the support layer and the Bragg reflection structure 2, and the step impedance can be used as an acoustic reflection boundary. Optimizing the material of the support layer can reduce the mechanism effect of the scattered wave, control the reflection and body wave excitation of the acoustic reflection boundary, control the acoustic impedance mismatch, suppress or attenuate the scattered wave radiation of the Bragg reflection structure 2, and thus suppress or attenuate the in-band spurious signals of the surface acoustic wave resonator.

[0090] In some embodiments, the support layer includes HTCC (High Temperature Co-fired Ceramic) ceramic.

[0091] The magnitude of the reflection coefficient of the surface acoustic wave resonator is related to the number of Bragg reflection units in the Bragg reflection structure 2 and / or the material type of the support layer. Fig.18As shown in FIG. 1 , when the Bragg reflection structure 2 includes a Bragg reflection unit and the materials of the supporting layer are copper, LTCC (Low Temperature Co-fired Ceramic), 42YXLT or HTCC, the curve of the amplitude of the reflection coefficient of the surface acoustic wave resonator in a wide frequency range is detected as a function of frequency. In this case, the Bragg reflection structure 2 cannot achieve reliable acoustic isolation, and the amplitude of the reflection coefficient of the surface acoustic wave resonator is negatively correlated with the isolation level. Fig.19 and Fig. 20 As shown, when the Bragg reflection structure 2 includes two and three Bragg reflection units respectively, and the materials of the supporting layer are copper, LTCC, 42YXLT and HTCC respectively, the curve of the amplitude of the reflection coefficient of the surface acoustic wave resonator in a wide frequency range is detected as a inverse of the frequency. Fig.21 for Fig. 20 Detailed diagram of in-band spurious in the structure. In both cases, the Bragg reflection structure 2 has reliable surface acoustic wave isolation characteristics. Due to body radiation, spurious waves are generated in the Bragg reflection structure 2. It should be noted that the Bragg reflection structure 2 in this embodiment has no mechanical loss and dielectric loss, and the generation or attenuation of spurious waves depends on the surface acoustic wave propagation characteristics of the laminated structure of the Bragg reflection structure 2.

[0092] In this embodiment, when the material of the support layer is HTCC ceramic, the stray signal generated by the body wave radiation in the Bragg reflection structure 2 can be reduced, thereby suppressing or attenuating the in-band stray signal of the surface acoustic wave resonator. It should be noted that the support layer may also include other materials, and the material of the support layer may be selected according to the film material and film structure of the Bragg reflection structure 2.

[0093] In some embodiments, Figures 1 to 3 , Figures 6 to 10 , Figures 15 to 17 and Fig. 22 As shown, the first piezoelectric layer 31 is a single-layer structure or a stacked-layer structure.

[0094] like Figures 1 to 3 , Figures 6 to 10 , Figures 15 to 17 As shown, the first piezoelectric layer 31 is a single-layer structure. Fig. 22 As shown, the first piezoelectric layer 31 is a laminated structure, and the first piezoelectric layer 31 may include a plurality of piezoelectric sub-layers stacked. The piezoelectric sub-layer located at the bottom of the first piezoelectric layer 31 may be used to suppress body wave radiation, generate high-frequency harmonics, improve temperature coefficients, and improve quality factors. The materials and orientations of each piezoelectric sub-layer are selected according to the functional requirements of the surface acoustic wave resonator in practical applications. The first piezoelectric layer 31 of the laminated structure is conducive to the generation of high-order harmonics and can be applied to high-frequency harmonic resonators.

[0095] In some embodiments, Fig. 9 As shown, the substrate 1 includes a second piezoelectric layer 32 and a second electrode layer 52. The second piezoelectric layer 32 is located on a side of the Bragg reflection structure 2 away from the first piezoelectric layer 31, and the second electrode layer 52 is located on a side of the second piezoelectric layer 32 away from the Bragg reflection structure 2.

[0096] In some embodiments, the second electrode layer 52 may include a plurality of electrode fingers, a third bus bar, and a fourth bus bar. The plurality of electrode fingers include third electrode fingers and fourth electrode fingers that are alternately and spaced apart along the first direction. The third electrode fingers and the fourth electrode fingers both extend along the second direction. The third bus bar and the fourth bus bar are respectively located on opposite sides of the plurality of electrode fingers along the first direction, and the third bus bar and the fourth bus bar both extend along the first direction. The third electrode finger is connected to the third bus bar, and the fourth electrode finger is connected to the fourth bus bar.

[0097] Among them, the number of the third electrode finger and the fourth electrode finger can be the same. The size (including length and width, etc.) of the third electrode finger and the fourth electrode finger can be the same. The materials of the third electrode finger and the fourth electrode finger can both include metal materials such as copper and aluminum. The third busbar and the fourth busbar can be used as connecting wires connecting adjacent resonators or connecting wires connecting the package side. The materials of the third busbar and the fourth busbar can both include metal materials such as copper and aluminum.

[0098] In this embodiment, the piezoelectric layer and the electrode layer are respectively arranged on the opposite sides of the Bragg reflection structure 2, which can form two resonators arranged in a stacked manner. When the surface acoustic wave resonator is applied to a surface acoustic wave filter, the size of the surface acoustic wave filter is reduced, and the miniaturization design of the surface acoustic wave filter is promoted. Through the design of the Bragg reflection structure 2, the two resonators arranged in a stacked manner can be coupled or insulated. The two coupled resonators can enhance the electromechanical coupling, which is conducive to the generation of high-order modes and the suppression of stray modes.

[0099] It should be noted that the surface acoustic wave resonator in the embodiment of the present application can be applied to electronic devices such as surface acoustic wave filters, duplexers, delay lines, frequency discriminators and modulators. For example, the surface acoustic wave resonator can be used as a component unit of a surface acoustic wave filter and is widely used in communication systems.

[0100] In summary, according to the surface acoustic wave resonator provided by the embodiment of the present application, a Bragg reflection structure 2 is provided in the surface acoustic wave resonator, and the Bragg reflection structure 2 includes a first high impedance layer 22 and a first low impedance layer 21 that are alternately stacked, and the thickness of the first high impedance layer 22 and the first low impedance layer 21 is one quarter of the wavelength of the surface acoustic wave, and the first high impedance layer 22 and the first low impedance layer 21 respectively include at least one of an isotropic material and an anisotropic material, so as to optimize the material and structure of the Bragg reflection structure 2, optimize the high-frequency transmission band and the forbidden band of the surface acoustic wave resonator, thereby suppressing or attenuating the out-of-band stray signals and high-frequency stray signals of the surface acoustic wave resonator, and further optimize the performance of the surface acoustic wave resonator. Moreover, by setting the first high impedance layer 22 as a plurality of high impedance sub-layers with different impedances, the high-frequency transmission band and the forbidden band are controlled while maintaining the main forbidden band, so as to further suppress or attenuate the high-frequency stray signals of the surface acoustic wave resonator. Furthermore, the support layer includes an isotropic material or an anisotropic material (such as HTCC ceramics) to suppress or attenuate the bulk wave of the Bragg reflection structure 2, so as to suppress or attenuate the in-band stray signal of the surface acoustic wave resonator.

[0101] Correspondingly, an embodiment of the present application further provides a surface acoustic wave filter, including the surface acoustic wave resonator in the above embodiment, which will not be described in detail here.

[0102] SAW resonators can be used as building blocks of SAW filters, which have the advantages of low acoustic velocity, low electromechanical losses, reliable power durability, and miniaturization, and can improve the effectiveness of wireless communications between multiple frequency bands and / or multiple devices.

[0103] In summary, according to the surface acoustic wave filter provided by the embodiment of the present application, a Bragg reflection structure 2 is set in the surface acoustic wave resonator, and the Bragg reflection structure 2 includes a first high impedance layer 22 and a first low impedance layer 21 that are alternately stacked, and the thickness of the first high impedance layer 22 and the first low impedance layer 21 is one quarter of the wavelength of the surface acoustic wave, and the first high impedance layer 22 and the first low impedance layer 21 respectively include at least one of an isotropic material and an anisotropic material, so as to optimize the material and structure of the Bragg reflection structure 2, optimize the high-frequency transmission band and the forbidden band of the surface acoustic wave resonator, thereby suppressing or attenuating the out-of-band stray signals and high-frequency stray signals of the surface acoustic wave resonator, and then suppressing or attenuating the out-of-band stray signals and high-frequency stray signals of the surface acoustic wave filter, improving the performance of the surface acoustic wave filter, and improving the effectiveness of wireless communication. Moreover, by setting the first high impedance layer 22 as a plurality of high impedance sub-layers with different impedances, the high-frequency transmission band and the forbidden band are controlled while maintaining the main forbidden band, so as to further suppress or attenuate the high-frequency stray signals of the surface acoustic wave resonator, and then further suppress or attenuate the high-frequency stray signals of the surface acoustic wave filter. Moreover, the support layer includes an isotropic material or anisotropic material (such as HTCC ceramics) to suppress or attenuate the body wave of the Bragg reflection structure 2 to suppress or attenuate the in-band stray signal of the surface acoustic wave resonator, thereby suppressing or attenuating the in-band stray signal of the surface acoustic wave filter.

[0104] Correspondingly, an embodiment of the present application further provides an electronic device, including the surface acoustic wave filter in the above embodiment, which will not be described in detail here.

[0105] In summary, according to the electronic device provided by the embodiment of the present application, by setting a Bragg reflection structure 2 in the surface acoustic wave resonator, the Bragg reflection structure 2 includes a first high impedance layer 22 and a first low impedance layer 21 that are alternately stacked, the thickness of the first high impedance layer 22 and the first low impedance layer 21 is one quarter of the wavelength of the surface acoustic wave, and the first high impedance layer 22 and the first low impedance layer 21 respectively include at least one of an isotropic material and an anisotropic material, so as to optimize the material and structure of the Bragg reflection structure 2, optimize the high-frequency transmission band and the forbidden band of the surface acoustic wave resonator, thereby suppressing or attenuating the out-of-band stray signals and high-frequency stray signals of the surface acoustic wave resonator, and further optimize the performance of the surface acoustic wave resonator. Moreover, by setting the first high impedance layer 22 as a plurality of high impedance sub-layers with different impedances, the high-frequency transmission band and the forbidden band are controlled while maintaining the main forbidden band, so as to further suppress or attenuate the high-frequency stray signals of the surface acoustic wave resonator. Furthermore, the support layer includes an isotropic material or an anisotropic material (such as HTCC ceramics) to suppress or attenuate the bulk wave of the Bragg reflection structure 2, so as to suppress or attenuate the in-band stray signal of the surface acoustic wave resonator.

[0106] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more.

[0107] In the description of the present application, “plurality” means two or more.

[0108] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0109] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A surface acoustic wave resonator, characterized in that: include: substrate; A Bragg reflection structure, located on one side of the substrate in a thickness direction, the Bragg reflection structure comprising a first high-impedance layer and a first low-impedance layer alternately stacked along the thickness direction, the thickness of the first high-impedance layer and the first low-impedance layer are respectively one-quarter wavelength, and the first high-impedance layer and the first low-impedance layer respectively comprise at least one of an isotropic material and an anisotropic material; A first piezoelectric layer is located on a side of the Bragg reflection structure away from the substrate; The first electrode layer is located on a side of the first piezoelectric layer away from the Bragg reflection structure.

2. The surface acoustic wave resonator according to claim 1, characterized in that: The first high impedance layer comprises a rotatable anisotropic material; The first low-impedance layer includes an isotropic material or a rotatable anisotropic material, or the first low-impedance layer includes a first low-impedance sublayer and a second low-impedance sublayer stacked along the thickness direction, the first low-impedance sublayer includes an isotropic material or an anisotropic material, and the second low-impedance sublayer includes a rotatable anisotropic material.

3. The surface acoustic wave resonator according to claim 1, characterized in that: The Bragg reflection structure further includes a binding layer; The binding layer is located on a side of the Bragg reflection structure close to the substrate.

4. The surface acoustic wave resonator according to claim 3, characterized in that: The binding layer includes a second high-impedance layer or a second low-impedance layer, and the second high-impedance layer or the second low-impedance layer includes an isotropic material or an anisotropic material.

5. The surface acoustic wave resonator according to claim 1, characterized in that: The first high-impedance layer includes a plurality of high-impedance sub-layers stacked along the thickness direction, and the impedances of the plurality of high-impedance sub-layers are different.

6. The surface acoustic wave resonator according to claim 5, characterized in that: The plurality of high impedance sublayers include a first high impedance sublayer and a second high impedance sublayer, the impedance of the first high impedance sublayer is smaller than the impedance of the second high impedance sublayer, and a thickness ratio of the first high impedance sublayer to the second high impedance sublayer is 5%-30%.

7. The surface acoustic wave resonator according to claim 5, characterized in that: The high-resistance sublayer includes a soft metal including Mg, Al or Ti.

8. The surface acoustic wave resonator according to claim 1, characterized in that: The first low-impedance layer is a single-layer structure or a stacked-layer structure.

9. The surface acoustic wave resonator according to any one of claims 1 to 8, characterized in that: The substrate includes a support layer including an isotropic material or an anisotropic material.

10. The surface acoustic wave resonator according to claim 9, characterized in that: The support layer includes HTCC ceramic.

11. The surface acoustic wave resonator according to any one of claims 1 to 8, characterized in that: The first piezoelectric layer is a single-layer structure or a stacked-layer structure.

12. The surface acoustic wave resonator according to any one of claims 1 to 8, characterized in that: The substrate includes a second piezoelectric layer and a second electrode layer; The second piezoelectric layer is located on a side of the Bragg reflection structure away from the first piezoelectric layer, and the second electrode layer is located on a side of the second piezoelectric layer away from the Bragg reflection structure.

13. A surface acoustic wave filter, characterized in that: The invention comprises a surface acoustic wave resonator as claimed in any one of claims 1 to 12.

14. An electronic device, characterized in that: The invention comprises a surface acoustic wave filter as claimed in claim 13.

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