Surface acoustic wave resonator and communication equipment

Abstract

The utility model relates to a surface acoustic wave resonator and communication equipment. The surface acoustic wave resonator comprises a piezoelectric film, an interdigital unit and a speed reduction unit. The interdigital ring energy unit is located on the piezoelectric film. The interdigital unit comprises a plurality of electrode fingers which are arranged at intervals. The speed reduction unit is located in the piezoelectric film. The speed reduction unit comprises at least one first groove used for reducing the propagation speed of the surface acoustic wave. And at least one part of the first groove is located in an area between any two adjacent electrode fingers, so that the wavelength of the surface acoustic wave resonator is reduced under the condition that the target resonant frequency of the surface acoustic wave is kept unchanged. The resonator is arranged based on the speed reduction unit, miniaturization can be effectively achieved under the condition that the working performance is not affected, the overall structure is flexible and diversified, and the miniaturization requirement is met. The communication equipment is provided with the resonator, so that the miniaturization is synchronously realized, and the application scene is expanded.

Description

Technical Field

[0001] This application relates to the field of resonator technology, and in particular to a surface acoustic wave resonator and communication device. Background Technology

[0002] Surface acoustic wave (SAW) resonators are microelectronic devices that utilize sound waves propagating on the surface of piezoelectric materials to achieve signal processing and frequency control. They offer advantages such as low cost, high reliability, and ease of integration, and have found wide application in wireless communication, sensors, microfluidics, photonics, and quantum information processing. For example, SAW resonators play a crucial role in signal separation and filtering in wireless communication.

[0003] With the rapid development of modern electronic technology, especially the rise of 5G and 6G communication, the Internet of Things, and smart wearable devices, there are strict requirements for the space occupied by SAW resonators and the integration of communication equipment, leading to an increasing demand for miniaturization of SAW resonators and communication equipment.

[0004] Therefore, how to provide a surface acoustic wave resonator and communication device to meet the miniaturization requirements of various application fields has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] Therefore, it is necessary to provide a surface acoustic wave (SAW) resonator to address the increasing demand for miniaturization in various application fields. The SAW resonator includes:

[0006] piezoelectric thin film;

[0007] Interdigitated units are located on the piezoelectric film, and the interdigitated units include a plurality of spaced-apart electrode fingers;

[0008] A deceleration unit, located in the piezoelectric film, includes at least one first groove for reducing the propagation speed of surface acoustic waves, and at least a portion of the first groove is located in the region between any two adjacent electrode fingers, so as to reduce the wavelength of the surface acoustic wave resonator while keeping the target resonant frequency of the surface acoustic wave unchanged.

[0009] In one embodiment, the preset parameters of the first groove are configured to reduce the propagation speed of surface acoustic waves, and the preset parameters include at least one of depth and width.

[0010] In one embodiment, the first groove opens from the side of the piezoelectric film near the interdigital unit, and the depth of the first groove is less than or equal to the thickness of the piezoelectric film in the direction from the piezoelectric film to the deceleration unit.

[0011] In one embodiment, the percentage value between the depth of the first groove and the thickness of the piezoelectric film ranges from 10% to 50%.

[0012] In one embodiment, the first groove is located in the region between two adjacent electrode fingers, and in the arrangement direction of the plurality of electrode fingers, the width of the first groove is less than or equal to the distance between any two adjacent electrode fingers.

[0013] In one embodiment, the percentage of the width of the first groove to the distance between any two adjacent electrode fingers ranges from 5% to 80%.

[0014] In one embodiment, the deceleration unit includes a plurality of the first grooves, with at least one of the first grooves in the region between any two adjacent electrode fingers.

[0015] In one embodiment, the surface acoustic wave resonator further includes at least one reflective grating unit located on one side of the interdigitated finger unit in the arrangement direction of the plurality of electrode fingers, and the reflective grating unit includes a plurality of spaced reflective grating strips.

[0016] In one embodiment, the deceleration unit further includes at least one second groove located between any two adjacent reflective gratings.

[0017] In one embodiment, the extension direction of the first groove is parallel to the extension direction of the electrode finger, and the cross-sectional shape of the first groove is at least one of a rectangle, a trapezoid, and an arc in the extension direction of the first groove.

[0018] In one embodiment, the metallization rate of the surface acoustic wave resonator is in the range of 0.3 to 0.7, the aperture of the surface acoustic wave resonator is in the range of 10λ to 50λ, and the thickness of the electrode fingers is in the range of 0.025λ to 0.15λ, where λ is the wavelength of the surface acoustic wave resonator.

[0019] A communication device is also provided, the communication device including the surface acoustic wave resonator as described above.

[0020] The aforementioned surface acoustic wave (SAW) resonator, based on the setting of the deceleration unit, reduces the propagation speed of SAW waves, thereby achieving miniaturization of the SAW resonator without changing the target resonant frequency. Furthermore, by adjusting the structure (including width and depth) of the first groove in the deceleration unit, the overall structure of the SAW resonator can be flexibly diversified.

[0021] The aforementioned communication device, having the SAW resonator, can be miniaturized simultaneously based on the miniaturization of the SAW resonator, thus expanding its application in the field of miniaturization technology. Attached Figure Description

[0022] Figure 1 A top view of the interdigitated unit in the surface acoustic wave resonator provided in the embodiments of this application;

[0023] Figure 2 This is a schematic diagram of the structure of a surface acoustic wave resonator in a related technology when the electrode fingers are composed of a stacked structure.

[0024] Figure 3 This application provides a schematic diagram comparing the structure of the piezoelectric thin film in the surface acoustic wave resonator before and after the thickness is reduced.

[0025] Figure 4 A cross-sectional schematic diagram of a surface acoustic wave resonator provided in an embodiment of this application when a first groove is provided;

[0026] Figure 5 Another cross-sectional view of the surface acoustic wave resonator provided in the embodiment of this application when a first groove is provided;

[0027] Figure 6 A schematic diagram illustrating the effect of the surface acoustic wave propagation speed of the surface acoustic wave resonator provided in this embodiment of the application changing with the depth of the first groove;

[0028] Figure 7 A schematic diagram illustrating the effect of the propagation speed of the surface acoustic wave in the surface acoustic wave resonator provided in this embodiment of the application changing with the depth and width of the first groove;

[0029] Figure 8 Admittance curves of a surface acoustic wave resonator with different structural parameters in the first groove provided in the embodiments of this application;

[0030] Figure 9 A cross-sectional schematic diagram of a surface acoustic wave resonator with an intermediate layer provided in an embodiment of this application;

[0031] Figure 10 This is a top view of a surface acoustic wave resonator with a reflective grating provided in an embodiment of this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 10 / 10a - Piezoelectric thin film; 20 - Interdigitated unit; 21 / 21a - Electrode finger; 22 - Busbar; 23 - Virtual finger; 30 - First groove; 40 - Reflective grating unit; 41 - Reflective grating bar; 50 - Supporting substrate; 60 - Intermediate layer. Detailed Implementation

[0034] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0035] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0040] Please see Figure 1 , Figure 1 A partial top view schematic diagram of a surface acoustic wave (SAW) resonator is shown. Typically, a SAW resonator comprises components located on a piezoelectric thin film (…). Figure 1 The interdigitated unit 20 (not shown) is located above the piezoelectric film. The interdigitated unit 20 includes a pair of busbars 22 and a plurality of electrode fingers 21 spaced apart and staggered between the pair of busbars 22. The interdigitated unit 20 converts electrical signals into surface acoustic waves (or converts surface acoustic waves into electrical signals), and the surface acoustic waves (hereinafter referred to as "sound waves") propagate in the piezoelectric film. The sound wave frequency is controlled by adjusting the structure of the interdigitated unit.

[0041] To address the technical problem mentioned in the background regarding the unmet need for miniaturization of SAW resonators, a related technology proposes a SAW resonator structure constructed of heavy metals. This SAW resonator, while meeting the target resonant frequency, can achieve miniaturization to a certain extent. Please refer to [link / reference]. Figure 2 , Figure 2 This illustrates the SAW resonator structure along... Figure 1A cross-sectional view at point I-I'. The electrode fingers 21a are composed of stacked metal layers, including a bottom electrode (unlabeled) and a top electrode (unlabeled). The bottom electrode is made of heavy metals such as platinum, tungsten, and molybdenum, while the top electrode is made of Al. Analysis of the resonator's structure suggests that the design of the metal-stacked electrode fingers 21a reduces the propagation speed of surface acoustic waves (SAWs), thereby reducing the spacing between adjacent electrode fingers 21a and consequently decreasing the wavelength of the SAW resonator, thus achieving miniaturization.

[0042] For a SAW resonator, its target resonant frequency fr, wavelength λ (λ is twice the distance p between two adjacent electrodes), and sound velocity v satisfy the following relationship: Since λ = 2p, to meet the miniaturization requirements of SAW resonators, the spacing between adjacent electrode fingers in the original structural design can be adaptively reduced based on the decrease in sound velocity, thereby achieving overall miniaturization of the SAW resonator while maintaining the target resonant frequency. For example, in SAW resonators made of LiTaO3 piezoelectric thin film, the sound velocity is typically between 3800 m / s and 4000 m / s. If the sound velocity is reduced by several percentage points, the spacing between adjacent electrode fingers can be adaptively reduced by several percentage points, significantly reducing the overall volume of the SAW resonator.

[0043] Based on the above analysis, we attempted to reduce the thickness of the piezoelectric film used for sound wave propagation. Please refer to [link to relevant documentation]. Figure 3 , Figure 3 A SAW resonator is shown along Figure 1 A cross-sectional view at I-I' is shown, comparing the structural simplification before and after thinning the piezoelectric film. Without changing the structure of electrode fingers 21, by reducing the thickness of the piezoelectric film 10a in this SAW resonator, the propagation speed of sound is reduced, and the spacing between adjacent electrode fingers is correspondingly reduced, thereby achieving miniaturization of the SAW resonator while maintaining the target resonant frequency. However, actual verification revealed that simply reducing the thickness of the piezoelectric film 10a has little effect on reducing the sound velocity (see reference...). Figure 6 and Figure 7 This limits the size reduction of SAW resonators and may still be insufficient to meet miniaturization requirements.

[0044] Please see Figure 1 and Figure 4 , Figure 4 The SAW resonator provided in this application embodiment is shown in the image. Figure 1A cross-sectional schematic diagram at point I-I'. Embodiments of this application provide a SAW resonator, including a piezoelectric film 10, interdigital units 20, and a deceleration unit (not shown). Typically, a SAW resonator typically includes two separately arranged interdigital units 20.

[0045] Specifically, the interdigitated unit 20 is located on the piezoelectric film 10, and the interdigitated unit 20 includes a plurality of spaced-apart electrode fingers 21. The deceleration unit is located within the piezoelectric film 10. Figure 4 As shown, the deceleration unit includes at least one first groove 30 for reducing the propagation speed of surface acoustic waves (SAWs). At least a portion of the first groove 30 is located in the region between any two adjacent electrode fingers 21. This reduces the wavelength (λ) of the SAW resonator while maintaining the target resonant frequency of the SAW. That is, the SAW resonator provided in this embodiment has the same resonant frequency (i.e., target resonant frequency) as a conventional resonator without a deceleration unit, but a different wavelength. The target resonant frequency can be considered as the requirement of the SAW resonator for its resonant frequency in the actual application scenario.

[0046] In some embodiments, the preset parameters of the first groove 30 are configured to reduce the propagation speed of surface acoustic waves, and the preset parameters include at least one of width and depth. That is, by adjusting the width and / or depth of the first groove 30, the effect of reducing the propagation speed of surface acoustic waves can be achieved.

[0047] In some embodiments, such as Figure 4 and Figure 5 As shown, the first groove 30 is located in the region between two adjacent electrode fingers 21 (i.e., it does not extend below any electrode finger 21), and in the arrangement direction of the plurality of electrode fingers 21 ( Figure 4 and Figure 5 In the X direction shown, the width of the first groove 30 is less than or equal to the distance between any two adjacent electrode fingers 21. For example, as Figure 4 As shown, the width b of the first groove 30 is less than the distance a between any two adjacent electrode fingers 21. For example, as... Figure 5 As shown, the width b of the first groove 30 is equal to the distance a between any two adjacent electrode fingers 21. Furthermore, the first groove 30 is equidistant from the distance between the first and second adjacent electrode fingers 21 (i.e., the first groove 30 is centrally located between the two adjacent electrode fingers 21), which can increase the uniformity and symmetry of the overall structure of the SAW resonator, avoiding the introduction of parasitic effects that could affect the operating performance of the SAW resonator, such as causing a shift in the target resonant frequency.

[0048] In some embodiments, in the arrangement direction of the plurality of electrode fingers 21, the percentage value of the width of the first groove 30 to the distance between any two adjacent electrode fingers 21 ranges from 5% to 80% (including endpoint values), for example, it can be 10%, 30%, 50%, or 60%. The above percentage values ​​are preferred ranges summarized by comprehensively considering the miniaturization requirements, structural reliability, and manufacturing costs of the SAW resonator, which can achieve significant wavelength reduction (to meet miniaturization requirements) while avoiding device performance degradation and increased manufacturing difficulty and cost. Of course, if only the factor of reducing the sound velocity achieved by the first groove 30 is considered, the percentage value of the width of the first groove 30 to the distance between any two adjacent electrode fingers 21 can be less than 5% or greater than 80%, and even the width of the first groove 30 can be greater than the distance between any two adjacent electrode fingers 21.

[0049] Specifically, since the first groove 30 is located between two adjacent electrode fingers, after the interdigitated unit 20 is fabricated, the first groove 30 is fabricated based on the area between two adjacent electrode fingers 21. Due to limitations in photolithography precision, it may be impossible to fabricate a first groove 30 with a smaller width, or it may affect the width consistency between different first grooves 30, or it may require high-precision photolithography and etching techniques, significantly increasing the fabrication cost of the SAW resonator. When the width of the first groove 30 is large, for example, if the width of the first groove 30 is equal to the spacing between two adjacent electrode fingers 21, the area of ​​the piezoelectric film 10 located between adjacent electrode fingers 21 is reduced. If the width of the electrode fingers 21 themselves is small, this may cause mechanical deformation or breakage, which is detrimental to the reliability of the SAW resonator.

[0050] In some embodiments, such as Figure 4 and Figure 5 As shown, the first groove 30 opens from the side of the piezoelectric film 10 near the interdigital unit 20, and in the direction from the piezoelectric film 10 to the deceleration unit ( Figure 4 and Figure 5 In the Z direction shown, the depth d of the first groove 30 is less than or equal to the thickness of the piezoelectric film 10. The first groove 30 opens from the side of the piezoelectric film 10 near the interdigital unit 20, meaning that the first groove 30 penetrates the upper surface of the piezoelectric film 10. Besides being simple and convenient to manufacture, since acoustic surfaces mainly propagate along the surface of the piezoelectric film 10, the aforementioned first groove 30 can effectively reduce the sound velocity.

[0051] In some embodiments, the deceleration unit includes a plurality of first grooves 30, with at least one first groove 30 present in the region between any two adjacent electrode fingers 21. The structures of the plurality of first grooves 30 may be the same or different. When the structures of the plurality of first grooves 30 are different, although it may lead to discontinuities in the direction of sound wave propagation, increasing the possibility of sound wave energy scattering, it can still achieve the effect of reducing the speed of sound and is also suitable for miniaturizing the resonator. The phrase "at least one first groove 30 present in the region between any two adjacent electrode fingers 21" includes the following two cases: each region between every two adjacent electrode fingers 21 has a first groove 30; or, a portion of the region between two adjacent electrode fingers 21 has a first groove 30, while another portion of the region between two adjacent electrode fingers 21 does not have a first groove 30.

[0052] Furthermore, the region between any two adjacent electrode fingers 21 may have only one first groove 30, or it may have two or more first grooves 30 (forming a first groove group). Even further, the multiple first grooves 30 in the first groove group between any two adjacent electrode fingers 21 may be arranged in the same direction as the multiple electrode fingers 21. Figure 1 The electrodes are arranged in the X direction shown in the diagram, or in the extension direction of the electrode fingers 21. Figure 1 The first grooves are arranged in the Y direction (as shown in the diagram). Furthermore, in the latter case, any two adjacent first groove groups can be aligned or staggered. The staggered arrangement, compared to the aligned arrangement, can reduce the difference in the sound wave propagation path, thus ensuring the performance of the SAW resonator.

[0053] In some embodiments, while maintaining a consistent structure, the multiple first grooves 30 are arranged periodically to increase the uniformity and symmetry of the overall structure of the SAW resonator. In some embodiments, the metallization rate of the SAW resonator ranges from 0.3 to 0.7 (inclusive of endpoints), and can be 0.4, 0.5, or 0.6. The aperture of the SAW resonator ranges from 10λ to 50λ (inclusive of endpoints), and can be 20λ, 30λ, or 40λ. The thickness of the electrode finger 21 ranges from 0.025λ to 0.15λ (inclusive of endpoints), and can be 0.05λ or 0.10λ. Here, λ is the wavelength of the SAW resonator. The metallization rate refers to the ratio of the width of the electrode finger 21 to the spacing between two adjacent electrode fingers 21 (i.e., the period of the electrode finger 21). The aperture refers to the width of the overlapping portion of two adjacent electrode fingers 21 in the arrangement direction of the multiple electrode fingers 21 (the direction of propagation of the surface acoustic wave).

[0054] In some embodiments, the extending direction of the first groove 30 is parallel to the extending direction of the electrode finger 21, and the cross-sectional shape of the first groove 30 in the extending direction of the first groove 30 is at least one of a rectangle, a trapezoid, and an arc. For example, as Figure 1 As shown, the cross-sectional shape of the first groove 30 is rectangular, while in other embodiments, the cross-sectional shape of the first groove 30 may also be trapezoidal or arc-shaped.

[0055] In this embodiment, a speed-reducing unit is provided in the piezoelectric film 10. The speed-reducing unit includes at least one first groove 30, at least a portion of which is located in the region between any two adjacent electrode fingers 21. Based on the design of the speed-reducing unit, at least a portion of the structure in the piezoelectric film 10 located between two adjacent electrode fingers 21 is etched. On the one hand, the provision of the first groove 30 can reduce the thickness of the corresponding portion of the piezoelectric film 10, thereby reducing the sound velocity. On the other hand, the first groove 30 can also change the reflection efficiency of surface acoustic waves between two adjacent electrode fingers 21, thereby further effectively reducing the sound velocity.

[0056] Typically, for a conventional SAW resonator, the reflection coefficient is mainly affected by the spacing between two adjacent interdigital fingers 21. Here, by setting the first groove 30, the reflection coefficient can be changed, thereby changing the sound velocity. Specifically, for a SAW resonator, its target resonant frequency fr, reference velocity Vr, reflection coefficient k of the interdigital unit pair (including two separately arranged interdigital units 20), and resonator wavelength λ satisfy the following: Wherein, the reference velocity Vr refers to the propagation speed of the sound wave within the piezoelectric film 10 when there are no other structures on the surface (i.e., the velocity when the piezoelectric film 10 is a free surface). When a first groove 30 is formed in the region between two adjacent electrode fingers 21, the reflection coefficient k increases because the first groove 30 has a reflector-like effect. Further, based on the above formula, it can be seen that the target resonant frequency fr decreases as the reflection coefficient k increases. It is known that for the interdigitated unit 20 with a specific structure, the wavelength λ is a constant. Therefore, when the target resonant frequency fr decreases as the reflection coefficient k increases, the sound velocity v will inevitably decrease accordingly. To avoid the decrease in the target resonant frequency fr, other parameters (e.g., the structure of the deceleration unit and the first groove 30) can be adjusted to offset the effect of the change in reflection coefficient k on the resonant frequency fr, thereby maintaining the target resonant frequency unchanged. That is, the arrangement of the first groove 30 simultaneously regulates its influence on both the reflection coefficient k and the propagation velocity v, and the synergistic change of the two offsets the influence on fr.

[0057] Please see Figure 6 , Figure 6This illustration shows a comparison of the effects of thinning the piezoelectric film in a conventional SAW resonator and the etching depth of the first groove in this embodiment on the surface acoustic wave propagation velocity. Figure 6 The structural parameters of the middle part are as follows: piezoelectric film 10: thickness is 900nm (0.225λ), material is 42°YX-LiTaO3; resonator: wavelength λ is 4μm, metallization is 0.5, electrode finger 21 spacing is 2μm, electrode finger 21 thickness is 400nm (0.1λ).

[0058] based on Figure 6 It can be seen that when the piezoelectric film 10a in a conventional SAW resonator is thinned, although the sound velocity gradually decreases with the thinning of the piezoelectric film 10a, the reduction effect is not significant. When the thickness of the thinned portion of the piezoelectric film 10 gradually increases from 0 to 850 nm, the sound velocity only decreases from 3800 m / s to 3500 m / s. That is, when the piezoelectric film 10 is basically completely etched, the sound velocity only decreases by 7.89%. However, when the first groove 30 is formed in the piezoelectric film 10, as the depth of the first groove 30 increases from 0 to 850 nm, the sound velocity decreases from 3800 m / s to 1700 m / s, a reduction of about 55%. Among them, when the depth of the first groove 30 is 200 nm, the sound velocity has already decreased by about 11%, which is significantly greater than 7.89%. Therefore, by controlling the (etching) depth of the first groove 30, the degree of sound velocity reduction can be effectively controlled, thereby correspondingly reducing the spacing between two adjacent electrode fingers 21 to meet the miniaturization requirements of the resonator.

[0059] In some embodiments, the percentage value between the depth of the first groove 30 and the thickness of the piezoelectric film 10 ranges from 10% to 50% (inclusive), and can be 20%, 30%, or 40%. The aforementioned percentage values ​​represent a trade-off range that comprehensively considers the miniaturization requirements, structural reliability, and fabrication feasibility of the SAW resonator, achieving significant wavelength reduction (to meet miniaturization needs) while avoiding uncontrollable degradation of device performance. Of course, if only the reduction in sound velocity achieved by the first groove 30 is considered, the percentage between the first groove 30 and the thickness of the piezoelectric film 10 can be less than 10% or greater than 50%. Therefore, the specific depth of the first groove 30 is adjusted based on the application scenario of the resonator to optimize its miniaturization and operational reliability.

[0060] Specifically, based on Figure 6It is known that when the depth of the first groove 30 is small (i.e., the percentage value between the depth of the first groove 30 and the thickness of the piezoelectric film 10 is small), for example, when the depth of the first groove 30 is 50 nm, the percentage value between it and the thickness of the piezoelectric film 10 (900 nm) is approximately 5.55%, the sound velocity of the SAW resonator is less different from that of a SAW resonator with a conventional structure. This means that the speed-reduction unit's effect on reducing sound velocity still needs further improvement. Furthermore, the small depth of the first groove 30 makes it difficult to control the etching uniformity during fabrication, potentially leading to significant depth differences between different areas within the same first groove 30 or between multiple first grooves 30. Controlling the lower limit of the aforementioned percentage value to 10% helps increase process tolerance. Since current mainstream etching processes typically achieve a depth accuracy of ±5%, the mass production requirements of the SAW resonator with the speed-reduction unit can be met based on mainstream etching processes without requiring higher-precision etching processes or equipment. When the depth of the first groove 30 is large (i.e., the percentage value between the depth of the first groove 30 and the thickness of the piezoelectric film 10 is large), although it can effectively reduce the sound velocity to make the SAW resonator more miniaturized, this will result in a relatively thin portion of the piezoelectric film 10 located below the first groove 30. This may lead to stress concentration during subsequent structural layer manufacturing or use, making it prone to cracking or even crack propagation, affecting structural stability. In addition, it may also cause a decrease in the mechanical stiffness of the sound wave propagation path, resulting in a shift in the target resonant frequency, thereby causing uncontrollable degradation of the performance of the SAW resonator.

[0061] Please see Figure 7 , Figure 7 This illustration shows a comparison of the effects of thinning the piezoelectric film in a conventional SAW resonator and the etching depth and width of the first groove in this embodiment on the surface acoustic wave propagation velocity. Figure 7 The different percentages represent the percentage of the width of the first groove 30 to the distance between two adjacent electrode fingers 21. Based on Figure 7 As can be seen from the content, besides the depth of the first groove 30 affecting the sound velocity, the sound velocity also varies depending on the width of the first groove 30. For example, when the first groove 30 has the same depth, the sound velocity decreases as the width of the first groove 30 increases. Therefore, both the depth and width of the first groove 30 can be designed simultaneously to achieve miniaturization of the SAW resonator.

[0062] Please see Figure 8 , Figure 8The diagram shows a comparison of admittance curves for a conventional SAW resonator with those for three different first grooves with different parameters provided in this application. Figure 8 In the conventional structure, the deceleration unit is not present, and its wavelength is 4.6 μm. The SAW resonators corresponding to curves A through C all contain the deceleration unit, and their wavelengths are all 4.0 μm. The only difference lies in the structure of the first groove 30. Specifically, in the SAW resonator corresponding to curve A: the width of the first groove 30 is 70% of the distance between two adjacent electrode fingers 21 (i.e., a ratio of 7:10), and the depth of the first groove 30 is 250 nm. In the SAW resonator corresponding to curve B: the width of the first groove 30 is 30% of the distance between two adjacent electrode fingers 21 (i.e., a ratio of 3:10), and the depth of the first groove 30 is 300 nm. In the SAW resonator corresponding to curve C: the width of the first groove 30 is 10% of the distance between two adjacent electrode fingers 21 (i.e., a ratio of 1:10), and the depth of the first groove 30 is 350 nm. Figure 8 The following information can be obtained:

[0063] 1) When the SAW resonator has a conventional structure (i.e., the SAW resonator does not have the first groove 30), its target resonant frequency is approximately 800MHz when the wavelength of the SAW resonator is 4.6μm. However, by incorporating the first groove 30 into the SAW resonator and through reasonable adjustments to the structure of the first groove 30, a target resonant frequency of 800MHz can be achieved when the wavelength of the SAW resonator is 4.0μm (i.e., the target resonant frequency is essentially not shifted). Furthermore, compared to the SAW resonator with the first groove 30 having three different structural sizes, the wavelength of the conventional SAW resonator is reduced by approximately 15%, thereby achieving a corresponding reduction in the size of the SAW resonator. Therefore, based on the configuration of the first groove 30, the velocity of sound can be flexibly controlled without changing the target resonant frequency to meet the normal operating performance of the resonator, thereby reducing the wavelength of the resonator (by approximately 15%) and meeting the requirements for miniaturization applications.

[0064] 2) When a SAW resonator has a first groove 30, SAW resonators with different structural parameters of the first groove 30 can have essentially the same target resonant frequency. That is, the structures of SAW resonators corresponding to the same target resonant frequency do not need to be strictly identical. Therefore, Figure 8It was also demonstrated that, without changing the target resonant frequency and achieving miniaturization, the structure of the first groove 30 is flexible and versatile, making the overall structure of the SAW resonator flexible and diverse. In practical applications, the first groove 30 with a suitable structure can be designed based on application needs. For example, the etching depth of the first groove 30 can be appropriately reduced while the width of the first groove 30 is increased, which can reduce the manufacturing difficulty of the first groove 30.

[0065] In some embodiments, in the extending direction of the first groove 30, the length of the first groove 30 is equal to the spacing between a pair of busbars 22, or the length of the first groove 30 is equal to the aperture of the SAW resonator, or the length of the first groove 30 is between the aperture of the SAW resonator and the spacing between a pair of busbars 22.

[0066] In some embodiments, please refer to 9. Figure 9 A cross-sectional schematic diagram of the SAW resonator is shown. The SAW resonator also includes a supporting substrate 50 and an intermediate layer 60 located on the supporting substrate 50. The piezoelectric thin film 10 is located on the side of the intermediate layer 60 away from the supporting substrate 50. The supporting substrate 50 is made of Si, and the intermediate layer 60 is made of SiO2. The intermediate layer 60 provides excellent characteristics such as less leakage of elastic wave energy in the direction of the supporting substrate 50, while also exhibiting a higher electromechanical coupling coefficient and a higher quality factor. Therefore, the resonator with the multilayer structure performs better than a conventional resonator (without the intermediate layer 60).

[0067] In some embodiments, please refer to Figure 10 , Figure 10 The illustration shows a top view of a surface acoustic wave (SAW) resonator with a reflective grating provided in an embodiment of this application. The SAW resonator further includes at least one reflective grating unit 40. In the arrangement direction of the plurality of electrode fingers 21, the reflective grating unit 40 is located on one side of the interdigitated finger unit 20. The reflective grating unit 40 includes a plurality of spaced reflective grating strips 41.

[0068] In some embodiments, the deceleration unit further includes at least one second groove (not shown) located between any two adjacent reflective grid strips 41. Further, the deceleration unit includes multiple second grooves, such that in each reflective grid unit 40, at least one second groove is present between any two adjacent reflective grid strips 41. Since the overall reflection coefficient of the SAW resonator includes the effect of the presence of the reflective grid, synchronously providing the second grooves in the reflective grid can also reduce the sound velocity to a certain extent, thereby contributing to the miniaturization of the resonator.

[0069] In some embodiments, the first groove 30 in the deceleration unit has the same structure as the second groove, wherein the same structure includes the same width, depth and cross-sectional shape, which facilitates precise control of the sound velocity.

[0070] In some embodiments, such as Figure 10 As shown, the interdigitated unit 20 also includes a plurality of virtual fingers 23, which are arranged in a one-to-one correspondence with the plurality of electrode fingers 21. The virtual fingers 23 can optimize the performance of the resonator, for example, by increasing the symmetry of the interdigitated unit 20 to improve the resonant characteristics of the resonator.

[0071] The surface acoustic wave (SAW) resonator of this application embodiment, based on the setting of the deceleration unit, can achieve miniaturization of the SAW resonator without changing the target resonant frequency. Furthermore, based on the structural adjustment of the first groove in the deceleration unit, the overall structure of the SAW resonator can be flexibly diversified.

[0072] This application also provides a communication device, which includes the SAW resonator described above.

[0073] In some embodiments, the communication device includes at least one of a filter and a duplexer.

[0074] The communication device of this application embodiment, having the SAW resonator, can be miniaturized simultaneously based on the miniaturization of the SAW resonator, thus expanding its application in the field of miniaturization technology.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A surface acoustic wave resonator, characterized by, The surface acoustic wave resonator comprises: a piezoelectric thin film; an interdigital transducer located on the piezoelectric thin film, the interdigital transducer comprising a plurality of spaced-apart electrode fingers; a velocity reduction unit located in the piezoelectric thin film, the velocity reduction unit comprising at least one first groove for reducing the propagation velocity of the surface acoustic wave, and at least a portion of the first groove being located in a region between any two adjacent electrode fingers, so as to reduce the wavelength of the surface acoustic wave resonator while keeping the target resonant frequency of the surface acoustic wave unchanged.

2. The surface acoustic wave resonator according to claim 1, characterized by: The preset parameters of the first groove are configured to reduce the propagation velocity of the surface acoustic wave, and the preset parameters comprise at least one of the depth and the width.

3. The surface acoustic wave resonator according to claim 2, characterized by: The first groove is open from a side of the piezoelectric thin film close to the interdigital transducer, and the depth of the first groove is less than or equal to the thickness of the piezoelectric thin film in a direction from the piezoelectric thin film to the velocity reduction unit.

4. The SAW resonator of claim 3, wherein: The percentage value in the range of 10% to 50% between the depth of the first groove and the thickness of the piezoelectric thin film.

5. The SAW resonator of claim 2, wherein: The first groove is located in the region between the two adjacent electrode fingers, and the width of the first groove is less than or equal to the spacing between any two adjacent electrode fingers in the arrangement direction of the plurality of electrode fingers.

6. The surface acoustic wave resonator according to claim 5, characterized by: The percentage value in the range of 5% to 80% between the width of the first groove and the spacing between any two adjacent electrode fingers.

7. The SAW resonator of claim 2, wherein: The velocity reduction unit comprises a plurality of first grooves, and at least one first groove is located in the region between any two adjacent electrode fingers.

8. The surface acoustic wave resonator of claim 1, wherein: The surface acoustic wave resonator further comprises at least one reflector grating unit located on one side of the interdigital transducer in the arrangement direction of the plurality of electrode fingers, the reflector grating unit comprising a plurality of spaced-apart reflector grating bars.

9. The SAW resonator of claim 8, wherein: The velocity reduction unit further comprises at least one second groove, and the second groove is located between any two adjacent reflector grating bars.

10. The SAW resonator according to any one of claims 1 to 9, characterized in that: The extension direction of the first groove is parallel to the extension direction of the electrode fingers, and the cross-sectional shape of the first groove in the extension direction of the first groove is at least one of a rectangle, a trapezoid, and an arc.

11. The surface acoustic wave resonator of claim 1, wherein: The metallization rate of the surface acoustic wave resonator is in the range of 0.3 to 0.7, the aperture of the surface acoustic wave resonator is in the range of 10λ to 50λ, and the thickness of the electrode fingers is in the range of 0.025λ to 0.15λ, where λ is the wavelength of the surface acoustic wave resonator.

12. A communication device, characterized by: The communication device comprises the surface acoustic wave resonator according to any one of claims 1 to 11.

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