Bulk acoustic wave resonator and filter
By introducing continuous concave-convex contours and periodic structures into the bulk acoustic resonator frame design, the problem of transverse acoustic wave leakage was solved, resulting in higher parallel resonant impedance and Q value, and improving the energy utilization efficiency of the filter.
Patent Information
- Application Number
- CN202522473372.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2035-11-21
AI Technical Summary
In existing bulk acoustic resonators, transverse energy leakage leads to energy loss and a decrease in Q value. Traditional frames have limited reflection efficiency and are difficult to effectively suppress acoustic leakage at high frequencies.
The frame design features continuous concave-convex contours on at least one or both sides, forming multiple reflection interfaces to break up the lateral sound wave path. Combined with periodically changing sawtooth or wave-shaped contours, the reflection effect is enhanced.
It effectively suppresses transverse energy acoustic wave leakage, improves parallel resonant impedance and quality factor Q value, reduces energy loss, and enhances filter performance.
Smart Images
Figure CN224935645U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of filter technology, and in particular to a bulk acoustic resonator and filter. Background Technology
[0002] With the development of 5G and higher frequency communication technologies, related industries have increasingly stringent requirements for the performance and size of filters. Film Bulk Acoustic Resonators (FBARs) have become a key technology for high-frequency filters due to their high quality factor (Q value), low loss, and ease of integration.
[0003] Existing bulk acoustic resonators utilize the piezoelectric effect to convert electrical signals into acoustic signals at different vibration frequencies. Electrical energy is converted into bulk acoustic waves within a suspended membrane structure above the cavity, resonating at specific frequencies. These specific frequencies of acoustic signals are then directionally filtered to obtain and output a high-quality, stable electrical signal. However, an ideal resonant mode requires the acoustic energy to be completely confined within an effective region defined by electrodes. In practical devices, a portion of the acoustic energy propagates and leaks laterally as transverse energy waves, creating noise. This not only causes energy loss but also reduces the filter's quality factor (Q) and parallel resonant impedance (Rp), leading to deterioration in out-of-band rejection.
[0004] To suppress this transverse energy leakage, existing technologies typically incorporate a frame at the electrode edge of the bulk acoustic resonator. This frame forms an acoustic impedance mismatch boundary through mass loading, reflecting transversely propagating sound waves. However, traditional frames often employ simple geometries, such as rectangles or regular polygons, with straight edges. While this straight-edge boundary provides some reflection for transverse energy waves incident nearly perpendicularly, its reflection efficiency is limited for energy waves propagating at various complex angles, especially at high frequencies where wavelengths shorten and diffraction effects become more pronounced. A significant portion of the energy continues to propagate or leak along the frame boundary, thus limiting its effectiveness in improving the Q-value.
[0005] Therefore, a new bulk acoustic resonator structure is needed to solve the above-mentioned technical problems. Utility Model Content
[0006] The purpose of this invention is to provide a bulk acoustic resonator and filter that can more effectively suppress the leakage of transverse energy acoustic waves during the filtering process. To achieve this purpose, the present invention can adopt the following technical solution:
[0007] The first aspect of this utility model provides a bulk acoustic wave resonator, including a substrate on which a silicon dioxide layer and a resonant component are sequentially stacked. The resonant component includes a frame and a bottom electrode, a piezoelectric layer, and a top electrode stacked sequentially. The frame is disposed on the top electrode and / or the bottom electrode and surrounds and defines an effective resonant region. At least one side of the frame has a continuous concave-convex profile, and the at least one side includes: the inner wall of the frame facing the effective resonant region, and / or the outer wall of the frame facing away from the effective resonant region.
[0008] Optionally, both the inner wall of the frame and the outer wall facing away from the effective resonant region have continuous concave-convex contours, and the concave-convex contours of the inner wall and the outer wall are symmetrically arranged.
[0009] Optionally, the continuous concave-convex profile is a structure that changes periodically.
[0010] Optionally, the periodically changing structure is a sawtooth-shaped profile, and the tips of the sawtooth-shaped profile are rounded.
[0011] Optionally, the length of the bottom edge of the sawtooth in a single cycle of the sawtooth shape profile is A, where A is 1 / 15 to 1 / 10 of the side length of the side where the sawtooth is located in the frame; the amplitude of the sawtooth in a single cycle is B, where B is 1 / 5 to 1 / 3 of the length of the bottom edge A of the sawtooth corresponding to the sawtooth.
[0012] Optionally, the periodically changing structure is a wave-shaped profile.
[0013] Optionally, the wave shape profile is a periodic curve based on trigonometric functions.
[0014] Optionally, the silicon dioxide layer has an annular perforated structure, and the substrate, the annular perforated silicon dioxide layer, and the bottom electrode in the resonant component together form a cavity.
[0015] Optionally, the frame and the top electrode or the bottom electrode are integrally formed.
[0016] A second aspect of this utility model provides a filter, including a filter body, the filter further including at least one of the bulk acoustic wave resonators, the bulk acoustic wave resonators being disposed on the filter body.
[0017] The beneficial effects of this utility model are:
[0018] The resonant component of the bulk acoustic wave resonator provided by this invention employs a frame with a continuous concave-convex profile, which, together with the bottom electrode and / or top electrode supporting it, defines an effective resonant region. Within the effective resonant region, the continuous concave-convex profile of the frame provides a large number of microscopic reflection interfaces at different angles. Thus, during the operation of the bulk acoustic wave resonator, compared to a frame with a straight edge profile, these microscopic reflection interfaces can create more reflections of the sound waves within the frame, thereby more effectively confining the transverse energy sound waves propagating along the plane within the effective resonant region. Simultaneously, through the multiple reflections of sound waves by the microscopic reflection interfaces, an irregular acoustic impedance mismatch interface based on the transverse energy sound waves can be artificially created. Under this irregular acoustic impedance interface, because the propagation path of the transverse energy sound waves is broken and reflected, the leakage of transverse energy sound waves propagating along the frame boundary is correspondingly reduced, thereby reducing energy loss in the bulk acoustic wave resonator and improving the device performance of the filter. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the structure of the bulk acoustic resonator of this utility model;
[0020] Figure 2 This is a schematic diagram of the frame with a sawtooth-shaped outline in this utility model;
[0021] Figure 3 This is a partial enlarged view of the frame C, which has a sawtooth-shaped outline, in this utility model;
[0022] Figure 4 This is a schematic diagram of a frame with straight edges in the prior art;
[0023] Figure 5 This is a magnified view of a portion of the frame D, which is straight-edged in the prior art.
[0024] Figure 6 This is a front view of the bulk acoustic resonator of this utility model;
[0025] Figure 7 This is a simulation result diagram of a straight-edged frame in the prior art under finite element experiment;
[0026] Figure 8 This is a simulation result diagram of the serrated outline of the frame in this utility model under finite element experiment.
[0027] In the picture:
[0028] 110, Substrate; 120, Silicon dioxide layer; 130, Bottom electrode; 140, Piezoelectric layer; 150, Top electrode; 160, Frame; 160', Straight-edge frame; 170, Cavity; 180, Effective resonant region; 210, Resonant component. Detailed Implementation
[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.
[0030] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" 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. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0032] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.
[0033] This embodiment provides a filter. This filter can be applied to RF front-end modules such as 5G communication. The filter incorporates a bulk acoustic wave resonator. This embodiment aims to optimize the structure of the bulk acoustic wave resonator in the prior art, so that during the filtering process, the leakage of transverse energy acoustic waves can be more effectively suppressed through this resonator.
[0034] Please see Figure 1The bulk acoustic wave resonator includes a substrate 110, on which a silicon dioxide layer 120 and a resonant component 210 can be sequentially stacked. In this embodiment, the substrate 110 can be made of silicon wafer material. The substrate 110 serves as the basic packaging framework of the bulk acoustic wave resonator, providing a physical substrate for the bulk acoustic wave resonator to be used for electrical actuation. The silicon dioxide layer 120 has a ring-shaped hollow structure. Silicon dioxide, as a stable dielectric material, helps to regulate the dielectric properties of the bulk acoustic wave resonator structure and improve the overall operating performance of the bulk acoustic wave resonator. The resonant component 210 includes a bottom electrode 130, a piezoelectric layer 140, and a top electrode 150 stacked sequentially, wherein the bottom electrode 130 is disposed adjacent to the silicon dioxide layer 120. The bottom electrode 130 and the top electrode 150 are metal layers.
[0035] like Figure 1 As shown, the substrate 110, the annular hollow silicon dioxide layer 120, and the bottom electrode 130 in the resonant component 210 together form a cavity 170. The main function of the cavity 170 is to reflect the sound wave energy by utilizing the high acoustic impedance mismatch between the air gap and the device interface, and to suppress energy leakage at the upper and lower interfaces.
[0036] like Figure 2 and Figure 3 As shown, the resonant component 210 also includes a frame 160, which is preferably configured as a mass-loaded frame or an acoustic reflection structure. In this embodiment, the frame 160 is disposed on the bottom electrode 130 of the resonant component 210 and (together with the resonant component 210) located above the cavity 170. In other embodiments without departing from the spirit of the present invention, the frame 160 may also be disposed on the top electrode 150, or simultaneously disposed on the bottom electrode 130 and the top electrode 150 (e.g., Figure 6 (As shown). The frame 160 surrounds and defines an effective resonant region 180, as... Figure 1 As shown in the dashed box, the effective resonant region 180 is the core working region for generating the main resonance, which is enclosed by the inner wall of the frame 160.
[0037] The core function of frame 160 is to reduce acoustic energy leakage. Specifically, the inner wall of frame 160 serves as an acoustic interface to regulate the propagation path of transverse sound waves, reflecting transversely leaked sound wave energy back into the effective resonant region 180. This helps to reduce the leakage of sound wave energy to the external region of frame 160.
[0038] However, existing framework designs still have shortcomings in implementing this functionality. For example... Figure 4 and Figure 5As shown, the inner walls of frames in existing technologies are typically straight-edged. While this straight-edged edge profile does reflect laterally propagating sound waves to some extent, the direction of sound wave reflection is singular. Therefore, the confinement effect of this straight-edged edge profile on laterally propagating sound waves is limited, and significant energy leakage still occurs.
[0039] In response to this issue, such as Figure 2 and Figure 3 As shown, this utility model provides an improved frame 160, the core of which is that at least one side of the frame 160 has a continuous concave-convex profile. For example, the inner wall of the frame 160 facing the effective resonant region 180 has a continuous concave-convex profile. The key function of this continuous concave-convex profile is to simultaneously form an impedance mismatch interface and disperse the reflection path of transverse acoustic waves, thereby more effectively suppressing energy leakage.
[0040] Specifically, the continuous concave-convex profile provides a large number of microscopic reflective interfaces at different angles. When transverse energy sound waves strike these microscopic reflective interfaces, they are scattered in multiple different directions, rather than producing regular, unidirectional reflections as with straight-edged profiles.
[0041] Through the above-mentioned effects, the propagation path of transverse energy sound waves can be effectively changed and interrupted, preventing them from easily leaking outside the effective resonant region 180. In other words, they are more effectively confined within the effective resonant region 180, achieving the beneficial effect of suppressing energy sound waves and improving the quality factor Q of the device.
[0042] It should be noted that in some specific device designs, a continuous concave-convex profile can also be provided only on the outer wall of the frame 160 facing away from the effective resonant region 180. The consideration for this design is that when residual acoustic energy enters the wall of the frame 160, the concave-convex profile on the outer wall of the frame 160 can be used to prevent this residual acoustic energy that has already entered the frame 160 from radiating further to the outside of the device, and scatter it back into the interior of the frame 160 wall, which can also reduce energy loss.
[0043] Furthermore, this utility model also provides a further preferred embodiment. For example... Figure 2 , Figure 3 and Figure 6 As shown, the inner wall of frame 160 has a continuous concave-convex profile, and its outer wall facing away from the effective resonant region 180 also has a continuous concave-convex profile. This design combines the advantages of the two aforementioned schemes, providing a dual acoustic confinement mechanism: the profile of the inner wall acts as the first line of defense to suppress leakage at the source; the profile of the outer wall acts as the second line of defense to prevent the leakage of residual energy.
[0044] Preferably, the continuous concave-convex contour of the inner wall can be symmetrically arranged with the continuous concave-convex contour of the outer wall. This symmetrical design allows the frame 160 to form acoustic wave scattering interfaces on both its inner and outer sides. This not only prevents transverse energy acoustic waves from leaking inwards but also prevents them from radiating outwards through the frame, thereby forming a more regular and effective acoustic wave interference or attenuation mode within the frame 160 wall, further enhancing the overall transverse energy acoustic wave confinement capability.
[0045] To further enhance the above-mentioned technical effects, in this embodiment, the continuous concave-convex contour can preferably be a periodically varying structure. Compared with random edge contours, the advantage of using a periodically varying structure is that its reflection characteristics are uniform and predictable, making it easy to optimize the suppression effect of specific frequency bands through design (e.g., adjusting the period parameter), while also ensuring the consistency and repeatability of the manufacturing process.
[0046] Please see Figure 2 and Figure 3 In a preferred embodiment, the periodically changing structure is a sawtooth-shaped profile, with rounded tips for the sawtooth edges. Furthermore, to ensure optimal technical performance, the parameters of this sawtooth-shaped profile can be set as follows:
[0047] Preferably, the length of the bottom edge of the sawtooth in a single cycle is set to A, where A is 1 / 15 to 1 / 10 of the side length of the side containing the sawtooth in frame 160. Simultaneously, the amplitude of the sawtooth in a single cycle is set to B, where B is 1 / 5 to 1 / 3 of the length of the bottom edge A corresponding to the sawtooth. It should be noted that "the side length of the side containing the sawtooth in frame 160" here refers to the overall straight-line length of the inner wall of the frame to which the sawtooth profile is attached.
[0048] The selection of the above parameter range (i.e., the range of A and the range of B relative to A) aims to balance the acoustic reflection effect and the manufacturing process yield: on the one hand, it ensures that the sawtooth profile is fine enough to effectively disperse and reflect transverse energy sound waves; on the other hand, it avoids the decline in the yield of manufacturing processes such as photolithography and etching due to the sawtooth profile being too dense.
[0049] As a further preferred example, the bottom edge length A of the serration can be specifically 1 / 15, 1 / 12, or 1 / 10 of the side length of the side containing the serration in the frame 160; and the serration amplitude B can be specifically 1 / 5, 4 / 15, or 1 / 3 of its corresponding bottom edge length A. Without departing from the spirit of this utility model, the above parameters A and B can be adjusted according to actual process requirements, and are not specifically limited here.
[0050] To further verify the technical effect of the sawtooth-shaped frame of this utility model, a finite element simulation experiment was conducted and compared with a comparative example using a traditional straight-edge frame 160'. Figure 7 The finite element simulation results using the straight-edge frame 160' (i.e., the comparative example) are shown. Figure 8 The figure shows the finite element simulation results of the frame with the sawtooth-shaped profile adopted in the embodiment of this utility model.
[0051] In the simulation experiment, to ensure that the variable is singular, the comparative scale (using a straight-edged frame 160') is set to have the same height and width as the embodiment of this utility model (using a frame 160 with a serrated outline).
[0052] like Figure 7 and Figure 8 As shown, the finite element simulation results obtained are as follows: Comparative Example ( Figure 7 The parallel resonant impedance Rp of the present invention is 2576, while the embodiment of the present invention ( Figure 8 The parallel resonant impedance Rp of the device is significantly increased to 3021, an increase of approximately 17%.
[0053] The experimental results show that when using a frame 160 with a sawtooth profile, the transverse energy acoustic waves are more effectively confined within the effective resonant region 180. This directly proves that the leakage of transverse energy acoustic waves is effectively suppressed, thereby significantly improving the quality factor Q of the resonator and reducing its energy loss.
[0054] In another embodiment, the periodically changing structure can also be a wave-shaped profile. For example, the wave-shaped profile can be a periodic curve based on trigonometric functions. Compared with the aforementioned sawtooth profile, the contour boundary curve of the wave-shaped profile is smoother, which makes it more advantageous in controlling the propagation path of transverse energy sound waves, while also achieving effective transverse energy sound wave scattering.
[0055] In specific implementations, the dimensions of the frame 160 are also preferred parameters. Preferably, the height of the frame 160 can be 0.5 to 1.5 micrometers, and the width can be 0.5 to 5 micrometers. This size range provides sufficient mass loading effect to form an effective acoustic impedance mismatch boundary to reflect sound waves, while avoiding a significant increase in energy capacitance or an excessive burden on the manufacturing process due to excessive height or width. By optimizing the height-to-width ratio of the frame 160, the amount of acoustic signal transmitted within the effective resonant region 180 can be avoided due to a mismatch in the height-to-width ratio of the frame 160, thereby ensuring the transmission efficiency of the filter.
[0056] Further preferred examples include that the height of the frame 160 can be 0.5 micrometers, 1 micrometer, or 1.5 micrometers, and the width can be 0.5 micrometers, 2.75 micrometers, or 5 micrometers.
[0057] The material of the piezoelectric layer 140 can be selected from conventional piezoelectric materials in the art, such as aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), lithium tantalate (LiTaO3) single crystal, or lithium niobate (LiNbO3) single crystal. Specifically, using aluminum nitride helps to aid heat dissipation when the resonator operates at excessive power. Doping with scandium-doped aluminum nitride helps to enhance the piezoelectric performance of the resonator. Adding lithium tantalate or lithium niobate single crystals helps to improve the filtering capability of the bulk acoustic wave filter.
[0058] Preferably, the frame 160 can be integrally formed with its electrodes (e.g., top electrode 150 or bottom electrode 130). For example, the frame 160, top electrode 150, and bottom electrode 130 are made of the same metal material and are integrally formed through the same photolithography and etching process. This integral forming method simplifies the device manufacturing process and improves production efficiency. Furthermore, it avoids device failure caused by structural changes due to stress or high temperature at the connection points or surfaces of different components. This method ensures the stability and accuracy of the bulk acoustic wave resonator under specific operating conditions.
[0059] Furthermore, this invention also provides a filter (not shown) with at least one bulk acoustic resonator as described above. Because the bulk acoustic resonator provided by this invention effectively suppresses lateral energy leakage through its continuous concave-convex profile, it (as shown in simulation experiments) has a higher parallel resonant impedance Rp value and a higher quality factor Q value, and the energy acoustic waves are effectively suppressed.
[0060] When this high-performance resonator is applied to a filter, its high Q-value helps to significantly reduce the filter's insertion loss. Simultaneously, its effective suppression of energetic acoustic waves contributes to superior out-of-band rejection performance and a clearer passband edge. Therefore, the filter provided by this invention has lower energy loss and better frequency selectivity compared to existing technologies.
[0061] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make various obvious changes, readjustments, and substitutions without departing from the protection scope of this utility model. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.
Claims
1. A bulk acoustic wave resonator, comprising a substrate (110), wherein a silicon dioxide layer (120) and a resonant component (210) are sequentially stacked on the substrate (110); the resonant component (210) comprises a frame (160) and a bottom electrode (130), a piezoelectric layer (140), and a top electrode (150) stacked sequentially; the frame (160) is disposed on the top electrode (150) and / or the bottom electrode (130) and surrounds and defines an effective resonant region (180), characterized in that, The frame (160) has at least one side with a continuous concave-convex profile, the at least one side including: the inner wall of the frame (160) facing the effective resonant region (180), and / or, the outer wall of the frame (160) facing away from the effective resonant region (180).
2. The bulk acoustic resonator according to claim 1, characterized in that, The inner wall and the outer wall of the frame (160) both have the continuous concave-convex profile, and the concave-convex profile of the inner wall is symmetrically arranged with respect to the concave-convex profile of the outer wall.
3. The bulk acoustic resonator according to claim 1 or 2, characterized in that, The continuous concave-convex contour is a structure that changes periodically.
4. The bulk acoustic resonator according to claim 3, characterized in that, The periodically changing structure is a sawtooth-shaped profile, and the tips of the sawtooth-shaped profile are rounded.
5. The bulk acoustic resonator according to claim 4, characterized in that, The length of the bottom edge of the sawtooth in a single cycle of the sawtooth shape profile is A, where A is 1 / 15 to 1 / 10 of the side length of the side containing the sawtooth in the frame (160); and / or, The sawtooth amplitude of a single cycle is B, where B is 1 / 5 to 1 / 3 of the length A of the bottom edge of the sawtooth corresponding to that sawtooth.
6. The bulk acoustic resonator according to claim 3, characterized in that, The periodically changing structure has a wave-shaped profile.
7. The bulk acoustic resonator according to claim 6, characterized in that, The wave-shaped profile is a periodic curve based on trigonometric functions.
8. The bulk acoustic resonator according to claim 1, characterized in that, The silicon dioxide layer (120) has an annular hollow structure. The substrate (110), the annular hollow silicon dioxide layer (120), and the bottom electrode (130) in the resonant component (210) together form a cavity (170).
9. The bulk acoustic resonator according to claim 1, characterized in that, The frame (160) and the top electrode (150) or the bottom electrode (130) are integrally formed.
10. A filter, comprising a filter body, characterized in that, The filter further includes at least one bulk acoustic resonator as described in any one of claims 1 to 9, the bulk acoustic resonator being disposed on the filter body.