Acoustic filtering device
By setting up overlapping areas of the Lelo-like polygon-shaped shape in the bulk acoustic wave element of the acoustic filter device, the problems of reduced quality factors and lateral clutter mode caused by lateral vibration in the acoustic wave device are solved, and a higher quality factor and more stable filtering performance are achieved.
Patent Information
- Application Number
- CN202311616281.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-28
- Publication Date
- 2025-05-30
AI Technical Summary
In acoustic wave devices, due to poor boundary conditions and poor film flatness caused by process, the sound waves produce lateral vibrations during longitudinal propagation, reducing the device quality factors and introducing lateral clutter modes.
By setting the shape of the overlapping region to a lelopolygon in the bulk acoustic wave element of the acoustic filter device, the lateral mode is effectively reduced and the quality factor of the acoustic wave device is improved.
The design of the Lelo polygon effectively weakens the lateral mode, improves the quality factor of the acoustic devices, improves the filter's insertion loss performance and passband stability.
Smart Images
Figure CN120074438A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the fields of semiconductor technology and communication device technology, and relates to an acoustic filtering device. Background Art
[0002] In recent years, filters and duplexers based on acoustic wave resonators have been increasingly miniaturized, high-frequency, and broadband. High-performance devices have increasingly higher requirements for device insertion loss, which requires the resonator itself to have a high quality factor. For example, in bulk acoustic wave devices, sound waves mainly propagate longitudinally along the stacking direction. However, in practical applications, due to factors such as unsatisfactory boundary conditions and poor film flatness caused by the process, sound waves will produce lateral vibrations when propagating longitudinally, causing energy to leak in the lateral direction, thereby reducing the quality factor of the device and introducing lateral noise modes. In the corresponding filter, the insertion loss decreases and large ripples appear in the passband. Summary of the invention
[0003] In view of this, the present disclosure provides an acoustic filter device. The object of the present invention is to provide an acoustic filter device that can suppress the lateral vibration of body sound waves.
[0004] One aspect of the present disclosure provides an acoustic filtering device, comprising:
[0005] A substrate, and a plurality of bulk acoustic wave elements disposed on the substrate;
[0006] The bulk acoustic wave element is configured to include an acoustic reflector, a bottom electrode, a piezoelectric layer and a top electrode in order from the substrate upward, and the acoustic reflector, the bottom electrode, the piezoelectric layer and the top electrode have an overlapping area;
[0007] Among them, the above-mentioned multiple bulk acoustic wave elements include at least one first target bulk acoustic wave element, and at least one layer of the above-mentioned acoustic reflector, the above-mentioned bottom electrode, the above-mentioned piezoelectric layer and the above-mentioned top electrode included in the above-mentioned first target bulk acoustic wave element is configured to have a shape of a Reuleaux polygon in the above-mentioned overlapping area.
[0008] According to an embodiment of the present disclosure, the plurality of BAW elements constitute the series arm and the parallel arm of the acoustic filter device, and the at least one first target BAW element constitutes at least a portion of the parallel arm or at least a portion of the series arm.
[0009] According to an embodiment of the present disclosure, the multiple endpoints included in the above-mentioned Reuleaux-like polygon are all configured as arcs.
[0010] According to an embodiment of the present disclosure, the edge of the overlapping area is configured to be provided with an inwardly concave annular structure or an outwardly convex annular structure.
[0011] According to an embodiment of the present disclosure, the above-mentioned acoustic reflector is configured to be embedded in the above-mentioned substrate, and the above-mentioned acoustic emitter is configured to be a cavity structure.
[0012] According to an embodiment of the present disclosure, the above-mentioned acoustic reflector is configured to be embedded in the above-mentioned substrate, and the above-mentioned acoustic emitter is configured to be a Bragg reflection structure composed of alternating multi-layer materials.
[0013] According to an embodiment of the present disclosure, the above-mentioned multiple bulk acoustic wave elements include a second target bulk acoustic wave element, and at least one layer of the above-mentioned acoustic reflector, the above-mentioned bottom electrode, the above-mentioned piezoelectric layer, and the above-mentioned top electrode included in the above-mentioned second target bulk acoustic wave element is configured to have a shape of a quasi-regular polygon in the above-mentioned overlapping region.
[0014] According to an embodiment of the present disclosure, each side of the above-mentioned quasi-regular polygon is an arc, and the radius of curvature of the arc is configured to be less than the distance from the end point of the above-mentioned quasi-regular polygon to the center of the above-mentioned quasi-regular polygon.
[0015] According to an embodiment of the present disclosure, each side of the above-mentioned quasi-regular polygon is an arc, and the radius of curvature of the arc is configured to be greater than the distance from the end point of the above-mentioned quasi-regular polygon to the center of the above-mentioned quasi-regular polygon.
[0016] According to an embodiment of the present disclosure, each side of the above-mentioned quasi-regular polygon is composed of at least two arcs, and the arcs are at least partial curves of an elliptical curve with the end points of the above-mentioned quasi-regular polygon as the long axis end points.
[0017] According to an embodiment of the present disclosure, for the multiple bulk acoustic wave elements included in the acoustic filtering device, by setting the shape of the overlapping region of each thin film layer in at least one first target bulk acoustic wave element among the multiple bulk acoustic wave elements, that is, the shape of the effective resonance region, to a Reuleaux polygon shape, since any two sides of the Reuleaux polygon are not parallel, the transverse mode can be effectively weakened. At the same time, since the Reuleaux polygon has a larger area-to-perimeter ratio compared to various regular polygons, the quality factor of the acoustic wave device can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:
[0019] Figure 1 A cross-sectional view of the acoustic filtering device according to an embodiment of the present disclosure is schematically shown;
[0020] Figure 2A A top view of the first target bulk acoustic wave element according to an embodiment of the present disclosure is schematically shown;
[0021] Figure 2BA top view of a first target bulk acoustic wave device according to another embodiment of the present disclosure is schematically shown;
[0022] Figure 3 A schematic diagram showing the relationship between the quality factor of a bulk acoustic wave device according to an embodiment of the present disclosure and the area-to-perimeter ratio of the overlapping region is schematically shown;
[0023] Figure 4 A schematic diagram showing the relationship between the quality factor of a bulk acoustic wave device according to an embodiment of the present disclosure and the lateral clutter frequency is schematically shown;
[0024] Figure 5 A circuit diagram of an acoustic filtering device according to an embodiment of the present disclosure is schematically shown;
[0025] Figure 6A A top view of a second target bulk acoustic wave device according to an embodiment of the present disclosure is schematically shown;
[0026] Figure 6B A top view of a second target bulk acoustic wave device according to another embodiment of the present disclosure is schematically shown;
[0027] Figure 7 A top view of the overlapping region of a bulk acoustic wave device according to an embodiment of the present disclosure is schematically shown;
[0028] Figure 8 A top view of an acoustic filtering device according to an embodiment of the present disclosure is schematically shown. Detailed Description of the Embodiments
[0029] To make the objectives, technical solutions, and advantages of the present disclosure clearer and more understandable, the present disclosure will be further described in detail below with reference to specific embodiments and the accompanying drawings.
[0030] An acoustic wave filter is composed of a combination of several acoustic wave resonators. Among them, acoustic wave resonators are generally classified into surface acoustic wave (SAW) devices, bulk acoustic wave (BAW) devices, and contour mode resonators (CMR) according to the vibration mode.
[0031] SAW devices use interdigital electrodes to convert electrical energy into acoustic energy, or conversely convert acoustic energy into electrical energy. The interdigital electrodes use a piezoelectric substrate and two opposite bus bars at two different potentials and two sets of electrodes connected to the two bus bars. Due to the inverse piezoelectric effect, the electric field between two consecutive electrodes at different potentials provides a sound wave source. Conversely, if the transducer receives an incident wave, charges are generated in the electrodes due to the piezoelectric effect, and a resonator is obtained by placing the transducer between two reflection gratings.
[0032] BAW devices are similar to SAW devices, relying on the piezoelectric effect of piezoelectric materials to form resonance. In general, BAW devices have higher quality factors, where the quality factor is the ratio of the total energy stored in the resonator to the energy lost by the resonator through various pathways. And better power handling capacity, but the equivalent coupling coefficient is slightly smaller than SAW. BAW resonators generally consist of a sandwich structure consisting of a top electrode, a piezoelectric layer, and a bottom electrode to produce resonance. Above the top electrode and below the bottom electrode is an air cavity or an acoustic reflection layer, and the resonance area is the overlapping area of the above layers.
[0033] In addition, CMR devices use the Lamb wave mode of the piezoelectric layer to make resonators. Due to the small equivalent coupling coefficient of the device, poor reliability, and low quality factor, it is rarely used in acoustic filters.
[0034] In recent years, filters and duplexers based on acoustic wave resonators have been increasingly miniaturized, high-frequency, and broadband. High-performance devices have increasingly higher requirements for device insertion loss, which requires the resonator itself to have a high quality factor. For example, in bulk acoustic wave devices, sound waves mainly propagate longitudinally along the stacking direction. However, in practical applications, due to factors such as unsatisfactory boundary conditions and poor film flatness caused by the process, sound waves will produce lateral vibrations when propagating longitudinally, causing energy to leak in the lateral direction, thereby reducing the quality factor of the device and introducing lateral noise modes. In the corresponding filter, the insertion loss decreases and large ripples appear in the passband.
[0035] Therefore, there is a need to improve the quality factor and spurious mode of bulk acoustic wave devices such as film bulk acoustic resonators (FBARs) and solid mounted resonators (SMRs).
[0036] In view of this, the present disclosure proposes an acoustic filtering device for improving the quality factor of an acoustic wave device and reducing the lateral clutter mode.
[0037] Specifically, an embodiment of the present disclosure provides an acoustic filtering device, which includes: a substrate, and a plurality of bulk acoustic wave elements arranged on the substrate; wherein the bulk acoustic wave elements are configured to include, in order from the substrate upward, an acoustic reflector, a bottom electrode, a piezoelectric layer and a top electrode, and the acoustic reflector, the bottom electrode, the piezoelectric layer and the top electrode have an overlapping area; wherein the plurality of bulk acoustic wave elements include at least one first target bulk acoustic wave element, and at least one layer of the acoustic reflector, the bottom electrode, the piezoelectric layer and the top electrode included in the first target bulk acoustic wave element is configured to have a shape of a Reuleaux polygon in the overlapping area.
[0038] Figure 1 A cross-sectional view schematically shows an acoustic filter device according to an embodiment of the present disclosure.
[0039] As Figure 1 shown, the acoustic filtering device may include a substrate 10 and a plurality of bulk acoustic wave elements 20 disposed on the substrate 10. Among them, the bulk acoustic wave element 20 is configured to sequentially include an acoustic reflector 21, a bottom electrode 22, a piezoelectric layer 23, and a top electrode 24 from the substrate 10 upward. The acoustic reflector, the bottom electrode, the piezoelectric layer, and the top electrode have an overlapping region, that is, the acoustic reflector 21, the bottom electrode 22, the piezoelectric layer 23, and the top electrode 24 overlap above the substrate 10, and this overlapping region may be the effective resonance region of the bulk acoustic wave element 20.
[0040] According to an embodiment of the present disclosure, the substrate 10 may be made of materials such as silicon, quartz, or alumina. The acoustic reflector 21 may be disposed in the substrate 10, and the structure of the acoustic reflector 21 is to confine the energy of the acoustic wave in the filter body, and SMR technology or FBAR technology is often used. The acoustic impedance of the piezoelectric layer 23 is not much different from that of the substrate 10. The piezoelectric layer 23 may be composed of any one or a combination of materials such as aluminum nitride, zinc oxide, lithium niobate, and lithium tantalate, or may be composed of a combination of one or more of the above materials doped with other elements. The bottom electrode 22 and the top electrode 24 included in the bulk acoustic wave element 20 may be metals with good electrical conductivity, specifically, any one of the following metals or a metal alloy composed of multiple metals: aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, titanium, tin, etc.
[0041] According to an embodiment of the present disclosure, there are overlapping regions in the bulk acoustic wave element, and the overlapping regions in the bulk acoustic wave element are also called effective resonance regions. The bulk acoustic wave element whose cross-sectional shape of the overlapping region is a Reuleaux polygon is called the first target bulk acoustic wave element. At least one of the acoustic reflector 21, the bottom electrode 22, the piezoelectric layer 23, and the top electrode 24 has a shape of a Reuleaux polygon in the overlapping region, which can be understood as that any two sides of the polygon formed by the overlapping region are not parallel.
[0042] According to an embodiment of the present disclosure, for the plurality of bulk acoustic wave elements included in the acoustic filtering device, by setting the shape of the overlapping region of each thin film layer in at least one first target bulk acoustic wave element among the plurality of bulk acoustic wave elements, that is, the shape of the effective resonance region, to a Reuleaux polygon shape, since any two sides of the Reuleaux polygon are not parallel, the transverse mode can be effectively weakened. At the same time, since the Reuleaux polygon has a larger area-to-perimeter ratio compared to various regular polygons, the quality factor of the acoustic wave device can be effectively improved.
[0043] According to an embodiment of the present disclosure, the acoustic reflector is configured to be embedded in a substrate, and the acoustic emitter is configured as a cavity structure. The cavity structure can be formed by etching the structure of a part of the substrate, then filling a sacrificial layer on the etched structure, and finally releasing the sacrificial layer, thereby fabricating the acoustic reflector. Among them, the material of the sacrificial layer can be silicon dioxide or phosphosilicate glass. Of course, other materials can also be used as the sacrificial layer, which is not limited here. For example, porous silicon, photoresist, etc. A thin film bulk acoustic resonator is generally an acoustic filtering device formed by fabricating the acoustic reflector in this way.
[0044] According to an embodiment of the present disclosure, the acoustic reflector is configured to be embedded in a substrate, and the acoustic emitter can also be configured as a Bragg reflection structure composed of alternating layers of materials. A solid-state assembled resonator is generally an acoustic filtering device formed by fabricating the acoustic reflector in this way.
[0045] According to an embodiment of the present disclosure, multiple end points included in the Reuleaux polygon-like shape are all configured to be arc-shaped. When fabricating the first target bulk acoustic wave element, the end points of the overlapping region with a Reuleaux polygon-like shape in the first target bulk acoustic wave element can be processed into an arc shape to configure multiple end points as arc-shaped.
[0046] According to an embodiment of the present disclosure, the edge of the overlapping region is configured to be provided with an inwardly concave annular structure or an outwardly convex annular structure. The edge of the overlapping region is an annular structure composed of arcs, but the concave and convex directions of the arcs are not limited here. The outwardly convex annular structure can be understood as the tangent of the arc on the annular structure intersecting the annular structure, and the inwardly concave annular structure can be understood as the tangent of the arc on the annular structure being outside the annular structure and not intersecting the annular structure.
[0047] Figure 2A A top view of the first target bulk acoustic wave element according to an embodiment of the present disclosure is schematically shown.
[0048] As Figure 2A shown, the overlapping region of the first target bulk acoustic wave element is an inwardly concave or outwardly convex annular structure. The bulk acoustic wave element includes an acoustic reflector 21, a bottom electrode 22, a piezoelectric layer 23, and a top electrode 24. The shapes of multiple bulk acoustic wave elements are Reuleaux pentagon-like shapes, where the edge of the Reuleaux pentagon-like shape is an inwardly concave or outwardly convex annular structure, and the end points of the pentagon are processed into an arc shape because a sharp overlapping region pattern or the outer shape of the bulk acoustic wave element will reduce the filtering effect.
[0049] Figure 2B A top view of the first target bulk acoustic wave element according to another embodiment of the present disclosure is schematically shown.
[0050] As Figure 2B shown, different from Figure 2A that, here the Reuleaux polygon-like shape is set as a triangle. Figure 2BThe overlapping region of the bulk acoustic wave element in the [device] is also a concave annular structure. The bulk acoustic wave element includes an acoustic reflector 21, a bottom electrode 22, a piezoelectric layer 23, and a top electrode 24. The shapes of multiple bulk acoustic wave elements are similar to Reuleaux triangles, where the edges of the Reuleaux triangles are concave annular structures, and the endpoints of the triangles are also processed into arcs.
[0051] According to an embodiment of the present disclosure, according to Figure 2A Figure 2B By comparing two types of Reuleaux polygons in [the text], it is obtained that the acoustic filtering device with a Reuleaux pentagon has a higher quality factor than the acoustic filtering device with a Reuleaux triangle. However, under the same area of the Reuleaux triangle and the Reuleaux pentagon, the present disclosure selects the FBAR device formed by the Reuleaux triangle because the shortest distance from the shape center to the edge is shorter than that of the Reuleaux pentagon, making the heat dissipation effect of the device better. This phenomenon is because both above the top electrode and below the bottom electrode of the FBAR device are cavities, and the poor heat dissipation of air causes the central region of the FBAR device to be the hottest, with a gradient temperature change from the center to the edge. Therefore, the number of sides of the Reuleaux polygon can be set according to specific application scenarios.
[0052] Figure 3 Schematically shows a schematic diagram of the relationship between the quality factor of the bulk acoustic wave element and the area perimeter ratio of the overlapping region in an embodiment of the present disclosure.
[0053] As Figure 3 shown, the quality factor of the bulk acoustic wave element increases as the area perimeter ratio of the overlapping region increases. Figure 3 In [the text] include four geometric figures: small triangles, squares, rhombuses, and circles. These four geometric figures have the same area but different area perimeter ratios. Figure 3 Shows the magnitude relationship of the area perimeter ratios of geometric figures with different shapes, and the differences in quality factors caused by different area perimeter ratios of geometric figures.
[0054] According to an embodiment of the present disclosure, the area of the Reuleaux polygon can be obtained by the following formula:
[0055] A = R 2 / 2 * π - n * sin(π / n) + n * sin(2π / n) / 4 / sin(2π / n * (n - 1) / 4)
[0056] where A is the area of the Reuleaux polygon, R is the radius of the circle, i.e., the side length of the polygon, and n is the number of sides.
[0057] Figure 4 Schematically shows a schematic diagram of the relationship between the quality factor of the bulk acoustic wave element and the frequency in an embodiment of the present disclosure.
[0058] As Figure 4As shown, the vertical axis represents the quality factor, and the horizontal axis represents the frequency of the sound wave received by the acoustic filtering device. Figure 4 Using finite element simulation of 3D FBAR devices, the quality factors of Reuleaux pentagon-like, regular pentagon, and rectangular devices were compared. The left dashed line on the curve graph corresponds to the resonance frequency, and the right dashed line corresponds to the anti-resonance frequency. As can be seen from the figure, both the Reuleaux polygon and the regular pentagon effectively suppress the lateral clutter near the resonance frequency and the anti-resonance frequency. At the same time, the Reuleaux polygon has a certain improvement in the quality factor compared to the regular pentagon.
[0059] According to an embodiment of the present disclosure, because the area-to-perimeter ratio of the Reuleaux polygon is greater than that of the corresponding regular polygon, the Reuleaux polygon shape will have an improvement in the quality factor performance compared to the regular polygon. The area-to-perimeter ratio of a circle is greater than that of the Reuleaux polygon, but due to the parallelism of the opposite sides of the circular device, the lateral parasitic mode is more serious, which will introduce strong ripples in the passband of the filter. Therefore, the improvement in the quality factor performance of the circle is lower than that of the Reuleaux polygon.
[0060] According to an embodiment of the present disclosure, multiple bulk acoustic wave elements form the series arms and parallel arms of the acoustic filtering device, and at least one first target bulk acoustic wave element forms at least a part of the parallel arm or at least a part of the series arm. The architecture of the acoustic filtering device formed by the series arms and parallel arms can be a trapezoidal architecture, and at least one first target bulk acoustic wave element forms the series arm or the parallel arm of the acoustic filtering device.
[0061] Figure 5 Schematically shows the circuit diagram of the acoustic filtering device according to an embodiment of the present disclosure.
[0062] As Figure 5 shown, an acoustic filtering device with a specific passband can be constructed in the following way: arranging multiple bulk acoustic wave elements in the series arms and parallel arms of a trapezoidal architecture, where the multiple bulk acoustic wave elements include series bulk acoustic wave elements S1 to S5 and parallel bulk acoustic wave elements P1 to P5, and connecting these bulk acoustic wave elements to each other. At least one of these acoustic wave elements is a first target acoustic wave element, and the overlapping area of the first target acoustic wave element is a Reuleaux polygon. It should be clear here that the number of the series arms and parallel arms of the acoustic filtering device in this embodiment and the connection relationship between them are not limited herein.
[0063] According to an embodiment of the present disclosure, the multiple bulk acoustic wave elements include a second target bulk acoustic wave element, and at least one of the acoustic reflector, bottom electrode, piezoelectric layer, and top electrode included in the second target bulk acoustic wave element is configured to have a shape of a quasi-regular polygon in the overlapping area.
[0064] According to an embodiment of the present disclosure, each side of the quasi-regular polygon is an arc, and the radius of curvature of the arc is configured to be less than the distance from the endpoint of the quasi-regular polygon to the center of the quasi-regular polygon.
[0065] Figure 6A A top view of a second target SAW device according to an embodiment of the present disclosure is schematically shown.
[0066] As Figure 6A shown, the second target SAW device includes a sound reflector 21, a bottom electrode 22, a piezoelectric layer 23, and a top electrode 24. Among them, at least one of the sound reflector 21, the bottom electrode 22, the piezoelectric layer 23, and the top electrode 24 is configured as a quasi-regular polygon. As Figure 6A shown, taking the top electrode 24 as a quasi-regular pentagon and the sound reflector 21, the bottom electrode 22, and the piezoelectric layer 23 as rectangles as an example. Since the edge of the top electrode 24 is within the boundaries of other layers, the shape of the overlapping region is the same as the shape of the top electrode 24, and the shape of the overlapping region is also a quasi-regular pentagon. The outer contour of the top electrode 24 is composed of an outer edge pattern consisting of five circles, which is similar to a Reuleaux pentagon. As Figure 6A shown, the shape of the top electrode 24 also consists of five vertices and five arcs, but the radius of curvature of the arcs is set to be less than the distance from the center of the virtual regular polygon to the vertex, and an arc treatment is made at the graphic endpoints of the top electrode 24. Among them, the virtual regular polygon is a regular polygon formed by taking the endpoints of the quasi-regular polygon as vertices.
[0067] According to an embodiment of the present disclosure, each side of the quasi-regular polygon is an arc, and the radius of curvature of the arc is configured to be greater than the distance from the endpoint of the quasi-regular polygon to the center of the quasi-regular polygon. A Reuleaux polygon can be understood as a virtual regular polygon, or it can be classified as a quasi-polygon, each of its sides is an arc, but the radius of curvature of the arc is set to be greater than the distance from the center of the virtual regular polygon to the vertex.
[0068] Figure 6B A top view of a second target SAW device according to another embodiment of the present disclosure is schematically shown.
[0069] As Figure 6B shown, the second target SAW device includes a sound reflector 21, a bottom electrode 22, a piezoelectric layer 23, and a top electrode 24. Among them, at least one of the sound reflector 21, the bottom electrode 22, the piezoelectric layer 23, and the top electrode 24 is configured as a quasi-regular polygon. As Figure 6B shown, in the figure, taking the top electrode 24 as a quasi-regular pentagon and the sound reflector 21, the bottom electrode 22, and the piezoelectric layer 23 as rectangles as an example. Since the edge of the top electrode 24 is within the boundaries of other layers, the shape of the overlapping region is the same as the shape of the top electrode 24, and the shape of the overlapping region is also a quasi-regular pentagon. The outer contour of the top electrode 24 is composed of an outer edge pattern consisting of five circles, which is similar to a Reuleaux pentagon. As Figure 6BThe shape of the top electrode 24 shown is also composed of five vertices and five arcs, but the radius of curvature of the arcs is set to be greater than the distance from the center of the virtual regular polygon to the vertex, and an arc treatment is made at the graphic end point of the top electrode 24. Among them, the virtual regular polygon is a regular polygon formed by taking the end points of the quasi-regular polygon as vertices.
[0070] Among them, Figure 6A and Figure 6B the area perimeter ratio of the overlapping region of the bulk acoustic wave element shown is also greater than that of the corresponding polygon, and when arranging the architecture, a certain complementary space can be formed with the quasi-Reuleaux polygon.
[0071] According to an embodiment of the present disclosure, each side of the quasi-regular polygon is composed of at least two arcs, and the arcs are at least part of the elliptical curve with the end points of the quasi-regular polygon as the long axis end points.
[0072] Figure 7 A top view of the overlapping region of the bulk acoustic wave element according to an embodiment of the present disclosure is schematically shown.
[0073] As Figure 7 shown, the acoustic reflector 21, the bottom electrode 22, the piezoelectric layer 23, and the top electrode 24 are quasi-regular polygons, Figure 7 the figure formed by the solid lines in is the overlapping region of the quasi-polygon of the bulk acoustic wave element. Each side of the quasi-polygon is composed of at least two arcs. In the figure, two arcs are taken as an example, and each arc is a part of the elliptical curve with the end points of the quasi-regular polygon as the long axis end points. Among them, to ensure the shape of the bulk acoustic wave element is similar to a regular polygon, the number of arcs of the quasi-regular polygon can be set to twice the number of arcs of the regular polygon it resembles.
[0074] According to an embodiment of the present disclosure, the quasi-polygon formed by an ellipse also satisfies the property that the opposite sides of the irregular polygon are not parallel, and can improve the quality factor value of the acoustic filtering device while suppressing the lateral parasitic mode.
[0075] Figure 8 A top view of the acoustic filtering device according to an embodiment of the present disclosure is schematically shown.
[0076] As Figure 8 shown, the acoustic filtering device can be composed of multiple bulk acoustic wave elements. Taking two first target bulk acoustic wave elements and two second target bulk acoustic wave elements as an example, as Figure 8 shown, the two first target bulk acoustic wave elements and the two second target bulk acoustic wave elements are combined to form Figure 8 the acoustic filtering device in. When arranging the above two quasi-Reuleaux pentagons and one quasi-Reuleaux triangle, the arrangement method shown in the figure is selected to better utilize the space, reduce the size of the bulk acoustic wave element, and thus reduce the cost of the acoustic filtering device.
[0077] According to embodiments of the present disclosure, there are various construction methods for Reuleaux polygon-like shapes, which are not limited herein. Here, taking the construction of a Reuleaux triangle-like shape as an example, a method for constructing a Reuleaux polygon-like shape is introduced. The centers of three identical circles are arranged at the vertices of the corresponding regular polygon, and the side length of the polygon is equal to the radius of the circle. The overlapping regions of the multiple circles form the Reuleaux polygon-like shape.
[0078] It should also be noted that although the present disclosure is described with reference to the accompanying drawings, the embodiments disclosed in the drawings are intended to exemplarily illustrate the preferred embodiments of the present disclosure and should not be construed as a limitation of the present disclosure. The dimensional ratios in the drawings are merely illustrative and should not be construed as a limitation of the present disclosure. The directional terms mentioned in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only references to the directions in the drawings and are not used to limit the protection scope of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. When it may cause confusion in the understanding of the present disclosure, conventional structures or configurations will be omitted.
[0079] Moreover, the shapes and sizes of the components in the figures do not reflect the actual sizes and ratios, but only illustrate the content of the embodiments of the present disclosure. Additionally, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claims.
[0080] The ordinal terms used in the description and claims, such as "first", "second", "third", etc., are used to modify the corresponding elements. They do not themselves imply any ordinal number of the elements, nor do they represent the order of one element relative to another or the order in the manufacturing method. The use of these ordinal numbers is only to clearly distinguish one element with a certain name from another element with the same name.
[0081] Furthermore, the word "comprising" or "including" does not exclude the existence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the existence of multiple such elements.
[0082] Unless there are technical obstacles or contradictions, the above various embodiments of the present disclosure can be freely combined to form additional embodiments, and these additional embodiments are all within the protection scope of the present disclosure.
[0083] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc., made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.
Claims
1. An acoustic filtering device, comprising: a substrate, and a plurality of bulk acoustic wave elements disposed on the substrate; wherein, the bulk acoustic wave element is configured to sequentially include an acoustic reflector, a bottom electrode, a piezoelectric layer, and a top electrode from the substrate upward, and the acoustic reflector, the bottom electrode, the piezoelectric layer, and the top electrode have an overlapping region; wherein, the plurality of bulk acoustic wave elements includes at least one first target bulk acoustic wave element, and at least one layer of the acoustic reflector, the bottom electrode, the piezoelectric layer, and the top electrode included in the first target bulk acoustic wave element is configured to have a shape of a Reuleaux polygon in the overlapping region.
2. The device according to claim 1, wherein, the plurality of bulk acoustic wave elements constitute a series arm and a parallel arm of the acoustic filtering device, and the at least one first target bulk acoustic wave element constitutes at least a part of the parallel arm or at least a part of the series arm.
3. The device according to claim 1, wherein, a plurality of end points included in the Reuleaux polygon are all configured to be arc-shaped.
4. The device according to claim 1, wherein, an edge of the overlapping region is configured to be provided with a concave annular structure or a convex annular structure.
5. The device according to claim 1, wherein, the acoustic reflector is configured to be embedded in the substrate, and the acoustic emitter is configured to be a cavity structure.
6. The device according to claim 1, wherein, the acoustic reflector is configured to be embedded in the substrate, and the acoustic emitter is configured to be a Bragg reflection structure formed by alternating multiple layers of materials.
7. The device according to claim 1, wherein, the plurality of bulk acoustic wave elements includes a second target bulk acoustic wave element, and at least one layer of the acoustic reflector, the bottom electrode, the piezoelectric layer, and the top electrode included in the second target bulk acoustic wave element is configured to have a shape of a regular polygon in the overlapping region.
8. The device according to claim 7, wherein, each side of the regular polygon is an arc, and a radius of curvature of the arc is configured to be less than a distance from an end point of the regular polygon to a center of the regular polygon.
9. The device according to claim 7, wherein, each side of the regular polygon is an arc, and a radius of curvature of the arc is configured to be greater than a distance from an end point of the regular polygon to a center of the regular polygon.
10. The device according to claim 7, wherein, each side of the regular polygon is composed of at least two arcs, and the arcs are at least partial curves of an elliptical curve with an end point of the regular polygon as a long axis end point.