Bulk acoustic wave resonator

Abstract

The application discloses a bulk acoustic wave resonator. The bulk acoustic wave resonator comprises a substrate, a reflection structure, a lower electrode, a piezoelectric layer and an upper electrode which are sequentially arranged on the substrate; the piezoelectric layer comprises a central region, and a central axis of the central region is coincident with a central axis of a resonance region of the piezoelectric layer; at least one cavity is arranged around the central region in the piezoelectric layer, and a side wall of the cavity is in an inclined shape relative to an upper surface of the substrate. The application can convert lateral waves into longitudinal waves to improve longitudinal wave energy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resonators, in particular to a bulk acoustic wave resonator. BACKGROUND

[0002] The bulk acoustic wave filter uses the longitudinal resonance of the piezoelectric film to achieve high and low impedance, and thus achieve the filtering effect. The loss is mainly caused by the lateral wave. In addition to reducing the energy of the longitudinal wave, the lateral wave will also form a spurious mode, as shown in the Smith chart, which reduces the performance of the filter. Figure 1

[0003] The prior art mainly forms an irregular resonator shape to make the lateral wave transmission path longer, avoiding spurious resonance, or forms a non-reflective structure at the edge of the resonator to avoid spurious resonance. However, such a device structure can only eliminate or move the lateral wave to a lower frequency, and cannot improve the energy of the longitudinal wave. SUMMARY

[0004] The present application provides a bulk acoustic wave resonator which can convert the lateral wave into a longitudinal wave to improve the energy of the longitudinal wave.

[0005] The present application provides a bulk acoustic wave resonator, comprising a substrate, a reflective structure, a lower electrode, a piezoelectric layer and an upper electrode arranged on the substrate in sequence.

[0006] The piezoelectric layer comprises a central region, and the central axis of the central region coincides with the central axis of the resonant region of the piezoelectric layer; at least one cavity is arranged around the central region in the piezoelectric layer, and the side wall of the cavity is inclined relative to the upper surface of the substrate.

[0007] Preferably, the projection of the cavity on the substrate is a closed shape or a non-closed shape.

[0008] Preferably, the cavity comprises a plurality of holes.

[0009] The plurality of holes are arranged at intervals in the circumferential direction of the central region.

[0010] Preferably, the lengths of different cavities in the direction perpendicular to the upper surface of the substrate are the same or different; the lengths of different cavities in the direction parallel to the upper surface of the substrate are the same or different; the inclination angles of the side walls of different cavities are the same or different; any two adjacent cavities form a cavity pair, and the spacings of different cavity pairs are the same or different.

[0011] Preferably, the length of the cavity in the direction parallel to the upper surface of the substrate ranges from greater than 0.05 um to less than 10 um; and the spacing of any two adjacent cavities ranges from greater than 0.05 um to less than 10 um.​

[0012] Preferably, the piezoelectric layer further comprises a tuning region surrounding the central region, and the cavity is located in the tuning region.

[0013] The tuning region has a different acoustic impedance from the central region, and a first interface between the tuning region and the central region is inclined with respect to the upper surface of the substrate.

[0014] Preferably, the tuning region comprises a plurality of sub-regions surrounding the central region, and at least one of the sub-regions has the cavity.

[0015] The central region has a different acoustic impedance from its adjacent sub-region, any two adjacent sub-regions have different acoustic impedances, and a second interface between any two adjacent sub-regions is inclined with respect to the upper surface of the substrate.

[0016] Preferably, the number of cavities in different sub-regions is the same or different; the length of the cavities in different sub-regions in a direction perpendicular to the upper surface of the substrate is the same or different; the length of the cavities in different sub-regions in a direction parallel to the upper surface of the substrate is the same or different; the inclination angle of the side wall of the cavities in different sub-regions is different; and the distance between two adjacent cavities in different sub-regions is the same or different.

[0017] Preferably, the volume ratio of the cavities in any two adjacent sub-regions is different.

[0018] Preferably, the cavities are filled with air or a material having a different acoustic impedance from the sub-region in which the cavity is located.

[0019] Preferably, the at least one cavity is located in a resonant region of the piezoelectric layer.

[0020] Alternatively, the at least one cavity is partially located in a resonant region of the piezoelectric layer and partially located outside the resonant region of the piezoelectric layer.

[0021] Alternatively, the at least one cavity is located outside a resonant region of the piezoelectric layer.

[0022] The present application has the following beneficial effects: by providing at least one cavity surrounding the central region in the piezoelectric layer, since the cavity has a different acoustic impedance from the piezoelectric layer and the side wall of the cavity is inclined with respect to the upper surface of the substrate, the travel path of the lateral wave generated by the central region is changed by the cavity, the lateral wave is converted into a longitudinal wave, the lateral energy is converted into longitudinal resonant energy, thereby improving the longitudinal wave energy and improving the performance of the resonator. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A Smith chart of a bulk acoustic resonator in the prior art;

[0025] Figure 2 A first cross-sectional schematic view of a bulk acoustic resonator provided by an embodiment of the present application;

[0026] Figure 3 A second cross-sectional schematic view of a bulk acoustic resonator provided by an embodiment of the present application;

[0027] Figure 4 A third cross-sectional schematic view of a bulk acoustic resonator provided by an embodiment of the present application;

[0028] Figure 5 A first cross-sectional schematic view of a piezoelectric layer in a bulk acoustic resonator provided by an embodiment of the present application;

[0029] Figure 6 A top view of a cavity in a bulk acoustic resonator provided by an embodiment of the present application;

[0030] Figure 7 A top view of a bulk acoustic resonator provided by an embodiment of the present application;

[0031] Figure 8 A fourth cross-sectional schematic view of a bulk acoustic resonator provided by an embodiment of the present application;

[0032] Figure 9 A fifth cross-sectional schematic view of a bulk acoustic resonator provided by an embodiment of the present application;

[0033] Figure 10 A sixth cross-sectional schematic view of a bulk acoustic resonator provided by an embodiment of the present application;

[0034] Figure 11 A second cross-sectional schematic view of a piezoelectric layer in a bulk acoustic resonator provided by an embodiment of the present application. DETAILED DESCRIPTION

[0035] The specific structure and function details disclosed herein are merely representative, and are for the purpose of describing exemplary embodiments of the present application. However, the present application can be embodied in many alternative forms, and should not be interpreted as being limited to only the embodiments set forth herein.

[0036] In the description of the present application, it needs to be understood that the terms "center", "transverse", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can be explicitly or implicitly included one or more of the features. In the description of the present application, unless otherwise specified and limited, the term "a plurality of" means two or more. In addition, the term "includes" and any variations thereof are intended to cover non-exclusive inclusion.

[0037] In the description of the present application, it needs to be understood that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The terms used herein are only used to describe specific embodiments and are not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular form "a", "an" used herein is also intended to include the plural. It should also be understood that the terms "include" and / or "contain" used herein specify the existence of the stated features, integers, steps, operations, units and / or components, and do not exclude the existence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0039] Reference Figure 2 is a structural schematic diagram of a bulk acoustic wave resonator provided by an embodiment of the present application.

[0040] As Figure 2 shown, the bulk acoustic wave resonator provided by the embodiment of the present application includes a substrate 1, and a reflection structure 2, a lower electrode 3, a piezoelectric layer 4 and an upper electrode 5 arranged in sequence on the substrate 1. The reflection structure 2 is located on the substrate 1, the lower electrode 3 is located on the reflection structure 2, the piezoelectric layer 4 is located on the lower electrode 3, the reflection structure 2 and the substrate 1, and the upper electrode 5 is located on the piezoelectric layer 4. In combination with Figure 7As shown, the bulk acoustic wave resonator can further include an upper electrode lead 6 and a lower electrode lead 7. The upper electrode lead 6 is arranged in the same layer as the upper electrode 5 and is connected to the upper electrode 5. The lower electrode lead 7 is arranged in the same layer as the lower electrode 3 and is connected to the lower electrode 3.

[0041] The reflection structure 2 can be located above the substrate 1 or inside the substrate 1 close to the upper surface of the substrate 1. The reflection structure 2 can be a cavity or a reflector, such as a Bragg reflector. When the reflection structure 2 is a cavity, a sacrificial layer (not shown in the figure) can be formed on the substrate 1 first, for example, a sacrificial layer is formed above the substrate 1, or a groove is formed in the substrate 1 and the sacrificial layer is filled in the groove. The sacrificial layer can have a side wall that is inclined with respect to the upper surface of the substrate 1, and the inclination angle of the side wall can be 35 degrees. Since the sacrificial layer is a transition material, after the lower electrode 3, the piezoelectric layer 4 and the upper electrode 5 are sequentially formed on the substrate 1 and the sacrificial layer, the sacrificial layer can be released by a release hole to form a cavity at the sacrificial layer. The longitudinal section of the cavity can be isosceles trapezoidal, and the base angle of the isosceles trapezoid can be 35°.

[0042] The substrate 1 can be silicon, glass, sapphire, gallium nitride, gallium arsenide, lithium niobate, lithium tantalate, etc. The materials of the lower electrode 3 and the lower electrode lead 7 can be the same, for example, one or more combinations of molybdenum, tungsten, chromium, aluminum, copper, ruthenium, graphene, carbon nanotubes. The shape of the orthographic projection of the lower electrode 3 on the substrate 1 includes any one or more combinations of semicircle, triangle, rectangle and irregular polygon. The piezoelectric layer 4 has a crystal of <002> preferably, which can be aluminum nitride, zinc oxide, lead zirconate titanate, or the above-mentioned materials doped with rare earth elements. The materials of the upper electrode 5 and the upper electrode lead 6 can be the same, for example, one or more combinations of molybdenum, tungsten, chromium, aluminum, copper, ruthenium, graphene, carbon nanotubes. The shape of the orthographic projection of the upper electrode 5 on the substrate 1 includes any one or more combinations of semicircle, triangle, rectangle and irregular polygon.

[0043] The bulk acoustic wave resonator includes a resonance region A and a non-resonance region outside the resonance region A. The resonance region A refers to a region that vibrates in a predetermined direction to produce resonance by the piezoelectric phenomenon when electrical energy is applied to the lower electrode 3 and the upper electrode 5 to induce an electric field in the piezoelectric layer 4, for example, the region where the reflection structure 2, the lower electrode 3, the piezoelectric layer 4 and the upper electrode 5 overlap is the resonance region A. The non-resonance region refers to a region other than the resonance region A.

[0044] As Figures 2 to 4As shown, the piezoelectric layer 4 includes a center region C. The central axis of the center region C coincides with the central axis of the resonance region A of the piezoelectric layer 4, as shown in FIG. 1C. The center region C can be located within the resonance region A of the piezoelectric layer 4, as shown in FIG. 1D, or the resonance region A of the piezoelectric layer 4 can be located within the center region C, as shown in FIG. 1E. Figure 2 The normal projection of the center region C on the substrate 1 can have the same shape as the normal projection of the resonance region A on the substrate 1, but can have a different size. The resonance region A of the piezoelectric layer 4 can include the center region C, i.e., the center region C is located within the resonance region A of the piezoelectric layer 4, as shown in FIG. 1D. Figure 2 The resonance region A of the piezoelectric layer 4 can also include the center region C, i.e., the resonance region A of the piezoelectric layer 4 completely coincides with the center region C or the resonance region A of the piezoelectric layer 4 is located within the center region C, as shown in FIG. 1E. Figure 3 The resonance region A of the piezoelectric layer 4 can also include the center region C, i.e., the resonance region A of the piezoelectric layer 4 completely coincides with the center region C or the resonance region A of the piezoelectric layer 4 is located within the center region C, as shown in FIG. 1E. Figure 4 The resonance region A of the piezoelectric layer 4 can also include the center region C, i.e., the resonance region A of the piezoelectric layer 4 completely coincides with the center region C or the resonance region A of the piezoelectric layer 4 is located within the center region C, as shown in FIG. 1E.

[0045] The piezoelectric layer 4 includes at least one cavity 8, and each cavity 8 is arranged around the center region C. Since the center region C can be located within the resonance region A of the piezoelectric layer 4 or can include the resonance region A of the piezoelectric layer 4, all the cavities 8 can be located within the resonance region A of the piezoelectric layer 4, or part of the cavities 8 are located within the resonance region A of the piezoelectric layer 4 and the remaining cavities 8 are located outside the resonance region A of the piezoelectric layer 4, or all the cavities 8 are located outside the resonance region A of the piezoelectric layer 4. As shown in FIG. 1F, when the center region C is located within the resonance region A of the piezoelectric layer 4, three cavities 8 are arranged in the piezoelectric layer 4, and all the three cavities 8 are located within the resonance region A of the piezoelectric layer 4. Figure 2 As shown in FIG. 1G, when the center region C is located within the resonance region A of the piezoelectric layer 4, three cavities 8 are arranged in the piezoelectric layer 4, i.e., 8a, 8b, and 8c. The cavity 8a is located within the resonance region A of the piezoelectric layer 4, the cavity 8b is partially located within the resonance region A of the piezoelectric layer 4 and the remaining part is located outside the resonance region A of the piezoelectric layer 4, and the cavity 8c is located outside the resonance region A of the piezoelectric layer 4. Figure 3 As shown in FIG. 1H, when the center region C includes the resonance region A of the piezoelectric layer 4, three cavities 8 are arranged in the piezoelectric layer 4, and all the three cavities 8 are located outside the resonance region A of the piezoelectric layer 4. Figure 4

[0046] It should be noted that when the center region C is located within the resonance region A of the piezoelectric layer 4, the area of the center region C cannot be too small to avoid the cavities 8 being too close to the center of the resonance region A and affecting the performance of the resonator.

[0047] The side wall of the cavity 8 is inclined relative to the upper surface of the substrate 1, and the cavity 8 can be filled with air or filled with a material having a different acoustic impedance from the center region C, so that the acoustic impedance of the cavity 8 is different from that of the center region C, thereby ensuring that the lateral wave generated in the center region C is converted into a longitudinal wave through the cavity 8. The acoustic impedance of the cavity 8 can be greater than or less than the acoustic impedance of the center region C, which is not limited here.

[0048] ​The acoustic impedance can be expressed as Z = p x v, where p is the density of the material and v is the speed of sound transmission in the material, which can also be expressed as c is the modulus of elasticity of the material. It can be seen that a lower acoustic impedance requires a material with low density and low sound speed, and a higher acoustic impedance requires a material with high density and high sound speed.

[0049] When the material in the cavity 8 is filled, the material in the center region C can be the same as or different from the material filled in the cavity 8. When the material in the center region C is the same as the material filled in the cavity 8, the density and sound speed of the center region C and the material filled in the cavity 8 are made different by doping the material in the center region C or the material filled in the cavity 8, so that the acoustic impedance of the center region C and the cavity 8 is different. The material in the center region C and the material filled in the cavity 8 can be a piezoelectric material, such as zinc oxide, aluminum nitride, lead zirconate titanate, lead scandium tantalate, or bismuth sodium titanate, etc. The material filled in the cavity 8 can also be a non-piezoelectric material, preferably a reflective material, such as a high acoustic impedance material or a low acoustic impedance material. Among them, the high acoustic impedance material can be molybdenum, tungsten, cadmium or ruthenium, etc.; the low acoustic impedance material can be silicon dioxide, aluminum, zinc, etc.

[0050] The side wall of each cavity 8 can be inclined to the direction F1 of the center region C, as shown in Figure 2 and Figure 4 The side wall of the cavity 8 can also be inclined to the direction F2 away from the center region C, as shown in Figure 3 The inclination angle θ1 of the side wall of the cavity 8 is the included angle between the side wall of the cavity 8 and the upper surface of the substrate 1, which is an acute angle, i.e. 0° < θ1 < 90°. The inclination angles θ1 of the side walls of different cavities 8 are the same or different, as shown in Figure 5 The inclination angles θ1 of the cavities 8e and 8g are the same, and the inclination angles θ1 of the cavities 8d, 8e and 8f are different.

[0051] The extension depth of different cavities 8 can be different, i.e. the cavities 8 can penetrate through the piezoelectric layer 4 or be located within the piezoelectric layer 4. As shown in Figure 5 The cavity 8e penetrates through the piezoelectric layer 4, the top and bottom of the cavity 8d are located within the piezoelectric layer 4, the top of the cavity 8g is located within the piezoelectric layer 4, and the bottom extends to the bottom surface of the piezoelectric layer 4, the bottom of the cavity 8f is located within the piezoelectric layer 4, and the top extends to the top surface of the piezoelectric layer 4. Since the extension depth of different cavities 8 can be different, the length H of different cavities 8 in the direction F3 perpendicular to the upper surface of the substrate 1 can be the same or different. As shown in Figure 5 The lengths H of the cavities 8f and 8g in the direction F3 perpendicular to the upper surface of the substrate 1 are the same, and the lengths H of the cavities 8d, 8e and 8f in the direction F3 perpendicular to the upper surface of the substrate 1 are different.

[0052] Different cavities 8 may have the same or different lengths Q along the direction F4 parallel to the upper surface of substrate 1. For example... Figure 5 As shown, cavities 8e and 8g have the same length Q in the direction F4 parallel to the upper surface of substrate 1, while cavities 8d, 8e, and 8f have different lengths Q in the same direction F4. Preferably, the length Q of cavity 8 in the direction F4 parallel to the upper surface of substrate 1 is greater than 0.05 μm and less than 10 μm, i.e., 0.05 μm < Q < 10 μm.

[0053] Any two adjacent cavities 8 form a cavity pair. The spacing P between the cavities 8 in different cavity pairs may be the same or different. The spacing P between the cavities in a cavity pair refers to the shortest distance between the two cavities in the cavity pair along the direction F4 parallel to the upper surface of the substrate 1. Figure 5 As shown, cavities 8d and 8e form a first cavity pair, cavities 8e and 8f form a second cavity pair, and cavities 8f and 8g form a third cavity pair. The distance P between cavities 8d and 8e in the first cavity pair is the same as the distance P between cavities 8f and 8g in the third cavity pair. The distance P between cavities 8d and 8e in the first cavity pair is different from the distance P between cavities 8e and 8f in the second cavity pair. Preferably, the distance P between any two adjacent cavities 8 is greater than 0.05 μm and less than 10 μm, i.e., 0.05 μm < P < 10 μm.

[0054] Each cavity 8 is arranged around the central region C. The orthographic projection of each cavity 8 onto the substrate 1 can be a closed shape or a non-closed shape. The shapes of the orthographic projections of different cavities 8 onto the substrate 1 can be the same or different. Specifically, the cavity 8 can be a closed structure, such that the orthographic projection of the cavity 8 onto the substrate 1 is a closed shape. This closed shape can be annular, rectangular, irregular polygonal, etc. Figure 6 As shown, the orthographic projection of cavity 8h onto substrate 1 is a closed shape. Cavity 8 can also be a non-closed structure with an opening, such that the orthographic projection of cavity 8 onto substrate 1 is a non-closed shape with an opening, for example, an annular, rectangular, or irregular polygon with an opening. Preferably, the width of the opening (i.e., the length of the opening in the circumferential direction B of the central region C) is greater than 0.05 μm and less than 10 μm. Figure 6 As shown, the orthographic projection of cavity 8i onto substrate 1 is a non-closed shape with an opening.

[0055] The cavity 8 may also include multiple holes 81, which are spaced apart on the circumferential direction B of the central region C. Preferably, the length of two adjacent holes 81 on the circumferential direction B of the central region C is greater than 0.05 μm and less than 10 μm. Figure 6 As shown, the cavity 8j includes three holes 81, and the three holes 81 are spaced apart in the circumferential direction of the central region C.

[0056] like Figure 7 As shown, the piezoelectric layer 4 also includes an adjustment region D, which surrounds the central region C and is adjacent to the central region C. The adjustment region D refers to the area where the acoustic impedance of the piezoelectric layer 4 can be adjusted. Combined with... Figure 8 As shown, Figure 8 for Figure 7 The cross-sectional diagram at the dashed line OO' shows that cavity 8 is located within adjustment area D and surrounds central area C. Adjustment area D can be a single zone, or it can be divided into multiple zones, meaning adjustment area D can include multiple zones, which are sequentially arranged around central area C, with central area C and the multiple zones being sequentially adjacent. Figure 11 As shown, the adjustment area D includes four partitions: partition D1, partition D2, partition D3, and partition D4. Partition D1 is set around the central area C and is adjacent to the central area C; partition D2 is set around partition D1 and is adjacent to partition D1; partition D3 is set around partition D2 and is adjacent to partition D2; and partition D4 is set around partition D3 and is adjacent to partition D3.

[0057] Since the central region C can be located within or include the resonant region A of the piezoelectric layer 4, the adjustment region D can also be located within the resonant region A of the piezoelectric layer 4. Figure 9 As shown; the adjustment region D can be partially located within the resonant region A of the piezoelectric layer 4, with the remaining portion located outside the resonant region A of the piezoelectric layer 4, as shown. Figure 8 As shown; the adjustment region D can be located outside the resonant region A of the piezoelectric layer 4, such as... Figure 10 As shown. When the adjustment region D includes multiple partitions, all partitions can be located within the resonant region A of the piezoelectric layer 4; all partitions can be located outside the resonant region A of the piezoelectric layer 4; some partitions can be located within the resonant region A of the piezoelectric layer 4, and the remaining partitions can be located outside the resonant region A of the piezoelectric layer 4.

[0058] Furthermore, the central region C and the adjustment region D may only cover a portion of the piezoelectric layer 4; that is, the piezoelectric layer 4 may also include an outer region surrounding the adjustment region D. The material of the outer region can be the same as that of the central region C, and the acoustic impedance of the outer region can be the same as that of the central region C. Alternatively, the central region C and the adjustment region D may completely cover the piezoelectric layer 4, meaning the outer boundary of the adjustment region D is the sidewall of the piezoelectric layer 4, such as... Figure 11 As shown.

[0059] like Figures 7 to 10 As shown, the acoustic impedance of the central region C and the adjustment region D are different, and the first interface E1 between the central region C and the adjustment region D is inclined relative to the upper surface of the substrate 1.

[0060] The acoustic impedance difference between the central region C and the adjustment region D is greater than 0. That is, the acoustic impedance of the central region C can be greater than that of the adjustment region D, or the acoustic impedance of the central region C can be less than that of the adjustment region D, as long as the acoustic impedances of the central region C and the adjustment region D are different. Preferably, the acoustic impedance of the central region C is less than that of the adjustment region D.

[0061] The materials of the central region C and the adjustment region D can be the same or different. When the materials of the central region C and the adjustment region D are the same, doping of either the central region C or the adjustment region D can create differences in the density and sound velocity of the materials in the central region C and the adjustment region D, thereby ensuring that the acoustic impedances of the central region C and the adjustment region D are different. The materials of the central region C and the adjustment region D can be piezoelectric materials, and the material of the adjustment region D can also be a non-piezoelectric material. Preferably, when the material of the central region C is aluminum nitride, the difference between the acoustic impedance of the central region C and the acoustic impedance of the adjustment region D is greater than 1 × 10⁻⁶. 6 kg / m 4 s.

[0062] The cavity 8 can be filled with air or a material with a different acoustic impedance than that of the adjustment area D, so that the acoustic impedance of the cavity 8 is different from that of the adjustment area D. The acoustic impedance of the cavity 8 can be greater than that of the adjustment area D, or it can be less than that of the adjustment area D; no specific limitation is made here.

[0063] When filling cavity 8 with material, the material of adjustment region D can be the same as or different from the material filling cavity 8. When the material of adjustment region D and the material filling cavity 8 are the same, doping can be performed on either material to make their densities and sound velocities different, thus ensuring different acoustic impedances between the two. The material of adjustment region D and the material filling cavity 8 can be piezoelectric or non-piezoelectric materials, but when the material of adjustment region D is piezoelectric, the material filling cavity 8 is non-piezoelectric.

[0064] The first interface E1 between the central region C and the adjustment region D can be tilted towards the central region C in the direction F1, such as... Figure 9 and Figure 10 As shown, the upper surface area of ​​the central region C is smaller than the lower surface area of ​​the central region C. The first interface E1 between the central region C and the adjustment region D can also be tilted in the direction F2 away from the central region C, as shown. Figure 8 As shown, the upper surface area of ​​the central region C is greater than the lower surface area of ​​the central region C. The first interface E1 can be a plane or a curved surface. When the first interface E1 is a plane, as shown... Figure 8As shown, the inclination angle θ2 of the first interface E1 is the included angle between the first interface E1 and the upper surface of the substrate 1, which is an acute angle, i.e. 0° < θ2 < 90°. When the first interface E1 is a curved surface, the first interface E1 can be convex in the direction F1 of the central region C, or convex in the direction F2 away from the central region C, as shown in FIG. 2B. Figure 9 As shown, the inclination angle θ2 of the first interface E1 is the tangent angle at the position of the largest curvature radius of the first interface E1. Preferably, 30° < θ2 < 60°.

[0065] When the adjustment region D includes multiple sub-regions, the cavity 8 is provided in at least one sub-region, i.e. the cavity 8 can be provided in all sub-regions, or the cavity 8 is provided in part of the sub-regions and not provided in the remaining sub-regions. The acoustic impedance of the central region C is different from that of its adjacent sub-regions, and the acoustic impedance of any two adjacent sub-regions is different. As shown in FIG. 2A, Figure 11 As shown, the cavity 8 is not provided in the sub-region D2, and the cavity 8 is provided in the sub-regions D1, D3 and D4. In addition, the acoustic impedance of the central region C is different from that of the sub-region D1, the acoustic impedance of the sub-region D1 is different from that of the sub-region D2, the acoustic impedance of the sub-region D2 is different from that of the sub-region D3, and the acoustic impedance of the sub-region D3 is different from that of the sub-region D4. The acoustic impedance of the sub-regions that are spaced apart can be the same or different, such as the acoustic impedance of the sub-region D1 can be the same as or different from that of the sub-region D3 and the sub-region D4, and the acoustic impedance of the sub-region D2 can be the same as or different from that of the sub-region D4. The acoustic impedance of the central region C can be the same as or different from that of its adjacent sub-regions, such as the acoustic impedance of the central region C can be the same as or different from that of the sub-region D2, the sub-region D3 and the sub-region D4.

[0066] The acoustic impedance of the central region C can be smaller than that of the adjustment region D, and in the direction F1 towards the central region C, the acoustic impedance of the multiple sub-regions can gradually decrease, such as the acoustic impedance of the sub-region D4, the sub-region D3, the sub-region D2, the sub-region D1 and the central region C gradually decreases. The acoustic impedance of the central region C can also be greater than that of the adjustment region D, and in the direction F1 towards the central region C, the acoustic impedance of the multiple sub-regions can gradually increase, such as the acoustic impedance of the sub-region D4, the sub-region D3, the sub-region D2, the sub-region D1 and the central region C gradually increases.

[0067] The material of the center region C and the adjustment region D can be the same or different, i.e., the material of the center region C and any of the sub-regions can be the same or different, and the materials of different sub-regions can be the same or different, such as the materials of the center region C, the sub-region D1, the sub-region D2, the sub-region D3, and the sub-region D4 can be the same or different. When the materials of the center region C and the sub-region D1 are the same, the density and the sound speed of the materials in the center region C and the sub-region D1 are made different by doping the material of the sub-region D1, so as to ensure that the acoustic impedance of the center region C and the sub-region D1 is different. When the materials of two adjacent sub-regions are the same, the density and the sound speed of the materials in any of the two adjacent sub-regions are made different by doping the material of the sub-region, so as to ensure that the acoustic impedance of the two adjacent sub-regions is different. The materials of the center region C and each sub-region can be piezoelectric materials, and the materials of each sub-region can also be non-piezoelectric materials.

[0068] The cavity 8 can be filled with air or filled with a material different from the acoustic impedance of the sub-region where the cavity 8 is located, so that the acoustic impedance of the cavity 8 is different from the acoustic impedance of the sub-region where the cavity 8 is located. The acoustic impedance of the cavity 8 can be greater than the acoustic impedance of the sub-region where the cavity 8 is located, and the acoustic impedance of the cavity 8 can also be less than the acoustic impedance of the sub-region where the cavity 8 is located, which is not specifically limited here. As shown in FIG. 1, the acoustic impedance of the cavity 8k is different from the acoustic impedance of the sub-region D1 where the cavity 8k is located, the acoustic impedance of the cavity 8l and the cavity 8m is different from the acoustic impedance of the sub-region D3 where the cavity 8l and the cavity 8m are located, and the acoustic impedance of the cavity 8n and the cavity 8o is different from the acoustic impedance of the sub-region D4 where the cavity 8n and the cavity 8o are located. Figure 11 As shown in FIG. 1, the acoustic impedance of the cavity 8k is different from the acoustic impedance of the sub-region D1 where the cavity 8k is located, the acoustic impedance of the cavity 8l and the cavity 8m is different from the acoustic impedance of the sub-region D3 where the cavity 8l and the cavity 8m are located, and the acoustic impedance of the cavity 8n and the cavity 8o is different from the acoustic impedance of the sub-region D4 where the cavity 8n and the cavity 8o are located.

[0069] When the cavity 8 is filled with a material, the material filled in the cavity 8 can be the same as or different from the material of the sub-region where the cavity 8 is located. When the material filled in the cavity 8 is the same as the material of the sub-region where the cavity 8 is located, the density and the sound speed of the material filled in the cavity 8 and the material of the sub-region where the cavity 8 is located are made different by doping the material filled in the cavity 8 or the material of the sub-region where the cavity 8 is located, so as to ensure that the acoustic impedance of the cavity 8 and the sub-region where the cavity 8 is located is different.

[0070] The minimum lengths L of different sub-regions in the direction F4 parallel to the upper surface of the substrate 1 are the same or different, such as Figure 11 As shown in FIG. 1, the minimum lengths L of the sub-region D1, the sub-region D2, the sub-region D3, and the sub-region D4 in the direction F4 parallel to the upper surface of the substrate 1 can be the same or different. In the direction F1 toward the center region C, the minimum lengths L of the plurality of sub-regions can gradually decrease, or the minimum lengths L of the plurality of sub-regions can gradually increase.

[0071] In addition, when the center region C includes the resonant region A of the piezoelectric layer 4, i.e., the resonant region A of the piezoelectric layer 4 is located in the center region C, the adjustment region D is located outside the resonant region A of the piezoelectric layer 4, the first interface E1 between the center region C and the adjustment region D is located outside the resonant region A of the piezoelectric layer 4, and the spacing between the first interface E1 and the resonant region A of the piezoelectric layer 4 matches the wavelength of the lateral wave. As shown in FIG. 1, the resonant region A of the piezoelectric layer 4 is located in the center region C, the adjustment region D is located outside the resonant region A of the piezoelectric layer 4, the first interface E1 between the center region C and the adjustment region D is located outside the resonant region A of the piezoelectric layer 4, and the spacing between the first interface E1 and the resonant region A of the piezoelectric layer 4 matches the wavelength of the lateral wave. Figure 10As shown, the distance between the first interface E1 and the resonance region A of the piezoelectric layer 4 is L0, which is matched with the wavelength of the lateral wave. Preferably, 50nm < L0 < 10um.

[0072] The first interface E1 of the central region C and the adjustment region D (i.e. the interface of the central region C and its adjacent sub-region) is inclined relative to the upper surface of the substrate 1, and the second interface E2 of any two adjacent sub-regions is inclined relative to the upper surface of the substrate 1. As shown, Figure 11 As shown, the first interface E1 of the central region C and the sub-region D1, the second interface E2 of the sub-region D1 and the sub-region D2, the second interface E2 of the sub-region D2 and the sub-region D3, and the second interface E2 of the sub-region D3 and the sub-region D4 are all inclined relative to the upper surface of the substrate 1. The first interface E1 and the second interface E2 can be inclined towards the direction F1 of the central region C, or can be inclined away from the direction F2 of the central region C.

[0073] The first interface E1 and the second interface E2 can be planar or curved. The first interface E1 and the second interface E2 can be planar at the same time, the first interface E1 and the second interface E2 can be curved at the same time, the first interface E1 and the second interface E2 can be partially planar and partially curved.

[0074] As shown, Figure 11 The inclination angle of the second interface E2 is θ3. When the second interface E2 is planar, the inclination angle θ3 is the included angle (acute angle) between the second interface E2 and the upper surface of the substrate 1. When the second interface E2 is curved, the second interface E2 can be convex towards the direction F1 of the central region C, or can be convex away from the direction F2 of the central region C, and the inclination angle θ3 is the tangent angle at the maximum curvature radius of the second interface E2. Preferably, 30° < θ3 < 60°.

[0075] The number of cavities 8 in different sub-regions is the same or different. As shown, Figure 11 As shown, there is one cavity 8k in the sub-region D1, there are two cavities 8l, 8m in the sub-region D3, there are two cavities 8n, 8o in the sub-region D4, and there is no cavity in the sub-region D2.

[0076] The length H of the cavities 8 in different sub-regions in the direction F3 perpendicular to the upper surface of the substrate 1 is the same or different. As shown, Figure 11 As shown, the length H of the cavity 8k in the sub-region D1 and the cavity 8n in the sub-region D4 in the direction F3 perpendicular to the upper surface of the substrate 1 is the same, and the length H of the cavity 8k in the sub-region D1, the cavities 8l, 8m in the sub-region D3 and the cavity 8o in the sub-region D4 in the direction F3 perpendicular to the upper surface of the substrate 1 is different. When a sub-region has multiple cavities 8, the length H of the multiple cavities 8 in the sub-region in the direction F3 perpendicular to the upper surface of the substrate 1 is the same or different. As shown, Figure 11As shown, the lengths H of the two cavities 8l, 8m in the partition D3 in the direction F3 perpendicular to the upper surface of the substrate 1 are different, and the lengths H of the two cavities 8n, 8o in the partition D4 in the direction F3 perpendicular to the upper surface of the substrate 1 are different.

[0077] The lengths Q of the cavities 8 in different partitions in the direction F4 parallel to the upper surface of the substrate 1 are the same or different. As shown, Figure 11 As shown, the lengths Q of the cavity 8l in the partition D3 and the cavities 8n, 8o in the partition D4 in the direction F4 parallel to the upper surface of the substrate 1 are the same, and the lengths Q of the cavity 8k in the partition D1 and the cavities 8l, 8m in the partition D3 and the cavities 8n, 8o in the partition D4 in the direction F4 parallel to the upper surface of the substrate 1 are different. When there are multiple cavities 8 in one partition, the lengths Q of the multiple cavities 8 in the partition in the direction F4 parallel to the upper surface of the substrate 1 are the same or different. As shown, Figure 11 As shown, the lengths Q of the two cavities 8l, 8m in the partition D3 in the direction F4 parallel to the upper surface of the substrate 1 are different, and the lengths Q of the two cavities 8n, 8o in the partition D4 in the direction F4 parallel to the upper surface of the substrate 1 are the same.

[0078] The inclination angles θ1 of the side walls of the cavities 8 in different partitions are the same or different. As shown, Figure 11 As shown, the inclination angles θ1 of the side walls of the cavity 8k in the partition D1 and the cavities 8l, 8m in the partition D3 and the cavities 8n, 8o in the partition D4 are different, and the inclination angles θ1 of the side walls of the cavity 8l in the partition D3 and the cavity 8o in the partition D4 are the same. When there are multiple cavities 8 in one partition, the inclination angles θ1 of the side walls of the multiple cavities 8 in the partition are the same or different. As shown, Figure 11 As shown, the inclination angles θ1 of the side walls of the two cavities 8l, 8m in the partition D3 are different, and the inclination angles θ1 of the side walls of the two cavities 8n, 8o in the partition D4 are different.

[0079] When there are multiple cavities 8 in a partition, the spacings P of two adjacent cavities in different partitions are the same or different. As shown, Figure 11 As shown, there are two cavities 8l, 8m in the partition D3, and there are two cavities 8n, 8o in the partition D4, and the spacing P of the two cavities 8l, 8m in the partition D3 is different from the spacing P of the two cavities 8n, 8o in the partition D4.

[0080] The volume ratios of the cavities in any two adjacent partitions are different. The volume ratio of the cavities in a partition refers to the ratio of the total volume of all cavities in the partition to the volume of the partition. As shown, Figure 11 Figure 11 Figure 11As shown, the cavity 8 is not present in the partition D2, so the volume ratio of the cavity in the partition D2 is 0; the volume ratio of the cavity in the partition D1 is the ratio of the volume of the cavity 8k to the volume of the partition D1; the volume ratio of the cavity in the partition D3 is the ratio of the total volume of the two cavities 8l and 8m to the volume of the partition D3; and the volume ratio of the cavity in the partition D4 is the ratio of the total volume of the two cavities 8n and 8o to the volume of the partition D4. The volume ratios of the cavities in the partition D1 and the partition D2 are different, the volume ratios of the cavities in the partition D2 and the partition D3 are different, and the volume ratios of the cavities in the partition D3 and the partition D4 are different. The volume ratios of the cavities in the partitions that are spaced apart can be the same or different, such as the volume ratios of the cavities in the partition D1 and the partition D3 can be the same or different, and the volume ratios of the cavities in the partition D1 and the partition D4 can be the same or different.

[0081] From the above, the body acoustic wave resonator provided by the embodiment of the present application changes the travel path of the lateral wave generated by the central region through the cavity by setting at least one cavity surrounding the central region in the piezoelectric layer, converts the lateral wave into longitudinal wave, converts the lateral energy into longitudinal resonance energy, thereby improving the longitudinal wave energy and the performance of the resonator, because the acoustic impedance of the cavity and the piezoelectric layer is different, and the side wall of the cavity is inclined relative to the upper surface of the substrate.

[0082] To sum up, although the present application has been disclosed as above with preferred embodiments, the above preferred embodiments are not used to limit the present application, and those skilled in the art can make various changes and decorations without departing from the spirit and scope of the present application, so the protection scope of the present application is subject to the scope defined by the claims.

Claims

1. A bulk acoustic resonator, characterized in that, The device includes a substrate, a reflective structure, a lower electrode, a piezoelectric layer, and an upper electrode sequentially disposed on the substrate. The piezoelectric layer includes a central region, the central axis of which coincides with the central axis of the resonant region of the piezoelectric layer; the piezoelectric layer has at least one cavity surrounding the central region, the sidewalls of which are parallel to each other and inclined relative to the upper surface of the substrate; The piezoelectric layer further includes an adjustment region surrounding the central region, the cavity being located within the adjustment region, the adjustment region having a different acoustic impedance from the central region, and the first interface between the adjustment region and the central region being inclined relative to the upper surface of the substrate. The adjustment area includes multiple partitions arranged around the central area, at least one of the partitions having the cavity, the acoustic impedance of the central area and its adjacent partitions being different, the acoustic impedance of any two adjacent partitions being different, the acoustic impedance of the cavity being different from that of its partition, and the second interface between any two adjacent partitions being inclined relative to the upper surface of the substrate.

2. The bulk acoustic resonator according to claim 1, characterized in that, The cavity's orthogonal projection onto the substrate is either a closed shape or a non-closed shape.

3. The bulk acoustic resonator according to claim 2, characterized in that, The cavity includes multiple holes; The plurality of holes are spaced apart circumferentially in the central area.

4. The bulk acoustic resonator according to claim 1, characterized in that, The different cavities may have the same or different lengths in the direction perpendicular to the upper surface of the substrate; the different cavities may have the same or different lengths in the direction parallel to the upper surface of the substrate; the different cavities may have the same or different inclination angles of their sidewalls; any two adjacent cavities constitute a cavity pair, and the cavity spacing in different cavity pairs may be the same or different.

5. The bulk acoustic resonator according to claim 4, characterized in that, The length of the cavity in the direction parallel to the upper surface of the substrate is greater than 0.05 μm and less than 10 μm; the distance between any two adjacent cavities is greater than 0.05 μm and less than 10 μm.

6. The bulk acoustic resonator according to claim 1, characterized in that, The number of cavities in different partitions may be the same or different; the length of the cavities in different partitions may be the same or different in the direction perpendicular to the upper surface of the substrate; the length of the cavities in different partitions may be the same or different in the direction parallel to the upper surface of the substrate; the inclination angle of the sidewalls of the cavities in different partitions may be different; the spacing between two adjacent cavities in different partitions may be the same or different.

7. The bulk acoustic resonator according to claim 6, characterized in that, The volume ratio of the cavity in any two adjacent partitions is different.

8. The bulk acoustic resonator according to claim 6, characterized in that, The cavity is filled with air or a material with a different acoustic impedance than the partition in which it is located.

9. The bulk acoustic resonator according to claim 1, characterized in that, The at least one cavity is located within the resonant region of the piezoelectric layer; Alternatively, the at least one cavity portion is located within the resonant region of the piezoelectric layer, while the remaining portion is located outside the resonant region of the piezoelectric layer; Alternatively, the at least one cavity may be located outside the resonant region of the piezoelectric layer.

Images