Bulk acoustic resonator based on acoustic reflection structure and method of manufacturing the same

Abstract

The application discloses a bulk acoustic resonator based on an acoustic reflection structure and a preparation method thereof. The bulk acoustic resonator comprises a resonant cavity, a first electrode, a piezoelectric layer and a second electrode which are sequentially stacked on the resonant cavity, and an edge portion of at least one of the first electrode, the piezoelectric layer and the second electrode is provided with an acoustic reflection structure, the acoustic reflection structure comprises at least one protruding portion and / or at least one recessed portion provided on the edge portion, the protruding portion protrudes in a first direction, the recessed portion is recessed in a second direction, the first direction is parallel to a film plane of the piezoelectric layer, and the first direction gradually deviates from the direction of the edge portion, and the second direction is opposite to the first direction. The bulk acoustic resonator provided by the embodiment of the application has the acoustic reflection structure with a triangular or arc shape in the edge portion, and can effectively reduce the interference of a parasitic mode in the device.

Description

Technical Field

[0001] This invention relates to a bulk acoustic wave resonator, and more particularly to a bulk acoustic wave resonator based on an acoustic reflection structure and its fabrication method, belonging to the field of semiconductor technology. Background Technology

[0002] Thin-film bulk acoustic wave (BAWR) filters are considered the preferred option for miniaturized high-frequency (≥2GHz) filters due to their lower insertion loss, steeper roll-off, and better out-of-band rejection. They consist of series and parallel BAWRs, with a basic structure consisting of a lower electrode / piezoelectric material / upper electrode sandwich.

[0003] Regular rectangular or square electrodes can introduce parasitic modes between the series resonant frequency (fs) and the parallel resonant frequency (fp), causing impedance abrupt changes in the resonator and further affecting the in-band ripple of filters composed of this type of resonator. A common solution is to use irregular electrode structures, such as irregular quadrilaterals, pentagons, and irregular polygons with more sides, or even ellipses. However, irregular electrode structures result in lower chip area utilization and greater difficulty in layout when connecting chips in series and parallel configurations. Summary of the Invention

[0004] The main objective of this invention is to provide a bulk acoustic resonator based on an acoustic reflection structure and its fabrication method, thereby overcoming the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a bulk acoustic resonator based on an acoustic reflection structure, comprising: a resonant cavity and a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on the resonant cavity. At least one of the first electrode, the piezoelectric layer, and the second electrode has an acoustic reflection structure at its edge. The acoustic reflection structure includes at least one protrusion and / or at least one recess at the edge. The protrusion extends along a first direction, and the recess is recessed along a second direction. The first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the edge. The second direction is opposite to the first direction.

[0007] This invention also provides a method for fabricating the aforementioned bulk acoustic resonator, comprising:

[0008] A first electrode, a piezoelectric layer, and a second electrode are sequentially fabricated on a substrate in a stacked configuration.

[0009] A portion of the edge portion of at least one of the first electrode, the piezoelectric layer, and the second electrode is removed to form at least one protrusion and / or at least one recess, thereby forming an acoustic reflection structure; the protrusion extends along a first direction, the recess is recessed along a second direction, the first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the edge portion, and the second direction is opposite to the first direction.

[0010] A portion of the piezoelectric layer and the second electrode are removed to form a through-hole exposing the first electrode, and a resonant cavity is formed within the substrate.

[0011] Compared with the prior art, the bulk acoustic resonator with an acoustic reflection structure of triangular or arc shape at the edge provided by the embodiments of the present invention can effectively reduce parasitic mode interference in the device. Attached Figure Description

[0012] Figure 1a This is a schematic diagram of a bulk acoustic resonator based on an acoustic reflection structure provided in a typical embodiment of the present invention;

[0013] Figure 1b This is an enlarged structural diagram of structure A in Figure 1;

[0014] Figure 2 This is a schematic diagram of the fabrication process of a bulk acoustic resonator based on an acoustic reflection structure provided in Embodiment 1 of the present invention;

[0015] Figure 3 This is an example of the impedance characteristic curves of a bulk acoustic resonator based on a triangular acoustic reflection structure and a bulk acoustic resonator without an acoustic reflection structure provided in a typical embodiment of the present invention.

[0016] Figure 4 This is an impedance characteristic curve of a bulk acoustic resonator based on a triangular acoustic reflection structure with one row of notches, two rows of notches, or three rows of notches, provided in a typical embodiment of the present invention.

[0017] Figure 5 The impedance characteristic curves of a bulk acoustic resonator based on a rectangular electrode with an acoustic reflection structure and a bulk acoustic resonator based on a rectangular electrode but without an acoustic reflection structure are provided in a typical embodiment of the present invention.

[0018] Figure 6 The impedance characteristic curves of a bulk acoustic resonator based on a square electrode with an acoustic reflection structure and a bulk acoustic resonator based on a square electrode but without an acoustic reflection structure are provided in a typical embodiment of the present invention.

[0019] Figure 7This is an example of an embodiment of the present invention, which provides impedance characteristic curves for a bulk acoustic resonator based on a triangular acoustic reflection structure and an arc-shaped acoustic reflection structure, and a bulk acoustic resonator without an acoustic reflection structure.

[0020] Figure 8 This is a schematic diagram of the fabrication process of a bulk acoustic resonator based on an acoustic reflection structure provided in Embodiment 2 of the present invention;

[0021] Figure 9 This is an example of the impedance characteristic curves of a bulk acoustic resonator based on an electrode with an acoustic reflection structure and a piezoelectric layer with an acoustic reflection structure, and a bulk acoustic resonator without an acoustic reflection structure, provided in a typical embodiment of the present invention.

[0022] Figure 10 This is a schematic diagram of the fabrication process of a bulk acoustic resonator based on an acoustic reflection structure provided in Embodiment 3 of the present invention. Detailed Implementation

[0023] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0024] The inventors of this case have discovered that acoustic reflection structures (also known as acoustic structures) such as polygons such as triangles or arcs such as fan shapes can change the direction of transverse wave propagation in a chip and can effectively suppress the formation of transverse standing waves. By setting such acoustic reflection structures at the edges of regular-shaped bulk acoustic resonators, parasitic mode interference in the device can be reduced, and high-performance BAWR devices can be obtained.

[0025] This invention provides a bulk acoustic resonator based on an acoustic reflection structure, comprising: a resonant cavity and a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on the resonant cavity. At least one of the first electrode, the piezoelectric layer, and the second electrode has an acoustic reflection structure at its edge. The acoustic reflection structure includes at least one protrusion and / or at least one recess at the edge. The protrusion extends along a first direction, and the recess is recessed along a second direction. The first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the edge. The second direction is opposite to the first direction.

[0026] In one specific embodiment, the protrusion and the recess have regular or irregular contour shapes, and the angle of at least one base angle α of the protrusion or the recess is 20-60°, or the angle of at least one base angle α of the circumscribed triangle of the protrusion or the recess is 20-60°.

[0027] In a specific implementation, the shape of the protrusion and the recess can be polygonal or arc-shaped. The polygon includes triangles, and the arc includes sectors. Of course, the polygon can also be quadrilateral, pentagon, etc. The base angle is generally the angle formed by one side of the protrusion or the recess and the edge of the first electrode, the piezoelectric layer, or the second electrode. Alternatively, one of the two sides of the base angle is the side closest to the edge of the first electrode, the piezoelectric layer, or the second electrode.

[0028] In one specific implementation, the side length a of the protrusion or recess is (1-8)λ, where λ is the wavelength of the Lamb wave to be suppressed in the piezoelectric layer.

[0029] In one specific implementation, λ can be 100nm-20μm.

[0030] In one specific embodiment, the acoustic reflection structure includes a plurality of protrusions and / or recesses, which are arranged continuously at the edge of the first electrode, the piezoelectric layer, or the second electrode; or, the plurality of protrusions and / or recesses are spaced apart at the edge of the first electrode, the piezoelectric layer, or the second electrode, and the distance between two adjacent protrusions and / or recesses is (0-5)λ.

[0031] In one specific implementation, the recess is a notch formed at the edge.

[0032] In one specific implementation, the shape of the protrusion or recess can be regular or irregular. For example, the shape of the protrusion or recess includes polygons or arcs, such as triangles and fan shapes. Of course, triangular and arc-shaped protrusions or recesses can also be combined to form a composite acoustic reflection structure. This acoustic reflection structure can be used on regular-shaped bulk acoustic resonators or on irregular-shaped acoustic resonators.

[0033] In one specific implementation, the shapes and characteristic parameters of the multiple protrusions or recesses may be the same or different, and the combination of multiple protrusions or recesses with different shapes and / or characteristic parameters forms a composite acoustic reflection structure.

[0034] In one specific embodiment, the acoustic reflection structure further includes at least one through hole disposed at the edge portion, the through hole penetrating the first electrode, the piezoelectric layer, or the second electrode along the thickness direction, and the through hole having a regular or irregular contour shape.

[0035] In one specific implementation, the angle of at least one base angle α of the through hole is 20-60°, or the angle of at least one base angle α of the circumscribed triangle of the through hole is 20-60°.

[0036] In one specific implementation, the shape of the through hole includes a polygon or an arc. The polygon includes a triangle, and the arc includes a sector. Of course, the polygon can also be a quadrilateral, a pentagon, etc. The base angle is generally the angle formed by one side of the through hole and the edge of the first electrode, the piezoelectric layer, or the second electrode. Alternatively, one of the two sides of the base angle is the side closest to the edge of the first electrode, the piezoelectric layer, or the second electrode.

[0037] In one specific implementation, the side length a of the through hole is (1-8)λ.

[0038] In one specific implementation, the area of ​​the edge portion of the first electrode, the piezoelectric layer, and the second electrode is less than 20% of their total area, and the edge portion is disposed around the main body portion.

[0039] In one specific embodiment, the first electrode and the second electrode are preferably electrodes with regular shapes, but they can also be electrodes with irregular shapes.

[0040] In one specific implementation, both the first electrode and the second electrode can be rectangular electrodes, or they can be electrodes of shapes such as rhombus, circle or ellipse.

[0041] In one specific implementation, the first electrode includes a first electrode layer, the material of which includes any one or more combinations of Mo, Al, Pt, Ru and W, but is not limited thereto.

[0042] In one specific embodiment, the second electrode includes a second electrode layer, the material of which includes any one or more combinations of Mo, Al, Pt, Co, W, Ni, Au, PMN-PT, FeGa, FeGaC, FeNi, FeCoNi, FeCoSiB and FeGaB, but is not limited thereto.

[0043] In one specific implementation, the thickness of the first electrode layer is 50nm-2000nm.

[0044] In one specific implementation, the thickness of the second electrode layer is 50nm-2000nm.

[0045] In one specific implementation, the bulk acoustic wave resonator further includes a temperature control layer, which is stacked between the first electrode and the piezoelectric layer and / or between the second electrode and the piezoelectric layer and / or between two adjacent piezoelectric layers. For example, the bulk acoustic wave resonator structure can be first electrode / temperature control layer / piezoelectric layer / second electrode, first electrode / piezoelectric layer / temperature control layer / second electrode, or first electrode / piezoelectric layer / temperature control layer / piezoelectric layer / second electrode.

[0046] In one specific implementation, the temperature control layer is made of silicon oxide or doped silicon oxide, wherein the doped silicon oxide may be silicon oxide doped with B, C, P or F, etc.

[0047] In one specific implementation, the material of the piezoelectric layer includes any one or a combination of two or more of AlN, ZnO, PZT and LiNbO3, but is not limited thereto.

[0048] In one specific implementation, the thickness of the piezoelectric layer is 50nm-5000nm.

[0049] In one specific embodiment, the bulk acoustic resonator includes: a substrate, wherein the resonant cavity is disposed on one side surface of the substrate or penetrates the substrate along a selected direction.

[0050] In one specific implementation, the substrate may be a silicon substrate or the like.

[0051] In one specific implementation, the first electrode stack is disposed on the seed layer, and the seed layer stack is disposed on the resonant cavity.

[0052] In one specific implementation, the seed layer is made of AlN and has a thickness of 10-100 nm.

[0053] This invention also provides a method for fabricating the aforementioned bulk acoustic resonator, comprising:

[0054] A first electrode, a piezoelectric layer, and a second electrode are sequentially fabricated on a substrate in a stacked configuration.

[0055] A portion of the edge portion of at least one of the first electrode, the piezoelectric layer, and the second electrode is removed to form at least one protrusion and / or at least one recess, thereby forming an acoustic reflection structure; the protrusion extends along a first direction, the recess is recessed along a second direction, the first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the edge portion, and the second direction is opposite to the first direction.

[0056] A portion of the piezoelectric layer and the second electrode are removed to form a through-hole exposing the first electrode, and a resonant cavity is formed within the substrate.

[0057] In one specific embodiment, the preparation method further includes: removing a portion of the edge portion of at least one of the first electrode, the piezoelectric layer, and the second electrode to form at least one through hole, thereby forming an acoustic reflection structure.

[0058] The following will further explain the technical solution, its implementation process and principle. Unless otherwise specified, the equipment and process parameters used in the sputtering, deposition, etching and other processes in the embodiments of the present invention are known to those skilled in the art.

[0059] Please see Figure 1a and Figure 1b A bulk acoustic resonator based on an acoustic reflection structure includes: a substrate and a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on the substrate. At least one of the first electrode, the piezoelectric layer, and the second electrode has an acoustic reflection structure at its edge. The acoustic reflection structure includes a plurality of protrusions and / or a plurality of recesses disposed at the edge. The protrusions extend along a first direction, and the recesses are recessed along a second direction. The first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the edge. The second direction is opposite to the first direction.

[0060] In this embodiment, the edge portions of the first electrode, the piezoelectric layer, and the second electrode are disposed around the main body portion, and the area of ​​the edge portions of the first electrode, the piezoelectric layer, and the second electrode is less than 20% of their total area.

[0061] In this embodiment, a plurality of the protrusions and / or recesses are arranged in a continuous manner at the edge of the first electrode, the piezoelectric layer, or the second electrode; or, a plurality of the protrusions and / or recesses are spaced apart at the edge of the first electrode, the piezoelectric layer, or the second electrode.

[0062] In this embodiment, the recessed portion is a notch formed at the edge portion, wherein, Figure 1a and Figure 1b The notch shown is formed by an inward indentation from the edge of the first electrode, the piezoelectric layer, or the second electrode.

[0063] In this embodiment, the notch can be a regular shape or an irregular shape. For example, the shape of the notch can be a triangle or an arc. The angle of at least one base angle α of the triangular notch is 20-60°, or the angle of at least one base angle α of the circumscribed triangle of the arc notch is 20-60°. The side length a of the notch is (1-8)λ, and the distance b between two adjacent notches is (0-5)λ, where λ is the wavelength of the Lamb wave to be suppressed in the piezoelectric layer.

[0064] In this embodiment, please refer to Figure 4 The acoustic reflection structure further includes at least one through hole disposed at the edge portion, the through hole penetrating the first electrode, the piezoelectric layer or the second electrode along the thickness direction, and the through hole having a regular or irregular contour shape.

[0065] In this embodiment, the shape of the through hole includes a polygon or an arc. The polygon includes a triangle, and the arc includes a sector. The angle of at least one base angle α of the through hole is 20-60°, or the angle of at least one base angle α of the circumscribed triangle of the through hole is 20-60°, and the side length a of the through hole is (1-8)λ.

[0066] In this embodiment, a plurality of through holes are arranged continuously at the edge of the first electrode, the piezoelectric layer, or the second electrode, or a plurality of through holes are spaced apart at the edge of the first electrode, the piezoelectric layer, or the second electrode, and the distance b between two adjacent through holes is (0-5)λ.

[0067] In one embodiment, the substrate has a resonant cavity disposed on one side surface of the substrate or through the substrate, and the first electrode is disposed on the resonant cavity.

[0068] Example 1

[0069] Please see Figure 2 A method for fabricating a bulk acoustic resonator based on an acoustic reflection structure may include the following steps:

[0070] 1) Prepare a high-resistivity Si(100) wafer and clean it;

[0071] 2) A Mo metal layer with a thickness of 200 nm was deposited on the first surface of a high-resistivity Si(100) wafer using magnetron sputtering and other methods, and then patterned to form the first electrode;

[0072] 3) An AlN layer with a thickness of 610 nm was deposited on the first electrode using magnetron sputtering and other methods as a piezoelectric layer, and a Mo metal layer with a thickness of 200 nm was deposited on the piezoelectric layer.

[0073] 4) The metal Mo stacked on the piezoelectric layer is patterned to form a second electrode and an acoustic structure located at the edge of the second electrode; wherein the second electrode can be a rectangular structure, especially a square structure, and the acoustic structure can be a triangular or arc-shaped notch, or a combination of both.

[0074] 5) Patterning is used to form conductive vias that expose the first electrode;

[0075] 6) The second surface of the high-resistivity Si(100) wafer is patterned to form a resonant cavity that penetrates the high-resistivity Si(100) wafer along the thickness direction, thereby completing the fabrication of the bulk acoustic resonator, wherein the first surface and the second surface are arranged back to back.

[0076] 7) The impedance characteristics of the fabricated bulk acoustic resonator were tested and characterized using a network analyzer. The results are shown in Figure 3-. Figure 7 As shown, Figures 3-7 The impedance characteristics of bulk acoustic resonators with different acoustic structures prepared by the preparation method provided in this embodiment are shown respectively. The impedance characteristics are obtained by simulation using finite element simulation software.

[0077] Example 2

[0078] Please see Figure 8 A method for fabricating a bulk acoustic resonator based on an acoustic reflection structure may include the following steps:

[0079] 1) Prepare a high-resistivity Si(100) wafer and clean it;

[0080] 2) A 200 nm thick Mo metal is deposited on the first surface of a high-resistivity Si(100) wafer using magnetron sputtering and other methods, and then patterned to form the first electrode;

[0081] 3) An AlN layer with a thickness of 610 nm was deposited on the first electrode as a piezoelectric layer by means of magnetron sputtering, and a Mo metal layer with a thickness of 200 nm was deposited on the piezoelectric layer;

[0082] 4) The metal Mo stacked on the piezoelectric layer is patterned to form a second electrode and an acoustic structure located at the edge of the second electrode. The acoustic structure located at the edge of the second electrode is deepened to the edge of the piezoelectric layer by patterning and etching techniques.

[0083] 5) Patterning is used to form conductive vias that expose the first electrode;

[0084] 6) The second surface of the high-resistivity Si(100) wafer is patterned to form a resonant cavity that penetrates the high-resistivity Si(100) wafer along the thickness direction, thereby completing the fabrication of the bulk acoustic resonator, wherein the first surface and the second surface are arranged back to back.

[0085] 7) The impedance characteristics of the prepared bulk acoustic resonator were tested and characterized using a network analyzer, and the results were basically the same as those in Example 1.

[0086] Example 3

[0087] A method for fabricating a bulk acoustic resonator based on an acoustic reflection structure may include the following steps:

[0088] 1) Prepare a high-resistivity Si(100) wafer and clean it;

[0089] 2) A 200 nm thick Mo metal is deposited on the first surface of a high-resistivity Si(100) wafer using magnetron sputtering and other methods, and then patterned to form the first electrode;

[0090] 3) A 640 nm thick ZnO layer was deposited on the first electrode as a piezoelectric layer using magnetron sputtering and other methods, and a 200 nm thick Mo metal layer was deposited on the piezoelectric layer.

[0091] 4) The metal Mo stacked on the piezoelectric layer is patterned to form a second electrode and an acoustic structure located at the edge of the second electrode. Patterning and etching techniques are used to deepen the acoustic structure located at the edge of the second electrode to the edge of the piezoelectric layer.

[0092] 5) Patterning is used to form conductive vias that expose the first electrode;

[0093] 6) The second surface of the high-resistivity Si(100) wafer is patterned to form a resonant cavity that penetrates the high-resistivity Si(100) wafer along the thickness direction, thereby completing the fabrication of the bulk acoustic resonator, wherein the first surface and the second surface are arranged back to back.

[0094] 7) The impedance characteristics of the fabricated bulk acoustic resonator were tested and characterized using a network analyzer, and the results are as follows: Figure 9 As shown.

[0095] Example 4

[0096] Please see Figure 10 A method for fabricating a bulk acoustic resonator based on an acoustic reflection structure may include the following steps:

[0097] 1) Prepare a high-resistivity Si(100) wafer and clean it. Then, pattern the first surface of the high-resistivity Si(100) wafer and etch a cavity on the first surface of the high-resistivity Si(100) wafer.

[0098] 2) Fill the cavity with silicon dioxide (PSG) containing phosphorus, and use chemical mechanical polishing (CMP) to planarize the surface of the high-resistivity Si(100) wafer filled with P-containing silicon dioxide and remove the PSG outside the cavity; then use magnetron sputtering or other methods to deposit an AlN layer with a thickness of 10-50 nm as a buffer layer on the first surface of the high-resistivity Si(100) wafer, deposit a Mo metal layer with a thickness of 200 nm on the buffer layer, and pattern the Mo metal to form the first electrode;

[0099] 3) A 1000 nm thick PZT layer is deposited on the first electrode as a piezoelectric layer using magnetron sputtering or other methods, and a 200 nm thick Mo layer is deposited on the piezoelectric layer.

[0100] 4) The metal Mo stacked on the piezoelectric layer is patterned to form a second electrode and an acoustic structure located at the edge of the second electrode. The second electrode can be a rectangular structure, especially a square structure. The acoustic structure can be a triangular or arc-shaped notch, or a combination of both.

[0101] 5) Patterning is used to form conductive vias that expose the first electrode;

[0102] 6) Etch to form a release via corresponding to the cavity, and use liquid or gaseous HF to remove PSG in the cavity, thereby forming a resonant cavity and completing the fabrication of the bulk acoustic resonator;

[0103] 7) The impedance characteristics of the prepared bulk acoustic resonator were tested and characterized using a network analyzer, and the results were basically the same as those in Example 1.

[0104] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A bulk acoustic resonator based on an acoustic reflection structure, characterized in that, include: The resonant cavity includes a first electrode, a piezoelectric layer, and a second electrode stacked sequentially on the resonant cavity. At least one of the first electrode, the piezoelectric layer, and the second electrode has an acoustic reflection structure at its edge. The acoustic reflection structure includes at least one protrusion and / or at least one recess at the edge. The protrusion extends along a first direction, and the recess is recessed along a second direction. The angle α of at least one base angle of the protrusion or the recess is 20-60°, or the angle α of at least one base angle of the circumscribed triangle of the protrusion or the recess is 20-60°. The first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the edge. The second direction is opposite to the first direction.

2. The bulk acoustic resonator according to claim 1, characterized in that: The protrusions or recesses have regular or irregular outline shapes.

3. The bulk acoustic resonator according to claim 2, characterized in that: The protrusions and recesses are in the shape of polygons or arcs, the polygons including triangles and the arcs including sectors.

4. The bulk acoustic resonator according to claim 2, characterized in that: The side length a of the protrusion and the concave part is (1-8)λ, where λ is the wavelength of the Lamb wave to be suppressed in the piezoelectric layer, λ=100nm-20μm.

5. The bulk acoustic resonator according to claim 1, 2, 3, or 4, characterized in that: The acoustic reflection structure includes multiple protrusions and / or recesses, which are arranged continuously at the edge of the first electrode, the piezoelectric layer, or the second electrode. Alternatively, the multiple protrusions and / or recesses are spaced apart at the edge of the first electrode, the piezoelectric layer, or the second electrode, and the distance between two adjacent protrusions and / or recesses is (0-5)λ.

6. The bulk acoustic resonator according to claim 5, characterized in that: The recessed portion is a notch formed at the edge.

7. The bulk acoustic resonator according to claim 1, characterized in that: The acoustic reflection structure further includes at least one through hole disposed at the edge portion, the through hole penetrating the first electrode, the piezoelectric layer, or the second electrode along the thickness direction, and the through hole having a regular or irregular contour shape.

8. The bulk acoustic resonator according to claim 7, characterized in that: The angle of at least one base angle α of the through hole is 20-60°, or the angle of at least one base angle α of the circumscribed triangle of the through hole is 20-60°.

9. The bulk acoustic resonator according to claim 7, characterized in that: The shape of the through hole includes a polygon or an arc, the polygon including a triangle, and the arc including a sector.

10. The bulk acoustic resonator according to claim 7, characterized in that: The side length a of the through hole is (1-8)λ.

11. The bulk acoustic resonator according to claim 1, characterized in that: The area of ​​the edge portion of the first electrode, the piezoelectric layer, and the second electrode is less than 20% of their total area, and the edge portion is arranged around the main body portion.

12. The bulk acoustic resonator according to claim 1, characterized in that: Both the first electrode and the second electrode are electrodes with regular shapes.

13. The bulk acoustic resonator according to claim 12, characterized in that: The first electrode includes a first electrode layer, and the material of the first electrode layer includes any one or a combination of two or more of Mo, Al, Pt, Ru and W.

14. The bulk acoustic resonator according to claim 12, characterized in that: The second electrode includes a second electrode layer, the material of which includes any one or a combination of two or more of Mo, Al, Pt, Co, W, Ni, Au, PMN-PT, FeGa, FeGaC, FeNi, FeCoNi, FeCoSiB and FeGaB.

15. The bulk acoustic resonator according to claim 13, characterized in that: The thickness of the first electrode layer is 50nm-2000nm.

16. The bulk acoustic resonator according to claim 14, characterized in that: The thickness of the second electrode layer is 50nm-2000nm.

17. The bulk acoustic resonator according to claim 1, characterized in that: The bulk acoustic resonator further includes a temperature control layer, which is stacked between the first electrode and the piezoelectric layer and / or between the second electrode and the piezoelectric layer and / or between two adjacent piezoelectric layers.

18. The bulk acoustic resonator according to claim 17, characterized in that: The temperature control layer is made of silicon oxide or doped silicon oxide.

19. The bulk acoustic resonator according to claim 1, characterized in that: The piezoelectric layer is made of any one or a combination of two or more of AlN, ZnO, PZT and LiNbO3.

20. The bulk acoustic resonator according to claim 19, characterized in that: The thickness of the piezoelectric layer is 50nm-5000nm.

21. The bulk acoustic resonator according to claim 1, characterized in that, include: The substrate, wherein the resonant cavity is disposed on one side surface of the substrate or penetrates the substrate in a selected direction.

22. The bulk acoustic resonator according to claim 21, characterized in that: The first electrode stack is disposed on the seed layer, and the seed layer stack is disposed on the resonant cavity.

23. The bulk acoustic resonator according to claim 22, characterized in that: The seed layer is made of AlN and has a thickness of 10-100 nm.

24. A method for fabricating a bulk acoustic resonator, characterized in that, The fabrication method for a bulk acoustic resonator as described in any one of claims 1-23 comprises: A first electrode, a piezoelectric layer, and a second electrode are sequentially fabricated on a substrate in a stacked configuration. A portion of the edge portion of at least one of the first electrode, the piezoelectric layer, and the second electrode is removed to form at least one protrusion and / or at least one recess, thereby forming an acoustic reflection structure; the protrusion extends along a first direction, the recess is recessed along a second direction, the first direction is parallel to the film plane of the piezoelectric layer and gradually moves away from the direction of the edge portion, and the second direction is opposite to the first direction; A portion of the piezoelectric layer and the second electrode are removed to form a through-hole exposing the first electrode, and a resonant cavity is formed within the substrate.

25. The preparation method according to claim 24, characterized in that, Also includes: A portion of the edge portion of at least one of the first electrode, the piezoelectric layer, and the second electrode is removed to form at least one through-hole, thereby forming an acoustic reflection structure.

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