A film bulk acoustic resonator and a method of manufacturing the same

Abstract

This invention discloses a thin-film bulk acoustic wave resonator and its fabrication method. The thin-film bulk acoustic wave resonator includes: a first support layer located in a second edge region comprising a first support portion and a first suspension portion; the first suspension portion comprising a first recess, a first protrusion, and a second recess; the first support layer located in the first edge region comprising a second protrusion; the first support portion contacting a substrate; and the first recess, first protrusion, second recess, and second protrusion not contacting the substrate; and a cavity being formed on a first surface of the substrate adjacent to the first support layer. Alternatively, the first support layer located in the second edge region comprising a second support portion in contact with the substrate; the first support layer further comprising a second suspension portion located between the second support portion and the first edge region; the second suspension portion further comprising at least one third protrusion; and the first edge region comprising a fourth protrusion. This invention can improve the problem of transverse wave energy leakage and increase the Q value of the resonator.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, and in particular to a thin-film bulk acoustic resonator and its fabrication method. Background Technology

[0002] With the rapid development of 5G communication technology, the application and demand for radio frequency (RF) filters are constantly upgrading. RF filters are operating at increasingly higher frequencies, with wider bandwidths and lower insertion losses, placing increasingly higher demands on the overall performance of RF filters. To meet the performance requirements of filters at high frequencies, thin-film bulk acoustic resonators (FBARs) are currently the mainstream research area. Figure 1 This is a schematic diagram of a traditional thin-film bulk acoustic wave (FBAR) resonator. The FBAR resonator is connected to the substrate 10 through the bottom electrode 30 and the piezoelectric layer 40, supporting the entire resonant region. The FBAR resonator has a sandwich structure of top electrode 50-piezoelectric layer 40-bottom electrode 30. However, this design has limitations. Existing FBARs generally have lateral parasitic clutter and leakage, which affects the performance of the thin-film bulk acoustic wave resonator. Summary of the Invention

[0003] This invention provides a thin-film bulk acoustic resonator and its fabrication method, which can effectively improve the problem of leakage of transverse wave energy propagation and increase the Q value of the resonator.

[0004] According to one aspect of the present invention, a thin-film bulk acoustic resonator is provided, comprising:

[0005] A substrate, a first support layer, a bottom electrode, a piezoelectric layer, and a top electrode are stacked sequentially.

[0006] The resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, with the second edge region surrounding the first edge region; a top electrode is disposed in the resonant region, and a piezoelectric layer and a bottom electrode are disposed in the first edge region and the resonant region; a first support layer is disposed in the first edge region and the second edge region;

[0007] The portion of the first support layer located in the second edge region includes a first support portion and a first suspension portion. The first suspension portion includes a first recess, a first protrusion, and a second recess. The portion of the first support layer located in the first edge region includes a second protrusion. The first support portion is in contact with the substrate, while the first recess, the first protrusion, the second recess, and the second protrusion are not in contact with the substrate. In the direction from the second edge region to the resonant region, the first support portion, the first recess, the first protrusion, and the second recess are sequentially arranged. The first surface of the substrate adjacent to the first support layer has a cavity. The resonant region, the first edge region, and the second edge region (excluding the first support portion) are located within the cavity in their vertical projection on the substrate. The distance between the surfaces of the first recess and the second recess adjacent to the substrate and the second surface of the substrate away from the bottom electrode is less than the distance between the surfaces of the first protrusion and the second protrusion adjacent to the substrate and the second surface of the substrate. The bottom electrode is in contact with the surface of the second protrusion away from the substrate.

[0008] Alternatively, the first surface of the substrate adjacent to the first support layer is planar, the portion of the first support layer located in the second edge region includes a second support portion, the second support portion is in contact with the substrate, the first support layer also includes a second suspension portion located between the second support portion and the first edge region, the second suspension portion also includes at least one third protrusion, the first edge region includes a fourth protrusion, the distance between the surface of the third protrusion and the fourth protrusion adjacent to the substrate and the first surface of the substrate is greater than the distance between the surface of the second suspension portion adjacent to the substrate and the first surface of the substrate in other regions, the bottom electrode is in contact with the surface of the fourth protrusion away from the substrate, and the second suspension portion of the first support layer is not in contact with the first surface of the substrate.

[0009] According to another aspect of the present invention, a method for fabricating a thin-film bulk acoustic resonator is provided, comprising:

[0010] A substrate is provided; the resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region;

[0011] A cavity is formed on the substrate;

[0012] A first sacrificial layer is disposed in the cavity, and a first groove and a second groove are formed on the first sacrificial layer; wherein, the first groove and the second groove are located in the second edge region, and the first groove is disposed on the side of the second groove away from the resonant region, and the depth of the first groove and the second groove is less than the thickness of the first sacrificial layer;

[0013] A first support layer is formed on a first sacrificial layer; the first support layer is disposed in a first edge region and a second edge region; wherein, the portion of the first support layer located in the second edge region includes a first support portion and a first suspension portion, the first suspension portion includes a first recessed portion, a first protrusion portion and a second recessed portion, the portion of the first support layer located in the first edge region includes a second protrusion portion, the first recessed portion is located in a first groove, the second recessed portion is located in a second groove, the first support portion is in contact with the substrate, and the first recessed portion, the first protrusion portion, the second recessed portion and the second protrusion portion are not in contact with the substrate. In the direction from the second edge region to the resonant region, the first support portion, the first recessed portion, the first protrusion portion and the second recessed portion are sequentially disposed; a second sacrificial layer is formed on the first support layer; wherein, the second sacrificial layer covers the first sacrificial layer not covered by the first support layer.

[0014] A bottom electrode, a piezoelectric layer, and a top electrode are sequentially formed on the second sacrificial layer. The top electrode is disposed in the resonant region, and the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region, respectively. The bottom electrode is in contact with the surface of the second protrusion away from the substrate. The distance between the surface of the first recess and the second recess adjacent to the substrate and the second surface of the substrate away from the bottom electrode is less than the distance between the surface of the first protrusion and the second protrusion adjacent to the substrate and the second surface of the substrate.

[0015] Remove the first and second sacrificial layers.

[0016] According to another aspect of the present invention, a method for fabricating a thin-film bulk acoustic resonator is provided, comprising:

[0017] A substrate is provided; the resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region;

[0018] A third sacrificial layer is formed on the first surface of the substrate, and a third groove, a fourth groove and a fifth groove are formed on the third sacrificial layer; wherein, the third groove, the fourth groove and the fifth groove are located in the second edge region, and the third groove and the fifth groove are located on the side of the fourth groove away from the resonant region, the vertical projection of the fifth groove on the substrate covers the vertical projection of the third groove on the substrate, the third groove penetrates the third sacrificial layer, and the depth of the fourth groove and the fifth groove is less than the thickness of the sacrificial layer.

[0019] A first support layer is formed on the surface of the third sacrificial layer; the first support layer is disposed in a first edge region and a second edge region; wherein, the portion of the first support layer located in the second edge region includes a second support portion, the second support portion is located in a third groove, the second support portion is in contact with the substrate, the first support layer also includes a second suspension portion located between the second support portion and the first edge region, the second suspension portion also includes at least one third protrusion, the first edge region includes a fourth protrusion, the third protrusion is located between a fifth groove and a fourth groove, the distance between the surface of the third protrusion and the fourth protrusion adjacent to the substrate and the first surface of the substrate is greater than the distance between the surface of the second suspension portion adjacent to the substrate and the first surface of the substrate in other regions, and the second suspension portion of the first support layer is not in contact with the first surface of the substrate;

[0020] A fourth sacrificial layer is formed in the first support layer; wherein the fourth sacrificial layer covers the third sacrificial layer that is not covered by the first support layer;

[0021] A bottom electrode, a piezoelectric layer, and a top electrode are sequentially formed on the fourth sacrificial layer; the top electrode is disposed in the resonant region, the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region, and the bottom electrode is in contact with the surface of the fourth protrusion away from the substrate.

[0022] Remove the third and fourth sacrifice layers.

[0023] The thin-film bulk acoustic resonator provided by the technical solution of the present invention provides a first support layer in the second edge region, and a first recess, a first protrusion, and a second recess in the first support layer. The first recess, the first protrusion, and the second recess in the first support layer can reflect transverse sound waves propagating in the plane of the resonator multiple times. Alternatively, the first support layer can be provided with a second support, a third protrusion, and a fourth protrusion. The second support, the third protrusion, and the fourth protrusion can also reflect transverse sound waves propagating in the plane of the resonator multiple times. This effectively reduces the problem of vibration energy leakage to the substrate in traditional thin-film bulk acoustic resonators and greatly improves the Q value of the resonator.

[0024] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is a schematic diagram of a traditional thin-film bulk acoustic resonator.

[0027] Figure 2 This is a schematic diagram of the structure of a thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0029] Figure 4 This is a vibration displacement diagram of a traditional thin-film bulk acoustic resonator;

[0030] Figure 5 yes Figure 2 Vibration displacement diagram of a thin-film bulk acoustic resonator;

[0031] Figure 6 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0032] Figure 7 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0033] Figure 8 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0034] Figure 9 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0035] Figure 10 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0036] Figure 11 This is a schematic diagram of the structure of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention;

[0037] Figure 12 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention;

[0038] Figure 13 This is a schematic diagram of the cavity structure of a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0039] Figure 14 This is a schematic diagram of the fabrication process of a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0040] Figure 15 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0041] Figure 16 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0042] Figure 17 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0043] Figure 18 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0044] Figure 19 This is a flowchart of another method for fabricating a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0045] Figure 20 This is a schematic diagram of the sacrificial layer structure of a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0046] Figure 21 This is a flowchart of another method for fabricating a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0047] Figure 22 This is a flowchart of another method for fabricating a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0048] Figure 23 This is a flowchart of another method for fabricating a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention;

[0049] Figure 24 This is a flowchart of another method for fabricating a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0052] Example 1

[0053] This invention provides a thin-film bulk acoustic resonator. Figure 2 This is a schematic diagram of the structure of a thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 2 The thin-film bulk acoustic resonator includes a substrate 10, a first support layer 20, a bottom electrode 30, a piezoelectric layer 40, and a top electrode 50, which are stacked sequentially.

[0054] The resonator includes a resonant region 60 and a first edge region 70 and a second edge region 80 surrounding the resonant region 60, with the second edge region 80 surrounding the first edge region 70; a top electrode 50 is disposed in the resonant region 60, and a piezoelectric layer 40 and a bottom electrode 30 are disposed in the first edge region 70 and the resonant region 60; a first support layer 20 is disposed at least in the first edge region 70 and the second edge region 80.

[0055] The portion of the first support layer 20 located in the second edge region 80 includes a first support portion 21 and a first suspension portion. The first suspension portion includes a first recessed portion 24, a first protrusion 22, and a second recessed portion 25. The portion of the first support layer 20 located in the first edge region 70 includes a second protrusion 23. The first support portion 21 is in contact with the substrate 10, while the first recessed portion 24, the first protrusion 22, the second recessed portion 25, and the second protrusion 23 are not in contact with the substrate. In the direction from the second edge region 80 to the resonant region 60, the first support portion 21, the first recessed portion 24, the first protrusion 22, and the second protrusion 23 are... The recesses 25 are arranged sequentially; the first surface of the substrate 10 adjacent to the first support layer 20 has a cavity, and the resonant region 60, the first edge region 70 and the second edge region 80 other than the first support 21 are located in the cavity in the vertical projection of the substrate 10. The distance between the surface of the first recess 24 and the second recess 25 adjacent to the substrate 10 and the second surface of the substrate 10 away from the bottom electrode 30 is less than the distance between the surface of the first protrusion 22 and the second protrusion 23 adjacent to the substrate 10 and the second surface of the substrate 10. The bottom electrode 30 is in contact with the surface of the second protrusion 23 away from the substrate 10.

[0056] or, Figure 3 This is a schematic diagram of the structure of a thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 3 The first surface of the substrate 10 adjacent to the first support layer 20 is planar. The portion of the first support layer 20 located in the second edge region 80 includes a second support portion 26, which is in contact with the substrate 10. The first support layer 20 also includes a second suspension portion located between the second support portion 26 and the first edge region 70. The second suspension portion also includes at least one third protrusion 27. The first edge region 70 includes a fourth protrusion 28. The distance between the surfaces of the third protrusion 27 and the fourth protrusion 28 adjacent to the substrate 10 and the first surface of the substrate 10 is greater than the distance between the surfaces of the other regions of the second suspension portion adjacent to the substrate 10 and the first surface of the substrate 10. The bottom electrode 30 is in contact with the surface of the fourth protrusion 28 away from the substrate 10. The second suspension portion of the first support layer 20 is not in contact with the first surface of the substrate 10.

[0057] Specifically, Figure 3 The thin-film bulk acoustic resonator uses a new process to form a cavity, which effectively avoids the formation of stress concentration areas at the edges of traditional cavities, thus preventing a decrease in the overall stability of the device and greatly improving the reliability of the device.

[0058] The substrate 10 can be made of glass, alumina (Al2O3) or high-resistivity silicon to prevent electrical leakage or interference of the bottom electrode 30. The bottom electrode 30 and the top electrode 50 can be made of metal, for example molybdenum. The first support layer 20 can isolate the resonant region 60 formed by the sandwich structure of top electrode 50-piezoelectric layer 40-bottom electrode 30 from the substrate 10 to form a suspension structure.

[0059] The working principle of the thin-film bulk acoustic resonator is as follows: when an alternating voltage is applied to the bottom electrode 30 and the top electrode 50 of the resonator, the piezoelectric layer 40 will generate an inverse piezoelectric effect. During this process, the piezoelectric layer 40 will contract and expand with the change of the alternating electric field. This periodic deformation forms a periodic vibration, which in turn excites a bulk acoustic wave. When the frequency of the excited bulk acoustic wave is the same as the resonant frequency of the resonant region 60 determined by the total thickness of the bottom electrode 30, the piezoelectric layer 40 and the top electrode 50, resonance will be formed. Figure 4 This is a vibration displacement diagram of a traditional thin-film bulk acoustic resonator, for reference. Figure 4 The horizontal axis represents position, and the vertical axis represents the magnitude of displacement. Figure 4The value represents the magnitude of the vibration displacement of the resonator at different positions. For example, the leftmost position of the resonator is set to 0 μm, and the horizontal axis is 50 μm, which represents the position 50 μm away from the leftmost position of the resonator. At the resonant frequency of 2.4 GHz, it can be seen that the traditional thin-film bulk acoustic resonator has obvious energy leakage at the substrate of the black circle, causing the substrate to produce obvious vibration displacement. Figure 5 yes Figure 2 Vibration displacement diagram of a thin-film bulk acoustic resonator, reference Figure 5 As can be seen, no significant energy leakage was observed at the substrate area marked with a black circle in the embodiment of this invention. Compared to the traditional thin-film bulk acoustic resonator structure, this indicates that the structure of the thin-film bulk acoustic resonator in this embodiment can reflect transverse acoustic waves propagating along the resonator plane multiple times, effectively reducing transverse wave energy leakage and significantly improving the resonator's Q value. The Q value is an important indicator for evaluating resonator performance. Traditional FBAR resonators are affected by transverse parasitic clutter, which interferes with the resonator's electrical characteristics, leading to a decrease in the FBAR resonator's Q value and significantly impacting the quality of high-frequency FBAR resonators.

[0060] The thin-film bulk acoustic resonator provided by the technical solution of the present invention provides a first support layer 20 in the second edge region 80, and a first recess 24, a first protrusion 22, and a second recess 25 in the first support layer 20. The first recess 24, the first protrusion 22, and the second recess 25 in the first support layer 20 can reflect transverse sound waves propagating in the plane of the resonator multiple times. Alternatively, a second support portion 26, a third protrusion 27, and a fourth protrusion 28 can be provided in the first support layer 20, and the second support portion 26, the third protrusion 27, and the fourth protrusion 28 can also reflect transverse sound waves propagating in the plane of the resonator multiple times. This effectively reduces the problem of vibration energy leakage to the substrate 10 in traditional thin-film bulk acoustic resonators and greatly improves the Q value of the resonator.

[0061] Optional, see reference Figure 2 The first recess 24 and the second recess 25 are equidistant from the surfaces of the substrate 10 and the second surface of the substrate 10; the first protrusion 22, the second protrusion 23, and the first support 21 are equidistant from the surfaces of the substrate 10 and the second surface of the substrate 10; Reference Figure 3 The third protrusion 27 and the fourth protrusion 28 are at the same distance from the first surface of the substrate 10.

[0062] Wherein, the distance between the surface of the first recess 24 and the second recess 25 adjacent to the substrate and the second surface of the substrate 10 is S1, the distance between the surface of the second protrusion 23 and the first support 21 adjacent to the substrate and the second surface of the substrate 10 is S2, and the distance between the third protrusion 27 and the fourth protrusion 28 and the first surface of the substrate 10 is S3; in the formation process of the first support layer 20, a first sacrificial layer needs to be provided on the substrate 10, and the first recess 24 and the second recess 25 are formed in the first groove and the second groove by etching a first groove and a second groove of the same depth on the first sacrificial layer.

[0063] The distances between the surfaces of the first recessed portion 24 and the second recessed portion 25 adjacent to the substrate 10 and the second surface of the substrate 10, the distances between the surfaces of the first protrusion 22, the second protrusion 23 and the first support portion 21 adjacent to the substrate 10 and the second surface of the substrate 10 are all determined by the size of the first sacrificial layer. The distances between the first recessed portion 24 and the second recessed portion 25 and the second surface of the substrate 10 are the same. The distances between the first protrusion 22, the second protrusion 23 and the first support portion 21 and the second surface of the substrate 10 are the same. The distances between the third protrusion 27 and the fourth protrusion 28 and the first surface of the substrate 10 are the same, which makes the fabrication process of the first sacrificial layer relatively simple.

[0064] Optional, Figure 6 This is a schematic diagram of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 6 The first support layer 20 is also disposed in part of the resonant region 60; the second protrusion 23 extends into the resonant region; Figure 7 This is a schematic diagram of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 7 The fourth protrusion 28 extends to the resonant region 60.

[0065] The first support layer 20 can be disposed in a region of no more than 3 μm within the first edge region 70, the second edge region 80, and the resonant region 60. The second protrusion 23 and the fourth protrusion 28 are disposed in a region of no more than 3 μm within the first edge region 70, the second edge region 80, and the resonant region 60. This arrangement can increase the contact area between the first support layer and the bottom electrode and enhance the support performance without affecting the performance of the thin-film bulk acoustic resonator.

[0066] Optional, Figure 8 This is a schematic diagram of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 8 A second support layer 91 is also included between the first recess 24 and the substrate 10; Figure 9 This is a schematic diagram of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 9The first support layer 20 also includes a third support portion located on the side of the second support portion 26 away from the resonant region 60, and a third support layer 92 is disposed between the third support portion and the substrate 10.

[0067] For details, please refer to Figure 8 A first sacrificial layer can be set in the cavity, and a first support layer 20, a bottom electrode 30, a piezoelectric layer 40 and a top electrode 50 can be formed on the first sacrificial layer. Then the first sacrificial layer is removed. Since the lateral dimension of the device is large enough, the first sacrificial layer between the first recess 24 and the substrate 10 can be left unremoved by controlling the etching time. This part of the first sacrificial layer is the second support layer 91.

[0068] refer to Figure 9 A third sacrificial layer can be formed on the first surface of the substrate 10, and a first support layer 20, a bottom electrode 30, a piezoelectric layer 40 and a top electrode 50 can be formed on the third sacrificial layer. Then the third sacrificial layer can be removed. Alternatively, the third sacrificial layer between the third support portion and the substrate 10 can be left unremoved. This portion of the third sacrificial layer is the third support layer 92, which can increase the support strength.

[0069] Optional, see reference Figure 8 The thickness of the first support layer 20 is 0.2-0.8 μm; the distance between the surface of the first protrusion 22 and the second protrusion 23 adjacent to the substrate 10 and the bottom surface of the cavity is 2-3 μm; the depth of the first recess 24 and the second recess 25 is 0.6-1.5 μm; Reference Figure 9 The distance between the surface of the third protrusion 27 and the fourth protrusion 28 adjacent to the first surface of the substrate 10 is 2-3 μm; the depth of the third protrusion 27 is 0.6-1.5 μm.

[0070] Among them, reference Figure 8The distance between the first protrusion 22 and the second protrusion 23 and the bottom surface of the cavity is S4, where S4 is 2-3 μm. The depth of the first recess 24 and the second recess 25 is S5, where S5 is 0.6-1.5 μm. The width of the first recess 24 and the second recess 25 along the direction from the resonant region 60 to the second edge region 80 is S6, where S4, S5, and S6 are all determined by the size of the first sacrificial layer. A first sacrificial layer can be disposed on the substrate 10, and a first support layer 20 is formed on the first sacrificial layer. The thickness of the first sacrificial layer is the same as S4, which is 2-3 μm. A first groove and a second groove are etched on the first sacrificial layer. The first recess 24 and the second recess 25 are formed in the first groove and the second groove, respectively. The depth of the first groove and the second groove is the same as the depth S5 of the first recess 24 and the second recess 25, which is 0.6-1.5 μm. The width of the first groove and the second groove is 10-15 μm. The first support layer adopts the above dimensions, which ensures that the portion of the first support layer located in the second edge region can better reflect transverse sound waves, and the manufacturing process is relatively simple.

[0071] refer to Figure 9 The distance between the third protrusion 27 and the fourth protrusion 28 and the first surface of the substrate 10 is S3, the depth of the third protrusion 27 is S7, the distance between adjacent edges of the third protrusion 27 and the fourth protrusion 28 is S8, and the width of the second support portion 26 is S9 along the direction from the resonant region 60 to the second edge region 80. S3, S7, S8 and S9 are all determined by the size of the third sacrificial layer. A third sacrificial layer can be formed on the substrate 10, and a first support layer 20 is formed on the third sacrificial layer. A third, fourth, and fifth groove can be formed on the third sacrificial layer. The distance between the third protrusion 27 and the fourth protrusion 28 and the first surface of the substrate 10 is the same, 2-3 μm. The depth of the fourth and fifth grooves is the same as the depth of the third protrusion 27, 0.6-1.5 μm. The width of the fourth groove is 5-10 μm. Along the direction from the resonant region 60 to the second edge region 80, the width of the third groove is 5-10 μm, and the width of the second support 26 is smaller than the width of the third groove. By setting the first support layer with the above dimensions, it is ensured that the portion of the first support layer located in the second edge region can reflect transverse acoustic waves well, and the fabrication process is relatively simple.

[0072] Optional, Figure 10 This is a schematic diagram of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 10 The first protrusion 22 is provided with a first release hole 291, which penetrates the first support layer 20; Figure 9 This is a schematic diagram of another thin-film bulk acoustic resonator provided in Embodiment 1 of the present invention, for reference. Figure 9The third protrusion 27 is provided with a second release hole 292, which penetrates the first support layer 20; the diameter of the first release hole 291 and the second release hole 292 is 10μm.

[0073] In the process of forming the resonator structure, a sacrificial layer needs to be provided on the first surface of the substrate 10, and a first support layer 20, a bottom electrode 30, a piezoelectric layer 40 and a top electrode 50 are formed on the sacrificial layer. The sacrificial layer can be removed by etching the first release hole 291 formed by the first support layer 20, or by etching the second release hole 292 formed by the third protrusion 27. After removing the sacrificial layer, a cavity can be formed between the substrate 10 and the first support layer 20.

[0074] Optionally, the piezoelectric layer is made of at least one of polycrystalline or single-crystal materials such as AlN, AlScN, LiNbO3, and LiTaO3, as well as ferroelectric single-crystal materials; the first support layer is made of polycrystalline silicon or silicon nitride.

[0075] Among them, polycrystalline or single-crystal materials such as AlN, AlScN, LiNbO3, and LiTaO3 have good piezoelectric properties and mature processes. To address the issue that the electromechanical coupling coefficient of traditional piezoelectric layer materials cannot meet the requirements for a large bandwidth, piezoelectric layers can also be made of ferroelectric single crystals with high piezoelectric coefficients. For example, a solid solution of an indium-doped (In) composite perovskite structure (PMN-PT single crystal) can be used. The first support layer is made of polycrystalline silicon or silicon nitride, which can support the thin-film bulk acoustic resonator structure on the substrate. Electrical signals can be transmitted using the first support layer or the bottom electrode.

[0076] Example 2

[0077] Based on the above embodiments, this invention provides a method for fabricating a thin-film bulk acoustic resonator. Figure 12 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention, for reference. Figure 12 The method includes:

[0078] Step 110: Provide a substrate; the resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region.

[0079] The substrate material can be glass, alumina (Al2O3), or high-resistivity silicon.

[0080] Step 120: Form a cavity on the substrate.

[0081] in, Figure 13 This is a schematic diagram of the cavity structure of a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention; see reference. Figure 13The substrate 10 can be patterned by etching to form a cavity 11 with a depth of 2-3 μm.

[0082] Step 130: A first sacrificial layer is provided in the cavity, and a first groove and a second groove are formed on the first sacrificial layer; wherein the first groove and the second groove are located in the second edge region, and the first groove is provided on the side of the second groove away from the resonant region, and the depth of the first groove and the second groove is less than the thickness of the first sacrificial layer.

[0083] in, Figure 14 This is a schematic diagram of the fabrication process of a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention, for reference. Figure 14 A first sacrificial layer 12 is formed in the cavity by a deposition process. For example, silicon dioxide can be deposited, and then chemical mechanical polishing (CMP) is performed on the entire wafer surface to retain only the first sacrificial layer 12 in the cavity, and the upper surface of the first sacrificial layer 12 in the cavity is flush with the upper surface of the substrate 10. Figure 15 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention, for reference. Figure 15 The first sacrificial layer 12 in the cavity is patterned by etching to form the first groove 13 and the second groove 14.

[0084] Step 140: Form a first support layer on the first sacrificial layer; the first support layer is disposed in a first edge region and a second edge region; wherein, the portion of the first support layer located in the second edge region includes a first support portion and a first suspension portion, the first suspension portion includes a first recessed portion, a first protrusion, and a second recessed portion, the portion of the first support layer located in the first edge region includes a second protrusion, the first recessed portion is located in a first groove, the second recessed portion is located in a second groove, the first support portion is in contact with the substrate, and the first recessed portion, the first protrusion, the second recessed portion, and the second protrusion are not in contact with the substrate. In the direction from the second edge region to the resonant region, the first support portion, the first recessed portion, the first protrusion, and the second recessed portion are sequentially disposed. Figure 16 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention, for reference. Figure 16 A support layer is deposited on the surface of the first sacrificial layer 12. For example, the support layer 20 may be polysilicon. The support layer deposited on the surface of the first sacrificial layer 12 is patterned and etched to remove part or all of the support layer in the resonant region, thereby forming the first support layer 20.

[0085] Step 150: Form a second sacrificial layer in the first support layer; wherein the second sacrificial layer covers the first sacrificial layer not covered by the first support layer.

[0086] in, Figure 17 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention, for reference. Figure 17 A second sacrificial layer 15 is deposited on the first support layer 20, and the thickness of the second sacrificial layer 15 is the same as the thickness of the first support layer 20. The second sacrificial layer 15 is patterned and etched to remove the second sacrificial layer 15 covering the first support layer 20. Then, the second sacrificial layer 15 is CMP polished to make the upper surface of the second sacrificial layer 15 flush with the upper surface of the first support layer 20.

[0087] Step 160: A bottom electrode, a piezoelectric layer, and a top electrode are sequentially formed on the second sacrificial layer; the top electrode is disposed in the resonant region, the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region, and the bottom electrode is in contact with the surface of the second protrusion away from the substrate; the distance between the surface of the first recess and the second recess adjacent to the substrate and the second surface of the substrate away from the bottom electrode is less than the distance between the surface of the first protrusion and the second protrusion adjacent to the substrate and the second surface of the substrate.

[0088] in, Figure 18 This is a schematic diagram of the fabrication process of another thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention, for reference. Figure 18 A first electrode layer is formed in the resonant region and the first edge region; the first electrode layer located on one side of the second edge region is removed to form a bottom electrode 30; a piezoelectric layer 40 is formed on the surface of the bottom electrode 30; a second electrode layer is formed on the surface of the piezoelectric layer 40; the second electrode layer in the first edge region is removed to form a top electrode 50.

[0089] Step 170: Remove the first and second sacrificial layers.

[0090] Among them, reference Figure 10 , Figures 12-18 The first sacrificial layer 12 and the second sacrificial layer 15 can be removed through the first release hole 291. A solution that can corrode the first sacrificial layer 12 and the second sacrificial layer 15 is poured into the first release hole 291, so that the first sacrificial layer 12 and the second sacrificial layer 15 are removed to form a cavity 11, while the first sacrificial layer 12 located between the first recess and the substrate 10 is retained to form a second support layer 91, which is used to enhance the stability of the overall structure.

[0091] Based on the above embodiments, this invention also provides a method for fabricating a thin-film bulk acoustic resonator. Figure 19 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention, for reference. Figure 19 The method includes:

[0092] Step 210: Provide a substrate; the resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region.

[0093] The implementation method and beneficial effects of step 210 are the same as those of step 110.

[0094] Step 220: A third sacrificial layer is formed on the first surface of the substrate, and a third groove, a fourth groove, and a fifth groove are formed on the third sacrificial layer; wherein the third groove, the fourth groove, and the fifth groove are located in the second edge region, and the third groove and the fifth groove are located on the side of the fourth groove away from the resonant region, the vertical projection of the fifth groove on the substrate covers the vertical projection of the third groove on the substrate, the third groove penetrates the third sacrificial layer, and the depth of the fourth groove and the fifth groove is less than the thickness of the sacrificial layer.

[0095] in, Figure 20 This is a schematic diagram of the sacrificial layer structure of a thin-film bulk acoustic resonator provided in Embodiment 2 of the present invention, for reference. Figure 20 A third sacrificial layer 16 is deposited on the substrate 10. For example, the third sacrificial layer 16 may be a silicon dioxide sacrificial layer. The third sacrificial layer 16 is etched to form a third groove 17. Figure 21 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention, for reference. Figure 21 The third sacrificial layer 16 is then patterned by a second etching process to form the fourth groove 18 and the fifth groove 19.

[0096] Step 230: Form a first support layer on the surface of the third sacrificial layer; the first support layer is disposed in the first edge region and the second edge region; wherein, the portion of the first support layer located in the second edge region includes a second support portion, the second support portion is located in the third groove, the second support portion is in contact with the substrate, the first support layer also includes a second suspension portion located between the second support portion and the first edge region, the second suspension portion also includes at least one third protrusion, the first edge region includes a fourth protrusion, the third protrusion is located between the fifth groove and the fourth groove, the distance between the surface of the third protrusion and the fourth protrusion adjacent to the substrate and the first surface of the substrate is greater than the distance between the surface of the second suspension portion adjacent to the substrate and the first surface of the substrate in other areas, and the second suspension portion of the first support layer is not in contact with the first surface of the substrate.

[0097] in, Figure 22 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention, for reference. Figure 22 A support layer can be formed on the surface of the third sacrificial layer 16 by a deposition process. For example, a support layer can be formed by polysilicon deposition, and the support layer can be patterned and etched to remove the support layer in the resonant region to form the first support layer 20.

[0098] Step 240: Form a fourth sacrificial layer in the first support layer; wherein the fourth sacrificial layer covers the third sacrificial layer that is not covered by the first support layer.

[0099] in, Figure 23 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention, for reference. Figure 23 A fourth sacrificial layer 161 is deposited on the first support layer, and the thickness of the fourth sacrificial layer 161 is the same as the thickness of the first support layer 20. The fourth sacrificial layer 161 is patterned and etched to remove the fourth sacrificial layer 161 covering the first support layer 20. The fourth sacrificial layer 161 is then CMP polished to make the upper surface of the fourth sacrificial layer 161 flush with the upper surface of the first support layer 20.

[0100] Step 250: A bottom electrode, a piezoelectric layer, and a top electrode are sequentially formed on the fourth sacrificial layer; the top electrode is disposed in the resonant region, the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region, and the bottom electrode is in contact with the surface of the fourth protrusion away from the substrate.

[0101] in, Figure 24 This is a flowchart of a method for fabricating a thin-film bulk acoustic resonator according to Embodiment 2 of the present invention, for reference. Figure 24 A first electrode layer is formed in the resonant region and the first edge region; the first electrode layer located on one side of the second edge region is removed to form a bottom electrode 30; a piezoelectric layer 40 is formed on the surface of the bottom electrode 30; a second electrode layer is formed on the surface of the piezoelectric layer 40; the second electrode layer in the first edge region is removed to form a top electrode 50.

[0102] Step 260: Remove the third and fourth sacrificial layers.

[0103] Among them, reference Figure 11 , Figures 20-24 The third sacrificial layer 16 and the fourth sacrificial layer 161 can be removed through the second release hole 292. A solution that can etch the third sacrificial layer 16 and the fourth sacrificial layer 161 is poured into the second release hole 292, so that the third sacrificial layer 16 and the fourth sacrificial layer 161 are removed to form a cavity, while the third sacrificial layer 16 located between the third support portion in the first support layer 20 and the substrate 10 is retained to form the third support layer 92, which is used to enhance the stability of the overall structure.

[0104] Optional, see reference Figure 20 and with Figure 21The method involves depositing a third sacrificial layer 16 on a first surface of a substrate 10, including: depositing the third sacrificial layer 16 on the substrate 10; etching the third sacrificial layer 16 to form a third groove 17, wherein the depth of the third groove 17 is equal to the thickness of the third sacrificial layer 16; performing a second etching on the third sacrificial layer 16 to form a fourth groove 18 and a fifth groove 19, wherein the depth of the fourth groove 18 and the fifth groove 19 is less than the thickness of the third sacrificial layer 16, and the depths of the fourth groove 18 and the fifth groove 19 are the same; the vertical projection of the fifth groove 19 onto the substrate 10 covers the vertical projection of the third groove 17 onto the substrate 10, and points in the direction from the second edge region to the resonant region, and the width of the fifth groove 19 is greater than the width of the third groove 16.

[0105] In particular, etching the third groove 17, the fourth groove 18 and the fifth groove 19 on the third sacrificial layer 16 helps the subsequent first support layer 20 to form the second support portion 26, the third protrusion 27 and the fourth protrusion 28. This allows for multiple reflections of transverse acoustic waves propagating along the resonator plane, effectively reducing the problem of vibration energy leakage to the substrate 10 in traditional thin-film bulk acoustic resonators and greatly improving the Q value of the resonator.

[0106] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0107] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A film bulk acoustic resonator, characterized by, include: A substrate, a first support layer, a bottom electrode, a piezoelectric layer, and a top electrode are stacked sequentially. The resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region; the top electrode is disposed in the resonant region, the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region; the first support layer is disposed in the first edge region and the second edge region; The portion of the first support layer located in the second edge region includes a first support portion and a first suspension portion. The first suspension portion includes a first recess, a first protrusion, and a second recess. The portion of the first support layer located in the first edge region includes a second protrusion. The first support portion is in contact with the substrate. The first recess, the first protrusion, the second recess, and the second protrusion are not in contact with the substrate. The first support portion, the first recess, the first protrusion, and the second recess are sequentially arranged in the direction from the second edge region to the resonant region. The first surface of the substrate adjacent to the first support layer has a cavity. The resonant region, the first edge region, and the second edge region (excluding the first support portion) are located within the cavity in the vertical projection of the substrate. The distance between the surfaces of the first recess and the second recess adjacent to the substrate and the second surface of the substrate away from the bottom electrode is less than the distance between the surfaces of the first protrusion and the second protrusion adjacent to the substrate and the second surface of the substrate. The bottom electrode is in contact with the surface of the second protrusion away from the substrate. Alternatively, the first surface of the substrate adjacent to the first support layer is planar, the portion of the first support layer located in the second edge region includes a second support portion, the second support portion is in contact with the substrate, the first support layer also includes a second floating portion located between the second support portion and the first edge region, the second floating portion also includes at least one third protrusion, the first edge region includes a fourth protrusion, the distance between the surface of the third protrusion and the fourth protrusion adjacent to the substrate and the first surface of the substrate is greater than the distance between the surface of the other region of the second floating portion adjacent to the substrate and the first surface of the substrate, the bottom electrode is in contact with the surface of the fourth protrusion away from the substrate, and the second floating portion of the first support layer is not in contact with the first surface of the substrate.

2. The resonator according to claim 1, characterized in that: The first recess and the second recess are equidistant from the second surface of the substrate, and the first protrusion, the second protrusion, and the first support are equidistant from the second surface of the substrate. The third protrusion and the fourth protrusion are at the same distance from the first surface of the substrate.

3. The resonator according to claim 1, characterized in that: The first support layer is also disposed in a portion of the resonant region; The second protrusion extends into the resonant region; The fourth protrusion extends into the resonant region.

4. The resonator according to claim 1, characterized in that, A second support layer is also included between the first recess and the substrate; The first support layer further includes a third support portion located on the side of the second support portion away from the resonant region, and a third support layer is disposed between the third support portion and the substrate.

5. The resonator according to claim 2, characterized in that, The thickness of the first support layer is 0.2-0.8 μm; The distance between the surface of the first protrusion and the second protrusion adjacent to the substrate and the bottom surface of the cavity is 2-3 μm; the depth of the first recess and the second recess is 0.6-1.5 μm; along the direction from the resonant region to the second edge region; The distance between the surface of the third protrusion and the fourth protrusion adjacent to the substrate and the first surface of the substrate is 2-3 μm; the depth of the third protrusion is 0.6-1.5 μm.

6. The resonator according to claim 1, characterized in that: The first protrusion is provided with a first release hole, which penetrates the first support layer; The third protrusion is provided with a second release hole, which penetrates the first support layer; The diameter of the first release hole and the second release hole is 10 μm.

7. The resonator of claim 1, wherein The piezoelectric layer is made of polycrystalline or single-crystal materials of AlN, AlScN, LiNbO3 and LiTaO3, and at least one of ferroelectric single-crystal materials. The material of the first support layer is polycrystalline silicon or silicon nitride.

8. A method of fabricating a film bulk acoustic resonator, characterized by, include: A substrate is provided; the resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region; A cavity is formed on the substrate; A first sacrificial layer is disposed in the cavity, and a first groove and a second groove are formed on the first sacrificial layer; wherein the first groove and the second groove are located in the second edge region, and the first groove is disposed on the side of the second groove away from the resonant region, and the depth of the first groove and the second groove is less than the thickness of the first sacrificial layer; A first support layer is formed on the first sacrificial layer; the first support layer is disposed in the first edge region and the second edge region; wherein, the portion of the first support layer located in the second edge region includes a first support portion and a first suspension portion, the first suspension portion includes a first recessed portion, a first protrusion portion and a second recessed portion, the portion of the first support layer located in the first edge region includes a second protrusion portion, the first recessed portion is located in the first groove, the second recessed portion is located in the second groove, the first support portion is in contact with the substrate, the first recessed portion, the first protrusion portion, the second recessed portion and the second protrusion portion are not in contact with the substrate, and the first support portion, the first recessed portion, the first protrusion portion and the second recessed portion are sequentially disposed in the direction from the second edge region to the resonant region; A second sacrificial layer is formed in the first support layer; wherein the second sacrificial layer covers the first sacrificial layer that is not covered by the first support layer; A bottom electrode, a piezoelectric layer, and a top electrode are sequentially formed on the second sacrificial layer; the top electrode is disposed in the resonant region, the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region, and the bottom electrode is in contact with the surface of the second protrusion away from the substrate; the distance between the surface of the first recess and the second recess adjacent to the substrate and the second surface of the substrate away from the bottom electrode is less than the distance between the surface of the first protrusion and the second protrusion adjacent to the substrate and the second surface of the substrate; Remove the first sacrificial layer and the second sacrificial layer.

9. A method for fabricating a thin-film bulk acoustic resonator, characterized in that, include: A substrate is provided; the resonator includes a resonant region and a first edge region and a second edge region surrounding the resonant region, the second edge region surrounding the first edge region; A third sacrificial layer is formed on a first surface of the substrate, and a third groove, a fourth groove, and a fifth groove are formed on the third sacrificial layer; wherein the third groove, the fourth groove, and the fifth groove are located in the second edge region, and the third groove and the fifth groove are disposed on the side of the fourth groove away from the resonant region, the vertical projection of the fifth groove on the substrate covers the vertical projection of the third groove on the substrate, the third groove penetrates the third sacrificial layer, and the depth of the fourth groove and the fifth groove is less than the thickness of the sacrificial layer; A first support layer is formed on the surface of the third sacrificial layer; the first support layer is disposed in the first edge region and the second edge region; wherein, the portion of the first support layer located in the second edge region includes a second support portion, the second support portion is located in the third groove, the second support portion is in contact with the substrate, the first support layer also includes a second suspension portion located between the second support portion and the first edge region, the second suspension portion also includes at least one third protrusion, the first edge region includes a fourth protrusion, the third protrusion is located between the fifth groove and the fourth groove, the distance between the surface of the third protrusion and the fourth protrusion adjacent to the substrate and the first surface of the substrate is greater than the distance between the surface of the other region of the second suspension portion adjacent to the substrate and the first surface of the substrate, and the second suspension portion of the first support layer is not in contact with the first surface of the substrate; A fourth sacrificial layer is formed in the first support layer; wherein the fourth sacrificial layer covers the third sacrificial layer that is not covered by the first support layer; A bottom electrode, a piezoelectric layer, and a top electrode are sequentially formed on the fourth sacrificial layer; the top electrode is disposed in the resonant region, the piezoelectric layer and the bottom electrode are disposed in the first edge region and the resonant region, and the bottom electrode is in contact with the surface of the fourth protrusion away from the substrate; Remove the third and fourth sacrificial layers.

10. The preparation method according to claim 9, characterized in that, A third sacrificial layer is formed on the first surface of the substrate, comprising: A third sacrificial layer is deposited on the substrate; The third sacrificial layer is etched to form a third groove, wherein the depth of the third groove is equal to the thickness of the third sacrificial layer; The third sacrificial layer is etched a second time to form a fourth and a fifth groove, wherein the depth of the fourth and fifth grooves is less than the thickness of the third sacrificial layer, and the depth of the fourth and fifth grooves is the same; the vertical projection of the fifth groove on the substrate covers the vertical projection of the third groove on the substrate, and points in the direction from the second edge region to the resonant region; the width of the fifth groove is greater than the width of the third groove.

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