Film bulk acoustic resonator and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor devices, and particularly discloses a film bulk acoustic resonator and a preparation method thereof, and the film bulk acoustic resonator comprises a substrate, and a lower electrode, a piezoelectric layer, a thickening layer and an upper electrode which are stacked on the substrate; the overlapped part of the projections of the lower electrode, the piezoelectric layer and the upper electrode on the substrate is an active area; an air wing and an air bridge which are positioned on two opposite sides of the active region are formed between the thickening layer and the piezoelectric layer; and at the position corresponding to the air bridge, the thickening layer and the upper electrode are sunken towards one side of the piezoelectric layer, so that the thickening layer is in contact with the piezoelectric layer to generate a piezoelectric effect, and the air bridge is divided into a first sub-air cavity and a second sub-air cavity. According to the invention, the strong parasitic peak introduced by the thickening structure can be effectively reduced, so that the resonator has better performance.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor devices, and in particular to a thin film bulk acoustic wave resonator and a method for preparing the same. Background Art

[0002] In order to improve the Q value, the prior art usually adds a thickening structure to the sandwich structure of the thin film bulk acoustic resonator (FBAR), so that the frequency of the boundary area of ​​the resonator is lower than that of the active area, thereby improving the reflection of the acoustic wave energy and suppressing the leakage of lateral energy. Although the thickening structure has a good effect in improving the Q value, it itself will bring a serious problem, that is, the thickening structure itself will also resonate at its corresponding frequency, and the resonant frequency is often lower than the main resonant frequency, introducing a strong parasitic peak in the low frequency band, which deteriorates the out-of-band suppression performance of the bandpass filter constructed by the FBAR, and cannot meet the out-of-band suppression performance requirements of the device. Summary of the invention

[0003] The purpose of the present application is to provide a thin film bulk acoustic wave resonator and a preparation method thereof, which can effectively reduce the strong parasitic peaks introduced by the thickened structure, so that the resonator has better performance.

[0004] The embodiment of the present application is implemented as follows:

[0005] In the first aspect, an embodiment of the present application provides a thin film bulk acoustic wave resonator, comprising a substrate and a lower electrode, a piezoelectric layer, a thickened layer and an upper electrode stacked on the substrate; the overlapping portion of the lower electrode, the piezoelectric layer and the upper electrode projected on the substrate is an active area; air wings and air bridges are formed between the thickened layer and the piezoelectric layer and are located on opposite sides of the active area; at a position corresponding to the air bridge, the thickened layer and the upper electrode are recessed toward one side of the piezoelectric layer so that the thickened layer contacts the piezoelectric layer to produce a piezoelectric effect, and the air bridge is divided into a first sub-air cavity and a second sub-air cavity.

[0006] As an optional implementation, the edge thickness of the lower electrode gradually decreases to form an inclined structure at the edge of the active area, and the recessed portion of the thickened layer and the upper electrode is located on the projection of the inclined structure on the substrate.

[0007] As an optional implementation, a passivation layer is provided on the side of the upper electrode facing away from the piezoelectric layer, and the passivation layer is recessed toward the piezoelectric layer at a position corresponding to the air bridge.

[0008] As an optional implementation, the thickened layer is hollowed out at a position corresponding to the active area so that the upper electrode and the piezoelectric layer form a contact area, and an annular groove is etched on the passivation layer at the edge of the contact area.

[0009] As an optional embodiment, the annular groove includes an annular groove extending along the circumference of the contact area and connected end to end, or includes a plurality of arc grooves arranged at intervals around the circumference of the contact area.

[0010] As an optional implementation, the upper electrode is made of scandium aluminum nitride, wherein the atomic ratio of aluminum element to scandium element is 3-5:1.

[0011] In a second aspect, an embodiment of the present application provides a preparation method for preparing the above-mentioned thin film bulk acoustic wave resonator, comprising:

[0012] A lower electrode and a piezoelectric layer are sequentially arranged on the substrate, and a lead-out hole is formed on the piezoelectric layer;

[0013] A thickening layer and an upper electrode are sequentially arranged on the piezoelectric layer with the lead-out hole, and the overlapping portion of the lower electrode, the piezoelectric layer and the upper electrode projected on the substrate is an active area; wherein a first sacrificial layer and a second sacrificial layer are also arranged between the piezoelectric layer and the thickening layer and located on opposite sides of the active area;

[0014] The first sacrificial layer and the second sacrificial layer are released to form air wings and air bridges in the active area, and the thickened layer on the air bridge collapses under tensile stress and contacts the piezoelectric layer to divide the air bridge into a first sub-air cavity and a second sub-air cavity.

[0015] Furthermore, a lower electrode and a piezoelectric layer are sequentially arranged on the substrate, and a lead hole is formed on the piezoelectric layer, including:

[0016] Depositing a lower electrode on the substrate, and gradually reducing the edge thickness of the lower electrode by etching or photolithography;

[0017] The piezoelectric layer is deposited so that the piezoelectric layer forms an inclined structure.

[0018] Furthermore, before releasing the first sacrificial layer and the second sacrificial layer to form an air wing and an air bridge in the active area, and the thickened layer on the air bridge collapses under tensile stress and contacts the piezoelectric layer to divide the air bridge into a first sub-air cavity and a second sub-air cavity, the method further includes:

[0019] The positions of the thickened layer corresponding to the active area are etched and hollowed out to form a contact area between the upper electrode and the piezoelectric layer.

[0020] Furthermore, before releasing the first sacrificial layer and the second sacrificial layer to form an air wing and an air bridge in the active area, and the thickened layer on the air bridge collapses under tensile stress and contacts the piezoelectric layer to divide the air bridge into a first sub-air cavity and a second sub-air cavity, the method further includes:

[0021] A passivation layer is deposited on the upper electrode, and an annular groove is etched on the passivation layer at the edge of the contact area.

[0022] The beneficial effects of the embodiments of the present application include:

[0023] The embodiment of the present application provides a thin film bulk acoustic wave resonator, including a substrate and a lower electrode, a piezoelectric layer, a thickened layer and an upper electrode stacked on the substrate; the overlapping portion of the lower electrode, the piezoelectric layer and the upper electrode projected on the substrate is an active area. In the embodiment of the present application, air wings and air bridges located on opposite sides of the active area are formed between the thickened layer and the piezoelectric layer. In the embodiment of the present application, at the position corresponding to the air bridge, the thickened layer and the upper electrode are recessed toward one side of the piezoelectric layer so that the thickened layer contacts the piezoelectric layer to produce a piezoelectric effect, and the air bridge is divided into a first sub-air cavity and a second sub-air cavity. In the embodiment of the present application, an additional electric field effect is generated in the air bridge part through the contact between the thickened layer and the piezoelectric layer. Through this electric field effect, the strong parasitic peaks introduced by the thickened layer structure are effectively reduced, and the out-of-band suppression performance of the filter constructed by the thin film bulk acoustic wave resonator is effectively improved.

[0024] The preparation method provided in the embodiment of the present application is used to prepare the above-mentioned thin film bulk acoustic wave resonator, including: sequentially arranging a lower electrode and a piezoelectric layer on a substrate, forming an extraction hole on the piezoelectric layer; sequentially arranging a thickening layer and an upper electrode on the piezoelectric layer with the extraction hole, and the overlapping part of the lower electrode, the piezoelectric layer and the upper electrode projected on the substrate is an active area; wherein a first sacrificial layer and a second sacrificial layer located on opposite sides of the active area are also arranged between the piezoelectric layer and the thickening layer; releasing the first sacrificial layer and the second sacrificial layer to form an air wing and an air bridge in the active area, and the thickening layer located on the air bridge collapses under tensile stress and contacts the piezoelectric layer, so as to divide the air bridge into a first sub-air cavity and a second sub-air cavity. The preparation method provided in the embodiment of the present application utilizes the film tensile stress of the thickening layer and the upper electrode to form a recessed portion between the thickening layer and the upper electrode, realizes the contact between the thickening layer and the piezoelectric layer, effectively reduces the strong parasitic peak introduced by the thickening layer structure, and effectively improves the out-of-band suppression performance of the filter constructed by the thin film bulk acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is one of the structural schematic diagrams of the thin film bulk acoustic resonator according to an embodiment of the present application;

[0027] Figure 2 This is the second structural schematic diagram of the thin film bulk acoustic wave resonator according to the embodiment of the present application;

[0028] Figure 3 This is the third structural diagram of the thin film bulk acoustic resonator according to the embodiment of the present application;

[0029] Figure 4 This is the fourth structural diagram of the thin film bulk acoustic wave resonator according to the embodiment of the present application;

[0030] Figure 5 This is the fifth structural diagram of the thin film bulk acoustic wave resonator according to the embodiment of the present application;

[0031] Figure 6a Series FBAR and parallel FBAR constructed for the prior art;

[0032] Figure 6b Test graphs for bandpass filters constructed for prior art;

[0033] Figure 7 This is a comparison diagram of the impedance of the thin film bulk acoustic wave resonator provided by the prior art and the embodiment of the present application;

[0034] Figure 8 Test graph of the bandpass filter constructed for this application.

[0035] icon:

[0036] 101-substrate; 102-cavity; 103-lower electrode; 1031-lower electrode inclination angle; 1032-seed layer; 104-piezoelectric layer; 1041-lead-out hole; 1051-first sacrificial layer; 1052-second sacrificial layer; 106-thickening layer; 1061-lead-out hole thickening layer; 1062-left thickening layer; 1063-right thickening layer; 107-upper electrode; 1071-lead-out upper electrode; 108-passivation layer; 109-annular groove; 113-air wing; 114-air bridge; 1141-first sub-air cavity; 1142-recess; 1143-second sub-air cavity; 1101-first protective layer; 1102-second protective layer; 401-second parasitic peak; 402-first parasitic peak; 403-protrusion; 404-left out-of-band suppression condition. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0039] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0040] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] In order to improve the Q value, the prior art usually adds a thickening structure to the sandwich structure of the thin film bulk acoustic resonator (FBAR), so that the frequency of the boundary area of ​​the resonator is lower than that of the active area, thereby improving the reflection of the acoustic wave energy and suppressing the leakage of lateral energy. Although the thickening structure has a good effect in improving the Q value, it itself will bring a serious problem, that is, the thickening structure itself will also resonate at its corresponding frequency, and the resonant frequency is often lower than the main resonant frequency, introducing a strong parasitic peak in the low frequency band, which deteriorates the out-of-band suppression performance of the bandpass filter constructed by the FBAR, and cannot meet the out-of-band suppression performance requirements of the device.

[0042] In order to solve the above technical problems, the embodiments of the present application provide a thin film bulk acoustic wave resonator and a preparation method thereof.

[0043] Reference Figure 3 , Figure 5As shown, an embodiment of the present application provides a thin film bulk acoustic wave resonator, including a substrate 101 and a lower electrode 103, a piezoelectric layer 104, a thickening layer 106 and an upper electrode 107 stacked on the substrate 101; the overlapping portion of the lower electrode 103, the piezoelectric layer 104 and the upper electrode 107 projected on the substrate 101 is an active area; an air wing 113 and an air bridge 114 located on opposite sides of the active area are formed between the thickening layer 106 and the piezoelectric layer 104; at a position corresponding to the air bridge 114, the thickening layer 106 and the upper electrode 107 are recessed toward one side of the piezoelectric layer 104, so that the thickening layer 106 contacts the piezoelectric layer 104 to generate a piezoelectric effect, and the air bridge 114 is divided into a first sub-air cavity 1141 and a second sub-air cavity 1143.

[0044] It should be noted that the prior art can maximize the performance of the device, such as K value, Q value, and FOM value, by optimizing the width and thickness of the three structures of the thickened layer 106 , the air wing 113 , and the air bridge 114 .

[0045] The embodiment of the present application solves the problem of strong parasitic peaks caused by the thickened layer 106 while retaining the above-mentioned performance.

[0046] It should be noted that, in the embodiment of the present application, at the position corresponding to the air bridge 114, an additional electric field effect is generated through the recessed portion 1142 of the thickened layer 106 and the contact with the piezoelectric layer 104. Through this electric field effect, the strong parasitic peak introduced by the thickened layer 106 structure is effectively reduced, and the out-of-band suppression performance of the filter constructed by the thin film bulk acoustic resonator is effectively improved.

[0047] Among them, Figure 6a As shown, the left sides of the low-frequency parallel FBAR and the high-frequency series FBAR in the prior art have a first parasitic peak 402 and a second parasitic peak 401, respectively. Figure 6b In the process of the bandpass filter shown, it is inevitable that the left side out-of-band suppression of the filter forms a bulge 403, so that it does not meet the left side out-of-band suppression condition 404. Generally, the out-of-band suppression is below -30dB. If it conflicts with a special frequency band, the out-of-band suppression requirement may be higher.

[0048] like Figure 7 As shown, a comparison diagram of the impedance curves of the thin film bulk acoustic wave resonator provided by the prior art and the present application is shown, wherein the prior art is represented by a dotted line and the present application is represented by a solid line, which can effectively eliminate the strong parasitic peak on the left.

[0049] like Figure 8 As shown, the curve obtained by testing the bandpass filter constructed by the thin film bulk acoustic wave resonator provided in the embodiment of the present application effectively enhances the out-of-band suppression performance.

[0050] In the process of preparing the thickening layer 106 and the piezoelectric layer 104 by vapor deposition, the gas flow rate can be controlled so that the formed thickening layer 106 and the piezoelectric layer 104 film have tensile stress. During the preparation, after the sacrificial layer is removed, the above-mentioned recess 1142 is formed by tensile stress.

[0051] For example, in the vapor deposition process for preparing the thickening layer 106 and the upper electrode 107, the target material is scandium aluminum nitride, and the argon gas flow rate is 19-24 cm 3 / min; nitrogen gas flow rate is 95-120cm 3 / min, and the RF bias power is 15-30 W. The above settings can generate a film tensile stress of about 50 MPa.

[0052] Among them, the atomic ratio of aluminum element to scandium element in scandium aluminum nitride is 3-5:1.

[0053] It should be noted that the recessed portion 1142 between the thickened layer 106 and the piezoelectric layer 104 can be located at the center of the air bridge 114, or can be at a certain distance from the center. In addition, the contact area between the thickened layer 106 and the piezoelectric layer 104 is not particularly limited in the present embodiment, and those skilled in the art can select it according to their needs.

[0054] It should be noted that, refer to Figure 5 As shown, the thickened layer 106 and the upper electrode 107 are recessed toward one side of the piezoelectric layer 104 so that the thickened layer 106 contacts the piezoelectric layer 104 to generate a piezoelectric effect and divide the air bridge 114 into a first sub-air cavity 1141 and a second sub-air cavity 1143 .

[0055] The first sub-air cavity 1141 and the second sub-air cavity 1143 may be two independent air cavities, or the first sub-air cavity 1141 and the second sub-air cavity 1143 may be connected to each other, and those skilled in the art may make the configuration as required.

[0056] More preferably, the edge thickness of the lower electrode 103 gradually decreases to form an inclined structure at the edge of the active area, and the recessed portion 1142 of the thickened layer 106 and the upper electrode 107 is located on the projection of the inclined structure on the substrate 101 .

[0057] In the embodiment of the present application, the position opposite to the contact portion between the piezoelectric layer 104 and the thickened layer 106 is the edge of the lower electrode 103 , and the edge thickness of the lower electrode 103 gradually decreases, resulting in a tilt angle.

[0058] The lower electrode 103 may have an inclination angle of 10-30°. Since the piezoelectric layer 104 is laid on the lower electrode 103, the piezoelectric layer 104 also generates a corresponding inclined structure. At this time, the thickened layer 106 and the recessed portion 1142 of the upper electrode 107 are located on the projection of the inclined structure on the substrate 101. When the thickened layer 106 contacts the inclined structure of the piezoelectric layer 104, the electric field effect generated by the thickened layer 106 can more effectively eliminate the parasitic peak problem caused by the thickened layer 106.

[0059] Reference Figure 5 As shown, as an optional implementation, a passivation layer 108 is provided on the side of the upper electrode 107 facing away from the piezoelectric layer 104 , and the passivation layer 108 is recessed toward the piezoelectric layer 104 at a position corresponding to the air bridge 114 .

[0060] The passivation layer 108 may be any one of AlN, SiC, SiO2, and SiN. It should be noted that the passivation layer 108 is generally not easy to absorb moisture, and can prevent the underlying film from being oxidized, and can play a good protective role.

[0061] Reference Figure 5 As shown, as an optional implementation, the thickened layer 106 is hollowed out at a position corresponding to the active area so that the upper electrode 107 forms a contact area with the piezoelectric layer 104, and an annular groove 109 is etched on the passivation layer 108 at the edge of the contact area.

[0062] It should be noted that the width of the annular groove 109 can be kept consistent or inconsistent, and those skilled in the art can set it according to needs.

[0063] As an optional embodiment, the annular groove 109 includes an annular groove extending along the circumference of the contact area and connected end to end, or includes a plurality of arc grooves arranged at intervals around the circumference of the contact area.

[0064] The present application provides a preparation method for preparing the above-mentioned thin film bulk acoustic wave resonator, comprising:

[0065] Reference Figure 1 , Figure 2 As shown, a lower electrode 103 and a piezoelectric layer 104 are sequentially arranged on a substrate 101, and a lead hole 1041 is formed on the piezoelectric layer 104;

[0066] A thickening layer 106 and an upper electrode 107 are sequentially arranged on the piezoelectric layer 104 formed with the lead-out hole 1041, and the overlapping portion of the projection of the lower electrode 103, the piezoelectric layer 104 and the upper electrode 107 on the substrate 101 is an active region; wherein a first sacrificial layer 1051 and a second sacrificial layer 1052 are also arranged between the piezoelectric layer 104 and the thickening layer 106 and located on opposite sides of the active region;

[0067] Reference Figure 5 As shown, the first sacrificial layer 1051 and the second sacrificial layer 1052 are released to form an air wing 113 and an air bridge 114 in the active area, and the thickened layer 106 located on the air bridge 114 collapses due to tensile stress and contacts the piezoelectric layer 104. At this time, the thickened layer 106 collapses due to the tensile stress, and the thickened layer 106 moves downward until it contacts the piezoelectric layer 104 to divide the air bridge 114 into a first sub-air cavity 1141 and a second sub-air cavity 1143. In addition, the mass distribution of the thickened layer 106 is uneven, and the mass of the thickened layer 106 in the area where the recess 1142 is projected downward is greater than that of other parts of the thickened layer 106.

[0068] The preparation method provided in the embodiment of the present application utilizes the thin film tensile stress of the thickened layer 106 and the upper electrode 107 to make the thickened layer 106 and the upper electrode 107 concave to form a recessed portion 1142, thereby achieving contact between the thickened layer 106 and the piezoelectric layer 104, effectively reducing the strong parasitic peaks introduced by the thickened layer 106 structure, and effectively improving the out-of-band suppression performance of the filter constructed by the thin film bulk acoustic wave resonator.

[0069] Furthermore, a lower electrode 103 and a piezoelectric layer 104 are sequentially arranged on the substrate 101, and a lead-out hole 1041 is formed on the piezoelectric layer 104, including:

[0070] Reference Figure 2 , Figure 3 As shown, a lower electrode 103 is deposited on a substrate 101, and the edge thickness of the lower electrode 103 is gradually reduced by etching;

[0071] The piezoelectric layer 104 is deposited so that the piezoelectric layer 104 forms an inclined structure.

[0072] It should be noted that the cavity 102 is etched on the substrate 101, and a cavity sacrificial layer is filled in the cavity 102; then a seed layer 1032 is first deposited on the substrate 101, and then a patterned lower electrode 103 is deposited. The lower electrode tilt angle 1031 is formed by etching or photolithography.

[0073] Further, before the first sacrificial layer 1051 and the second sacrificial layer 1052 are released to form the air wing 113 and the air bridge 114 in the active area, the thickened layer 106 located on the air bridge 114 collapses under tensile stress and contacts the piezoelectric layer 104 to divide the air bridge 114 into the first sub-air cavity 1141 and the second sub-air cavity 1143, the method further includes:

[0074] The thickened layer 106 is etched and hollowed out at positions corresponding to the active area so that the upper electrode 107 forms a contact area with the piezoelectric layer 104, wherein the mass of the thickened layer 106 is unevenly distributed, and the mass of the thickened layer 106 in the area projected downward by the recess 1142 is greater than that of other parts of the thickened layer 106.

[0075] Specifically, the thickening layer 106 is deposited and patterned to form the lead-out hole thickening layer 1061 , the left thickening layer 1062 , and the right thickening layer 1063 . In addition, the thickening layer 106 at the lead-out hole has the function of leading out the lower electrode 103 .

[0076] Further, before the first sacrificial layer 1051 and the second sacrificial layer 1052 are released to form the air wing 113 and the air bridge 114 in the active area, the thickened layer 106 located on the air bridge 114 collapses under tensile stress and contacts the piezoelectric layer 104 to divide the air bridge 114 into the first sub-air cavity 1141 and the second sub-air cavity 1143, the method further includes:

[0077] Reference Figure 4 As shown, a passivation layer 108 is deposited on the upper electrode 107 , and an annular groove 109 is etched on the passivation layer 108 at the edge of the contact region.

[0078] The lead-out thickening layer 106 is covered with the lead-out upper electrode 1071 , and the passivation layer 108 is hollowed out by patterning the passivation layer 108 . Then, the lead-out hole 1041 and the upper electrode 107 are covered with a first protective layer 1101 and a second protective layer 1102 , respectively.

[0079] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A thin film bulk acoustic resonator, characterized in that: The invention comprises a substrate (101) and a lower electrode (103), a piezoelectric layer (104), a thickening layer (106) and an upper electrode (107) stacked on the substrate (101); the overlapping portion of the lower electrode (103), the piezoelectric layer (104) and the upper electrode (107) projected on the substrate (101) is an active area; an air wing (113) and an air bridge (114) located on opposite sides of the active area are formed between the thickening layer (106) and the piezoelectric layer (104); at a position corresponding to the air bridge (114), the thickening layer (106) and the upper electrode (107) are recessed toward one side of the piezoelectric layer (104), so that the thickening layer (106) and the piezoelectric layer (104) are in contact with each other to generate a piezoelectric effect, and the air bridge (114) is divided into a first sub-air cavity (1141) and a second sub-air cavity (1143).

2. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: The edge thickness of the lower electrode (103) gradually decreases to form an inclined structure at the edge of the active area, and the recessed portion (1142) of the thickened layer (106) and the upper electrode (107) is located on the projection of the inclined structure on the substrate (101).

3. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: A passivation layer (108) is provided on the side of the upper electrode (107) facing away from the piezoelectric layer (104), and the passivation layer (108) is recessed toward the side of the piezoelectric layer (104) at a position corresponding to the air bridge (114).

4. The thin film bulk acoustic wave resonator according to claim 3, characterized in that: The thickened layer (106) is hollowed out at a position corresponding to the active area so that the upper electrode (107) and the piezoelectric layer (104) form a contact area, and an annular groove (109) is etched on the passivation layer (108) at the edge of the contact area.

5. The thin film bulk acoustic resonator according to claim 4, characterized in that: The annular groove (109) comprises an annular groove extending along the circumference of the contact area and connected end to end, or comprises a plurality of arc-shaped grooves arranged at intervals around the circumference of the contact area.

6. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: The upper electrode (107) is made of scandium aluminum nitride, wherein the atomic ratio of aluminum element to scandium element is 3-5:

1.

7. A method for preparing the thin film bulk acoustic resonator according to any one of claims 1 to 6, characterized in that: include: A lower electrode (103) and a piezoelectric layer (104) are sequentially arranged on a substrate (101), and an extraction hole (1041) is formed on the piezoelectric layer (104); A thickening layer (106) and an upper electrode (107) are sequentially arranged on a piezoelectric layer (104) formed with an extraction hole (1041); the overlapping portion of the lower electrode (103), the piezoelectric layer (104) and the upper electrode (107) projected on the substrate (101) is an active region; wherein a first sacrificial layer (1051) and a second sacrificial layer (1052) are also arranged between the piezoelectric layer (104) and the thickening layer (106) and located on opposite sides of the active region; The first sacrificial layer (1051) and the second sacrificial layer (1052) are released to form an air wing (113) and an air bridge (114) in the active area, and the thickened layer (106) located on the air bridge (114) collapses under tensile stress and contacts the piezoelectric layer (104), so as to divide the air bridge (114) into a first sub-air cavity (1141) and a second sub-air cavity (1143).

8. The preparation method according to claim 7, characterized in that: The method comprises sequentially arranging a lower electrode (103) and a piezoelectric layer (104) on a substrate (101), and forming an extraction hole (1041) on the piezoelectric layer (104), comprising: Depositing the lower electrode (103) on the substrate (101), and gradually reducing the edge thickness of the lower electrode (103) by etching or photolithography; The piezoelectric layer (104) is deposited so that the piezoelectric layer (104) forms an inclined structure.

9. The preparation method according to claim 7, characterized in that: Before the first sacrificial layer (1051) and the second sacrificial layer (1052) are released to form an air wing (113) and an air bridge (114) in the active area, and the thickened layer (106) on the air bridge (114) collapses under tensile stress and contacts the piezoelectric layer (104) to divide the air bridge (114) into a first sub-air cavity (1141) and a second sub-air cavity (1143), the method further comprises: The thickened layer (106) is etched and hollowed out at a position corresponding to the active area, so that the upper electrode (107) forms a contact area with the piezoelectric layer (104).

10. The preparation method according to claim 9, characterized in that: Before the first sacrificial layer (1051) and the second sacrificial layer (1052) are released to form an air wing (113) and an air bridge (114) in the active area, and the thickened layer (106) on the air bridge (114) collapses under tensile stress and contacts the piezoelectric layer (104) to divide the air bridge (114) into a first sub-air cavity (1141) and a second sub-air cavity (1143), the method further comprises: A passivation layer (108) is deposited on the upper electrode (107), and an annular groove (109) is etched on the passivation layer (108) at the edge of the contact area.

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