Bulk acoustic wave resonator preparation method, bulk acoustic wave resonator and filter

Abstract

The invention relates to the technical field of semiconductors, in particular to a bulk acoustic wave resonator preparation method, a bulk acoustic wave resonator and a filter, and the method comprises the steps: sequentially arranging a bottom electrode layer, a piezoelectric layer, an upper electrode layer and a passivation layer on the surface of a substrate in a stacked manner; wherein the overlapped part of the projections of the bottom electrode layer, the piezoelectric layer and the upper electrode layer on the substrate is an active area; forming a protective layer on the surface of the passivation layer by adopting an atomic deposition process; and forming a groove on the protective layer, wherein the groove is located at the edge of the active region. According to the invention, the grooves are formed in the atomic deposition protection layer, so that the generation of sub-resonance at the upper electrode layer can be effectively avoided, and the device performance can be improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing a bulk acoustic wave resonator, a bulk acoustic wave resonator and a filter. Background Art

[0002] BAW resonators can use the piezoelectric effect to convert mechanical vibrations into electrical signal outputs. When the BAW resonator is working, the sound waves will produce lateral parasitic modes, which will eventually be lost at the edge position, resulting in energy loss. In order to suppress this energy loss, the prior art usually adds grooves at the edge of the top electrode layer. This type of structure will lead to secondary resonances, which will affect the performance of the filter. When grooves are set at the edge of the top electrode, the geometry of the grooves will change suddenly, resulting in local mechanical stress concentration. This stress concentration will affect the propagation path of the sound waves in the resonator, causing the sound waves to reflect, scatter or diffract near the grooves, thereby interfering with the main resonant mode. Summary of the invention

[0003] The purpose of the present application is to provide a bulk acoustic wave resonator preparation method, a bulk acoustic wave resonator and a filter, which can effectively avoid the generation of secondary resonance at the upper electrode layer by forming grooves on the atomically deposited protective layer, thereby improving device performance.

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

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a bulk acoustic wave resonator, comprising:

[0006] providing a substrate;

[0007] A bottom electrode layer, a piezoelectric layer, an upper electrode layer and a passivation layer are sequentially stacked on the surface of the substrate; wherein the overlapping portion of the bottom electrode layer, the piezoelectric layer and the upper electrode layer projected on the substrate is an active area;

[0008] forming a protective layer on the surface of the passivation layer by using an atomic deposition process;

[0009] A groove is formed on the protection layer, wherein the groove is located at an edge of the active area.

[0010] As an optional implementation, the bottom electrode layer, the piezoelectric layer, the top electrode layer and the passivation layer are sequentially stacked on the surface of the substrate, including:

[0011] etching through holes in the piezoelectric layer;

[0012] A first hollow portion and a second hollow portion are formed in the passivation layer; wherein the through hole is connected with the first hollow portion to form a lead channel, and the projection of the lead channel is located on the bottom electrode layer; and the projection of the second hollow portion is located on the upper electrode layer;

[0013] forming a first electrode in the first hollow portion, wherein the first electrode is used to connect to the bottom electrode layer;

[0014] A second electrode is formed in the second hollow portion, and the second electrode is used to be connected to the upper electrode layer.

[0015] As an optional implementation manner, the step of forming a protective layer on a surface of the passivation layer facing away from the substrate by using an atomic deposition process comprises:

[0016] The protection layer is patterned to allow the first electrode and the second electrode to leak out.

[0017] As an optional implementation, the substrate has a cavity;

[0018] The method of forming a protective layer on a surface of the passivation layer facing away from the substrate by using an atomic deposition process also includes:

[0019] The protective layer is formed on the inner wall of the cavity.

[0020] As an optional implementation, before forming the protective layer on the surface of the passivation layer facing away from the substrate by using the atomic deposition process, the method includes:

[0021] forming a release channel on the bottom electrode layer, the piezoelectric layer, the upper electrode layer and the passivation layer, wherein the release channel is connected to the cavity;

[0022] The method of forming a protective layer on a surface of the passivation layer facing away from the substrate by using an atomic deposition process also includes:

[0023] The protective layer is formed on the inner wall of the release channel.

[0024] In a second aspect, an embodiment of the present application provides a bulk acoustic wave resonator, which adopts the above-mentioned preparation method. The bulk acoustic wave resonator includes a substrate and a bottom electrode layer, a piezoelectric layer, an upper electrode layer and a passivation layer stacked in sequence on the substrate; the overlapping part of the bottom electrode layer, the piezoelectric layer and the upper electrode layer projected on the substrate is an active area; a protective layer is formed on the surface of the passivation layer facing away from the substrate, a groove is formed on the protective layer, and the groove is located at the edge of the active area.

[0025] As an optional implementation, a cavity is formed on the substrate, and the inner wall of the cavity forms the protective layer.

[0026] As an optional implementation, a release channel communicating with the cavity is formed on the BAW resonator; and the protective layer is formed on an inner wall of the release channel.

[0027] As an optional implementation, the substrate includes a first substrate, a middle insulating layer and a second substrate which are stacked.

[0028] On the other hand, an embodiment of the present application provides a filter, including the above-mentioned BAW resonator and an input port and an output port electrically connected to the BAW resonator, wherein there are multiple BAW resonators, and the multiple BAW resonators are connected in series and / or in parallel.

[0029] The beneficial effects of the embodiments of the present application include:

[0030] The embodiment of the present application provides a method for preparing a bulk acoustic wave resonator, including: providing a substrate; sequentially stacking a bottom electrode layer, a piezoelectric layer, an upper electrode layer and a passivation layer on the surface of the substrate; wherein the overlapping portion of the bottom electrode layer, the piezoelectric layer and the upper electrode layer projected on the substrate is an active area; forming a protective layer on the surface of the passivation layer by an atomic deposition process; forming a groove on the protective layer, wherein the groove is located at the edge of the active area. The embodiment of the present application uses atomic deposition to form a protective layer, and forms a groove on the protective layer. Compared with the prior art, the embodiment of the present application does not form a groove structure on the upper electrode layer, so that the acoustic wave will not undergo complex changes at the edge of the upper electrode layer, and can effectively avoid the generation of secondary resonance at the upper electrode layer, which is beneficial to improving device performance.

[0031] The embodiment of the present application provides a bulk acoustic wave resonator, which adopts the above-mentioned preparation method. The bulk acoustic wave resonator includes a substrate and a bottom electrode layer, a piezoelectric layer, an upper electrode layer and a passivation layer stacked in sequence on the substrate; the overlapping portion of the bottom electrode layer, the piezoelectric layer and the upper electrode layer projected on the substrate is the active area; a protective layer is formed on the surface of the passivation layer facing away from the substrate, and a groove is formed on the protective layer, and the groove is located at the edge of the active area. The bulk acoustic wave resonator provided by the embodiment of the present application can effectively avoid the generation of sub-resonance at the upper electrode layer by forming a groove on the atomically deposited protective layer, which is beneficial to improving the performance of the device. In addition, the protective layer of the embodiment of the present application can reliably protect the bulk acoustic wave resonator, effectively prevent water vapor from interfering with the device, and improve the service life of the device.

[0032] The embodiment of the present application provides a filter, including the above-mentioned BAW resonator and an input port and an output port electrically connected to the BAW resonator, wherein there are multiple BAW resonators, and the multiple BAW resonators are connected in series and / or in parallel. The embodiment of the present application adopts the above-mentioned boost wave resonator, which can reduce the influence of sub-resonance and effectively improve the performance of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 This is one of the structural schematic diagrams of the bulk acoustic wave resonator according to the embodiment of the present application;

[0035] Figure 2 This is the second structural schematic diagram of the bulk acoustic wave resonator of the embodiment of the present application;

[0036] Figure 3 This is the third structural diagram of the bulk acoustic wave resonator of the embodiment of the present application;

[0037] Figure 4 This is the fourth structural diagram of the bulk acoustic wave resonator of the embodiment of the present application;

[0038] Figure 5 This is the fifth structural diagram of the bulk acoustic wave resonator of the embodiment of the present application;

[0039] Figure 6 This is the sixth structural diagram of the bulk acoustic wave resonator of the embodiment of the present application;

[0040] Figure 7 It is a test diagram of the resonator frequency-impedance characteristics of the prior art and the embodiment of the present application.

[0041] icon:

[0042] 100-substrate; 101-bottom electrode layer; 102-piezoelectric layer; 103-upper electrode layer; 104-passivation layer; 105-protective layer; 106-groove; 107-through hole; 108-first hollow portion; 109-second hollow portion; 110-first electrode; 111-second electrode; 112-cavity; 113-release channel; 114-input port; 115-output port; 116-seed layer. DETAILED DESCRIPTION

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] BAW resonators can use the piezoelectric effect to convert mechanical oscillations into electrical signal outputs. When the BAW resonator is working, the sound waves will produce lateral parasitic modes, which will eventually be lost at the edge position, resulting in energy loss. In order to suppress this energy loss, the prior art usually adds a groove 106 at the edge of the top electrode layer. This type of structure will lead to secondary resonance, which will affect the performance of the filter. When the groove 106 is set at the edge of the top electrode, the geometry of the groove 106 will change suddenly, resulting in local mechanical stress concentration. This stress concentration will affect the propagation path of the sound wave in the resonator, causing the sound wave to reflect, scatter or diffract near the groove 106, thereby interfering with the main resonant mode.

[0048] In order to solve the above technical problems, the embodiments of the present application provide a method for preparing a bulk acoustic wave resonator, a bulk acoustic wave resonator and a filter.

[0049] Reference Figure 1 As shown, the embodiment of the present application provides a method for preparing a bulk acoustic wave resonator, comprising:

[0050] Providing a substrate 100;

[0051] A bottom electrode layer 101, a piezoelectric layer 102, an upper electrode layer 103 and a passivation layer 104 are sequentially stacked on the surface of the substrate 100; wherein the overlapping portion of the bottom electrode layer 101, the piezoelectric layer 102 and the upper electrode layer 103 projected on the substrate 100 is an active area;

[0052] A protective layer 105 is formed on the surface of the passivation layer 104 by using an atomic deposition process;

[0053] A groove 106 is formed on the protection layer 105 , and the groove 106 is located at the edge of the active area.

[0054] It should be noted that the embodiment of the present application provides a passivation layer 104 on the upper electrode layer 103, which can protect the upper electrode layer 103 on the one hand, and can also play a frequency modulation role on the other hand, which is used for thinning the resonator so that the frequency of the resonator reaches the target frequency.

[0055] It should be noted that the sub-resonance refers to other unnecessary vibration modes except the main resonance mode. The sub-resonance will interfere with the main resonance frequency and reduce the performance of the resonator.

[0056] In the prior art, a groove 106 structure is usually constructed on the top electrode layer or the passivation layer 104 to eliminate sub-resonance. However, such a structure has extremely high requirements on the position in the device and is small in size, which increases the difficulty of process preparation. In addition, the groove 106 will be damaged during the thinning and frequency modulation process of the passivation layer 104, which reduces the product yield and is not conducive to large-scale production.

[0057] It should be noted that the embodiment of the present application uses atomic deposition to form the protective layer 105 on the surface of the passivation layer 104, which can form a uniform and highly controllable thin film. It deposits only a single atomic layer or molecular layer in each cycle through layer-by-layer deposition, so that precise control at the nanometer level or even sub-nanometer level can be achieved.

[0058] The embodiment of the present application uses atomic deposition to form the protective layer 105, and forms a groove 106 on the protective layer 105. Compared with the prior art, the embodiment of the present application does not form a groove 106 structure on the upper electrode layer 103, so that the acoustic wave will not produce complex changes at the edge of the upper electrode layer 103, and can effectively avoid the generation of sub-resonance at the upper electrode layer 103, which is conducive to improving the performance of the device.

[0059] For the resonator frequency-impedance characteristic test of the prior art and the embodiment of the present application, refer to Figure 7 As shown, the WithoutI N line represents the resonator designed in the prior art. Figure 7 It can be seen that there are relatively serious subharmonics. Another frequency-impedance characteristic curve of the bulk acoustic wave resonator provided in the embodiment of the present application is shown in FIG. Figure 7It can be clearly seen that the embodiment of the present application is relatively smooth and can effectively solve the problem of subharmonics.

[0060] It should be noted that, firstly, the embodiment of the present application can effectively prevent the influence of external environmental factors such as moisture, oxygen, and dust on the resonator through the provision of the protective layer 105, thereby extending its practical life. Second, the atomically deposited protective layer 105 can enhance the mechanical strength of the resonator and reduce damage caused by external shock or vibration. Third, the atomically deposited protective layer 105 used in the embodiment of the present application can reduce parasitic capacitance and inductance, and improve the frequency response and signal integrity of the resonator. Fourth, the protective layer 105 deposited in the embodiment of the present application can improve the thermal stability of the resonator and ensure that it maintains stable performance under different temperature environments.

[0061] It should be noted that the specific material and thickness of the protective layer 105 can be set by those skilled in the art as required, and are not particularly limited thereto.

[0062] Exemplarily, the protection layer 105 may be an aluminum oxide layer. The aluminum oxide layer has excellent insulation properties and chemical stability and is often used to protect the electrodes and substrate 100 of the resonator.

[0063] Exemplarily, an aluminum nitride layer is formed on the passivation layer 104 by atomic deposition. The aluminum nitride layer has good acoustic properties and thermal conductivity and is suitable for high-frequency resonators and piezoelectric devices.

[0064] Exemplarily, a silicon dioxide layer is formed on the passivation layer 104 by atomic deposition. The silicon dioxide layer has excellent insulation and corrosion resistance and is suitable for protecting the surface and interface of the resonator.

[0065] Exemplarily, a barium titanate layer is formed on the passivation layer 104 by atomic deposition. The barium titanate layer has excellent piezoelectric properties and is suitable for manufacturing high-performance piezoelectric resonators.

[0066] Reference Figure 2 , Figure 3 As shown, as an optional implementation, a bottom electrode layer 101, a piezoelectric layer 102, an upper electrode layer 103 and a passivation layer 104 are sequentially stacked on the surface of a substrate 100, including:

[0067] Etching a through hole 107 on the piezoelectric layer 102;

[0068] A first hollow portion 108 and a second hollow portion 109 are formed in the passivation layer 104; wherein the through hole 107 is connected to the first hollow portion 108 to form a lead channel, and the projection of the lead channel is located on the bottom electrode layer 101; the projection of the second hollow portion 109 is located on the upper electrode layer 103;

[0069] A first electrode 110 is formed in the first hollow portion 108 , and the first electrode 110 is used to connect to the bottom electrode layer 101 ;

[0070] A second electrode 111 is formed in the second hollow portion 109 , and the second electrode 111 is used to be connected to the upper electrode layer 103 .

[0071] Reference Figure 4 As shown, as an optional implementation, a protective layer 105 is formed on a surface of the passivation layer 104 facing away from the substrate 100 by using an atomic deposition process, including:

[0072] The protection layer 105 is patterned to allow the first electrode 110 and the second electrode 111 to be exposed.

[0073] Reference Figure 3 , Figure 4 As shown, as an optional implementation, the substrate 100 has a cavity 112;

[0074] The protective layer 105 is formed on the surface of the passivation layer 104 facing away from the substrate 100 by using an atomic deposition process, and further includes:

[0075] A protection layer 105 is formed on the inner wall of the cavity 112 .

[0076] Reference Figure 3 , Figure 4 As shown, as an optional implementation, before forming the protective layer 105 on the surface of the passivation layer 104 facing away from the substrate 100 by using an atomic deposition process, the method includes:

[0077] A release channel 113 is formed on the bottom electrode layer 101, the piezoelectric layer 102, the upper electrode layer 103 and the passivation layer 104, and the release channel 113 is connected to the cavity 112;

[0078] The protective layer 105 is formed on the surface of the passivation layer 104 facing away from the substrate 100 by using an atomic deposition process, and further includes:

[0079] A protective layer 105 is formed on the inner wall of the release channel 113 .

[0080] It should be noted that the protection layer 105 can be formed on the surface of the passivation layer 104 , the inner wall of the cavity 112 , and the inner wall of the release channel 113 by a single atomic deposition process.

[0081] It should be noted that the atomic deposition process can achieve uniform deposition of the protective layer 105 on the complex geometric structure of the resonator, ensuring that each part is fully protected. In addition, it can achieve good coverage in structures such as holes and grooves with high aspect ratios, avoiding performance degradation caused by local defects.

[0082] Reference Figure 1 , Figure 5 As shown, the BAW resonator provided in the embodiment of the present application adopts the above-mentioned preparation method, and the BAW resonator includes a substrate 100 and a bottom electrode layer 101, a piezoelectric layer 102, an upper electrode layer 103 and a passivation layer 104 stacked in sequence on the substrate 100; the overlapping portion of the bottom electrode layer 101, the piezoelectric layer 102 and the upper electrode layer 103 projected on the substrate 100 is an active area; a protective layer 105 is formed on the surface of the passivation layer 104 on one side away from the substrate 100, and a groove 106 is formed on the protective layer 105, and the groove 106 is located at the edge of the active area.

[0083] Reference Figure 3 As shown, a seed layer 116 is disposed on the substrate 100 , and a specific material of the seed layer 116 may be aluminum nitride or scandium aluminum nitride. A bottom electrode layer 101 and a piezoelectric layer 102 are disposed on the seed layer 116 .

[0084] It should be noted that the passivation layer 104 in the embodiment of the present application is used to thin the resonator so that the frequency of the resonator reaches the target frequency.

[0085] The substrate 100 of the embodiment of the present application includes a first substrate 100 , a middle insulating layer and a second substrate 100 which are stacked.

[0086] The BAW resonator provided in the embodiment of the present application can effectively avoid the generation of sub-resonance at the upper electrode layer 103 by forming a groove 106 on the atomically deposited protective layer 105, which is beneficial to improving the performance of the device. In addition, the protective layer 105 in the embodiment of the present application can reliably protect the BAW resonator, effectively prevent water vapor from interfering with the device, and improve the service life of the device.

[0087] As an optional implementation, a cavity 112 is formed on the substrate 100 , and a protective layer 105 is formed on the inner wall of the cavity 112 .

[0088] It should be noted that, in the embodiment of the present application, a protective layer 105 is also provided on the inner wall of the cavity 112 , which can further prevent water vapor from causing adverse effects on the lower electrode, and is beneficial to enhancing the reliability and service life of the resonator.

[0089] As an optional implementation, a release channel 113 communicating with the cavity 112 is formed on the BAW resonator; and a protective layer 105 is formed on the inner wall of the release channel 113 .

[0090] Furthermore, in the embodiment of the present application, a protective layer 105 is formed in the release channel 113 , which can protect the release channel 113 on the piezoelectric layer 102 , the bottom electrode layer 101 , and the top electrode layer.

[0091] Reference Figure 6As shown, the filter provided in the embodiment of the present application includes the above-mentioned BAW resonator and an input port 114 and an output port 115 electrically connected to the BAW resonator. There are multiple BAW resonators, and the multiple BAW resonators are connected in series and parallel.

[0092] The embodiment of the present application adopts the above-mentioned bulk acoustic wave resonator, which can reduce the influence of sub-resonance and effectively improve the performance of the filter.

[0093] 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 method for preparing a bulk acoustic wave resonator, characterized in that: include: Providing a substrate (100); A bottom electrode layer (101), a piezoelectric layer (102), an upper electrode layer (103) and a passivation layer (104) are sequentially stacked on the surface of the substrate (100); wherein the overlapping portion of the bottom electrode layer (101), the piezoelectric layer (102) and the upper electrode layer (103) projected on the substrate (100) is an active area; forming a protective layer (105) on the surface of the passivation layer (104) by using an atomic deposition process; A groove (106) is formed on the protection layer (105), and the groove (106) is located at the edge of the active area.

2. The method for preparing a bulk acoustic wave resonator according to claim 1, characterized in that: The bottom electrode layer (101), the piezoelectric layer (102), the top electrode layer (103) and the passivation layer (104) are sequentially stacked on the surface of the substrate (100), comprising: Etching a through hole (107) on the piezoelectric layer (102); A first hollow portion (108) and a second hollow portion (109) are formed in the passivation layer (104); wherein the through hole (107) is connected to the first hollow portion (108) to form a lead channel, and the projection of the lead channel is located on the bottom electrode layer (101); and the projection of the second hollow portion (109) is located on the top electrode layer (103); A first electrode (110) is formed in the first hollow portion (108), wherein the first electrode (110) is used to connect to the bottom electrode layer (101); A second electrode (111) is formed in the second hollow portion (109), and the second electrode (111) is used to be connected to the upper electrode layer (103).

3. The method for preparing a bulk acoustic wave resonator according to claim 2, characterized in that: The method of forming a protective layer (105) on a surface of the passivation layer (104) facing away from the substrate (100) by using an atomic deposition process comprises: The protective layer (105) is patterned so that the first electrode (110) and the second electrode (111) are exposed.

4. The method for preparing a bulk acoustic wave resonator according to claim 1, characterized in that: The substrate (100) has a cavity (112); The method of forming a protective layer (105) on a surface of the passivation layer (104) facing away from the substrate (100) by using an atomic deposition process further comprises: The protective layer (105) is formed on the inner wall of the cavity (112).

5. The method for preparing a bulk acoustic wave resonator according to claim 4, characterized in that: Before forming a protective layer (105) on a surface of the passivation layer (104) facing away from the substrate (100) by using an atomic deposition process, the method comprises: A release channel (113) is formed on the bottom electrode layer (101), the piezoelectric layer (102), the top electrode layer (103) and the passivation layer (104), wherein the release channel (113) is connected to the cavity (112); The method of forming a protective layer (105) on a surface of the passivation layer (104) facing away from the substrate (100) by using an atomic deposition process further comprises: The protective layer (105) is formed on the inner wall of the release channel (113).

6. A bulk acoustic wave resonator, characterized in that: The preparation method according to any one of claims 1 to 5 is adopted, wherein the bulk acoustic wave resonator comprises a substrate (100) and a bottom electrode layer (101), a piezoelectric layer (102), an upper electrode layer (103) and a passivation layer (104) which are sequentially stacked on the substrate (100); the overlapping portion of the bottom electrode layer (101), the piezoelectric layer (102) and the upper electrode layer (103) projected on the substrate (100) is an active area; a protective layer (105) is formed on a surface of the passivation layer (104) facing away from the substrate (100), a groove (106) is formed on the protective layer (105), and the groove (106) is located at the edge of the active area.

7. The BAW resonator according to claim 6, characterized in that: A cavity (112) is formed on the substrate (100), and the protective layer (105) is formed on the inner wall of the cavity (112).

8. The bulk acoustic wave resonator according to claim 7, characterized in that: A release channel (113) communicating with the cavity (112) is formed on the BAW resonator; the protective layer (105) is formed on the inner wall of the release channel (113).

9. The BAW resonator according to claim 7, characterized in that: The substrate (100) comprises a first substrate (100), a middle insulating layer and a second substrate (100) which are stacked.

10. A filter, characterized in that: The invention comprises the BAW resonator according to any one of claims 6 to 9, and an input port (114) and an output port (115) electrically connected to the BAW resonator, wherein there are a plurality of BAW resonators, and the plurality of BAW resonators are connected in series and / or in parallel.

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