Film bulk acoustic wave filter and preparation method thereof

Abstract

The invention discloses a film bulk acoustic wave filter and a preparation method thereof. The film bulk acoustic wave filter comprises a bonding structure and at least one resonator, the resonator comprises a substrate and a transducer stacking structure which are arranged in a stacked mode. The transducer stacking structure comprises a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially stacked; in a non-resonance area of the transducer stacking structure, the piezoelectric layer comprises a first groove, the first groove penetrates through the piezoelectric layer, and the top electrode layer covers the first groove to form a bonding interface; the bonding structure is fixedly connected with the resonator through bonding glue on a bonding interface; in the thickness direction of the resonator, the projection of the bonding structure on the plane where the substrate is located covers the projection of the resonator on the plane where the substrate is located. According to the technical scheme, the first groove is formed in the piezoelectric layer, so that the top electrode layer covers the first groove to form a non-planar bonding interface, the bonding glue contact area is increased, and the bonding strength and the packaging airtightness of the bulk acoustic wave film resonator are improved.

Description

Technical Field

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

[0002] Wafer-level packaging significantly reduces the footprint of filters, freeing up valuable internal space for devices or allowing for the integration of more functions, aligning with the trend towards thinner and smaller electronic products. However, wafer-level packaging also faces the challenge of hermetic sealing. Summary of the Invention

[0003] This invention provides a thin-film bulk acoustic wave filter and its fabrication method to solve the problem of poor airtightness of filter packaging in the prior art.

[0004] According to one aspect of the present invention, a thin-film bulk acoustic wave filter is provided, comprising: a bonding structure and at least one resonator;

[0005] The resonator comprises a stacked substrate and a transducer stack structure;

[0006] The transducer stack structure includes a bottom electrode layer, a piezoelectric layer and a top electrode layer stacked sequentially; in the non-resonant region of the transducer stack structure, the piezoelectric layer includes a first groove, the first groove penetrates the piezoelectric layer, and the top electrode layer covers the first groove to form a bonding interface.

[0007] The bonding structure is fixedly connected to the resonator at the bonding interface by bonding adhesive;

[0008] Along the thickness direction of the resonator, the projection of the bonding structure onto the plane of the substrate covers the projection of the resonator onto the plane of the substrate.

[0009] Optionally, the bonding interface includes a first bonding surface and a second bonding surface;

[0010] The top electrode layer of the first bonding surface is disposed in the first groove, and the top electrode layer of the second bonding surface is disposed on the side of the piezoelectric layer away from the bottom electrode layer.

[0011] The second bonding surface is arranged around the first bonding surface and along the thickness direction of the resonator. The projection of the first bonding surface onto the plane of the substrate is connected to the projection of the second bonding surface onto the plane of the substrate.

[0012] Optionally, the bottom electrode layer includes a first bottom electrode region and a second bottom electrode region that are not connected to each other; a portion of the first bottom electrode region is located in the resonant region; and the second bottom electrode region is located in the non-resonant region.

[0013] In the non-resonant region, the piezoelectric layer also includes a second groove and a third groove that penetrate through it; the top electrode layer covers the second groove to connect with the second bottom electrode region; the top electrode layer on the second groove is connected to the top electrode layer in the resonant region;

[0014] The top electrode layer covers the third groove to connect with the first bottom electrode region;

[0015] The substrate includes vias that penetrate the substrate; the side of the substrate away from the transducer stack structure includes a redistribution layer; the redistribution layer is connected to the first bottom electrode region and the second bottom electrode region through vias.

[0016] Optionally, a metal layer may also be included;

[0017] The metal layer is disposed on the side of the top electrode layer covering the first groove, the side of the top electrode layer covering the second groove, and the side of the top electrode layer covering the third groove.

[0018] Optionally, the redistribution layer on the side away from the substrate includes a solder mask layer;

[0019] Solder balls are placed on the solder mask layer; the solder balls are connected to the redistribution layer.

[0020] According to another aspect of the present invention, a method for fabricating a thin-film bulk acoustic filter is provided, for fabricating the thin-film bulk acoustic filter;

[0021] Preparation methods include:

[0022] A substrate is obtained, and a bottom electrode layer and a piezoelectric layer are sequentially fabricated on the substrate;

[0023] The piezoelectric layer is etched to form a first groove on the piezoelectric layer; wherein the first groove is located in the non-resonant region of the transducer stack structure and penetrates the piezoelectric layer;

[0024] A top electrode layer is prepared on the side of the piezoelectric layer away from the bottom electrode layer and the top electrode layer is patterned so that the top electrode layer covers the first groove to form a bonding interface;

[0025] A bonding structure is obtained and bonded to the resonator at the bonding interface using bonding adhesive; wherein, along the thickness direction of the resonator, the projection of the bonding structure onto the plane of the substrate covers the projection of the resonator onto the plane of the substrate.

[0026] Optionally, the top electrode layer is patterned, including:

[0027] A patterned top electrode layer is formed to form a first bonding surface and a second bonding surface; wherein, the top electrode layer of the first bonding surface is disposed in a first groove, and the top electrode layer of the second bonding surface is disposed on the side of the piezoelectric layer away from the bottom electrode layer; the second bonding surface is disposed around the first bonding surface and along the thickness direction of the resonator, and the projection of the first bonding surface on the plane of the substrate is connected to the projection of the second bonding surface on the plane of the substrate.

[0028] Optionally, the bottom electrode layer includes a first bottom electrode region and a second bottom electrode region that are not connected to each other; a portion of the first bottom electrode region is located in the resonant region; and the second bottom electrode region is located in the non-resonant region.

[0029] Etching the piezoelectric layer to form a first groove on the piezoelectric layer includes:

[0030] The piezoelectric layer is etched to form a first groove, a second groove, and a third groove on the piezoelectric layer; wherein the second groove and the third groove penetrate the piezoelectric layer;

[0031] Patterning the top electrode layer includes:

[0032] The top electrode layer is patterned so that the top electrode layer covers the second groove and connects with the second bottom electrode region, the top electrode layer on the second groove is connected with the top electrode layer of the resonant region, and the top electrode layer covers the third groove to connect with the first bottom electrode region.

[0033] After obtaining the bonding structure and bonding the bonding structure to the resonator at the bonding interface using bonding glue, the process also includes:

[0034] The substrate is etched to form a via in the substrate; wherein the via penetrates the substrate;

[0035] A redistribution layer is prepared on the side of the substrate away from the transducer stack structure; wherein the redistribution layer is connected to the first bottom electrode region and the second bottom electrode region through vias.

[0036] Optionally, before obtaining the bonding structure and bonding the bonding structure to the resonator at the bonding interface using bonding glue, the method further includes:

[0037] A metal layer is fabricated on the side of the top electrode layer away from the piezoelectric layer;

[0038] The metal layer is peeled off so that the metal layer covers one side of the top electrode layer of the first groove, one side of the top electrode layer of the second groove, and one side of the top electrode layer of the third groove.

[0039] Optionally, after fabricating the redistribution layer on the side of the substrate away from the transducer stack structure, the method further includes:

[0040] A solder resist layer is prepared on the side of the redistribution layer away from the substrate;

[0041] Solder balls are prepared on the solder mask layer; wherein the solder balls are connected to the redistribution layer.

[0042] The technical solution of the present invention increases the bonding adhesive contact area by setting a first groove in the piezoelectric layer, so that the top electrode layer covers the first groove to form a non-planar bonding interface, thereby improving the bonding strength and encapsulation airtightness of the bulk acoustic wave thin film resonator.

[0043] 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

[0044] 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.

[0045] Figure 1 This is a schematic diagram of the structure of a thin-film bulk acoustic filter according to an embodiment of the present invention;

[0046] Figure 2 This is a flowchart of a method for fabricating a first type of thin-film bulk acoustic filter according to an embodiment of the present invention;

[0047] Figure 3 This is a structural diagram corresponding to the fabrication method of the first thin-film bulk acoustic filter provided in the embodiments of the present invention;

[0048] Figure 4 This is a flowchart of a method for fabricating a second type of thin-film bulk acoustic filter according to an embodiment of the present invention;

[0049] Figure 5 This is a structural diagram corresponding to the fabrication method of the second thin-film bulk acoustic filter provided in the embodiments of the present invention;

[0050] Figure 6 This is a flowchart of a third method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention;

[0051] Figure 7 This is a structural diagram corresponding to the fabrication method of the third thin-film bulk acoustic filter provided in the embodiments of the present invention;

[0052] Figure 8 This is a flowchart of a fourth method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention;

[0053] Figure 9This is a structural diagram corresponding to the fabrication method of the fourth thin-film bulk acoustic filter provided in the embodiments of the present invention;

[0054] Figure 10 This is a flowchart of a fifth method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention;

[0055] Figure 11 This is a structural diagram corresponding to the fifth method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] Figure 1 This is a schematic diagram of the structure of a thin-film bulk acoustic filter according to an embodiment of the present invention. Figure 1 As shown, the thin-film bulk acoustic wave filter includes:

[0059] Bonding structure 110 and at least one resonator;

[0060] The resonator includes a substrate 101 and a transducer stack structure arranged in layers;

[0061] The transducer stack structure includes a bottom electrode layer 105, a piezoelectric layer 106 and a top electrode layer 107 stacked sequentially; in the non-resonant region of the transducer stack structure, the piezoelectric layer 106 includes a first groove 1161, the first groove 1161 penetrates the piezoelectric layer 106, and the top electrode layer 107 covers the first groove 1161 to form a bonding interface.

[0062] The bonding structure 110 is fixedly connected to the resonator at the bonding interface by bonding adhesive 111;

[0063] Along the thickness direction y of the resonator, the projection of the bonding structure 110 onto the plane of the substrate 101 covers the projection of the resonator onto the plane of the substrate 101.

[0064] The thin-film bulk acoustic wave filter includes one or more resonators. Each resonator comprises a substrate 101 and a transducer stack structure stacked on top of each other. The transducer stack structure includes a bottom electrode layer 105, a piezoelectric layer 106, and a top electrode layer 107 sequentially stacked on the substrate 101. In some embodiments, the substrate 101 includes a cavity 102. The overlapping region of the cavity 102, the bottom electrode layer 105, the piezoelectric layer 106, and the top electrode layer 107 is a resonant region, while other regions are non-resonant regions. The resonant region converts electrical energy into sound waves through the inverse piezoelectric effect to form resonance. A first groove 1161 penetrating the piezoelectric layer 106 is included in the non-resonant region. The top electrode layer 107 covers both the resonant region and the first groove 1161 in the non-resonant region. The bonding interface can be the bonding plane of the bonding structure 110 and the resonator. Since the thickness of the top electrode layer 107 is thinner than that of the piezoelectric layer 106, there is still a certain height difference between the top electrode layer 107 and the surface of the piezoelectric layer 106 after the top electrode layer 107 covers the first groove 1161. Therefore, the bonding interface is non-planar.

[0065] The bonding structure 110 can be a silicon cap. The bonding adhesive 111 can be placed on the bonding interface, and the silicon cap can be bonded to the resonator through the bonding adhesive 111. Along the thickness direction y of the resonator, the projection of the bonding structure 110 on the plane where the substrate 101 is located covers the projection of the resonator on the plane where the substrate 101 is located, thereby making the resonator and the bonding structure 110 bonded to form a sealed thin-film bulk acoustic wave filter.

[0066] It is understandable that by setting the first groove 1161 in the piezoelectric layer 106, the bonding interface is made into a non-planar structure, which can increase the contact area of ​​the bonding adhesive 111, thereby improving the bonding strength of the bonding structure 110 with the resonator and the hermeticity of the encapsulation.

[0067] For example, during fabrication, a substrate 101 is first provided, and a bottom electrode layer 105 and a piezoelectric layer 106 are sequentially fabricated on the substrate 101; the piezoelectric layer 106 is etched to form a first groove 1161 on the piezoelectric layer 106; a top electrode layer 107 is fabricated on the side of the piezoelectric layer 106 away from the bottom electrode layer 105 and the top electrode layer 107 is patterned so that the top electrode layer 107 covers the first groove 1161 to form a bonding interface; a bonding adhesive 111 is coated on the bonding interface, and the bonding structure 110 is bonded to the resonator at the bonding interface through the bonding adhesive 111.

[0068] The technical solution of this invention provides a first groove in the piezoelectric layer, which allows the top electrode layer to cover the first groove to form a non-planar bonding interface. This increases the contact area of ​​the bonding adhesive and improves the bonding strength and hermeticity of the bulk acoustic wave thin film resonator.

[0069] Optional, continue to refer to Figure 1 As shown, the bonding interface includes a first bonding surface and a second bonding surface;

[0070] The top electrode layer 107 of the first bonding surface is disposed in the first groove 1161, and the top electrode layer 107 of the second bonding surface is disposed on the side of the piezoelectric layer 106 away from the bottom electrode layer 105.

[0071] The second bonding surface is arranged around the first bonding surface and along the thickness direction y of the resonator. The projection of the first bonding surface onto the plane of the substrate 101 is connected to the projection of the second bonding surface onto the plane of the substrate 101.

[0072] In order to further improve the bonding strength, the top electrode layer 107 is provided to not only cover the first groove 1161, but also cover the surface of the piezoelectric layer 106. That is, the top electrode layer 107 of the first bonding surface is provided in the first groove 1161, and the top electrode layer 107 of the second bonding surface is provided on the side of the piezoelectric layer 106 away from the bottom electrode layer 105. During the fabrication process, the top electrode layer 107 can be etched to retain only the first bonding surface and the second bonding surface in the non-resonant region.

[0073] Specifically, during the fabrication process, the top electrode layer 107 completely covers the piezoelectric layer 106 and the first groove 1161. The patterned electrode layer disconnects the top electrode layer 107 in the resonant region from the non-resonant region, exposing the top electrode layer 107 in the first groove 1161 and a portion of the top electrode layer 107 on the piezoelectric layer 106 surrounding the first groove 1161. This allows the second bonding surface to be arranged around the first bonding surface, and the projection of the first bonding surface onto the plane of the substrate 101 is connected to the projection of the second bonding surface onto the plane of the substrate 101.

[0074] Understandably, setting the bonding interface to include a first bonding surface and a second bonding surface increases the unevenness of the bonding interface, thereby further improving the bonding strength and the hermeticity of the package.

[0075] Optional, continue to refer to Figure 1 As shown, the bottom electrode layer 105 includes a first bottom electrode region 1051 and a second bottom electrode region 1052 that are not connected to each other; a portion of the first bottom electrode region 1051 is located in the resonant region; and the second bottom electrode region 1052 is located in the non-resonant region.

[0076] In the non-resonant region, the piezoelectric layer 106 also includes a through second groove 1162 and a third groove 1163; the top electrode layer 107 covers the second groove 1162 to connect with the second bottom electrode region 1052; the top electrode layer 107 on the second groove 1162 is connected to the top electrode layer 107 of the resonant region.

[0077] The top electrode layer 107 covers the third groove 1163 to connect with the first bottom electrode region 1051;

[0078] The substrate 101 includes a via that extends through the substrate 101; the side of the substrate 101 away from the transducer stack structure includes a redistribution layer 113; the redistribution layer 113 is connected to the first bottom electrode region 1051 and the second bottom electrode region 1052 through the via.

[0079] The first bottom electrode region 1051 can be used as the bottom electrode in the resonant region, so the first bottom electrode region 1051 is partially located in the resonant region; the second bottom electrode region 1052 can be used to connect with the top electrode layer 107, so the first bottom electrode region 1051 and the second bottom electrode region 1052 are not connected to each other and the second bottom electrode region 1052 is located in the non-resonant region.

[0080] Specifically, a second groove 1162 and a third groove 1163 are provided on the piezoelectric layer 106. The second groove 1162 penetrates the piezoelectric layer 106 to expose the second bottom electrode region 1052, and the third groove 1163 penetrates the piezoelectric layer 106 to expose the first bottom electrode region 1051. Thus, after the top electrode layer 107 is prepared, the top electrode layer 107 covers the second groove 1162 and is electrically connected to the second bottom electrode region 1052, and the top electrode layer 107 covers the third groove 1163 and is electrically connected to the first bottom electrode region 1051.

[0081] Since the second bottom electrode region 1052 can be used to connect with the top electrode layer 107, the top electrode layer 107 located in the second groove 1162 is electrically connected to the top electrode layer 107 in the resonant region.

[0082] It is understandable that by providing the second groove 1162 and the third groove 1163 in the piezoelectric layer 106, the top electrode layer 107 and the bottom electrode layer 105 of the working area can be led out after the top electrode layer 107 is prepared, thereby facilitating the connection between the resonator and the external traces.

[0083] Specifically, vias are etched in the substrate 101, and the positions of the vias correspond to the positions of the second groove 1162 and the third groove 1163. A redistribution layer 113 is prepared on the side of the substrate 101 away from the transducer stack structure, such that the redistribution layer 113 fills the vias, thereby bringing out the top electrode layer 107 and the bottom electrode layer 105 of the working region.

[0084] The technical solution of this invention ensures the normal operation of the thin-film bulk acoustic wave filter by setting vias in the substrate and setting a redistribution layer so that the top electrode layer and bottom electrode layer of the working area are led out through the redistribution layer. At the same time, by setting vias on the substrate side, the integrity of the bonding structure is not damaged, further ensuring the packaging quality. The setting of the redistribution layer can greatly improve the heat dissipation path, form an efficient vertical heat dissipation channel, and improve the heat dissipation efficiency of the thin-film bulk acoustic wave filter.

[0085] Optional, continue to refer to Figure 1 As shown, it also includes a metal layer 108;

[0086] Metal layer 108 is disposed on one side of the top electrode layer 107 covering the first groove 1161, one side of the top electrode layer 107 covering the second groove 1162, and one side of the top electrode layer 107 covering the third groove 1163.

[0087] Since the electrode layer in the resonator is relatively thin, in order to ensure the lead-out of the electrode layer, after the top electrode layer 107 is prepared, a metal layer 108 is prepared so that the metal layer 108 covers the top electrode layer 107 in the first groove 1161, the top electrode layer 107 in the second groove 1162, and the top electrode layer 107 in the third groove 1163.

[0088] Optional, continue to refer to Figure 1 As shown, the redistribution layer 113 includes a solder mask layer 114 on the side away from the substrate 101;

[0089] Solder balls 115 are disposed on the solder mask layer 114; the solder balls 115 are connected to the redistribution layer 113.

[0090] In order to improve the insulation and sealing of the filter, a solder mask layer 114 is provided on the side of the redistribution layer 113 away from the substrate 101, and solder balls 115 are provided on the solder mask layer 114 to connect with the redistribution layer 113, thereby leading out the bottom electrode layer 105 and the top electrode layer 107.

[0091] The thin-film bulk acoustic wave filter in this embodiment of the invention increases the contact area of ​​the bonding adhesive by setting a first groove in the piezoelectric layer, thereby improving the bonding strength and the hermeticity of the packaging; it ensures the integrity of the bonding structure by opening a through-hole on the wafer side of the device, thereby further improving the packaging quality; and it greatly shortens the heat dissipation path by setting a redistribution layer in the through-hole, thereby forming an efficient vertical heat dissipation channel.

[0092] Based on the same inventive concept. Figure 2 This is a flowchart of a method for fabricating a first type of thin-film bulk acoustic filter according to an embodiment of the present invention. Figure 3 This is a structural diagram corresponding to the fabrication method of the first thin-film bulk acoustic filter provided in the embodiments of the present invention, combined with... Figure 2 and Figure 3 As shown, this embodiment of the invention provides a method for fabricating a thin-film bulk acoustic wave filter. The fabrication method for the thin-film bulk acoustic wave filter includes:

[0093] S10. Obtain the substrate and sequentially fabricate the bottom electrode layer and the piezoelectric layer on the substrate. For example... Figure 3 As shown in step (a).

[0094] A cavity 102 can be provided in the substrate 101. First, the cavity 102 is formed by etching on the substrate 101. Then, a sacrificial layer 103 is deposited on the substrate 101 and planarized by chemical mechanical polishing so that the sacrificial layer 103 only fills the cavity 102.

[0095] A bottom electrode layer 105 is fabricated and patterned on one side of the substrate 101, and a piezoelectric layer 106 is deposited on one side of the bottom electrode layer 105.

[0096] In some embodiments, in order to improve the deposition quality of the piezoelectric layer 106, a seed layer 104 is deposited before the bottom electrode layer 105 is prepared.

[0097] S11. Etch the piezoelectric layer to form a first groove on the piezoelectric layer. The first groove 1161 is located in the non-resonant region of the transducer stack structure and penetrates the piezoelectric layer 106. Figure 3 As shown in step (b).

[0098] Specifically, the piezoelectric layer 106 is etched in the non-resonant region to form a first groove 1161, which exposes the bottom electrode layer 105.

[0099] S12. A top electrode layer is prepared on the side of the piezoelectric layer away from the bottom electrode layer, and the top electrode layer is patterned so that the top electrode layer covers the first groove to form a bonding interface. For example... Figure 3 As shown in step (c).

[0100] After depositing the top electrode layer 107, the top electrode layer 107 is patterned, and the top electrode layer 107 in the first groove 1161 is retained.

[0101] S13. Obtain the bonding structure and bond the bonding structure to the resonator at the bonding interface using bonding adhesive. Wherein, along the thickness direction y of the resonator, the projection of the bonding structure 110 onto the plane of the substrate 101 overlaps the projection of the resonator onto the plane of the substrate 101. For example... Figure 3 As shown in step (d).

[0102] The bonding structure 110 can be a silicon cap. Before bonding the bonding structure 110, a groove structure can be etched on the silicon wafer to form a silicon cap, and then the bonding structure 110 can be bonded to the resonator at the bonding interface using bonding adhesive 111.

[0103] It is understandable that by setting the first groove 1161 in the piezoelectric layer 106, the bonding interface is made into a non-planar structure, which can increase the contact area of ​​the bonding adhesive 111, thereby improving the bonding strength of the bonding structure 110 with the resonator and the hermeticity of the encapsulation.

[0104] For example, during fabrication, a substrate 101 is first provided, and a bottom electrode layer 105 and a piezoelectric layer 106 are sequentially fabricated on the substrate 101; the piezoelectric layer 106 is etched to form a first groove 1161 on the piezoelectric layer 106; a top electrode layer 107 is fabricated on the side of the piezoelectric layer 106 away from the bottom electrode layer 105 and the top electrode layer 107 is patterned so that the top electrode layer 107 covers the first groove 1161 to form a bonding interface; a bonding adhesive 111 is coated on the bonding interface, and the bonding structure 110 is bonded to the resonator at the bonding interface through the bonding adhesive 111.

[0105] The technical solution of this invention forms a bonding interface while fabricating the resonator, without the need for an additional photomask. Due to the unevenness of the bonding interface, the contact area of ​​the bonding adhesive is increased, thereby improving the bonding strength and hermeticity of the bulk acoustic wave thin film resonator.

[0106] Based on the above embodiments, Figure 4 This is a flowchart of a second method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention. Figure 5 This is a structural diagram corresponding to the fabrication method of the second thin-film bulk acoustic filter provided in the embodiments of the present invention, combined with... Figure 4 and Figure 5 As shown, the preparation method includes:

[0107] S20. Obtain the substrate and sequentially fabricate the bottom electrode layer and the piezoelectric layer on the substrate. For example... Figure 5 As shown in step (e).

[0108] S21. Etch the piezoelectric layer to form a first groove on the piezoelectric layer. For example... Figure 5 As shown in step (f).

[0109] S22. A top electrode layer is fabricated and patterned on the side of the piezoelectric layer away from the bottom electrode layer to form a first bonding surface and a second bonding surface. The top electrode layer 107 of the first bonding surface is disposed in the first groove 1161, and the top electrode layer 107 of the second bonding surface is disposed on the side of the piezoelectric layer 106 away from the bottom electrode layer 105. The second bonding surface surrounds the first bonding surface and is disposed along the resonator thickness direction y. The projection of the first bonding surface onto the plane of the substrate 101 is connected to the projection of the second bonding surface onto the plane of the substrate 101. Figure 5 As shown in step (g).

[0110] In this process, a top electrode layer 107 is deposited on the surface of the piezoelectric layer 106, completely covering the piezoelectric layer 106 and the first groove 1161. The patterned electrode layer disconnects the top electrode layer 107 in the resonant region from the non-resonant region, exposing the top electrode layer 107 in the first groove 1161 and a portion of the top electrode layer 107 on the piezoelectric layer 106 surrounding the first groove 1161. This allows the second bonding surface to be disposed around the first bonding surface, and the projection of the first bonding surface onto the plane of the substrate 101 is connected to the projection of the second bonding surface onto the plane of the substrate 101.

[0111] S23. Obtain the bonding structure and bond the bonding structure to the resonator at the bonding interface using bonding adhesive. For example... Figure 5 The (h) step is shown.

[0112] The technical solution of this invention increases the unevenness of the bonding interface by preparing a first bonding surface and a second bonding surface, thereby further improving the bonding strength and the hermeticity of the encapsulation.

[0113] Based on the above embodiments, Figure 6 This is a flowchart of a third method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention. Figure 7 This is a structural diagram corresponding to the fabrication method of the third thin-film bulk acoustic filter provided in the embodiments of the present invention, combined with... Figure 6 and Figure 7 As shown, the bottom electrode layer 105 includes a first bottom electrode region 1051 and a second bottom electrode region 1052 that are not connected to each other; a portion of the first bottom electrode region 1051 is located in the resonant region; and the second bottom electrode region 1052 is located in the non-resonant region. The fabrication method includes:

[0114] S30. Obtain the substrate and sequentially fabricate the bottom electrode layer and the piezoelectric layer on the substrate. For example... Figure 7 As shown in step (i).

[0115] S31. Etch the piezoelectric layer to form a first groove, a second groove, and a third groove on the piezoelectric layer. The second groove 1162 and the third groove 1163 penetrate the piezoelectric layer 106. Figure 7 The (j) step is shown.

[0116] The purpose of etching the second groove 1162 and the third groove 1163 is to bring out the bottom electrode layer 105 and the top electrode layer 107. After the piezoelectric layer 106 is fabricated, the first groove 1161, the second groove 1162 and the third groove 1163 are etched simultaneously, such that the second groove 1162 penetrates the piezoelectric layer 106 to expose the second bottom electrode region 1052, and the third groove 1163 penetrates the piezoelectric layer 106 to expose the first bottom electrode region 1051.

[0117] S32. A top electrode layer is prepared on the side of the piezoelectric layer away from the bottom electrode layer and patterned so that the top electrode layer covers the first groove to form a bonding interface, so that the top electrode layer covers the second groove and connects with the second bottom electrode region, the top electrode layer on the second groove connects with the top electrode layer of the resonant region, and the top electrode layer covers the third groove to connect with the first bottom electrode region. Figure 7 The (k) step is shown.

[0118] Specifically, a top electrode layer 107 is prepared after etching the first groove 1161, the second groove 1162, and the third groove 1163. This top electrode layer 107 covers the first groove 1161, the second groove 1162, and the third groove 1163, connecting with the first bottom electrode region 1051 and the second bottom electrode region 1052. By patterning the top electrode layer 107, a bonding interface is formed, connecting the resonant region and a non-resonant region connecting the first bottom electrode region 1051.

[0119] S33. Obtain the bonding structure and bond the bonding structure to the resonator at the bonding interface using bonding glue. For example... Figure 7 The (l) step is shown.

[0120] S34. Etch the substrate to form a through-hole in the substrate. The through-hole penetrates the substrate. For example... Figure 7 The (m) step is shown.

[0121] The substrate 101 can be thinned before etching. The positions of the vias correspond to the positions of the second groove 1162 and the third groove 1163.

[0122] S35. A redistribution layer is fabricated on the side of the substrate away from the transducer stack structure. The redistribution layer 113 is connected to the first bottom electrode region 1051 and the second bottom electrode region 1052 via vias. Figure 7 The (n) steps are shown.

[0123] The redistribution layer 113 fills through-holes, so that the redistribution layer 113 is connected to the first bottom electrode region 1051 and the second bottom electrode region 1052 through the through-holes, thereby leading out the top electrode layer 107 and the bottom electrode layer 105 of the working region.

[0124] The technical solution of this invention involves etching a first groove, a second groove, and a third groove after preparing the piezoelectric layer, thereby forming a bonding interface and leading out the bottom electrode layer and the top electrode layer during the processing of the resonator; at the same time, by setting through holes, the integrity of the bonding structure is not damaged, further ensuring the packaging quality; the preparation of the redistribution layer can greatly improve the heat dissipation path, forming an efficient vertical heat dissipation channel, and improving the heat dissipation efficiency of the thin-film bulk acoustic wave filter.

[0125] Based on the above embodiments, Figure 8 This is a flowchart of a fourth method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention. Figure 9 This is a structural diagram corresponding to the fabrication method of the fourth thin-film bulk acoustic filter provided in the embodiments of the present invention, combined with... Figure 8 and Figure 9 As shown, the preparation method includes:

[0126] S40. Obtain the substrate and sequentially fabricate the bottom electrode layer and the piezoelectric layer on the substrate. For example... Figure 9 The (o) step is shown.

[0127] S41. Etch the piezoelectric layer to form a first groove, a second groove, and a third groove on the piezoelectric layer. For example... Figure 9 The (p) step is shown.

[0128] S42. A top electrode layer is prepared on the side of the piezoelectric layer away from the bottom electrode layer and patterned so that the top electrode layer covers the first groove to form a bonding interface, so that the top electrode layer covers the second groove and connects with the second bottom electrode region, the top electrode layer on the second groove connects with the top electrode layer of the resonant region, and the top electrode layer covers the third groove to connect with the first bottom electrode region. Figure 9 The (q) step is shown.

[0129] S43. Prepare a metal layer on the side of the top electrode layer away from the piezoelectric layer. For example... Figure 9 The (r) step is shown.

[0130] S44. Peel off the metal layer so that the metal layer covers one side of the top electrode layer of the first groove, one side of the top electrode layer of the second groove, and one side of the top electrode layer of the third groove. For example... Figure 9 The (s) step is shown.

[0131] Since the electrode layer in the resonator is relatively thin, in order to ensure the lead-out of the electrode layer, after the top electrode layer 107 is prepared, the metal layer 108 is prepared. The metal layer 108 is peeled off so that the metal layer 108 covers the top electrode layer 107 in the first groove 1161, the top electrode layer 107 in the second groove 1162, and the top electrode layer 107 in the third groove 1163.

[0132] In addition, after stripping the metal layer 108, a release hole 109 can be etched on the resonator to release the sacrificial layer in the cavity 102.

[0133] S45. Obtain the bonding structure and bond the bonding structure to the resonator at the bonding interface using bonding adhesive. For example... Figure 9 The (t) step is shown.

[0134] S46. Etch the substrate to form vias in the substrate. For example... Figure 9 The (u) step is shown.

[0135] S47. Fabricate a redistribution layer on the side of the substrate away from the transducer stack structure. For example... Figure 9 The (v) step is shown.

[0136] Based on the above embodiments, Figure 10 This is a flowchart of the fifth method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention. Figure 11 This is a structural diagram corresponding to the fifth method for fabricating a thin-film bulk acoustic filter according to an embodiment of the present invention, combined with... Figure 10 and Figure 11 As shown, the preparation method includes:

[0137] S50. Obtain the substrate and sequentially fabricate the bottom electrode layer and piezoelectric layer on the substrate. For example... Figure 11 The (w) step is shown.

[0138] S51, Etch the piezoelectric layer to form a first groove, a second groove, and a third groove on the piezoelectric layer. For example... Figure 11 The (x) step is shown.

[0139] S52. A top electrode layer is prepared on the side of the piezoelectric layer away from the bottom electrode layer and patterned so that the top electrode layer covers the first groove to form a bonding interface, so that the top electrode layer covers the second groove and connects with the second bottom electrode region, the top electrode layer on the second groove connects with the top electrode layer of the resonant region, and the top electrode layer covers the third groove to connect with the first bottom electrode region. Figure 11 The (y) step is shown.

[0140] S53. Obtain the bonding structure and bond the bonding structure to the resonator at the bonding interface using bonding adhesive. For example... Figure 11 The (z1) step is shown.

[0141] S54. Etch the substrate to form vias in the substrate. For example... Figure 11 The (z2) step is shown.

[0142] S55. Fabricate a redistribution layer on the side of the substrate away from the transducer stack structure. For example... Figure 11 The (z3) step is shown.

[0143] S56. Prepare a solder resist layer on the side of the redistribution layer away from the substrate. For example... Figure 11 The (z4) step is shown.

[0144] S57. Solder balls are prepared on the solder mask layer. Solder balls 115 are connected to the redistribution layer 113. For example... Figure 11The (z5) step is shown.

[0145] In order to improve the insulation and sealing of the filter, a solder mask layer 114 is provided on the side of the redistribution layer 113 away from the substrate 101, and solder balls 115 are implanted on the solder mask layer 114 to achieve connection with the redistribution layer 113, and the bottom electrode layer 105 and the top electrode layer 107 are led out.

[0146] The method for fabricating a thin-film bulk acoustic wave filter provided in this invention directly forms a bonding interface during the filter fabrication process, increasing the contact area of ​​the bonding adhesive and improving bonding strength and packaging hermeticity without adding a photomask; by opening vias on the filter wafer side, the integrity of the silicon cap is ensured, further improving the packaging quality; by fabricating a redistribution layer in the vias, the heat dissipation path is greatly shortened, forming an efficient vertical heat dissipation channel.

[0147] 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.

[0148] 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 thin-film bulk acoustic wave filter, characterized in that, include: Bonded structure and at least one resonator; The resonator includes a stacked substrate and a transducer stack structure; The transducer stack structure includes a bottom electrode layer, a piezoelectric layer, and a top electrode layer stacked sequentially; in the non-resonant region of the transducer stack structure, the piezoelectric layer includes a first groove that penetrates the piezoelectric layer, and the top electrode layer covers the first groove to form a bonding interface; The bonding structure is fixedly connected to the resonator at the bonding interface by bonding adhesive; Along the thickness direction of the resonator, the projection of the bonding structure onto the plane of the substrate overlaps the projection of the resonator onto the plane of the substrate.

2. The thin-film bulk acoustic filter according to claim 1, characterized in that, The bonding interface includes a first bonding surface and a second bonding surface; The top electrode layer of the first bonding surface is disposed in the first groove, and the top electrode layer of the second bonding surface is disposed on the side of the piezoelectric layer away from the bottom electrode layer; The second bonding surface is disposed around the first bonding surface and along the thickness direction of the resonator, and the projection of the first bonding surface on the plane of the substrate is connected to the projection of the second bonding surface on the plane of the substrate.

3. The thin-film bulk acoustic filter according to claim 1, characterized in that, The bottom electrode layer includes a first bottom electrode region and a second bottom electrode region that are not connected to each other; a portion of the first bottom electrode region is located in the resonant region; the second bottom electrode region is located in the non-resonant region. In the non-resonant region, the piezoelectric layer further includes a second groove and a third groove that penetrate through it; the top electrode layer covers the second groove to connect with the second bottom electrode region; the top electrode layer on the second groove is connected to the top electrode layer in the resonant region; The top electrode layer covers the third groove to connect with the first bottom electrode region; The substrate includes a via that penetrates the substrate; the side of the substrate away from the transducer stack structure includes a redistribution layer; the redistribution layer is connected to the first bottom electrode region and the second bottom electrode region respectively through the via.

4. The thin-film bulk acoustic filter according to claim 3, characterized in that, It also includes a metal layer; The metal layer is disposed on one side of the top electrode layer covering the first groove, one side of the top electrode layer covering the second groove, and one side of the top electrode layer covering the third groove.

5. The thin-film bulk acoustic filter according to claim 3, characterized in that, The redistribution layer on the side away from the substrate includes a solder mask layer; Solder balls are disposed on the solder mask layer; the solder balls are connected to the redistribution layer.

6. A method for fabricating a thin-film bulk acoustic wave filter, characterized in that, Used to prepare the thin-film bulk acoustic filter according to any one of claims 1-5; The preparation method includes: A substrate is obtained, and a bottom electrode layer and a piezoelectric layer are sequentially fabricated on the substrate; The piezoelectric layer is etched to form a first groove on the piezoelectric layer; wherein the first groove is located in the non-resonant region of the transducer stack structure and penetrates the piezoelectric layer; A top electrode layer is prepared on the side of the piezoelectric layer away from the bottom electrode layer and the top electrode layer is patterned so that the electrode layer covers the first groove to form a bonding interface; A bonding structure is obtained and the bonding structure is bonded to the resonator at the bonding interface using bonding adhesive; wherein, along the thickness direction of the resonator, the projection of the bonding structure onto the plane of the substrate covers the projection of the resonator onto the plane of the substrate.

7. The preparation method according to claim 6, characterized in that, Patterning the top electrode layer includes: The top electrode layer is patterned to form a first bonding surface and a second bonding surface; wherein the top electrode layer of the first bonding surface is disposed in the first groove, and the top electrode layer of the second bonding surface is disposed on the side of the piezoelectric layer away from the bottom electrode layer; the second bonding surface is disposed around the first bonding surface and along the thickness direction of the resonator, and the projection of the first bonding surface on the plane of the substrate is connected to the projection of the second bonding surface on the plane of the substrate.

8. The preparation method according to claim 6, characterized in that, The bottom electrode layer includes a first bottom electrode region and a second bottom electrode region that are not connected to each other; a portion of the first bottom electrode region is located in the resonant region. The second bottom electrode region is located in the non-resonant region; Etching the piezoelectric layer to form a first groove on the piezoelectric layer includes: The piezoelectric layer is etched to form a first groove, a second groove, and a third groove on the piezoelectric layer; wherein the second groove and the third groove penetrate the piezoelectric layer; Patterning the top electrode layer includes: The top electrode layer is patterned such that the top electrode layer covers the second groove and connects to the second bottom electrode region, the top electrode layer on the second groove is connected to the top electrode layer of the resonant region, and the top electrode layer covers the third groove and connects to the first bottom electrode region; After obtaining the bonding structure and bonding the bonding structure to the resonator at the bonding interface using bonding glue, the process further includes: The substrate is etched to form a through-hole in the substrate; wherein the through-hole extends through the substrate; A redistribution layer is prepared on the side of the substrate away from the transducer stack structure; wherein the redistribution layer is connected to the first bottom electrode region and the second bottom electrode region respectively through the via.

9. The preparation method according to claim 8, characterized in that, Before obtaining the bonding structure and bonding the bonding structure to the resonator at the bonding interface using bonding adhesive, the method further includes: A metal layer is prepared on the side of the top electrode layer away from the piezoelectric layer; The metal layer is peeled off so that it covers one side of the top electrode layer of the first groove, one side of the top electrode layer of the second groove, and one side of the top electrode layer of the third groove.

10. The preparation method according to claim 8, characterized in that, After fabricating the redistribution layer on the side of the substrate away from the transducer stack structure, the method further includes: A solder resist layer is prepared on the side of the redistribution layer away from the substrate; Solder balls are prepared on the solder mask layer; wherein the solder balls are connected to the redistribution layer.

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